Control Strategy Research Of The Flywheel Battery And Application

Flywheel battery is a new type of energy conversion and storage device equipped with high energy, non-pollution and high efficiency, which can be applied to multiple areas such as uninterruptible power supply (UPS), hybrid electric vehicles, electric power system and satellite dual attitude control. It has become an important direction to achieve efficient use of energy and reduce environmental pollution. Aiming at the current situation of unavailable flywheel battery products in China market, the high price of foreign products and the restriction in the development of related technology, the thesis carried out the research on energy conversion, dynamic modeling and control strategy in the processes of charging and discharging. Meanwhile, a power plant simulation platform was build for internal combustion engine rotary uninterruptible power system. This work was supported by the special funds of Ministry of Science and Technology " Electric Power Plant with Internal Combustion Engine Rotary Uninterruptible Power System"(2008EG19914-4). The major research works were carried out by follows:1) Based on the in-depth analysis and comparative study of the scheme about many kinds of power electronic device in flywheel battery energy conversion system and two-way reversible motor selection, the system scheme was designed with dual PWM converter as energy conversion device and the permanent-magnet synchronous as motor drive for flywheel. Based on this scheme, the research was carried out on energy conversion, dynamic modeling and control strategy in the processes of charging and discharging. The mathematical model in d-and q-axes system of flywheel battery was built, and an equivalent circuit model of flywheel battery in charging and discharging has also been presented. These works provided the support for following research.2) On the issues of "pollution" to power grid from flywheel battery rectifier in the charging rectifying link, hysteresis control strategy by direct current control was presented to achieve sinusoidal current of the PWM rectifier side of the flywheel battery and unitization of power factor. In the meantime, considering the large inertia, time-varying, nonlinear characteristics of flywheel battery, a conventional PI or PID controller for speed loop was not satisfied in dynamic stability and susceptible disturbance and impact from system parameter change. Combined with space vector PWM control technology, a kind of exponential reaching law sliding mode variable structure controller was designed. The controller made the system state slide along the sliding surface by switching controlled quantity. It was insured the invariance subjected to an external disturbance and parameter perturbation, improved the dynamic stability and the robustness, and reduced the vibration of the motor.3) On account of the "pollution" to flywheel battery from rectifier in the discharge rectifying link, a feed-forward decoupling control strategy was studied. By means of controlling the current vector and feed-forward compensation, it can realize sinusoidal current of the PWM rectifier side of the flywheel battery and unitization of power factor, as well as reduce the "pollution" to flywheel motor from rectification device. Considering the complexity and diversity of flywheel battery load, conventional PI or PID controller for output voltage loop was not content. A compact format model-free adaptive controller was designed, which depended only on the input and output data from controlled system and without mathematic model. This strategy enhanced the flywheel battery’s adaptability to all kinds of load and reduced output voltage waveform distortion caused by modern load, and improved the quality of power supply.4) Based on the energy conversion dynamic relationship modeling, research of control strategy and verification of simulation results of the flywheel battery, through the analysis of the structure and working principle of the internal combustion engine power station rotating uninterrupted power supply, a power of3kW simulation experiment platform was built by microprocessor dsPIC30F3011and programmable controller S7-200(CUP224) as core components. And the PC centralized monitoring system has also been developed with Ethernet as the communication medium and VB as a programming tool. The critical proposed control theories about the flywheel battery side PWM rectifier charging/discharging have been carried out on the platform. The experiments further validated the feasibility, effectiveness and engineering usability of system scheme and control strategy.