双馈风力发电系统低电压穿越的非线性滑模及Crowbar电路控制

发布时间：2018-11-23 09:21

【摘要】：风能是太阳能的另一种存在方式,具有取之不尽、用之不竭、无污染、廉价等优点。风力发电相比于太阳能、核能等新能源具有最优的成本效益,因此世界各国都在积极发展风力发电。为了规范新能源并网,各国针对新能源并网推出了各自的并网导则,其中对低电压穿越能力(Low Voltage Ride Through,LVRT)有明确的严格要求。双馈感应风力发电机(Double-Fed Induction Generator,DFIG)因其具有变换器容量小、重量轻、损耗低、可变速恒频运行等优点,占据风电市场主要份额。因此研究DFIG的低电压穿越具有代表性意义。首先,本文基于三相静止ABC坐标系和两相旋转dq坐标系建立了 DFIG的数学模型,分析DFIG的工作原理,之后基于功率解耦的数学模型以及同步旋转dq坐标系的数学模型介绍了矢量控制策略。其次,针对传统矢量控制策略下DFIG系统低电压穿越能力弱,需改进控制算法的问题,介绍状态反馈精确线性化与变结构控制理论,通过状态反馈精确线性化理论将DFIG非线性、强耦合的数学模型线性化,并利用动态响应速度快的变结构控制理论设计系统低电压穿越控制器。在MATLAB中,搭建6× 1.5MW系统。通过仿真验证,状态反馈精确线性化变结构控制较传统矢量控制能有效提高双馈风力发电系统低电压穿越能力。最后,针对电网电压大幅跌落,添加转子侧Crowbar电路和直流侧卸荷电路,分析了 Crowbar电路阻值的选取和投切时间对低电压穿越效果的影响。针对Crowbar电路接入后,双馈发电机以异步电机运行从电网吸收无功功率,不利于电网电压恢复的问题,通过将定子电压参考值与定子端电压相减,经PI调节后再与系统的实时无功功率相减,再经PI调节后得到无功电流的给定值,优化电网侧变换器无功功率控制策略。在Crowbar电路投入运行后,控制网侧变换器向电网输出无功以支撑电网电压恢复。
[Abstract]:Wind energy is another way of solar energy, which has the advantages of inexhaustible, pollution-free, cheap and so on. Compared with solar energy, nuclear energy and other new energy, wind power generation has the best cost-effectiveness, so all countries in the world are actively developing wind power generation. In order to standardize the grid connection of new energy, various countries have put forward their own grid connection guidelines for new energy, which has strict requirements for low voltage traversing capability (Low Voltage Ride Through,LVRT). Doubly-fed induction wind turbine (Double-Fed Induction Generator,DFIG) has the advantages of small capacity, light weight, low loss, variable speed and constant frequency operation, so it occupies the main share of wind power market. So it is significant to study the low voltage traversal of DFIG. Firstly, based on three-phase static ABC coordinate system and two-phase rotating dq coordinate system, the mathematical model of DFIG is established, and the working principle of DFIG is analyzed. Then the vector control strategy is introduced based on the power decoupling mathematical model and the synchronous rotating dq coordinate system. Secondly, aiming at the low voltage traversing ability of DFIG system under traditional vector control strategy and the need to improve the control algorithm, the state feedback exact linearization and variable structure control theory are introduced. The DFIG is nonlinear by the state feedback exact linearization theory. The strong coupling mathematical model is linearized and the low voltage traversing controller is designed by using the variable structure control theory with fast dynamic response. In MATLAB, a 6 脳 1.5MW system is built. The simulation results show that the state feedback accurate linearization variable structure control can effectively improve the low voltage traversing ability of the doubly-fed wind power generation system compared with the traditional vector control. Finally, the influence of the selection of Crowbar circuit resistance and switching time on the low voltage traversing effect is analyzed by adding rotor side Crowbar circuit and DC side unloading circuit to the large drop of power grid voltage. In view of the problem that the doubly-fed generator absorbs reactive power from the power network by asynchronous motor after the Crowbar circuit is connected, which is not conducive to the voltage recovery of the power grid, the reference value of the stator voltage and the stator terminal voltage are subtracted by subtracting the stator voltage reference value from the stator terminal voltage. After being adjusted by PI and subtracted from the real-time reactive power of the system, the given value of reactive power current is obtained by PI regulation, and the reactive power control strategy of power side converter is optimized. After the Crowbar circuit is put into operation, the grid side converter is controlled to output reactive power to the power grid to support the grid voltage recovery.
【学位授予单位】：西南交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TM614

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