微网中基于T型三电平逆变器新型双环控制策略

New Double Loop Control Strategy Based on T-type Three-level Inverter in Microgrid

针对传统的双PI控制存在电流谐波高、系统稳定性差以及响应速度慢的不足,提出一种基于Lyapu⁃nov函数的T型并网逆变器的控制策略。在分析T型逆变器数学模型的基础上,设计了电压-电流双闭环控制回路。从稳定性角度出发,结合系统的电流内环为控制基础提出了基于Lyapunov函数的非线性优化策略,从而实现对系统的谐波电流准确跟踪的目的。而电压外环仍可采用传统的PI控制方式,以有效跟踪直流电容电压,达到抑制中性点电压偏移的目的;同时,将电压外环的输出量作为电流内环的输入,可极大提高系统的抗扰性能。最后,利用仿真和硬件实验的结果来验证所提控制策略的合理性。

In view of the disadvantages of high current harmonics,poor system stability and slow response speed in the traditional double PI control,a control strategy for T-type grid-connected inverter based on the Lyapunov function was presented.On the basis of analyzing the mathematical model of T-type inverter,a voltage current double closed loop control circuit was designed.From the point of view of stability,a nonlinear control strategy based on Lyapunov function was proposed for the inner loop of current,which realized fast tracking of the harmonic current of the system.The voltage outer loop could still adopt traditional PI control to effectively track the DC capacitor voltage and achieve the purpose of suppressing the neutral point voltage offset.At the same time,using the output of the voltage outer loop as the input of the current inner loop can greatly improve the system's disturbance performance.Finally,the effectiveness and superiority of the proposed inverter control strategy were verified by the results of simulation and hardware experiments.