## 4 STATCOM Performance and Results
### Disintegration Loads  
Figure 7 shows that the starting nominal reactive power value is 0, and time reaches to 0.1 s. From 0.1 s, the variation of reference reactive power is moved to 20 MVAR, and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots until 0.15 s. The DC-Link voltage will start to decrease. Thus, the AC converter output voltage starts to decrease, then STATCOM will absorb the reactive power (\(Q_{S}^{*}\)) and, again, maintain the nominal reactive power value (i.e., 0) from 0.15 s to 0.2 s. The disintegration inductive load reactive power 40 MVAR is added at 0.20 s, and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots until 0.25 s. Again, STATCOM will absorb the reactive power (\(Q_{S}^{*}\)), and maintain the nominal reactive power value of 0 from 0.25 s to 0.3 s.  
Figure 5: Cumulative load performance results of seven level VSC based STATCOM with reference reactive power changes. Figure 6: STATCOM currents’ harmonic spectra during cumulative loads of inductive and capacitive operations. Thus, the disintegration inductive load reactive power 60 MVAR is observed at time 0.30 s, and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots till the time 0.35 s. Then, continuously, STATCOM will absorb the reactive power (\(Q_{S}^{*}\)) and maintain nominal reactive power value (i.e., 0) from 0.35 s to 0.4 s. Finally, the disintegration inductive load reactive power is moved to 80 MVAR at 0.40 s, and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots until 0.45 s. When \(Q_{S}^{*}\) is set to 80 MVAR, the DC-Link voltage will start to decreases. Thus, the AC converter output voltage starts to decrease. Therefore, STATCOM will consume the reactive power, and maintain the nominal reactive power value of 0 from 0.45 s to 0.5 s.  
The disintegration capacitive load starts at the time 0.5 s in the system, the reference reactive power is moved to \(-\)20 MVAR, and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots until 0.55 s. The DC-Link voltage will start to increase. Thus, the AC converter output voltage starts to increase, then STATCOM will deliver the reactive power (\(Q_{S}^{*}\)), and, again, maintain the nominal reactive power value of 0 from 0.55 s to 0.6 s. The disintegration capacitive load reactive power \(-\)40 MVAR is added at 0.60 s, and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots until 0.65 s. Again, STATCOM will deliver the reactive power (\(Q_{S}^{*}\)) and again maintain the nominal reactive power value (i.e., '0 ') from 0.65 s to 0.7 s.  
The disintegration capacitive load reactive power \(-\)60 MVAR is observed at the time 0.70, s and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots until 0.75 s. Then, continuously, STATCOM will deliver the reactive power (\(Q_{S}^{*}\)), and, again, maintain the nominal reactive power value (i.e., '0') from 0.75 s to 0.8 s. Finally, the disintegration capacitive load reactive power is moved to \(-\)80 MVAR at 0.80 s, and the actual reactive power (\(Q_{S}\)) flows in the system without any major overshoots until 0.85 s. When '\(Q_{S}^{*}\)' is set to \(-\)80 MVAR, then DC-Link voltage will start to increase. Thus, the AC converter output voltage starts to increase. Therefore, STATCOM will generate the reactive power and, again, maintain the nominal reactive power value of 0 from 0.85 s to 0.9 s.  
Figure 8 shows STATCOM currents' harmonic spectra during disintegration loads of inductive and capacitive operations. The THD of STATCOM currents is found to be 4.51% during the inductive operation when '\(Q_{S}^{*}\)' is set to 80 MVAR, as well as 5.41% during capacitive operation when '\(Q_{S}^{*}\)' is set to \(-\)80 MVAR. Figure 7: Disintegration loads performance results of seven level VSC based STATCOM with reference reactive power changes.