# Efficient Wireless Monitoring and Control of a Grid-Connected Photovoltaic System
## 1 Introduction
To provide the energy from the PV modules to the grid in the correct way, a zero-crossing detector [11] is required to inject the voltage in phase with the grid voltage and guarantee the grid stability [12] and power quality [13]. These problems arise in distributed PV systems when a large number of DC/AC converters are connected. The reason for the instability of these kinds of systems is the intermittent nature of solar energy since it depends on environmental conditions. That may cause fluctuations in the grid and over-voltage, making the voltage regulation difficult. Different control strategies have been proposed to reduce the reactive power [14], stabilize the voltage [15], or achieve maximum energy transfer [16]. In this study, the DC/AC converter uses a proportional integral (PI) control to supply energy to the grid. This method is simple and obtains a proper system operation [17]. The integration of the distributed PV systems in the power grid entails technological improvements in the power systems, such as updated sensors and communication, in order to detect the faults in the solar modules [18], control the DC/DC and DC/AC converter to search for and transfer the maximum power, and guarantee the correct operation of the whole system, ensuring the power quality, the stability of the power grid, and a safe operation and maintenance [19]. Wireless sensor networks (WSN) have become popular in the last decade and represent an opportunity in photovoltaic applications as opposed to wired ones, given their different constraints in terms of design and resources. For WSNs, resource constraints refer to the limited amount of energy, communication range, bandwidth, or limitations in processing power and data storage. The design is constrained by the environment to be monitored and is application-specific. Nevertheless, there are clear advantages that wireless technologies offer. The lack of cabling reduces costs and improves scalability and flexibility. They are easy to deploy, reliable, and require lower maintenance than the wired solutions. The components required for the deployment of WSNs have seen improvements in costs, size, and power constraints, mainly due to recent advances in microelectronics and wireless technologies. However, the widespread deployment of WSNs requires addressing a variety of challenges, which have to be researched. In this study, collecting precise real-time information on photovoltaic system performance is essential to track efficiently the MPP and guarantee the reliability of the power grid. Therefore, several design aspects must be adequately addressed, such as low latency for a suitable performance of the controllers, robustness against interference, reliability in the wireless data transmission, accuracy in data acquisition, and synchronization between sensor nodes and coordinator nodes. Although ZigBee and Bluetooth protocols have been used in PV systems for the monitoring of currents, voltages, temperature, and irradiance, [20; 21; 22; 23; 24; 25], providing energy-efficient designs, they cannot comply with tight latency and reliability requirements. This fact has required the design of a tailored wireless sensor network for the target application based on low latency techniques to achieve real-time monitoring and stable performance of the controllers. The Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard in beacon-enabled mode and with a guaranteed time slot (GTS) mechanism has been used to meet the data monitoring with a predetermined latency. For a better understanding of the readers, a list of symbols along with their descriptions that are used in this article are given in Table 1.