energies Article Feasibility Study GaN Transistors Application in the Novel Split-Coils Inductive Power Transfer System with T-Type Inverter Viktor Shevchenko 1,* , Bohdan Pakhaliuk 1,2, Oleksandr Husev 1,3,*, Oleksandr Veligorskyi 1, Deniss Stepins 4 and Ryszard Strzelecki 2,* 1 Chernihiv Power Electronics Laboratory, BRAS Department, Educational-Scientific Institute of Electronic and Information Technologies, Chernihiv National University of Technology, 14039 Chernihiv, Ukraine; [email protected] (B.P.); [email protected] (O.V.) 2 Faculty of Electrical and Control Engineering, Gdansk University of Technology, 80-233 Gdansk, Poland 3 Power Electronics Research Group, Tallinn University of Technology, 12616 Tallinn, Estonia 4 Institute of Industrial Electronics and Electrical Engineering, Riga Technical University, 12/K1 Azenes Street, LV-1658 Riga, Latvia; [email protected] * Correspondence: [email protected] (V.S.); [email protected] (O.H.); [email protected] (R.S.); Tel.: +380-93-957-4211 (V.S.); +380-96-985-5012 (O.H.) Received: 17 July 2020; Accepted: 28 August 2020; Published: 1 September 2020 Abstract: A promising solution for inductive power transfer and wireless charging is presented on the basis of a single-phase three-level T-type Neutral Point Clamped GaN-based inverter with two coupled transmitting coils. The article focuses on the feasibility study of GaN transistor application in the wireless power transfer system based on the T-type inverter on the primary side. An analysis of power losses in the main components of the system is performed: semiconductors and magnetic elements. System modeling was performed using Power Electronics Simulation Software (PSIM). It is shown that the main losses of the system are static losses in the filter inductor and rectifier diodes on the secondary side, while GaN transistors can be successfully used for the wireless power transfer system. The main features of the Printed Circuit Board (PCB) design of GaN transistors are considered in advance. Keywords: wireless power transfer; inductive power transmission; multilevel converter; AC-DC power converters; T-type inverter; GaN-transistors; electromagnetic coupling 1. Introduction Interest in inductive wireless power transmission is constantly growing due to the increasing interests of both low-power wireless chargers for mobile and wireless charging stations of medium and high power for electric bikes and electric vehicles. Such chargers transfer the electric energy wirelessly from primary to secondary inductor by means of inductive coupling [1]. Inductive wireless power transfer systems consist of a transmitting part (contains an inverter, compensation circuit and primary inductor) and a receiving part (receiving inductor, compensation circuit, rectifier) [1]. The researchers have already analyzed the main possible topologies of compensation schemes, their advantages and disadvantages, and described the general recommendations for their implementation. It is well known that Wireless Power Transfer (WPT) systems have some limitations, such as short transmission distance(centimeters or dozens of centimeters at acceptable levels of transmission efficiency) [2,3], sensitivity to the exact positioning of the receiving coil relative to the transmission coil [2,4], size and cost of the system. Energies 2020, 13, 4535; doi:10.3390/en13174535 www.mdpi.com/journal/energies Energies 2020, 13, x FOR PEER REVIEW 2 of 16 Among existing limitations, the issue of the size and cost of the WPT system is one of the most Energiesimportant.2020, 13Researchers, 4535 are still looking for the optimal system configurations and topologies2 of of 16 power converters that would best meet the above requirements. Different types of switches are utilized in the power electronics converters [5–8]. The conventionalAmong existingInsulated limitations, Gate Bipola ther Transistors issue of the (IGBTs) size and are cost gradually of the WPT going system out of is use one in of industrial the most important.circuits of ResearchersWPT systems are due still to looking their forlow the switching optimal systemcapability configurations [9]. The reverse and topologies blocking of voltage power converterscapability of that the would conventional best meet IGBT the is above very requirements.low; there are relatively large power losses [10]. It is well knownDi ffthaterent the types use of wideband switches are gap utilized semiconductors in the power (such electronics as GaN-transistors) converters [5 –instead8]. The of conventional classical Si Insulatedpower switches Gate Bipolarcan significantly Transistors reduce (IGBTs) the are power gradually losses goingthat lead out to of the use increasing in industrial of the circuits system of WPTefficiency systems or significantly due to their increase low switching switching capability frequency [9]. reducing The reverse size blockingof passive voltage elements capability [11–13]. ofIt theis advisable conventional to use IGBT GaN istransistors very low; for there T-type are topo relativelylogies large[5–8,14]. power The lossesGaN fe [10atures]. It isfast well switching, known thatlow parasitic the use of charges, wideband reverse gap semiconductorsconductivity with (such zero as recovery GaN-transistors) charge and instead low driving of classical power Si powerlosses switchesand dynamic can significantly losses; compared reduce theto Si-IGBTs power losses and that SiC-MOSFETs lead to the increasing [5,6,15–18], of thehigher system efficiency, efficiency low or significantlyparasitic output increase capacitance switching [16–18] frequency can be reducingachieved. sizeThe ofadvantage passiveelements of GaN over [11– Si13 is]. Itmostly is advisable visible toat higher use GaN frequencies transistors in for dynamic T-type losses topologies [15,19]. [5– However,8,14]. The the GaN conduction features fast losses switching, are comparable low parasitic with charges,the SIC semiconductors reverse conductivity [18,19]. with zero recovery charge and low driving power losses and dynamic losses;The compared main goal to Si-IGBTsof the article and SiC-MOSFETsis to study the [5 ,feasibility6,15–18], higherof GaN effi transistorciency, low application parasitic outputin the capacitanceproposed non-traditional [16–18] can be (non-classical) achieved. The WPT advantage system. This of GaN will be over based Si is on mostly the loss visible analysis at higherof the frequenciesmain components in dynamic of the lossescircuit. [15 ,19]. However, the conduction losses are comparable with the SIC semiconductorsThe paper, consisting [18,19]. of seven sections, proposes a new solution of the wireless power transfer systemThe based main on goal two of theparallel article single-phase is to study the T-type feasibility GaN-based of GaN invertors transistor (dual application T-type in inverter) the proposed with non-traditionaltwo transmitting (non-classical) coils on one ferrite WPT core system. (coupled This transmitting will be based inductances). on the loss The analysis case study of the system main componentsdescription and of the advantages circuit. of such solution are represented in Section 2 of the paper. According to previousThe paper,research consisting [20], more of than seven 70% sections, of the losse proposess in WPT a new systems solution for of various the wireless cases of power power, transfer loads systemand working based onfrequencies two parallel depend single-phase on semiconduc T-type GaN-basedtors and invertors inductors (dual [20,21]. T-type Therefore, inverter) withthe twocontribution transmitting of such coils parameters on one ferrite was coretaken (coupled into account transmitting in calculations inductances). in this paper. The case Confirmation study system of descriptionthe advantages and advantagesof the proposed of such solution, solution made are represented mainly by in power Section losses2 of the analysis, paper. Accordingdescribed toin previousSections 3–5. research Section [20 ],3 moreand 4 than proposes 70% of the the losses losses models in WPT of systems the GaN for transistors various cases and ofcoil power, inductors, loads andrespectively. working frequenciesSimulation dependand experimental on semiconductors verifica andtion inductors of the proposed [20,21]. Therefore, solution theis described contribution in ofSection such parameters5, with conclusions was taken and into list account of patents in calculations devoted to in the this proposed paper. Confirmation WPT system ofon the Section advantages 6 and of7, respectively. the proposed solution, made mainly by power losses analysis, described in Sections3–5. Sections3 and4 proposes the losses models of the GaN transistors and coil inductors, respectively. Simulation and2. Case experimental Study System verification Description of the proposed solution is described in Section5, with conclusions and list of patents devoted to the proposed WPT system on Sections6 and7, respectively. Figure 1 depicts the proposed circuit of a multi-level converter for WPT. The primary converter 2.consists Case Studyof a System full-bridge Description three-level T-type inverter connected to bidirectional auxiliary semiconductor switches. The GaN-based T-type inverter is first proposed for use in a WPT system togetherFigure with1 depicts two coupled the proposed inductors. circuit It provides of a multi-level a number converter of advantages for WPT. over The existing primary analogues. converter consistsThe of DC a full-bridgesource is applied three-level