Design Of Isolated CLLLC Resonant Dual Active Converter Based On SiC

The offline CLLLC resonant dual active converter is a DC/DC converter that can realize the bidirectional flow of energy.The converter not only retains the resonant circuit’s easy realization of soft switching characteristics,but also can realize bidirectional flow of energy.With the increasing demand for rated power and power density,the third generation wide band gap semiconductor silicon carbide devices have a wide range of applications in power electronics.The third generation wide band gap semiconductor dual active converter has high application prospect and academic research value.This paper will study the dual active converter from the circuit characteristics and control algorithm.Firstly,from the perspective of the frequency domain,the resonant converter circuit is simplified by First Harmonic Approximation,and the simplified circuit is analyzed to obtain its resonant frequency point.Divide the frequency near the resonance frequency point,analyze the state of the circuit in different modes,use the resonance parameters to describe the gain,and explain the three values of n,Q,and k to the circuit DC gain at different frequencies impact.Secondly,in order to control the resonant circuit more accurately,time domain analysis is carried out on the primary side of the controlled object,and the state of resonance current and excitation current is analyzed on the time domain model under different conditions.A charge control algorithm based on frequency modulation control is used to control the CLLLC circuit.On this basis,the method of feedforward compensation and dead time control is used to improve the charge control,and the improved charge control is verified by simulation software.Finally,the design steps of the converter are explained,the resonance parameters of the converter are calculated according to the design requirements,and the design circuit is simulated.The improved charge control algorithm is used to control the designed circuit,and a1 k W CLLLC circuit prototype is produced.Test and verify the waveform of the circuit at different frequencies.The resonant circuit waveforms at different frequencies are analyzed.The highest efficiency can reach 95% in forward operation and 92.5% in reverse operation.