Step-by-step controller design of voltage closed-loop control for virtual synchronous generator

Virtual synchronous generator (VSG) is a control scheme applied to the inverter of a distributed generating unit in order to support power system stability by imitating the behavior of a synchronous generator. A lot of effort has been dedicated to investigating the power stage control of VSG, but the waveform quality of VSG is not fully discussed. This paper analyses a VSG with an inner voltage loop to attenuate waveform distortion influenced by dead-time effect. And main parts of the voltage loop are voltage regulator and active damping of the LCL filter. Generally speaking, the voltage regulator attenuates the influence of dead-time effect, and the active damping suppresses the resonance peak caused by the LCL filter and makes it easier to stabilize the whole system. Based on the proportional-resonant (PR) compensator together with capacitor-current-feedback active damping which is widely used for their effectiveness and simple implementations, a step-by-step design method of the controller parameters for voltage loop is proposed. By carefully dealing with the interaction between the voltage regulator and active damping, the satisfactory regions of the controller parameters for meeting the system specifications are obtained, from which the controller parameters can be easily picked out. Simulation results verify the effectiveness of inner voltage loop.