Study On Storage Battery's Charging In UPS

The valve-regulated lead-acid battery becomes more and more widely used because of its excellent performances. Storage battery's charge and discharge is a very electrochemistry process. Its life is only half of which is declared by its manufactures because of simple charging algorithms. Try to extend the battery's life, we must adopt reasonable charging algorithms and build a perfect management system. This paper described the use of valve-regulated lead-acid batteries in Uninterruptible Power Supply System including the research on charging algorithms and the design of the charging system.Chapter 2 researched into the topological structure which consisted of a 12-Puls Rectifier and a double-buck reduction voltage circuit. The two circuits'principles of work were analyzed and the main electronic devices'parameters were designed. The 12-Puls Rectifier has more advantages compared with ordinary rectifiers, because the harmonic orders of its output are higher. The double-buck circuit has improved system reliability. When one of two switches is out of work, the other one can ensure the system's operation.Chapter 3 expounded the control strategy of the charging system. Based on the analysis of the charging theory and the investigation of many charging methods, a two-stage charging strategy with method of constant-voltage limitary-current was brought forward. At the former stage of charging,the charging current was very large, so it must be limited in order to dispel the polarization phenomenon and lower temperature. And at the latter stage, the constant-voltage charging method was adopted until the batteries were full. The temperature's effect on progress of charging was large, so temperature compensation system was adopted. PI regulator controlling of current closed-loop and voltage closed-loop was designed to realize the constant-voltage limitary-current charging method, and only one of the two closed-loops worked anytime. PI Regulator was adopted to improve Static and Dynamic Properties.Chapter 4 and 5 introduced the realization of the system design in hardware and software. Chapter 4 designed the hardware circuits including the driving circuit of IGBTs, the reset circuit, the interface circuit of sampling, the hardware lock and the code circuit. Chapter 5 gave software design flow diagram and design of assembly language program.A charging device prototype was constructed. Experimental results demonstrated that the system realized the constant-voltage limitary-current charge of batteries properly.