Power System Dynamic Stability Research Articles

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.

Online market-based rescheduling strategy to enhance power system stability

The study presents a framework for online power system dynamic stability enhancement with a new market-based rescheduling approach. The objective is to solve the online transient and oscillatory stability constrained economic power dispatch problem using a mixture of a modified particle swarm optimisation (PSO) and artificial neural network. The problem is formulated as a non-linear constrained optimisation problem, and PSO has been used as optimisation tool to search for the optimal solution within the available hyperspace. For reducing the time consumed in the computations, neural network has been used to assess power system dynamic stability. The rescheduling process based on the market participants' bids is used as a remedial action to maintain system operation sufficiently away from the limits of system stability. The goal of the approach is to minimise the additional payments arising from the rescheduling needed to enhance system dynamic stability. The critical clearing time corresponding to the critical contingency is considered as an index for transient stability, while system minimum damping of oscillation is considered as an indicator for oscillatory stability. The proposed framework is implemented on a 66-bus test system, and the results obtained are found to be satisfactory.

Japan 50-Hz Power System Dynamic Stability Analysis Based on Wide Area Measurement System Influenced by the Great Eastern Japan Earthquake

Abstract The “Eastern Japan Earthquake” March 11, 2011 at 14.46 JST (Japan Standard Time) caused serious damage at the Fukushima Daiichi nuclear power station operated by the Tokyo Electric Power Co. (TEPCO). Of course, this had an impact on the stability of power system dynamics in Japan 50-Hz power system. Therefore, it became an important issue to observe and analyze the situation. Two Phasor Measurement Units (PMUs) are installed at locations nearby the great earthquake area. One PMU located at Yokohama city and the other one at Hachinohe. The PMUs data are used which has very high time resolution (40 ms per sample) and is able to provide detailed information for observation and monitoring the power system stability dynamics and its correlation with time. Using FFT filter with Welch method-Auto Spectrum and histogram graphics based on PMUs data, this paper shows some results observing and monitoring the power stability dynamics before and after the earthquake in Japan 50-Hz power system.

Combined Design of PSS and STATCOM Controllers for Power System Stability Enhancement

In this paper a robust method is presented for the combined design of STATCOM and Power System Stabilizer (PSS) controllers in order to enhance the damping of the low frequency oscillations in power systems. The combined design problems among PSS and STATCOM internal ac and dc voltage controllers has been taken into consideration. The equations that describe the proposed system have been linearized and a Fuzzy Logic Controller (FLC) has been designed for the PSS. Then, the Particle Swarm Optimization technique (PSO) which has a strong ability to find the most optimistic results is employed to search for the optimal STATCOM controller parameters. The proposed controllers are evaluated on a single machine infinite bus power system with the STATCOM installed in the midpoint of the transmission line. The results analysis reveals that the combined design has an excellent capability in damping a power system's low frequency oscillations, and that it greatly enhances the dynamic stability of power systems. Moreover, a system performance analysis under different operating conditions and some performance indices studies show the effectiveness of the combined design.

Variable Structure Power System Stabilizer Optimized by Genetic Algorithm

In this study, an optimal variable structure power system stabilizer (VS-PSS) is proposed in order to improve dynamic stability of single machine infinite bus (SMIB) system. Model uncertainties, parameter variations, and external disturbances always exist in power systems. Therefore, variable structure control (VSC) is considered as a robust control method for designing PSS. Performance and robustness of VSC system depend on switching function and feedback gains. That's why; they are optimized via genetic algorithm (GA). The proposed VS-PSS is based on a state-space model which derived from Philps-Heffron model. It is seen that the VS-PSS improve the dynamic stability of power system better than conventional PSS according to simulation studies done under different external disturbance conditions.

Determination of SMES capacity to enhance the dynamic stability of power system

This paper proposes the principle of SMES capacity determination for power system stable operation. Adopting the energy function method, the mechanism of SMES damping power oscillation in the classical single-machine infinite-bus (SMIB) system is analyzed. The released kinetic energy during disturbance is the original of power system oscillation, which is taken as the principle of SMES capacity determination. Then, the influence of fault type, fault position, and fault clearing time on the SMES capacity determination are discussed. Using MATLAB simulation, the principle of SMES capacity determination is evaluated.

Long-term stabilisation of grid connected wind farms with FACTS controllers

The increasing power demand has led to the growth of new technologies that play an integral role in shaping the future energy market. Keeping in view of the environmental constraints, grid connected wind turbines are promising in increasing system reliability. This paper presents the impact of FACTS controllers on the long-term dynamic stability of power systems connected with wind farms based on doubly fed induction generator systems. The stability assessment is made first for a three-phase short circuit without the FACTS controllers in the power network and then with the FACTS controllers. The long-term dynamic simulation results yield information on: 1) the impact of faults and slow wind speed changes on the performance of wind driven induction generators; 2) the change in controllable parameters of the FACTS controllers following the faults and wind speed changes; 3) transient reactive power ratings of FACTS controllers for enhancement of rotor speed stability of induction generators and angle stability of synchronous generators.

Measurement-based method for wind farm power system oscillations monitoring

The global increase in the penetration of renewable energy is pushing electrical power systems into uncharted territory, especially in terms of transient and dynamic stability. In particular, the greater penetration of wind generation in European power networks is, at times, displacing a significant capacity of conventional synchronous generation with fixed-speed induction generation and now more commonly, doubly fed induction generators. The impact of such changes in the generation mix requires careful monitoring to assess the impact on transient and dynamic stability. This study presents a measurement-based method for the early detection of power system oscillations, with consideration of mode damping, in order to raise alarms and develop strategies to actively improve power system dynamic stability and security. A method is developed based on wavelet-based support vector data description (SVDD) to detect oscillation modes in wind farm output power, which may excite dynamic instabilities in the wider system. The wavelet transform is used as a filter to identify oscillations in frequency bands, whereas the SVDD method is used to extract dominant features from different scales and generate an assessment boundary according to the extracted features. Poorly damped oscillations of a large magnitude, or that are resonant, can be alarmed to the system operator, to reduce the risk of system instability. The proposed method is exemplified using measured data from a chosen wind farm site.

Design of Model-reference Discrete-time Sliding-mode Power System Stabilizer

Power system stabilizers improve the dynamic stability of power systems by increasing the damping torque of the synchronous machines in the system. Over the last four decades, various approaches for the design of power system stabilizers have been reported in the literature. The sliding-mode controller is one of these approaches that has some advantages, such as parameter insensitivity and realization simplicity, over other approaches. In this article, as a first and new approach for the design of the power system stabilizer in the literature, a model-reference discrete-time sliding-mode controller is presented. The effectiveness and the robustness of the proposed model-reference discrete-time sliding-mode controller based power system stabilizer is demonstrated by a number of studies. Simulation results show that the proposed power system stabilizer performs better for less overshoot and less settling time compared with the conventional and linear quadratic regulator based stabilizers under normal load operation and significant system parameter variation conditions.

Induction motor load impact on power system eigenvalue sensitivity analysis

Load modelling plays an important role in power system dynamic stability assessment. One of the widely used methods in assessing load model impact on system dynamic response is parametric sensitivity analysis. A composite load model-based load sensitivity analysis framework is proposed. It enables comprehensive investigation into load modelling impacts on system stability considering the dynamic interactions between load and system dynamics. The effect of the location of individual as well as patches of composite loads in the vicinity on the sensitivity of the oscillatory modes is investigated. The impact of load composition on the overall sensitivity of the load is also investigated.

Power system dynamic stability and voltage regulation enhancement using an optimal gain vector

This paper addresses a control methodology to enhance power system dynamic stability and voltage regulation by augmenting existing generator controls (conventional PSS and AVR) using an optimal static gain vector. The control design problem is reduced to finding a new control loop including a simple fixed gain vector. In order to optimal tune gain elements, the problem is formulated via an H ∞ static output feedback (H ∞-SOF) control technique, and the solution is easily found using an iterative linear matrix inequalities (ILMI) algorithm. Real-time experiments have been performed for a longitudinal four-machine infinite-bus system on the Analog Power System Simulator at the Research Laboratory of the Kyushu Electric Power Co. The proposed robust technique is shown to maintain the robust performance and minimize the effects of disturbances.

Impact of FACTS Controllers on the Dynamic Stability of Power Systems Connected with Wind Farms

The increasing power demand has led to the growth of new technologies that play an integral role in shaping the future energy market. Keeping in view of the environmental constraints, grid connected wind turbines are promising in increasing system reliability. This paper presents the impact of Flexible A.C. Transmission System (FACTS) controllers on the dynamic stability of power systems connected with wind energy conversion systems. The wind generator model considered is a variable speed doubly - fed induction generator model. The stability assessment is made first for a three phase short circuit without the FACTS controllers in the power network and then with the FACTS controllers. The dynamic simulation results yield information on (i) The impact of faults on the performance of induction generators/wind turbines. (ii) The change in controllable parameters of the FACTS controllers following the disturbance. (iii) Transient rating of the FACTS controllers for enhancement of rotor speed stability of induction generators and angle stability of synchronous generators.

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.

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.

Influence of Windfarms on Power System Dynamic and Transient Stability

The interaction between bulk windfarm generation and conventional generation and its influence on network dynamic characteristics are investigated. A simple three-generator system having characteristics that may be considered representative of the major areas of the UK network is used for the dynamic studies. Time response simulation and eigenvalue analysis are used to establish basic transient and dynamic stability characteristics. The wind generation is provided either by windfarms based on Fixed Speed Induction Generators (FSIGs) or Doubly Fed Induction Generators (DFIGs). In addition, in order to provide a base-line, against which windfarm influence on network dynamics can be judged, the case where the power is provided only by conventional synchronous generation is also considered.

動的負荷と分散型電源を考慮した電力系統の動態安定度解析

A fundamental study of power system dynamic stability analysis with dynamic load and distributed generation is presented. For this study, we use a single machine and a single load connected to an infinite bus model with voltage dependency parameters of loads. The adequacy of proposed model is demonstrated using power system stability simulations.Using proposed model, we can develop insights into various effects of dynamic loads and distributed generations to the dynamic stability analysis.

The Development and Application of a Marine Power System Simulator for Marine Engineer Training

For marine engineer training, marine power system analysis and fault diagnoses, a marine power system simulator (MPSS) is proposed here. It has been developed by applying system simulation techniques. The main techniques employed were marine power system modeling, microcomputer control, and local area network communication. Some functions and typical fault simulations produced with the MPSS are introduced. These operations are particularly useful for marine engineer training. A marine power system model is built by applying the power system dynamic stability theory. The power system model is the most important element in the simulator. The system model is made of a diesel engine generator, induction motor, power network, and so on. Many simulation results were obtained, such as starting the lubricating oil pump and a power network three-phase ground fault. Because the system offers online control, local area network communication, and human-machine interface of information, this MPSS is used extensively in marine engineer training where the standard is professional skill in marine electrical technology. The system has been used to meet the standards of the STCW78/95 international convention in many marine companies and training centers in China with good results.

Marine Power System Modeling and Simulator

For marine engineer training and marine power system fault diagnose analysis, microcomputer control and network techniques and system simulation techniques are used for building Marine Power System Simulator. With the simulator, the power system model is most important parts. A marine power system model is built by apply power system dynamic stability theory. The model is made of diesel engine generator, induction motor and power network etc. Some simulations are made. Such as power network three phases ground fault and lubricating oil pump starting simulation.

Influence of Field Mutual Leakage Reactance in Generator Model on Dynamic Behavior-Study on Sudden Short Circuit, Load Rejection and PSS Effect-

This paper describes the effect of mutual leakage reactance in rotor circuit (Canay reactance) on analysis of generator transient and dynamic behavior. The authors derived a detailed equivalent circuit model for 48P-15.75MVA generator, and analyzed sudden short circuit and load rejection phenomena of the generator by simulations using the electromagnetic transients program (ATP-EMTP), and compared the results with the experimental data. In addition to these analyses, the influence of mutual leakage reactance on analysis of power system dynamic stability was investigated.

Variable-Speed Wind Turbines with Doubly-Fed Induction Generators

Variable-speed pitch-controlled wind turbines with doubly-fed induction generators (DFIG) are modelled for power system dynamic stability. The model is explained and the parts of the model are verified. The model is implemented in the simulation tool PSS/E and created as a modular structure. This means that it is possible easily to add other control loops, as other modules, to the existing model code for ad-hoc investigations. This article is the first part of a large work dealing with investigation of dynamic interaction between the variable-speed wind turbines equipped with DFIG and the power grid.