Hysteresis control of voltage source converters for synchronous machine emulation

Synchronous generators (SGs) are the major contributors in maintaining the stability of power systems. As SGs are displaced by electronically-coupled distributed energy resources (DERs), the dynamic behaviour of these new generation technologies will become critical in ensuring grid stability. One method of ensuring continued provision of voltage and frequency regulation is to have these new devices emulate the response of traditional SGs. Achieving the desired emulation behaviour requires fast, robust control of DERs to track the rapid changes in current injections that arise when SGs are subjecting to changing grid conditions. Hence, this paper focuses on the feasibility of controlling a voltage source converter to emulate the behaviour of a SG during both steady-state and transient periods. Two types of hysteresis current controllers (HCCs)-standard and space vector based-are considered for tracking the current injections of a virtual SG in real-time. Through simulation, it is demonstrated that both HCCs provide robust, fast tracking that enables the desired emulation, but they exhibit a wide range of variations in switching frequencies. Hence, this paper proposes a dead-time control method and demonstrates that the switching frequencies can be limited while maintaining the quality of voltages and currents that are compatible to the IEEE 1547 standard.