Power-electronics based converters are essential circuits in renewable energy applications such as electricity generated with photovoltaic panels. The research on the field is getting increasing attention due to climate change problems and their possible attenuation with the use of renewable energy. Mathematical models of the converters are being used to optimize several aspects of their operation. This article is dedicated to optimizing (through the mathematical model and an evolutionary algorithm) the operation of a state-of-the-art converter. The converter, which is composed of two parts or phases, is controlled by pulse width modulation with two switching signals (one for each phase). The converter provides by itself low switching ripple in both the output voltage and the input current, which is beneficial for renewable energy applications. In the traditional operation, one of the switching signals has an algebraic dependence on the other one. This article proposes a new way to select the duty cycle for both signals. In the proposed method, duty cycles of both phases are considered independent of each other; this provides an extra degree of freedom; on the other hand, this produce that the possible combinations of duty cycles which produce a certain voltage gain is infinite, it becomes a problem with infinite possible solutions. The proposed method utilizes the a linear success-history based adaptive differential evolution with linear population reduction, also called L-SHADE algorithm for simplicity, to find the two duty cycles that achieve the desired voltage gain and to minimize the converters switching ripple. The obtained results are compared with the former operation of the converter; the proposed operation achieves a lower output voltage ripple while achieving the desired operation (voltage gain).

This paper introduces a dual-switchhigh step-up DC-DC power converter. The proposed converter features a high step-up voltage gain, relatively low cumulative stored energy over its inductors, low voltage stress on the active switches, and high efficiency, even at a relatively high duty ratio. An assessment of the proposed converter against conventional boost and a high step-up power converter is presented in terms of steady-state time, voltage gain, stored energy over its inductors, and efficiency. The assessment shows a reduction of 81.25% and 62.5% of stored energy in inductors to comply with the same operational conditions. Simulation and experimental results are provided to validate the benefits of the proposed dual-switch high step-up power converter.

Modular multilevel converters are playing a key role in the present and future development of topologies for medium–to–high–power applications. Among this category of power converters, there is a direct AC–AC modular multilevel converter called “Hexverter”, which is well suited to connect three–phase AC systems operating at different frequencies. This topology is the subject of study in this manuscript. The complete Hexverter system is composed of an Hexverter power converter and several control layers, namely, a “virtual $V_{\mathrm{C}}^2$ controller”, a branch current controller in a two–frequency $dq$ reference frame, a modulator, and a voltage balancing algorithm. The paper presents a thorough description and analysis of the entire Hexverter system, providing research contributions in three key aspects: (i) modeling and control in a unified two–frequency $dq$ framework; (ii) developing a “virtual $V_{\mathrm{C}}^2$ controller” to dynamically account for Hexverter’s active power losses allowing to achieve active power balance on the fly; and (iii) a comparative evaluation of modulation strategies (nearest level control and phase disposition–sinusoidal pulse width modulation). To this end, a detailed switched simulation was implemented in the PSCAD/EMTDC software platform. The proposed “virtual $V_{\mathrm{C}}^2$ controller” is evaluated through the measurement of its settling time and calculation of active power losses. Each modulation technique is assessed through total harmonic distortion and frequency spectrum of the synthesized three–phase voltages and currents. The results obtained suggest that the control scheme is able to properly regulate the Hexverter system under both modulation strategies. Furthermore, the “virtual $V_{\mathrm{C}}^2$ controller” is able to accurately determine the active power loss, which allows the assessment of the efficiency of the modulation strategies. The nearest level control technique yielded superior efficiency.

In this work two different modulation strategies termed: i) nearest level control, and ii) phase disposition-sinusoidal pulse width modulation, are described, simulated and compared when applied to a Hexverter-based modular multilevel converter. In addition, two different voltage balancing algorithms are implemented and evaluated. Furthermore, total harmonic distortion regarding three-phase system voltages are assessed. In the end, synthesized branch voltage spectrum for each modulation strategy is analyzed.

This paper exhibits the performance of a high step-up converter employed for maximum power extraction in a photovoltaic system. The proposed converter is conformed by a conventional boost followed by a diode-capacitor-based multiplier for increasing the nominal voltage gain of the boost converter, resulting in a lower duty cycle at the maximum power point. The main characteristics of the converters are analyzed in order to determine an optimal equivalent input impedance. Evaluation of the proposed converter using standard Perturb and Observe algorithm is carried out. Switching simulations evidence the good performance of the whole system under irradiance disturbances.