Real-Time Simulation of Hybrid Three-Level and Modular Multilevel Converter Based on Complete Equivalent Model for High Voltage Direct Current Transmission System

Real-time simulation is a crucial but complicated task for fast control prototyping of high-power converters. Detailed semiconductor device-based model simulates a large number of switching events at a small time step, which requires large computational effort and is thus challenging for real-time simulation. This paper proposes a complete equivalent model (CEM) approach for the real-time simulation of a hybrid 3-level and modular multilevel converter (H3LC). The presented CEM simplifies the detailed equivalent model (DEM) of the H3LC and facilitates the implementation of real-time simulation. A central processing unit (CPU) and field-programmable gate array (FPGA) based simulation is presented whereby the massive parallel computing power of the FPGA enables the simulation of the H3LC's three-level T-type converter and the hundreds of series-connected full-bridge submodules. The rest of the converter system, including the converter controls, the AC grid, and the measurement of the AC currents are implemented within the CPU model. The FPGA-based converter model is interfaced with the CPU model using controlled voltage sources to represent the AC- and DC-side equivalent voltages of the H3LC. The OP5700 real-time digital simulator from OPAL-RT Technologies is used to realize the CPU-FPGA real-time simulation, which is verified by the offline MATLAB/Simulink Simscape model.