利用模量模型识别的VSC-HVDC输电线路纵联保护新原理

电压源换流器型高压直流(VSC-HVDC)输电控制系统复杂,故障承受能力差,线路保护装置动作正确率不高。文中提出了一种利用模量模型识别的VSC-HVDC输电线路纵联保护新原理。该原理将区外故障等效为正的电容模型,差动电流和差动电压导数相关系数为1;将区内故障等效为负的电容模型,差动电流和差动电压导数相关系数为-1。通过判别相关系数的正负,即可区分区内、区外故障。在实际运行中,VSC-HVDC输电系统多为双极运行,为降低极间电磁耦合的影响,采用了1模和0模量构成判据。理论分析和PSCAD仿真实验表明,新原理无需补偿输电线路电容电流,原理简单、易于整定,不受过渡电阻和控制特性的影响,在各种工况下均能快速可靠地区分区内、区外故障。

A Novel Pilot Protection for VSC-HVDC Transmission Lines Using Modulus Model Identification

In view of the complexity of the control system of voltage source converter based HVDC (VSC-HVDC), its insufficient fault tolerance ability, and low correct rate of line protection device,a novel pilot protection for VSC-HVDC transmission lines using the modulus model identification is proposed. According to this principle, the external fault is equivalent to a positive capacitance model, so the correlation coefficient between the differential current and differential voltage derivative is 1; while the internal fault is equivalent to a negative capacitance model, so the correlation coefficient between the differential current and differential voltage derivative is -1. So the internal faults and the external faults can be distinguished by judging whether the correlation coefficient is positive or negative. In practice, modules are used to reduce the interpole electromagnetic coupling disturbance in the VSC-HVDC bipolar system. Theoretical analysis and PSCAD simulation experiments show that the new principle, without compensating for transmission lines capacitor current, is simple, easy to implement, and is not affected by transition resistance and control characteristics, while capable of identifying internal faults and external faults reliably and rapidly.