Fault-tolerant controller design for a master generation unit in an isolated hybrid wind-diesel power system
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Copyright © 2014 John Wiley & Sons, Ltd. This paper presents a methodology for designing an effective fault-tolerant controller (FTC) through the combination of three control techniques: linear parameter varying (LPV), model reference adaptive control (MRAC), and a proportional-integral-derivative (PID) controller. The proposed FTC is tested in a diesel engine generator (DEG), operating as a master generation unit in an autonomous hybrid wind-diesel power system with a battery storage system (BSS). The control objectives are to regulate voltage and frequency of the DEG and to ensure covering the demand load. Frequency regulation is achieved with the help of an MRAC-LPV scheme combining a PID controller tuned by a genetic algorithm (GA) for maintaining the speed of the diesel engine (DE) in a constant value, and in consequence the frequency of the grid. Voltage magnitude control is performed through a constrained variation of the field voltage of the synchronous generator through a classic MRAC. Different operating conditions of the hybrid power system are applied in order to test the controller's robustness: (i) steady-state operation; (ii) sudden connection of a load of 0.5 MW; (iii) a three-phase fault with duration of 0.5 s; and (iv) DE's actuator fault with six different magnitudes. An improved performance is achieved by the proposed scheme over a baseline controller, IEEE type 1 AVR for voltage regulation and a governor with PI controller for frequency regulation. Dynamic models of the microgrid components are presented, and the proposed microgrid and its FTC are implemented and tested in the Simpower Systems of MATLAB/Simulink simulation environment. The simulation results showed that the use of an LPV methodology for designing the MRAC allows the online accommodation of different fault magnitudes in the DE actuator and improves the FTC system performance in comparison with the baseline controller.