Excitation Voltage Control for Emergency Frequency Regulation of Island Power Systems With Voltage-Dependent Loads

Abstract

This paper proposes a generator excitation voltage control scheme for emergency frequency regulation of island power systems with voltage-dependent loads. It is able to regulate the load voltages and their power demand to maintain stable frequency when the systems have no active power reserves. Taking an actual island power system with aluminum electrolysis loads as an example, a frequency and excitation voltage control model for the actual island power system is established. Then, by applying the output regulation theory, feedback control signals with the frequency deviations and the power imbalances are used to obtain a practical feasible control scheme whose structure is similar to that of primary and secondary frequency control. Furthermore, by taking into account the constraints of generator voltage controls and load bus voltages, two useful conditions are found to limit the power imbalances. Our control strategy can maintain the frequency and voltages in permitted ranges. Both the WSCC 9-bus system and the actual island power system are used to validate the effectiveness of the proposed scheme.