Seamless self-healing control strategy for cascaded multilevel STATCOM

To improve the reliability of the cascaded multilevel STATCOM, this paper proposes a seamless self-healing scheme that can recover the STATCOM to its normal operation after the failed H-bridge units are bypassed. First the operating principle for seamless self healing is analyzed. Then based on the principle, the control strategy, including adjustment of the trigger pulses and augmentation of the output voltage in fault phase, is developed to ensure that the reactive power compensation capacity and the output voltage waveform quality is not affected by the fault. Simulation results are provided to verify the effectiveness of the proposed scheme.