Research On Real-time Simulation Of MMC-HVDC Based On FPGA

The real-time simulation platform of modular multilevel converter-high voltage direct current(MMC-HVDC)based on FPGA can be used for the development of control and protection devices and the testing of physical controllers before engineering operation,whose function is of great significance.Aiming at the problems such as difficult realization,low efficiency,poor versatility and insufficient fault simulation ability of the real-time simulation of MMC-HVDC,this paper conducts research on real-time simulation of MMC-HVDC.Firstly,the Thevenin’s equivalent model of MMC arm based on FPGA is established.On the basis of the classical Thevenin’s equivalent model,it is improved and optimized from four aspects:capacitance discretization method,ideal switching element,controlled voltage source modeling and parallel total comparison sorting algorithm.And the Thevenin’s equivalent model suitable for FPGA real-time simulation is proposed.At the same time,a MMC arm simplification method suitable for steady state real-time simulation is proposed.By mapping MMC’s three phases and six bridge arms,the complexity of MMC bridge arm simulation is greatly reduced and the simulation time is shortened.Then,based on the established Thevenin’s equivalent model of the MMC arm,MMC-HVDC model was built based on the System Generator(SG)to verify rapidly by FPGA co-simulation.The simulation model of MMC-HVDC is divided into two parts:the slow system of the primary circuit and the main controller on the PC side,the fast system of the arm equivalent system and capacitor voltage control on the FPGA side.The off-line and hardwire-in-loop simulation of the four-terminal MMC-HVDC is carried out through the multi-rate simulation mode.The simulation results show that the error between FPGA real-time model and PSCAD,RT-LAB valve model is less than 2%,and it also has the ability of transient fault simulation.Finally,a real-time simulation model of MMC-HVDC based on DDRTS is established,which realizes the decoupling of the primary circuit on the PC side and the equivalent module of the bridge arm on the FPGA side,and high-speed data communication is realized through PCI-E.This simulation mode can give full play to the advantages of PC side’s high serial computing efficiency and FPGA’s parallel computing,and greatly improve the simulation efficiency of MMC-HVDC.According to the different calculation logic of PC side network solution and FPGA side arm equivalent calculation,two simulation modes of serial and parallel are proposed.The accuracy and calculation speed of the real-time simulation are verified by the platform.