Analysis of Reverse Active Power for Grid-Forming Converters During Fault Ride-Through

This paper investigates the phenomenon of reverse active power in grid-forming voltage source converters during grid voltage recovery events. The study demonstrates that this issue originates from two primary aspects: the operating point during the fault steady state and the control dynamics. The operating point analysis reveals that maintaining a certain level of active power transmission during the fault steady state is necessary to keep the operating point within the positive-power region; otherwise, the operating point may shift into the negativepower region. Furthermore, the control dynamics cause the phase angle of the modulation voltage vector to rotate clockwise, which reduces the power angle and exacerbates the power reversal issue. Theoretical findings are validated through both simulation and experimental results.