基于无网压传感器控制的单相并网逆变器预同步控制策略

Pre⁃Synchronization Control Strategy for Single⁃Phase Grid⁃Connected Inverters Based on Non⁃Grid Voltage Sensors

针对无网压传感器控制在换流器与电网同步瞬间,可能导致冲击电流过大进而并网失败的问题,提出一种预同步控制策略,在保证跟网型变流器在弱电网下稳定性的前提下,实现基于无网压传感器控制的单相并网逆变器与电网平滑可靠并网。该控制策略通过对开关管施加占空比满足一定约束条件的周期性脉冲,使换流器作为逆变器连接到交流电网之前以单位功率因数运行在整流模式。因此,交流电网的初始相位可通过采样电流来估计,其中电流相位可通过锁相环(Phase⁃Locked Loop,PLL)获取。所提控制器策略无需采集公共耦合点(Point of Common Coupling,PCC)电压,即可实现换流器与电网平滑可靠并网。最后通过半实物实验测试,验证了所提控制策略的有效性。

Aiming at the problem that the non⁃grid voltage sensor control may lead to excessive inrush current and grid connection failure at the instant of synchronization between the converter and the grid,this paper proposes,a pre⁃synchronization control strategy to ensure the stability of the grid⁃following type of converter under a weak grid in order to achieve smooth and reliable grid connection of a single⁃phase grid⁃connected inverter based on the non⁃grid voltage sensor control.The proposed control strategy applies periodic pulses that satisfy certain constraints on the duty cycle of the switching tube,so that the converter can operate in rectification mode at a unit power factor before being connected to the AC grid as an inverter.Therefore,the initial phase of the AC grid can be estimated by sampling current,and the current phase can be acquired through a phase⁃locked loop(PLL).The proposed controller strategy can achieve smooth and reliable grid connection between the converter and the grid without requiring the acquisition of the point of common coupling(PCC)point voltage.Finally,the effectiveness of the proposed control strategy is verified by semi⁃physical experimental tests.