多相无刷双馈发电机及其控制系统基础研究

With the development of wind power generation technique, the unit capacity of wind power generation turbines is becoming larger. The higher requirement on reliability and performance-price ratio of generator is needed. But the existing generator, such as variable speed constant frequency (VSCF) brush doubly-fed generator (BDFG) and the permanent magnet synchronous generator (PMSG) which are widely applied on high power wind turbines today can not well satisfy the requirement of this development trend at present. Because both of them have some disadvantages such as low reliability, or high price, and so on. The Brushless doubly-fed generator (BLDFG) has the outstanding advantages, such as high reliability, high system efficiency and low system cost compared with BDFG and PMSG. So I am sure that BLDFG will be very suitable applied for wind turbines. A novel multiphase brushless doubly fed generator (MP-BLDFG), which is especially suitable for high voltage and large capacity, is proposed in this project at first time. Meanwhile, a matched power converter is proposed. To improve the efficiency of MP-BLDFG, the windings of rotor must be used "repeatly"。So a novel rotor winding design method based on MMF superposition principle is proposed too. According to this method, two MMF waveforms which have different pole pairs number and have reverse rotation direction can be realized with the same rotor winding. Specially, when the amplitude of two MMF waveforms are equal, the integration waveform is a standing wave, which can reduce loss and improve efficiency of the MP-BLDFG. According to proposed scalar control method, the independent control of reactive and active power of MP-BLDFG is realized. According to this project, we hope that the BLDFG can be applied at wind power generation turbines well, especially with high voltage and great power field. The academic value and practical engineering value will be very significant if this proposed project can be supported and can be finished successfully.

风力发电机组的单机容量越来越大，对发电机的可靠性和成本等要求也越来越高。目前广泛应用的变速恒频有刷双馈发电机可靠性不高，而永磁同步发电机成本较高。无刷双馈发电机实现了无刷化且功率变换器的容量接近于有刷方案。因此无论从可靠性，效率还是成本等各方面看，无刷双馈风力发电方案的竞争优势均十分明显。本项目首次提出一种多相无刷双馈发电机及其配套的多相功率变换器方案，特别适用于高压大容量场合的风力发电应用。另外，依据磁势叠加原理，首次提出了一种应用于绕线转子的绕组复用设计方法，采用一套绕组可同时实现两种不同极数且旋转方向相反的磁势。当这两种磁势的幅值相等时，转子合成磁势呈现出驻波磁势的特征，这时电机的效率和功率密度均较高。另外通过一种标量控制算法，解决了发电机在并网时的有功和无功功率的独立控制问题。本项目研究成果将推动无刷双馈发电机在高压大功率领域的工程化应用，同时具有重要的学术价值。

在一些应用场合，发电机的转速不一定恒定，如风力发电、船舶轴带发电、小型水力发电等。本项目提出了一种双三相无刷双馈发电机，可以实现变速恒频的发电目标。该电机的特点是定子上除了有一套三相功率绕组外，还有两套空间上互差30度且中性点独立的控制绕组。转子上也设计有绕组进行磁场调制，可以实现用一套绕组产生两种极对数不同且磁场旋转方向相反的磁场调制功能。.主要研究内容包括：1）研究了双三相无刷双馈发电机的原理，包括转子上如何采用一套绕组实现两种不同极对数且旋转磁场相反的磁势的方法；2）建立了该电机的数学模型；3）研究了双三相无刷双馈电机的电流控制算法；4）研究了无刷双馈发电机的无编码器控制算法，包括独立发电以及并网条件下的控制算法；5）研究了双三相绕组的载波移相控制方法；6）设计并制作了一台2/6极双三相无刷双馈发电机样机，以及一套相应的控制装置，进行了仿真和实验研究。.重要研究结果：1）所提出的双三相无刷双馈发电机原理上是可行的，但在转矩密度等重要指标上仍比常规电机要差一些；2）两套控制绕组的相轴在空间上互差30度后，电流时序上也应相差30度；3）两套控制绕组逆变器的载波可以移相90度，这样可以有效降低功率绕组输出电压波形中的高次谐波；4）双三相无刷双馈发电机可以采用无位置编码器控制，在独立发电条件下可实现对功率绕组电压和频率的有效控制，在并网发电条件下可实现对发电的有功功率和无功功率的有效控制。.科学意义：所提出的双三相无刷双馈发电机及配套的控制系统可以应用于风力发电、船舶轴带发电等变速恒频发电领域。由于转子上取消了滑环和电刷，因此电机的可靠性较高，又由于配套的电力电子变换器的功率仅为电机总功率的一部分（取决于转速范围），因此总的系统成本也相对有一定优势。另外多相化还可以帮助解决系统的电磁干扰问题，并有助于提高电机的绕组系数，降低电机控制绕组中的5次和7次谐波磁势。