针对现有低电压穿越（LVRT）研究难以准确全面评估变流器同步运行能力的问题,首先结合LVRT特性和电网侧特性定量研究不同因素对准静态平衡点的影响,揭示系统准静态平衡点的存在条件。其次,分析LVRT特性对并网逆变器暂态稳定性和小信号稳定性的影响,明晰电网故障期间系统不仅存在暂态失步的风险,而且难以在准静态平衡点稳定运行。基于以上理论分析,提出一种提高并网逆变器LVRT同步运行能力的优化策略。该策略在LVRT期间根据电网运行状态自适应调整锁相环参数,不仅可降低系统暂态失步的风险,还可增强其小信号稳定裕度。最后,通过仿真和实验验证了理论分析的正确性和优化策略的有效性。
Abstract
To address the problem that the existing low voltage ride-through（LVRT） studies cannot accurately and comprehensively assess the synchronous operation capability of converters, the effects of different factors on the quasi-static equilibrium point are quantitatively investigated by combining the LVRT characteristics and the grid-side characteristics, and the existence conditions of the quasi-static equilibrium point of the system are revealed. The influence of LVRT characteristics on the transient stability and small-signal stability of grid-connected inverters is analyzed, and it is clarified that the system not only has the risk of transient loss of synchronization during grid faults but also is difficult to operate stably at the quasi-static equilibrium point. Based on the above theoretical analysis, an optimization strategy for improving the LVRT synchronous operation capability of grid-connected inverters is proposed. The strategy adaptively adjusts the phase-locked loop parameters according to the grid operation state during LVRT, which not only reduces the risk of system transient loss of synchronization but also enhances its small signal stability margin. Finally, the correctness of the theoretical analysis and the effectiveness of the optimization strategy is verified by simulation and experiments.
关键词
逆变器 /
暂态稳定性 /
锁相环 /
小信号稳定性 /
准静态平衡点
Key words
inverter /
transient stability /
phase locked loop /
small-signal stability /
quasi-static equilibrium point
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基金
国家重点研发计划（2022YFB4202301）; 国家自然科学基金重点项目（51937003）
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