功率前馈的三相光伏并网逆变器模型预测控制

MODEL PREDICTIVE CONTROL FOR THREE-PHASE GRID-CONNECTED INVERTERS BASED ON POWER FEED-FORWARD CONTROL

为加快光伏并网系统的动态响应速度、减小并网电流总谐波畸变率,针对单级式三相光伏并网逆变器的特点,在αβ静止坐标系下提出一种功率前馈的两步模型预测并网控制方法。该方法在传统电压外环中引入光伏阵列输出功率前馈作为电流内环的参考值,使内环电流参考值中包含输入功率信息。考虑到一步预测存在计算延时问题,采用两步预测控制补偿延时。在Matlab中搭建系统仿真模型,并与未采用功率前馈、采用一步预测及传统PI控制方法进行对比分析。仿真结果表明:当外界条件发生变化时,采用功率前馈的模型预测控制可以加快系统的动态响应,快速的追踪光伏阵列的最大输出功率点。与采用传统PI控制相比,电流总谐波畸变率变小。

According to the characteristics of single-stage three-phase photovohaic grid connected inverter, a two step model predictive control method is proposed to speed up the dynamic response speed and reduce the total harmonic distortion. In this method, the output power of the PV array is introduced into the traditional voltage outer loop as the reference value of the current inner loop. Two step predictive control is adapted to solve the problem of computing delay in one step prediction. The simulation model of the system is established by using the MATLAB/Simulink simulation software, and the results are compared with the one without power feed forward, one step prediction and the traditional PI control method. The simulation results showed that the model predictive control with power feed forward can accelerate the dynamic response of the system and quickly track the maximum power point of the PV array when the external conditions change. Compared with the traditional PI control, the total harmonic distortion of the current becomes smaller.