提高海上风电场经MMC联网系统故障穿越能力的柔性泄能电阻控制策略

A Flexible Control Strategy of Breaking Resistor to Enhance Fault-ride-through Ability for Offshore Wind Farms Integrated to Grid via MMC

离岸较远的海上风电场经模块化多电平换流器型高压直流(modular multilevel converter high voltage direct current,MMC-HVDC)联网较交流联网有技术优势,但直流系统会因电网扰动而闭锁,影响风电功率外送。为提高直流系统抗扰动能力,构建了一种提高风电场经直流联网系统低电压故障穿越能力的柔性泄能电阻方案,具有对风电运行工况和故障强度的广泛适应性。研究了风电运行工况及故障强度对直流系统闭锁的影响,提出了系统的故障穿越安全域。分析了泄能电阻阻值设计原则,给出了柔性泄能电阻阻值的边界。设计了适用于不同风电运行工况的柔性泄能电阻投切控制策略。仿真结果表明:柔性泄能电阻控制策略可以在不同风电运行工况和故障强度条件下有效防范直流系统的闭锁,改善海上风电场经MMC-HVDC联网系统运行的安全性。

The offshore wind farms integrated to power grid via modular-multilevel-converter based high voltage direct current(MMC-HVDC)have technical advantages over AC interconnection.However,the DC system would be blocked due to grid disturbance,thus affecting wind power transmission.In order to improve anti-disturbance ability of DC system,a flexible controlled breaking resistor scheme is proposed to improve low-voltage fault-ride-through ability of the wind farms integrated to grid via HVDC,which has wide adaptability to wind power operation conditions and fault intensity.The influence of wind power operation conditions and fault intensity on DC system blocking is studied,and a fault-ride-through security region of the system is proposed.The design principle of resistance value of the breaking resistor is analyzed,and the boundary of the resistance value of the flexible controlled breaking resistor is given.A flexible switching control strategy of the breaking resistor is designed for different wind power operation conditions.Simulation results show that the flexible control strategy of breaking resistor can effectively prevent DC system blocking under different wind power operation conditions and fault intensities,and improve safety of offshore wind farm integrated to grid via MMC-HVDC.