FPGA algorithm implementation of hybrid MMC harmonic injection strategy

Abstract

Capacitor submodule occupies a large volume in Modular multi-level Converter (MMC) and costs a lot of money. Harmonic injection strategy can often achieve the effect of reducing the voltage fluctuation of the sub-module capacitors. Therefore, it can reduce reduce the construction cost of the HVDC transmission system. On the basis of introducing the basic principle of hybrid MMC harmonic injection and simulation verification on PSCAD platform, this paper introduces the physical platform of four-terminal flexible power grid, including its hardware display and monitoring and testing interface, showing the diversity of real-time data acquisition methods. Finally, through the experimental research on the implementation of the hybrid MMC harmonic injection strategy by FPGA, the modulation wave, the conduction number of the sub-module, the capacitance voltage of the sub-module and other physical quantities before and after the second harmonic injection are compared and analyzed. It is verified that the second harmonic injection can change the shape of the voltage modulation wave. At the same time, the second harmonic injection can reduce the voltage fluctuation of the capacitor of the sub-module and realize the lightening from the perspective of reducing the capacitor demand.