• Energy Research

In this paper a grid-tied photovoltaic (PV) cascaded H-bridge (CHB) inverter with embedded storage units is proposed. The multi-input single-output inverter architecture allows a distributed maximum power point tracking (DMPPT) approach, thus mitigating the mismatch effects. The energy storage units (ESUs) embedded at each dc-link provides more flexibility to the power circuit compensating for the inherent variability of the PV sources. The proposed power system ensures a continuous power supply to the grid also in case of PV power fluctuations due to irradiance conditions as well as to the MPPT. In particular, the presence of a storage element allows a voltage sweep on the PV source to be implemented, thus guaranteeing the maximization of PV energy harvesting, with no detrimental effect on the power delivery to the utility network. The numerical results, carried out on a single-phase nineteen-level PV CHB inverter, reveal the improved performance of the proposed design and control technique.

In this paper a grid-tied photovoltaic (PV) cascaded H-bridge (CHB) inverter with embedded storage units is proposed. The multi-input single-output inverter architecture allows a distributed maximum power point tracking (DMPPT) approach, thus mitigating the mismatch effects. The energy storage units (ESUs) embedded at each dc-link provides more flexibility to the power circuit compensating for the inherent variability of the PV sources. The proposed power system ensures a continuous power supply to the grid also in case of PV power fluctuations due to irradiance conditions as well as to the MPPT. In particular, the presence of a storage element allows a voltage sweep on the PV source to be implemented, thus guaranteeing the maximization of PV energy harvesting, with no detrimental effect on the power delivery to the utility network. The numerical results, carried out on a single-phase nineteen-level PV CHB inverter, reveal the improved performance of the proposed design and control technique.

Characterizing the electron transport layer (ETL)/perovskite interface in perovskite solar cells (PSCs) is of paramount importance for their overall performance. In this article the effect of different concentrations of graphene nanoplatelets in addition to SnO2 is investigated by considering degradation over time. PSCs behavior is monitored by collecting dark current–voltage curves as fabricated and after two months. A deeper insight is gained through impedance spectroscopy analysis. From Nyquist plots equivalent circuit models and the corresponding time constants are extracted. Moreover, resistive part of the impedance associated with high frequency has been related to static shunt resistance, assessing one of the considered ETL doping concentration as the more suitable choice to reduce degradation.

Characterizing the electron transport layer (ETL)/perovskite interface in perovskite solar cells (PSCs) is of paramount importance for their overall performance. In this article the effect of different concentrations of graphene nanoplatelets in addition to SnO2 is investigated by considering degradation over time. PSCs behavior is monitored by collecting dark current–voltage curves as fabricated and after two months. A deeper insight is gained through impedance spectroscopy analysis. From Nyquist plots equivalent circuit models and the corresponding time constants are extracted. Moreover, resistive part of the impedance associated with high frequency has been related to static shunt resistance, assessing one of the considered ETL doping concentration as the more suitable choice to reduce degradation.

The paper deals with design and control of a fault tolerant and reconfigurable photovoltaic converter integrating a Battery Energy Storage System as a standby backup energy resource. When a failure occurs, an appropriate control method makes the energy conversion system capable of operating in open-delta configuration in parallel with the grid as well as in islanded mode. In case network voltage is lacking due to heavy anomalies or maintenance reasons, the proposed control system is able to quickly disconnect the inverter from the grid while ensuring the energy continuity to the local load and the emergency fixtures by means of the integrated battery packs. In particular, the paper proposes a fast islanding detection method essential for the correct operation of the control system. This specific technique is based on the Hilbert transform of the voltage of the point of common coupling, and it identifies the utility lack in a period of time equal to half a grid cycle in the best case (i.e., 10 ms), thus resulting in good speed performance fully meeting the standard requirements. A thorough numerical investigation is carried out with reference to a representative case study in order to demonstrate the feasibility and the effectiveness of the proposed control strategy.

The paper deals with design and control of a fault tolerant and reconfigurable photovoltaic converter integrating a Battery Energy Storage System as a standby backup energy resource. When a failure occurs, an appropriate control method makes the energy conversion system capable of operating in open-delta configuration in parallel with the grid as well as in islanded mode. In case network voltage is lacking due to heavy anomalies or maintenance reasons, the proposed control system is able to quickly disconnect the inverter from the grid while ensuring the energy continuity to the local load and the emergency fixtures by means of the integrated battery packs. In particular, the paper proposes a fast islanding detection method essential for the correct operation of the control system. This specific technique is based on the Hilbert transform of the voltage of the point of common coupling, and it identifies the utility lack in a period of time equal to half a grid cycle in the best case (i.e., 10 ms), thus resulting in good speed performance fully meeting the standard requirements. A thorough numerical investigation is carried out with reference to a representative case study in order to demonstrate the feasibility and the effectiveness of the proposed control strategy.

A portable circuit for the continuous monitoring of the I-V curves of solar panels is presented. The circuit doesn't require to remove the solar panels from the field, it exploits a remote controlled solid-state switch to temporary isolate the solar panel from the string; meanwhile, a free path for the string current is allowed in order to prevent the interruption of power delivering. The accuracy of the system has been assessed by comparison with high precision lab instrumentation. On field experiments, performed in different situations, evidenced the suitability of the circuit for the diagnostic of outdoor operating solar panels.

A portable circuit for the continuous monitoring of the I-V curves of solar panels is presented. The circuit doesn't require to remove the solar panels from the field, it exploits a remote controlled solid-state switch to temporary isolate the solar panel from the string; meanwhile, a free path for the string current is allowed in order to prevent the interruption of power delivering. The accuracy of the system has been assessed by comparison with high precision lab instrumentation. On field experiments, performed in different situations, evidenced the suitability of the circuit for the diagnostic of outdoor operating solar panels.