Thyristors

This paper presents an overview of the state of the art in reactive power compensation technologies. The principles of operation, design characteristics and application examples of Var compensators implemented with thyristors and self-commutated converters are presented. Static Var generators are used to improve voltage regulation, stability, and power factor in ac transmission and distribution systems. Examples obtained from relevant applications describing the use of reactive power compensators implemented with new static Var technologies are also described.

Study about application of thyristors -solid state four layers p-n-p-n semicondutors -in the industry, both in manufacture stage and as part of end product. The thyristors are more commonly represented by Silicon Controlled Rectifiers -the SCRs -but are also represented by many authors by TRIACs, DIACs, MOSFETs and others. In thits study, their represented more accuracy than contactors, relays and other devices, specially on high volgate networks and power conversion.

The main aim of this work is to damp out power system oscillations, which has been recognized as one of the major concerns in power system operation. In a Static Synchronous Series Co mpensator (SSSC), a controllable A C voltage is generated by a voltage-source converter. There are two control channels for controlling the magnitude and phase of the voltage. This work describes the damping of power oscillations by static synchronous series compensator (SSSC) based damping controllers. The advantage of this approach is that it can handle the nonlinearit ies, at the same time it is faster than other conventional controllers and it improve the reactive power of the system. Simu lation studies will be carried out in Matlab/Simu link environ ment to evaluate the effectiveness of the proposed Static synchronous series compensator (SSSC) of mu lti-area power system. Results will show that the proposed SSSC based damping controllers improve the dampin g performance of the in the event of a major d isturbance.

The specifications of a highly flexible controller for a three-phase McMurray inverter are defined and the construction of a suitable controller is described. The controller is capable of operation in either the six step or pulsewidth modulation mode and incorporates safe start-up and shut-down procedures. The operation of the controller is illustrated by a series of inverter and controller oscillograms.

This paper presents a new three-phase pulse width modulated (PWM) half-controlled rectifier using a new PWM control strategy such that the low-order harmonic content in both the input current and the output voltage is reduced. Further, the circuit operates with a unity displacement factor at its input and uses minimum power components. The new PWM strategy developed allows its implementation on a three-phase half-controlled rectifier bridge with only three controlled switches to obtain PWM controlled rectification. Although the circuit operation is explained with force-commutated SCR switches, the basic controlled PWM operation is valid for any alternative controlled switches like GTO or transistors, which do not require the commutating power components. The circuit has wide applications ranging from rectifiers to battery chargers to motor drives. Even if an input current filter is desired, its size will be small due to the PWM pattern used.

With the increasing growth of population and development of industries, huge amount of sums are spent to increase the production of electricity and installation of new units. In this paper, a new method has been presented which reduces the aforementioned costs and prevents the losses in national capitals and fuel sources. This method finds the optimal location of Thyristor controlled series capacitor (TCSC) in transmission network by using genetic algorithm. Due to the use of fossil fuels in power plants, the application of this method is necessary in countries with the high cost of electricity. The effectiveness of the proposed method has been illustrated in a 10-bus network as a case study.

The 6.5 kV insulated gate bipolar transistor (IGBT) is a new promising power device for high-voltage high-power applications. Due to its increased voltage blocking capability, the new HV IGBT can serve as a good replacement for GTO and IGCT thyristors in medium or medium-to-high power applications. One of its general application fields is railway traction. The paper discusses design and development considerations of the 50-kW auxiliary power supply to be used in 3.0 kV DC commuter trains. Focus is on the implementation of 6.5kV IGBTs in the primary inverter of APS to improve overall power density, system integrity as well as reliability of the whole system. For instance, topology selection, analysis and simulation of functional blocks of a converter for different operation points are described. A prototype of half-bridge isolated DC/DC converter with two 6.5kV 200A IGBT transistors was designed and built. Some design considerations are specified in the paper.

Se analiza el proceso de diseño y la simulación de un esquema de filtro activo híbrido aplicable a tensiones medias sin necesitar de transformadores reductores para tal fin. Se muestra el desarrollo del método de compensación usado y los resultados obtenidos cuando se aplica en un sistema de conversión de alterna a continua basado en tiristores. El sistema se simula para diferentes niveles de tensión de alimentación.

As power system interconnections become more prevalent, there has been an increase in use of thyristor controlled shunt connected compensation devices for dynamic power compensation and enhancement of real power transmission capacity. In this paper, an enhancement technique of real power transfer capacity of transmission lines is presented. A static var compensator (SVC) is designed and applied to a simple power system for this purpose. Increase in power flow and improvement in bus voltage profile are observed after using the SVC. Stability analysis of the system after experiencing fault as well as consequent fault clearance by time domain analysis has also been performed and satisfactory results are obtained.

the main objective of this paper is to investigate the enhancement of power system stability via coordinated design of Thyristor Controlled Series Compensation (TCSC) and Power System Stabilizers (PSSs) in multimachine power system. The design problem of the proposed controllers is formulated as an optimization problem. Using the developed linearized power system model, the particle swarm optimization (PSO) algorithm is employed to search for optimal controllers' parameters settings that maximize the minimum damping ratio of all system eigenvalues. The proposed controller is evaluated on a multimachine power system. The nonlinear simulation results and eigenvalue analysis show the effectiveness of the proposed controller in damping power system oscillations.

Realization of on-chip electrostatic discharge (ESD) protection requires extensive technical experience and know-how. A technology computer-aided design (TCAD) methodology aimed to assist in the design and implementation of robust ESD devices is developed and presented. The methodology provides a systematic and practical means for the evaluation and optimization of ESD devices in a simulation environment. Advanced siliconcontrolled-rectifier devices are considered to illustrate the approach, and experimental data measured from these devices are also included in support of the TCAD development.

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The Flexible AC Transmission Systems (FACTS) devices can help the power system networks to reduce power flows on overloaded lines, resulting in increased system loadability, lower transmission line losses, improved power system stability and security, reduced power production costs, and more secure bus voltage levels. This paper presents a genetic algorithm (GA) based optimization process, for seeking optimal locations and parameters for multi-type FACTS devices in power systems. The optimization process is designed to maximize the power transmitted by the network. Five different FACTS devices are considered: SVC, TCSC, TCVR, TCPAR and UPFC. The simulation results show the effectiveness of the proposed optimization process in determining optimal placement of FACTS devices in several test networks.

Realization of on-chip electrostatic discharge (ESD) protection requires extensive technical experience and know-how. A technology computer-aided design (TCAD) methodology aimed to assist in the design and implementation of robust ESD devices is developed and presented. The methodology provides a systematic and practical means for the evaluation and optimization of ESD devices in a simulation environment. Advanced siliconcontrolled-rectifier devices are considered to illustrate the approach, and experimental data measured from these devices are also included in support of the TCAD development.

It is an important issue to study sea clutter suppression because it could interfere with the detection of targets above the sea surface severely. Spatial spectrum analyses show that the majority of sea clutter has low-frequency characteristics, compared to the high-frequency characteristics of the targets. This paper proposes a frequency-based spatial tracking filter to suppress sea clutter to facilitate targets identification. Experimental results show that the signal-to-clutter ratio can increase by more than 10 dB after filtering and the algorithm is feasible for practical use. In addition, the filtering equation can be optimized to maximize the signal-to-clutter ratio improvement. The equation parameters can also be adjusted to give a proper cut-off frequency for different targets and clutter.

This paper presents a three-phase 12-pulse phasecontrolled rectifier with unity displacement factor, low line current harmonic content, two quadrant operation and absence of phase shifting transformer. The circuit is composed by two three-phase 6-pulse rectifiers parallel connected by four balancing reactors.

This brief presents a quantitative analysis of the operating characteristics of three-phase diode bridge rectifiers with ac-side reactance and constant-voltage loads. We focus on the case where the ac-side currents vary continuously (continuous ac-side conduction mode). This operating mode is of particular importance in alternators and generators, for example. Simple approximate expressions are derived for the line and output current characteristics as well as the input power factor. Expressions describing the necessary operating conditions for continuous ac-side conduction are also developed. The derived analytical expressions are applied to practical examples and both simulations and experimental results are utilized to validate the analytical results. It is shown that the derived expressions are far more accurate than calculations based on traditional constant-current models.

Today, the development and integration of train and ship controllers is a more difficult task than ever. Emergence of high-power switching devices has enabled the development of new solutions with improved controllability and efficiency. It has also increased the necessity for more stringent test and integration capabilities since these new topologies come with less design experience on the part of the system designers. To address this issue, a real-time simulator can be a very useful tool to test, validate and integrate the various subsystems of modern rail vehicle devices. This paper presents such a real-time simulator, based on commercial-off-the-shelf PC technology, suitable for the simulation of train and ship propulsion devices.

Robust and novel devices called high-holding low-voltage trigger silicon controlled rectifiers (HH-LVTSCRs) for electrostatic discharge (ESD) protection of integrated circuits (ICs) are designed, fabricated and characterized. The S-type current-voltage (I-V) characteristics of the HH-LVTSCRs are adjustable to different operating conditions by changing the device dimensions and terminal interconnections. Comparison between complementary n- and p-type HH-LVTSCR devices shows that n-type devices perform better than p-type devices when a low holding voltage (VH) is allowed during the on-state of the ESD protection structure, but when a relatively high holding voltage is required, p-type devices perform better. Results further demonstrate that HH-LVTSCRs with a multiple-finger layout render high levels of ESD protection per unit area, applicable in the design of ICs with stringent ESD protection requirements of over 15 kV IEC.

Abstruct-A new adaptive control system for dc motor drive with field weakening is proposed. The adaptation mechanism is based on the gain scheduling. A deep knowledge of the phenomena in the drive was necessary to define the scheduled variables that capture the essential nonlinearities of the process considered. However, in practice, to realize the proposed adaptive control system, the only a priori knowledge required is the experimentally determined magnetization curve. Simulation and experimental results indicating high performances of the control system proposed, are presented.

Polyimide layers have been applied by a simple blade squeeze technique on double-mesa high voltage thyristor devices for its electrical passivation. Reverse and forward electrical blocking characteristics were measured as a function of polyimide application and curing processing conditions. During high temperature reverse bias reliability test, the thyristors showed appreciable leak-current increment, but after three day thermal process, the devices showed lower leakage currents than that devices fabricated by conventional glassivation technique.

A single-phase to three-phase cycloconverter system operating from a 50-Hz input has been simulated under various loading conditions using a PSPICE circuit simulator. The Giacolleto SCR model has been modified. Detailed waveforms of load voltage, load current, and current of various semiconductor-controlled rectifiers (SCR) have been plotted. It has been demonstrated that for low and medium L/R loads a simple constant firing angle sequence works well, whereas the cosine wave crossing method (CWCM) seems to be optimum for high L/R loads. Theoretical results are validated with the experimental results.

A problem with transaction system which requires an open network to carry out operations using a smart card is that the user does not know which information signs with his smart card. In addition, users do not have any proof about the smart card reader authenticity. Architecture of a trustworthy smart card reader to guarantee the correct operations of the smart card is proposed. A secure coprocessor is integrated inside the smart card reader to provide a safe place in order to store sensitive data and support different system level security services. The design includes a barrier substrate, x-ray sensor, temperature sensor and voltage monitors to detect any attempt of modification.

The most used deduster in industrial applications are plate-type electrostatic precipitators. They can treat high gas flows obtained from various burning processes, but their price is high. These costs depend mostly on the number of fields. An analysis was performed using experimental data collected from different plate-type electrostatic precipitators in a thermoelectric power plant. The following items were analysed: the collection efficiency, the speed distribution of the dust particles in the fields, and some electrical parameters for three types of electrostatic precipitators: with two, three and four fields.

In this work a new model is developed for power thyristors which contains amplifying gate and emitter-shorts. This model will be based on the two dimensional two-transistor circuit model of a thyristor. We use Gummel-Poon circuit model because it takes into consideration the high injection effects and the Conductivity modulation of the low n-doped region. The model parameters are defined and extracted according to a new methodology. The simulation results are compared with the measured results. It has been found that the developed model satisfactorily describes the performance of the thyristor under practical operating conditions.

The ESD robustness on different device structures and layout parameters of high-voltage (HV) NMOS has been investigated in 40-V CMOS process with silicon verification. It was demonstrated that a specific structure of HV n-type silicon controlled rectifier (HVNSCR) embedded into HV NMOS without N-drift implant in the drain region has the best ESD robustness. Moreover, due to the different current distributions in HV NMOS and HVNSCR, the trends of the TLP-measured It2 under different spacings from the drain diffusion to polygate are different.

A three-phase ac power control circuit using power transistors which operate in a high-frequency chopping mode is described. The circuit is capable of handling several kilowatts of power at any lagging load power factor angle and the output voltage can be smoothly controlled from zero to full supply voltage. The circuit has inherently fast response and the high-frequency ripple at the output is easily filtered. The development, study, and experimental evaluation of the circuit with resistive and induction motor loads is described.

Industrial electrolytic rectifiers work with high currents (in the order of kilo Amps) and very low dc voltage levels (few hundred Volts). The preferred industrial solutions for this type of application are Thyristor-based double-bridge and four-star multi-pulse rectifiers. A number of alternative more advanced rectifiers have been recently proposed presenting improved electrical properties, such as reduced harmonic distortion and reduced reactive power consumption. The various tradeoffs existent between these topologies however are presently only evaluated qualitatively. This paper addresses this present lack of proper design tools and proposes an engineered quantitative solution for the evaluation and selection of high current rectifiers. The proposed method is based on the reliability, electrical performance, efficiency and required equipment investment for these rectifiers. The IEEE Standards 493-1997 and IEEE C57.18.10 for reliability and efficiency are the basis of this method, being used specifically to configure the evaluation platform. Complete results for the standard double-bridge and four-star rectifiers, together with improved rectifier topologies including the chopper-rectifier, the sequential rectifier, and the filterless rectifier are presented and thoroughly discussed in the paper. From these, it is concluded that the modular multi-cell technology used in the chopper high-current rectifier is capable to challenge the long-used Thyristor-based industrial solutions.

Stability is one of the main challenges in the power grid. Power System Stablizer (PSS) is the main system used to damp oscillations of the conventional power grid, but it is not adequate for all problems. Therefore, other compensator must be added to increase reliability of the power system. TCSC is one of FACTS devices that can be used for this purpose. In this paper, the controller of TCSC is tuned using Genetic Algorithm (GA) to damp the oscillations of the power grid. A fault for a single machine is simulated in MATLAB software and the performance of the system with and without the proposed TSCS is compared to illustrate the advantages of the proposed system.

The turn-on mechanism of a silicon-controlled rectifier (SCR) device is essentially a current triggering event. While a current is applied to the base or substrate of the SCR device, it can be quickly triggered into its latching state. In this paper, a novel design concept to turn on the SCR device by applying the substrate-triggered technique is first proposed for effective on-chip electrostatic discharge (ESD) protection. This novel substrate-triggered SCR device has the advantages of controllable switching voltage and adjustable holding voltage and is compatible with general CMOS processes without extra process modification such as the silicide-blocking mask and ESD implantation. Moreover, the substrate-triggered SCR devices can be stacked in ESD protection circuits to avoid the transient-induced latch-up issue. The turn-on time of the proposed substrate-triggered SCR devices can be reduced from 27.4 to 7.8 ns by the substrate-triggering technique. The substrate-triggered SCR device with a small active area of only 20 m 20 m can sustain the HBM ESD stress of 6.5 kV in a fully silicided 0.25-m CMOS process.

A method for determining parameters for a two-transistor SCR model from SCR specification sheet data developed by Hu and Ki (1979) for use with the CAD program SPICE2 was examined. The model was found to need improvement in order to simulate the SCR turn-off transient in an inductive circuit. An improved model was then developed for SPICE2 which was demonstrated to perform satisfactorily through simulation of AC resonant charging circuits having one or two SCR's. The original and the modified Hu-Ki models are presented together with the simulation results.

Silicon-controlled rectifiers (SCRs) are frequently used to build on-chip electrostatic discharge (ESD) protection structures, but SCRs are not sufficiently robust to meet a wide range of ESD requirements in various integrated circuits. In this paper, a novel and robust SCR-based device called the HHLVTSCR is presented. It is demonstrated that HHLVTSCR can exhibit various characteristics useful for ESD solutions. An example is also included to illustrate how HHVLTSCRs can be used to provide ESD protection to a practical application.

A simple model for a thyristor driven dc motor is rigorously established. The derivation is based on the machine equations and on the definition of a pseudoinstantaneous meanvalue function. The influence of the converter on the voltage applied to the dc motor is considered. The final model includes ail significant effects, has the same structure for continuous and discontinuous current conduction modes, and allows simple control synthesis. The model is compared to the classical model of a dc motor and the differences are highlighted. With the proposed model, it is easy to understand the influence of a thyristor converter on the dynamic performance of a dc motor and, therefore, this formulation has a significant educational aspect. A dual-mode adaptive current controller is designed using this model. Experimental and simulation results are compared to validate the work.

This paper computes the small signal dynamic response of a thyristor controlled series capacitor system for use in control design. The computation includes the effects of synchronization and the nonlinearity due to thyristor switchings. Eigenvalues of the small signal dynamic response are computed and used to study the dynamic response of the Kayenta system using different methods of synchronization and a closed loop control.

Stability is one of the main challenges in the power grid. Power System Stablizer (PSS) is the main system used to damp oscillations of the conventional power grid, but it is not adequate for all problems. Therefore, other compensator must be added to increase reliability of the power system. TCSC is one of FACTS devices that can be used for this purpose. In this paper, the controller of TCSC is tuned using Genetic Algorithm (GA) to damp the oscillations of the power grid. A fault for a single machine is simulated in MATLAB software and the performance of the system with and without the proposed TSCS is compared to illustrate the advantages of the proposed system.

Electrostatic discharge (ESD) protection devices fabricated in a low-voltage CMOS process for communication interface applications typically provide relatively small blocking voltage, thus limiting the interface operating voltage range for which the ESD device can be used. This letter introduces a CMOS-based silicon controlled rectifier with a large blocking voltage beyond ±20 V and a high trigger current. Such a high blocking voltage is achieved by selectively defining native-buffer regions in critical blocking junctions of the device. Experimental characterization of the ESD robustness and standing operation are presented to validate the new device for low capacitance, high-voltage-tolerant communication interface ESD protection applications.

Although formal methods for developing computer systems have been available for more than a decade, few have had significant impact in practice. A major barrier to their use is that software developers find formal methods difficult to understand and apply. One exception is a formal method called SCR for specifying computer system requirements which, due to its easy to use tabular notation and its demonstrated scalability, has already achieved some success in industry. Recently, a set of software tools, including a specification editor, a consistency checker, a simulator, and a verifier, has been developed to support the SCR method . This paper describes recent enhancements to the SCR tools: a new dependency graph browser which displays the dependencies among the variables in the specification, an improved consistency checker which produces detailed feedback about detected errors, and an assertion checker which checks application properties during simulation. To illustrate the tool enhancements, a simple automobile cruise control system is presented and analyzed.

The static and dynamic parameters of bipolar power diode are optimized by the use of helium irradiation. The optimal position for the defect peak caused by the irradiation was found in the n-base very close to the anode junction. This was verified by both the simulation and the experiment.

InGaN-GaN multiple-quantum-well (MQW)-based photodetectors, with a detection edge at 450 nm and a high responsivity, have been fabricated and characterized. We show that the performance of MQW-based photodetectors strongly depends on a proper device design, i.e., number of QWs, and barrier and blocking layer thickness and doping level. Namely, the responsivity can be varied in the 1 to 100 mA/W range in similar structures and with the same number of QWs. These results support a model where the photocurrent increase is due to the improvement of collection efficiency caused by a change in transport mechanism for carriers photogenerated in the QWs. The transport mechanism depends on the location of the QWs in relation to the depletion region.