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Application of GaN HEMT as a bidirectional switch in matrix converter DOI:10.15199/48.2019.08.34

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In power electronics, bidirectional (four-quadrant) switches (BDS) are a necessary part of all matrix converters which allow to convert AC voltage directly (without a DC link) to AC voltage with controllable amplitude and frequency. BDS are capable to conduct current in both directions and block voltage of both polarities. There are several configurations of BDS but the most commonly used is antiparallel connection of two RB-IGBT and its main advantage is that the current is passing only through one semiconductor [1]. Nowadays, GaN BDS begin to appear as a single package device with dual gate and are used in matrix converters (MC), e.g. [2, 3], but they are still not available on the market. GaN HEMT could be a competition for RB-IGBT due their lower switching and conduction losses, their high frequency operation which could increase the power density of MCs [3]. GaN HEMT connected in series has not yet been tested as a BDS which was the main reason to conduct the research. I. Four-step semisoft current commutation method A. Analysis The 4-step semisoft current commutation method for BDS was firstly proposed in [4]. It is called semisoft, because half of the commutation process is soft switching and half is hard switching [1]. There are many other modifications of that method, e.g. 3-step, 2-step. [5] which are the modification of the 4-step method. To analyse all the commutation processes in a 3-phase MC it is enough to consider only a 2-phase to 1-phase (2f/1f) converter with a DC voltage source and RL load (Fig.1). RC snubbers added to each GaN HEMT significantly reduce the voltage ripple [6], (it is worth mentioning that in [2] for GaN BDS an RCD snubber with 4 diodes, resistor and capacitor is proposed, which could be compared in future work). Control strategy of the 4-step current commutation method is shown in Table 1. For example, if we want to switch from conducting TAa to open TBa BDS and the current of the RL [...]

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