基于智能卸荷电路的双馈风电机组故障穿越控制

Fault ride-through control of doubly-fed induction generator based on smart chopper circuit

双馈风电机组并网比例不断提高,加剧了电网遭遇外部故障导致规模化脱网问题。文章介绍了现有风机故障穿越控制方案的原理,考虑到频繁投切直流卸荷电路电阻易引起电压波形畸变、超级电容器控制方案成本过高等问题,提出了基于智能卸荷电路的双馈风电机组故障穿越控制方案。该方案将卸荷电阻通过DC/DC变换器与直流母线相连,在控制电路中引入有功功率-直流母线电压的下垂控制环节,实现故障期间电路电阻吸收功率的动态调节,同时设置高、低电压穿越两种模式,根据并网点电压变化情况自主启动。最后,在Matlab/Simulink中对智能卸荷电路控制策略进行验证。仿真结果表明,基于智能卸荷电路的风电机组故障穿越控制策略在直流母线电压抑制、电压恢复所需时间、转子电流畸变程度和方案经济成本等方面具有优势。

With the increasing proportion of wind turbines connected to grid,the security and stability problem caused by wind farm separated from power grid are becoming more and more serious.So it is particularly important to im-prove DFIG fault ride through capacity and reduce the occurrence of off-grid events.In view of the problems,existing DFIG fault ride through control schemes are introduces first.Considering that frequently switched of DC chopper circuit is easy to cause voltage waveform distortion and supercapacitor control scheme has high eco-nomic cost,the DFIG fault ride through control scheme based on smart chopper circuit is further proposed.The proposed method is upgraded based on DC chopper circuit.It connects the unloading resistance with the DC bus through DC/DC converter and introduces active power-DC voltage droop control link to adjust the circuit re-sistance power dynamically during fault period.Besides it sets two modes of high and low voltage crossing,which can be started automatically according to grid connected voltage.Finally,the smart chopper circuit con-trol scheme is verified in Matlab/Simulink.The simulation results show that considering the DC bus voltage sup-pression effect,the regulation time for voltage recovery,the distortion degree of rotor current and the economic cost of schemes,fault ride-through control of DFIG based on smart chopper circuit has the most advantages.