Research On The Buck-Boost DC/DC Converter Based On Interleaved Technology

With the development of power electronic technology, power electronic converters have been applied in more and more areas. Because the two-stage Buck-Boost DC/ DC converter has two switches and has the advantages of small switch stress, high efficiency, Buck-Boost function, same polarity of input and output,storage elements less requirement, etc.It has been widely used in new energy generation, distributed power, PFC and any other areas where require the converters have a wide input voltage range and high power conversion capability.In this paper, the two-stage Buck-Boost DC / DC converter is the core. A detailed comparative analysis of its operation and the various operating modes is made. The converter's four switching states are summed up and the essence of combined mode is constructed by buck mode and boost mode is revealed. State-space averaging method is used to establish the small-signal model of the converter under buck and boost mode. Interleaved technology is introduced to ehance the capacity of the converter and at the same time to reduce the demand for energy storage components,and then a DC/DC converter with the character of high-capacity and wide input voltage is received. By summarizing and contrasting the traditional DC/DC control strategies, a two mode average current control strategy, a combination of average current control and dual modulation-single carrier control, is proposed to increase the loop gain and achieve the automatic mode switching.At the same time, a new input voltage feedforward method which introduces the state of input voltage to the inner current loop is proposed to suppress the impact caused by input voltage rapid change and mode switch. The simulation model of the interleaved two-stage Buck-Boost DC/DC converter's main circuit and control system is built by using Matlab/Simulink software. Through simulation, it is verified that average current control strategy with input voltage feedforward can greatly enhance the converter's dynamic response speed and achieve automatic mode smooth switching. On the basis of simulation, a prototype is built. The test about the impact of input voltage distutbances on the output voltage is made under buck mode, boost mode and mode switching.The test results validate the wide input range character of the converter and the feasibility of the proposed control method.