不平衡和非线性负载下的逆变器控制技术研究

Research on control technology of inverter with unbalanced and nonlinear loads

针对越来越多不平衡和非线性负载严重影响电网电能质量的问题提出了一种三相四桥臂拓扑结构,应用对称分量法和旋转坐标变换建立三相四桥臂逆变器在不同坐标系下的数学模型。利用极点配置的原理设计了一种简单的PID控制器,并且结合重复控制器构成双环控制策略。重复控制能够抑制非线性负载引起的波形畸变,提高逆变器的稳态性能。PID控制的动态响应快,可以抑制系统发生大扰动时产生的超调和振荡。仿真结果表明:在三相平衡负载、三相不平衡负载以及非线性负载等多种情况下,三相四桥臂逆变器都能够保持良好的动态特性和电压输出特性。

A three-phase four-leg topology was proposed because more and more unbalanced and nonlinear loads influenced seriously the quality of power grid.Mathematical models of three-phase four-leg inverter in different reference frames were established by applying symmetrical component method and rotating coordinate transformation.A simple PID controller was designed by using principle of pole placement,the controller combined with repetitive controller constituted a double loop control strategy.The repetitive control was able to restrain waveform distortion which the nonlinear loads caused and improved steady state performance of the inverter.The dynamic response of PID control was very fast,the PID control could reduce overshooting number and oscillation when the system received the big perturbation.Simulation results show that the inverter dynamic characteristics and voltage output characteristics are good under conditions of balanced,unbalanced and nonlinear loads.