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随着电网负荷日益复杂化,电网常出现不对称故障,而且传统静止同步补偿器(STATCOM)存在参数整定难,计算复杂的缺点,故不能很好地实现无功电流的实时补偿和装置的稳定运行。通过对不对称故障状态下逆变器直流侧电压失稳机理的分析,提出一种基于正负序矢量分别定向控制新策略。该控制策略对不对称电压电流进行矢量分解,并在正负序网络下对各电矢量分别进行定向控制,从而可以有效抑制输出谐波分量,稳定直流电压,并实现动态无功补偿。同时结合能量泄放装置实现STATCOM在故障下的不脱网运行。该控制策略简单可靠,具有高鲁棒性,易于实现;仿真和实验结果表明,采用提出的控制方法可以及时穿越不对称故障,并有效补偿系统无功,稳定直流侧电压。
As grid load becomes more and more complex, asymmetric faults often occur on the power grid. Moreover, STATCOMs have some disadvantages, such as parameter setting difficulty and computational complexity. Therefore, real-time reactive current compensation and device stability can not be achieved run. Based on the analysis of the voltage instability of the DC side of the inverter under asymmetrical fault condition, a new directional control strategy based on positive and negative sequence vectors is proposed. The control strategy of the unsymmetrical voltage and current vector decomposition, and in the positive and negative sequence network of the electrical vector were directional control, which can effectively suppress the output harmonic components, DC voltage stability, and dynamic reactive power compensation. At the same time, STATCOM can be operated under the fault in combination with energy release device. The control strategy is simple and reliable, robust and easy to implement. The simulation and experimental results show that the proposed control method can transit the asymmetrical fault in time and compensate reactive power and stabilize DC voltage effectively.