Hybrid MMC(Hy-MMC)has broad application prospects because of the negative level output ability in its bridge arm.A Hy-MMC topology with a high-modulation ratio is designed in this paper.A second-harmonic current injec...Hybrid MMC(Hy-MMC)has broad application prospects because of the negative level output ability in its bridge arm.A Hy-MMC topology with a high-modulation ratio is designed in this paper.A second-harmonic current injection(SHCI)strategy based on Hy-MMC in high-modulation operation is also proposed to improve the power density of Hy-MMC effectively in steady-state operation.The amplitude of SHCI is determined from the perspective of the root mean square(RMS)value of bridge arm current,and the optimal initial phase angle is determined from the multi-objective optimization(capacitor voltage ripple of sub-modules(SMs),power loss,and peak value of bridge arm current).The effectiveness and engineering practicability of the proposed SHCI strategy based on Hy-MMC in high-modulation operation is verified by the electromagnetic transient(EMT)simulation using PSCAD/EMTDC®.The simulation results show that the capacitor voltage ripple of SMs can be effectively decreased by 61.98%or the capacitance can be decreased by 40%.The power loss is also analyzed.In addition,little influence of low capacitance on multi-operation conditions of Hy-MMC is verified by EMT simulation.展开更多
基金supported by National Natural Science Foundation of China(52277094).
文摘Hybrid MMC(Hy-MMC)has broad application prospects because of the negative level output ability in its bridge arm.A Hy-MMC topology with a high-modulation ratio is designed in this paper.A second-harmonic current injection(SHCI)strategy based on Hy-MMC in high-modulation operation is also proposed to improve the power density of Hy-MMC effectively in steady-state operation.The amplitude of SHCI is determined from the perspective of the root mean square(RMS)value of bridge arm current,and the optimal initial phase angle is determined from the multi-objective optimization(capacitor voltage ripple of sub-modules(SMs),power loss,and peak value of bridge arm current).The effectiveness and engineering practicability of the proposed SHCI strategy based on Hy-MMC in high-modulation operation is verified by the electromagnetic transient(EMT)simulation using PSCAD/EMTDC®.The simulation results show that the capacitor voltage ripple of SMs can be effectively decreased by 61.98%or the capacitance can be decreased by 40%.The power loss is also analyzed.In addition,little influence of low capacitance on multi-operation conditions of Hy-MMC is verified by EMT simulation.
