考虑虚拟阻抗的微网逆变器改进QPCI⁃MQPR控制

Improved QPCI-MQPR control of microgrid inverter considering virtual impedance

微电网中逆变器的输出电能质量极易受不同类型的交流负载影响,日常运行中无法避免大量的非线性不平衡混合负载出现在交流负载端,其结果直接劣化逆变器输出电能质量,电压出现严重畸变及不平衡。为了确保逆变器输出侧良好的电能质量,文中提出可用于微网逆变器的一种电压不平衡和谐波抑制的综合控制方法。首先阐明导致逆变器输出侧电压畸变的原因,分析两相静止坐标系下适用于不平衡负载改进后的准比例复数积分(Quasi-Proportional Complex Integral,QPCI)控制;其次,分析适用于非线性负载下逆变器的一般谐波抑制方法,针对单个准比例谐振(Quasi-Proportional Resonant,QPR)控制的不足,采用多谐振频率(Multi-QPR,MQPR)控制。在电压电流双环控制中对电压环改进,提出一种考虑虚拟阻抗的改进QPCI-MQPR的复合控制方法,保证了负载侧优质的电能质量。最后,在两相静止坐标系下对微网逆变器接入不同类型非理想负载进行仿真,其结果验证了所提控制方法的准确性、有效性。

The output power quality of inverter in the microgrid is very easy to be affected due to the influence of different types of AC loads.In daily operation,it is impossible to avoid a large number of nonlinear unbalanced mixed loads appearing at the AC load end,which directly degrades the inverter′s output power quality,and results in the serious distortion and unbalance of voltage.In order to ensure good power quality at the output side of the inverter,a comprehensive control method of voltage imbalance and harmonic suppression for microgrid inverter is proposed.The causes of voltage distortion on the output side of the inverter are clarified,and the improved quasi-proportional complex integral(QPCI)control suitable for unbalanced load in two-phase static coordinate system is analyzed.The general harmonic suppression method suitable for the inverter suffering from nonlinear load is analyzed.In allusion to the deficiency of single quasi-proportional resonance(QPR)control,the multi-QPR(MQPR)control is adopted.In the double loop control of voltage and current,the voltage loop is improved,and an improved QPCI-MQPR composite control method considering virtual impedance is proposed to ensure the high-class power quality on the load side.The simulation of microgrid inverter importing different types of non-ideal loads in two-phase static coordinate system was conducted to verify the accuracy and effectiveness of the proposed control method.