## 3 Experimental Analysis of the Reactive Power in Nowadays Power Distribution Lines
### The Reactive Power in PDL Loaded by SIMOVERT P 6 SE21 VFD  
The SIMOVERT P 6 SE21 VFD is factory-fitted with a relatively high-capacity DC circuit capacitor--470 uF. Therefore, this VFD, unlike the VFDs studied in Section 3.4 and presented in [4], provides leading reactive power only at the maximum high induction motor voltage frequency (67-80 Hz). However, by connecting additional capacitors to the SIMOVERT P 6 SE21 VFD DC circuit, the reactive power provided or drawn out by the VFD becomes lagging over the entire frequency range of the induction motor voltage. This is clearly seen in the diagrams in Figure 18a. The results of the experiment show that with natural PDL internal resistance and inductance and a factory-fitted DC circuit capacitor, the VFD consumes lagging active power only up to a certain load level. By increasing the load on the VFD above this level, the VFD begins to provide leading reactive power. In order for the VFD to remain a consumer of lagging reactive power and to be able to compensate the leading reactive power provided by the LED, the capacitance of the DC circuit capacitors must be increased. In addition, an experiment with SIMOVERT P 6 SE21 VFD showed that the additional capacitors in the DC circuit have no real effect on the active power. Figure 16: Active and reactive power provided or drawn out by Siemens Micromaster 420 single-phase diode rectifier supply-side VFD as a function of VFD frequency. Compensation of Reactive Power Provided by LED Light Devices by SIMOVERT P 6 SE21 VFD Fitted by Additional Capacitance in DC Circuit  
This experimental study was performed to test the ability of SIMOVERT P 6 SE21 VFD to compensate for the reactive power provided by LED light devices. According to the study described in Section 3.1, all experimentally investigated LED light devices provide leading reactive power. This is confirmed by the data published in [2]. According to the results of the study described in Section 4.1, additional capacitors in the VFD DC circuit convert the VFD into a lagging reactive power source. It was assumed that the reactive power provided by the LED light devices connected to the PDL would have to be compensated by the aforementioned VFD. This assumption was tested experimentally. The study was performed by connecting five different power and color temperature LED light devices and SIMOVERT P 6 SE21 VFD to PDL. Data were collected at the point of connection of these devices to the PDL. The results of the experimental study are presented in Figure 19.  
Figure 17: Circuit diagram of experimental setup for the reactive power provided or drawn out by diode rectifier supply-side variable frequency drive and LED light devices analysis. Figure 18: The power at the point of SIMOVERT P 6 SE21 VFD connection to PDL at a function of induction motor frequency in case of different DC circuit capacitance value: (**a**) reactive power; (**b**) active power. As can be seen from the results of the experimental study in Figure 19a, using the SIMOVERT P 6 SE21 VFD only with a factory-fitted 470 mF capacitor, we have the leading reactive power over the entire frequency range of the induction motor voltage. With the factory-fitted 470 mF capacitor, the SIMOVERT P 6 SE21 VFD does not compensate the reactive power provided by the LED. By connecting additional capacitors in the VFD DC circuit and increasing the capacity to 705 uF, the SIMOVERT P 6 SE21 VFD becomes able to compensate the reactive power provided by the LED in the frequency range between 30 and 70 Hz. However, it is not capable of the remaining frequency range. By connecting additional capacitors to the VFD DC circuit and increasing the capacity to 815 uF, the SIMOVERT P 6 SE21 VFD becomes able to compensate the reactive power provided by the LED over the entire voltage frequency range of the induction motor. It is also found that the additional capacitors in the SIMOVERT P 6 SE21 VFD DC circuit do not affect the active power.