Research On Load Side Converter Of Shaft Power Generation System Using Brushless Doubly Fed Generator

As the traditional fossil energy reserves are less and less, we are pursuring the efficient use of energy. In the ship industry, more and more ships are beginning to use the shaft power generation technology to improve energy utilization efficiency and reduce economic cost. In shaft power generation systems, it is essential to choose shaft generators. The brushless doubly fed generator(BDFG) is very fit for this kind of generation system due to its cancellation of the brush and slip ring which can improve its reliability and safty, so more and more attention is paid to BDFG. Therefore, in this paper, we do a systematic study on the control strategy of load side converter in the shaft power generation systems using BDFG.As BDFG is a new type of electric machine, firstly we illustrate the working principle of it, and then establish the steady-state equivalent circuit which can help us derive the energy relationship between the control windings and power windings. Then we establish mathematical model of BDFG in the three-phase static coordinate and rotating coordinates, and obtain its vector equivalent circuit. At last, we establish the simulation model of BDFG in Plecs, and simulations verify the validity of the model.Then we give the mathematical model of the load side converter(LSC),and according to the control target, the controller is well designed. We also design the starting strategy and reactive power compensation strategy of LSC which can be used in stand-alone power generation systems. At last, simulation verification is carried out in the Plecs simulation software. We first simulate the LSC in Plecs to verify the control strategy. With the machine side converter(MSC) using scalar control, we also cascade the MSC and LSC in Plecs to model the actual systems.In view of load voltage harmonic content being high in the stand-alone power generation systems, firstly we analyzed its causes. On this basis, we put forward a variety of filter circuits, and choose the best through comparison. But the filter may make a system unstable, we proposed the passive damping method and no damping resistor method based on the digital control to improve the stability. Finally, the validity of the methods is verified by simulation and experiment.Finally, we build an experimental platform of BDFG variable speed constant frequency stand-alone generation system, and program in C language in DSP controllers. Through the experiment, we obtain the ideal steady state and dynamic performance, which verifies the truth of the above theory.