Research on improving the fault simulation accuracy of Modular Multilevel Converters

The digital real-time simulation-based function and dynamic performance tests of the modular multi-level converter (MMC) control and protection systems have become an important method to ensure the safety and reliability of the MMC-HVDC projects, of which the real-time simulation model of the MMC is one of the key factors affecting the test effect. Currently, the MMC models are generally implemented in the central processing unit (CPU) and field programmable gates array (FPGA) with multi-rate time steps (large-small time step simulation). In case of fault simulations, the loss of accuracy caused by communication delay between CPU and FPGA can be significant. In order to further improve the test performance, the FPGA based small time step model of MMC has been studied. Comparative simulation has been carried out under AC and DC fault conditions to verify the proposed method. The results show that the real-time simulation accuracy of the MMC can be effectively improved with the new method.