## 2 Materials and Methods
This is typically expressed as a ratio or percentage. Where \(U_{1}\) is the amplitude (generally expressed as an RMS value) of the fundamental frequency component of the signal, and \(h\) is the order of the harmonic. The main difference between THD and individual harmonics is that THD is a metric used to measure the harmonic performance of a system, device, or circuit. In contrast, individual harmonics are frequency components produced in addition to the main frequency of a signal. It is typically expressed as a percentage and indicates how much the signal is distorted. A low THD value means high signal integrity and less distortion [48; 49]. In this study, Equation (6) was used to calculate the THD value:  
\[THD=\sqrt{\sum_{h=2}^{50}{(u_{h})}^{2}}, \tag{6}\]  
where THD is the harmonic distortion factor of the supply voltage, \(u_{h}\) is the relative value of the voltage of the fundamental component expressed as a percentage of the supply voltage, and \(h\) is the higher harmonic order. Also, the relative contribution of individual harmonics was analyzed via Equation (7):  
\[u_{h}=\frac{U_{h}}{U_{1}}\cdot 100\%. \tag{7}\]  
It was verified as to whether THD and individual harmonics did not exceed the available levels defined by legal acts [50]. The permissible harmonic content cannot exceed 8%, while individual harmonics cannot exceed the levels shown in Table 1.  
For the purpose of carrying out the tests, a measuring stand equipped with 22 kW electric vehicle service equipment (EVSE), commonly named the AC charger, was developed. The station has been equipped with the necessary number of single- and three-phase sockets, which allows it to be powered from any point (chains socket) of the LV network using a single cable. The station is also equipped with Fluke 434-II and 435-II Power  
\begin{table}
\begin{tabular}{c c c c c c} \hline \multicolumn{5}{c}{**Odd Harmonic**} & \multicolumn{2}{c}{**Even Harmonic**} \\ \hline \multicolumn{5}{c}{**Not Being a Multiplicity of 3**} & \multicolumn{2}{c}{**Being a Multiplicity of 3**} & \multicolumn{2}{c}{**Relative Voltage**} \\ \hline \multirow{4}{*}{**Harmonic Order**} & **Relative Voltage** & & **Relative Voltage as a** & **Value as a** & **Pla** **Amonic Order** & **Percentage of the** \\  & **Percentage of the** & **Harmonic Order** & **Percentage of the** & **Percentage of the** & **Fundamental** & **Component [\(u_{h}\)]** \\  & **Component [\(u_{h}\)]** & & & **Component [\(u_{h}\)]** & & \\ \hline
5 & 6\% & 3 & 5\% & 2 & 2\% \\
7 & 5\% & 9 & 1.5\% & 4 & 1\% \\
11 & 3.5\% & 15 & 0.5\% & \textgreater{}4  
Quality Analyzers (Fluke Corporation, Everett, WA, USA). These analyzers were used for measuring the parameters of the electrical energy transferred to the vehicle during charging. The obtained test results were used to analyze power and energy consumption, as well as to show the impact of the charging process of electric vehicles on the harmonic content in current and voltage. They were provided for all three phases and helped identify the sources of power quality issues. The analyzers were also used for the continuous recording of selected electrical parameters. View of test setup is presented on Figure 1.  
During the test, conditions similar to the typical method of using the EVs were maintained. The following conditions were considered: we started charging the vehicle when the battery's SoC level was at the level of 20%, and charging started immediately after the end of the journey. The only exception was charging the battery to 100% instead of 80% or 90% SoC as recommended by vehicle producers. It was assumed that this would be charging while traveling, and therefore the maximum power of the car's on-board charger (or supplied with the scooter) was used. The tests (registration of parameters) were completed when the on-board charger cut off the power supply. On-board charging involves a charger within the EV that converts externally supplied AC to DC, enabling the vehicle's battery to be charged.