Asymmetrical Voltage Support Control of Three- Phase Four-Wire Inverters with Zero Active Power Oscillation during Grid Faults

Supporting the grid voltage and suppressing the active power oscillation have recently become two major requirements for high penetration of distributed generations during asymmetrical faults. But they are rarely considered in the low-voltage microgrid including zero sequence voltage and current components. Therefore, this paper proposes an optimal voltage support control without active power oscillation in the four-wire inverter system, which also satisfies the constraints of maximum allowable peak current. Both the increase of positive sequence voltage, and the decrease of negative and zero sequence voltage can be well realized and optimized through the equivalent grid impedance. Then, the sum of zero sequence active power oscillation and the related oscillations caused by positive and negative sequence coupling is guaranteed to be zero. Finally, the validity of the proposed method is verified by the simulation and experimental results.