## 1 Introduction
Finally, the widespread use of EVs and their grid-connected charging may cause a significant increase in energy demand and, accordingly, may cause power quality problems [24; 25]. Power quality refers to the convenience of the electrical energy generated, transmitted, and used by an electrical system to the desired standards. Power quality problems typically denote abnormal conditions in electrical systems resulting from unexpected and undesired situations. These problems can manifest in various forms, hindering the proper operation of electronic equipment, causing productivity losses, leading to equipment failures, and even resulting in significant financial losses. Power quality issues can have widespread effects across a range of applications, from industrial facilities to residential use. Therefore, the proper monitoring, protection, and correction of energy systems are of paramount importance [26; 27; 28]. There are a number of factors that cause power quality problems. These factors are caused by various situations that often occur in energy transmission and distribution systems. Lightning strikes can damage power transmission lines or nearby facilities. In this case, instantaneous voltage increases (transient voltages) occur. When large motors, industrial machines, or large energy loads are put into operation, momentary voltage drops and fluctuations may occur. Faults on the network may cause power transmission lines to be interrupted or voltage fluctuations. Non-linear loads, especially loads with non-linear characteristics such as computers, power electronics, and other electronic devices, can cause harmonic distortions. Capacitive reactors are used to correct the power factor on the grid, but their uncontrolled or incorrect use can lead to harmonic distortions. Transformerfailures, breaker failures, or other electrical equipment failures can cause power quality problems. Lack of voltage regulation or improper functioning of regulation devices can lead to voltage fluctuations. Unbalanced distribution of loads on the network can cause voltage drops and fluctuations. Abnormal changes in grid frequency can have adverse effects on equipment in industrial facilities. Planned maintenance work by power companies or unexpected power outages can cause power quality problems [29; 30; 31]. In addition to other factors, the proliferation of EVs also leads to various power quality issues. In particular, the high electrical demand from charging stations can cause voltage drops and frequency fluctuations in the local grid. Furthermore, harmonic distortions generated during the charging process of EVs can disrupt the sinusoidal waveforms of power systems, potentially causing damage to other electronic devices. Managing these issues is possible through strategies such as implementing power quality improvement solutions and strengthening grid infrastructure. This approach allows for the environmental and operational benefits of EVs to be kept, while enabling more sustainable energy consumption [32; 33]. Many people are using \"clean\" personal means of transport like bicycles, scooters, and bikes which contain electrical batteries as an energy source. Other examples of transportation are EVs and buses. The main differences between these groups are the battery capacity and motor power. Most of these vehicles have individual on-board (e.g., cars) or separate chargers (e.g., scooters, bikes, kick scooters) for charging their batteries. Energy which must be stored in batteries is dependent on the charging process [34; 35]. Power quality problems can affect the reliability and performance of electrically powered systems in the transportation industry. Therefore, power quality monitoring and correction measures are crucial to help reduce potential problems. In this context, this article includes a power quality monitoring and correction study regarding harmonics and other power quality problems caused by EV charging.