摘要
随着能源短缺和环境污染日益严重,风能作为一种可再生的绿色能源,其开发与利用得到人们的广泛关注。混合励磁电机综合了永磁电机和电励磁电机的优点,能在高效的前提下实现电机主磁场的调节和控制,在变速恒频的风力发电系统有广阔的应用前景。以多重电枢混合励磁风力发电系统及其控制技术为主题,进行了从理论到实践、从仿真到实验的全面、系统深入的研究。主要研究内容和得到的研究结论如下:
(1)从满足三相逆变器的稳态指标和瞬态电流跟踪指标出发,提出交流侧电感设计的新方法。将设计的电感应用于三相并网逆变系统中,为后面的仿真和实验研究奠定了基础。
(2)根据三相并网逆变器动态数学模型,采用电网电压矢量定向的矢量控制,实现了d、q轴电流的解耦控制和功率因数任意可调。同时,详细分析了如何根据有功功率的误差和无功功率的误差去选择开关表,在此基础上,提出了一种基于新开关表的直接功率控制。
(3)针对三相并网逆变器的特点,将电流预测控制、基于误差函数预测控制、直接功率预测控制应用于三相并网逆变器。针对预测控制是对滤波电感参数比较敏感,采用电感在线辨识控制策略。将电感在线辨识应用于电流预测控制和直接功率预测控制中。最后,对三种预测控制进行了仿真和实验。
(4)为了提高三相并网逆变器可靠性和降低并网逆变器的成本,提出了一种基于锁相环和虚拟电网磁链的无电网电压传感器的控制策略。将无电网电压传感器的控制策略应用于矢量控制和电流预测控制系统中,并通过仿真和实验进行了验证。
(5)针对多重电枢混合励磁发电机,提出一种直流电压可以灵活串、关联切换的控制方案,并对该方案进行了实验。分析了三相并网逆变器并联运行时电流环流回路,建立三相并网逆变器并联时的平均状态模型。通过控制空间矢量调制(SVPWM)算法中不同零矢量在每一个周期的作用时间来抑制环流。
(6)研制了系统的实验平台,以便各种控制策略在实验平台进行实验。
(7)针对混合励磁发电机,提出一种最大风能跟踪的控制方案,通过调节混合励磁发电机的励磁电压去调节发电机的转速,使风机运行在最佳的叶尖速比。三相并网逆变器采用电网电压定向和电压、电流双闭环控制。最后对整个系统进行了建模,在Matlab7.4进行了仿真验证。
With the increasingly serious energy shortage and environmental pollution, the development and use of wind power attract people’s attention due to the wind power as a renewable green energy. Hybrid-excitation motor combines the advantages of permanent magnet motor and electric magnet motor, which main magnetic field can be adjusted and controlled with high efficiency. So the hybrid-excitation motor has broad application prospects in variable speed constant frequency wind power generation system. As wind power generation based on multiple armature hybrid-excitation generator is theme, it is carried out from theory to practice, from simulation to experiment with depth and comprehensive research. Main research contents and conclusions are as followings:
(1) In order to meet the steady demand and the transient current tracking demand for three-phase grid-side converters, a new method is proposed for the inductance design. The designed inductance will be applied in the three-phase grid-connected inverter, which will put the foundation for the subsequent simulation and experiment.
(2) According to the dynamic mathematical model of three-phase grid-connected inverters, using grid voltage orientation vector control, which realizes the decoupling control for the d-axis and q-axis currents and an adjustable power factor. At the same time, it is analyzed in detail how to select the switching table according to the active power error and the reactive power error. On this basis, a novel direct power control is proposed based on the new switching table.
(3) According to the characteristics of the three-phase grid-connected inverter, the current predictive control, predictive control based on the error function and direct power predictive control are applied to three-phase grid-connected inverters. Inductance on-line identification will be applied to current predictive control and direct power prediction control as the predictive control is sensitive to filter inductance parameter. Finally, three kinds of predictive controls are done with simulation and experiment.
(4) In order to improve the reliability and lower the cost for three-phase grid-connected inverters, the control strategy without grid voltage sensors based on phase-locked loop (PLL) and virtual grid flux is proposed. The control strategy without grid voltage sensors is used in vector control and current predictive control and verified by simulated and experimental results.
(5) For the multiple armature hybrid-excitation generator, a new control that the DC voltage can be switched in parallel or series is proposed and is verified by experimental results. The paper analyzes the current circulation loop and constructs the average state model when the grid-connected inverters are operated in parallel. The circulation currents are inhibited by controlling the operation time for zero vectors at every PWM cycle when the space vector pulse width modulation (SVPWM) algorithm is used.
(6) The whole experimental platform is constructed in order to do a variety of control strategies.
(7) The control strategy of maximum wind power tracking is proposed based on the hybrid-excitation generator. The speed of the hybrid-excitation generator can be controlled by controlling the excitation voltage of the hybrid-excitation generator, which makes the wind turbine run at optimum tip speed ratio. Grid voltage orientation, voltage loop and current loop are used for three-phase grid-side inverters. Finally, the mode of the whole system is established in Matlab7.4 and the simulated results verify the control strategy.
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