双级式光伏并网变换器的控制策略研究

摘要

文章针对双级式光伏并网前级Boost变换器,提出了一种具有功率、电压双闭环结构和基于梯度信息的变步长MPPT控制策略,它直接从光伏阵列的功率-电压特性出发,依据梯度信息直接给出最大功率点电压,进而通过电压闭环实现自动寻优,快速实现最大功率跟踪控制.针对后级含有LCL滤波器的逆变器,基于常规矢量控制技术,引入了有源阻尼控制中的电容电流反馈技术,给出了一种含有LCL滤波器的逆变器有源阻尼功率解耦控制策略,能够实现直流侧电压恒定和单位功率因数的并网控制,且在不增加系统损耗的情况下有效抑制系统谐振.建立了10 kW双级式光伏并网系统仿真模型,仿真结果表明,系统能够快速跟踪光强变化,实现MPPT控制及单位功率因数并网控制,具有良好的动态调节性能和静态特性.%In this paper,a variable step MPPT control strategy,which possesses the structure of power-voltage double closed-loop and uses gradient information,is put forward for front stage boost converter of double-stage grid-connected photovoltaic converter to achieve maximum power point tracking of PV array.The proposed strategy gets the voltage corresponding to the maximum power based on its gradient,thus achieves MPPT automatically by closed loop voltage control according to power-voltage characteristics of PV array.Based on conventional vector control strategy,the capacitor current feedback technique of active damping control is introduced,and a power decoupling control strategy with active damping for the inverter with LCL filter in back stage is given,the strategy not only achieves both constant DC-side voltage control and unity power factor control,but also suppresses resonance effectively without increasing any power losses.A 10kW simulation model of double-stage grid-connected photovoltaic power generation system is built up,simulation results show that the system can track solar irradiance changes quickly,and achieve both maximum power point tracking and unity power factor control,so that the system gets a good dynamic regulating performance and static characteristics.