Nonlinear Power System Stabilizer Research Articles

Nonlinear Power System Stabilizer Design for Small Signal Stability Enhancement

Nonlinear Power System Stabilizer Design for Small Signal Stability Enhancement

Artificial Neural Network Control of Battery Energy Storage System to Damp-Out Inter-Area Oscillations in Power Systems

This paper proposed an ANN (Artificial Neural Network) controller to damp out inter-area oscillation of a power system using BESS (Battery Energy Storage System). The conventional lead-lag controller-based PSSs (Power System Stabilizer) have been designed using linear models usually linearized at heavy load conditions. This paper proposes a non-linear ANN based BESS controller as the ANN can emulate nonlinear dynamics. To prove the performance of this nonlinear PSS, two linear PSS are introduced at first which are linearized at the heavy load and light load conditions, respectively. It is then verified that each controller can damp out inter-area oscillations at its own condition but not satisfactorily at the other condition. Finally, an ANN controller, that learned the dynamics of these two controllers, is proposed. Case studies are performed using PSCAD/EMTDC and MATLAB. As a result, the proposed ANN PSS shows a promising robust nonlinear performance.

Power system stabilizer based on pointwise min-norm control law

This paper presents a nonlinear power system stabilizer based on a pointwise min-norm control law and a third order state space mathematical model of the synchronous generator connected through transmission lines to the power system. Commonly, the mathematical model includes transient electromotive force as a state variable that cannot be measured. Therefore, the mathematical model is transformed in a form containing all measurable variables. Furthermore, the control law for the proposed stabilizer also considers voltage regulation. The proposed algorithm has been implemented in a digital control system and its performance experimentally verified on a 83kVA synchronous generator connected to the power system. Experimental results referring to the change in voltage and mechanical power reference, for disconnection of the transmission line, three phase and two phase short circuit, and forced oscillations are presented and compared to a PSS2A stabilizer. The experimental results show better performance of the excitation system with the proposed stabilizer compared to the system with a conventional PI voltage controller and PSS2A stabilizer. Furthermore, the results show that the proposed stabilizer is robust to system changes in the case of small and large disturbances, as well as near the generator stability limit.

Design of Optimal Proportional Integral Derivative Based Power System Stabilizer Using Bat Algorithm

The design of a proportional, derivative, and integral (PID) based power system stabilizer (PSS) is carried out using the bat algorithm (BA). The design of proposed PID controller is considered with an objective function based on square error minimization to enhance the small signal stability of nonlinear power system for a wide range of operating conditions. Three benchmark power system models as single-machine infinite-bus (SMIB) power system, two-area four-machine ten-bus power system, and IEEE New England ten-machine thirty-nine-bus power system are considered to examine the effectiveness of the designed controller. The BA optimized PID based PSS (BA-PID-PSS) controller is applied to these benchmark systems, and the performance is compared with controllers reported in literature. The robustness is tested by considering eight plant conditions of each system, representing the wide range of operating conditions. It includes unlike loading conditions and system configurations to establish the superior performance with BA-PID-PSS over-the-counter controllers.

A Nonlinear Excitation Controller Design Method for Terminal Voltage Regulation and Transient Stability Enhancement

Abstract This paper proposes a cascade control method to design a nonlinear excitation controller to guarantee the terminal voltage regulation and the transient stability. Firstly, a nonlinear automatic voltage regulator (NAVR) in the inner loop is designed to control the terminal voltage exactly. Secondly, the generator model including the NAVR is transformed to be a reduced one. Subsequently, based on the reduced generator model, the nonlinear power system stabilizer in the external loop is designed to enhance the transient stability of the power systems. Furthermore, a coordination strategy is presented to improve the performances of the terminal voltage regulation in the steady state and the stability in the transient state. Finally, the proposed method is verified by numerous simulation results.

Development of an industrial non-linear robust power system stabiliser and its improved frequency-domain testing method

The modern control methods, such as linear optimal control and non-linear control, for the generator excitation systems in state space have been dramatically developed during the past few decades. However, the lack of frequency-domain testing methods baffles the engineering applications of the modern controllers. In this study, a practical parameter configuration method as well as its frequency-domain testing method is proposed for the industrial non-linear robust power system stabiliser (industrial NR-PSS) for large synchronous generators. Furthermore, a two-machine, infinite-bus system is used to verify the effectiveness of the proposed method and the comprehensive performances of the industrial NR-PSS. A series of experiments are carried out on the real-time digital simulator to confirm its better performance comparing with the proportion integration differentiation (PID) controller and the conventional power system stabiliser (PSS). All the simulation and experimental results demonstrate that the industrial NR-PSS can improve system damping characteristic, enhance large disturbance stability and so has promising prospects in the applications to excitation systems.

Design of a non-linear power system stabiliser using the concept of the feedback linearisation based on the back-stepping technique

This study proposes a feedback linearisation based on the back-stepping method with simple implementation and unique design process to design a non-linear controller with a goal of improving both steady-state and transient stability. The proposed method is designed based on a standard third-order model of synchronous generator. A comparison based on simulation is then performed between the proposed method and two conventional control schemes (i.e. conventional power system stabiliser and direct feedback linearisation). The simulation results demonstrate that fast response, robustness, damping, steady-state and transient stability as well as voltage regulation are all achieved satisfactorily.

Non-linear power system robust stabiliser based on sliding mode technique

This paper presents a new method for designing non-linear power system stabiliser to improve transient and dynamic stability. In these studies, a 4th order non-linear model of synchronous generator has been used. First, the existence of a diffeomorphism transformation for non-linear power system has been proved and then, the non-linear model has been transformed to a canonical form using input-output linearisation method. Finally, the linearised model is controlled using sliding mode technique. At these procedures, the stability of zero dynamics has been attained. The simulation results on a single machine connected to an infinite bus confirm the feasibility and show the good performance of the stabiliser.

Design of a nonlinear power system stabilizer using synergetic control theory

Electromechanical oscillations of small magnitude and low frequency exist in the interconnected power system and often persist for long periods of time. Power system stabilizers (PSSs) are traditionally used to provide damping torque for the synchronous generators to suppress the oscillations by generating supplementary control signals for the generator excitation system. Numerous techniques have previously been proposed to design PSSs but many of them are synthesized based on a linearized model. This paper presents a nonlinear power system stabilizer based on synergetic control theory. Synergetic synthesis of the PSS is based fully on a simplified nonlinear model of the power system. The dynamic characteristics of the proposed PSS are studied in a typical single-machine infinite-bus power system and compared with the cases with a conventional PSS and without a PSS. Simulation results show the proposed PSS is robust for such nonlinear dynamic system and achieves better performance than the conventional PSS in damping oscillations.

NR-PSS (Nonlinear Robust Power System Stabilizer) for large synchronous generators and its large disturbance experiments on real time digital simulator

On the foundation of nonlinear robust control and exact generator model, this paper presents a design principle of NR-PSS (Nonlinear Robust Power System Stabilizer) for multi-machine power system, based on which an industrial NR-PSS equipment is developed. For popularizing it, the proposed parameter setting method of NR-PSS is completely the same as the widely used parameter adjustment rule of PSS. By virtue of real time digital simulator (RTDS), large disturbance experiments are carried out to compare the performances between generator excitation system equipped with NR-PSS and PSS in order to verify the correctness of design theory. The results show that compared with classical PSS, the proposed NR-PSS can dramatically improve the generator damping and attenuate the oscillation much faster, enhance the generator damping and raise both the small signal and large disturbance transient stability transmission power limit remarkably. The NR-PSS equipment with independent intellectual property right has been successfully put into operation on a 300 MW generator in Baishan Hydro Plant of Northeast China Grid more than 10 months.

Field experiments of NR-PSS for large synchronous generators on a 300MW machine in Baishan Hydro Plant

To verify the performance of NR-PSS (Nonlinear Robust Power System Stabilizer) for large synchronous generators, field experiments were carried out on a 300 MW generator in Baishan Hydro Plant of Northeast China Power Grid. The experiment results show that NR-PSS can improve the generator damping and enhance system stability remarkably.

A Normal Form Analysis Approach to Siting Power System Stabilizers (PSSs) and Assessing Power System Nonlinear Behavior

A nonlinear analysis framework based on normal form (NF) theory and center manifold reduction is proposed to determine the most effective selection of generating units to be equipped with power system stabilizers. The proposed method takes into account the nonlinear system structure and provides information on the effect of control action on nonlinear behavior and modal interaction. Based on a second-order NF representation of the system, the effect of control action on nonlinear behavior is approximated via suitable modification of the initial conditions in the nonlinear coordinate transformations which relate the physical system to the NF coordinates. On the basis of this model, nonlinear power system stabilizer (PSS) sensitivity indices are then proposed to determine the optimum sites to allocate PSS, and criteria to assess the effect of control action on linear modal interaction are developed. Examples of application of the developed approaches on a two-area four-machine test system are presented to estimate controllers' effects on system dynamic performance. The efficacy and accuracy of the method is demonstrated by comparisons to conventional analysis techniques

A Heuristic-Dynamic-Programming-Based Power System Stabilizer for a Turbogenerator in a Single-Machine Power System

Power system stabilizers (PSS) are used to generate supplementary control signals for the excitation system in order to damp the low frequency power system oscillations. To overcome the drawbacks of conventional PSS (CPSS), numerous techniques have been proposed in the literature. Based on the analysis of existing techniques, a novel design of power system stabilizer (PSS) based on heuristic dynamic programming (HDP) is proposed in this paper. HDP combining the concepts of dynamic programming and reinforcement learning is used in the design of a nonlinear optimal power system stabilizer. The proposed HDP based PSS is evaluated against the conventional power system stabilizer and indirect adaptive neurocontrol based PSS under small and large disturbances in a single machine infinite bus power system setup. Results are presented to show the effectiveness of this new technique.

Nonlinear output stabilization control for multimachine power systems

In this paper, a robust decentralized nonlinear control scheme is proposed for multimachine power system stability enhancement. The nonlinear controller consists of a novel dynamic direct feedback linearization (DFL) compensator through the excitation loop to cancel the nonlinearities and interactions among generators and a robust feedback controller to guarantee the asymptotic stability of the DFL compensated system considering the effects of dynamic output feedback and plant parametric uncertainties. The decentralized controller for each generator in the multimachine system is obtained by solving an algebraic Riccati equation. The nonlinear controller can guarantee the stability of the multimachine nonlinear power system within a whole operating region for all admissible parameters. The design procedure is tested on a three-machine power system. Simulation results show that the proposed control scheme can greatly enhance the stability of the system, regardless of the network parameters, operating points, and fault locations.

Nonlinear control of power system multi-mode oscillations

This paper presents a method to design a new nonlinear power system stabiliser (NPSS), using the nonlinear feedback transformation technique and ITAE (integration of the production of time and absolute error) rule in the optimal control theory of linear systems, to deal with the control problem of multi-mode oscillations in large-scale power systems. The design of NPSS is carried out based on a multi-machine power system model. A decoupled nonlinear control strategy is obtained for individual machines and implemented using purely feedback of local variables. Performance of the proposed nonlinear stabiliser in the multimachine power system with multi-mode oscillations is digitally simulated. The system responses controlled by the NPSS are compared with that obtained using the conventional PSS (CPSS), under different circumstances. The simulation results show that the NPSS can provide effective damping of the power system multi-mode oscillations and satisfactory control performance with good robustness.

Stabilization of a multi-machine power system using nonlinear robust variable structure control

Design of a robust nonlinear variable structure power system stabilizer which can be implemented using only local measurements is presented in this paper. The controller design procedure using a nonlinear variable transformation technique and variable structure control (VSC) theory is discussed. A method of eliminating chattering encountered in variable structure controllers is also presented. Performance of the proposed controller is evaluated by using computer simulation of a multi-machine power system which exhibits multi-modal oscillations. Results show that a significant improvement in the system performance can be obtained by the proposed control scheme.