Isolated multiport converters can host loads and sources at different power and voltage levels to their ports by a single topology, giving potential merits in terms of power density and efficiency. However, the higher the number of ports, the higher the number of degrees of freedom in the modulation patterns. This high number of modulation variables complicates the optimization problem, making closed-form solutions impractical. This article avoids the analytic solution to the optimization problem by proposing a data-driven solution. The presented approach is based on an artificial neural network (ANN) trained to minimize the rms value of the currents flowing through the switches and the transformer windings of a triple active bridge (TAB) converter. This minimization is achieved by determining suitable values of the duty-cycles for modulating the converter switches. The proposed ANN-based modulation is validated considering an experimental TAB prototype rated $5 \,\mathrm{k}\mathrm{W}$ .

The paper presents a multidimensional ripple correlation search technique of optimal operating points of triple active bridge (TAB) converters. Such converters present multiple modulation parameters that should be exploited to achieve high operation efficiency. On the other hand, the several degrees of freedom available make the identification of optimal parameters a challenging task, not easily tackled analytically or in closed form. A model-free on-line search method based on the ripple correlation technique is then proposed in this paper. The proposed method finds the optimum modulation parameters of TAB converters utilizing a three-dimensional ripple correlation control. The key property of the proposed solution is the adoption of orthogonal perturbation signals, where the orthogonality is simply obtained using different injection frequencies. The multidimensional correlation technique originally shown herein can be applied to other generic optimization problems. The proposed search is verified through a hardware-in-the-loop validation setup and an experimental prototype rated $5kW$ .

Various industrial applications require a voltage conversion stage from DC to AC. Among them, commercial renewable energy systems (RES) need a voltage buck and/or boost stage for islanded/grid connected operation. Despite the excellent performance offered by conventional twostage converter systems (dc–dc followed by dc–ac stages), the need for a single-stage conversion stage is attracting more interest for cost and size reduction reasons. Although voltage source inverters (VSIs) are voltage buck-only converters, single stage current source inverters (CSIs) can offer voltage boost features, although at the penalty of using a large DC-link inductor. Boost inverters are a good candidate with the demerit of complicated control strategies. The impedance source (Z-source) inverter is a high-performance competitor as it offers voltage buck/boost in addition to a reduced passive component size. Several pulse width modulation (PWM) techniques have been presented in the literature for three-phase Z-source inverters. Various common drawbacks are annotated, especially the non-linear behavior at low modulation indices and the famous trade-off between the operating range and the converter switches’ voltage stress. In this paper, a modified discontinuous PWM technique is proposed for a three-phase z-source inverter offering: (i) smooth voltage gain variation, (ii) a wide operating range, (iii) reduced voltage stress, and (iv) improved total harmonic distortion (THD). Simulation, in addition to experimental results at various operating conditions, validated the proposed PWM technique’s superior performance compared to the conventional PWM techniques.

Isolated multi-port converters offer the ability to connect multiple sources and loads operating at different power and voltage levels at their ports, providing galvanic isolation and shared magnetics as benefits. Nevertheless, challenges are present in these converters, primarily due to ports coupling, a high number of modulation variables, and the overall modeling complexity. This paper explores the operation of the dc-dc quad-active bridge converter (QAB) and introduces an optimization approach using an online model-free four-dimensional ripple correlation control (4D-RCC). A fundamental component analysis (FCA) of the QAB is conducted first, resulting in a decoupling matrix that ensures effective closed-loop control for each port independently. Subsequently, the 4D-RCC method is applied to the QAB, allowing online optimization of the converter’s overall efficiency. The validation of these analytical findings and the optimization strategy is presented through PLECS simulation results and experimental results obtained from a converter prototype rated 5kW.

Triple active bridge (TAB) converter, an isolated multi-port converter (IMPC), connects three dc ports via a three-terminal high-frequency transformer, enabling zero voltage switching (ZVS) without the need for additional snubber circuits. However, under certain loading conditions ZVS is lost and rms currents increase. This paper introduces a model-free, online optimization method using multi-dimensional ripple correlation control (MD-RCC) to ensure ZVS operation while reducing rms currents. The MD-RCC is an online model-free approach, providing robust performance against parameter uncertainties or operational variations. Two distinct methods are utilized to evaluate the cost function online. The first method involves the oversampling of the transformer currents. The second approach relies on the correlation between the EMI noise level and the hard switching of the devices, providing a simpler alternative to oversampling techniques. The proposed MD-RCC technique has been validated through both simulation and experimental testing on a 5 kW prototype, demonstrating its efficacy in optimizing ZVS, reducing EMI noise, and rms currents.