# Grid-Connected PV Systems Controlled by Sliding via Wireless Communication
## 1 Introduction  
In recent years, consumption has exhibited a trend towards growth. The ideal would be to provide the energy through renewable energies instead of conventional energies, reducing CO\({}_{2}\) emissions and using unlimited resources with zero fuel costs. Photovoltaic technology, after hydro and wind, has been consolidated as the third most widespread renewable energy. The PV systems can be classified as stand-alone PV energy systems and grid-connected PV systems. The stand-alone PV systems are usually used when there is no access to the grid and the energy produced is stored in batteries to guarantee the supply. Initially, the grid-connected PV systems were used in big areas to produce a large amount of energy although nowadays these systems are gradually growing as self-consumption systems too, within the distribution generation framework. Thus, they can be installed as generation systems in conventional housing, neighborhood associations, shopping centers, or industrial environments. This work is focused on the grid-connected PV systems to provide energy to the grid. However, the integration of the PV technologies into power systems involves some drawbacks due to the fluctuation of the solar generation and the electronic equipment required to convert and transfer the energy to the grid. Thus, the operation of these kind of systems should guarantee the stability, power quality, and reliability of the grid. To do that, it is necessary to implement appropriate methods to diagnose and detect faults, supervise, monitor, and control the operation of the grid. In addition, it is crucial to develop techniques to manage the grid operation in real time. Techniques of faults diagnosis and detectionhave been developed by different authors through learning machines [1; 2], using current-voltage curves and environmental conditions [3], or fuzzy logic [4], amongst others [5; 6]. The monitoring and supervision are also very important within the system operation. The different works focused on different technologies, although the vast majority of them uses wireless sensor networks [7], by means of the standard Open Platform Communications (OPC) [8] or ZigBee [9]. Regarding the communication system, there is a variety of wireless data transmission technologies. The most used so far is the wired communication. Nevertheless, one of the objectives of this work is to replace the conventional wired controlled system by wireless communication. One of the most used communication systems in the world is the satellite communication [10], 2G [11], or 3G [12]. Other technologies as radio-frequency communication can also be used [13]. There are other technologies that use short range communication, such as ZigBee [14; 15], Bluetooth [12], or Wi-Fi [12]. Wi-Fi communication is the selected one for this work because it is crucial to achieve precise measurements of the sensors in real-time to reach the maximum power point (MPP) ensuring the reliable operation of the grid-connected PV system and this type of communication can guarantee it. In addition, this technology ensures robustness even with the interferences that the wireless communication can cause and it also guarantees low latency, precise data acquisition and low power consumption. ZigBee is similar to Wi-Fi communication but when a tight latency and reliability is required, Wi-Fi communication is preferred. Another advantage of the Wi-Fi communication is that it is able to reach 300 m whereas ZigBee has a maximum range of 100 m. Thus, a control by means of Wi-Fi is possible facilitating a real-time and remote operation. In addition, there is a cost reduction since the vast majority of the cabling is not required in Wi-Fi communication. Another crucial aspect for the correct operation of the system is the control. The control is required to transfer the energy from the PV modules to the grid in appropriate conditions. Different works develop a wide range of control methods [16], but they are not focused on the implementation through wireless communication.