Periodic Reporting for period 1 - ISDT (Design and implementation of a frequency domain online diagnostic tool for PV modules)
Berichtszeitraum: 2024-02-01 bis 2026-01-31
Photovoltaic (PV) generators have been established as one of the most important renewable energy sources in the last years and they will have a main role in the energy transition that is envisaged for the coming years according to the European Union Recovery Plan and the Green Deal. However, PV panels may suffer early degradation and failures that affect the PV system reliability and considerably reduce the energy production, not only on a specific panel but in the entire string to which the panel is connected. Therefore, it is important to develop diagnostic tools to improve energy yield, extend the lifetime of the panels, and improve the effectiveness of maintenance activities. Hence, this project aims to develop an online monitoring and diagnostic system, for PV panels, that uses the impedance spectrum (IS) to detect failures while they are operating at their maximum power point (MPP). Therefore, there isn’t a reduction in the power produced by the generator and the measurements can be performed within short time frames to detect the failures as soon as possible. The proposed diagnostic tool will be formed by an electronic device and a failure classification algorithm running on an embedded system. Hence, the project begins with the design and implementation of the electronic device to generate the signals and implement the measurements required to obtain the IS. Then, the project continues with the development of a failure classification algorithm from the analysis of the PV generator dynamic model parameters (DMP), which are estimated using the ISs obtained with the proposed electronic device. Finally, the diagnostic tool will be experimentally validated with PV panels of different technologies and with real failures.
The activities performed up to month 12 are related to the design, simulation, implementation, and experimental validation of the proposed diagnostic tool and are briefly described below.
We performed a literature review to determine the feasible options for the hardware stage to be connected between the PV module and the power converter. From such literature review, we designed the power stage and validated it with simulations in software specialized in power electronics. Then, we defined the main elements to acquire for the implementation of the first version of the proposed hardware stage and performed the acquisition process with the university.
In parallel, we worked on an alternative option for the hardware to perform measurements of impedance spectra (IS) by using the power converter that performs the MPPT, i.e. without additional hardware. We advanced on the design and simulation of this alternative, which is now in the construction process of the first proof-of-concept prototype.
Other important activities are related to the experimental measurements of IS by using a laboratory instrument (potentiostat). We have performed some experimental campaigns in outdoor conditions for a PV module operating under uniform and partial shading conditions. We have used those measurements to propose a first partial-shading detection algorithm based on the IS performed close to the maximum power point. Moreover, we have used those experimental data also to understand the validity of the experimental measurements by using the Kramers-Kronig test.
We performed a literature review to determine the feasible options for the hardware stage to be connected between the PV module and the power converter. From such literature review, we designed the power stage and validated it with simulations in software specialized in power electronics. Then, we defined the main elements to acquire for the implementation of the first version of the proposed hardware stage and performed the acquisition process with the university.
In parallel, we worked on an alternative option for the hardware to perform measurements of impedance spectra (IS) by using the power converter that performs the MPPT, i.e. without additional hardware. We advanced on the design and simulation of this alternative, which is now in the construction process of the first proof-of-concept prototype.
Other important activities are related to the experimental measurements of IS by using a laboratory instrument (potentiostat). We have performed some experimental campaigns in outdoor conditions for a PV module operating under uniform and partial shading conditions. We have used those measurements to propose a first partial-shading detection algorithm based on the IS performed close to the maximum power point. Moreover, we have used those experimental data also to understand the validity of the experimental measurements by using the Kramers-Kronig test.
The main results obtained up to month 12 are listed below:
1. The power stage of the diagnostic tool designed and validated in simulations
2. A power converter for performing MPPT and IS measurements designed and validated in simulations
3. Partial shading detection algorithm based on IS measurements close to the MPP point
4. Procedure to determine the validity of the IS measurements based on the Kramers-Kronig test
5. Experimental campaign in outdoor conditions and different partial shading profiles performed with laboratory equipment (potentiostat)
Expected scientific impacts: These results will contribute to the development of diagnostic tools based on frequency response for PV panels, strings, and arrays. Although this research is focused on PV panels and IS analysis, it is expected that the obtained results can be extended for PV strings and arrays to be applied in residential, commercial, and industrial PV systems. Moreover, the hardware designed and implemented in this project could also be used to develop other diagnostic tools based on frequency response analysis not only for PV generators but also for other renewable energy sources. Furthermore, experimental data obtained in the project will help other researchers to continue the advance of diagnostic tools based on frequency analysis since the results will be accessible to the scientific community.
Expected economic/technological impacts: The ISDT will allow increasing the energy production of PV systems by avoiding the PV panel disconnection to identify if there is a failure or not. Additionally, the energy production is also increased because the ISDT operates along with the MPPT system and doesn’t require performing a voltage sweep to obtain the I-V curve. Moreover, the proof-of-concept prototype developed in this project could be further improved to produce, hopefully, a new device that can be connected to existing PV systems based on inverters and power optimizers. Such a device would also generate new services that can be offered to PV systems’ owners to generate alarms about the probability of a specific failure and to provide information for maintenance planning. Additionally, early failure detection helps to orient maintenance activities and extend the lifetime of the PV generator, bringing an increment in the return on the investment for the PV systems users.
1. The power stage of the diagnostic tool designed and validated in simulations
2. A power converter for performing MPPT and IS measurements designed and validated in simulations
3. Partial shading detection algorithm based on IS measurements close to the MPP point
4. Procedure to determine the validity of the IS measurements based on the Kramers-Kronig test
5. Experimental campaign in outdoor conditions and different partial shading profiles performed with laboratory equipment (potentiostat)
Expected scientific impacts: These results will contribute to the development of diagnostic tools based on frequency response for PV panels, strings, and arrays. Although this research is focused on PV panels and IS analysis, it is expected that the obtained results can be extended for PV strings and arrays to be applied in residential, commercial, and industrial PV systems. Moreover, the hardware designed and implemented in this project could also be used to develop other diagnostic tools based on frequency response analysis not only for PV generators but also for other renewable energy sources. Furthermore, experimental data obtained in the project will help other researchers to continue the advance of diagnostic tools based on frequency analysis since the results will be accessible to the scientific community.
Expected economic/technological impacts: The ISDT will allow increasing the energy production of PV systems by avoiding the PV panel disconnection to identify if there is a failure or not. Additionally, the energy production is also increased because the ISDT operates along with the MPPT system and doesn’t require performing a voltage sweep to obtain the I-V curve. Moreover, the proof-of-concept prototype developed in this project could be further improved to produce, hopefully, a new device that can be connected to existing PV systems based on inverters and power optimizers. Such a device would also generate new services that can be offered to PV systems’ owners to generate alarms about the probability of a specific failure and to provide information for maintenance planning. Additionally, early failure detection helps to orient maintenance activities and extend the lifetime of the PV generator, bringing an increment in the return on the investment for the PV systems users.