Droop-boost control for single-phase hybrid power filter

Hybrid power filter (HPF) is used as a low-cost solution to provide reactive power compensation in distribution systems. It can provide reactive power compensation with a very low operational voltage. Direct current tracking with hysteresis PWM is widely used for controlling the HPF. However, hysteresis PWM suffers from variable switching frequency and high current ripple. Droop control is able to generate reference voltage for controlling the inverter directly from the power to be transferred. With a reference voltage, carrier-based PWM can be applied to the HPF. The droop control is applied to HPF for the first time in this paper. In contrast with conventional droop control, a droop-boost combined control scheme is proposed. The power flow control characteristic of HPF is analyzed to deduce the key parameters for achieving droop-boost control. The control system and the parameter design are conducted and verified by simulation results.