电网电压不平衡条件下并网逆变器的改进控制

Improved control of grid-connected inverter under imbalanced voltage

针对电网电压不平衡条件下并网同步信息检测、数字采样、PWM输出等延时问题,研究一种基于预测占空比、零极点补偿控制以及正负序分量复数滤波器的综合改进方法,以此来提高并网逆变器的动态性能。本文首先引入了电网电压不平衡条件下的LCL型三相逆变器数学模型,并分析了传统控制方法下并网输出存在的主要问题;其次,通过引入预测占空比和零极点补偿控制相结合的方法来消除数字控制带来的采样延时、PWM输出延时,利用复数滤波器快速获取并网点电压正负序分量。最后,仿真分析了不平衡电网电压条件下并网逆变器输出特性,其结果表明所提方法比传统控制方法具有更高的动态特性。

In order to improve the dynamic performance of grid-connected inverter,a comprehensive improvement method based on the prediction duty cycle,zero pole compensation control and positive and negative sequence component complex filter is studied for the detection of synchronous information,digital sampling,PWM output and other time-delay problems under the condition of unbalanced power grid voltage.Firstly,the mathematical model of LCL type three-phase inverter is introduced under the condition of unbalanced grid voltage,at the same time the main problems are analyzed of the grid-connected output under the traditional control.Secondly,the sampling delay and PWM output delay caused by digital control are eliminated by introducing the method of prediction duty cycle and zero pole compensation control.Finally,the output characteristics of grid-connected inverter under unbalanced power grid voltage are analyzed by simulation.The results show that the proposed method is more real-time than the traditional control method.