Control Of Flywheel Energy Storage System And Its Application In Wave Power Generation

Compared with other energy storage methods, flywheel energy storage system(FESS) has many advantages such as high energy density, high efficiency, fast response speed, long life, and without being limited to the geographical environment.So it is one of the most promising energy storage technology, and has a very broad application prospect. The drive machine and power electronic converter play important roles in FESS. Whether the drive machine can smoothly switch between the generator and the motor operation modes and work steadily and safely with low loss determines the success of the whole system, so the choice of drive machine has vital significance. The structure and control system design of the power electronic converter is also very important, for it is responsible for energy transfer and connecting each unit of the whole system.In the ocean, ideal waves are close to periodic sine waves, so the output active power is unstable. FESS is very suitable for high power discharge in short time and frequent charging and discharging. So large fluctuation of wave energy converter's output power can be well solved if these two technologies are combined.In this paper, a flywheel energy storage system based on a switched reluctance machine(SRM) is studied, and the contribution is mainly as follows:(1) The working principle, technical advantages, key technologies, and the development at home and abroad of the flywheel energy storage device are introduced.(2) A flywheel energy storage system based on SRM is designed and the working principle and selective basis of each part are given.(3)Simulation models of the flywheel energy storage system charging and discharging are build, and control methods of fast charging, charging based on the given power from the grid, supplying power to the load independently as an UPS, and transmitting electricity to the grid as the given power are given. The results verify the effectiveness of the proposed control methods.(4) A float-type wave power generation system with the proposed flywheel energy storage unit is built according to the wave characteristics in the coastal area in Tianjin. In order to describe the characteristic of wave power system's output activepower, an active power smoothing coefficient F is defined. A control method of flywheel energy storage unit is proposed to dampen fluctuation of the wave power system's output power. Simulation results validate the FESS's ability to suppress the power fluctuation and reduce its impact on the grid.