电网不平衡下基于高频模型对三相VSC的研究

Research on Three-phase VSC Under Unbalanced Conditions Combined With High Frequency Model

不平衡条件下电网负序分量会通过三相电压源变流器(VSC)的常规控制策略在交直流侧产生奇、偶次谐波污染。对此问题,利用高频模型,通过分析交直流侧瞬时功率流阐明了交直流侧谐波之间的动态关系,并提出了控制的依据和目标;利用T/4延迟法精确分离了正、负序分量,并引入负载电流前馈控制,优化了传统双比例积分(PI)控制;通过研究直流侧瞬时功率平衡,将电压平方作为控制目标,更深入地反映了系统数学模型。通过样机实验及软件仿真,证明了改进的控制方法在响应时间及超调上具有优越性。

Negative sequence component will produce odd-order and even-order harmonic pollution in AC/DC side of the three-phase voltage-sourced converter（VSC） through conventional control strategy under unbalanced power grid condition.To address this issue,this paper illustrates the dynamic relationship of harmonic between AC/DC side and then puts forward gist and target of control through deep-analysis of instantaneous power flow by using high frequency model.Precise separation of positive and negative sequence component is achieved by using T/4 delaying method, in order to optimize the traditional double proportional integral （PI） control, a load current feed-forward control is introd- uced.Put voltage square as control target by studying the DC side instantaneous power balance ,this improvement can further reflect the system mathematical model.Simulation and experimental results show the superiority of the improved control strategy through response time and overshoot amount.