Optimized Control of VAR/Voltage in the Off-grid Hybrid Power System

Abstract

Voltage is a fundamental element in the quality of power supply, may rise/drop depending on the reactive power balance; hence, it has become extremely important to manage the reactive power balance for voltage control in the off-grid hybrid power system (OGHPS). This paper investigates the application of bacteria forging algorithm and genetic algorithm optimization algorithm to design an optimal control for voltage stability of off-grid hybrid power system. The off-grid hybrid power system considered in this work consists of an induction generator for wind power system, photovoltaic (PV) system with inverter, synchronous generator for diesel power generation, and composite load. The over-rated PV inverter has ample amount of VAR capacity while sourcing PV real power. Two control structures are incorporated in this work, to regulate load bus voltage. The first control structure is for controlling the total reactive power requirement of the system that by controlling inverter voltage magnitude for sourcing required reactive power to the system, and the second control structure is for controlling the SG excitation and hence the load bus terminal voltage. Both control structures have proportional-integral (PI) controller with a single input. In order to coordinate VAR/voltage control, the controller parameters tuned optimally and simultaneously using bacterial forging and genetic algorithm-based optimization method. Small signal model of all components of OGHPS is simulated in Simulink, tested for reactive load disturbance, and/or wind power input disturbance of different magnitudes for voltage stability. All system state variables are examined to evaluate the effectiveness of proposed optimal coordinated controls.