微网中双向DC-AC变流器的性能优化控制

Improvement Control of Dual-Direction DC-AC Converters for Microgrids

为解决用于直流微网与交流电网相连的双向DC-AC变流器因受到交直流双侧母线电压谐波的影响而导致的交流并网电流波形质量恶化等问题,首次推导了考虑交直流双侧电压谐波情况下的DCAC变流器交流并网电流的表达式,揭示了交直流双侧电压谐波影响的本质和特征。同时引入DC-AC变流器交流侧并网电流dq轴分量的比例-积分-双重复控制策略以抑制上述影响。进一步针对数字化系统中存在的系统采样频率与基波频率比为非整数造成重复控制器增益显著衰减的问题,提出基于对期望采样数据进行局部线性插值的重复控制器增益提升方法,以增强重复控制器对交流电网电压谐波的抑制性能。详细的仿真和实验结果证明了理论分析以及所提交流并网电流波形质量优化控制策略的正确性和有效性。

In the dual-direction DC-AC converter used to connect the DC microgrid and the AC grid,the AC voltage and DC voltage harmonics will generate lower-order harmonics in the AC grid current of the DC-AC converters. In order to tackle the problem,the grid current expression of the DC-AC converter considering the AC and DC dual side voltage harmonics is deduced for the first time and the essence and character of this effect have been revealed. The proportional-integral-dual repetitive control strategy is introduced into the d and q axis of the grid current to control the grid current of the DC-AC converter. Furthermore,aiming at the problem that the nonintegral ratio of the sampling and fundamental frequencies in the digital system will decay the gain of the repetitive controller,a gain enhancement approach for the repetitive controller with the desirable sampling point linear interpolation algorithm is proposed to improve the performance of the repetitive control in terms of cancelling the grid voltage harmonics. Detailed simulation and experimental results validate the accuracy and validity of the theoretical analysis and the improvement scheme of the AC grid current waveform quality of the DC-AC converter.