Research On Interleaved Parallel Bidirectional DC-DC Based On Current Sharing Technology

To cope with the energy crisis and environmental pollution,environmental protection and energy-saving industries such as electric vehicles and photovoltaic power generation are gradually entering people's lives.Multiphase interleaved parallel bidirectional DC-DC converters with the advantages of small size,high efficiency,high power density,and small output current ripple have become an important medium for the energy regulation center of electric vehicles and photovoltaic power generation systems.Due to the difference in the parasitic parameters between the phases,the currents in each phase are unbalanced.Based on the actual needs,this paper designs a three-phase staggered parallel bidirectional DC-DC converter,and conducts an in-depth study on t he causes of current sharing and suppression methods.First of all,considering the actual application working conditions,this article takes the duty cycle D?(1/3,2/3)as an example to analyze the working modes of the converter in boost and buck mode.From a mathematical point of view,the output current ripple characteristics are analyzed,and the expressions of the converter output current ripple and single-phase inductor current ripple are given.The results show that the interleaved parallel technique can reduce the ripple amplitude to a certain extent,In the best case,the ripple amplitude is zero.Secondly,the reason for the current imbalance in each phase of the converter is pointed out because there are differences in the external characteristics of each phase,and the basic current sharing strategy is summarized.Aiming at the shortcomings of the complex design of the traditional current sharing control loop,a kind of current sharing is proposed.Control Strategy.The state space averaging method and the equivalent circuit method were used to analyze the relationship between the phase current and the parasitic parameters of the switch,the parasitic resistance of the inductor,the duty cycle and other factors.The steady-state duty cycle D compensation was proposed to eliminate the current imbalance,and to Take any one phase as a r eference and derive the remaining two correspondingly compensated duty cycle components ?D.At the same time,the perturbation method is used to establish small-signal models under different working modes of the converter,the corresponding control objectives of the system are established,and the compensation network is designed to improve system performance.Finally,a 10 kW three-phase test prototype was built,which introduced the design and device selection of related hardware circuits in detail.The software part is based on Matlab /Simulink real-time code generation tool RTW,builds the designed controller model,and generates DSP control code.At the same time,according to the different working modes and load conditions of the converter,experiments are carried out.The experimental results show that the converter has good steady-state and dynamic current sharing performance and meets the specified standards.