Low-voltage-ride-through (LVRT) capability of a phase-shifted-PWM STATCOM using the modular multilevel cascade converter based on single-star bridge-cells (MMCC-SSBC)

This paper has an experimental discussion on low-voltage-ride-through (LVRT) capability of a phase-shifted-PWM STATCOM using the modular multilevel cascade converter based on single-star bridge-cells (MMCC-SSBC). The cluster-balancing control, that produces a significant effect on the LVRT capability, is modeled and analyzed with focus on either low-pass filter (LPF) or moving average filter (MAF) to attenuate the 100Hz (double the line frequency) component inherent in each dc capacitor voltage. The cluster-balancing control using the MAF is better in transient performance than that using the LPF. A three-phase downscaled system rated at 150 V and 10 kVA is designed, constructed, and tested to verify the LVRT capability of the SSBC-based STATCOM under the severest single-phase, two-phase, and three-phase voltage sags with a voltage depth of 100%. Experimental waveforms show that the STATCOM continues operating stably as if no voltage sag occurred.