海上风电场经柔直送出系统的虚拟导纳中频振荡抑制策略

Virtual admittance control strategy for medium-frequency oscillation in an offshore wind farm when connected to a VSC-HVDC

随着柔性直流输电技术在远海风电的广泛应用,海上换流站接入远海风电场时出现了中频振荡现象,严重危害系统安全稳定运行。为此,提出了一种基于虚拟导纳的中频振荡抑制策略。首先,采用模块化状态空间法建立了海上风电场经柔直送出系统的小信号模型。然后,采用参与因子分析方法揭示了影响中频振荡的关键因素,并分析了各关键因素对中频振荡的影响特性。在此基础上,提出在柔直控制系统中添加虚拟导纳的阻尼控制策略,并基于阻尼控制器对中频、LCL振荡的差异影响划分了控制器参数的稳定域。最后,在Matlab/Simulink中搭建时域仿真模型。结果表明,所提策略在系统不同运行工况下均可有效抑制中频振荡,提高了系统稳定性。

With the widespread application of flexible DC transmission technology(VSC-HVDC)in offshore wind power engineering,medium-frequency oscillation(MFO)may occur when offshore converter stations are connected to offshore wind farms,seriously endangering the safe and stable operation of the system.Therefore,a virtual admittance-based MFO suppression strategy is proposed.First,a modular state space method is used to establish a small signal model of offshore wind farm when connected to a VSC-HVDC.Then,the participation factor analysis method is used to reveal the key factors affecting the MFO,and the impact characteristics of each key factor on the MFO are analyzed.Based on this,a damping control strategy is proposed to add virtual admittance to the VSC-HVDC control system.The stable range of the controller parameters is divided based on the differential influence of the damping controller on MFO and LCL oscillations.Finally,a time-domain simulation model is built in Matlab/Simulink.The simulation results show that the proposed strategy can effectively suppress MFO and improve system stability in different system operating conditions.