含LCC-HVDC的交直流混联电网统一谐波状态估计方法

Unified Harmonic State Estimation Method for AC/DC Hybrid Power Grid with LCC-HVDC

基于电网换相换流器的高压直流(LCC-HVDC)输电系统的大量应用使交直流混联电网谐波与谐振问题日益突出。谐波状态估计是电网谐波治理的前提,但是现有研究主要着眼于交流电网,即使考虑直流系统,也仅将其视为谐波电流源,不能实现计及交直流系统间谐波相互作用的统一谐波状态估计。为此,基于广域宽频同步监测系统,首先将含LCC-HVDC的交直流混联电网视为一有机整体,建立其统一谐波状态估计模型,有效地反映交直流系统间的谐波相互耦合关系;其次,提出计及经济性、冗余度和鲁棒性的宽频同步相量测量单元综合优化配置模型及其分阶段求解方法,提高了优化配置的科学性和计算效率;再次,采用抗差最小二乘法,求解含LCC-HVDC的交直流混联电网的统一谐波状态估计值;最后,基于PSCAD/EMTDC建立了交直流混联电网仿真模型,仿真结果验证了所提方法的有效性和准确性。

The large-scale application of the line commuted converter based high voltage direct current(LCC-HVDC) transmission systems makes the harmonic and resonance problems of AC/DC hybrid power grids increasingly prominent. The harmonic state estimation is the premise of power grid harmonic management, but existing studies mainly focus on AC grids. Even if the DC system is considered, it is only regarded as a harmonic current source. And existing methods cannot achieve the unified harmonic state estimation that takes into account the harmonic interaction between AC and DC systems. Based on the wide-area broadband synchronous monitoring system, and treating the AC/DC hybrid power grid as an organic whole, a unified harmonic state estimation model for the AC/DC hybrid power grid with LCC-HVDC is developed. Then, taking into account economy,redundancy and robustness, a comprehensive model for the optimal placement of broad-band phasor measurement units(bPMUs)and its staged solution method are proposed, which significantly improve the rationality of the placement and the computational efficiency. Furthermore, the robust least squares method is used to solve the unified harmonic state estimation value of the AC/DC hybrid power grid with LCC-HVDC. Finally, a simulation model of the AC/DC hybrid power grid based on PSCAD/EMTDC is established. The simulation results verify the effectiveness and accuracy of the proposed method.