基于改进下垂控制的孤岛交流微电网无功分配研究

REACTIVE POWER DISTRIBUTION CONTROL STRATEGY IN ISLANDED AC MICROGRID BASED ON IMPROVED DROOP CONTROL

在孤岛运行交流微电网中,受分布式电源(DG)间等效线路阻抗差异的影响,传统下垂控制难以按照下垂增益合理分配无功功率。为此,提出一种基于自适应虚拟阻抗的改进下垂控制方法。即利用DG输出无功信息构造自适应虚拟阻抗,消除等效线路阻抗差异,从而提高无功功率分配精度,并添加电压补偿环节,补偿虚拟阻抗上产生的电压降落。此外,针对频率偏移问题,构造基于DG自身频率与频率参考值差值的积分项作为自频恢复环节以及基于DG输出有功与有功均值差值的积分项作为频率补偿环节。其中,功率均值利用基于局部信息的一致性算法获取,无需全局通信系统控制DG间的信息。最后通过Matlab仿真和RTDS实验设计,验证了所提策略的有效性。

In the islanded AC microgrid,due to the unmatched line impedance among distributed generators(DG),reasonable distributing reactive power according to droop gain is difficulty by using the traditional droop control. Therefore,an improved droop control method based on adaptive virtual impedance is proposed. In order to eliminate the unmatched line impedance and improve the sharing accuracy of reactive power of DG units,the virtual impedance is constructed by taking advantage of the output reactive power of DG units. Aiming at the voltage drop caused by virtual impedance,the voltage compensation method is proposed. Additionally,considering the frequency deviation problem,the integral term based on the deviation between the DG’s frequency and frequency reference value is constructed as the self-frequency recovery link,and the integral term based on the deviation between the DG’s output active power and the average active power of system is used as the frequency compensation link to realize the frequency adjustment without deviation. The average power can be obtained by using distributed consistency algorithm with local information. Finally,the effectiveness of the proposed strategy is verified through Matlab simulation and RTDS experimental.