Research On Dual Input High Gain DC-DC Converter With Variable Structure

With the aggravation of environmental pollution and fossil energy gradually decreased in recent years, new energy has been paid more attention. In this paper, to solve the problem of multiple inputs, low input voltage and the source instability appeared in the new energy, a dual input high step-up DC-DC converter based on capacitor-diode multiplier cell with a variable structure unit is proposed. The converter has a high voltage gain, low voltage stress of device, multi-degree of freedom control and the flexibility for each input source power distribution. The design of variable structure switch group, making the converter able to work in both single and dual input state, provides a stable output voltage and power and makes the most use of the clean energy.At first, a new boost unit is designed on the basis of the common dual input voltage converter, which doubled the gain of the original converter. And then it points out that there are some defects in the single input state of the converter.Therefore,the concept of variable structure topplogy and the topology of dual input variable structure high gain converter are proposed to solve this problem. The topology not only has a high gain,but also can satisfy the need of dual input and single input power supply. Then the operation principle and performance of the converter are analyzed in detail. The condition of the different switching states is introduced. The advantages and limitations of the converter are also summarized.Secondly, in the face of the control problem of dual input energy and switch group, this paper provides a detailed control strategy, which makes the converter can independently adjust the switch group and the control method according to the load size, in order to ensure the output voltage stable and the maximum use of the clean energy. Futhermore, considering the six order model of the converter is more difficult to design the compensation. In this paper, the method of equivalent replacement is used to reduce the order of the model, and the four order model is obtained in the different state of the switch group, and the corresponding compensator is designed.Finally, in order to verify the feasibility of the proposed topology and the accuracy of the analysis, the experimental prototype is made. The two closed loop experiments are carried out under the condition of double input steady state and the switching condition. The results of the two experiments are given, and the meaning of the waveform is analyzed in detail.The experimental results and theoretical analysis show that the proposed dual input variable structure high gain converter topology realized high gain, energy management and reduce the voltage stress of the switches, but also to make it possible for dual inputs work simultaneously or alone.It provides a new solution for converter applied in the mixing energy which there is a big voltage gap between input and output.