混合多馈入直流作用下江苏受端电网安全稳定性评估及改善

混合馈入直流系统一般指电网换相换流器（line commutated converter，LCC）和模块化多电平换流器（modular multilevel converter，MMC）混合馈入的直流系统。目前，含有多个直流落点的混合多馈入直流系统已在受端电网规划中得到采用，但其对系统安全稳定性的影响尚未明确。为了对混合多馈入直流作用下受端电网的安全稳定性进行量化评估，首先总结了7种评估指标，并形成了一套评估方法。然后，以江苏电网为例进行了分析，说明江苏受端电网的安全稳定性不足，直流系统换相失败是最严重的问题。针对现存问题，先后提出了将彬长直流逆变侧改用MMC的方案1，以及进一步构建受端以MMC为主的多端直流系统的方案2。最后，对2种方案应用效果进行了定量评估，结果说明采用MMC换流站并构建多端直流系统将提升受端电网安全稳定性，也验证了所提评估方法的有效性。

Evaluation and Improvement of Security and Stability of Jiangsu Receiving-End Power Grid with Hybrid Multi-Infeed DC

The hybrid infeed DC system usually refers to a hybrid infeed DC system with line commutated converter (LCC) and modular multilevel converter (MMC). At present, the hybrid multi-infeed DC system with multiple DC terminal locations has been adopted in planning of receiving-end power grids, but its impact on the system security and stability is not clear. In order to quantitatively evaluate the security and stability of the receiving-end power grid with hybrid multi-infeed DC, this paper summarizes seven evaluation indexes and proposes an evaluation method. Then, a case study of Jiangsu power grid is carried out, which shows that the security and stability of Jiangsu receiving-end power grid is insufficient, and the most serious problem is the commutation failure of DC system. To solve the existing problems, two schemes are proposed: the scheme 1 is to change the inverter-side LCC of Binchang DC into MMC, and the scheme 2 is to construct a multi-terminal DC system mainly based on MMC. Finally, the application effects of two schemes are evaluated quantitatively, which shows that the security and stability of receiving-end power grid will be improved using MMC and constructing multi terminal DC system, and also proves the effectiveness of the proposed evaluation method.