SummaryIn this paper, an innovative optimized type-2 fuzzy PID power system stabilizer is proposed to enhance the stability of the power system. This stabilizer is a combination of PID controller and type-2 fuzzy set whose parameters have been optimized with Hybrid Big Bang-Big Crunch (HBB-BC) algorithm. This combination makes the stabilizer to be flexible in face of changing in operating points of the power system and also encountering to power system nonlinearities and uncertainties. The main sources of uncertainties in the power system are the uncertainties in operation conditions, power system parameters, and measurement devices. Uncertainties do not allow the stabilizer to offer its full capabilities, and hence the efforts of the stabilizer may not satisfy the expectations. In order to evaluate the performance of the proposed controller, 2 case studies under different disturbances are investigated. The obtained results show that the proposed stabilizer can suitably provide appropriate damping in oscillatory modes of the system.
KEYWORDSHybrid Big Bang-Big Crunch algorithm, interval type-2 fuzzy-PID, low-frequency oscillation, power system stabilizer, uncertainty
| INTRODUCTIONThe stability of power system plays an important role in the power system studies area. The frequency and voltage level should be kept at a suitable range, while disturbances like changing in loading condition, generation loss, or the loss of tie lines are occurred. Low-frequency oscillations (LFO) are in the range of 0.1 and 3.0 Hz that can be divided into local and inter-area oscillations. 1 If these oscillations continue, the ability of tie lines for transmitting electrical energy will be reduced, and the power system may experience instability. These oscillations usually occur during or after a system disturbance. Therefore, it is essential to use control methods in order to eliminate these LFO. In order to enhance the stability of the power system, a power system stabilizer (PSS) has been installed in the exciter system of the generator. 2 The power system stabilization can be established centralized or decentralized. A centralized controller has an almost perfect performance in damping oscillation phenomena if it is intelligently tuned which is often a hard task. In addition, such a controller needs safe communication channels to transmit data. However, the delay in the communication system is an inevitable issue. This time delay may cause deterioration on oscillation damping and even result to an unstable power system. 3 One way to solve this problem is the use of predictive control. In this method, the model identification