电压不平衡条件下并网逆变器的直流电压控制

DC Voltage Control of Grid-Connected Inverters Under Imbalanced Voltage

电网电压不平衡时,逆变器的并网功率中含有的二倍频谐波分量使得直流电压波动,影响其稳定性和并网质量。在不平衡电网电压条件下进行逆变器直流电压动态过程及其对输出性能影响的分析,在平衡的电网电压条件下的逆变器PQ控制模型基础上引入一个负序控制环,正负序叠加控制和直流电压控制改善了逆变器的控制效果,使得直流电压和并网功率波动更小,同时直流侧电容电压波动的减小也降低了逆变器并网电流中的3次谐波分量。仿真结果验证了并网逆变器控制策略的有效性和优越性,该方法能够提高了逆变器在电网电压不平衡条件下的稳定运行能力。

In the environment of imbalanced grid voltage the second order harmonic component in the power of the grid-connected inverter makes the DC voltage fluctuated and affects both the stability of DC voltage and the grid-connected power quality. Under the imbalanced grid voltage the dynamic process of the DC voltage of the inverter and the impact of the dynamic process on output DC voltage are analyzed. Under the balanced grid voltage, based on the PQ control model of the inverter a negative sequence control loop is led in, and the superimposed fundamental positive- and negative-sequence voltage control with the DC voltage control improve the control effect of the inverter and make the fluctuation of both DC voltage and grid-connected power smaller, meanwhile the decrease of the capacitor voltage fluctuation at the DC side reduces the third-order harmonic component in the grid-connected current of the inverter. The effectiveness and superiority of the proposed control strategy for grid-connected inverter are validated by simulation results. Using the proposed method, the capability of stable operation, of the grid-connected inverter under imbalanced grid voltage can be improved.