## 2 Materials and Methods  
Distortions caused by the non-linear load are directly related to the charging process of EVs described above. EV charging stations typically represent highly non-linear loads. This is due to the use of power electronic components (such as power converters) during the charging process. These components alter the waveform of the electric current while converting alternating current (AC) to direct current (DC) or changing the DC to a different DC voltage level. This alteration deviates from the ideal sinusoidal wave and produces disturbances known as harmonic distortion [39; 40]. Harmonics are signals that are exact multiples of the fundamental frequency and act as unwanted additional frequencies in the electrical system. Voltage asymmetry is the imbalance of voltages between phases in a three-phase system. Single-phase loads, particularly large single-phase EV chargers, are potential sources of voltage asymmetry. Other distortions arising from non-linear loads, including non-sinusoidal residual currents, can cause issues in residential or commercial electrical installations during the charging process. These distortions can decrease the efficiency and reliability of the electrical system, pose safety risks, cause overheating in electrical installations, shorten the lifespan of equipment, and lead to many other power quality problems [41]. In this study, total harmonic distortion (THD) and separate harmonic components were examined. Voltage, current THD, and individual harmonics are important power quality parameters and expresses the percentage of the ratio of harmonic components in electrical signals to components at the fundamental frequency. These harmonic components represent distortions that often affect the operation of electronic devices, causing overheating in systems, energy losses, and malfunctions in electrical equipment [42; 43]. Standards have been required to define the limits of and methods for measuring harmonic distortion because of the adverse effects of harmonics and inter-harmonics. When relevant studies were examined, it was seen that various equations were used to calculate and measure THD [44; 45; 46; 47]. _THD_ expression is presented in Equations (1) and (2), which are described by [44]. \[THD=\sqrt{\left(\frac{V_{0}}{V_{1,rms}}\right)^{2}+\sum_{n=2}^{\infty}\left( \frac{V_{n,rms}}{V_{1,rms}}\right)^{2}}, \tag{1}\]  
where \(V_{rms}\) is  
\[V_{rms}=V_{1,rms}\sqrt{1+THD^{2}}. \tag{2}\]  
The generalized _THD_ expression presented in [45] is given in Equation (3) below:  
\[THD=\sqrt{\frac{\left(\frac{N-1}{2}\right)^{2}-\frac{1}{45}\cdot\sum_{k=1}^{ \left[\frac{N-1}{2}\right]}\left(\left(k+\left[\frac{N}{2}\right]-\frac{N}{2} \right)\cdot\alpha_{k}\right)}{\sqrt{\frac{8}{\pi^{2}}\cdot\left(\sum_{k=1}^{ \left[\frac{N-1}{2}\right]}\cos\left(\frac{\pi\cdot\alpha_{k}}{180}\right)\ +\left[\frac{N}{2}\right]-\frac{N-1}{2}\right)^{2}}-1}}, \tag{3}\]  
where \(N\) is a random number of phase voltage levels (odd or even), and \(\alpha_{k}\) is the \(k\)-th switching angle. Moreover, in [46], THD is defined according to Equation (4):  
\[THD=\frac{\sqrt{\sum_{h=2}^{hmax}\left(Y_{H,h}\right)^{2}}}{Y_{H,1}}=\sqrt{ \sum_{h=2}^{hmax}\left(\frac{Y_{H,h}}{Y_{H,1}}\right)^{2}}=\sqrt{\sum_{h=2}^{ hmax}\left(y_{H,h}{}^{2}\right)^{2}}, \tag{4}\]  
where \(Y_{H,h}\) is the rms value of the harmonic component with index \(h\), where \(h\) represents the order of the harmonic and can take values like 2, 3, 4, etc., and \(hmax\) is the maximum harmonic order considered in the measurement or analysis. It specifies the highest order of harmonics that is taken into account. Where \(Y_{H,1}\) is the rms value of the fundamental frequency component, which is the lowest frequency component and generally the main component of the signal. \(THD_{u}\) is also calculated using the Equation (5) [47]:  
\[THD_{u}=\sqrt{\frac{\sum_{h=2}^{40}{(U_{h})}^{2}}{U_{1}}}, \tag{5}\]  
where \(U_{h}\) represents the amplitude of each harmonic component compared to the fundamental voltage.