单相光伏并网逆变器建模与控制技术研究

RESEARCH ON MODELING AND CONTROL STRATEGY FOR SINGLE-PHASE PHOTOVOLTAIC GRID-CONNECTED INVERTER

对一种由Boost和带LCL滤波器的逆变电路组成的两级式单相光伏并网逆变器进行了研究。建立了前级电路的小信号模型,不含右半平面零点,且光伏阵列工作点变化不影响除转折频率外的幅频特性,简化了控制器的设计。后级采用双电流环控制策略:将滤波电容电流作为内环反馈量,实现LCL滤波器有源阻尼,并对两种实现方法进行分析比较;外环采用带谐波补偿的准比例谐振控制,实现并网电流零稳态误差控制,具有很好的跟随性能和抗干扰性能。基于能量平衡原理,推导了电压控制器输出到直流链电压的大信号模型,将系统校正成Ⅱ型系统,并引入复合控制,消除了稳态误差,增强了系统抗干扰能力。最后用Saber进行仿真,证明了建模和控制方法的有效性。

A two-stage single-phase photovohaic grid-connected inverter has been studied, which consists of a boost DC/DC converter and a DC/AC inverter with LCL filter. The built small-signal model of pre-stage does not contain any fight-half plane zero. The amplitude-frequency characteristics except the comer frequency wouldn＇ t be affected by PV array operating point, which simplifies the controller＇ s design. A two-current-loop control strategy was used ： the filter-capacitor current as the inner-loop variable is adopted for active damping of the LCL filter, and two kinds of methods are analyzed and compared in this paper; the grid current as the outer-loop variable is adopted for achie- ving zero steady-state error by a quasi-PR ＋ HC controller, which has the high performance in both the sinusoidal reference tracking and the disturbance rejection. The large signal model from the output of voltage controller to the DC-link voltage is derived based on energy balance, then the design for PI controller about the control system is ac- complished, the control system is corrected to be typical II which can eliminate the steady error and improve the anti-disturbing ability with compound control. The simulation in Saber confirms the effectiveness of the modeling and control strategy.