基于有气隙感应式旋转变压器的交流励磁无刷双馈风力发电机研究

Doubly fed induction generators are widely used in wind power system. The presence of brushes and slip rings debases the performance of the ordinary ac-excited doubly fed induction generator and increases the maintenance costs. This item brings forward a new type brushless doubly fed induction generator, in which a special transformer is used to substitute brushes and slip rings for avoiding mechanical contact between rotating electric circuits. The generators maintenance can be drastically reduced and the installation of wound rotor doubly fed induction machines on explosive environments becomes possible. The transformer has the particularity of an air gap to permit movement between primary and secondary annular windings totally involved by the core which is made by SMC, which would reduce the magnetic hysteresis loss and improve the transmission efficiency of the transformer. By connecting the secondary windings to the rotor windings of the induction generator, it is possible to control the machine to operate at almost any speed. The topology study will be made on the special structure of the three-phase transformer to reduce the leak magnetic field and ensure the balance of phases. The equivalent circuit of the transformer will be established by three-dimensional equivalent reluctance meshwork method. Considering the voltage drop produced by the transformer, the union equivalent circuit of the doubly-fed three-phase induction generator system with a rotating inductive transformer will be established to calculate the parameters and analysis the machine. The dynamic-state model that enables performance prediction of the double-fed three-phase induction generator with a rotating inductive transformer will be provided to analysis the influences of the transformer on the system. Moreover, this solution keeps all the benefits inherent to the use of induction machine rotor circuit for machine controlling. The controlling strategy combined by the differential control and fuzzy control will be put forward to cooperate with it, while ensuring constant based on the generator output frequency to minimize system power consumption. The project would give good expectations about using doubly fed induction machine with an air-gap inductive transformer as wind power generators.

双馈感应发电机在风力发电领域具有广泛的应用前景。由于普通交流励磁双馈风力发电机存在电刷-滑环结构，使其运行可靠性差，维护成本高，无法在恶劣条件下应用。本项目提出一种新型的无刷双馈感应发电机，采用由能相对运动的有气隙感应式变压器替代电刷-滑环结构，实现对电机转子绕组的控制，降低了维护成本，提高了电机运行可靠性，扩大了应用范围；利用软磁复合材料构建变压器原、副边铁心，绕组采用环形结构，减小磁滞损耗，提高变压器传输效率，减小发电机系统损耗；采用三维等效磁阻网络法建立双馈发电机系统统一等效电路，建立其动态模型并进行相应的理论分析和试验研究；采用差动控制和模糊控制相结合的控制策略，在保证发电机输出频率恒定基础上最大限度降低了系统功耗。本项目的研究将解决交流励磁双馈风力发电机由于电刷和滑环带来的维护和成本问题，降低风力发电成本，提高系统稳定性，为新型无刷双馈风力发电机的应用奠定理论和实验基础。

由于普通交流励磁双馈风力发电机存在电刷-滑环结构，使其运行可靠性差，维护成本高，无法在恶劣条件下应用。本课题针对这种情况，基于感应式电能传输原理，结合传统变压器结构，提出一种基于有气隙旋转变压器的无刷双馈风力发电机，主要的研究内容和成果包括：提出了感应式有气隙旋转变压器的新型拓扑结构，替代电刷-滑环结构，实现对电机转子绕组的控制，降低了维护成本；系统研究了感应式旋转变压器内在的电磁关系和机理，全面分析了气隙几何尺寸参数对变压器能量传输效率以及变压器动、稳态性能的影响；根据拓扑结构不同，分别建立了各相独立的单相旋转变压器和三相共铁芯结构的旋转变压器磁路模型并进行了理论分析，导出准确的等效磁路和解析计算方法，实现了稳态性能的准确计算；基于单目标遗传算法，对旋转变压器主要尺寸进行了优化设计；考虑到感应式旋转变压器对发电机功率因数的影响，提出功率因数补偿方法，确定了单边补偿和双边补偿方式下补偿电容，研究了谐振补偿电容参数与变压器运行频率及变压器转子部分转速的关系；为了与变压器模型连接，实现新型的无刷双馈感应发电机的全面设计与分析计算，推导了三相感应发电机数学计算模型，并将变压器等效电路和发电机等效电路结合，构建了统一的系统等效电路，对该电机系统进行了研究，系统分析了转速与电流、功率因数等电机特性参数的关系；利用函数逆P-集合与它生成逆P-信息规律及其特征，逆P-信息规律推理及其推理结构，提出了利用逆P-信息规律推理确定电机控制参数的方法；设计并制造了3kVA旋转变压器样机，进行了样机试验，对理论分析进行了验证，并提出完整的旋转变压器设计规律，替代电刷-滑环结构，降低双馈风力发电机的维护和运行成本。此外，以无刷发电机研究为基础，本项目还对三相无刷混合励磁同步发电机进行了研究，提出了一种基于辅助绕组电流控制的全波感应励磁同步发电机结构，显著提高了电机的励磁效率。