The capacitor voltage full feedforward control strategy is adopted in the grid-connected inverter,which can effectively suppress the influence of grid voltage background harmonics on the grid-connected current.However,under very weak grid conditions,the phase-locked loop,digital control delay,and other factors are coupled with the grid im-pedance,resulting in poor stability of the inverter and weak passivity in the impedance crossover frequency domain,which can easily lead to system harmonic oscillation and even instability problems.Therefore,this paper reveals the dominant factors affecting the impedance characteristics of the system in each frequency band with the help of passive theory and impedance analysis method and then proposes a highly robust control strategy for grid-connected inverters based on capacitive voltage full feedforward.The theoretical analysis shows that the proposed control strategy can not only effectively widen the system output impedance stability range,but also ensure the improved system output imped-ance with high amplitude gain.Finally,the effectiveness of the proposed control strategy was verified by simulation and experiments.
关键词
弱电网/电容电压全前馈/数字控制延时/锁相环/并网逆变器/无源性理论
Key words
weak grid/capacitor voltage full feedforward/digital control delay/phase-locked loop/grid-connected in-verter/passivity theory
维普
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