| Flywheel energy storage system is a kind of novel electromechanical energy conversion device with several advantages, including long-life, high efficiency, strong adaptablility and no pollution etc. There is extensive application foreground in mang fields, such as aerospace, distributed electricity generation, electric power peak adjustion, and electromotion vehicle so on. Flywheel energy storage technology is a kind of cross technology with several high and new technology, including magnetic suspension technology, high speed electric machine technology, vacuum technology, power electronics technology and composite material technology etc., and it is deemed to be one of the most valuable energy storage technology, so, the relative study content is very abundant. The research task of this paper comes from the Key Science and Technology Research Project of Shenzhen City Government——Early Research of Distributed Self-determination Energy System, and the main study contents of this paper include three parts: magnetic suspension bearing, motor/generator for flywheel energy storage(flywheel electric machine for energy storage) and control of flywheel electric machine drive system for energy storage.Magnetic suspension bearing technology is one of the key technologies of flywheel energy storage. This project proposes full passive magnetic suspension bearing structure which consisits of axial permanent-magnet suspension bearing and radial passive electromotive magnetic suspension bearing to remove abrasion and lubrication of traditional bearing. Axial permanent-magnet bearing is used to support the mass of flywheel rotor, radial passive electromotive magnetic bearing is used to keep radial stable suspension of flywheel. There are many delightful research achievements of passive electromotive magnetic bearing in linear-motion occasion, but the research of passive electromotive magnetic bearing is in initial starting stage in rotating occasion, and it is a difficult point of magnetic bearing field. This paper proposes a new stucture of passive electromotive magnetic bearing which inclues two parts: stator supplys repulsive magnetic field, and rotor selects single-layer 8-shape coil structure or double-layer 8-shape coil structure. And then several contents which include characteristics of repulsive magnetic field, force of 8-shape coil, force of rotor, and stabilization of bearing etc., are studied with theoretical analysis scheme and finite element analysis(FEA) scheme. Finally, a prototype and a test device for radial passive electromotive magnetic bearing is designed to validate theory analysis and simulation study; this device can assemble rotor to implement high speed rotation, conveniently observe movement process of stator, and measure the relative data between departure length and force of stator.Flywheel electric machine for energy storage which is the carrier of energy between electrical energy and mechanical energy is another key part of flywheel energy storage. Ironless permanent magnet square-wave flywheel electric machine is selected in this paper to improve some characteristics of energy storage system, such as efficiency, integration level etc. This type of electric machine has no copper loss of rotor and no iron loss of stator, so, the main loss is winding eddy loss without load, and the main loss includes winding loss and rotor eddy loss with full load. Theory estimation calculation model is modeled to reduce winding eddy loss, and the winding eddy loss of a prototype is estimated with the proposed model, finally validated by experiment of free halt. The rotor eddy loss maily comes from armature reaction, and the field resolution scheme is proposed using equivalent current layer which includes inner layer and outer layer to get the distribution of armature reaction field; to reduce rotor eddy loss and obtain high efficiency, the principle of loss caused by space harmonics and time harmonics is analyzed in detail, then, a experimental scheme to measure rotor eddy loss by changing windage loss is propsed, and the experiment results compare with FEA calculation results to validate the proposed experiment scheme, furthermore, the reliability of FEA calculation is also demonstrated.During the charge period, ironless permanent magnet square-wave brushless electric machine is difficult to drive because the little phase-inductance causes large steady-state current ripple with PWM control scheme; furthermore, large phase-conversion current ripple will be produced while the motor/generator is driven by square-wave control scheme. So, the large steady-state current ripple and large phase-conversion current ripple will increase the control difficulty. This paper proposes a novel control scheme including double-frequency PWM(pulse width modulation) square-wave control and DC voltage adjustion to reduce steady-state current ripple, and the proposed scheme is validated by Matlab simulation and experiment. Then, novel three-phase inverter and bus current detecting shceme which are to obtain all current information are proposed to reduce phase-conversion current ripple of square-wave motor, and the proposed scheme is also validated by Matlab simulation and experiment. During the discharge period, the output voltage decreases with the speed of electric machine, which increases the control difficulty for discharge. So, a converter for discharge which includes a Boost circuit and a single-phase inverter circuit is presented to obtain stable and safety output, and the proposed scheme is also validated by Matlab simulation.Finally, a digital minimum drive system for electric machine drive of flywheel energy storage based on TMS320F2812 DSP is designed. To satisfy control requirement of flywheel energy storage system, this paper mainly introduces hardware design and software design, and experimental research of flywheel energy storage system prototype is implemented with the minimum system, then experimental results compare with simulation results to validate practicability of system control scheme.
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