基于功率前馈的光伏并网控制方法及稳定性分析

A Power Feedforward-Based Control Approach for Grid-Connection of Photovoltaic Generation and Its Stability Analysis

针对光伏并网逆变器,提出了一种基于功率前馈的电压电流双环比例积分(proportional integral,PI)控制方法,电压外环实现逆变直流侧的电压稳定,内环追踪交流侧并网电流。在并网电流指令中,引入功率前馈环节,加快系统响应速度,减少直流电压的稳态误差。根据双闭环系统的波特图和根轨迹图,分析了系统在某区域范围内的稳定性。针对功率前馈环节,仿真对比了有无功率前馈对系统性能的影响。搭建了2kW的单相光伏并网发电平台,并对系统进行了性能测试。仿真与实验结果表明:系统能长期稳定可靠运行且能快速响应外界变化,并网电流畸变率为2.8%。该系统已成功应用到光伏建筑一体化(building integrated photovoltaic,BIPV)系统中,具有较强的工程实践价值。

A kind of power feedforward-based voltage and current double loop PI control method for grid-connection inverter of photovoltaic generation is proposed. The voltage stability at DC side of the inverter is implemented by voltage outer loop and the grid-connecting current at AC side is traced by the inner loop. A power feedforward link is introduced in the grid-connecting current instructions to quicken response speed and decrease steady-state error of DC voltage. According to bode plot and root locus plot of double closed-loop system the stability of the whole control system in a certain region is analyzed. For power feedforward link, the influences of two conditions, i.e., with and without power feedforward, on the performance of the control system are compared by simulation results. A grid-connected single-phase photovoltaic generation platform with capacity of 2 kW is constructed to carry out performance testing of the control system. Results of simulation and experiments show that the proposed control system can operate stably and reliably in the long term and respond to the change from outside rapidly, and the distortion rate of grid-connecting current is 2.8%. The prototype has been applied to photovoltaic roof of building integrated photovoltaic （BIPV） system successfully.