Wide bandgap semiconductor based high performance bidirectional CLLL converter for electric vehicle application

Abstract

Thisthesisproposesanimprovedtopologyforanisolatedbidirectionalresonant dc-dcconverterforelectricvehicle(EV)onboardchargers.Asopposedtothecon- ventional capacitor-inductor-inductor-inductor-capacitor (CLLLC) resonant con- verter,theproposedconverter’sresonantcircuitiscomposedofacapacitor-inductor- inductor-inductor(CLLL)structure,whoseinductances,exceptthecapacitor,can befullyintegratedwiththeleakageandmutualinductancesofthehigh-frequency (HF)transformer.Therefore,thisoffersasmallersize,lowercosts,minimalpower loss, and eventually higher efficiency. Again, the proposed converter design is based on wide bandgap (WBG) transistor switches that operate at MHz-level switchingfrequencytoachievehighpowerdensity,highefficiency,andhighcom- pactness.Toassureclosed-loopcontroloftheproposedCLLLconverter,adiscrete- timeproportionalintegralderivative(PID)controllerhasfirstbeendesignedusing the phase-shifted pulse width modulation (PSPWM) method. The genetic algo- rithm (GA) and particle swarm optimization (PSO) algorithms have both been used to optimize the PID controller parameters and a comparison between the two algorithms have been provided. Second, an intelligent controller based on deepreinforcementlearning(DRL)hasbeenproposedtoautomatethecontroller process. A comparison of the DRL and PID controllers has also been provided, and the DRL controller performed better than the conventional PID controller. Toachievefastswitchingwithverylittleswitchingloss,theconverterissimulated with several Wide Bandgap (WBG) switching devices. A performance compar- ison with conventional Si-based switching devices is also provided. An accurate powerlossmodeloftheswitchingdeviceshasbeendevelopedfromthemanufac- turer’s datasheet to achieve the perfect thermal design of the converter. A 5 kW CLLL converter with an input range of 400 − 460 V direct current (DC) andanoutput range of 530 − 610 V DC and a switching frequency of 1 MHz has beendesignedandinvestigatedundervariousloadingscenarios.GalliumNitride(GaN) switchingdevice-baseddesignsachievedthehighestlevelsofefficiencyamongthe switchingdevices. Theefficiencyofthisdeviceis97.40percentinforwardmode and 96.67 percent in reversemode.