Control of Parallel DVR with Demand-side Response under Complex Operating Conditions

As an effective scheme to deal with voltage sags, dynamic voltage regulator (DVR) has a wide range of applications in distribution networks, especially in complex conditions, which require faster dynamic response time and power supply reliability. Under the influence of load operation, the DVR based on traditional PI control has some problems, such as output power fluctuation and poor quality of output current waveform. This paper firstly conducts the control system modeling of the post-stage converter of the DVR unit accurately. According to the regulation time requirements, the PI-P double-loop control system is designed in combination with the principle of pole zero cancellation and dominant pole assignment. In order to improve the power supply reliability of the DVR, the parallel expansion strategy is further adopted. Based on the principle of master-slave control, CAN communication and interconnection lines are used to perform information exchange. Finally, complex vector modeling is adopted to analyze the stability of the parallel system, and the corresponding digital delay in the critical stable state is deduced. The proposed control strategy and theoretical analysis are verified by simulation and experiment.