1.National Electric Power Conversion and Control Engineering Technology Research Center (Hunan University), Changsha 410082, China;2.School of Electrical and Information Engineering, Changsha University of Science & Technology, Changsha 410004, China;3.State Grid Anhui Electric Power Co. Ltd. Research Institute, Hefei 230000, China

Aiming at the low utilization rate and poor reliability of the traditional series-connected power quality control device, and the ability of the parallel-connected power quality control device to solve the voltage fluctuation problem needs to be further improved, a multi-function grid-connected converter (MF-GCC) with integrated voltage support and reactive power regulation capability is proposed. When the grid voltage fluctuates, the MF-GCC works in the series access mode to realize the voltage regulation function. When the grid voltage is normal, the MF-GCC works in the parallel access mode to achieve the unit power factor operation on the grid side. Compared with the traditional series-connected power quality control device, the MF-GCC only has one more switch and one more coupling capacitor, which can realize the effective integration of the functions of series-connected and parallel-connected power quality control device. In addition, when the system fails, the port voltage of the active part in the MF-GCC is clamped to zero and the fault current is limited. Thus the reliability of the MF-GCC itself and its connection to grid is fully improved. This paper analyzes the topology structure, working principle, control strategy and parameter design of MF-GCC in detail. Simulation and experimental results verify the effectiveness and feasibility of the proposed topology and control strategy.