基于储存能量特征的直流孤岛电压稳定控制方法

A Direct-current Island Voltage Stability Control Method Based on Stored Energy Characteristics

  • 摘要: 针对高压直流弱送端系统进入孤岛运行状态后电压失稳的问题,提出了一种基于储存能量特征的直流孤岛电压稳定控制方法。首先,建立了直流送端系统无功分布模型,解析了直流系统进入孤岛后的电压跌落与无功缺额的关系,推导了直流孤岛并/离网前后换流母线电压变化的表达式。然后,构造了考虑控制环节响应的直流孤岛系统动态能量函数,建立了整流器电流指令值与储存能量的关联关系。在此基础上,提出了计及系统能量稳定性约束的电流指令值调整方法,减少了直流恢复过程中的无功消耗,实现了电压波动的快速平抑。最后,在RT-LAB平台搭建了直流孤岛外送系统模型对所提方法进行验证。实验结果表明,该方法减小了直流外送系统切除大容量电网后的电压波动,并且可以在孤岛运行后实现电压稳定性的快速恢复。

     

    Abstract: Aiming at the issue of voltage instability in high voltage DC weak sending-end systems upon entering the island mode, a voltage stability control method is proposed based on stored energy characteristics. Firstly, a reactive power distribution model of the DC feeder system is established. The relationship between voltage sag and reactive power deficiency after a DC system enters the island mode is analyzed, and the expression for the voltage variation of the converter bus before and after DC island synchronization and desynchronization processes is derived. Subsequently, the dynamic energy function of the DC island system considering the response of the control link is constructed, and the relation between the rectifier current command value and the stored energy is established. On this basis, a current command value adjustment method is put forward, which takes into account the energy stability constraints of the system. The proposed method is capable of reducing the reactive power consumption in the process of DC recovery and achieving the rapid stabilization of voltage fluctuations. Finally, a DC island transmission system model is built on the RT-LAB platform to verify the proposed method. The experimental results demonstrate that the proposed method mitigates the voltage fluctuations after the disconnection of the DC outgoing system to the large capacity grid, and enables rapid recovery of voltage stability after isolated island operation.

     

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