不平衡非线性负载下分布式供电逆变器的控制

Control of Distributed Power Inverter with Unbalanced and Nonlinear Loads

分布式供电系统中的逆变器需要为各种不同的负载提供优质电能。文中针对不平衡和非线性负载提出了三相四桥臂拓扑结构及其极点配置比例—积分—微分(PID)控制。应用开关周期平均法和旋转坐标变换建立连续定常系统模型,根据三相四桥臂逆变系统的控制传递函数、期望的极点分布和性能指标,计算出合适的PID控制参数。对该系统工作于不平衡负载时输出电压的不平衡程度与非线性负载下输出电压的谐波含量进行对比分析,结果表明所提出的设计方法在不平衡负载下具有很强的控制输出电压平衡的能力,在非线性负载下能较好地抑制谐波产生,同时具有很好的动静态特性。该方法与其他控制方法相比具有原理简洁、应用方便、参数整定灵活等优点。详细的仿真和实验结果验证了该方法的正确性。

Inverters in a distributed power system are used to supply high quality power for all kinds of loads. For unbalanced and nonlinear loads, a PID controller of three-phase four-leg inverter based on the pole assignment is proposed. Firstly, the switch-cycle average method and rotating coordinates transformation are used to establish a continuous constants system model. Then the transfer function of the controller, expected pole distribution and performance indices are obtained. Based on which, a PID controller with appropriate parameters is designed. By analyzing output voltages under unbalanced loading conditions and harmonics components with nonlinear loads, it is indicated that the four-leg inverter system combined with the optimal PID controller can achieve excellent steady-state and dynamic performances. Moreover, the method is simple in theory, easy to implement and flexible. Detail simulation and experimental results validate the proposed method.