This paper addresses a new method to design a PI-based load-frequency control (LFC) with communication delays. First the LFC problem is reduced to a static output feedback control synthesis for a multiple delays power system, and then the control parameters are easily carried out via a mixed H ₂ /H _infin control technique, using a developed iterative linear matrix inequalities (ILMI) algorithm. The proposed method is applied to a 3-control area power system and the results are compared with a delayless H _infin -based control design

Spontaneous emission is one of the important noise sources in semiconductor laser amplifiers (SLAs). In this paper we analyze the dynamic behavior of this phenomenon in SLA based on numerical solution of the carrier and field rate equations. From the numerical results we obtain the evolution of the gain and amplified spontaneous emission dynamics which presented for the first time.

In a deregulated environment, Automatic Generation Control (AGC), as an ancillary service essential for maintaining the system reliability, acquires a fundamental role to enable power exchanges and to provide better conditions for electricity trading. Since the AGC system is faced with new uncertainties in the liberalized electricity market, a reevaluation in traditional modeling and control structures is highly needed. In response to the coming challenge of integrating computation, communication, and control into appropriate levels of system operation and control, this work introduces a multi-agent-based scenario to perform the automatic generation control task in a deregulated environment.

Load frequency control (LFC) has been one of the major subjects in electric power system design/oper- ation and is becoming much more significant today in accordance with increasing size and the changing structure and complexity of interconnected power systems. In practice, power systems use simple propor-tional-integral (PI) controllers for frequency regulation and load tracking. However, since the PI controller parameters are usually tuned based on classical or trial and error approaches, they are incapable of obtaining good dynamical performance for a wide range of operating conditions and various load changes sce- narios in a restructured power system. This paper addresses a new decentralized robust LFC design in a deregulated power system under a bilateral based policy scheme. In each control area, the effect of bilateral contracts is taken into account as a set of new input signals in a modified traditional dynamical model. The LFC problem is formulated as a multi-objective control problem via a mixed H2/H1 control technique. In order to design a robust PI controller, the control problem is reduced to a static output feedback control synthesis, and then, it is solved using a developed iterative linear matrix inequalities algorithm to get a robust performance index close to a specified optimal one. The proposed method is applied to a 3 control area power system with possible contract scenarios and a wide range of load changes. The results of the proposed multi-objective PI controllers are compared with H2/H1 dynamic controllers.

In many real world control problems, we have to follow several control objectives, simultaneously. At the same time, it is usually desirable to meet all specified goals using the controllers with simple structures such as proportional-integral (PI) and proportional-integral-derivative (PID) which are useful in industry applications. Since, practically these controllers are commonly tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamical performance to capture all design objectives and specification. With regard to above problem, this paper addresses a new method to design of multi-objective PI/PID controller. For this purpose, first the multi-objective control design is reduced to an H/sub 2//H/sub /spl infin// static output feedback control synthesis, and then the control parameters are easily carried out using an iterative linear matrix inequalities (ILMI) algorithm. As a numerical example, the proposed method is applied to a multi-area power system to design a set of PI-based robust load frequency controllers.

This paper addresses a new method to design a PI-based load-frequency control (LFC) with communication delays. First the LFC problem is reduced to a static output feedback control synthesis for a multiple delays system, and then the control parameters are easily carried out using robust H_∞ control technique. A 3-control area power system example is given to illustrate the proposed control methodology and the results are compared with the H_∞-based delay-less control system design.

In a deregulated environment, Load-frequency control (LFC), as an ancillary service essential for maintaining the system reliability, acquires a fundamental role to enable power exchanges and to provide better conditions for the electricity trading. Since the LFC system is faced by new uncertainties in the liberalized electricity market, a reevaluation in traditional modeling and control structures is highly needed. In response to the coming challenge of integrating computation, communication and control into appropriate levels of system operation and control, a comprehensive scenario is proposed to perform the LFC task in a deregulated environment. As a part of the mentioned scenario, this paper addresses a new method to design of robust LFC with considering the communication delays. First the LFC problem is reduced to a static output feedback control synthesis for a multiple delays power system, and then the control parameters are easily carried out via a mixed H2/H∞ control technique, using a developed iterative linear matrix inequalities (ILMI) algorithm. The proposed method is applied to a 3-control area power system ∞and the results are compared with the recently developed H∞ -based LFC designs.

Automatic control design has been one of the major subjects in real-world system design/operation and is becoming much more significant today in accordance with increasing size, changing structure, uncertainties and complexity of artificial industry systems. A major challenge in a new environment is to integrate computing, communication and control into appropriate levels of real-world system operation and control. In practice, many control systems usually track different control objectives such as stability, disturbance attenuation and reference tracking with considering practical constraints, simultaneously. At the moment in the industry applications, it is desirable to meet all specified goals using the controllers with simple structures. Since, practically these controllers are commonly designed based on experiences, classical and trial-and-error approaches, they are incapable of obtaining good dynamical performance to capture all design objectives and specifications for a wide range of operating conditions and various disturbances. It is significant to note that because of using simple structure, pertaining to the low-order control synthesis for dynamical systems in the presence of strong constraints and tight objectives are few and restrictive. Under such conditions, the synthesis process may not approach to a strictly feasible solution. Therefore, the most of robust and optimal approaches suggest complex state-feedback or high-order dynamic controllers. Moreover in the most of proposed approaches, a single performance criterion has been used to evaluate the robustness of resulted control systems. This research addresses three systematical, fast and flexible algorithms to design of low order or static output controllers for dynamical systems. The developed strategies attempt to invoke the strict conditions and bridge the gap between the power of optimal/robust control theory and industrial control design. To illustrate the effectiveness of the proposed control

This paper addresses a modified dynamical model to analysis of load-frequency control (LFC) in a bilateral-based restructured power system. In a new environment, vertically integrated utilities no longer exist, however the common objectives, i.e. restoring the frequency and the net interchanges to their desired values for each control area are remained. It is assumed that each distribution company (Disco) is responsible for tracking its own load and honoring tie-line power exchange contracts with its neighbors by securing as much transmission and generation capacity as needed. Therefore the overall power system structure can be considered as a collection of distribution areas as separate control areas interconnected through high voltage transmission lines or tie-lines. A three control areas power system example with possible contract scenarios and load changes is given to illustrate the generalized model.

In many real world control problems, it is usually desirable to meet specified control goals using controllers with simple structures like as proportional-integral (PI) and proportional-integral derivative (PID) which are useful in industry applications. Since practically, these controllers are commonly tuned based on experiences, classical or trial-and-error approaches, they are incapable of obtaining good dynamical performance to capture design objectives. This paper addresses a systematic method to design robust PIIPID controllers based on H∞ -control technique. First the PIIPID control problem is reduced to an H∞ -static output feedback control synthesis, and then the control parameters are easily carried out using an iterative linear matrix inequalities (ILMI) algorithm. A numerical example and simulations are given to illustrate the proposed methodology.

This paper addresses a control strategy to design a PIbased load-frequency control (LFC) in face of communication delays. First the PI-based LFC design is transferred to a static output feedback (SOF) control design and then to obtain the optimal PI gains, a multi constraint minimization problem is solved using the H∞control technique.A multi-area power system example is given to
illustrate the proposed control methodology and the results are compared with the delay less system-based H∞ control design.

In this paper, using the multi layer perceptron (MLP) neural network, we determine the breakdown voltage for separate absorption and multiplication region avalanche photodiode (SAM-APD). Also, we analyze the sensitivity of breakdown voltage with different parameters. As examples, live devices are simulated with the model.

In a deregulated environment, Automatic Generation Control (AGC), as an ancillary service essential for maintaining the system reliability, acquires a fundamental role to enable power exchanges and to provide better conditions for the electricity trading. Since the AGC system is faced by new uncertainties in the liberalized electricity market, a reevaluation in traditional modeling and control structures is highly needed.In response to the coming challenge of integrating computation, communication and control into appropriate levels of system operation and control, this work introduces a multi-agent based scenario to perform the automatic generation control task in a deregulated environment.

We present a detailed analysis of the static tuning characteristics of three-section tunable DBR laser using transfer matrix method. The key feature of the analysis is the use of modified oscillation condition. With exact oscillation condition, the static tuning characteristics such as threshold current, output power, oscillating wavelength are obtained and the effects of a discontinuity at the active-passive interface and also the manufacturing imperfections on the device characteristics are investigated.

Boost DC-to-DC converters have very good source interface properties. The input inductor makes the source current smooth and hence these converters provide very good EMI performance. On account of this good property, the boost converter is also the preferred converter for off-line UPF rectifiers. One of the issues of concern in these converters is the large size of the storage capacitor on the DC link. The boost converter suffers from the disadvantage of discontinuous current injected to the load. The size of the capacitor is therefore large. Further, the ripple current in the capacitor is as much as the load current; hence the ESR specification of the tank capacitor is quite demanding. This is specially so in the emerging application areas of automotive power conversion, where the input voltage is low (typically 12 V) and large voltage boost (4 to 5) are desired. In the UPF rectifier applications, the input voltage varies from zero to maximum value twice in every cycle of the AC input voltage. The duty cycle therefore varies in the full range of zero to one. The inductor current varies from zero to rated current twice in every AC cycle of the input current. On account of these wide operating point variations, the design of the power circuit as well as the closed loop controller is a demanding task. This paper suggests polyphase operation of boost converter to overcome the disadvantages of large size storage capacitor in boost converter and off-line UPF rectifiers and a small signal analysis of N converters in parallel to an equivalent second order system in such converters, which have not been considered in previous works

In this paper we calculate the spatial dependency of the spontaneous emission in semiconductor laser cavity using a model based on transmission line laser method (TLLM). Results show that in the simple ridge laser structure, the major part of the spontaneous emission occurs at the middle of the cavity and so uniform spontaneous emission can’t be assumed

A decentralized robust approach is proposed for an automatic generation control (AGC) system based on a generalized AGC structure. This work addresses a new strategy to adapt a well-tested classical AGC scheme to the changing environment of power system operation under deregulation. The effect of bilateral contracts is taken into account in each control area dynamical model as a set of new input signals. The PI-based AGC synthesis is formulated via an H/spl infin/ static output control problem and is solved using an iterative linear matrix inequalities (ILMI) algorithm. A three area power system example with possible contract scenarios and wide range of load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and maintain the robust performance.

This paper addresses a new decentralized robust strategy to adapt the well tested classical automatic generation control (AGC) system to the changing environment of power system operation under deregulation based on the bilateral AGC scheme. In each control area, the effect of bilateral contracts is taken into account in a modified traditional dynamical model as a set of new input signals. The AGC problem is formulated as a multi-objective control problem, and the mixed H₂/H_∞ control technique is used to synthesis the desired robust controllers for AGC design in a multi-area power system.A three area power system example with possible contract scenarios and a wide range of load changes is given to illustrate the proposed approach. The results of the proposed control strategy are compared with the pure H_∞ method. The resulting controllers are shown to minimize the effect of disturbances and maintain robust performance.

This paper addresses a new decentralized robust LFC design in a deregulated power system under bilateral-based policy scheme. The LFC problem is formulated to a PI based multi-objective control problem via a mixed H/sub 2//H/sub /spl infin// control technique. The robust PI control problem is reduced to a static output feedback control synthesis, and it is solved using a developed iterative linear matrix inequalities algorithm to get a robust performance index close to specified optimal one. The proposed method is applied to a 3-control area power system with possible contract scenarios and a wide range of load changes. The results are compared with H/sub 2//H/sub /spl infin// dynamic control design.

The modeling idea presented in Ref. (1) is generalized to obtain the dynamical model for load-frequency control (LFC) analysis and synthesis in a bilateral-based restructured power system. In each control area, the effect of bilateral contracts is taken into account as a set of new input signals. It is assumed that each distribution company (Disco) is responsible for tracking its own load and honoring tie-line power exchange contracts with its neighbors by securing as much transmission and generation capacity as needed.

In this paper, we analyze the dynamic behavior of semiconductor laser amplifier (SLA) using numerical solution of the carrier and field rate equations. From the numerical results we obtain the gain dynamics, the carrier density evolution, and the transient response of SLA for an input optical pulse and different bias currents.

In this paper, a general robust control synthesis framework is proposed for DC-DC quasi-resonant converters (QRCs) in order to achieve both stability and desired performance, such as reduced sensitivity to load variations, desired disturbance rejection, reduced output impedance and attenuated transfer from input to output. The /spl mu/-analysis is used to design and verify the robustness of the resulted controller. The proposed control strategy is applied to a typical zero-current switching QRC and nonlinear simulation is performed using nonlinear model of converter circuit. The simulation results demonstrate the good reference voltage tracking, line disturbance rejection and show that the designed procedure guarantees the robust stability and robust performance for a wide range of load variation.

The load-frequency control (LFC) problem has been one of the major subjects in electric power system design/operation and is becoming much more significant today in accordance with increasing size, changing structure and complexity of interconnected power systems. In practice LFC systems use simple proportional-integral (PI) controllers. However, since the PI controller parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamical performance for a wide range of operating conditions and various load changes scenarios in a multi-area power system. For this problem, the decentralised LFC synthesis is formulated as an H∞-control problem and is solved using an iterative linear matrix inequalities algorithm to design of robust PI controllers in the multi-area power systems. A three-area power system example with a wide range of load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimise the effect of disturbances and maintain the robust performance.

In this paper, a decentralized robust approach is proposed for load-frequency control (LFC) design in a deregulated environment using bilateral market scheme. First, the effect of bilateral contracts as a set of new input signals is taken into account in the control area dynamical model, and then the LFC problem will be formulated as a multi-objective problem to cover robust performance, practical constraint on control action and minimize the effects of load disturbance under wide range of demand changes. A mixed H/sub 2//H/sub /spl infin// is used to solve the problem and design the desired robust controllers. A three-control areas power system example with possible contract scenarios and load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and maintain the robust performance.

A new systematic approach to design of sequential decentralized load frequency controllers for multi-area power systems based on μ synthesis and analysis is described. System uncertainties, practical constraints on control action and desired performance are included in the synthesis procedure. The robust performance in terms of the structured singular value is used as a measure of control performance. A four area power system example is presented, demonstrating the controllers’ synthesis procedure and advantages of the proposed strategy.

This paper addresses a robust control method to decentralized PI-based load-frequency control (LFC) synthesis in a multi-area power system. The LFC problem is reduced to a static output feedback H∞ control problem and then it is solved using a developed iterative linear matrix inequalities (ILMI) algorithm to get an optimal performance index. A three control area power system example with a wide range of load changes is given to illustrate the proposed approach. The obtained controllers are compared with full dynamic H∞ controllers. The results show the proposed controllers guarantee the robust performance for a wide range of operating conditions as well as full-dynamic H∞ controllers.

In this paper, a decentralized robust approach is proposed for the Automatic Generation Control (AGC) system based on a modified traditional AGC structure. This work addresses the new strategy to adapt well-tested classical AGC scheme to the changing environment of power system operation under deregulation. The effect of bilateral contracts is considered as a set of new input signals in each control area dynamical model.
  In practice, AGC systems use simple proportional-integral (PI) controllers. However, since the PI controller parameters are usually tuned based on classical or trial-and-error approaches, they are incapable of obtaining good dynamical performance for a wide range of operating conditions and various scenarios in deregulated environment. In this paper with regard to this problem, the AGC synthesis is formulated as an H_∞ static output control problem and is solved using a developed iterative linear matrix inequalities (ILMI) algorithm to design of robust PI controllers in the restructured power system control areas. A three area power system example with possible contract scenarios and wide range of load changes is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and maintain the robust performance.

An approach based on structured singular value theory is proposed for the design of robust load frequency controller in response to the new technical control demand for large scale power systems in a deregulated environment. In this approach the power system is considered under the pluralistic Load Frequency Control (LFC) scheme, as a collection of different control areas. Each control area can buy electric power from some generation companies to supply the area-load. The control area is responsible to perform its own LFC by buying enough power from pre-specified generation companies, which equipped with robust load frequency controller.
A three area power system example is given to illustrate the proposed approach. The resulting controllers are shown to minimize the effect of disturbances and achieve acceptable frequency regulation in presence of uncertainties and load variation.

This paper addresses a robust control method to decentralized PI-based load-frequency control (LFC) synthesis in a multi-area power system. The LFC problem is reduced to a static output feedback H∞ control problem and then it is solved using a developed iterative linear matrix inequalities (ILMI) algorithm to get an optimal performance index. A three control area power system example with a wide range of load changes is given to illustrate the proposed approach. The obtained controllers are compared with full dynamic H∞ controllers. The results show the proposed controllers guarantee the robust performance for a wide range of operating conditions as well as full-dynamic H∞ controllers.

This paper addresses a new decentralized robust control design for load-frequency control (LFC) in multi-area power systems. The LFC problem is considered as a multi-objective problem and formulated via a mixed H2/H∞ control technique, then it is easily carried out to synthesis the desired robust controllers by solving standard linear matrix nequalities (LMI). A three-area power system example with a wide range of load changes is given to illustrate the proposed approach. The results are compared with pure H∞ method. It is shown that the designed controllers maintain the robust performance, minimize the effect of disturbances and specified uncertainties, effectively.

DC-DC quasi-resonant converters (QRCs) have a highly nonlinear and time-varying behavior as well as other types of DC-DC resonant converters such as conventional and multi-resonant converters. Changing in operating conditions, mainly due to variation in load and line disturbance, leads to significant changes on system dynamics so that desired performance and even stability are lost. Taking into consideration the uprising need for high-quality resonant power converters has opened a new research window on the control of these systems using modern and systematic approaches.
In this paper in order to achieve both stability and desired performance, such as reduced sensitivity to load variations, desired disturbance rejection, reduced output impedance and attenuated transfer from input to output, we have proposed a methodology based on μ-synthesis technique for DC-DC QRCs controller design. The μ-analysis is used to verify the robustness of the designed controller. The proposed control strategy is applied to a typical zero-current switching QRC and nonlinear simulation is performed using nonlinear model of converter circuit. The simulation results demonstrate the good reference voltage tracking, line disturbance rejection and show that the designed procedure guarantees the robust stability and robust performance for a wide range of load variation.

An approach based on /spl mu/-synthesis and analysis theory is proposed for the design of load frequency controller in response to the new technical control demand for power system in a deregulated environment. In this approach the power system is considered as a collection of separate control areas and each control area can buy electric power from some generation companies to supply the area-load. The proposed technical scenario is illustrated with application to the design of load-frequency controller for a typical control area. The resulting controller is shown to minimize the effect of disturbances and achieve acceptable frequency regulation in presence of uncertainties and load variation.

A new approach based on /spl mu/-synthesis technique is proposed for the design of robust load frequency controller in response to the new technical demand for load frequency regulation in a competitive distributed generation power system. The siting of numerous generator units in distribution feeders is being encouraged by the current deregulation of the industry is likely to have an impact on the load frequency control (LFC) operation of the existing power systems. In this approach the overall power system will be divided to some distribution areas. Each area is modeled as a collection of distributed generators to supply the area-load. The area is responsible to perform its own LFC by using an independent robust controller. An example for a distribution area is given to illustrate the proposed approach. The resulting controller is shown to minimize the effect of disturbances and achieve acceptable frequency regulation in presence of uncertainties and load variation.

The siting of numerous generator units in distribution areas is being encouraged by the current deregulation of the industry is likely to have an impact on the frequency regulation of the existing power systems, which designed to operate with large and central generating facilities. An approach based on µ-synthesis technique is proposed for the design of robust load frequency controller in response to the new Load Frequency Control (LFC) technical demand for multi-machine power systems. An example for a multimachine area is given to illustrate the proposed approach. The resulting controller is shown to minimize the effect of disturbances and achieve acceptable frequency regulation in presence of uncertainties and load variation

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A new systematic approach to design of sequential decentralized load frequency controllers for multi-area power systems based on μ-synthesis is described. System uncertainties according to load, practical constraint on control action and desired performance are included in the synthesis procedure. The robust performance in terms of the structured singular value is used as a measure of control performance. A 3-area power system example is presented demonstrating the controllers synthesis procedure and advantages of this method.

Resonant converters have a highly nonlinear and time-varying nature. Any change in operating conditions leads to significant changes in system dynamical model so that desired performance and even stability are lost. This situation is mainly due to variation in load and line voltage. Taking into consideration the uprising need for high-quality resonant power converters comes the need for modern and systemic approaches to the control of these systems. In this paper to access both satisfactory stability and satisfactory performance, such as reduced sensitivity to line voltage and load variations, satisfactory disturbance rejection, reduced output impedance, and attenuated transfer from input to output, we use the /spl mu/-synthesis technique for a zero-current switching (ZCS) converter.

This paper demonstrates a flexible neural networks application, as a possible solution, to an automatic load frequency control problem in a deregulated electric power system environment. We consider a typical power system in a competitive, distributed control environment with open access organizational structure. With this new structure, the conventional controllers are incapable of obtaining good dynamical performance, then there is a need for novel control strategies to maintain the reliability and eliminates the frequency error. In order to achieve all proposed design objectives, we have used flexible neural networks with dynamic neurons that have wide ranges of variation. A sample power system is used to illustrate the design method.

Robust control design for resonant converters

The electric power industry is in transition from large and regulated utilities to an industry that will incorporate competitive companies selling unbundled power at lower rates. The new structure of electric power systems, which includes separate companies with an open access policy demands novel control strategies to maintain the stability and eliminates the frequency error. Under current organization several approaches have already been proposed. This paper addresses the design and introduce of reduced load frequency controller based on μ-synthesis theorem for a possible structure in the new deregulated open access environment. We used the singular values of the observability matrix of the high order μ-controller for reducing the controller order.

Any power system has a fundamental control problem of matching real power generation to load plus losses, a problem called load frequency control ( LFC) or frequency regulation. The purpose of load frequency control is tracking of load variation while maintaining system frequency and tie line power interchanges close to specified values. With introduction of the deregulation policy to the power system operation, a lot of interests have been recently refocused on the LFC. That is because the conventional controllers are incapable of obtaining good dynamical performance, then, it comes the need for novel control strategies to maintain the reliability and eliminates the frequency error. Recently, under deregulated organizations, several notable LFC scenarios based on classical, robust/adaptive and intelligent control theorems have been proposed. In this paper, by using of obtained results, the authors make varies comparisons between these approaches and discuss the main advantages and disadvantages of these methods.