【目的】在“双碳”目标驱动下,新能源高比例并网的发展背景下,构网型储能变流器(GFESC)并联运行已成为储能电站规模运行的核心方案,并联工况下因线路阻抗不匹配导致的无功功率无法按容量比例精准分配,成为亟待解决的关键问题。【方法】本文首先通过理论推导,深入分析了并联变流器系统的功率传输机理与无功功率分配误差的产生机制。基于此,提出了一种基于自适应虚拟阻抗的改进型下垂控制策略,旨在动态补偿线路阻抗不匹配对无功功率分配的影响。最后,基于Matlab/Simulink仿真平台搭建并联变流器系统模型,对所提控制策略的效果进行了对比验证。【结果】仿真结果表明,本文所提无功功率分配策略在实际线路阻抗未知、无需变流器间互联通信的条件下,可实现无功功率的高精度按比例分配,同时有效减小变流器输出电压的偏差。该策略引入虚拟阻抗后,有效改善了传统方案中无功功率高精度分配与公共连接点(PCC)电压跌落之间的矛盾,可有效补偿PCC电压,使其恢复至额定工作水平;同时采用电压外环和电流内环组成的双闭环控制结构,有效维持系统电网电压与频率的稳定。【结论】该策略通过自适应虚拟阻抗实现了等效阻抗的精准匹配,为GFESC的规模化运行提供了高可靠性解决方案。

[Objective] Under the development background of high-proportion renewable energy integration driven by the "dual carbon" goals, the parallel operation of grid-forming energy storage converter (GFESC) has become the core solution for large-scale energy storage power stations. However, the inability to accurately allocate reactive power proportionally due to line impedance mismatch in parallel operation has emerged as a critical issue that urgently needs to be addressed. [Methods] The power transmission mechanism of the parallel converter system and the generation mechanism of reactive power allocation errors were first analyzed in depth through theoretical derivation. Based on this, an improved droop control strategy based on adaptive virtual impedance was proposed, aiming to dynamically compensate for the impact of line impedance mismatch on reactive power allocation. Finally, a parallel converter system model was built based on the Matlab/Simulink simulation platform, and the effectiveness of the proposed control strategy was verified through comparative experiments. [Results] The simulation results demonstrated that the proposed reactive power allocation strategy achieved high-precision proportional distribution under conditions where the actual line impedance was unknown and no inter-converter communication was required, while effectively reducing the output voltage deviation of the converters. After the introduction of virtual impedance, the strategy significantly mitigated the conflict between high-precision reactive power allocation and point of common coupling (PCC) voltage drop observed in conventional methods, enabling effective PCC voltage compensation to restore it to the rated operating level. Meanwhile, a double closed-loop control structure consisting of an outer voltage loop and an inner current loop is adopted to effectively maintain the stability of the system’s grid voltage and frequency. [Conclusion] The strategy achieves precise matching of equivalent impedance through adaptive virtual impedance, providing a highly reliable solution for the large-scale operation of GFESC.

国家自然科学基金(52377191)；湖北省自然科学基金(2024AFB584)