Research On AC Combined Biased Magnetic Bearing For Magnetic Suspension Flywheel

The flywheel energy storage system(FESS) has been widely concerned because it has a lot of advantages such as fast charge, high power density, high energy density, low demands on environment, can be modularized and so on. However, the mechanical friction loss brought by the high speed rotation of flywheel became one of the important factors to limit the development of FESS. Magnetic suspension supporting technology used in FESS can avoid mechanical friction,improve the energy storage efficiency and service life of FESS, make the FESS have a wider application prospect. The AC hybrid magnetic bearing has many advantages such as compact configuration, low power, simple control and so on. It has advantages to use the AC hybrid magnetic bearing into FESS. In this dissertation, the new type of five freedom AC hybrid magnetic bearing was used as the supporting system of FESS. The main research content of this dissertation focus on the structure design, mathematical model and control method of magnetic bearing. The main research contents are as follows:Firstly, based on the basic principle of magnetic suspension FESS, several different kinds of common magnetic suspension supporting structures are proposed. Through the comparative analysis of the advantages and disadvantages of these schemes, a 2-DOF AC hybrid magnetic bearing and a 3-DOF AC hybrid magnetic bearing are finally chosen to support FESS.Secondly, through the analysis and calculation of the magnetic circuit structure, how the biased flux generated by permanent magnet will affect the design of AC hybrid magnetic bearing can be known, and the the advantages and disadvantages of different design can be analyzed.Because the AC hybrid magnetic bearing whose biased flux generated by permanent magnet has some disadvantages, this dissertation propose a combined biased method that the bias flux is generated by permanent magnet and current. The principle and advantages of the combined biased method are represented in detail.Thirdly, designed a 2-DOF AC hybrid magnetic bearing and a 3-DOF AC hybrid magnetic bearing with the combined biased method. The parameters design steps of the 5-DOF magnetic bearing are presented in detail. The mathematical model of suspension force and the size of the DC biased current are deduced. The model of combined biased magnetic bearing is simulated by Ansoft software, demonstrate the validity of the combined biased method. The simulation results show that the suspension force size has reached the design requirements.Finally, the digital control experimental platform of 5-DOF combined biased magnetic bearing is built. The hardware structure, software structure and the debugging process are introduced in detail. The starting up experiment and the disturbance experiment of magnetic bearing are completed and the experimental results are analyzed.