A digital control strategy based on repetitive and multi-loop control for an active voltage quality regulator

This paper presents a digital complicated control method for an active voltage quality regulator (AVQR). The scheme combines repetitive and multi-loop control, utilizing repetitive control to guarantee good steady-state performances and dual-closed-loop as well as feed-forward control to improve dynamic response. Hence, it can achieve precise control for the output voltage waveform and fast dynamic response against both source voltage and load current disturbances. This paper analyses the proposed controller in detail. The design guidelines of the controller are described. The feasibility of the proposed control method is verified experimentally on a 2kVA AVQR system. Experimental results show that the steady-state error and the THD of output voltage with a linear load and a non-linear load are both below 1%, and the dynamic response time against source voltage disturbance and load current disturbance is shorter than 2 ms, all of which confirm the good characteristics of the proposed control strategy.