基于虚拟同步发电机低电压穿越的无缝切换控制策略

SEAMLESS SWITCHING CONTROL STRATEGY FOR LOW VOLTAGE RIDE-THROUGH BASED ON VIRTUAL SYNCHRONOUS GENERATOR

虚拟同步发电机(VSG)控制使分布式发电接入电网呈现友好特性,该文在建立逆变器VSG控制数学模型基础上,针对分布式电源逆变器采用VSG控制,针对其不具备低电压穿越(LVRT)能力的问题,结合传统LVRT控制方法,提出一种基于电压幅值和相位预同步的模式无缝切换控制策略,引入预同步单元对VSG输出实时矫正,有效避免LVRT/VSG模式切换前后的相位不一致问题。仿真结果表明该控制策略能够使逆变器在电网低电压故障期间抑制暂态冲击电流和改善并网电能质量,保证基于分布式电源逆变器VSG实现LVRT而不脱网,验证了所提方法的正确性和有效性。

The distributed generation based on virtual synchronous generator(VSG)control strategy can connect to grid friendly. Based on the establishment of the mathematical model of the VSG control strategy and combined with traditional low voltage ride-through(LVRT)control method,according to the problem of the distributed generation based on VSG control strategy without LVRT capacity,this paper proposed a mode seamless switching control strategy based on voltage amplitude and phase synchronization. The VSG output phase is corrected by pre-synchronization unit in real time,and the problem of voltage amplitude and phase inconsistency before and after the LVRT/VSG mode switching was avoid Effectively. The simulation results show that the proposed control strategy can make the converter suppress the transient impulse current and improve the power quality of the grid during the grid fault,and furthermore guarantee the distributed generation based on VSG control strategy connect to power grid safely,the correctness and effectiveness of proposed method is verified.