Power quality controller based on hybrid modular multilevel converter

This paper presents a hybrid modular multilevel converter (HMMC) based power quality controller (HM-PQC) intended for medium- or high-voltage applications. HM-PQC is characterized by cascaded connection of leg inductors and power units. Modular structure makes it easily be extended to high-level, thus leading to low voltage steps and low generation of EMI problems, etc.. Comparing with the conventional star-connected cascaded H-bridge converter, HM-PQC can be controlled for improving various power quality problems in three-phase balanced or unbalanced power systems. The circuit configuration and operation principles of HMMC were presented in detail. Moreover, power quality control strategies of HM-PQC were proposed for different compensation purpose. Experimental results show that HM-PQC is suitable for comprehensive mitigating of all the power quality problems, such as reactive power compensation, harmonic suppression and negative-sequence balancing.