不平衡电网电压下光伏并网逆变器功率/电流质量协调控制策略

Coordinate Control of Power and Current Quality for Grid-connected PV Inverters Under Unbalanced Grid Voltage

不平衡电网电压下系统输出功率和电流质量是光伏并网逆变器重要的性能指标。首先分析不平衡电网电压下光伏并网逆变器电流谐波产生的机理和系统输出功率波动的原因,并进行量化分析。然后提出一种静止坐标系控制策略,采用瞬时功率直接计算电流参考指令,无需锁相环和电压/电流正负序分离计算,简化了控制结构。利用加权思想实现光伏并网逆变器功率/电流质量的协调控制,提高了系统运行性能。最后进行不平衡电网电压下的仿真和实验研究,结果验证了提出方法的可行性和有效性。

Power oscillation and current quality are the important performance Index for the photovoltaic （PV） grid-connected inverter under unbalanced grid voltage. Firstly, the generation mechanism of the current harmonic and power oscillation of the PV grid-connected inverter is discussed with a quantitative analysis. Secondly, a new stationary frame control strategy is proposed. The current reference is directly generated with the instantaneous power concept, which greatly simplifies the control structure due to no need of the phase-locked loop and voltage/current positive/negative sequence extraction calculation. The coordinate control of t^ower and current quality is achieved with the weighted idea, which enhances the operation performance of the PV grid- connected inverter. Finally, the simulation and experiments are carried out under the unbalanced grid voltage. Results verify the feasibility and effectiveness of the propose method.