基于储能的风电柔直并网系统直流故障穿越协调控制策略

Coordinated Control Strategy of DC Fault Ride-through for Flexible DC Grid-connected System of Wind Power Based on Energy Storage

采用具有明显技术和经济优势的架空线柔性直流输电是大规模可再生能源并网的理想方案。然而,架空线故障率较高且直流系统故障发展迅速,仅靠直流断路器隔离故障线路并不能完善地解决系统的故障穿越问题。为解决该问题,针对大规模风电场经柔性直流输电并网系统的直流线路故障工况,充分利用风电场中广泛配置的储能系统,提出从故障定位隔离到故障类别判断,再到储能系统与换流站、风电场之间协调控制的一套完整直流故障穿越策略,并从能量角度展开故障特性分析。与现有工程中采用的耗能电阻方式相比,所提策略调节系统不平衡功率的灵活性更高,控制效果更优,且对所储存能量可以再利用,避免能量浪费。此外,为降低对储能系统的功率及容量需求,提出风电机组转子加速控制以减少风电场出力的方案。最后,在PSCAD/EMTDC仿真平台验证了所提方法的有效性。

It is an ideal scheme for grid connection of large-scale renewable energy to adopt overhead-line flexible DC transmission with obvious technical and economic advantages. However, the failure rate of overhead lines is high and the DC system faults develop rapidly. Isolating the fault lines by DC circuit breakers alone cannot solve the fault ride-through problem of the system perfectly. To solve this problem, aiming at the DC line fault condition of grid-connected system of large-scale wind power through flexible DC transmission, a complete DC fault ride-through strategy is proposed from fault location and isolation to fault category judgment, and then to the coordinated control between energy storage system, converter station and wind farm by making full use of the extensive configuration of the energy storage system in the wind farm. Then, the fault characteristic is analyzed from the perspective of the energy. Compared with the energy consumption resistor method used in the existing projects, the proposed strategy has higher flexibility and better control effect in adjusting the unbalanced power of the system, and can reuse the stored energy to avoid energy waste. In addition, in order to reduce the power and capacity requirements of the energy storage system,the rotor acceleration control of wind turbines is proposed to reduce the output of wind farms. Finally, the effectiveness of the proposed method is verified on the PSCAD/EMTDC simulation platform.