Study Of Work Characteristics For Paralleled Boost Converter

It is necessary to study the techniques of paralleled power modules, because of huge power requirements and wide developments of distributed power system. In practice, there are some differences in power ratings and electrical parameters for paralleled power modules, so, it is possible that one or more modules have excessive current, which could cause more thermal stress, lower stability, what's more, make the modules of heavy load failure. The conventional way of fixing it is to use current share techniques, which would balance current in every module. A lot of researches of current sharing techniques have been done, the main techniques are droop method, master-slave configuration, average current-sharing control, democratic configuration and external current-sharing controller etc. The basic principle of these techniques is uniform that current balance between paralleled modules is ensured according to load, in which the number of paralleled modules is fixed, but efficiency problems are not considered, that is, when load changes, how can we improve the efficiency of paralleled converters by changing the number of paralleled modules and distributing current between modules.In distributed power system, DC/DC converter modules with same or different power levels can be chosen, and modules with different power levels have different operation efficiency. If current sharing technique is used, some modules would work in case of poor efficiency and the performance of converter can not be utilized sufficiently. So, the current sharing technique is only propitious to modules with same or similar efficiency characteristic. For a well-designed power system, the load range must be large enough. It is unfavorable for improving system efficiency that the number of paralleled modules is constant when the load is changing. In this paper, the efficiency problem of paralleled modules with same or different efficiency characteristics is analyzed based on the efficiency characteristics of converters.First, the steady characteristics of Boost converter are analyzed. The state space average method is adopted to analyze the control methods and stability of closed-loop converter. Next, the common current sharing techniques are studied and simulated. Then the efficiency characteristics of Boost converter are studied. Lastly, the correlative efficiency issues are analyzed in paralleling operation and a new way of current distribution is presented, which can improve the efficiency of paralleled DC/DC converters. Simulation results validate theory analysis.