## 3 Results of Measurements
### Correlation between Current and Voltage Harmonics  
The source of harmonics in the voltage may be the current distortions caused, for example, by power electronic converters. Below, a current and voltage harmonic analysis will be presented for a representative measurement. The recording of parameters started after connecting the EVSE to the vehicle, and the charging process started approximately 3 min later. The recording of power parameters was completed approximately 3 min after vehicle charging was completed. The current harmonic distribution during this measurement is shown in Figure 3.  
In order to identify the reason for the occurrence of a significant DC component in the current, particularly in phase 3, an analysis of the variability of this component during charging was carried out, and the course of its share is shown in Figure 4.  
Figure 4: DC current component while charging the vehicle.  
Figure 3: THD\({}_{\text{i}}\) and individual current harmonic content for electric vehicles.  
A very large share of the DC component, over three times higher than fundamental harmonic for the state of the vehicle connected to the network but not being charged, may make voltage nonsinusoidal. However, it should be noticed that the measured effective value of the current drawn from the network during these periods is less than 10 mA. An analysis of harmonic current components was also performed, excluding the period when the vehicle is connected and not charged. Probably, this large share of the DC component is related to the EVSE communication process with the vehicle, which involves, among other things, powering the communication system in the EVSE and the need to \"issue\" a DC voltage of 9 V on the CP line, which has decreased to 6 V during the charging process [52].  
Taking the above into account, an analysis of current and voltage harmonics was also carried out, excluding the time before and after charging; i.e., the analysis concerned only the charging time. The voltage and current harmonic distribution for this case are shown in Figures 9 and 10, respectively.  
Figure 8: THDi and power transmitted to the vehicle at the end of the test (powers transmitted by each line are always the same, so overlapping of graph lines be observed).  
Figure 7: THDi and power transmitted to the vehicle at the beginning of the test.  
This analysis proves that while both the DC component and even the harmonics of the current occur during charging, their share in the voltage, and therefore in the power supply of neighboring loads, is negligible, and the largest contributions are made by harmonics of the following orders: 3, 5, and 7. The main goal of the analyses is to observe the impact of the vehicle charging process on the voltage supplying other loads in the installation; therefore, further considerations will be limited to the recorded voltage distortions.  
Figure 10: THD\({}_{\text{I}}\) and individual current harmonic content for electric vehicles (no-charging period at the beginning and end of process is excluded).  
Figure 9: THD\({}_{\text{U}}\) and individual current harmonic content for electric vehicle (no-charging period at the beginning and end of the process is excluded).