基于改进锁相环的新能源并网逆变器预测控制

Predictive Control of New Energy Grid-tied Inverter Based on Improved Phase Locked Loop

为简化并网逆变器模型预测控制(MPC)的调谐过程,提出了一种改进的锁相环(PLL)。首先,基于有限控制集的思想提出一种改进的PLL,避免了使用比例积分(PI)控制器,简化了调谐过程。其次,通过d,q轴电压关系分析了现有基于有限控制集的PLL可能存在的稳定性问题,优化设计代价函数及其补偿相角。此外,为缩减基于有限控制集PLL的计算量,根据二分法的思想设计一种迭代搜寻算法锁出最优相角,分析对比了现有有限控制集PLL和所提PLL的迭代相角精度,并将最优相角应用于预测控制。最后,通过实验对比了常规PI-PLL和所提PLL的控制性能,结果证明所提PLL动态响应极快,且应用到预测电流控制后,并网效果良好。

In order to simplify the tuning process of model predictive control(MPC)for grid-tied inverter,an improved phase locked loop(PLL)is proposed.Firstly,based on the principle of finite control set,an improved PLL is proposed,which avoids the use of proportional integral(PI)controller and simplifies the tuning process.Secondly,the possible stability problems of existing PLL based on finite control set are analyzed through d,q axis voltage relationship,and the cost function and compensation phase angle are optimized.In addition,to reduce the calculation amount based on the finite control set PLL,an iterative search algorithm is designed according to the idea of dichotomy to lock out the optimal phase angle.The iterative phase angle accuracy of the existing finite control set PLL and the proposed PLL is analyzed and compared,and the optimal phase angle is applied to predictive control.Finally,the control performance of conventional PI PLL and the proposed PLL is compared through experiments.The results show that proposed PLL has extremely fast dynamic response,and the grid connection effect is good when applied to predictive current control.