大规模风电经VSC-HVDC接入的电网频率控制策略

The Frequency Control Strategy of the Grid Connected to Large-scale Wind Power via VSC-HVDC

大规模风电经柔性直流输电(Voltage Source Converter Based High Voltage Direct Current,VSC-HVDC)并网替代了电网内大量的同步发电机,削弱了电网的调频能力。对此,文中提出了利用直流电容和风电机组功率备用提高电网频率响应能力的协同控制策略。通过系统频率响应模型分析电网频率响应特性与影响频率的关键因素;建立了直流电压与电网频率的关系式,控制直流电容吸收或释放能量实现VSC-HVDC惯量支撑;基于超速减载控制方案,将电网频率的偏差与微分引入风电机组的功率控制系统,实现风电机组综合频率控制。最后,在大规模风电经VSC-HVDC接入的电网中验证所提控制策略的有效性。结果表明:所提控制策略能够显著提升电网的惯量水平与一次调频响应能力。

For the grid connected to large-scale wind power via voltage source converter based high voltage direct current(VSC-HVDC),a large number of synchronous generators are replaced and frequency regulation capability is weakened in the grid.Therefore,this paper proposes a coordinated control strategy to improve the frequency response capability of the grid.The strategy uses DC capacitance and wind turbine power backup to adjust the frequency.A system frequency response model is used to analyse the grid frequency response characteristics and the key factors affecting frequency;A relationship between DC voltage and grid frequency is established to control the DC capacitor to absorb or release energy to achieve VSC-HVDC inertia support;Based on the over-speed load shedding control scheme,the deviation and differential of grid frequency is introduced into the wind turbine control system to achieve integrated frequency control.Finally,the effectiveness of the proposed control strategy is verified in grid connected with large-scale wind power via VSC-HVDC.The results show that the proposed strategy can significantly improve the inertia level and primary frequency response of the grid.