# Fault Analysis of a Small PV/Wind Farm Hybrid System Connected to the Grid
## 5 Results and Simulation
### With Fault  
Three lines to ground fault is a condition that occurs frequently in industrial settings and is actually quite harmful for converters built using power electronics. The voltage dip and excess current flow must be managed to prevent any device damage due to the semiconductor devices' quick response times [36]. On the transmission line, an LLLG fault with a 0.1 s fault duration occurred at time t = 6 s. The LLLG fault's impact on the parameters of a PV panel is shown in Figure 22. It is obvious that during the fault, the PV array's voltage, current, and maximum output power are reduced; nevertheless, after 6.1 s, these parameters returned to normal value. Figure 23 depicts how the DC voltage the DC converter delivers is disturbed from 6 to 6.1 s into the LLLG fault. The controller has the capacity to manage the disturbance, causing the voltage to stabilize at 500 V in just 6.1 s. The DC voltage abruptly increases at 6 s from 500 V to 1545 V before dropping to 490 V before the fault is cleared. Without a pitch angle controller, the rotor speed climbs to high values during grid disturbances, as seen in Figure 24. At this point, the rotor speed can be stabilized with the use of the pitch angle controller. It is evident that following the occurrence of the fault, the rotor speed stabilizes. Consequently, the pitch angle controller contributes to the stability of rotor speed. The behavior of the PCC bus's three-phase voltage throughout an LLLG fault is shown in Figure 25. The voltage is kept at 20 kV prior to the start of the incident (max). The voltage at the grid is 0 for 6 to 6.1 s during the LLLG fault. The voltage returned to normal after 6.1 s. The outcome reveals that the inverter was shut down between the seconds of 6 and 6.1. Figure 26 depicts the three-phase current behavior of the PCC bus during the LLLG fault. It shows that the current was settled at 224 A before to the fault's beginning and increased to 1000 A with the injection of the fault at 6 s. After the faulty period, the current finally restores to its regular value of 224 A. The outcome demonstrates that current increases abruptly to 1000 A during the faulty period and then decreases to the steady state at a time instant of roughly 7 s. Figure 27 displays the PCC bus's receipt of active and reactive power during the faulted duration. It has been demonstrated through modeling and actual experiences that the real and reactive power supplied into the PCC bus are also disrupted during the LLLG fault between the seconds of 6 and 6.1. The active power delivered into the PCC bus is zero during the faulty period. Additionally, it can be seen that there is a power surge right after the fault is cleared, which causes the converter to transport more power and strains the devices. Reactive power is one of the parameters that is least altered after an LLLG malfunction. A spike is noticed immediately once the fault was fixed, and within 7 s it returned to normal value.  
Figure 22: PV panel parameters with LLLG fault.  
Figure 23: DC link voltage with LLLG fault.  
Figure 24: Rotor speed without and with pitch angle controller during LLLG fault.  
Figure 25: Voltage of PCC bus with LLLG fault.