Topology And Control Of Interleaved High-gain DC-DC Converter

The DC-DC converter represented by the traditional Boost converter theoretically has infinite step-up capacity.However,in practical applications,due to the parasitic parameters of the converter,it is difficult to achieve a voltage gain of more than five times.This limits the application of traditional Boost converters in many situations where high voltage gain is required.In order to improve the voltage gain of DC-DC converters,various high-gain DCDC converters have been proposed,and four mainstream voltage gain enhancement techniques have been formed based on the principles of topology cascade technique,inductive coupling step-up technique,inductive energy storage step-up technique,and capacitive energy storage step-up technique.However,as the topology of high-gain DC-DC converters continues to evolve,its development characteristics show a tendency to overly pursue improving the voltage gain of the converter while neglecting other performance of the converter.Most of the proposed highgain DC-DC converters are formed using the technology fusion of the four mainstream voltage gain enhancement methods described above,resulting in higher gain DC-DC converters.Most of the proposed novel high-gain DC-DC converters are based on the combination of the four mainstream voltage gain enhancement techniques mentioned above,resulting in higher gain DC-DC converters.Although the combination of techniques can further improve the step-up capability of the converters,it also introduces the shortcomings of the techniques used into the proposed converter.At present,the DC-DC converter still has the following issues to be optimized.First,The issue of limited voltage gain.Second,The duty cycle range optimization issue for the optimal operating state of the converter.Third,The control optimization issue for non-optimal operating states of converters.Fourth,Modeling of high order converters.Fifth,The development of converter applications towards high voltage levels.Sixth,The development of converter applications towards high power levels.Seventh,The development of converters towards integration.The main works of this thesis are as follows.(1)A summary of the existing high-gain DC-DC converter step-up techniques are sorted out,and the advantages and disadvantages of four mainstream step-up techniques are compared.The capacitor energy storage step-up technique is selected as the entry point for topology design and control optimization of interleaved high-gain DC-DC converters.(2)A low switching stress 2LP-1C(Two inductors in parallel and one capacitor in output)high-gain DC-DC converter is proposed.The proposed converter has a voltage gain twice that of the traditional Boost converter,and the voltage stresses of all switches does not exceed half of the output voltage of the converter,which improves the first and fifth converter optimization issues.In addition,an automatic voltage-balancing control method is proposed,which enables the proposed converter to achieve automatic averaging of the inductor currents and automatic balancing of the capacitor voltages without the need for additional current-averaging and voltage-balancing control.This improves the fifth and sixth converter optimization issues.(3)A 3LP-2CS(Three inductors in parallel and two capacitors in series)high-gain DCDC converter is proposed,which has a voltage gain of three times that of the traditional Boost converter and lower switching voltage and current stresses.In the optimal operating state of the converter,it has automatic averaging feature of the inductor currents and automatic balancing feature of the capacitor voltages.This improves the first,fifth and sixth converter optimization issues.In addition,a 180° phase-shift control method is proposed.Compared with the traditional interleaved parallel control method,the proposed method can expand the duty cycle range of the main switch in the optimal operation state of the proposed converter from 2/3<D<1 to 1/2<D<1.This improves the second converter optimization issue.Moreover,a modeling method for multiphase high-order high-gain DC-DC converters considering parasitic parameters and a closed-loop design method based on numerical calculation are proposed,which provides a mathematical tool for voltage gain analysis and closed-loop design of highorder converters with parasitic parameters.This improves the fourth converter optimization issue.(4)A current-averaging optimization control method for 3LP-2CS high-gain DC-DC converter in non-optimal operation state is proposed.Compared to the traditional 180° phaseshift control method,the proposed control method achieves the inductor current-averaging feature in non-optimal operation state of the converter,and avoids the uneven current distribution problem that occurs in non-optimal operation state.Further,the problem of intermittent or reverse charging of the inductor current caused by the extremely low inductor current in a certain phase in the converter is avoided,and the lower limits of the range of minimum power and minimum current in the non-optimal operation state of the.converter are extended.This improves the third converter optimization issue.(5)A symmetrical topology of 4LP-2CS(Four inductors in parallel and two capacitors in series)high-gain DC-DC converter is proposed.Compared to the 3LP-2CS high-gain DC-DC converter,the proposed converter has higher voltage gain and lower switching voltage and current stresses,and its symmetrical structure allows the two output capacitors to have the same voltage stress.This improves the first,fifth and sixth converter optimization issues.On this basis,a unified topology structure for 2nLP-2CS(2n inductors in parallel and two capacitors in series)high-gain DC-DC converters is proposed,which realizes the phase expansion of the topology family described in this thesis,and provides a modular design scheme for this converter family.The unified converter topology structure has the features of automatic current averaging for inductor currents and automatic voltage balancing for capacitor voltages.The switching voltage and current stresses decrease with the increase of the converter inductor phases,and all capacitor stresses do not exceed half of the converter output voltage.Due to the interleaving feature of the output capacitor ripples of the unified converter topology structure,the output voltage ripple of the converter is greatly reduced,which reduces the withstand voltage and capacity of the capacitors,making the use of ceramic capacitors possible,thus greatly reducing the capacitance volume of the converters.This improves the first,fifth,sixth and seventh converter optimization issues.Moreover,the full dimensional mathematical unified model and simplified mathematical model of the proposed converter unified topology structure are stablished,which provide model reference for advanced control methods and mature design methods of optimal closed-loop controllers for second-order systems.This improves the fourth converter optimization issue.