孤岛交直流混合微电网功率互助策略

交直流混合微电网可以通过交、直流子微网之间的互助互济来有效协调混合微网系统功率的分配,并提高系统平抑功率波动的能力。为实现交、直流子微网之间合理互助互济,提出了一种孤岛交直流混合微电网功率互助策略。首先,为了避免互联变流器频繁动作带来功率损耗,提出了分层控制策略,该策略将系统运行模式分为功率自治模式与功率互助模式,并对运行模式的切换条件进行了合理设计;其次,提出了基于子微网自身条件以及蓄电池荷电状态(state of charge, SOC)的功率互助目标,并设计了基于交流频率和直流电压反馈的功率协同控制算法以实现功率互助目标。最后,在PSCAD/EMTDC中搭建了仿真模型,仿真结果表明,利用所提互助策略,交、直流子微网能够根据自身条件承担系统功率波动并维持蓄电池处于合理的荷电状态。

Mutual Power Support Strategy for Isolated Hybrid AC/DC Microgrid

Hybrid AC/DC microgrid can effectively coordinate the power distribution of microgrid through mutual power support between two sub-grids, and improve the system’s ability to suppress power fluctuations. In order to realize the reasonable mutual power support between the two sub-grids, this paper proposes a mutual power support strategy for hybrid AC/DC microgrid used in island operation mode. Firstly, in order to avoid the power loss caused by the frequent actions of inter-linking converter, a hierarchical control strategy is proposed, which includes power autonomy model and power interaction model, and the changing between system operating models is designed reasonably. Then the goal of mutual power support based on the conditions of the sub-grids and the state of charge (SOC) of the battery is proposed. Meanwhile, a power cooperation control algorithm, which gives consideration to both AC frequency and DC voltage, is designed to achieve the goal. A simulation model is built in PSCAD/EMTDC. The simulation results show that, with the mutual power support strategy, the AC and DC sub-grids can bear the power fluctuations of the system according to their own conditions. And reasonable SOC of the battery can be maintained.