Design On Single Phase On-Line UPS In The Station

With the rapid development of information technology and the increasing popularity of computers, the Uninterruptible Power System (UPS) has been more and more widely applied into all walks of life, specially in precision measurement systems, aviation management systems, medical control systems and other industries. The UPS system is required to ensure continuous power supply and provides high quality stable voltage and frequency, without surge of electric energy. The performance of the whole system of UPS is largely determined by its control section. Therefore, it is important to choose the appropriate control strategy for the system. At present, with the continuous development and improvement of digital control, the control of UPS system is gradually changed from analog control to digital control, which becomes one of the popular research on UPS study.Based on the current research status of on-line UPS, this thesis focuses on how to improve the input power factor and the stability of the system.The function, working principle and working conditions of each modules of on-line UPS system, are theoretically analyzed in detail. Topological structures of the power correction circuit, the inverter circuit and battery charging circuit are analyzed and selected.The control method of power correction circuit and inverter circuit are studied in this thesis. In order to improve the dynamic and steady-state performance of the system, corresponding control algorithms are proposed and introduced into the UPS systems control for practical application:(1)The average current control method of power correction circuit is proposed.(2)The double closed loop control strategy with load feed-forward is proposed, which is based on the load of the inverter, and the parameters of the controller are designed by pole placement. (3)The double closed loop control strategy is used in battery charging circuit.Then, APFC, inverter circuit and battery charging circuit simulation model of the UPS system is set up in the MATLAB software. Various simulation results are analyzed and compared, the power factor and stability are improved, which meet the design requirements.Based on the above study, the primary software design of control part of online UPS system is completed, including the control flow of main program, initialization program, the timer to generate PWM pulse control signal and the interrupt cycle.Finally, combined with practice, the experimental platform is built, and the experiment of the input power factor correction and the inverter of UPS are completed.