FPGA-based Modular DC Chopper Model for Real-time Simulation & HIL Tests

Voltage source converter (VSC) based high voltage DC (HVDC) systems are an effective way to connect offshore wind farms to power grids. To better resolve the issues caused by excess wind power during a grid fault, a modular DC chopper, containing hundreds of submodules, has been proposed to absorb the excess power in the VSC-HVDC system. The real-time HIL test bench is an efficient way to validate the DC chopper and its controllers. However, conventional electromagnetic transient (EMT) simulation tools have difficulties modeling the choppers of hundreds of submodules for real-time simulation. In this paper, a high-fidelity real-time model of the modular DC chopper is developed and implemented in FPGA and tested by using a real-time simulator. The modular chopper model is implemented in the field programmable gate array (FPGA) with sub-microsecond time resolution, and its small form-factor pluggable (SFP) IOs allow connection to external controllers through optical fibers and exchanging hundreds of signals in a few microseconds. The model is developed with flexibility allowing easy model scale expansion and capability of controller hardware-in-the-loop (C-HIL) testing. The DC chopper model is validated in real-time simulation along with an HVDC system and the real-time HIL test results are provided.