基于改进DSOGI-FLL的并网变流器多谐振解耦网络同步方法

电网电压基频正序分量相位和幅值的准确检测是三相并网变流器稳定运行的重要保证。针对传统单同步旋转坐标系锁相环在畸变或不平衡电网下锁相精度低的问题,文中利用双二阶广义积分器锁频环(DSOGI-FLL)设计了一种多谐振解耦网络的电网同步方法。首先,分析了二阶广义积分器锁频环自适应提取电网电压基波和频率的原理;其次,详细分析了不平衡电网下DSOGIFLL的锁频响应特性,提出将负序电压分量考虑在内的增益标准化线性模型,以提升其在不平衡电网下的锁频性能;然后,设计了以DSOGI-FLL为基础的多二阶广义积分器谐振解耦网络,实现畸变及不平衡电网下基波电压信息的准确获取。仿真与实验表明,该方法在电网电压畸变或不平衡情况下均能准确获取电网电压基频正序分量的相位和幅值信息。

Improved DSOGI-FLL Based Synchronization Method of Multi-resonant Decoupled Network for Grid-connected Converter

The accurate detection of phase and amplitude of the fundamental grid voltage is an important guarantee for the stable operation of three-phase grid-connected converters. In order to solve the problem of poor phase locking accuracy of the conventional phase-locked loop(PLL)based on single synchronous rotating coordinate when the grid voltage is distorted or unbalanced, this paper proposes a synchronization method of multi-resonant decoupled network based on the double second-order generalized integrator frequency-locked loop(DSOGI-FLL). Firstly, the principle of SOGI-FLL extracting fundamental voltage and frequency self-adaptively is studied. Secondly, the frequency-locked response characteristics of DSOGI-FLL under unbalanced power grid are analyzed in detail. Then a gain normalized linear model considering the negative sequence voltage component is proposed to improve frequency-locked performance of DSOGI-FLL under the unbalanced power grid. Based on the DSOGI-FLL, a resonant decoupled network with multiple second-order generalized integrators is designed to realize the accurate acquisition of fundamental voltage information under the distorted and unbalanced power grid. Finally, the results of simulation and experimental examples show that the proposed method is able to accurately obtain the phase and amplitude information of the positive sequence component of fundamental grid voltage when the grid voltage is distorted or unbalanced.