Parallel multi-rate simulation scheme for modular multilevel converter-based high-voltage direct current with accurate simulation of high-frequency characteristics and field programmable gate array-based implementation

The real-time simulation of the modular multilevel converter-based high-voltage direct current (MMC-HVDC) transmission system has become a popular research topic. However, in order to meet the real-time performance, the real-time simulation technology will cause additional simulation errors for MMC-HVDC, especially on its frequency characteristics. Therefore, a parallel multi-rate simulation scheme for MMC-HVDC is developed in this work to ensure accurate simulation of high-frequency characteristics. Firstly, a non-error method based on converter transformer decoupling is proposed to decouple the converter and alternating current system; direct current transmission line decoupling and arm decoupling methods are used to achieve decoupling among and within converters. A multi-rate data synchronous mechanism is established by considering the differences among high-frequency characteristics caused by delayed data interaction. Secondly, the computing architectures of the primary system solver and modular multilevel converter controller are designed based on a field programmable gate array (FPGA). The real-time simulation platform for a four-terminal true bipolar MMC-HVDC is constructed based on the FPGA array. Thirdly, the factors in multi-rate simulation affecting the simulation accuracy of high-frequency characteristics are analysed. The simulator is shown to be accurate in steady and dynamic states. The authors also verify its applicability for further research on high-frequency resonance based on control experiments.