星型链式STATCOM闭环负序注入法控制策略

Research on Negative Sequence Closed-loop Current Injection Control Strategy of Star Cascaded STATCOM

星型链式静止同步补偿器(STATCOM)由于拓扑简单、成本较低等突出优点,在新能源发电系统等诸多领域得以广泛应用。但因其三相换流阀电流互相耦合且缺乏一个电流控制自由度的缺点,使得其在接入侧系统电压发生不对称性故障时换流阀相间模组电容电压极易产生不均衡的现象,严重影响其运行稳定性及应用可靠性。基于星型链式STATCOM功率模组数学模型分析,首先建立时域条件下三相换流阀功率模组电容电压和换流阀输出正负序电流的关系,给出相间电容电压偏差和d,q旋转坐标轴控制系统下负序电流的相互关系,并通过拉普拉斯变换将相互关系从时域系统转换到频域系统,从而为根轨迹法设计控制参数提供理论依据。最后,分别通过稳态实验和暂态实验证明提出方法的正确性。

The star cascaded static synchronous compensator(STATCOM) is widely used in many field such as renewable energy generation system because of its simple topology and low cost.However,due to disadvantages of coupling of three-phase valve current and lack of one degree of current control freedom,the capacitance voltage between the different phases of valves will be easily unbalanced when the AC voltage of points of voltage coupling is asymmetrical,which affects the operation stability and reliability of the valves.Based on the mathematical model analysis of power modules of star cascaded STATCOM,the relationship between capacitance voltage and positive and negative sequence current of three-phase power modules under time domain is analyzed,then the relationship between capacitance voltage deviation and negative sequence current under d,q coordinate control system is given.Meanwhile the Laplace transform method is used to convert the derivative relationship from time domain to frequency domain,which provides a theoretical basis for the design of control parameters by root locus method.Finally,the proposed solution is proved to be correct by steady and transient tests respectively.