Investigation of ZVS criteria and Optimization of Switching Loss in a Triple Active Bridge Converter using Penta-Phase-Shift Modulation

Triple active bridge (TAB) as an isolated multiport dc-dc converter is a promising solution for integrated energy management systems to maintain an efficient power flow between the ports. This paper presents the design, modeling, and switching loss optimized phase-duty controlled PWM modulation scheme of a TAB converter composed of three full-bridge modules and a high-frequency planar transformer. The work aims at the derivation and analysis of the zero-voltage switching (ZVS) conditions for a TAB, where the turn-on switching loss is mitigated along with attaining an improved EMI performance, comprising of reduced noise peaks. Moreover, an optimized five-variable control-based TAB PWM modulation technique is proposed in the paper in order to achieve the minimized switching loss as well as overall system loss for a wide voltage gain and load range. The instantaneous switching currents, responsible for the switching losses at the devices, are derived from the transformer winding current expressions, formulated employing the generalized harmonic approximation (GHA) technique. The various loss minimization techniques and the theoretically obtained criteria for ZVS are experimentally verified using a laboratory-developed prototype of a 800W TAB converter. With the implementation of the proposed optimal phase-duty control, the experimental results show a non-unity gain light load efficiency increment up to 10% compared to the conventional phase shift modulation alone.