# Charge Management of Electric Vehicles from Undesired Dynamics in Solar Photovoltaic Generation
## 2 Power Photovoltaic Fluctuations  
Photovoltaic (PV) systems use solar power as their primary resource for energy production. Their production capacity depends mainly on the variability of the incident solar radiation on the surface of the PV panels. Therefore, the output energy can reach values above or below the required power demand [12]. The fluctuating behavior of the output power is related to weather conditions, especially to the density of the cloudiness between the panel surface and the sun [13].  
It is necessary to use maximum power point tracking (MPPT) techniques [2] to optimize the energy supplied by the PV solar system. There are several MPPT algorithms, such as perturb and observe (P&O), incremental conductance (IC), fuzzy logic control (FLC), and fractional short circuit current (FSC), among others [14]. Regardless of variations in weather conditions, these methods seek to extract the maximum energy from the PV array (PV module + DC/AC converter) [2], In addition, these algorithms can reduce the variation of output energy, reducing the efficiency of the system, an aspect that compromises the profitability of the solar system.  
The dynamic behavior of solar radiation in the measurement area shows fluctuations with periods in the order of hours, minutes, or even seconds. These variations depend mainly on the cloud density, with an atypical behavior, as shown in Figure 1. The data in the figure come from the meteorological station available at the microgrid laboratory of the University of Cuenca (Campus Balazy) [15], which is located in the city of Cuenca-Ecuador, belonging to the mountainous region of the Andes at the coordinates \(2^{\circ}53^{\prime}31.0^{\prime\prime}\) S \(79^{\circ}02^{\prime}18.7^{\prime\prime}\) W.  
The city of Cuenca presents the typical meteorological behavior of the Andean mountain regions with only two seasons. Between March and April and October and November is the rainy season, and June and July are the dry seasons. These particular conditions influence the behavior of solar irradiation and temperature [2].  
The study developed by [2] presents an analysis of the dynamic behavior of solar radiation for this same Andean city, and the results showed that the PV power ramp-rate can reach between 50% and 70% of the nominal power of the system in intervals close to 15 s. This study evaluates the use of electrical-type storage systems with supercapacitors at the point of common coupling (PCC) to reduce the variations in PV power output. Using this technology, the decrease in the power ramp rate was nearly 6.66 times. Moreover, among other technologies of energy storage that could be used for this purpose include batteries, fuel cells, and recently, electric vehicle (EV) batteries [6; 13; 16].  
The energy storage system (ESS) of EV batteries contributes to the flexibility of the power system. This storage system helps to store excess electricity and provide ancillary services to the grid, such as frequency regulation, peak demand reduction, and improved operation and reserve capacity to secure the grid [17]. From a technical point of view, the massive insertion of EVs plays an important role in the integration of PV solar power generation systems into existing distribution grids. It constitutes a feasible solution for the control and reduction of PV power fluctuations in the PCC. For instance, an evaluation found that the good process matching between EV charging and PV generation makes it possible to manage the surplus energy produced by this source [17].  
Despite the benefits of the high share of EVs in controlling PV power fluctuations, it can affect power quality and grid reliability. The EV charging process causes an increase in the load profile during peak hours, overloading of power system components, voltage deviations, harmonics, and system stability problems [18].  
Figure 1: Typical behavior of solar radiation. September 2020. Campus Balazy, Cuenca-Ecuador.