电网电压不平衡时光伏并网逆变器低电压穿越技术

摘要

To improve the stability of power grid with photovoltaic(PV)inverter,the operational characteristics of PV in⁃verter and how to improve the ability of low-voltage ride-through(LVRT)under unbalanced grid voltage conditions are studied. This paper adopts two vector-oriented control strategies,which respectively orientate positive-sequence and negative-sequence voltages under positive-sequence and negative-sequence synchronous coordinate transforms. Consid⁃ering that the instantaneous power of the filter inductor is not zero,the calculation of instantaneous power in the bridge arm side is adopted to eliminate the fluctuating component in the active power transmission,thus the DC bus voltage can be stabilized. Considering the inverter current safety limit,the LVRT control scheme under unbalanced grid voltage conditions is given when the inverter is operating in rated power. A simulation model of grid-connected PV systems is built in Matlab/Simulink,and the simulation results show that hardware protection apparatus is not necessary and the proposed LVRT operation can be realized under unbalanced grid voltage conditions.%为提高光伏逆变器所并电网的运行稳定性，研究了电网电压不平衡时光伏逆变器的运行特性以及提高其低电压穿越运行能力，采用了在正、负序同步坐标变换下，电网正、负序电压分别定向的矢量控制策略。考虑滤波电感上的瞬时功率不为零，需按照桥臂侧瞬时功率计算来消除有功功率传输中的波动分量，以稳定直流母线电压；考虑逆变器电流安全限值等问题，给出额定功率运行时电网电压不平衡的低电压穿越控制方案。在Mat⁃lab/Simulink中建立了光伏并网发电系统仿真模型，系统仿真结果表明，所提出的控制方案无需增加硬件保护装置，在电网电压不平衡时可实现光伏并网逆变器的低电压穿越运行。