Robust Power Sharing Control for Parallel Three-phase Inverters against Voltage Measurement Errors

In islanded microgrids, distributed generations (DGs) have been increasingly employed through parallel voltage source inverters (VSIs). To fully utilize the VSI capacity and avoid overloading, the total load power is expected to be accurately shared among VSIs based on their power ratings. However, it is revealed that even small voltage measurement scaling errors may severely deteriorate the power sharing by injecting positive- and negative-sequence circulating currents. An explicit analysis indicates that this issue cannot be avoided if the conventional voltage-feedback control is adopted with an accurate fundamental voltage tracking ability. To solve this problem, a hybrid feedback and feedforward control is proposed, which makes the power sharing robust against voltage measurement errors. In specific, the feedforward control is utilized to enhance the unbalanced and reactive power sharing by reshaping the VSI fundamental output impedance. Meanwhile, the feedback-based impedance shaping control is also employed to improve the harmonic power sharing. As no communication and sensor error knowledge are required, the proposed control scheme provides a simple but effective solution for decentralized power sharing among parallel three-phase VSIs. Finally, both simulation and experimental results are provided for verification.