弱电网下单相并网逆变器自同步控制策略

Self-synchronizing Control Strategy of Single-phase Grid-connected Inverter in Weak Grid

传统电流控制策略中,锁相环(PLL)通过检测公共耦合点(PCC)电压,实现电网电压相位检测,为电流控制器提供相位参考。然而,在弱电网条件下,由于PCC电压随变流器输出功率波动,PLL输出相位会出现偏差,甚至诱发系统振荡。为此,针对单相并网逆变器,提出一种自同步控制策略。传统控制策略中PLL输入变量为电网电压,与之不同,此处所提方法将电流控制器的输出调制波电压分量作为PLL的输入利用电流控制器固有的滤波特性,实现自同步控制。所提控制策略无需采集PCC电压,即可实现与电网的同步,并且在弱电网下仍能保证控制系统的稳定性。最后通过半实物实验测试,验证了所提控制策略的有效性。

In the traditional current control strategy,the phase-locked loop(PLL) detects the voltage at the common coupling point(PCC) to achieve the grid voltage phase detection and provide a phase reference for the current controller.However,since the PCC voltage fluctuates with the output power of the converter under weak grid conditions,the PLL output phase will deviate and even induce system oscillations.Hence,a self-synchronizing control strategy is proposed for single-phase grid-connected inverter.Unlike the traditional control strategy,where the PLL input is the grid voltage,the proposed method takes the output modulation wave voltage component of the current controller as the input of the PLL,and uses the inherent filtering characteristics of the current controller to achieve self-synchronizing control.The proposed control strategy can achieve synchronization with the power grid without detecting the PCC point voltage,and can still ensure the stability of the control system under a weak power grid.Finally,hardware in the loop test is carried out to verify the effectiveness of the proposed control strategy.