机组协同-分布卸荷的风电场-柔直并网系统故障穿越方法

为降低风电场-柔性直流并网系统在交流主网发生低电压故障时的穿越成本,提出一种直流耗能装置与风电机组卸荷电路协同作用的电网故障穿越策略,在电网故障时送端换流器配合风电场快速降低直流功率输出.由于直流耗能装置仅在故障发生的前期、风电场输出功率下降前起到限制直流电压升高的作用,该策略能够显著降低直流耗能装置的体积.在此基础上,该策略将直流耗能装置中的耗能电阻分散置入到受端模块化多电平换流器中,进一步降低了卸荷成本.最后,在PSCAD/EMTDC仿真软件中,构建了风电场-柔性直流并网系统的仿真算例,对所提出的故障穿越方法的正确性和有效性进行了验证.

Fault Ride-through Method of Flexible HVDC Transmission System for Wind Farm Integration Based on Coordination of Wind Turbines and Distributed Braking Resistors

In order to reduce the ride-through cost of the flexible high voltage direct current (HVDC) system with wind farm integration when a low-voltage fault occurs in the AC main grid, this paper proposes a grid fault ride-through strategy in which the DC energy dissipation equipment and the DC choppers in wind turbines work together. The wind farm will reduce its DC power output with the coordination of the sending-end converter during the grid fault. The DC energy dissipation equipment is only required to limit the DC voltage increase in the early stage of the grid fault before the output power of the wind farm have been reduced. Therefore, this strategy could greatly reduce the volume of the DC energy dissipation equipment. On this basis, the proposed strategy integrates the energy dissipation resistor of the DC energy dissipation equipment into the receiving-end modular multilevel converter, to further reduce the unloading cost. Finally, a simulation example of the flexible HVDC system with wind farm integration is constructed in the PSCAD/EMTDC simulation software, which verifies the correctness and effectiveness of the proposed fault ride-through method.