海上风电经柔性直流送出系统高频振荡分析及抑制策略

High frequency oscillation analysis and suppression strategy of offshore wind power through MMC-HVDC system

近年来,柔性直流输电已经是风电深远海开发的有效方案,随着大量用于远海风电并网的柔性直流输电系统不断投运,高频振荡现象在实际工程中频繁出现。然而,现有研究大多聚焦于新能源交流并网系统或异步分区电网交互所产生的高频振荡现象,针对海上风电经柔性直流送出系统的高频振荡研究尚不充分。并且现有模块化多电平换流器(MMC)高频段阻抗模型通常忽略换流器中、低频段特性,使得投入高频振荡抑制策略对中、低频阻抗特性的影响无法被准确揭示。为此,本文首先考虑系统链路延时的影响,基于谐波状态空间建立MMC全频段阻抗模型。在此基础上,分析海上风电经柔性直流送出系统高频振荡机理,并设计控制参数优化策略。最后,基于Matlab/Simulink搭建海上风电经柔性直流送出系统电磁暂态仿真模型,并验证本文所建阻抗模型的精确性以及高频振荡抑制策略的有效性。

In recent years,high voltage direct current(HVDC)transmission system has been an effective scheme for the development of wind power in the deep sea.With the continuous operation of a large number of HVDC transmission systems for the grid connection of wind power in the deep sea,high-frequency oscillation phenomenon frequently occurs in practical projects.However,most of the existing research focuses on the high-frequency oscillation phenomenon generated by the interaction of new energy AC grid-connected system or asynchronous zonal pow-er grid,and the research on the high-frequency oscillation of offshore wind power through flexible direct transmis-sion system is not sufficient.Moreover,the existing modular multilevel converter(MMC)high-band impedance model usually ignores the characteristics of the low frequency band of the converter,so that the influence of the high-frequency oscillation suppression strategy on the low-frequency impedance characteristics cannot be accurately revealed.Therefore,this paper first considers the influence of system time delay,and establishes the impedance model of MMC based on the harmonic state space.On this basis,the high-frequency oscillation mechanism of offshore wind power through HVDC transmission system is analyzed,and the control parameter optimization strategy is designed.Finally,based on Matlab/Simulink,the electromagnetic transient simulation model of the offshore wind power through HVDC transmission system is built to verify the accuracy of the impedance model and the effectiveness of high-frequency oscillation suppression strategy.