Coordinated Fuzzy Logic Control between SVC and PSS to Enhance Stability of Power Systems

Abstract

SUMMARYThis paper presents a new switching control scheme for static var compensator (SVC) using fuzzy logic control rules to enhance the overall stability of electric power systems. In addition, the coordination with power system stabilizers (PSS) is also considered to achieve a wider stable region. An SVC is set on one of the busbars in the transmission system, where the real power flow signal is utilized at the location of the SVC to determine the firing angle of the thyristor switch. The switching control scheme is simple so as not to require heavy computation on the microcomputer based switching controller. The PSSs are also set on the generators in the study system. Simulation results show the effectiveness of the proposed fuzzy logic switching control scheme for the SVC. The coordination between SVC and PSS is also effective to enlarge the stable region.

Development of a Fuzzy Rule-Based Multi-Objective Hybrid Controller for Static Synchronous Compensator

“…An alternative way is to implement different control law according to different operating conditions, i.e. to develop an event driven control strategy [4,5]. This implies that a hybrid control strategy, which is an integration of the numerical and heuristic approaches, is needed.…”

“…The voltage deviation ⌬U s , the speed deviation ⌬ o and the deviation of acceleration ⌬ o are adopted as input variables, and the variation of the control angle ⌬␦ i is used as the output variable of the controller. According to Hiyama et al [2][3][4], a point p(k) in the phase plane (as shown in Fig. 4) can give the system condition at a particular instant t = k⌬t.…”

“…In practice, the states of the power system are continuous in nature, and its multi-objective demands to Statcom exist in the whole plane; only the relative importance of different demands may vary with the specified region. Hence a smoothing approach with fuzzy regions should be adopted [3][4][5] to develop a global control strategy, and a unified Statcom controller. The final output of the fuzzy controller (i.e.…”

“…The setting of the scaling factor ␣ and D r can be optimised according to different control requirements [2][3][4]; the authors just simply apply 1.0 to ␣ and D r . Obviously, further work should be done to optimise the setting, but the proposed controller with the above simple settings does work well, as shown in the following simulation results.…”

“…As a nonlinear and variable structure system, if its operating point drifts from the specified condition as a result of continuous load changes or unpredictable major disturbances, the tuning of the controller may be not valid, and may lead to undesired and sustained oscillations in power and voltage. In this respect, to maintain a good dynamic performance over a wide range of operating conditions, different adaptive control strategies have been proposed, such as the rule-based stabiliser [2], the selftuning stabiliser, variable structure controller, and fuzzy-rule based controller [3][4][5]. Although the adaptive control strategy as well as the variable structure controller can offer much better static and dynamic performance than a fixed parameter strategy, it suffers from the fact that extended computing is needed for parameter tuning, which is undesirable for online computer control.…”