三相光伏并网逆变器多目标优化模型预测控制

Multi-objective optimization model-predictive control of PV grid-connected inverters

三相电压型并网逆变器广泛用于光伏发电领域。逆变控制方法用于提高并网系统效率和响应质量。模型预测控制策略使用离散时间模型预测下一个采样周期所有可能的输出值,根据评估函数选取最优电压向量。将模型预测控制用于三相电压型并网逆变器中。首先,建立三相光伏逆变器在d-q坐标系下的瞬时功率数学模型。其次,设计预测函数在线预测逆变并网参数。选择合适的目标函数控制逆变器下一采样周期的输出值。d-q坐标系下的跟踪精确迅速,所提出的控制策略计算量小,无需PWM调制,更容易实现。然后,对模型预测控制进行多目标优化。设计电流解耦控制减小系统输出有功功率,改变评估函数提高输出电流质量,修正交流侧电压参数提高预测的准确性。最后,仿真和实验结果证明提出的控制策略输出电流具有良好的动态性能和较低的谐波畸变率,可快速跟踪给定的参考值,具有无功补偿的功能。

Three-phase voltage-source grid-connected inverters are widely applied in the field of photovoltaic power generation. A variety of control strategies about inverters have been proposed in order to improve performance and efficiency of grid-connected systems. Model predictive control strategy uses the discrete time model to predict all the possible output value in the next sampling period. The optimal voltage vector is chosen according to the cost function. A model predictive control strategy is used in three-phase voltage-source grid-connected inverter. Firstly, instantaneous power mathematical model of three-phase PV inverter in d-q coordinates systems is established. Secondly, predictive function is designed to predict the inverter grid parameters online. The optimal objective function is selected to control the inverter in the next cycle. The tracking in d-q coordinate system is fast and accurate. The calculation amount of proposed strategy is small. It is easy to be implemented and does not need PWM module. Then, multi-objective optimization control is designed. Current decouple control is designed to reduce reactive power of the system. Cost function is changed to improve output current quality. The AC voltages are modified to improve the prediction accuracy. Finally, simulation and experimental results show that the output current of the proposed strategy has good static performance and low harmonic distortion rate. It can track reference and realize reactive power compensation.