电网电压对称跌落下Z源永磁直驱风电系统的运行与控制研究

在Z源风力发电系统中,当电网电压发生对称跌落时,会导致Z源网络电容电压上升和交流侧过电流,严重威胁风电机组和变流器的安全,破坏系统的稳定运行。针对这一问题,提出一种适用于Z源永磁直驱发电系统在电网电压对称跌落情况下的故障穿越策略。详细分析了Z源永磁直驱系统的工作原理,建立了Z源逆变器的数学模型。在电网电压正常情况下,运用Z源电容电压外环控制和电流内环控制的双闭环控制策略,实现Z源风力发电系统的单位功率因数并网运行;在电网电压发生三相对称跌落的情况下,分析功率流动情况,将耗能crowbar电路并联在Z源网络输入端,以实现系统的低电压穿越,从而保持恒定的Z源电容电压和稳定的交流侧电流。最后,在Matlab/Simulink中搭建模型进行系统仿真,仿真结果验证了所提方法的有效性。

Research on the Operation and Control of Z-Source Wind Power Generation System Under Grid Voltage Symmetry Faults

A symmetrical drop in power grid voltage in the Z source wind power generation system will lead to an increase of the capacitor voltage of Z-source network as well as the occurrence of AC-side current, thus seriously threatening the safety of wind turbines and converters, and destroying the stable operation of the system. In view of the above-mentioned problems, a proposal has been made of a fault ride-through strategy for permanent magnet direct drive power generation system with Z source under symmetrical drop in voltage. A detailed analysis has been made of the working principle of Z source permanent magnet direct drive system, followed by the eatablishment of the mathematical model of Z source inverter. Under the normal voltage of the power grid, the dual closed loop control strategy of the Z source capacitor voltage outer loop control and the current loop control is used to realize the unit power factor of the Z source wind power generation system. In the case of the three-phase symmetry drop of the grid voltage, an analysis has been made of the power flow situation. The low voltage crossing of the system can be achieved with a parallel between the energy dissipation crowbar circuit and the input terminal of the Z source network, thus maintaining a constant Z source voltage and stable AC side current. Finally, a model is to be built in Matlab/Simulink to simulate the system, with its results verifying the effectiveness of the proposed method.