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当多端高压直流输电系统用于远距离输电时,直流线路的电压降落以及线路功率损耗会对电压裕度控制的精度带来较大影响,使直流电压不能稳定控制于一点,为此提出一种适用于多端柔性直流输电系统的精确电压裕度控制方法。推导了多端柔性直流输电系统的dq坐标数学模型,基于直流系统潮流计算的思想,充分考虑线路压降和损耗对控制参考值的影响,对电压裕度的取值进行计算,并在控制器中实现裕度修正。在PSCAD/EMTDC环境中建立了基于模块化多电平换流器的三端直流系统仿真模型,仿真结果验证了所提出的控制方法的正确性和有效性,该方法能够有效避免因电压裕度取值不当造成的控制特性偏移,并在系统受到较大功率扰动时可以有效、迅速地转换控制方式,提升系统稳定性。
When the multi-terminal HVDC system is used for long-distance transmission, the voltage drop of the DC line and the power loss of the line will greatly affect the accuracy of the voltage margin control, so that the DC voltage can not be controlled at a stable point. Therefore, a Accurate voltage margin control method for multi-terminal flexible HVDC system. The dq coordinate mathematical model of multi-terminal flexible HVDC transmission system is deduced. Based on the idea of power flow calculation in DC system, the influence of line voltage drop and loss on control reference is fully considered, and the value of voltage margin is calculated. Margin correction. The three-terminal DC system simulation model based on modular multi-level converter is established in PSCAD / EMTDC environment. The simulation results verify the correctness and effectiveness of the proposed control method. This method can effectively avoid the voltage margin Improper value of the control characteristics caused by the shift, and the system is subject to greater power disturbance can be effectively and quickly switch control mode, improve system stability.