【作者】 谷鑫；

【导师】 夏长亮；

【作者基本信息】 天津大学 ， 电机与电器， 2010， 博士

【摘要】 在能源安全问题日趋严峻的形势下,本文阐述了风能利用与风力发电的重要意义及其广阔的发展前景。为适应大容量风电系统的发展趋势,提出了一种适用于直驱式永磁风力发电系统的功率变换器拓扑结构——Boost斩波—三电平变换器。在该结构中,发电机定子端连接二极管整流桥,电网侧采用二极管箝位型三电平变换器,整流桥与网侧变换器之间通过Boost三电平斩波器连接。基于该拓扑结构,并针对网侧三电平变换器直流侧中点电位不平衡的问题,提出了Boost三电平斩波器的相差控制方式,该控制方式通过调节斩波器中两个功率器件开关信号间的相差,达到平衡输出侧中点电位的目的,而在控制中点电位过程中,并不改变斩波器的升压特性。根据该控制方式的基本原理,建立了Boost三电平斩波器的数学模型,该模型为斩波器的控制器设计提供了理论依据。鉴于通过Boost三电平斩波器同时实现风电系统MPPT控制与网侧三电平变换器中点电位平衡控制,因此斩波器控制器采用并行双PI调节的控制策略。为验证该控制策略的可行性,将其应用于一个典型的大容量风力发电系统,并进行了仿真研究,结果表明该控制策略能够达到预期的效果。为进一步验证该控制策略的有效性,与两种基于短矢量冗余开关状态选择的中点电位平衡控制策略进行了对比分析,并将这两种控制策略也分别应用于同一风力发电系统中,数字仿真结果表明所提出功率变换器控制策略在中点电位平衡以及网侧功率调节中均可达到满意的效果。同时,由于中点电位不平衡被斩波器所抑制,因此网侧变换器的SVPWM调制算法得到了较大程度的简化。在所提出的功率变换器拓扑中,为了保证Boost三电平斩波器的输入—输出电压满足1/(1-d)的升压关系,分析了相差控制方式下影响斩波器工作模式的主要因素,根据不同工作模式间的临界条件,推导了临界电感的计算方法,并且分析了不同工作模式对输出侧电容纹波的影响。仿真与实验结果验证了理论分析的正确性,进而表明该分析方法对Boost三电平斩波器的设计具有一定参考价值,且具有通用性。此外,针对网侧变换器矢量定向控制策略中PI控制器参数整定过程繁复的特点,结合内模控制的基本原理,简化了PI参数的整定过程。理论分析结果表明,在受控对象为一阶系统的情况下,当采用闭环PI控制时,该PI参数整定方法具有普遍适用性。更多还原

【Abstract】 This paper discusses the significance and development prospect of wind energy and wind power generation under the increasingly serious situation of energy security. A novel topology of power converter which is applied to direct driven wind energy conversion systems (WECSs) based permenant magnetic synchronous generators (PMSGs) is proposed to meet the demand of large capacity WECSs. The stator of generator is connected to a diode rectifier, a diode-clamped three level (TL) inverter is connected to the grid, and a boost TL chopper is set between the rectifier and the TL inverter. Based on this topology, the switch-signal phase-delay control (SSPDC) for the boost TL chopper is put forward to balance the neutrual point (NP) potential of the TL inverter. The NP potential is balanced by adjusting the phased delay betweent the two switching signals of the two power switches in the TL chopper, and the boosting feature of the TL chopper is not changed. The boost TL chopper under the SSPDC is modeled for its controller design.A parallel dual-PI control strategy is designed for the boost TL chopper, as the maximum power point tracking (MPPT) and NP balancing are achieved both by the TL chopper. This strategy is simulated in a typical large capacity WECS, and its feasibility is verified by simulation results. The validity of the proposed NP balancing method is verified furtherly by comparing with two redundant vector selection NP balancing methods which are both simulated in the same WECS. The modulation algorithm of the grid-side TL inverter is simplified a lot as the NP potential is balanced by the boost TL chopper.The main factors on which the operating mode of boost TL choppers depend are ananlyzed for guaranteeing the relationship between the input and output voltage of the TL chopper in the proposed topology. The formulas of critical boosting inductances are deduced according to the critical conditions between different operating modes. The capacitor voltage ripples are also analyzed under different operating modes. The validity of these ananlyses is verified by simulating and experimental results. Furthermore, these ananlyses could be generally used in guiding the design of boost TL choppers.In addition, the PI parameters tuning method for the controllers of the grid-side TL inverter is simplified according to the principle of internal model control (IMC). The ananlysis indicated that the tuning method is generally applicable when controlled plants could be regarded as first-order systems.更多还原