Research On Dual-Stator Winding Multi-Phase High-Speed Induction Generator With Rectifier Load

The dual-stator winding multi-phase high-speed induction generator with a rectifier load is characterized with high power density, good electric supply quality, reliable operating performance, and convenient adjustment. It represents the development tendency of the power generation block in ship's integrated power systems. To meet the requirements of minimizing the machine size, improving the mechanical strength, reducing the noise, and enhancing the electromagnetic compatibility, the stator of this novel induction generator has two embedded windings. The two windings include a 12-phase power winding connected to a rectifier load and a 3-phase control winding connected to a static excitation regulator respectively. It has a squirrel-cage solid rotor. Also, there are the capacitors for self-excitation and the inter-phase reactors in the system for performance improvement. With the configuration of multi-loop, variable-topology, and nonlinear magnetic/electric circuits, the complex system covers many subjects, i.e. electric machinery, power systems, power electronics, control theory, etc.An incidence matrix method is introduced to compute the system parameter for the first time. A unified algorithm is developed to calculate hundreds of the slot leakage inductances, harmonic leakage inductances, and end-winding leakage inductances among 15 phase windings, which lays the foundation for performance calculation of the induction generator system.The electromagnetic field finite element method, combined with the variable iteration, is carried out to obtain the self-excitation capacitance of the 12-phase induction generator. That the calculated result matches the actual one confirms the correctness of the presented method.The expression of the relation between the order of the time harmonics of the currents flowing through a 12-phase winding and the order of the space harmonics of the resulting MMF is revealed. It is a new idea that if only thefundamental MMF is considered, the whole system can be divided into two sub-systems linked by the terminal variables only. For one sub-system of the 12-phase power winding with a rectifier load, the loop current method, based on the network graph theory, is performed to establish the variable-topology network equations in a matrix form. To solve those time-dependent equations, the numerical stability is attained by alternating use of the fixed time-step and the varying time-step. The calculated results, such as the winding currents, voltages, etc, well checked with the experimental ones at three load points. It indicates that the newly proposed method is of high accuracy.For the other sub-system of the induction generator with dual-stator winding and cage solid rotor, the finite element method is used for the electromagnetic field analysis. The analysis determines the control winding current and frequency with a multi-variable optimization approach. The calculated values of the control winding current and the stator frequency well match the experimental values. The impacts of the rotor structure and the parameters outside the induction generator system on operating performances are also investigated. Three different rotors are compared with the original copper-bar cage solid rotor. They are the lamination rotor with the copper-bars, the solid rotor without the cage, and the solid rotor with the brass bars. The computation of the reactive powers of the control winding and the rotor losses illustrates that the original copper bar solid rotor is a good choice. The reactive powers for the different inter-phase inductances and self-excitation capacitances are compared, so that the right values of the inductances and capacitances can be determined.