高压直流输电交流滤波器与交流系统最大并联阻抗的分析与计算

Computation and Analysis of Maximum Parallel Impedance between the AC Filter and AC Network in HVDC Transmission System

作为高压直流输电的重要组成部分,交流滤波器在抑制谐波和无功补偿方面发挥着巨大的作用。在滤波器的设计中需要进行性能和稳态定值计算,二者都需要得到滤波器阻抗与系统阻抗的并联阻抗最大幅值,以计算最大谐波电压畸变和滤波器元件的最大电流应力。将拉格朗日乘数法引入到滤波器阻抗与系统阻抗的并联极大值计算中,首先从理论分析的角度证明,在系统阻抗和滤波器阻抗的电阻值均不为负时,并联阻抗极大值点位于系统阻抗区域的边界线上。然后,提出目前常用的系统阻抗区域类型的并联阻抗极大值点的计算方法,并给出相应的求解公式,最后利用仿真分析法验证本文算法的有效性。对比结果表明:所提出的方法在计算精度方面有较大优势,比利用找谐振点法得到的结果更加符合实际工程的要求。

As an important part of the HVDC system, AC filter is used to suppress the harmonics and compensate the reactive power in the AC side. It is necessary to determine the maximum parallel impedance （MPI） between the AC filter and AC network in implementing the performance and steady rating computation which are two major parts in the processing design of AC filter. In fact, the MPI can also be used to calculate the maximum voltage distortion on the specific bus and the maximum current stress of AC filter. In this paper, the Lagrange multiplier method was introduced to implement the computation of the MPI. Firstly, it was proved in theory that the value of MPI must be on the boundary of the AC network impedance zoom when the resistances of the AC network and the AC filter were both non-negative. Then, the basic steps of the common utilized method, as well as the principle and solution formula of the proposed method were analyzed. Finally, the validity and effectiveness of the proposed methods were compared with the common used method by the simulation model. The comparison result shows that the presented Lagrange multiplier method has a better performance in computation accuracy and it is closer to the reality of the HVDC system.