可再生能源交流孤网转并网运行中的电压控制策略

柔性直流远距离输送有仅通过直流送出模式和交直流混联送出模式。两种送出模式下,系统的运行点存在较大差异,直接切换会对电网产生较大冲击。文章首先分析了两种送出模式下系统的调压控制特点,指出并网点电压幅值偏差是切换过程的关键点,设计了以可再生能源集群并网点电压偏差最小为主目标,换流站综合无功裕度最大为次目标的柔性切换策略。最后,基于某柔直电网可再生能源送端规划系统进行仿真,验证了所提策略的有效性。

The voltage control strategy in the transformation of renewable energy AC isolated network operation to grid connected operation

There are two delivery modes for large-scale renewable energy that is sent to load center through flexible DC transmission system:DC only and AC-DC hybrid mode.When the renewable energy is transmitted only through flexible DC,the collection island at the sending end is decoupled with the AC main power grid,whose voltage is only formed by the voltage source converter(VSC)station.After being switched to AC-DC hybrid transmission mode,the AC islanding system is closely related to the main AC power grid.The voltage state of its collecting bus is determined by the electrical parameters of the system and the voltage of the AC main network.The operation states of the two transmission modes are quite different,and the switching operation will have a great surge on the power grid.To restrict the surge,this paper first proposes the switching process of the two operating modes,analyzes the characteristics of the system voltage regulation under the two operating modes,and build the flexible switching model.Then,the main aim of the switching strategy is to minimize voltage deviation,and the converter's comprehensive reactive power margin is secondary,considering all VSC operation constraints.Finally,based on a planning system,the simulation is applied to verify the effectiveness of the proposed strategy.