Research On Single-Phase Series-Parallel Compensated UPS Characteristics Based On Full-Bridge Bidirectional High-Frequency Isolated

With the development of the national high and new technology industry,the demand for the power quality of the enterprise's production equipment is becoming more and more severe.The sudden drop,the distortion or even the power off of the grid voltage will seriously affect the safe and stable operation of the electric equipment.Uninterrupted Power Supply(UPS)emerges as the times require to meet the requirements of power users for power quality and ensure uninterrupted power supply for key users.At present,the series and parallel compensation UPS is widely used in the market.However,the use of the power frequency transformer makes it larger and increases the weight of the system,which is not conducive to the realization of high frequency and modularization.The circuit topology of single phase series compensated UPS based on bi-directional full bridge high frequency isolation is studied in this paper.The circuit topology of UPS is also studied..In this paper,the structure and function of the high frequency isolated single-phase serial parallel compensation UPS are analyzed,and the direct control strategy and the indirect control strategy are compared and analyzed.It is pointed out that the direct control strategy that the series converter is controlled by a sinusoidal current source and the parallel converter as the sinusoidal voltage source is more suitable for the UPS control scheme.The switching control mode is used to supply the power directly to the load.Based on the direct control strategy,the working principle of the system and the energy flow of the system under different state of the power grid condition are analyzed,and the charge and discharge of the battery in different state of the power grid is studied.In order to realize the control targets of the bidirectional flow of energy,the constant output power and the unit power factor of the power grid,the mathematical modeling of the series,parallel and two-way full bridge high frequency isolation DC-DC converter is carried out respectively,and the corresponding control strategy is given according to the mathematical model and the control target of the converter.Onthe basis of the mathematical model of the parallel converter,the control strategy adapted to the different load conditions is proposed.The theoretical analysis and simulation verification of the double closed loop PI and the quasi PR control are carried out.Based on the mathematical model of the series converter,the calculation method of the grid current reference value and the control strategy of the high voltage side DC bus voltage are given.The three phase shift control strategy is applied to the bidirectional DC-DC converter,which can make the control of the system more flexible,reduce the reflux power of the system and expand the soft switching range of the system.Then,the power transmission,reactive circulation and soft switching specificity of the bidirectional DC-DC converter are analyzed.Finally,the MATLAB/Simulink is used to simulate the single-phase series and compensation UPS,and the experimental platform based on DSP TMS320F28335 is built,and the hardware parameters of the system are given.Simulation and experimental results verify the feasibility of the proposed topology,the correctness of theoretical analysis and the effectiveness of control strategy.