基于虚拟阻抗的微网功率分配策略研究

孤岛模式运行的微电网,其稳定性和可靠性要求各发电单元均衡分担负荷,电能质量要求系统电压和频率波动在一定范围内。采用传统下垂控制的微电网,电压和频率波动受负荷影响,电源输出特性与输电阻抗等因素有关,无法满足以上要求。本文分析了功率均衡分配条件,利用虚拟阻抗实现功率解耦和无功功率合理分配。针对虚拟阻抗以及下垂控制造成的母线电压降低,引入计算母线电压重新设计无功下垂方程,降低负荷变化和虚拟阻抗对母线电压的影响,保证其波动在规定范围内,提高了微网电能质量。

Study on Microgrid Power Allocation Strategy Based on Virtual Impedance

The stability and reliability of microgrid working in island mode require each power generation unit to share the load equally and the power quality requires system voltage and frequency fluctuations within a certain range.The voltage and frequency fluctuation of microgrid with traditional droop control are affected by load,the output characteristic of source is related to such factors as transmission impedance and above requirement cannot be met.In this paper,the equal power distribution condition is analyzed,the virtual impedance is used to realize power decoupling and reasonable distribution of reactive power.Regarding bus voltage droop due to virtual impedance and droop control,an improved droop control method is proposed.The calculation bus voltage is introduced to redesign the reactive power droop equation so to reduce the influence of load variation and virtual impedance on the bus voltage,assure the fluctuation within the specified range and improve power quality of the microgrid.