微网光伏双模式逆变器双环控制策略研究

Research on a dual-loop control strategy of dual mode inverters for photovoltaic microgrid systems

针对微网系统并网/离网运行过程中对模式平滑切换,抗外界干扰能力和系统动态响应具有较高要求的情况下,提出了双模式逆变器在电网基波频率同步旋转坐标系下的双环控制策略,建立了微网光伏逆变器并网/离网模式数学模型。系统并网时采用基于PI调节器的电压矢量跟踪电流控制策略,离网运行时采用基于SVPWM的电容电压外环电感电流内环控制策略。同时,为减小双模式切换过程产生的网络冲击,设计了并网/离网平滑切换方法。仿真结果表明,所提控制策略能够保证系统的稳定运行,同时在切换模式下,减小了电压电流冲击,实现模式平滑切换。

In view of strict requirement on smooth mode switching,anti-interference ability and demand response of system during grid-connected and off-grid operation of microgrid system,a dualloop control strategy of dual mode inverters under synchronous rotating reference frame of grid fundamental frequency was proposed,and a mathematic model of inverter grid-connected and off-grid mode in photovoltaic microgrid systems was built. When the systems are connected to power grid,voltage vector tracking current control strategy based on PI controller is adopted;in off-grid operation,an SVPWM-based dual-loop control strategy with capacitor voltage outer-loop and inductive current inner-loop was adopted in off-grid operation. To reduce grid impact of the mode switching,a smooth grid-connection and off-grid switching method was formulated. The simulation results show that the proposed control strategy can ensure operation stability of the system,reduce voltage and current impact and enable smooth mode switching.