Whether the STATCOM can withstand the impact of grid imbalance, perform stable operation and provide effective dynamic reactive power support in the case of grid imbalance is direct embodiment of its performance.In this paper, the control method of negative sequence voltage feed forward and zero sequence voltage stability of cascade STATCOM is proposed staring from the point of the balance of suppressing negative sequence current and active power and with the use of superposition principle.The negative sequence is suppressed by way superposing negative sequence component at the port voltage of inverter.Superposition of zero sequence component in the port voltage of inverter to offset the positive sequence reactive power current and the active power due to the negative sequence component of port voltage of the inverter, thus achieving stability of the three-phase DC voltage.The method can deal with the influence of the negative sequence voltage on the device in the grid fault, avoid DC voltage instability of the device in grid fault and, at the same time, can compensate accurately dynamic reactive power.The strategy proposed in this paper finally passed Matlab/Simulink simulation test and RTDS test.%STATCOM能否承受电网不平衡的冲击,在电网不平衡时持续稳定运行并提供有效的动态无功支撑,是其性能好坏的直接体现.本文从抑制负序电流和有功功率平衡的角度出发,利用叠加原理,提出级联星接STATCOM的负序电压前馈和零序电压稳压的控制方法.通过在逆变端口电压中叠加负序分量来抑制负序电流,在逆变端口电压中叠加零序分量将正序无功电流与逆变端口电压负序分量作用产生的有功功率予以抵消,从而实现了三相直流电压的稳定.该方法可以应对电网故障时负序电压对装置的影响,避免了装置在电网故障时直流电压失稳,同时能够准确地补偿动态无功.本文所提策略最终经过Matlab/Simulink完整仿真测试及RTDS试验测试.
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