模块化多电平直流融冰装置谐振机理及抑制措施研究

The resonance mechanism and suppression measures of DC ice-melting equipment based on a modular multilevel converter

直流融冰作为电网抵御低温冰冻灾害的有效措施之一,融冰装置在线路覆冰期间的运行可靠性极其重要。首先介绍了全桥模块化多电平直流融冰装置的拓扑结构以及直流融冰装置融冰工作状态下直流侧振荡现象。其次,分析了融冰装置振荡机理并提出了抑制措施,即在直流电压前馈环节引入非线性滤波器对高频谐振进行抑制。最后通过仿真与实验验证表明:基于模块化多电平直流融冰系统阻抗的相频特性得到了大幅度的改善,控制系统可以正常解锁、升压,证明了抑制措施的有效性,降低了高频振荡风险。

DC ice-melting is one of the effective measures to prevent low temperature and freezing disasters in a power grid.The operational reliability of a DC de-icing device is very important during the icing period.This paper first introduces the topology of a full bridge modular multilevel DC de-icing device,and reveals the oscillation phenomenon on the DC side of the DC ice-melting device in the de-icing working state.Secondly,the oscillation mechanism of the ice melting device is analyzed and suppression measures are proposed.That is,a nonlinear filter is introduced in the DC voltage feedforward link to suppress high-frequency resonance.Finally,simulation and experimental verification show that the phase-frequency characteristics of the ice melting system impedance have been greatly improved,and the control system can be unlocked and boosted normally.This proves the effectiveness of the suppression measures and reduces the risk of high frequency oscillation.