A fully normalized algorithm to implement the optimal triple-phase shift (TPS) modulation strategy of the dual active bridge converter is proposed in this paper. The algorithm evaluates three simple expressions that fit the optimal solutions obtained in recent works, which allows the algorithm to be implemented in real-time and valid for the whole operating range. As a result, the converter operates under zero voltage switching conditions and minimizes conduction losses. In addition, the algorithm considers the minimum current required to guarantee zero voltage switching condition that faces undesired dead-band of switching devices effect. The proposal achieves soft transition between any operation region and fast closed-loop response with no stability concern, presenting robustness under leakage inductance deviation. Finally, the algorithm presented in this paper is verified with a 4 kW experimental prototype. Experimental results show that the algorithm proposed can be evaluated with less than 2.8 μs and allows soft transition between any operation region to be achieved. Besides, fast closed-loop changes of 750 μs through all the operating ranges, keeping minimum RMS current under zero voltage switching, are shown.

Modular multilevel converters (MMC) can be used in several applications, especially (but not only) in high-voltage direct current (HVDC) and STATCOM. In order to develop experimental scaled-down test benches for lab validation, several projects have developed MMCs with a limited number of cells, but they need to use pulse width modulation (PWM) techniques to achieve acceptable power quality (because nearest level modulation (NLM), common in HVDC applications with hundreds of levels, cannot achieve sufficient power quality unless the number of cells is high enough). The present paper proposes a new concept which is based on designing arms with a single cell. This allows to have the simplest possible converter that maintains the structure of an MMC. While all the inner controllers of large-scale HVDC MMCs are included, the only remarkable difference is that PWM is used and NLM cannot be implemented. As this is also a limitation for other low voltage MMC, the proposed concept is suggested for scaled-down low voltage applications. The paper includes the design and construction of the converter, the definition and implementation of the converter controllers, and the converter testing, with detailed dynamic simulations and an experimental setup.

This paper presents the design and implementation of a Complex Order Fractional Proportional Resonant (COFPR) controller. The proposed COFPR controller is an evolution of the Fractional Proportional Resonant (FPR) controller suitable for high-frequency tracking. The best performance of the COFPR is obtained by reducing the excitation region promoted by FPR controllers and PR controllers. The COFPR is analysed in the frequency domain. For comparison purposes, Proportional Resonant with Harmonic Compensators (PRHC), FPR and COFPR controllers are designed for the current regulation of a voltage source converter. They are compared considering the same controller gains tuning criteria and also the same phase margin. A set of simulations and experimental results on a 3.6 kVA gallium nitride (GaN) inverter are discussed. The proposed COFPR controller arises superior at high frequencies when the same gains for the controllers are used. The COFPR controller can reduce excitation regions on PR controllers tuned with a similar phase margin without losing a close tracking capability. This advantage promotes COFPR as a proper alternative regarding program memory and execution time required, as it can be properly implemented within a specific frequency range by an approximation of order three or four.

This paper proposes a triangular modulation with zero current switching (ZCS) for a hybrid Si-SiC isolated bidirectional DC-DC converter (IBDC). Three of the four legs in the IBDC operate at ZCS and use Si IGBTs, while the fourth operates at zero voltage switching (ZVS) and uses SiC MOSFET. In that case, the turn-off switching losses are concentrated regardless of the direction of the power. The main contribution of this paper resides in the proposed dead-band compensation mechanism. This dead-band compensation is crucial when addressing ZCS modulation and improves the overall efficiency of the full operating range. As a co-benefit, the proposed mix of semiconductor technologies can result in an effective cost reduction compared with a full SiC IBDC. The paper contains a detailed explanation of the implemented modulation applied to an IBDC. The paper contributes to deploy a theoretical implementation where the effect of parasitic capacitance on semiconductors during the dead-band is analytically considered. The presented method results are validated on a laboratory set-up using a 20 kW - 40 kHz hybrid Si-SiC IBDC.