【作者】 王仕韬；

【导师】 吕征宇； 张德华；

【作者基本信息】 浙江大学 ， 电力电子与电力传动， 2011， 博士

【摘要】 风能是新兴的绿色能源。为了降低每千瓦时的发电成本,风力发电机组正朝着大功率方向发展,单机功率等级不断提高。快速提高的功率容量带来了新的机遇和挑战。本文对风力发电系统,主要侧重于机侧整流器部分,做了以下几个方面的研究和尝试。多个发电机与单级增速箱相结合的半直驱式替代永磁直驱装置,实现了发电机功率密度的提高和增速装置机械强度要求的降低。根据该装置特点,提出了新型整流器输出端串并联组合的多脉整流装置。由于机组多个发电机之间转速相同、输出端之间电气隔离,利用发电机输出交流电压的电角度不同和发电机之间电气角度的错位安装,整流器的输出电压串联叠加后,电压峰值脉波数增加,幅值变小,从而获得平稳的直流功率输出,降低滤波电容容量。多组整流模块并联扩容,并可以根据风速范围切入切出,提高变流器效率。为了克服现阶段IGBT器件对发电机输出端口电压和变流装置容量进一步发展的限制,在变拓扑柔性变流器理论的基础上,提出了具有宽电压输入范围的变拓扑晶闸管整流器。该整流器由两个晶闸管整流桥和包括二极管与开关的辅助电路组成。通过改变辅助电路中开关的状态,实现了两个晶闸管整流桥在串联和并联模式之间的动态切换：当风机转速比较低时,开关闭合,两个整流桥串联在一起,提高输入电压；当风机接近额定转速时,开关断开,两个整流桥并联在一起扩大功率容量。变拓扑整流器替代常用的三相六管PWM整流器或者不控整流加boost升压的二级串联整流器,整流侧完全采用晶闸管器件,使得电力电子器件不再是限制发电机输出电压等级和功率容量提升的瓶颈。工作过程中的动态结构切换是变拓扑变流器控制的核心问题,也是困扰变拓扑柔性变流器的难题。采用传统的PI控制时,虽然控制方法成熟,但是动态效果不理想,无法补偿变拓扑过程存在的电流过冲。新型电流峰值预测控制替代了传统方法用来消除拓扑切换过程的电流过冲,不但获得了切换过程中平滑的功率输出,而且取得快速的电流动态响应,提高了整流器抗谐波干扰能力。新的电流峰值预测控制方法基于交流电压伏秒积分的周期性变化。利用交流电压伏秒积分变化的周期性,晶闸管触发后,电感电流在本周期内将要到达的最大峰值可以根据上个周期的电压伏秒变化趋势做出预先判断。因此,预测模型只涉及直流侧电感上的电压伏秒积分与电流之间的关系,与负载无关,大大简化了控制计算,避免了以往预测控制中超越函数的求解。而且晶闸管的触发不再依赖电压相位信息,提高了抗谐波干扰能力。仿真和实验结果表明并行计算的两个电流峰值预测控制器成功实现了拓扑结构动态切换的平滑过渡,消除了电流过冲。说明变拓扑的变流器装置采用合理的控制策略,完全能够克服动态拓扑变化带来的不利影响,在拓扑切换的过程中仍保持平滑的功率输出。新型变拓扑结构的晶闸管整流器不能实现发电机的单位功率因数运行。但是六相双Y永磁同步发电机与变拓扑变流器配合使用时,发电机内部5、7次谐波磁势显著削弱,使得转子表面附加损耗和转子温升大大降低,因此,由于非正弦波形包含谐波所造成的发电机降额使用的情况显著得到改善。沉重的机舱通过细长的塔架支撑树立在半空中,是典型的欠阻尼系统,在受到风力作用将长时间前后振荡。采用多变量状态反馈扰动调节控制,对造成塔架振荡的风速扰动进行主动的变桨距调节,增加塔架阻尼,降低运行中塔架的机械应力和疲劳。更多还原

【Abstract】 Wind power is an emerging clean energy source that can be relied on for the long-term future. The power capacity of wind turbines grow rapidly in recent years in order to cut the cost of per kWh down. The soaring growth in capacity of wind turbines brings new problems and challenges, too. New solutions provided in article are trying to solve some problems, especially focus on rectification side.Multi-generator with single-stage gearbox substitutes the single PM generator, achieving high power density with low mechanical stress. A converter suitable for this new type power system is proposed. Based on series and parallel connection between several electrical isolated rectifier modules with different phase angle, the multi-pulse rectifier achieves smooth power output with high voltage and low current.A novel flexible thyristor rectifier with wide input voltage range is presented based on flexible topology converter theory. The rectifier consists of two 3-phase thyristor bridges and an auxiliary circuit containing diodes and a switch. By changing the state of the switch, the relationship of the two rectifiers jumps dynamically between series and parallel mode. When the turbine speed is low, the switch is turned on; the two bridges work in series mode to increase the input voltage. When the turbine speed is approaching to the rated speed, the switch is off; the two bridges work in parallel to enlarge power capacity. The switchable thyristor rectifier substitutes traditional 3-phase PWM rectifier or diode plus dc-dc boost rectifier as front end, the generator design is free from voltage and power level limited by IGBTs.The process of dynamic topology switching is an important issue and a great challenge for control. Traditional PI control methods are not satisfactory when applied to flexible topology converter, because the current overshoot during topology switching can not be compensated. Quick current tracking responses, robust operations under polluted voltage, especially the elimination of current overshoot are achieved when a novel peak current predictive controller is applied to the novel flexible thyristor rectifier.The AC voltage integration on inductor is periodical according to the novel peak current predictive control. Therefore, the maximum peak current on inductor can be predicted according to the trend of voltage integration in last cycle when triggering. As a result, prediction model is established only on the relationship of voltage integration and current of the inductor. It simplifies the calculation process greatly, because it has nothing to do with the load, thus avoiding solving transcendental functions based on load model. Triggering of thyristor is no longer depending on the voltage phase information, and the robustness of performance is improved. The novel control method is verified by both simulation and experiment. Two predictive controllers calculate the parallel and the series mode separately, achieving a smooth transition during topology switching. Reasonable control strategy can eliminates the adverse effects brought by topology switching. The theory of flexible topology converter is further verified in the AC-DC power conversion.The generator cannot operate in unity power factor using the flexible topology thyristor rectifier. But, the 6-phase double-Y PM machine has the advantage of low 5th and 7th harmonics in space flux when connected with rectification load. When it is adopted with the new flexible thyristor rectifier, the degraded usage of generator is alleviated greatly compared with 3-phase PM machines.The heavy nacelle half sky is supported by a slim tower. The system is an under damped system, and it oscillating for a long run under the push of wind. The disturbance accommodating controller derives disturbances of wind speed from state space variables, and then compensates it by adjusting pitch. Results show that the damping ratio is improved greatly, and the mechanical fatigue drops accordingly.更多还原