摘要
This paper focuses on a DC/ $3\phi $ power converter combining the single-delta bridge-cell (SDBC) converter and a single-phase PWM converter via a medium-frequency transformer for voltage flicker mitigation. In this application, the converter is required to produce negative-sequence reactive power and active power in addition to positive-sequence reactive power and harmonic power. However, in conventional SDBC-based STATCOM, steady-state active power control is not possible, and furthermore, it suffers from large voltage fluctuation in the DC-capacitor voltages when low-frequency active power is controlled. On the other hand, the proposed converter is capable of controlling active power and has been confirmed to operate at 37% of the rated reactive power, demonstrating its adaptability for flicker compensation. Nevertheless, the proposed converter still faces two challenges when intended for flicker compensation operation. The relationship between the deliverable negative-sequence reactive power and active power has not been clarified in previous research. Additionally, the operation of the system during low-frequency active power control has not been analyzed. This paper attempts to solve the first problem by conducting theoretical power analysis when negative-sequence reactive power is controlled by supplying circulating current from the single-phase converter. The second problem is also addressed by presenting current reference values for low-frequency active power control and conducting circuit analysis. The validity of the control and theoretical analysis developed in this paper is experimentally verified using a 100-V, 5-kVA downscaled model.