基于滑模控制的双馈风电机组网侧变流器低电压穿越控制策略

电网电压跌落会引起双馈电机(doubly fed induction generators,DFIG)直流电容两侧功率的不平衡,造成直流电压的波动甚至过电压,严重影响DFIG的安全运行。本文根据DFIG网侧变换器(grid side converter, GSC)和直流侧电容的数学模型,提出了一种基于滑模变结构控制的GSC控制策略。该控制策略采用电压(功率)单环控制代替传统的双闭环级联控制,简化了控制器的设计,提高了系统的响应性能。根据电网故障时直流电容和GSC的功率流动特点,以抑制直流电压波动为目的,提出一种考虑GSC进线电抗器功率波动的改进控制策略。仿真结果表明,该控制策略不仅具有良好的动态响应性能,而且能够有效抑制直流电压波动,提高了电网故障时DFIG的不间断运行能力。

A LVRT Control Strategy for Grid-side Converter in DFIG Based on Sliding Mode Control

Grid voltage dips will induce power imbalance on both sides of the DC-link capacitor in the doubly fed induction generators (DFIG). Therefore, it will result in the fluctuation of DC-link voltage or over-voltage, which seriously affects security operation of the DFIG. According to the mathematical models of the grid-side converter (GSC) and the DC-link capacitor, a control strategy based on sliding mode control (SMC) for the GSC is proposed in this paper. In order to improve the response ability and to simplify the design of the controllers, single voltage (power) control loop is adopted instead of cascaded current and voltage (power) control loops. According to power flow characteristics of DC-link capacitor and GSC when the voltage dip occurs, an improved control strategy by considering the power fluctuation in the reactor of the GSC is proposed to suppress the fluctuation of the DC-link voltage. Simulation results show that the proposed control strategies not only have good dynamic response, but also can effectively suppress the DC-link voltage fluctuation during voltage dips, which improves the uninterrupted operation ability of the DFIG.