考虑谐波耦合特性的LCC-HVDC换流站小信号建模

谐波间的耦合作用关系着系统的动态稳定性能,为在对电网换相换流器高压直流输电(line commutated converter high voltage direct current,LCC-HVDC)系统数学建模时考虑该动态耦合过程,提出了基于12脉波换流器的开关函数理论与指数傅里叶级数相结合的LCC-HVDC小信号谐波状态空间(harmonic state space,HSS)建模方法。该建模方法不仅考虑了谐波的相互耦合作用,具有较高建模精度,同时也揭示了换流站处于不同运行模式下,交/直流侧谐波通过换流站传递到直/交流侧的动态耦合机理。最后,通过PSCAD电磁暂态仿真结果与小信号模型计算结果的对比,验证了文中提出的LCC-HVDC系统小信号HSS模型的有效性及内部谐波动态分析的正确性。该研究结果还为系统稳定性评估与参数优化奠定基础。

Small Signal Modeling of LCC-HVDC Station With Consideration of Harmonic Coupling Characteristics

The coupling effect between different harmonics is closely related to the dynamic stability of the system. In the mathematical modeling of the line commutated converter high voltage direct current(LCC-HVDC) system, due to the dynamic coupling process, a small signal harmonic state space(HSS) modeling method is proposed based on the switch function theory of 12 pulse converter and the complex Fourier series is proposed, which can achieve high accuracy since it considers the interaction of harmonics. At the same time, it also reveals the dynamic coupling mechanism of harmonic transfer from AC or DC side to DC or AC side through converter station under different operating modes. Finally, through the comparison between PSCAD electromagnetic transient simulation results and small signal model calculation results, the validity of the small signal HSS model and the correctness of internal harmonic dynamic analysis of LCC-HVDC system are verified. The research results also lay a foundation for system stability evaluation and parameter optimization.