弱电网下基于D分割法的逆变器PI参数设计及稳定域分析

随着新能源装机容量和渗透率的增加,电网逐渐呈现出较大等效电网阻抗的弱电网特性,此时常规强电网下设计的并网逆变器比例-积分(PI)参数往往会引起系统谐振等不稳定问题。针对弱电网下如何优化设计并网逆变器PI参数的问题,常规方法往往需要近似处理或反复试凑,而且无法结合多个性能指标进行参数整定。因此,文中基于D分割法得到了弱电网下的并网逆变器同时满足相角裕度、幅值裕度、电流环带宽和短路比等多性能指标下的PI参数稳定域,并通过图形可视化地表现出来,从而快速、准确地获取弱电网下的PI参数,避免了反复试凑。最后,得出了弱电网下的并网逆变器即使将锁相环带宽设置得很低,其PI参数也需要合理进行设计和选取才能使其稳定、高效运行的结论,并基于30 k W实验平台验证了该设计方法和结论的正确性。

Proportional-Integral Parameter Design for Inverter Based on D-Partition Method and Its Stability Region Analysis in Weak Grid

With the increase of installed capacity and penetration rate of renewable energy, the power grid gradually exhibits the characteristics of weakness with large equivalent grid impedance. Proportional-integral (PI) parameters of grid-connected inverter designed under the conventional strong grid often cause system resonance or other instability problems. To optimize the design of PI parameters for grid-connected inverter in a weak grid, the conventional method requires approximate processing or repeated trial and error, and cannot combine multiple performance indices for parameter setting. So, the stability region of PI parameters for the grid-connected inverter in a weak grid is obtained based on the D-partition method, which satisfies the multi-performance indices, such as phase margin, amplitude margin, current-loop bandwidth and short-circuit ratio, etc. And it can be visualized by graphics, so as to quickly and accurately obtain PI parameters of weak grid, avoiding repeated trial and error. Finally, it is concluded that even the bandwidth of phase-locked loop is set very low, the PI parameters of the grid-connected inverter need to be reasonably designed and selected to make the inverter operate stably and efficiently. The validity of this design method and conclusion is verified by 30 kW experimental platform.