Virtual control method applied to Modular Multilevel Converter
Virtual control method applied to Modular Multilevel Converter
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DOI：
10.1016/j.egyr.2021.11.099
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发表时间：
2021-11
期刊：
影响因子：
5.2
通讯作者：
Z. Zhang;Chuyang Wang;Yang Xu
中科院分区：
文献类型：
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作者：
Z. Zhang;Chuyang Wang;Yang Xu
基于模块化多电平变换器（MMC）结构的直流Transformer具有可扩展性强、输出电压谐波含量低、易于实现背靠背连接、功率传输效率高等优点。它广泛应用于直流配电网。然而，传统的控制方法很难为直流配电网提供惯性，从而在新能源输出波动、直流配电网故障或其他干扰发生时降低了配电网的稳定性。针对直流母线电压易受功率波动影响的问题，提出了一种应用于MMC结构直流Transformer的虚拟惯性控制方法。类似于在交流配电网中引入虚拟同步发电机来提高系统惯量，本文在传统的两相移相控制的基础上，设计了一种通过增加虚拟电容来动态调节虚拟惯量的控制策略。文中还介绍了虚电容的计算方法。当直流微网中的功率波动较大时，该策略能有效增强直流配电网的惯性，抑制直流母线电压波动。最后在PLECS仿真软件中建立了含分布式电源的直流配电网模型，并与传统控制策略进行了比较，验证了该控制策略的有效性。
The DC transformer based on the Modular Multilevel Converter (MMC) structure has the advantages of robust scalability, low output voltage harmonic content, easy realization of back-to-back connection, and high power transmission efficiency. It is widely used in DC distribution networks. However, traditional control methods hardly provide inertia for the DC distribution network, thereby reducing the stability of the distribution network when new energy output fluctuations, DC distribution network failures, or other disturbances occur. Aiming at the problem that the DC bus voltage is easily affected by power fluctuations, the paper proposes a virtual inertia control method applied to the DC transformer with MMC structure. Similar to the introduction of virtual synchronous generators in the AC distribution network to enhance the system inertia, the paper designs a control strategy for dynamically adjusting the virtual inertia with a virtual capacitor added, which is based on the traditional two-phase shift control. The paper also presents the calculation method of the virtual capacitance. When the power in the DC microgrid fluctuates significantly, the strategy can effectively enhance the inertia of the DC distribution network and suppress the voltage fluctuation of the DC bus. The paper finally establishes a DC distribution network model with distributed power sources in the PLECS simulation software, and verifies the effectiveness of the control strategy compared with the traditional strategy.