Real-Time Device-Level Transient Electrothermal Model for Modular Multilevel Converter on FPGA

Abstract

Real-time simulation of modular multilevel converters (MMCs) is challenging due to their complex structure consisting of a large number of submodules (SMs). In the literature, the computational speed is emphasized for MMC modeling in real-time simulation, while accurate and detailed information of insulated-gate bipolar transistor (IGBT) modules in SMs is sacrificed. A novel datasheet-based device-level electrothermal model for an MMC on the field programmable gate array (FPGA) is presented in this paper for real-time hardware emulation. Conduction and switching power losses, junction temperatures, temperature-dependent electrical parameters, and linearized switching transient waveforms of IGBT modules are adequately captured in the proposed model. Simultaneously the system-level behavior of the MMC is accurately modeled. Five-level and nine-level MMC systems are emulated in the hardware with the time step of 10 $\bm {\mu }\text{s}$ and 10 $\text{ns}$ for system-level and device-level computations, respectively. The paralleled and pipelined hardware design using IEEE 32-bit floating point number precision runs on Xilinx Virtex-7 XC7VX485T device. The emulated real-time results by an oscilloscope have been validated by offline simulation on SaberRD software.