Synchronous voltage controllers: Voltage-based emulation of synchronous machines for the integration of renewable energy sources

Abstract

Recently, significant attention has been paid to the integration of renewable energy sources into power systems by similar characteristics of synchronous machines (SMs). The conventional method to emulate SMs is to use power components, typically known as power-based virtual synchronous machines (PB-VSMs). This paper looks at the development of a new approach to mimic SMs using voltage components called voltage-based virtual synchronous machines (VB-VSMs). A VB-VSM is a cascaded double-loop controller with current and voltage regulation as opposed to a single-loop PB-VSM. Further, the dynamic model of an automatic voltage regulator (AVR) and a physical rotor field circuit are integrated into the controller. In addition to grid-responsive features, the VB-VSM can also eliminate an extra synchronization unit, typically a phase-locked loop (PLL), as the internal controller acts in a similar fashion to regular PLLs in research literature. Since the controller adopts voltage components for synchronization, control, and emulation purposes, it can be regarded as a synchronous voltage controller (SynVC). Extensive case studies under various conditions are carried out to demonstrate the performance of a SynVC.