Photovoltaic (PV) grid-connected system is nowa-days a well established industry. For PV inverters, European (EURO) efficiency and California Energy Commission (CEC) efficiency have been defined, as Figures of Merit (FoM) allowing easy PV inverter efficiency estimation, while including consideration on PV variability. This paper explores the applicability of weighted efficiencies for off-grid H2production system with DC-DC connection of the PV source, for both DC-DC converter, and electrolyzer. The study considers precise modeling of the system, and evaluation of its operation and efficiency over real scenario, with environmental data of three locations considered, with minute-based resolution, allowing precise simulation. Evaluation of EURO and CEC efficiencies for DC-DC converter and electrolyzer demonstrate the accuracy of the FoM with error lower than 1.23% and 3.70% respectively. It is finally recommended the use of weighted efficiencies for the evaluation of off-grid H2production systems, allowing fast and accurate comparison between different electrolyzer and DC-DC converter technologies while designing new plants.

This paper proposes a DC-coupled PEM electrolyzer current control scheme combined with an Input Capacitors Voltage Balancing (ICVB) strategy for a three-channel interleaved dual buck converter topology, aimed at low-carbon hydrogen production. Input capacitors voltage imbalance can lead to improper operation of the interleaved dual buck converter topology, potentially damaging the power components. To address this issue, a control scheme featuring differential operation is proposed to regulate the input voltages, alongside the current control of the electrolyzer, directly influencing the amount of hydrogen produced. By controlling 5 out of 6 inductor currents, it is possible to leave one degree of freedom to control the voltage balance of the input capacitors, indirectly controlling the remaining current due to the operating principle of the topology. Simulation results are presented to validate the proposed control scheme for the proposed system with a nominal power of 1MW.

DC microgrids have been gaining importance in modern power grids. Thanks to its DC nature, photovoltaic (PV) energy generation fits perfectly as a renewable source for DC microgrids. In this context, DC-DC converters are used to interconnect the PV source with the DC bus of the microgrid. This paper proposes a new transformerless partial power AC-link converter which can be used for this purpose. Unlike traditional partial power converters, the proposed solution does not require the use of a transformer. A reduced dynamic average model of the new converter is presented and detailed operation of the proposed converter is given, along with simulation results, to validate the converter’s behavior. Results on a 6.5 kW PV system show a maximum efficiency of 98.7%, confirming the interest of the proposed transformerless partial power AC-link converter in a DC microgrid.

Increasing the amount of energy extracted from a large-scale photovoltaic (PV) plant directly impacts its profitability. Obtaining higher energy yields depends heavily on the efficiency of the power conversion stages, but also on the configuration of the PV plant. More distributed maximum power point tracking (MPPT) among PV modules, allows maximizing the amount of energy extracted, especially under non-uniform conditions. To deal with partial shading conditions at module level, a sub-module power optimizer based on partial power converters is proposed. The configuration employs an isolated partial DC-DC power converters allowing to decouple the shaded parts from the unshaded at PV module level, maximizing the energy extracted. The behavior of the proposed configuration is verified through simulation, which is compared with a classic string configuration through analysis based on performance, improvements, and drawbacks of the proposed structure under mismatching scenarios.

Commercial photovoltaic microinverter topologies are normally composed of two stages: a step-up dc-dc stage and a step-down dc-ac stage. Nevertheless, to achieve high-ratio conversion, a high frequency transformer is used in the dc-dc stage, resulting in a bulky configuration with a high cost of implementation. To minimize these issues, a single stage boost inverter is proposed, composed by two bidirectional boost dc-dc converter. The control of this topology is complex due to its high non-linearity behaviour. Therefore, this paper presents a control methodology based on Finite Control Set Model Predictive Control (FCS-MP) algorithm with predictions of the system variables through the inverter model and an optimization process. Each boost dc-dc converter of the inverter is regulated to achieve an output signal composed of the sinusoidal wave with a dc bias. The main features of the boost inverter and predictive control are analysed. Simulations are shown in order to validate the proposed control and the converter for grid-connected PV applications.

The parallel association of classical commutation cells is a good solution for increasing the output current driven by the converters while the classical semiconductors technology are used. The control strategies used with this type of connection must be able to ensure good distribution of the output current among the different legs. This paper applies two control strategies based on the Model Predictive Control (MPC) in order to handle these type of connections. A comparison between these control strategies is also carried out by experiments.

Current model predictive control for a grid-connected four-leg voltage source converter application is presented in this paper. The solution of the optimum criterion defined by predictive control is considered as the reference current. This current will be applied based on projections of the different current control vectors corresponding to the switches states. Geometrical properties of the predicted current projections are used to achieve a current control strategy operating at fixed switching frequency. A laboratory model of the four-leg converter and its load has been constructed and its performance has been tested through experiments.