An Improved Synchronverter Control for DERs under Grid Voltage Variations

Synchronverter (SV) or virtual synchronous generator (VSG) control for distributed energy resources (DERs) has been popular recently due to the emulation of synchronous generator (SG) behaviour. For the configuration of basic SV controlled DERs connected to grid, variations in grid voltage amplitude within normal range leads to transients in current. Virtual impedance implementation to VSG or SV controlled DERs has the drawbacks of partial current transients suppression, adverse effect of high virtual impedance on system stability and arbitrary design of virtual impedance. Hence, the reactive power loop (RPL) of SV control is improved in this work by incorporating the measured grid voltage rms value. Effective suppression of current transients by the improved SV control is shown through small signal analysis and it is verified by simulations. Further, the SV control with improvement to RPL is tested for grid fault conditions, and it is observed that the current during fault and the current transient after fault recovery might become large. Thus, simple changes to parameters in APL during fault conditions are proposed to keep the current within limits during fault and after fault recovery as well.