基于时频分析的超高压输电线路快速保护原理研究

发布时间：2018-10-20 13:59

【摘要】：随着我国坚强智能电网的建设,大规模新能源发电场／站大量接入输电网；高压直流输电(high voltage direct current, HVDC)逐渐增多；柔性交流输电系统(Flexible Alternating Current Transmission System, FACTS)得到广泛应用。上述输电网的发展变化对输电线继电保护的选择性、灵敏性、可靠性、速动性提出了更高要求。另一方面,快速切除超高压及特高压输电线故障,可减小短路电流所产生的较大电动力和热应力对系统设备造成的不利影响,也是增加输电线传输容量和提高系统暂态稳定的一种有效措施。因此,研究快速、可靠、灵敏动作的保护原理对于保障电力系统的安全稳定运行具有重要意义。基于此,本文对基于暂态行波的超高速保护和基于微分方程算法的快速距离保护进行研究。首先,论文应用S变换获取单频率行波的时域分布,提出考虑输电线传输函数的超高速行波纵联单元式保护。为了精确描述行波在输电线路上的传播过程及其衰减规律,依据有损均匀传输线的等效二端口网络建立故障附加网络的集总电路,推导出输电线两端初始反向行波的数学关系。利用线路两端初始反向行波的比值构造识别区内外故障的判据。故障判据从原理上克服了线路模型误差、线路参数不确定性、波速不一致性等因素产生的不利影响。利用PSCAD/EMTDC仿真数据对保护算法进行了测试,仿真结果表明保护算法能可靠识别区内外故障。其次,论文在定义视在波阻抗的基础上,分析了视在波阻抗与母线网络波阻抗和正方线路波阻抗之间的关系,提出了两种行波方向继电器。一种是基于视在波阻抗的方向继电器。依据母线网络波阻抗及正方线路波阻抗分别设置正、反方向欧姆圆,构成双欧姆圆的方向判据。系统发生故障,如果计算的视在波阻抗位于正方向欧姆圆内,判断正方向发生故障,如果视在波阻抗位于反方向欧姆圆内,判断反方向发生故障。另一种是基于视在波阻抗相角的方向继电器。由于正方向发生故障,利用初始行波计算的视在波阻抗相角大于0.5π(rad);反方向发生故障,利用初始行波计算的视在波阻抗相角接近零。依据视在波阻抗相角的大小可构成正、反方向故障判据。大量的PSCAD/EMTDC仿真实验结果表明：提出的两种方向继电器能可靠、灵敏、超高速识别正反方向故障,其性能受故障初始角、故障距离、故障电阻等因素的影响小。再次,论文提出采用希尔伯特-黄变换(hilbert-huang transform, HHT)分解微分方程算法计算结果中高频成分的距离保护方案。该方案将微分方程算法的结果构成时间序列,通过经验模态分解(empirical mode decomposition, EMD)将序列中代表高次谐波的本质模态函数(intrinsic mode function, IMF)分离出来,得到具有单调变化趋势的“残差”,然后根据“残差”计算出故障线路阻抗。仿真结果表明该方案能在线路故障后快速估算出具有较高精度的故障线路阻抗值。最后,提出了利用基波相量变化率的故障选相方法和雷击干扰识别方法。线路发生短路故障后,故障相基波电流相量变化率受衰减直流分量及工频故障分量影响,其值迅速增大,而非故障相基波电流相量变化率变化较小；如果发生接地故障,零序电流基波相量变化率受衰减直流分量及工频故障分量影响,其值也会迅速增大,否则其值在零附近波动。论文依据不同类型故障中基波电流相量变化率的特征,提出了利用基波电流相量变化率的故障选相方法。线路发生短路故障或遭受故障性雷击,附加电流分量中包含衰减周期分量以及基波故障分量,导致基波电流相量变化率大幅度变化；线路遭受非故障性雷击,附加电流分量仅包含高频雷电波,雷击后一段时间内基波电流相量变化率较小。论文依据短路故障、故障性雷击及非故障性雷击产生的附加电流分量对基波电流相量变化率的不同影响,提出了利用基波电流相量变化率识别雷击干扰的方法。PSCAD/EMTDC仿真结果验证了所提方法的有效性和可靠性。为了进一步利用动模实验或现场在线测试等方式验证保护算法是否符合继电保护的各种规范要求,论文采用浮点数字信号处理器TMS320C6748设计了保护实验装置的硬件,给出了以实时操作系统内核SYS/BIOS为核心的系统软件架构以及保护应用程序的设计方案。对关键程序及算法进行了测试。
[Abstract]:With the construction of China's strong intelligent power network, large-scale new energy transmission system/ station has a large number of access points; high voltage direct current (HVDC) is increasing gradually; flexible alternating current transmission system (FACTS) has been widely used. The development change of the above-mentioned power supply provides higher requirements for the selectivity, sensitivity, reliability and speed of relay protection of the transmission line. On the other hand, rapid removal of ultra-high voltage and ultra-high voltage transmission line faults can reduce the adverse effect of large electric power and thermal stress generated by short circuit current on the system equipment, and also an effective measure to increase transmission capacity of transmission line and improve transient stability of the system. Therefore, the research on the protection principle of fast, reliable and sensitive action is of great significance to ensure the safe and stable operation of the power system. Based on this, this paper studies fast distance protection based on transient traveling wave and fast distance protection based on differential equation algorithm. Firstly, the paper uses S-transform to acquire the time-domain distribution of single-frequency traveling wave, and puts forward the ultra-high-speed traveling wave longitudinal coupling protection for transmission function of transmission line. In order to accurately describe the propagation process of traveling wave on the transmission line and its attenuation law, the mathematical relation of initial reverse traveling wave at both ends of the transmission line is deduced according to the lumped circuit of the equivalent two-port network of lossy uniform transmission line. Based on the ratio of the initial reverse traveling wave at both ends of the line, the criterion for identifying the inside and outside faults of the identification area is constructed. The failure criterion overcomes the adverse effects of line model error, line parameter uncertainty, wave velocity inconsistency and other factors from the principle. The protection algorithm is tested with PSCAD/ EMTDC simulation data. The simulation results show that the protection algorithm can reliably identify the internal and external faults of the area. Secondly, based on wave impedance, the paper analyzes the relation between wave impedance and wave impedance of bus network, and puts forward two kinds of traveling wave directional relays. The invention relates to a directional relay based on apparent wave impedance. The positive and reverse ohmic circles are respectively set according to the wave impedance of the bus network and the wave impedance of the line, and the direction criterion of the double-ohm circle is formed. If the system fails, if the calculated apparent impedance is in the positive direction ohm circle, it is judged that the positive direction is in fault, and if the wave impedance is in the anti-direction ohmic circle, it is judged that the reverse direction is faulted. The other is based on the direction relay based on the wave impedance phase angle. Due to the fault in the positive direction, the apparent wave impedance phase angle calculated by the initial traveling wave is greater than 0.5dBc (rad); in the reverse direction, the apparent wave impedance phase angle calculated by the initial traveling wave is close to zero. According to the magnitude of the wave impedance phase angle, the positive and reverse direction fault criteria can be constructed. A large number of PSCAD/ EMTDC simulation results show that the two directional relays are reliable, sensitive, super high speed identification positive and negative faults, and their performance is affected by the factors such as initial angle, fault distance and fault resistance. Thirdly, Hilbert-Huang transform (HHT) is used to calculate the distance protection scheme of high-frequency components in the calculation results of differential equations. In this scheme, the result of the differential equation algorithm is divided into the time series, and the intrinsic mode function (IMF) representing the high sub-harmonic in the sequence is separated by empirical mode decomposition (EMD) to obtain the 鈥渞esidual鈥，

本文编号：2283386