Power System Dynamic Performance Research Articles

Dynamic Stability Enhancement of Power Systems Using Neural-Network Controlled Static-Compensator

This paper aims at enhancement of dynamic stability of power systems using artificial neural network (ANN) controlled static VAR compensator (SVC). SVC is proven the fact that it improves the dynamic stability of power systems apart from reactive power compensation; it has multiple roles in the operation of power systems. The auxiliary control signals to SVC play a very important role in mitigating the rotor electro-mechanical low frequency oscillations. Artificial neural network based controller is designed using the generator speed deviation, as a modulated signal to SVC, to generate the desired damping, is proposed in this paper. The ANN is trained using conventional controlled data and hence replaces the conventional controller. The ANN controlled SVC is used to improve the dynamic performance of power system by reducing the steady-state error and for its fast settling. The simulations are carried out for multi-machine power system (MMPS) at different operating conditions.

Dynamics of Type-3 Wind Turbine Generator Models

The influence of wind turbine generators (WTGs) on power system dynamic performance is becoming increasingly important as wind generation grows. The dynamic behavior of WTGs should therefore be thoroughly understood. The paper analyzes dynamic models of type-3 WTGs, and in particular the WECC generic model. The behavior of such models is governed by interactions between the continuous dynamics of state variables, and discrete events associated with limits. It is shown that these interactions can be quite complex, and may lead to switching deadlock that prevents continuation of the trajectory. Switching hysteresis is proposed for eliminating deadlock situations. Various type-3 WTG models include control blocks that duplicate integrators. It is shown that this leads to non-uniqueness in the conditions governing steady-state, and may result in pre- and post-disturbance equilibria not coinciding. It also gives rise to a zero eigenvalue in the linearized WTG model.

Fuzzy based HVDC regulation controller for load frequency control of multi-area system

This paper investigates the load frequency control (LFC) problem for a multi-area power system taking into consideration system parameter variations. This paper proposes an intelligent control scheme for LFC of interconnected power systems. A fuzzy logic based integral controller is proposed for two-area power system interconnected via parallel AC/DC transmission link, which is also referred as asynchronous tie-lines. The linear model of AC/DC link with HVDC regulation controller is developed and the system responses to sudden load change are studied. The simulation studies are carried out for a two area interconnected power system with non-reheat steam turbine for simplicity and without loss of generality. Suitable solution for LFC problem of two-area electrical power system is obtained by means of improving dynamic performance of power system under study. Robustness of controller is also checked by varying parameters. Simulation results indicate that the proposed control scheme work well when compared with others.

Fuzzy Controller Design of TCSC with ANFIS to Improve the Dynamic Stability of Power System

In this paper, a new variable fuzzy control algorithm is proposed for thyristor-controlled series capacitor (TCSC) to improve power system dynamic performance. Rules of adaptive neuron fuzzy inference system (ANFIS) devise this fuzzy controller for TCSC in power system. ANFIS uses a hybrid learning algorithm to identify the membership function parameters of Sugeno-type fuzzy inference system. Consequences of this control trend are compared with PI controller and it is shown by using fuzzy controller the system has more stable power flow and less power oscillations. Simulation results signify power stability improvement of two-area power system by using fuzzy controller in TCSC than traditional PI controller.

Automatic Generation Control in Multi Area Interconnected Power System by using HVDC Links

T his paper investigates the effects of HVDC link in parallel with HVAC link on automatic generation control (AGC) problem for a multi-area power system taking into consideration system parameter variations. A fuzzy logic controller is proposed for four area power system interconnected via parallel HVAC/HVDC transmission link which is also referred as asynchronous tie-lines. The linear model of HVAC/HVDC link is developed and the system responses to sudden load change are studied. The simulation studies are carried out for a four area interconnected thermal power system. Suitable solution for automatic generation control problem of four area electrical power system is obtained by means of improving the dynamic performance of power system under study. Robustness of controller is also checked by varying parameters. Simulation results indicate that the scheme works well. The dynamic analyses have been done with and without HVDC link using fuzzy logic controller in Matlab-Simulink. Further a comparison between the two is presented and it has been shown that the performance of the proposed scheme is superior in terms of overshoot and settling time. DOI: http://dx.doi.org/10.11591/ijpeds.v2i1.182

NEURAL NETWORK PREDICTIVE CONTROL BASED POWER SYSTEM STABILIZER

The present study investigates the power system stabilizer based on neural predictive control for improving power system dynamic performance over a wide range of operating conditions. In this study a design and application of the Neural Network Model Predictive Controller (NN-MPC) on a simple power system composed of a synchronous generator connected to an infinite bus through a transmission line is proposed. The synchronous machine is represented in detail, taking into account the effect of the machine saliency and the damper winding. Neural network model predictive control combines reliable prediction of neural network model with excellent performance of model predictive control using nonlinear Levenberg-Marquardt optimization. This control system is used the rotor speed deviation as a feedback signal. Furthermore, the using performance system of the proposed controller is compared with the system performance using conventional one (PID controller) through simulation studies. Digital simulation has been carried out in order to validate the effectiveness proposed NN-MPC power system stabilizer for achieving excellent performance. The results demonstrate that the effectiveness and superiority of the proposed controller in terms of fast response and small settling time.

STATCOM Stabilizer based on Fuzzy Logic Control for Damping Power Oscillation

Problem statement: In power systems, there exists a continuous challenge to improve dynamic performance of power system. Approach: Static Synchronous Compensator (STATCOM) is a power electronic based device that has the capability of controlling the power flow through a line. This study applies the Static Synchronous Compensator (STATCOM) to control the power flow during dynamic period. To verify the effect of the STATCOM on dynamic performance, the mathematical model and control strategy of a STATCOM was needed to be presented. The converters of STATCOM were represented by variable voltage source with associate transformer leakage reactance and the voltage source and the reactance were transformed into current injection. The current injection model of STATCOM was modeled into power flow equation and thus it was used to determine control strategy. This study applies the fuzzy logic control to determine the control strategy of STATCOM. The swing curves of the three phase faulted power system without and with a STATCOM was tested and compared in various cases. Results: The swing curve of the system with STATCOM based fuzzy logic control had the less amplitude during the dynamic period. Conclusion: STATCOM can improve the dynamic performance of the system after disturbance.

An advanced FMRL controller for FACTS devices to enhance dynamic performance of power systems

The parameters of power system slowly change with time due to environmental effects or may change rapidly due to faults. It is preferable that the control technique in this system possesses robustness for various fault conditions and disturbances. The used flexible alternating current transmission system (FACTS) in this paper is an advanced super-conducting magnetic energy storage (ASMES). Many control techniques that use ASMES to improve power system stability have been proposed. While fuzzy controller has proven its value in some applications, the researches applying fuzzy controller with ASMES have been actively reported. However, it is sometimes very difficult to specify the rule base for some plants, when the parameters change. To solve this problem, a fuzzy model reference learning controller (FMRLC) is proposed in this paper, which investigates multi-input multi-output FMRLC for time-variant nonlinear system. This control method provides the motivation for adaptive fuzzy control, where the focus is on the automatic online synthesis and tuning of fuzzy controller parameters (i.e., using online data to continually learn the fuzzy controller that will ensure that the performance objectives are met). Simulation results show that the proposed robust controller is able to work with nonlinear and nonstationary power system (i.e., single machine-infinite bus (SMIB) system), under various fault conditions and disturbances.

Model predictive control approach based load frequency controller

The present paper investigates the design of Load-Frequency Control ( LFC) system for improving power system dynamic performance over a wide range of operating conditions based on model predtictive...

Optimal Control Design of Static Synchronous Series Compensator for Damping Power System Oscillation

Problem statement: In power systems, there exists a continuous challenge to improve dynamic performance of power system. Approach: The Static Synchronous Series Compensator (SSSC) is a power electronic based device that has capability of controlling the power flow through the line both in steady state and dynamic sate. This study applied the SSSC to damp power system oscillation. The optimal control design is applied to derive the control strategy of SSSC. The simulation results are tested on a Single Machine Infinite bus. The proposed method is equipped in sample system with disturbance. The generator rotor angle curve of the system without and with a SSSC is plotted and compared. Results: It was found that the system without a SSSC has high variation whereas that of the system with a SSSC has much smaller variation. Conclusion: From the simulation results, the SSSC can damp power system oscillation.

Neural predictive controller of a two-area load frequency control for interconnected power system

The present paper investigates the load-frequency control (LFC) for improving power system dynamic performance over a wide range of operating conditions. This study proposed design and application of the neural network model predictive controller (NN-MPC) on two-area load frequency power systems. Neural network model predictive control (NN-MPC) combines reliable prediction of neural network with excellent performance of model predictive control using nonlinear Levenberg–Marquardt optimization. The controller used the local power area error deviation as a feedback signal. To validate the effectiveness of the proposed controller, two-area power system is simulated over a wide range of operating conditions and system parameters change. Further, the performance of the proposed controller is compared with a fuzzy logic controller (FLC) through simulation studies. Obtained results demonstrate the effectiveness and superiority of the proposed approach.

Coordination of PSS and TCSC controller using modified particle swarm optimization algorithm to improve power system dynamic performance

This paper develops a modified optimization procedure for coordination of a power system stabilizer (PSS) and a thyristor controlled series compensator (TCSC) controller to enhance the power system small signal stability. The new approach employs eigenvalue-based and time-domain simulation based objective functions simultaneously to improve the optimization convergence rate. A modified particle swarm optimization (MPSO) algorithm is used as the optimization algorithm. The results of simulations and eigenvalue analysis for a single machine infinite bus (SMIB) system equipped with the proposed PSS and TCSC controllers confirm that the new approach is effective in enhancing the system stability.

Creational Object-Oriented Design Pattern Applied to the Development of Software Tools for Electric Power Systems Dynamic Simulations

The development of software for dynamic simulation of electrical power systems requires a comprehensive range of complex studies, which encompasses many areas of electrical engineering as well as software engineering. This study aims at to develop an efficient strategy applied to the development of software tools for dynamic power systems simulations studies. The proposed strategy is based on the object-oriented creational pattern. This approach has the advantage of makes easy the application development process, by performing a mapping between block diagram model representation and the corresponding specialized classes. Firstly, a conceptual mapping between block diagram and the object-oriented paradigm, based on the Factory Method, is carried out. After that, some flexible strategies are presented in order to obtain an improved efficiency for the numerical routines, based on the Builder standard. This allows for the parameterization of the selected numerical integration techniques. The proposed strategy was evaluated by using a 4-generator multi-machine power system. The simulation results shown that the proposed strategy was able to provides a good power system dynamic performance.

Power systems (review of "Power System Dynamics--Stability and Control" by Machowski, J. et al; 2008) [Book reviews

This is a good introductory textbook on the subject of power system dynamic performance and control, and I would recommend it to both students of power system dynamics and practicing engineers. It is well written with a good balance between mathematical rigger and physically insightful discussions. The book provides a good broad coverage of dynamics, stability and control of power systems covering all the major issues such as voltage stability, angular stability, frequency stability and control, and modeling of power systems and their components.

A self-tuning fuzzy PI controller for TCSC to improve power system stability

In this paper, a self-tuning fuzzy PI controller (STFPIC) is proposed for thyristor-controlled series capacitor (TCSC) to improve power system dynamic performance. In a STFPIC controller, the output-scaling factor is adjusted on-line by an updating factor ( α). The value of α is determined from a fuzzy rule-base defined on error ( e) and change of error (Δ e) of the controlled variable. The proposed self-tuning controller is designed using a very simple control rule-base and the most natural and unbiased membership functions (MFs) (symmetric triangles with equal base and 50% overlap with neighboring MFs). The comparative performances of the proposed STFPIC and the standard fuzzy PI controller (FPIC) have been investigated on two multi-machine power systems (namely, 4 machine, 2 area system and 10 machine 39 bus system) through detailed non-linear simulation studies using MATLAB/SIMULINK. From the simulation studies it has been found out that for damping oscillations, the performance of the proposed STFPIC is better than that obtained by the standard FPIC. Moreover, the proposed STFPIC as well as the FPIC have been found to be quite effective in damping oscillations over a wide range of operating conditions and are quite effective in enhancing the power carrying capability of the power system significantly.

Improving power system dynamic performance using wide-area high-voltage direct current damping control

A systematic methodology for placement and integration of wide-area measurements in high-voltage direct current (HVDC) damping modulation is developed for large-scale AC/DC power system. A concept observed centre of inertia (OCOI) of power grid is described. For an interconnected AC/DC power network, the frequency difference between the OCOI of the sub-grids can be used as the input signal for HVDC modulation control when the DC link connects two regional power grids. This input contains more useful information of the interarea oscillation modes than the conventionally used signals. In addition, it takes into account the realistic situation of a large-scale power grid. Simulation results for the wide-area control based on the China Southern Power Grid data justify the feasibility and advantage of the phasor measurement unit application in HVDC modulation and power system stability control.

Coordinated Control of EPT and Generator Excitation System for Multidouble-Circuit Transmission-Lines System

A new optimal coordinated control strategy between an electronic power transformer (EPT) and generator excitation is proposed to improve power system dynamic performance and stability. The studied system is based on a single-machine multidouble-circuit transmission-lines (SMTL) system. In the SMTL system, the generator is connected to an infinite bus through a conventional power transformer with a double-circuit transmission line, and to another infinite bus with an EPT with a double-circuit transmission line. The mathematical model of the SMTL system is established, and the proposed optimal coordinated control strategy is upon linear optimal control theory. Numerical simulations were carried out for the SMTL system, and the simulation results showed that the proposed control strategy has good dynamical performance for a variety of disturbances, and can improve the system damping and voltage performance effectively.

Improvement of transient stability by unified power flow controller based on Hamiltonian system theory

AbstractIn this paper we propose a novel Hamiltonian theory based controller design methodology for unified power flow controller (UPFC) control to improve the dynamic performance of power systems. The Hamiltonian theory of the differential‐algebraic (DA) system is described and a simple control strategy is deduced to stabilize the system. Furthermore, the influence of the control law on the stability region of the system is discussed as well. It can be proved that the stability region of the system can indeed be enlarged under the control strategy. The UPFC control scheme of multi‐machine power system is developed, and a classical three‐generator system is used to validate the effectiveness of the control law. Copyright © 2007 John Wiley & Sons, Ltd.

Dynamic model for power systems with multiple FACTS controllers

Computer simulation and analysis of power systems are necessary for both planning and operation. This requires an appropriate mathematical model of the system that includes many inter-related linear/nonlinear differential and algebraic equations. Such mathematical model is also needed for the design of globally coordinated controllers to improve power system dynamic performance and stability. This paper presents a procedure for finding comprehensive dynamic models of power systems fitted with shunt and/or series connected FACTS controllers such as STATCOM, SSSC, and UPFC. In this procedure, individual components of a power system are modeled using appropriate frame of references. Then all related equations are transformed to a common network frame of reference and tied to each other through the Y-matrix of the transmission network. The procedure is tested on the Western System Coordinating Council (WSCC) test system including FACTS controllers by performing computer simulations of the system for three-phase short circuit faults. MATLAB/Simulink software package is used for the simulations.

Fault Current Contribution From Synchronous Machine and Inverter Based Distributed Generators

There are advantages of installing distributed generation (DG) in distribution systems: for example, improving reliability, mitigating voltage sags, unloading subtransmission and transmission system, and sometimes utilizing renewables. All of these factors have resulted in an increase in the use of DGs. However, the increase of fault currents in power systems is a consequence of the appearance of new generation sources. Some operating and planning limitations may be imposed by the resulting fault currents. This paper discusses a model of inverter based DGs which can be used to analyze the dynamic performance of power systems in the presence of DGs. In a style similar to protective relaying analysis, three-dimensional plots are used to depict the behavior of system reactance (X) and resistance (R) versus time. These plots depict operating parameters in relation to zones of protection, and this information is useful for the coordination of protection systems in the presence of DG