Design Method of Laboratory-Scale MMC Physical Simulation System Considering Multiharmonic Simulation Accuracy

Abstract

Besides real-time numerical simulation technology, the laboratory-scale physical simulation technology is an alternative for simulation analysis and hardware testing of modular multilevel converter (MMC). It can realize full-scale connection with complicated control and protection hardware with no need for extra interface devices, which is necessary in real-time simulation. However, due to the limitations on size and investment, the power loss rate of the MMC physical simulation system is inevitably higher than that of the real MMC project, which obviously will have a negative effect on the simulation accuracy. To solve the problem, an improved parameter design method of the MMC physical simulation system is proposed in this article. The similarity criteria of MMC with explicit expressions are first derived. On this basis, the relationship between multiharmonic simulation accuracy and power loss nonsimilarity is theoretically analyzed. Furthermore, the range of the power loss nonsimilarity is determined, which facilitates the selections of passive elements in the MMC physical simulation system with appropriate quality factors. The proposed design method can guarantee the simulation accuracy while reducing the whole system investment. Finally, the effectiveness of the proposed design method is validated by both the simulation and experimental results.