新型配电网中柔性源荷容量占比的持续增加有利于提高配电网的灵活性和可控性,提出以基于虚拟同步控制的光伏并网变流器为对象,深入研究其对配电网电能质量的提升路径.首先,考虑锁相环的动态性能建立了光伏并网变流器在最大功率点跟踪(Maximum power point track,MPPT)模式下的序阻抗模型,揭示了含光伏接入的配电网电能质量问题产生机理;然后,建立基于虚拟同步控制策略的光伏并网变流器阻抗模型,并明确该控制策略可降低台区配电网的等效阻抗,同时增强光伏变流器的电压支撑能力和改善直流互联装置的运行环境,并从谐波含量和电压波动两方面证明其对配电网电能质量的提升作用,为交直流混联配电系统电能质量主动优化与协同控制技术提供了新思路.最后,在Matlab/Simulink中建立仿真模型验证了所提方法的有效性.
Improvement of Power Quality of Distribution Network by Photovoltaic Grid Connected Converter Based on Virtual Synchronous Control
The continuous increase of the proportion of flexible source load capacity in the new distribution network is conducive to improving the flexibility and controllability of the distribution network.Taking the PV grid-connected converter based on virtual synchronous control as the object,the path to improve the power quality of the distribution network is deeply studied.Firstly,considering the dynamic performance of phase-locked loop,the sequence impedance model of photovoltaic grid-connected converter in the maximum power point track(MPPT)mode is established,and the generation mechanism of power quality problems in distribution network with photovoltaic access is revealed.Secondly,the impedance model of PV grid-connected converter based on virtual synchronous control strategy is established and it is clear that this control strategy can reduce the equivalent impedance of the distribution network in the substation area,enhance the voltage support ability of the PV converter and improve the operation environment of the DC interconnection device,and prove its role in improving the power quality of the distribution network from the aspects of harmonic content and voltage fluctuation.It provides a new idea for active optimization and collaborative control technology of power quality in AC/DC hybrid distribution system.Finally,a simulation model is built in Matlab/Simulink to verify the effectiveness of the proposed method.
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