Paper presentation: Nano-technology


NANOTECHNOLOGY - CRITICAL ENDEAVOR IN CANCER


ABSTRACT    
                          The advent of nanotechnology in cancer research couldn’t have come at a more opportune time. The vast knowledge of cancer genomics and proteomics emerging as a result of the Human Genome Project is providing critically important details of how cancer develops, which, in turn, creates new opportunities to attack the molecular underpinnings of cancer. However, scientists lack the technological innovations to turn promising molecular discoveries into benefits for cancer patients. It is here that nanotechnology can play a pivotal role, providing the technological power and tools that will enable those developing new diagnostics, therapeutics, and preventives to keep pace with today’s explosion in knowledge.
                        
                          Nanotechnology provides the sized materials that can be synthesized and function in the same general size range and Biologic structures. Attempts are made to develop forms of anticancer therapeutics based on nanomaterials. Dendritic polymer nanodevices serves as a means for the detection of cancer cells, the identification of cancer signatures, and the targeted delivery of anti-cancer therapeutics (cis-platin, methotrexate, and taxol) and contrast agents to tumor cells. Initial studies documented the synthesis and function of a targeting module, several drug delivery components, and two imaging/contrast agents. Analytical techniques have been developed and used to confirm the structure of the device. Progress has been made on the specifically triggered release of the therapeutic agent within a tumor using high-energy lasers. The work to date has demonstrated the feasibility of the nano-device concept in actual cancer cells in vitro.

2.0 INTRODUCTION
                           Nanotechnology offers the unprecedented and paradigm-changing opportunity to study and interact with normal and cancer cells in real time, at the molecular and cellular scales, and during the earliest stages of the cancer process. Through the concerted development of nanoscale devices or devices with nanoscale materials and components, the NCI Alliance for Nanotechnology in Cancer will facilitate their integration within the existing cancer research infrastructure. The Alliance will bring enabling technologies for:
•    Imaging agents and diagnostics that will allow clinicians to detect cancer  earliest stages
•    Systems that will provide real-time assessments of therapeutic and surgical efficacy for accelerating clinical translation
•    Multifunctional, targeted devices capable of bypassing biological barriers to deliver multiple therapeutic agents directly to cancer cells and those tissues in the  microenvironment that play a critical role in the growth and metastasis of cancer .
•    Agents that can monitor predictive molecular changes and prevent precancerous cells from becoming malignant
•    Novel methods to manage the symptoms of cancer that adversely impact quality of life
•    Research tools that will enable rapid identification of new targets for clinical development and predict drug resistance.

3.0 NANOTECHNOLOGY IN CANCER
             Nanoscale devices are somewhere from one hundred to ten thousand times smaller than human cells. They are similar in size to large biological molecules ("biomolecules") such as enzymes and receptors. As an example, hemoglobin, the molecule that carries oxygen in red blood cells, is approximately 5 nanometers in diameter. Nanoscale devices smaller than 50 nanometers can easily enter most cells, while those smaller than 20 nanometers can move out of blood vessels as they circulate through the body.
             Because of their small size, nanoscale devices can readily interact with biomolecules on both the surface of cells and inside of cells. By gaining access to so many areas of the body, they have the potential to detect disease and deliver treatment in ways unimagined before now. And since biological processes, including events that lead to cancer, occur at the nanoscale at and inside cells, nanotechnology offers a wealth of tools that are providing cancer researchers with new and innovative ways to diagnose and treat cancer.





4.0 NANOTECHNOLOGY AND CANCER THERAPY
                Nanoscale devices have the potential to radically change cancer therapy for the better and to dramatically increase the number of highly effective therapeutic agents. Nanoscale constructs can serve as customizable, targeted drug delivery vehicles capable of ferrying large doses of chemotherapeutic agents or therapeutic genes into malignant cells while sparing healthy cells,greatly reducing or eliminating the often unpalatable side effects that accompany many current  cancer therapies.
                 On an equally unconventional front, efforts are focused on constructing robust “smart” nanostructures that Will eventually be capable of detecting malignant cells in vivo, pinpointing their location  in the body, killing the cells, and reporting back that their payload has done its job. The operative principles driving these current efforts are modularity and multifunctionality, i.e., creating functional building blocks that can be snapped together and modified to meet the particular demands of a given clinical situation.

5.0 NANOWIRES
                In this diagram, nano sized sensing wires are laid down across a microfluidic channel. These nanowires by nature have incredible properties of selectivity and specificity. As particles flow through the microfluidic channel, the nanowire sensors pick up the molecular signatures of these particles and can immediately relay this information through a connection of electrodes to the outside world.

                These nanodevices are man-made constructs made with carbon, silicon and other materials that have the capability to monitor the complexity of biological phenomenon and relay the information, as it is monitored, to the medical care provider.
                They can detect the presence of altered genes associated with cancer and may help researchers pinpoint the exact location of those changes


 6.0 CANTILEVERS

            Nanoscale cantilevers – microscopic, flexible beams resembling a row of diving boards – are built using semiconductor lithographic techniques. These can be coated with molecules capable of binding specific substrates—DNA complementary to a specific gene sequence, for example. Such micron-sized devices, comprising many nanometer-sized cantilevers, can detect single molecules of DNA or protein.

             As a cancer cell secretes its molecular products, the antibodies coated on the cantilever fingers selectively bind to these secreted proteins. These antibodies have been designed to pick up one or more different, specific molecular expressions from a cancer cell. The physical properties of the cantilevers change as a result of the binding event. Researcherscan read this change in real time and provide not only information about the presence and the absence but also the concentration of different molecular expressions.
             Nanoscale cantilevers, constructed as part of a larger diagnostic device, can provide rapid and sensitive detection of cancer-related molecules.

7.0 NANOSHELLS
             Nanoshells have a core of silica and a metallic outer layer. These nanoshells can be injected safely, as demonstrated in animal models.Because of their size, nanoshells will preferentially concentrate in cancer lesion sites. This physical selectivity occurs through a phenomenon called enhanced permeation retention (EPR).Scientists can further decorate the nanoshells to carry molecular conjugates to the antigens that are expressed on the cancer cells themselves or in the tumor microenvironment. This second degree of specificity preferentially links the nanoshells to the tumor and not to neighboring healthy cells.  As shown in this example, scientists can then externally supply energy to these cells. The specific properties associated with nanoshells allow for the absorption of this directed energy, creating an intense heat that selectively kills the tumor cells. The external energy can be mechanical, radio frequency, optical – the therapeutic action is the same.The result is greater efficacy of the therapeutic treatment and a significantly reduced set of side effects.

8.0 NANOPARTICLES
               Nanoscale devices have the potential to radically change cancer therapy for the better and to dramatically increase the number of highly effective therapeutic agents.In this example, nanoparticles are targeted to cancer cells for use in the molecular imaging of a malignant lesion. Large numbers of nanoparticles are safely injected into the body and preferentially bind to the cancer cell, defining the anatomical contour of the lesion and making it visible.


            These nanoparticles give us the ability to see cells and molecules that we otherwise cannot detect through conventional imaging. The ability to pick up what happens in the cell — to monitor therapeutic intervention and to see when a cancer cell is mortally wounded or is actually activated — is critical to the successful diagnosis and treatment of the disease.
            Nanoparticulate technology can prove to be very useful in cancer therapy allowing for effective and targeted drug delivery by overcoming the many biological, biophysical and biomedical barriers that the body stages against a standard intervention such as the administration of drugs or contrast agents.

9.0 CHALLENGES

The six major challenge areas of emphasis include:
   9.1 Prevention and Control of Cancer:
•    Developing nanoscale devices that can deliver cancer prevention agents
•    Designing multicomponent anticancer vaccines using  nanoscale delivery vehicles
   9.2 Early Detection and Proteomics:
•    Creating implantable, biofouling-indifferent molecular sensors that can detect cancer-associated biomarkers that can be collected for ex vivo analysis or analyzed in situ, with the results being  transmitted via wireless technology to the physician
•    Developing “smart” collection platforms for simultaneous mass spectroscopic analysis of multiple cancer-associated markers. 
   9.3 Imaging Diagnostics:
•    Designing “smart” injectable, targeted contrast agents that improve the resolution of cancer to the single cell level
•    Engineering nanoscale devices capable of addressing the biological and evolutionary diversity of the multiple cancer cells that make up a tumor within an individual.
  9.4 Multifunctional Therapeutics:
•    Developing nanoscale devices that integrate diagnostic and therapeutic functions
•    Creating “smart” therapeutic devices that can control the spatial and temporal release of therapeutic agents while monitoring the effectiveness of these agents
  9.5 Quality of Life Enhancement in Cancer:
•    Designing nanoscale devices that can optimally deliver medications for treating conditions that may arise over time with chronic anticancer therapy, including pain, nausea, loss of appetite, depression, and difficulty breathing.
  9.6 Interdisciplinary Training:
•    Coordinating efforts to provide cross-training in molecular and systems biology to nanotechnology engineers and in nanotechnology to cancer researchers.
•    Creating new interdisciplinary coursework/degree programs to train a new generation of researchers skilled in both cancer biology and nanotechnology.

CONCLUSION
                 Work is currently being done to find ways to safely move these new research tools into clinical practice. Today, cancer-related nanotechnology is proceeding on two main fronts: laboratory-based diagnostics and in vivo diagnostics and therapeutics.
 Nanodevices can provide rapid and sensitive detection of cancer-related molecules byenabling scientists to detect molecular changes even when they occur only in a small percentage of cells.        Nanotechnology is providing a critical bridge between the physical sciences and engineering, on the one hand, and modern molecular biology on the other. Materials scientists, for example, are learning the principles of the nanoscale world by studying the behavior of biomolecules and biomolecular assemblies. In return, engineers are creating a host of nanoscale tools that are required to develop the systems biology models of malignancy needed to better diagnose, treat, and ultimately prevent cancer.  In particular, biomedical nanotechnology is benefiting from the combined efforts of scientists from a wide range of disciplines, in both the physical and biological sciences, who together are producing many different types and sizes of nanoscale devices, each with its own useful characteristics.

Scada technology: paper presentation

Scada technology : Paper presentations

ABSTRACT:
SCADA is a computer system for gathering and analyzing “real time data”.SCADA system are used to monitor and control a plant or equipment in industries.

Introduction of SCADA –SCADA systems have made sustainable progress over the recent years in terms of functionality, performance.

Evolution –Created sensaphone SCADA 3000 a Y2K-complaint hardware and software system designed to accommodate in small to mid-sized companies.

The architecture of SCADA– hardware architecture and software architecture.

Functionality – alarm and event monitoring, data acquisition, operator interface, non real time control, Data bases and data logging, use of MMI, logging/archiving, report generation, automation.

Development with the help of SCADA –Rapid expansion in communication systems and increase processing power available at site.

Operation – operation of SCADA with remote telemetry unit.

Applications of SCADA –waste water control and monitoring petroleum and hydrocarbon  rocessing, power generation, food processing, steel manufacturing, Remote tele-communication and plant machinery maintenance.

Case study –Updating SCADA system at power plant for increased capability and reliability.

Advantages and disadvantages – The advantages and disadvantages in using “SCADA” technology.

Developments in SCADA –Tecnomatix technology, Schneider electric’s new telemecanique brand.
Conclusion –purpose of using SCADA systems which reduce down time; increase throughput; limit the frequency of accidents; improve record etc;

SCADA –SUPERVISORY CONTROL AND DATA ACQUISITION:
SCADA stands for Supervisory Control and Data Acquisition. As the name indicates it is not a full control system, but rather focuses on the supervisory level. As such, it is purely software package that is positioned on top of hardware to which it is interfaced, in general via Programmable Logic Controllers (PLC’S), or other commercial hardware modules. Contemporary SCADA systems exhibit predominantly open-loop control characteristics and utilize predominantly long distance communications, although some elements or closed-loop control and/or short distance communications may also be present. It is process control software that remotely gathers “real time data” used in
manufacturing to acquire measurements of process variables and machine states, and for
performing regulatory or machine control. SCADA is used by the energy industry, telecommunication industry, transport industry, and water and waste control industry. SCADA –is also called supervisory control and data acquisition system or supervisory control and data acquisition software.

INTRODUCTION
Widely used in industry for Supervisory Control and Data Acquisition of industrial processes, SCADA systems are now also penetrating the experimental physics laboratories for the controls of ancillary systems such as cooling, ventilation, power distribution, etc. More recently they were also applied for the controls of smaller size particle detectors such as the L3 muon detector and the NA48.
SCADA systems have made substantial progress over the recent years in terms of functionality, scalability, performance and openness such that they are an alternative to in house development even for very demanding and complex control systems as those of physics experiments.

EVOLUTION:
Phonetics created the SENSAPHONE SCADA 3000, a Y2K-complaint hardware and software system design to accommodate small to mid-size companies seeking SCADA control. The system main unit uses two microprocessors to perform all control and communication functions. In terms of hard ware, the standard SENASAPHONE SCADA 3000 is equipped with 16 universal inputs, eight relay outputs, two RS-232 ports for local programming and radio communications, and a four line by 20-characters LCD.

WHAT DOES SCADA MEAN?
SCADA stands for Supervisory Control and Data Acquisition, it is a computer system for gathering and analyzing “real time data” SCADA systems are used to monitor and control a plant or equipment in industries.

SCADA systems are used not only in industrial processes: e.g. steel making, power generation (conventional and nuclear) and distribution, chemistry, but also in some experimental facilities such as nuclear fusion. The size of a plant ranges from few 1000 to several thousand to 10 thousand input/output (I/O) channels. SCADA systems used to run on DOS, VMS, and UNIX; in recent years all SCADA vendors have moved to NT and some also to Linux.

ARCHITECTURE:
1. Hardware Architecture:
One distinguishes two basic layers in a SCADA system: the “client layer” which caters for man machine interaction and the “data server layer” which handles most of the process data control activities. The data servers communicate with devices in the field through process controllers which are connected to data servers.

Figure 1: TYPICAL HARDWARE ARCHITECTURE

2. Software Architecture
The products are multi-tasking and are based upon a real-time database (RTDB) located in one or more servers. Servers are responsible for data acquisition and handling (e.g. polling controllers, alarm checking, calculations, logging and archiving) on a set of parameters, typically those they are connected to.

figure2: GENERIC SOFTWARE ARCHITECTURE

FUNCTIONALITY:
1. Alarms and Event Monitoring:
A SCADA system must be able to detect, display, and log alarms and events. When there are problems the SCADA system must notify the operators to take corrective action. Alarms and event must be recorded so that engineers and programmers can review the alarms to determine what caused the alarm and prevent them happening again. More complicated expressions can be developed by creating derived parameters on which status or limit checking is then performed. The alarms are logically handled centrally, i.e. the information only exists in one place and all users see the same status, and multiple alarm priority levels are supported.

2. Data Acquisition:
SCADA must be able to read data from PLCs and other hardware and then to analyze and graphically present that data to the user. SCADA systems must be able to read and write multiple sources of data.

3. Operator Interface:
A SCADA system collects all of the information about a process. The SCADA systems then need to display this data to the operator so that they can comprehend what is going on with the process.

4. Non Real Time Control:
For simple control requirements, the SCADA system should be able to control instead of a PLC. For anything other than simplistic control we prefer a PLC to do the real time control with SCADA doing the non real time control. The SCADA system is the medium between the operator and the real time controller.

5. Data Bases And Data Logging:
Most applications require recipes, data logging, and other means of reading and writing databases. SCADA systems can log incredible amounts of data to disk for later review. This is helpful for solving problems as well as providing information to improve the process.

6. Use Of MMI:
SCADA uses MMI to present the data acquire from the process to allow the process operation to be supervised e.g. start/stop or changing set points. SCADA provides MMI functions such as: Mimics-a graphical representation of the process with dynamically up dated values; Trends-graphs of variables against selected time periods; Reports-allows process variables to be summarized on a period basis; Alarms-they also support the concept of a “generic” graphical object with links to process variable’s.

7. Logging/Archiving:
Logging is the medium term storage of data on the disk, where as archiving is the long term storage of data on disk or any other permanent storage medium. Logging of data can be performed at a set frequency, or only initiated if the value changes or when a specific predefined event occurs. The logged data is time stamped and can be filtered when viewed by the user.

8. Report Generation:
One can produce reports using SQL type queries to the archive, RTDB or logs. Although it is sometimes possible to embed EXCEL charts in the report. Facilities exist to be automatically generated, print and archive reports.

9. Automation:
The majority of the products allow actions to be automatically triggered by events. Scripting languages provided by the SCADA products allow these actions to be defined. The concepts of receipts is supported, whereby a particular system configuration can be saved to a file and then re-loaded at a latter date. Sequencing is also supported; it is possible to execute a more complex sequence of actions on one or more devices. Sequences may also react to external events.

DEVELOPMENT WITH THE HELP OF SCADA:
SCADA system were developed for gathering data from far and wide using poor quality comms and providing and providing high levels of reliability and operability. Given the rapid expansion of communication systems,(satellite, cellular, fiber, microwave etc)and the increasing processing power available at site.

When the data gathering, integrity and validations requirements of SCADA can be met by commonly used for IT systems, then there will be even further convergence. SCADA system can be justified cost, but the really big payoff is to reduce the capital investment. In many cases the applications that run at that level are becoming more important than the user stuff. However applications like batch tracking and leak detection are SCADA advantages.

OPERATION OF SCADA:
Supervisory control and data acquisition (SCADA) technology collects real-time data from virtually any environment where there is a need to monitor machinery or processes, make adjustments based on measurable conditions, measure down time, or regulate processes to avoid costly problems. The computer-based technology was designed to do all the things with little human involvement. From a central reading location, a SCADA system can monitor a number of remote sites equipped with RTUs. The RTUs measures various conditions and parameters, including tank levels, temperature, voltage, current, volume, and flow. The unit reports the data back to the CPU, carrying out the necessary analysis and cost functions.

Additionally, SCADA technology personal of current or potential alarm situations, allowing an operator to and fine tune a process. Control can be automatic or initiated by operator commands, based on the sophistication of the individual system. The technology is widely accepted as a reliable and efficient control system within numerous industrial markets.

APPLICATION OF SCADA:
A typical SCADA application requires several low cost distributed RTUs, controlled by a central station/master.
Common applications for SCADA systems typically include water and waste treatment, petroleum and hydro carbon processing, power generation, food processing, steel manufacturing, remote telecommunications and plant machinery maintenance. Unlike in plant process control systems, SCADA systems typically include a remote telecommunication link. Real-time measurements and controls at remote stations are transferred to a CPU through the communication link. Large systems can monitor and control 10-2000 remote sites, with each site containing as many as 2000 I/O points.

A SCADA system for small applications:
SCADA is not a new technology by any means, but innovations and significant improvements have been made since its introduction. Until recently, SCADA technology was often viewed as a luxury item by small industrial companies. The technology was deemed unobtainable because of high association with that systems could not be fully used because of their massive I/O capacities.

CASE STUDY:
UPDATING SCADA SYSTEMS AT POWER PLANTS FOR INCREASED CAPACITY, RELIABILITY.
Companies have long monitored and controlled electric power generating
operations using computer-based Supervisory Control and Data Acquisition systems.

Power pumped storage station:
Many power plants are brought on-line and continue to run uninterrupted until maintenance is required. It is a pumped storage hydroelectric plant, designed specifically to help the power plant meet peak demand. Pumped storage is the most economic method of doing so.
The older computer system at the plant was sufficient for monitoring the plant-just barely. It was operating at near capacity. It did not allow the collection and graphic display of data. Therefore the company upgraded the computer system with MODCOMP’s REAL/IX PX operating system a real time implementation of UNIX that runs on Intel-based platforms. The power plant has more computing power and greater flexibility to upgrade in the future because the SCADA system now uses industry standard hardware and software systems.

Defining Goals, System Design:
Power plant began the process of upgrading its SCADA systems with a number of broad goals. Those include:
1. Migrating to standard, open systems with a long useful life.
2. Maintaining existing user interfaces whenever possible.
3. Permitting future expansion without performance degradation.
4. Utilize the existing I/O infrastructure to contain costs.

The new system runs on two Intel-based host servers, one that is the primary system and other is the secondary backup and the information source. In case of hardware failure, plant operators can fail over to the secondary servers. Eight RTUs are connected to the servers. Each of the six generators is monitored by the independent RTUs. The RTUs communicate with the host servers over a dual-redundant fiber optic TPC/IP network. The new system is far more responsive.

Migrating to Open Systems:
The power plant first goal for the new system was to migrate to standard open systems. The new systems use Intel-based computers running the REAL/IX PX operating system. The UNIX operating system platform is compactable with a number of third party programs that power plant can integrate into its SCADA or reporting systems at the later date.

Maintaining User Interfaces, functionality:
The important requirement was to minimize the impact of the changeover on daily operations and the need for re-training. Existing applications software functionality was also migrated into the new SCADA package. The original 10000-point database, with 6500 digital inputs and 3500 analog inputs, was imported into the new software
.
Utilizing Existing I/O, Leaving Room to Grow:
The major challenges for SCADA systems are to keep the majority of the I/O infrastructure and to reduce the cost of the system by interfacing the existing MODACS interface over the new system. The important feature of the SCADA system is its scalability. Secondly, the REAL/IX PX operating system ensures that the systems will continue to run in real time.

New Capabilities:
As the part of the upgrade the power plant wanted to interface its real-time control and data with a data acquisition system with a data historian, creating a historical database for later analysis. Another new capability is remote access for maintenance. System engineers from MODCOMP can dial in to the system, diagnose many problems remotely and fix them. One can expect to see wide scale integration of SCADA and Geographic Information systems (GIS). With GIS, SCADA base users can integrate with real time data to pin point a disruption of service. It will make power companies more productive in determining where faults are located.

ADVANTAGES AND DISADVANTAGES OF SCADA TECHNOLOGY:
Advantages of SCADA system include Wide area connective and pervasive; routable; parallel polling; redundancy and hot stand by ; large addressing ranges; integration of I.T to automation and monitoring net works; standardization; reduce down time; limit the frequency of accidents; improve record; increase through put.

Disadvantages of SCADA Technology include IP performance over head; web enabled SCADA hosts users to remotely monitor, control remote sites via a web browser; security concerns.

DEVELOPMENTS IN SCADA:
SCADA 3000 was released to five beta sites for testing and evaluation. As a result of testing Phonetics has added several features such a additional ladder and C program functions.
Tenomatix technologies new product is eM-Insight, a data source neutral tolerance management and statistical process control product that helps manufacturing companies share and distribute parts inspection data throughout the organization. Schneider Electric’s new Telemecanique brand Unity plat form of PLC processors and automation software provide new tools designed to enhance productivity.

 As far as new technology is concerned the SCADA products are now adopting:
1. Web technology, ActiveX, Java etc.,
2. OPC as a means for communicating internally between the client and server
modules. It should be possible to connect OPC complaint third party modules to the SCADA products.

ENGINEERING:
The need for proper Engineering cannot be sufficiently emphasized to reduced development effort and to reach a system that complies with the requirements, that is economical in development and maintenance and i.e., reliable and robust. The Engineering activities specific to the use of a SCADA system includes templates for different types of panels; Instructions on how to control; a mechanism to prevent conflicting controls; alarm levels, behavior to be adopted in case of specific alarms.

CONCLUSION:
SCADA systems are used to monitor and control a plant and equipment in industries. The benefits one can expect from adopting a SCADA system a rich functionality and extensive development facilities. The systems are used to mission critical industrial processes where reliability and performance are paramount. These systems are used to gather and analyze “real time data”.

REFERENCES:
www.marineeng.com/scada.
www.modcomp.com/scada/virgina_power.html.
www.electronics_x.com/electronic/waste water.html
www.modular-scada.co.uk/what -is-scada.html
www.electronics.com/power generation/scada.html
Under the Guidance of Chinna Subbanna.
A.Daneels, W.Salter, “technology survey summary of survey report.

Electronic Principles by Albert Malvino

Electronic Principles by Albert Malvino:


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Paper presentation: A HIGH PERFORMANCE INDUCTION MOTOR DRIVE SYSTEM USING FUZZY LOGIC CONTROLLER








  
A HIGH PERFORMANCE INDUCTION MOTOR DRIVE SYSTEM USING FUZZY LOGIC CONTROLLER


ABSTRACT
Abstract- Basically, the motor drive system comprises a voltage source inverter-fed induction motor (VSIM): namely a three-phase voltage source inverter and the induction motor. The squirrel-cage induction motor voltage equations are based on an orthogonal d-q reference-rotating frame where the coordinates rotate with the controlled source frequency. The paper presents a novel fuzzy logic controller for high performance induction motor drive system. The inputs to the fuzzy logic controller are the linguistic variables of speed error and change of speed error, while the output is change in switching control frequency of the voltage source inverter. In this paper a comparison between fuzzy logic controller and traditional PI controllers are presented. The results validate the robustness and effectiveness of the proposed fuzzy logic controller for high performance of induction motor drive. Simulink software that comes along with MATLAB was used to simulate the proposed model.

I. INTRODUCTION
Simulink induction machine models are available in the literature [1-2], but they appear to be black boxes with no internal details. Some of them in [1-2] recommend using S functions, which are software source codes for Simulink blocks. This technique does not fully utilize the power and ease of Simulink because S-function programming knowledge is required to access the model variables. Another approach is using the Simulink Power System Block set [3] that can be purchased with Simulink. This block set also makes use of S-functions and is not as easy to work with as rest of the Simulink blocks. Reference [4] refers to an implementation approach similar to the' one in this paper but fails to give any details. In this paper, a modular, easy to understand Simulink induction motor model is described. With the modular system, each block solves one of the model equations. 
Though induction motors have few advantageous characteristics, they also posse's nonlinear and time-varying dynamic interactions [5-6], Using conventional PI controller, it is very difficult and complex to design a high performance induction motor drive system. The fuzzy logic control (FLC) is attractive approach, which can accommodate motor parametric variations and difficulty in obtaining an accurate mathematical model of induction motor due to rotor parametric and load time constant variations.
The FLC is a knowledge-based control that uses fuzzy set theory and fuzzy logic for knowledge representation [7]. This paper presents a novel fuzzy logic controller suitable for speed control of induction motor drives.

II. SIMULINK IMPLEMENTATION
One of the most popular induction motor models derived from this equivalent circuit is Krause's model [6]. An induction machine model can be represented with five differential equations. To solve these equations, they have to be rearranged in the state-space. form,
X=Ax+b Where X=[Fqs FdsFdr Fdr r] T is the state vector.

The inputs of a squirrel cage induction machine are the three-phase voltages, their fundamental frequency, and the load torque. The outputs, on the other hand, are the three phase currents, the electrical torque, and the rotor speed. The d-q model requires that all the three-phase variables have to be transformed to the two-phase synchronously rotating frame. Consequently, the induction machine model will have blocks transforming the three-phase voltages to the d-q frame and the d-q currents back to three-phase. The induction machine model implemented in this paper is shown in Fig. I. It consists of five major blocks: the o-n conversion, abc-syn conversion, syn-abc conversion, unit vector calculation, and the induction machine d-q model blocks. The following subsections will explain each block.

A. O-N Conversion Block:
This block is required for an isolated neutral system, otherwise it can be bypassed. The transformation done by this block can be represented as follows:




B. Unit Vector Block Calculation
Unit vectors cos teta*e and sin teta*e are used in vector rotation blocks, "abc-syn conversion block" and "syn-abc conversion block". The angle teta*e is calculated directly by integrating the frequency of the input three-phase voltages, teta*e.

The unit vectors are obtained simply by taking the sine and cosine of Be' This block is also where the initial rotor position can be inserted, if needed, by adding an initial condition to the Simulink "Integrator" block. Note that the result of the integration is reset to zero each time it reaches2n radians so that the angle always varies between 0 and 2n.

C. abc-syn con version block:

To convert three-phase voltages to voltages in the two phase synchronously rotating frame, they arc first converted to two-phase stationary frame using (3) and then from the stationary frame to the synchronously rotating frame using

where the superscript "s" refers to stationary frame.

D. syn-abc conversion block:

This block does the opposite of the abc-syn conversion block for the current variables using (5) and (6) following the same implementation techniques as before.







E. Induction machined-q model block:


The resulting model is modular and easy to follow. Any variable can be easily traced using the Simulink 'Scope' blocks. The blocks in the first two columns calculate the flux linkages, which can be used in vector control systems in a flux loop. The blocks in Column 3 calculate all the current variables, which can be used in the current loops of any current control system and to calculate the three-phase currents. The two blocks of Column 4, on the other hand, calculate the torque and the speed of the induction machine, which again can be used in torque control or speed control loops, These two variables can also be used to calculate the output power of the machine.

III. OPEN-LOOP CONSTANT V/HZ OPERATION



Fig. 5 shows the implementation of open-loop constant V1Hzcontrol of an induction machine. This figure has two new blocks: command voltage generator and 3-phasePWM inverter blocks. The first one generates the three-phase voltage commands, and it is nothing more than a "syn-abc" block explained earlier. The latter first compares the reference voltage, Vref to the command voltages to generate PWM signals for each phase, then uses these signals to drive three Simulink "Switch" blocks switching between +VJ2 and -Vd/2 (Vd: dc link voltage). The open-loop constant V/Hz operation is simulated for 1.2s ramping up and down the speed command and applying step load torques. The results are plotted in Fig. 3 where the response of the drive to changes in the speed command and load disturbance scan be observed.






IV. FUZZY LOGIC CONTROL ALGORITHM
A fuzzy algorithm consists of situation and action pairs. Conditional rules expressed in IF and THEN statements are generally used. For example, the control rule might be: if the output is lower than the requirement and the output is dropping moderately then the input to the system shall be increased greatly. Such a rule has to be converted into a more generally statement for application to fuzzy algorithms. To achieve this the following terms are defined: error equals the set point minus the process output, error change equals the error from the process output minus the error from last output: and control input applied to the process. In addition, it is necessary to quantize the qualitative statements and the following linguistic sets are assigned
1. Large Positive(LP)            2. Medium Positive (MP)
3. Small Positive(SP)            4. Zero (ZZ)   
5. Small Negative(SN)        6. Medium Negative (MN)   
7. Large Negative(LN)
Thus the statement of the example control will be: if the error is large positive and the error change is small positive then the input to the system is large positive.

V. FUZZY CONTROL ACTION
1.    Specify and store the minimum and the maximum ranges of the error signal E=er(k) , the error change dE= der(k)and the control input change df.

2.    If the minimum and maximum ranges of step one are different then quantize then into a common universe of discourse using scaling factors such that the maximum and minimum of the quantized error signal E, the quantized error change dE, and the quantized control input changed f are all the same.

3.    Define the symmetrical linguistic fuzzy subsets of E, dE, and df.

4.    Calculate the error er and the error change der for the current sampling period and find their quantized values E and dE respectively in the common universe of discourse.

5.    From the E and dE the contribution of each rule given in table 1in the fuzzy subsets of control input df and scaling of its membership grades using the rule can be found.



6.    The result of application of all rules is membership function grades of control input df through the universe of its discourse. To calculate the crisp or numerical value of df the COA Criteria is used as follows:


Where n is the number of quantization levels of the output.
7.    Add the control input change dF(k) to the previous value F(k-l) to calculate the new control action to be taken for the kth sample: F(k)=F(k-l)+dF(k).

Table. 1. Fuzzy Control Rule Decision Table
 
VI. CLOSED LOOP CONSTANTV/Hz OPERATION

The closed loop circuit has the fuzzy logic controller as the new component. The inputs to the fuzzy logic controller are the speed error and rate of change of speed error. The output is fed to the power



converter-pwm inverter, which is used to adjust the inverter switching control frequency. The output of FLC controls the firing angle of the inverter, thereby varying the output voltages. The reference speed of the pwm inverter is modified each time when there is a different output of the fuzzy controller. These outputs are found from the truth table (rule table). The pwm inverter output is then fed to the induction machine where a constant V/Hz operation is carried out.

VII. SIMULATION RESULTS
The output of the fuzzy logic controller (FLC) is used to adjust the inverter switching control frequency and the dc voltage at the inverter using a constant (VF) ratio. The induction motor drive system using FLC is shown in Fig 4. Results were obtained using a three-phase squirrel cage induction motor with 208 volt phase to phase voltage, 60Hz rated frequency, 1750 rpm rated speed and 1/4 Hp rated power. The parameters of the motor at rated conditions in per unit are given by (all per unit values are based on Base=1/4 Hp, Vbase=208volt and Ibase=1.2amp) Rs=198 p.u. Rr=1353P.u., X1s=1l7 p.u., & Xlr=.l17 p.u., XM=2.2 p.u

VIII. CONCLUSION
This paper presents a simple, novel and robust fuzzy logic speed controller for high performance

induction motor drives. The FLC does not need exact knowledge of induction motor and tolerate range load excursions and parametric variations. The control assignment rules are obtained using heuristic trial and error and human expertise. The simulation test results validate the FLC robustness for different speed trajectories.

REFERENCES
[1] P. C. Krause, Analysis of Electric Machinery ,McGraw-Hill Book Company, 1986 f71L.A.Zadeh,"Outlineof a New Approach to the Analysis of Complex Systems and Decision Processes", IEEE Trans. Systems, Man, and Cybernetics,No.3, PP.28-44,1973.
 [2] N.T. M. Mohan Undeland and W.P.Robbins, "Power Electronics Converter, Applications and Design" john Wiley & Sons Inc. Canada, 1989.
[3] L. Tang, M. F. Rahman, “A new direct torque control strategy for flux and torque ripple reduction for induction motors drive – a Matlab/Simulink model,” IEEE International Electric Machine and Drives Conference,2001,pp.884-890.
[4] Bimal K. Bose,Modern Power Electronics and AC Drives, Prentice Hall, 2002.
 [5]. P. C. Krause, Analysis of Electric Machinary, McGraw-Hill Book Compeny,1986

Paper presentation: Remote Detection of Illegal Electricity Usage via Power Line Communications

A Solution to Remote Detection of Illegal Electricity
Usage via Power Line Communications



ABSTRACT:
Power line communication (PLC) presents an interesting and economical solution for Automatic Meter Reading (AMR). If an AMR system via PLC is set in a power delivery system, a detection system for illegal electricity usage may be easily added in the existing PLC network. In the detection system, the second digitally energy meter chip is used and the value of energy is stored. The recorded energy is compared with the value at the main kilo Watt-hour meter. In the case of the difference between two recorded energy data, an error signal is generated and transmitted via PLC network. The detector and control system is proposed. The architecture of the system and their critical components are given. The measurement results are given.

This paper describes detector system for illegal electricity usage using the power lines based on the research work-taking place at the Central Power Research Institute (CPRI), Bangalore. The target of this study is to discover new and possible solutions for this problem.


1. INTRODUCTION :
India, the largest democracy with an estimated population of about 1.04 billion, is on a road to rapid growth in economy. Energy, particularly electricity, is a key input for accelerating economic growth. The theft of electricity is a criminal offence and power utilities are losing billions of rupees in this account. If an Automatic Meter Reading system via Power line Communication is set in a power delivery system, a detection system for illegal electricity usage is possible .Power line communications (PLC) has many new service possibilities on the data transferring via power lines without use of extra cables. Automatic Meter Reading (AMR) is a very important application in these possibilities due to every user connected each other via modems, using power lines. AMR is a technique to facilitate remote readings of energy consumption.
The following sections will describe the proposed detection and control system for illegal electricity usage using the power lines. The scheme is based on the research work-taking place at “Central Power Research Unit (CPRI), Bangalore ”.In this section the discussion is on how a subscriber can illegally use the electricity and the basic building blocks for the detection using power line communication.

Methods of illegal electricity usage:
In illegal usage a subscriber illegally use electricity in the following ways,

1) Using the mechanical objects: A subscriber can use some mechanical objects to prevent the revolution of a meter, so that disk speed is reduced and the recorded energy is also reduced.

2) Using a fixed magnet: A subscriber can use a fixed magnet to change the electromagnetic field of the current coils. As is well known, the recorded energy is proportional to electromagnetic field.

3) Using the external phase before meter terminals: This method gives subscribers free energy without any record.

4) Switching the energy cables at the meter connector box: In this way, the current does not pass through the current coil of the meter, so the meter does not record the energy consumption.
Although all of the methods explained above may be valid for electromechanical meters, only the last two methods are valid for digital meters. Therefore, this problem should be solved by electronics and control techniques .

2 BUILDING BLOCKS FOR DETECTION:

2.1. Automatic Meter Reading (AMR): The AMR system starts at the meter. Some means of translating readings from rotating meter dials, or cyclometer style meter dials, into digital form is necessary in order to send digital metering data from the customer site to a central point.



Fig 1: Electromechanical movement to digital signal conversion.

In most cases, the meter that is used in an AMR system is the same ordinary meter used for manual reading but the difference with conventional energy meter is the addition of some device to generate pulses relating to the amount of consumption monitored, or generates an electronic, digital code that translates to the actual reading on the meter dials. One such technique using optical sensor is shown in above fig……

Three main components of AMR system are:
1. Meter interface module: with power supply, meter sensors, controlling electronics and a communication interface that allows data to be transmitted from this remote device to a central location.

Fig:2 AMR communication setup

2. Communications systems: used for the transmission, or telemetry, of data and control send signals between the meter interface units and the central office.
3. Central office systems equipment: including modems, receivers, data concentrators, controllers, host upload links, and host computer [4].

2.2 POWER LINE COMMUNICATION (PLC):
Power line carrier communications take place over the same lines that deliver electricity. This technique involves injecting a high frequency AC carrier onto the power line and modulating this carrier with data originating from the remote meter or central station. Power line communications has many new service possibilities on the data transferring via power lines without use of extra cables. AMR is a very important application in these possibilities due to every user connected each other via power lines. In this power network, every user connected to each other via modems with data originating from the remote meter or central station. Electrical power systems vary in configuration from country to country depending on the state of the respective power sources and loads. The practice of using medium-voltage (11-to-33kV) and low-voltage (100-to-400V) power distribution lines as high-speed PLC communication means and optical networks as backbone networks is commonplace.Under normal service conditions, they can be broadly divided into open-loop systems, each with a single opening, and tree systems with radial arranged lines. In the case of tree systems, connection points for adjacent systems are provided in order that paths/loads may be switched when necessary for operation. Additionally, in terms of distribution line types, there are underground cables and overhead power distribution lines. Where transformers are concerned, they can be divided into pole-mounted transformers, pad-mounted transformers and indoor transformers.


Figure 3: Schematic illustration of detection system of illegal electricity usage

High-speed PLC applications of the future include Automatic Meter Reading (AMR), power system fault detection, power theft detection, leakage current detection, and the measurement/control/energy-management of electrical power equipment for electrical power companies, as well as home security, the remote- monitoring/control of electrical household appliances, online games, home networks, and billing [3].

3. DETECTION AND CONTROL SYSTEM:
The proposed control system [1] for the detection of illegal electricity usage is shown in Fig.3. PLC signaling is only valid over the low voltage VAC power lines. The system should be applied to every low-voltage distribution network. The system given in Fig. 3 belongs only one distribution transformer network and should be repeated for every distribution network. Although the proposed system can be used uniquely, it is better to use it with automatic meter reading system. If the AMR system will be used in any network, the host PLC unit and a PLC modem for every subscriber should be contained in this system. In Fig. 3, the host PLC unit and other PLC modems are named PLC1A, PLCNA and are used for AMR. These units provide communication with each other and send the recorded data in kilowatt-hour meters to the PLC unit. In order to detect illegal usage of electrical energy, a PLC modem and an energy meter chip for every subscriber are added to an existing AMR system. As given in Fig. 3, PLC1B, PLCNB and energy meter chips belong to the detector.The detector PLC s and energy meters must be placed at the connection point between distribution main lines and subscriber’s line. Since this connection point is usually in the air or at underground, it is not suitable for anyone to access, such that its control is easy. The main procedure of the proposed system can be summarized as follows.PLC signaling must be in CENELEC standards. In Europe, CENELEC has

formed the standard EN-50 065-1, in which the frequency bands, signaling levels, and procedures are specified. 3–95 kHz are restricted for use by electricity suppliers, and 95–148.5 kHz are restricted to consumer use. The recorded data in kilowatt-hour meters for every subscriber are sent to host PLC modem via PLC modems, which is placed in subscriber’s locations. On the other hand, energy meter chips are located at the connection points and read the energy in kilowatt-hours and also send the data to host PLC unit. This proposed detector system has two recorded energy data in host PLC unit, one, which comes from the AMR-PLC, and the other, which comes from the PLC modem at the connection points. These two recorded energy data are compared in the host PLC. If there is any difference between two readings, an error signal is generated. This means that there is an illegal


usage in the network. After that, the subscriber address and error signal are combined and sent to the central control unit. If it is requested, a contactor may be included to the system at subscriber locations to turn off the energy automatically, as in the case of illegal usage.



Fig4: illegal detector system of one subscriber

3.1. SIMULATION:
The system model and simulation of the detection system of illegal electricity usage is shown in Fig. 4. It contains a host PLC modem, an energy meter chip and its PLC modem, an electromechanical kilowatt-hour meter and its PLC modem, and an optical reflector sensor system is loaded at the same phase of the power grid. The energy value at the electromechanical kilowatt-hour meter is converted to digital data using by optical reflector sensor. Disk speed of the kilowatt-hour meter is counted and obtained data is sent to PLC modem as energy value of the kilowatt-hour meter. At the system model, an illegal load may be connected to the power line before the kilowatt-hour meter via an S switch. While only a legal load is in the system, two meters are accorded each other to compensate for any error readings. The host PLC unit reads two recorded data coming from metering PLC units. If the S switch is closed, the illegal load is connected to the system, and therefore two recorded energy values are different from each other.

Fig 5: System simulation and modeling of the detection system of illegal electricity usage for electromechanical kilowatt-hour meters

The host PLC unit is generated when it received two different records from the same subscriber. This is the detection of the illegal usage for interested users. In these tests, the carrier frequency is selected at 132 kHz, which is permitted in the CENELEC frequency band. In real applications the AMR systems may be designed in CENELEC bands. The data rate between the host and other PLC modems is 2400 b/s.
Data signaling between PLC modems has a protocol, which includes a header, address, energy value data, error correction bits, and other serial communication bits such as parity and stop bits. The protocol may also be changed according to the properties of the required system and national power grid architecture. Fig.5 shows the detection system for an electromechanical kilowatt-hour meter system. In the digital energy meter system, the recorded energy may be received in the digital form directly using the port of the meter. Therefore, there is no need for an optical reflector system in digital meters. The results of the tests show that this system may solve this problem economically because the budget of the proposed system is approximately U.S. $ 20–25 per subscriber. It is very economical and is a reliable solution when it is compared with the economic loss caused by illegal usage [1].

4. OVER VIEW OF THE PROPOSED DETECTOR SYSTEM:
The proposed detector system is the equipment and procedure for controlling more remote stations from a master control station. It includes PLC modems, energy meters, control logics, and the system software. The PLC modems are host and target modems for two-way communications to and from the host station and the remotely controlled targets. The energy meters include metering chips and some circuit elements; the control and logic units compare and generate the error signal in the
Illegal usage.


The system software has two parts: assembler program for the micro controller and the operating software for the management of the overall system. Operating software may be downloaded from a PC and should be placed in the main center of the system.
An AMR system including an illegal detector performs the following functions.
1) Every user has two PLC modems; one is for AMR and the other is used to send the data from second energy meter chip to host PLC modem.
2) An energy meter must be installed in the connection box between a home line and main power lines.
3) The host PLC unit must be placed in the distribution transformer and the configuration of the addressing format of PLC signaling must be designed carefully.
4) Operating software must be designed for the information of every subscriber in every sub power network: subscriber identification number, billing address, etc……..
5) The system has two values of the energy consumption for every user, so if there is a difference between them, an error signal is generated for the illegal user,
6) The proposed equipment is the only one distributed in the power network. So this system should be repeated for all distribution power networks. All host units in each distribution transformer may be connected to only one main center station via phone lines, fiber-optic cable, or RF links.



Fig 7: Bit-error probability with frequency and load impedance for 1000-m [2]


Results and the variations of the measurements are shown in Figs. 6–7 [2]. The relations between frequency, length, and bit-error probability are given in these figures.. Research work has been taking place in the CPRI, Bangalore for the remote metering and detection of power theft and will soon be helpful to electricity boards in India.

5. CONCLUSION :
The proposed detector system to determine illegal electricity usage via power line communications is examined in the laboratory conditions. Results proved that if AMR and detector system are used together illegal usage of electricity might be detected. Once this proposed detection systems are tried in real power lines, the distribution losses in India can be reduced effectively.

6. REFERENCES :
[1] I. H. Cavdar, “A Solution to Remote Detection of …” IEEE Transactions on power delivery, Vol. 19..
[2] I. H. Cavdar, “Performance analysis of FSK power line communications systems over the time-varying channels: Measurements and modeling,” IEEE Trans. Power Delivery, vol. 19, pp. 111–117, Jan. 2004.
[3] Yoshinori Mizugai and Masahiro Oya “World Trends in Power Line Communications” Mitsubishi Electric
[4] Tom D Tamar kin “Automatic Meter Reading”, Public Power magazine Volume50, Number5 September-October 1992.

Paper presentation: Z-SOURCE INVERTER FOR ADJUSTABLE SPEED DRIVES


 


Z-SOURCE INVERTER
FOR
ADJUSTABLE SPEED DRIVES
(A Novel ASD System)
 


ABSTRACT
This paper presents a Z-source inverter system and control for adjustable speed drives (ASD). The Z-source inverter employs a unique LC network to couple the inverter main circuit to the diode front end. By controlling the shoot-through duty cycle, the Z-source can produce any desired output ac voltage, even greater than the line voltage. As results, the new Z-source inverter system provides ride-through capability under voltage sags, reduces line harmonics, and extends output voltage range. Simulation results will be presented to demonstrate the new features.




1. INTRODUCTION
The Traditional ASD system is based on a voltage-source inverter (V-source inverter), consisting of a diode rectifier front end, dc link capacitor, and inverter bridge as shown in Fig. 1. Because of the V-source inverter, the ASD system suffers the following common limitations and problems.
• Obtainable output voltage is quite limited below the input line voltage. The V-source inverter is a buck (step-down) inverter. For example, Fig. 1 illustrates
voltages of a 3-phase 230 V drive system, where the diode rectifier powered by the 230–V ac line produces about 310–V dc, under which the inverter can only produce a maximum 190–V ac in the linear modulation range. For a 230–V motor, the low obtainable output voltage significantly limits output power that is proportional to the square of the voltage. This is a very undesirable situation for many applications where the motor and drive system has to be oversized.
• Voltage sags can interrupt an ASD, thus shutting down critical loads and processes. Over 90% of power quality related problems are from momentary (typically 0.1–2 s)
voltage sags of 10–50% below nominal. The dc capacitor in an ASD is a relatively small energy storage element, which cannot hold dc voltage above the operable level under such voltage sags. Lack of ride-through capacity is a serious problem for sensitive loads driven by ASDs.
• Inrush and harmonic current from the diode rectifier can pollute the line.
A recently developed new inverter called Z-source inverter has a niche for ASD systems to overcome the above problems. A Z-source inverter-based ASD system can
• produce any desired output ac voltage, even greater than the line voltage;
• provide ride-through during voltage sags without any additional circuits;
• reduce in-rush and harmonic current.
This paper presents the basic idea of an ASD system using the Z-source inverter, its main circuit configuration, an equivalent circuit, and control. Simulation results are included to demonstrate the idea and features of the new ASD system.




2. Z-SOURCE ASD SYSTEM
Fig. 2 shows the main circuit configuration of the proposed Z-source inverter ASD system. Similar to that of the traditional ASD system, the Z-source ASD system’s main circuit consists of three parts: a diode rectifier, dc-link circuit—Z-source network,  and an inverter bridge. The only difference is the dc link circuit (or Z-source network: C¬1 and C2 and L¬1 and L2) and small input capacitors (Ca, Cb, and Cc) connected to the diode rectifier. Since the Z-source inverter bridge can boost the dc capacitor (C¬1 and C2 ) voltage to any value that is above the average dc value of the rectifier, a desired output voltage is always obtainable regardless the line voltage. Using the 230 V ASD system as an example, the dc capacitor voltage is boosted to 350 V in order to produce 230–V ac output as shown in Fig. 2. Theoretically, the dc capacitor voltage can be boosted to any value above the inherent average dc voltage (310 V for 230V ac) of the rectifier, by using shoot-through zero switching states when a higher output voltage is needed or during voltage sags. The maximum dc capacitor voltage will be limited by the device voltage rating in practical use, however.

3. EQUIVALENT CIRCUIT:
        OPERATING PRINCIPLE AND CONTROL
In the proposed ASD system in Fig. 2, a diode rectifier bridge with input capacitors (Ca, Cb, and Cc) serves as the dc source feeding the Z-source network. The input capacitors are used to suppress voltage surge that may occur due to the line inductance during diode commutation, thus requiring a small value of capacitance. At any instant, only two phases (of the three-phase diode bridge) that have the largest potential difference (i.e., the two phases cross the one of the input capacitors that has the highest voltage) may conduct, carrying current from the ac side to the dc side. Therefore, viewed from the Z-source network the diode bridge can be modeled as a dc source (i.e., one of the input capacitors) in series with two diodes as shown in Fig. 3.

The two diodes (D pa, b or c and D na, c or a) conduct as a pair with the capacitor (C a,b,or c). Note the suffix combinations that indicate diodes D pa and Dnb form a pair with capacitor Ca when voltage cross capacitor Ca (i.e., the voltage cross phases “a” and “b”) is the highest; and with D pa and Dnc with Cb when voltage cross capacitor Cb (i.e., the voltage cross phases “b” and “c”) is the highest; Dpc and Dna and Cc when voltage cross capacitor Cc (i.e., the voltage cross phases “c” and “a”) is the highest, respectively. Further, the two diodes conduct in a pair and in series acting as one when viewed from the Z-source network. Therefore, the proposed Z-source ASD system is reduced to a Z-source inverter.
The traditional three-phase V-source inverter has six active states in which the dc voltage is impressed across the load and two zero states in which the load terminals are shorted through either the lower or upper three devices, respectively. However, the three-phase Z-source inverter bridge has additional zero states when the load terminals are shorted through both the upper and lower devices of any one phase leg (i.e., both devices are gated on), any two phase legs, or all three phase legs. These shoot-through zero states are forbidden in the traditional V-source inverter, because it would cause a shoot-through. There are seven different shoot-through states: shoot-through via any one phase leg, combinations of any two phase legs, and all three phase legs. The shoot-through zero states boost dc capacitor voltage while producing no voltage to the load. It should be emphasized that both the shoot-through zero states and the two traditional zero states short the load terminals, produce zero voltage across the load, and thus preserve the same PWM properties and voltage waveforms to the load. The only difference is that shoot-through zero states boost the dc capacitor voltage, whereas the traditional zero states do not. For the proposed ASD system, the three-phase inverter bridge is controlled the same way as the traditional pulse width modulation (PWM) inverter without shoot-through when a desired output voltage is less than 190 V ac, which is the maximum voltage obtainable from 230 V line using the linear PWM. The diode rectifier functions such as the traditional one producing about 310Vacross the dc capacitors (C1 and C2 ). When a higher output voltage is required or when the line voltage sags, the shoot-through zero states are employed to boost the dc capacitor voltage. The longer time the shoot-through zero states are used, the higher the voltage one gets. By controlling the shoot-through zero state interval, a desired dc voltage can be maintained.



4. SIMULATION VERIFICATION OF THE ASD SYSTEM
Simulations have been carried out to confirm the operating principle of the new ASD system. In order to show clearly the output voltage obtained from the inverter, an LC filter with 1 kHz cutoff frequency is placed in-between the inverter bridge and the motor. The simulation parameters are as follows:
1) three-phase line voltage: 230–V, line impedance: 3%;
2) Load: three-phase 230–V 20 KW induction motor;



3) Input capacitors ( Ca,Cb , andCc ): 10 micro farads ;
4) Z-source network: L1 =L2=160 micro Henry, C1=C2= 1000 micro farads;
5) Switching frequency: 10 kHz.
Figs. 4 and 5 show simulation waveforms under the nominal line voltage of 230 Vac. The output inverter voltage is just like the traditional PWM waveform with a modulation index of 1.0. After the 1 kHz LC filter, the voltage becomes sinusoidal, indicating a 230 V rms value, which is not obtainable by the traditional ASD system.






Fig. 5 shows the inductor current and dc capacitor voltage, which has been boosted to 343 V. The maximum dc voltage was boosted to 376 V and should be limited below the device voltage rating, which can be 450 V for a 600 V IPM. The boost factor was 1.21. Also it is noted that the line current contains fewer harmonics because of the Z-source network and input capacitors.



Figs. 6 and 7 show simulation waveforms during 50% voltage sag (the line voltage drops to 115 Vac). The waveforms clearly demonstrate that the dc capacitor voltage can be boosted and maintained to a desired level, which in this case is above 300 V. The boost factor was 2.8 and the modulation index was 0.82.

5. CONCLUSIONS

This paper has presented a new ASD system based on the Z-source inverter. The Z-source inverter ASD system has several unique features that are very desirable for many ASD applications:
• produce any desired output ac voltage, even greater than the line voltage;


• provide ride-through during voltage sags without any additional circuits;
• reduce in-rush and harmonic current.

6. BIBLIOGRAPHY
      1. B.K.Bose."Adjustable speed ac drive systems."

       2. Y. Kim and S. Sul, “A novel ride-through system for adjustable-speed
drives using common-mode voltage,”


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