【目的】随着新能源发电比例的持续提高,构网型变换器凭借其主动电压与频率支撑能力,已成为实现高比例新能源电力系统可靠接入与稳定运行的关键技术。然而,由于功率器件的过流承受能力有限,当电网发生电压跌落或其他故障时,构网变换器易出现功角偏移、同步失稳及暂态过流等问题,从而对系统稳定运行构成显著挑战。【方法】针对上述问题,本文基于构网变换器的等效阻抗模型,结合故障前后系统电压与输出电流矢量关系图,系统分析故障过程中过流的产生机理及电压幅值与功角变化对故障电流幅值的影响。在上述分析基础上,提出了一种兼顾暂态同步稳定性与故障过流抑制的综合控制策略。所提策略通过自适应降低有功功率参考值以增强系统功角稳定性,同时引入故障电流幅值约束,并提出内部电压参考调节和浪涌电流抑制虚拟阻抗结合的控制方式,实现全故障过程的过流抑制。【结果】最后,通过试验平台进行对比测试验证了所提策略的合理性和有效性。试验结果表明,相较于传统方法,所提策略在提升构网型变换器暂态性能方面具有显著优势,能够在不同电网故障下维持系统功角稳定,并有效抑制故障电流,确保浪涌电流和故障稳态过流幅值均低于预设阈值。【结论】本文提出的考虑电流约束的构网变换器综合故障穿越策略,兼顾了功角稳定和过流抑制,能显著提升构网型变换器在复杂电网故障条件下的运行可靠性。

[Objective] With the continuous increase in the penetration of renewable energy generation, the grid-forming (GFM) converter, owing to their capability to actively support voltage and frequency, are regarded as a key technology for enabling the reliable integration and stable operation of power systems with high shares of renewable energy. However, due to the limited overcurrent withstand capability of power semiconductor devices, when voltage sags or other faults occur in the power grid, the GFM converter prone to large power angle deviations, loss of synchronization, and transient overcurrent, thereby posing significant challenges to stable operation. [Methods] Aiming at the above problems, based on the equivalent impedance model of the GFM converter and combined with the vector diagrams of system voltage and output current before and after the fault, this paper systematically analyzed the generation mechanism of overcurrent during the fault process and the influence of voltage amplitude and power angle variations on the fault current amplitude. On the basis of the above analysis, a comprehensive control strategy that took into account both transient synchronization stability and fault overcurrent suppression was proposed. The proposed strategy adaptively reduced the active power reference value to enhance the power angle stability of the system. Meanwhile, to achieve overcurrent mitigation throughout the entire fault process, the strategy implemented fault current magnitude constraints along with a combined control approach. This approach synergized internal voltage reference regulation for steady state fault current management and virtual impedance for surge current suppression. [Results] Finally, the rationality and effectiveness of the proposed strategy were verified through comparative tests on an experimental platform. The experimental results indicated that, compared with conventional methods, the proposed strategy had significant advantages in enhancing the transient performance of the grid-forming converter. It was able to maintain the power angle stability of the system under various grid fault conditions, effectively suppress the fault current, and ensure that both the surge current and the steady-state fault overcurrent magnitude were below the preset thresholds. [Conclusion] The comprehensive fault ride-through strategy for the GFM converters considering current constraints proposed in this paper takes into account both power angle stability and overcurrent suppression, and can significantly improve the operational reliability of grid-forming converters under complex grid fault conditions.

国家自然科学联合基金（U25B200105）