具有精确非线性补偿的三相光伏并网逆变器滑模变结构控制策略

A Discrete-Time Integral Sliding-Mode Controller with Nonlinearity Compensation for Three-Phase Grid-connected Photovoltaic Inverter

三相并网逆变器中,由于死区效应和开关延时带来的非线性将导致逆变器输出电压的严重失真,以致并网电流的总谐波失真增加。提出了一种新型的具有精确非线性补偿的三相光伏并网逆变器滑模变结构控制策略,以抑制并网电流谐波,并提高其动态响应速度和鲁棒性。该控制策略将d-q坐标变换下的非线性补偿实现于离散积分滑模控制中。分析了逆变器输出电压的非线性,并建立了相应的非线性效应模型。根据此新模型设计了离散积分滑模控制策略。该控制策略既实现了精确的非线性补偿,也保证了整个系统的强鲁棒控制,并在一个100 kW的三相光伏并网逆变器样机上得以证实。仿真和实验结果表明:所提控制策略实现了系统全局稳定性控制、动态响应快速、鲁棒性强以及优良的电流谐波抑制能力。

A novel control strategy was presented, which combines a discrete-time integral sliding-mode controller （DISMC） with nonlinearity compensation under d-q rotating frame for three-phase grid-connected photovoltaic inverter to suppress the current harmonics as well as improve the dynamic response and robustness. Because of the nonlinearity introduced by dead time and turn on/ off delay of three-phase grid-connected inverter, the output voltage of inverter was distorted seriously. This distortion could increase the THD of the grid current. The nonlinearity of inverter output voltage was analyzed and the model of inverter with the nonlinearity effect was estabhshed accordingly. In addition, a discrete-time integral sliding-mode controller was designed according to the new model to regulate the grid current. The novel control strategy achieves both exact nonlinearity compensation and strong robustness control of the whole system. Finally the control scheme was verified in a 100 kW three-phase grid-connected photovoltaic inverter prototype. The simulation and experimental results show that the proposed control strategy has fast dynamic response, strong robustness and good current harmonics rejection.