考虑直流子网影响的交直流混合微电网谐振特性分析

Analysis of Resonance Characteristics of AC/DC Hybrid Microgrid Considering the Influence of DC Subgrid

交直流混合微电网是未来配电网的重要组成形式。由于直流子网在混合微电网中所占比重提高,势必会对并网模式下的交直流混合微电网的谐振特性产生影响,而利用频域分析法需建立基于交直流混合微电网的高阶传递函数,建模困难。为了解决上述问题,提出了直流子网和互联变流器(interlinking converter,ILC)融合阻抗建模方法,建立了并网模式下交直流混合微电网系统的等效阻抗模型,利用模态分析法计算出系统谐振频率、参与因子以及参数灵敏度等谐振特性,进一步分析了ILC和直流子网参数变化对系统谐振特性的影响。分析表明,ILC和直流子网部分参数变化会大幅改变系统的谐振频率及谐振峰值。结论不仅有利于谐波谐振的治理,同时也为系统参数的设计提供了依据。最后在Matlab/Simulink仿真平台上搭建了交直流混合微电网仿真模型,验证所进行的谐振模态分析及参数变化对谐振特性影响的正确性。

The AC/DC hybrid microgrid is an important form of the future distribution gridwork. The increases of the proportion of DC subgrid in a hybrid microgrid will inevitably have an impact on the resonance characteristics of the AC/DC hybrid microgrid in grid-connected mode;however, the use of frequency domain analysis method requires the establishment of high-order transfer function based on AC/DC hybrid microgrid, whereas it is difficult to model. In order to solve the above problems, it is proposed to establish a fusion impedance modeling method of the DC subgrid and the interlinking converter(ILC), and to establish an equivalent impedance model of the AC/DC hybrid microgrid system in grid-connected mode, thus the system resonance characteristics such as frequency, participation factors and component sensitivity are calculated by the modal analysis method, and the influences of ILC and DC subgrid parameter changes on the system resonance characteristics are further analyzed. The analysis shows that ILC and some parameter changes of the DC subgrid will obviously change the resonance frequency and resonance peak value of the system. The analysis result not only is conducive to the treatment of harmonic resonance, but also provides a basis for the design of system parameters.Finally, an AC/DC hybrid microgrid simulation model was built on the Matlab/Simulink simulation platform to verify the correctness of the resonance modal analysis and the effect of parameter changes on the resonance characteristics.