基于虚拟三相算法的微网三相逆变器控制

Control of Micro-Grid Three-Phase Inverter Based on Virtual Three-Phase Algo-Rithm

针对微电网中非隔离型三电平三相三桥臂逆变器采用传统矢量控制时并网电流总谐波畸变(total harmonicdistortion, THD)和离网时输出电压THD较高、微网缺相故障时无法运行的问题,提出了基于虚拟三相算法的微电网三相逆变器控制。该控制采用基于一阶惯性环节的虚拟三相算法,对逆变器控制所需的电压、电流每一相采样值构造成虚拟的三相对称矢量,并使用所得的虚拟三相矢量进行矢量控制。该控制将逆变器的三相控制分解成为独立的三个单相控制,可在微网缺相时正常运行,基于虚拟三相矢量每个单相控制可实现矢量控制并获得矢量控制带来的高控制精度和快速响应速度,从而减小逆变器并网/离网运行模式时输出电流/电压的THD。采用MATLAB/Simulink数字仿真软件进行了该控制方法实际效果的仿真试验,结果验证了该控制方法的有效性。

Mirco-grid non-isolated three-level three-phase three-leg inverter based on the traditional vector control has poor output current total harmonic distortion(THD)in grid-connected mode,poor output voltage THD in islanded mode and cannot work well in the micro-grid open-phase fault.Aiming at these problems,a control method based on the virtual three-phase was proposed for the micro-grid three-phase inverter.Virtual three-phase algorithm based on the first order inertia element was introduced in the proposed control.Each sampling phase voltage or phase current was built as the virtual three-phase symmetrical vector,which was used for the vector control of the inverter.With the proposed control,three-phase control of the inverter was resolved into the three independent single-phase control,to guarantee the inverter's normal operation during the micro-grid open-phase fault.Based on the virtual three-phase vectors,the single phase control achieved vector control,and then shared the high control accuracy and fast response speed,which reduced the output current THD or the output voltage THD of inverter in grid-connected mode or islanded mode.The simulated system was validated through simulation study carried out by using software interface(MATLAB/SIMULINK).The obtained results demonstrate the effectiveness of the proposed control algorithm.