# Grid-Connected PV Systems Controlled by Sliding via Wireless Communication
## 1 Introduction
Nowadays, the controllers are implemented in remote control centers, facilitating the monitoring, supervision and detection of faults. Then, the signals are sent to a base station, where the control is implemented, to calculate all the required values for the correct operation and sent them back to the PV plant again. In this work, we propose the control of a grid-connected PV system by means of wi-fi. The wireless communication increases the level of noise. Thus, the communication effect requires to be analysed to guarantee the robustness and stability of the system. The control through Wi-Fi communication has been already studied in a stand-alone PV system [17], analysing the effect of the communication in the DC/DC converter control. This work innovates studying the wi-fi effect in the controller of the DC/DC converter and the DC/AC converter which injects power to the grid accomplishing the power quality requirements amongst others (signals synchronization, maximum energy transfer, control stability, robustness). Regarding the DC/DC converter, there are different topologies. The most usual DC/DC converter used in PV systems is the boost converter [18], since it can rise the output voltage. In this work, a buck-boost converter is used, due to the possibility of increasing or decreasing the voltage at the output. This converter is advantageous when a required range of voltage is needed with telecom loads [19]. Thus, the maximum power point tracking (MPPT) algorithm is implemented in the buck-boost converter. There are many MPPT methods, from the simplest ones as the Perturb and Observe [20], or the Incremental Conductance [20], to the most complex such as fuzzy logic [21], neural network [16], Particle Swarm Optimization [22], or backstepping control [19], amongst others [23]. All the methods differ in the MPPT efficiency, convergence speed, complexity, number of sensors, or the effect of the perturbations [24]. In this work, a sliding mode control (SMC) is proposed and applied to a buck-boost converter [17]. This non-linear controller, which is robust and stable under perturbations, tracks the reference voltage that provides the maximum power point (MPP) [17; 25; 26]. The grid-connected PV system requires the connection of a DC/AC converter to inject energy to the grid. The inverter plays an important role in grid synchronization for the correct operation of the system [27; 28]. The DC/AC converter produces high order harmonic that affect the voltage power quality. Thus, it is required to inject the signals taking into consideration the power quality and the stability of the grid, using harmonic filters [28], to decrease the current harmonics, the voltage distortion or to compensate reactive power. In this work, a passive filter with an inductor connected at the inverter output is used. According to the DC/AC converter controller, there are many methods [29; 30; 31; 32]. In this work, a PI control is used due to its simplicity and effectiveness to transfer energy from the PV modules to the grid. The paper is organized as follows. In Section 2 the PV system is presented, where the different components of the grid-connected PV system are described, Section 3 presents the controllers for the DC/DC converter and the DC/AC converter, whereas Section 4 describes the experimental platform and the experimental results. Then, the discussion is presented in Section 5, and finally, the conclusions are drawn in Section 6.