## 5 Experimental Results and Analysis  
This section details the experimental results achieved with both conventional setups and those using the proposed control algorithm. During the experiment, the grid fault and various orders of harmonics voltage generation were emulated using the three-phase programmable AC power supply. A controller using a PLXIM's RT box was responsible for overall system control and signal processing. RT boxes have a rapid control prototype, providing them with a distinct advantage over conventional controllers that use a DSP MCU chip. SEMIKRON's IGBT module stack was used as an inverter, and a virtual EV's battery was simulated using a DC power supply. This experimental setup is shown in Figure 11.  
Figure 10: Simulation results of actual grid voltage and grid voltage using an observer. Figure 12a,b show the measured stationary reference frame grid currents and grid voltages when current control methods were used with and without CFFC and DRC. According to our experimental results, grid currents were properly controlled through with methods in the absence of grid fault. The total harmonic distortion (THD) of the experimental results shown in Figure 12 is summarized in Table 5.  
Figure 11: GCI experimental set-up for EV’s application. Figure 12: When normal grid condition, experimental results of proposed method a stationary reference frame grid currents and grid voltages (**a**) without CFFC and DRC and (**b**) with CFFC and DRC. According to international standards (e.g., IEEE 519), THD must be within 5% to be allowed to be connected to the distribution system. In grid normal conditions, the phase current THD before applying the proposed CFFC and DRC was approximately 4.8%. While this margin of 0.2[%] is less than the IEEE 519 standard requires, after application of our proposed method, THD dropped to 3.6%, resulting in a superior margin of approximately 1.4%. Figure 13 shows the frequency spectrum for the grid current depicted in Figure 12. Based on these results, harmonic distortion of phase current was analyzed with reference to IEEE 519. Total harmonic distortion before application of the proposed method had a THD margin of 0.2%, which satisfies IEEE 519, but exceeded the individual harmonic distortion IEEE 519 standard of 3%. With application of the proposed CFFC and DRC method, individual harmonic distortion of less than 3% was achieved as shown in Figure 13.  
Figure 14 shows the results of current control in the circumstance of line to ground fault. While there is no current trip-related standard, the average commercial inverter has a trip standard of 200-250%. When a grid fault occurs, the peak current generated in the transient state for an inverter with a  
Figure 13: Under normal grid conditions, the frequency spectrums of the stationary reference frame grid currents (**a**) without CFFC and DRC and (**b**) with CFFC and DRC. \begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Control Algorithm**} & \multicolumn{3}{c}{**Total Harmonic Distortion (THD)**} \\ \cline{2-4}  & **Without** & **With** & **Reduction Ratio** \\  & **CFFC and DRC** & **CFFC and DRC** & **Reduction Ratio** \\ \hline Proposed method & 4.8 [\%] & 3.6 [\%] & 1.2 [\%] \\ \hline \hline \end{tabular}
\end{table} 
Table 5: Experiment results of GCI system phase current total harmonic distortion (THD) in normal grid condition. trip condition of 201% without the proposed CFFC and DRC applied is 201%. With application of the proposed CFFC and DRC, the peak current generated was reduced by 17.7% to 183.3%, leaving a margin of 16.7% before the trip condition was triggered. Moreover, when the proposed CFFC and DRC were used, transient time was reduced by about half (reduction of approximately 0.03 s). The experimental results of transient response are summarized in Table 6.  
When 5 th and 7 th harmonics are added by nonlinear loads or machine connection to the grid, THD may exceed 5% in order to connect to a distribution system stated at IEEE 519 standard.