# Centralized MPPT Control Architecture for Photovoltaic Systems Using LoRa Technology
## 7 Conclusions  
This paper proposes a centralized MPPT control architecture for PV subsystems that use LoRa/LoRaWAN communication to exchange the control signals among the sensor and actuator nodes close to the PV subsystems and a centralized computing node, which executes the MPPT algorithms. Different MPPT algorithms may be used in parallel to maximize the power production from the PV subsystems by computing the duty cycle value from the DC-DC converters. This approach adapts to different points of operation due to the ambient conditions or orientation on the PV subsystems. It also adapts to different configurations with several PV subsystems, which may involve either PV modules or strings of PV modules that share one DC-DC power converter. The introduction of LoRa technology presents several advantages when compared to other alternatives. Although LoRa technology provides a low data transfer rate, it is a low-cost/low-consumption technology that is specifically designed for long-distance applications in the range of several kilometers. The use of LoRa's CSS enhances robustness, reducing data loss. Moreover, LoRa also enables connecting to LoRaWAN networks, thereby not only enhancing the potential for decentralized control, but also enabling scalable communication within a broader network infrastructure. All these characteristics make it adequate to be used in a centralized MPPT control architecture. A proof-of-concept prototype involving a rooftop installation in the Faculty of Engineering, Vitoria-Gasteiz (UPV/EHU), was built to validate the presented approach. This prototype involved a PV subsystem and a central computer running MATLAB for the execution of the MPPT control algorithms. These devices were connected by means of a point-to-point LoRa network, which were set up with Arduino MKR WAN 1300 LoRa boards. Although the proposed architecture allows for implementing complex MPPT algorithms, two algorithms were selected for validation purposes: the Perturb and Observe(P&O) and Sliding Mode Control (SMC) techniques. P&O is a simple, widely used MPPT algorithm that requires a low computational cost. Unfortunately, it provides a poor performance under partial shading and abrupt irradiance variations. SMC techniques are robust and provide the capability to overcome possible lost or wrong messages, which is especially relevant when using wireless communications. However, other MPPT techniques could be also used as long as they tolerate low bit rates. The obtained results prove the validity of the presented approach. The response time to abrupt changes in irradiance is acceptable for this kind of application. Future work will implement more advanced control techniques that are suitable for LoRa/LoRaWAN constraints, such as ANN, which calculate the initial duty cycle to reduce the settling time. Another possible future work could be the use of other advanced techniques to improve the estimation of the voltage reference. The presented approach could be complemented with additional mechanisms to ensure the operation of the PV system in the case of communication failures. For example, basic control algorithms could be implemented in edge computers to take over in such cases. The results of these experiments suggest that the proposed low-cost approach can be extrapolated to be used over a LoRaWAN network in which a central computing node executes, in parallel, a number of MPPT algorithms for different PV subsystems. Conceptualization, O.B. and I.C. ; methodology, O.B., I.C., P.F.-B. and E.A. ; investigation, P.F.-B. and E.A. ; writing--original draft preparation, E.A. and P.F.-B; writing--review and editing, O.B., I.C., P.F.-B. and E.A. ; visualization, P.F.-B. and E.A. ; supervision, O.B. and I.C. ; project administration, O.B. and I.C. All authors have read and agreed to the published version of the manuscript. This research was funded by the Basque Government through Project EKOHEGAZ II (ELKARTEK KK-2023/00051), by the UPV/EHU through Project GIU23/002, and by the MobilityLab Foundation (CONV23/14, CONV23/12).