负序电压前馈补偿的三相光伏逆变器不平衡单周控制策略

One-cycle Control Strategy of Three-phase PV Inverters Based on Negative Sequence Voltage Feedforward Compensation Under Unbalanced Input Voltage Conditions

鉴于电网不对称故障时有发生,提出一种基于负序电压前馈补偿的三相光伏并网逆变器不平衡单周控制策略,并设计了三相PWM逆变器不平衡单周控制系统。该控制策略对并网电流反馈量进行电网负序电压前馈补偿,可实现脉宽调制逆变器恒功率控制,大大简化了控制器的参数整定,且无需计算并网电流正、负序分量。实验结果表明,该控制策略仅使用一个传统PI控制器即可从根本上抑制电网电压不平衡时逆变器直流侧电压2次谐波和并网电流畸变,同时获得了较理想的静态特性和动态特性。

Considering frequent occurrence of grid unsymmetrical faults, an unbalanced one cycle control strategy for three-phase grid-connected photovoltaic （PV） inverters based on negative sequence components of voltage feedforward compensation is developed, and the corresponding control system is designed. The novel control strategy compensates feedback grid currents by negative sequence components of grid voltages to regulate the instantaneous active power to a constant value without any ripple, and the harmonics can be eliminated. Therefore, the parameter tuning of proportional integral （PI） controllers is simplified and the extraction of positive and negative sequence components of line currents is not required. Experimental results indicates that the proposed inverter control system adopts only one conventional PI controller to eliminate the second harmonic waves of the DC voltage and distortion of line currents under unbalanced input grid voltage conditions. As well as the control system has achieved perfect static and dynamic characteristics.