Research And Design On Digital Standby UPS System

With the information technology developing,the capacity,quality and reliability requirement for power is higher and higher,and the UPS has great advantage as the power supply equipment to provide uninterrupted power for power consumption equipment.The inverter occupies an important position as the core of the UPS.The parallel-connected inverters can increase the capacity,achieve the redundant operation and improve the reliability of power supply system.So it is quite significant to study the inverter.The control strategy of the UPS inverter and the parallel control technology of inverters are studied in this thesis.When the grid is normal,it provides power for the power consumption equipment with the UPS tracking the phase of the grid.When the grid fails or the power consumption equipment need to be removed from the grid,the UPS provides frequency ac voltage power for the power consumption equipment.In digital dual-loop control with outer voltage loop and inner current loop,the inner current loop can be used to increase system's bandwidth,accelerate the dynamic response,enhance the adjustment of the nonlinear load disturbance,reduce the harmonic distortion and improve the quality of output voltage.Besides,the parameters are easy to be adjusted and the anti-interference ability is relatively strong,so the double closed-loop PID control is adopted as the control strategy of the UPS inverter in this thesis.The amplitude and the phase of the inverters' output voltage must keep the same as the grid in order to suppress the circulating current in parallel-connected inverters and they are regulated by the active power and the reactive power in this thesis.What's more,the phase lock is studied.In the parallel-connected system,the main inverter tracks the phase of the grid and provides a phase reference standard for the slaved inverters,while the slaved inverters track the phase reference standard to achieve phase synchronism.The feasibility of the control method is verified based on the simulation of the control strategy.The experiment platform of the UPS system is built,and at the same time,the main circuit and the waves of them are tested and verified.The system runs steadily and the quality of output waves is good.