【作者】 王雅玲；

【导师】 徐衍亮；

【作者基本信息】 山东大学 ， 电机与电器， 2014， 博士

【摘要】 随着环境污染及石油危机的加剧,电动汽车的研发得到广泛重视,在目前车载蓄电池技术未得突破的前提下,电动汽车的电驱动系统是研究重点,显然电动汽车的电驱动系统依赖于不同类型的驱动电机。尽管永磁无刷电机在电动汽车驱动中具有综合优势,但其固有的难以实现弱磁扩速,从而难以实现较低逆变器容量下的低速大转矩和高速小转矩输出的缺陷,影响到电动汽车性能的进一步提高。因此,随着电动汽车对电机性能要求的不断提高,需要开发研究具有新结构、新概念的驱动电机。双定子永磁无刷电机是近几年提出的一种新型永磁无刷电机,因其具有双定子结构,大大改善了传统永磁无刷电机的性能,在电动汽车驱动中具有重要应用价值,目前对该种电机的研究相对较少,因此本文基于电动汽车应用对双定子永磁无刷电机进行深入分析研究,主要包括以下几部分内容：(1)分析了双定子永磁无刷电机适合用于电动汽车驱动的结构原理及其性能的优越性。双定子永磁无刷电机由内定子、中间转子、外定子嵌套而成,可以看作是一个外转子永磁无刷电机和一个内转子永磁无刷电机的合成。与传统的单定子永磁无刷电机相比,双定子永磁无刷电机不但具有一般永磁无刷电机的优点,且在相同的体积下,当内、外定子绕组共同作用时将具有更高的功率密度。当用作发电机时,可以提高电机的发电能力；当用作电动机时,可以提高电机的转矩输出能力。通过分析各种双定子永磁无刷电机的结构形式,得出串联磁路表贴式结构具有更适合电动汽车应用的性能优势：其转子铁心轭部圆周方向没有主磁通,在机械强度允许范围内转子铁心轭部可以很薄,从而减少电机的体积和重量。双定子永磁无刷电机的内、外定子上绕有独立的定子绕组,通常外定子绕组匝数多于内定子绕组匝数,因此,两套绕组既可串联运行,又可单独运行。当内、外定子绕组串联运行时,每相绕组有效串联匝数多,反电动势高,同时转折转速低,且产生较大的电磁转矩,从而能够很好的满足电动汽车低速爬坡及起动加速的要求。当外或内定子绕组单独运行时,每相绕组有效串联匝数少,反电动势低,产生的电磁转矩较小,但转折转速高,使电机能够高速运行,因此即使不经过弱磁扩速,电机也能达到较高的转速。而且当电机一套绕组出现故障时,另一套绕组可以单独运行,使电动汽车驱动具有容错性。同时,通过灵活控制绕组的连接方式,可使电机运行在不同工况下以满足电动汽车不同运行状态的需求。(2)根据双定子永磁无刷电机的结构特点,提出了一种双定子永磁无刷电机的设计方法。串联磁路表贴式结构的双定子永磁无刷电机因其双定子结构而具有优越的性能,但电机的结构更加复杂了,不仅内、外定子设计参数相互制约,其内、外定子间还存在电磁耦合关系,这大大增加了电机的设计难度,难以采用现有的设计手段对其进行电磁设计,从而限制了该种电机的深入研究和推广应用。因此,本文基于双定子永磁无刷电机的结构特点,提出了一种双定子永磁无刷电机的设计方法,即将双定子永磁无刷电机看作内、外两个单定子永磁无刷电机进行单独设计,然后合成为双定子永磁无刷电机设计方案。由于设计过程中涉及到内、外单定子电机设计参数的匹配,为了加快设计过程,并得到更为合理的设计方案,在设计过程中加入了响应面法和遗传算法进行优化。该方法对设计双定子永磁无刷发电机和电动机同样适用。本文以双定子永磁同步发电机为例,详细介绍了设计方法及设计过程,对最终的设计方案进行了有限元分析并制作了样机进行实验,验证了设计方法的正确性。(3)通过对双定子永磁无刷电动机的性能分析,提出了该种电机应用于电动汽车驱动时绕组连接方式的选择原则。本文首先设计了一台用于电动汽车驱动的双定子永磁无刷直流电动机,并对不同绕组连接方式下电机的性能进行了电磁场有限元分析,得到了相同逆变器供电时电机的三个额定工作点,即转折转速点,从而得到了双定子永磁无刷直流电动机的转矩转速曲线。其次,进一步对该电机的各运行区域进行细分,并对各运行区域内不同绕组连接方式下电机的性能进行有限元分析,得到了各运行区域内不同绕组连接方式下电机性能的优劣顺序。进而提出了双定子永磁无刷直流电动机基于电动汽车不同运行工况的绕组连接方式选择原则,使电机不仅具有较宽的运行范围,且在较宽的运行范围内能够高效运行,以满足电动汽车驱动系统的要求。最后制作了样机进行了实验验证。(4)提出了双定子永磁无刷电动机绕组连接方式的切换方法及绕组换接电路,并分析了绕组换接的动态过程。为了满足电动汽车不同运行工况的需求并使电机在各运行工况下具有高效率,需要合理的进行绕组连接方式的切换。经分析,常用的绕组换接方法需将电机电流降至零或接近零时进行绕组切换,换接过程会出现电流和转矩的明显中断。为了避免电流和转矩中断现象、降低绕组换接过程对电机正常运行的影响,本文提出了在电机各相绕组电流过零点时依次进行绕组切换的绕组换接方法,并提出了基于双向晶闸管的绕组换接电路。首先,为了降低控制系统的复杂性,选用双向晶闸管作为绕组换接电路的开关元件,给出了双定子永磁无刷电动机的绕组换接电路。其次,以方波电流驱动的双定子永磁无刷直流电动机和正弦波电流驱动的双定子永磁同步电动机为例,分别对绕组换接的动态过程进行了理论分析。最后,利用有限元仿真软件分别建立了两电机的场路耦合时步有限元仿真模型,对绕组换接的动态过程进行了有限元仿真,验证了绕组换接方法及绕组换接电路的可行性。更多还原

【Abstract】 With the intensification of the environmental pollution and oil crisis, widespread concern is focused on the research and development of electric vehicles. Unfortunately, the breakthrough of the vehicle-mounted batteries is still not achieved. So the electrical drive system is still the the key of the research. Evidently, the electrical drive system depends on different driving motor types. According to the demand analyses for electric vehicles’ drive motor, the permanent magnet brushless motors are predominant in the appliances. However, the indigenous permanent magnet structure of the motors impedes the flux weakening speed regulation; moreover, the low-speed-high-torque and the high-speed-low-torque operations are usually unattainable under a low capacity inverter. Accordingly, in pace with the continuously upgrades of the electric vehicles’ performances and other demands, the permanent magnet motors with new structures and new concepts are desired. In recent years, a dual-stator permanent magnet brushless motor is proposed, which significantly promotes the motor performances due to the dual-stator structure. At present, the novel dual-stator motors are sparsely carried out in applications or researches. Therefore, the aim of this dissertation is to carry out an in-depth study into the dual-stator permanent magnet brushless motor’s applications in electric vehicles.The main contents of this study are divided as follows:(1) Analyses on the dual-stator motor’s structural principle and on its predominant performances in electric vehicle applications.The dual-stator motor comprises an inner stator, an intermediate rotor, and an outer stator. The total structure can be regard as a combination of an inner-rotor motor and an outer-rotor motor, and is more complicated than a conventional permanent magnet brushless motor. Except inheriting the advantages of the conventional permanent magnet brushless motors, the dual-stator motor attains a much higher power density under the same volume. Furthermore, when the dual-stator motor operates in the generator mode, it could promote the generating capacity; when the motor operates in the motor mode, it could multiply the torque outputs. Analyzing through the characteristics of the typical rotor structures, the surface-mounted series magnetic circuit structure is identified to be of the least material usage and the smallest volume and weight. Because, little magnetic flux passes through the yoke of the rotor core in the circumferential direction, giving the allowance for a very thin rotor yoke that just depends on the mechanical strength.The windings in the inner and outer stators are independent, and the winding turns of the outer stator usually outnumbers that of the inner stator. The windings of both stators can be connected either in series or independently. If both windings are connected in series, the number of turns per phase is increased, bringing about an increased phase EMF and a reduced base speed. And this kind of connection also produces a high electromagnetic torque, which is beneficial for the low-speed-high-torque operation. If the windings are used independently, the number of turns per phase is decreased, bringing about a decreased phase EMF and electromagnetic torque but a high base speed. This kind of connection realizes a high speed operation without the flux weakening speed regulation. Besides, if one of the independent windings breaks down, the other winding can still maintain the motor fault-tolerance running independently. Therefore, according to the multiple winding connections, the dual-stator motor can work under various operating conditions and provide more flexibility for the electric vehicles drive.(2) According to the structural features of the dual-stator permanent magnet brushless motors, a design method of the dual-stator permanent magnet brushless motor is proposed.The dual-stator permanent magnet brushless motor with surface-mounted series magnetic circuit has a complex structure, which not only has the mutual restrained design parameters between the inner and outer stators, but also has the electromagnetic coupling of the inner and outer stators. It means that this kind of motors is difficult to be designed by available design methods, which is restricting their popularity. Accordingly, based on the structural features of the dual-stator permanent magnet brushless motor, a design method is proposed, regarding the dual-stator permanent magnet brushless motor as individual inner and outer single-stator motors, and then, compounding the two individual motor schemes into the final design scheme of the dual-stator permanent magnet brushless motor. As to the parameters matching between the inner and outer motor, the optimization algorithms such as the response surface method (RSM) and genetic algorithm (GA) are applied to achieve a faster design procedure and a more rational result. This method can be used both in the design of dual-stator permanent magnet brushless generator and dual-stator permanent magnet brushless motor. Taking a dual-stator permanent magnet synchronous generator’s design as an example, this dissertation amply introduces the design method and procedure, and then the design scheme is verified by the finite element analysis (FEA) and prototype machine experiments.(3) According to the analyses of the dual-stator permanent magnet brushless motor’s performances, the principles for selecting the connection modes of the inner and outer windings are proposed, when the motor is used in electric vehicle.Basing on the dual-stator permanent magnet brushless DC motor designed for electric vehicles, this dissertation performed the FEA on the motor with different winding connection modes. Then, the torque-speed curve is charted based on the three rated operating points. Furthermore, the operating region is subdivided, and under each operating subdivision, the performances of the motor with different winding connection modes are analyzed by the FEA. According to result, it can obviously determine which winding connection mode has the optimal performances under various operating states. Then, the principles for selecting the connection modes are obtained to adjust the motor working in a wide operation region with high efficiency, which is satisfying the demands of the electric vehicles’ drive system. At last, the experiments are carried on the prototype machine.(4) The winding switching method of the dual-stator permanent magnet brushless motor is proposed, and the winding switching dynamic procedure is analyzed.In order to maintain a high efficiency under different operating states of the electric vehicles, the winding connection modes of the motor should be rationally switched. According to the analyses, the common method is to adjusting the all currents of the motor reducing to zero or nearly zero before the winding switching, which causes significant interrupt to the current and the electromagnetic torque. In order to avoid the interrupt state, this dissertation proposes a winding switching method that every phase winding should be successively switched when every phase current is crossing zero. The whole control system of the dual-stator permanent magnet brushless motor with the winding switching circuit is designed, and in the winding switching circuit, the triode AC switches (TRIAC) are utilized as switches to reduce the complexity of the circuits. Individually, taking a square-wave driven dual-stator permanent magnet brushless DC motor and a sine-wave driven dual-stator permanent magnet synchronous motor as examples, the winding switching dynamic procedures are analyzed. And the results of the field-circuit coupled time-step FEA show that the winding switching method and circuit are feasible.更多还原