适用于不平衡负载工况下的微网逆变器控制策略

微网逆变器的一个重要性能是其工作在离网模式下时,在三相负载不平衡情况下仍能维持三相输出电压的对称性,为微网提供稳定的电压支撑。文中通过分析逆变器输出接不平衡负载时的系统不平衡机理,提出了一种简单有效的系统控制策略:在系统传统控制环路中引入谐振控制器,以抑制不平衡负载条件下控制环路中所存在的2倍工频脉动分量。所提出的控制策略免去常规控制中所需电压/电流正负序分离等控制环节,极大地简化了系统的控制结构。建立了新控制策略下的系统环路模型,给出了环路控制参数及谐振控制器的设计方法。仿真和实验结果验证了所提出的系统控制策略能有效抑制由不平衡负载引起的输出电压畸变,获得高质量的输出电压波形。

Control Strategy for Microgrid Inverter Under Unbalanced Load Conditions

An important characteristic of the microgrid inverter is that the three-phase output voltage remains balanced under unbalanced load conditions when operating in the off-grid mode to provide the microgrid with stable voltage support. The unbalanced mechanism of inverter under unbalanced load conditions is analyzed first. A simple and effective control strategy is proposed, in which the resonant controller is introduced into the voltage control loop to suppress the pulse signal(whose frequency is twice that of the inverter output voltage)existing in the control loop under the unbalanced load condition. The positive and negative sequence separation of voltage and current can be removed and the control structure is greatly simplified. A control loop model based on the proposed control strategy is developed, and the control loop parameters and the resonant controller design method are given. Finally, simulation and experimental results have verified the effectiveness of the proposed control strategy in suppressing the output voltage distortion caused by the unbalanced load. This work is supported by National High Technology Research and Development Program of China(863 Program)(No. 2015AA050603)and State Grid Corporation of China.