5.2.1. Single-Line to Ground Fault (The Fault Is Applied at Phase a)

The per unit rms terminal voltage of the BDFRG, as shown in Figure 13, at the instant of fault occurrence, the terminal voltage dropped to zero p.u. for 150 ms due to the occurrence of the studied single phase to ground fault, then after fault clearance, the terminal voltage returns to its original value (1 p.u.).

ondary currents were effectively improved.

**Figure 10.** Primary current of BDFRG without and with the proposed crowbar protection under symmetrical fault occurrence: (**a**). Without the proposed crowbar; (**b**). With the proposed crowbar. **Figure 10.** Primary current of BDFRG without and with the proposed crowbar protection under symmetrical fault occurrence: (**a**). Without the proposed crowbar; (**b**). With the proposed crowbar.

period. After the fault clearance, the primary current was increased to about 212% (19.74 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 216% (28.25 A) of the pre-fault value (13.05 A), while in the case of using the proposed crowbar, as shown in Figures 10b and 11b, after the fault clearance, both the primary and secondary currents were effectively improved. As the primary current increased to (15.25 A), while the secondary current increased to (22.86 A) and then quickly both the primary and sec-

**Figure 11.** Secondary current of BDFRG without and with the proposed crowbar protection under symmetrical fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar. **Figure 11.** Secondary current of BDFRG without and with the proposed crowbar protection under symmetrical fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar.

The dc link voltage of the BDFRG (with and without using the proposed crowbar) is shown in Figure 12, which has a reference value equals to 710 V. Under the fault occurrence, in the case of "without using the proposed crowbar", the dc link voltage was decreased to about 499.2 V. In the case of using the proposed crowbar, the dc link voltage decreased instantaneously to about 587.8 V only, then the dc link voltage improved and

returned quickly to its pre-fault value.

**700**

**750**

**800**

**Reference**

**Without the proposed crowbar**

**Crowbar resistance= 10 × secondary resistance**

**Figure 12.** DC link voltage of BDFRG with and without the proposed crowbar under symmetrical fault occurrence. **Figure 12.** DC link voltage of BDFRG with and without the proposed crowbar under symmetrical rence of the studied single phase to ground fault, then after fault clearance, the terminal voltage returns to its original value (1 p.u.).

**Figure 13.** Per unit rms terminal voltage (Va) of the studied wind farm main coupling point under single-line to ground fault occurrence. **Figure 13.** Per unit rms terminal voltage (Va) of the studied wind farm main coupling point under single-line to ground fault occurrence.

**0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 T i m e (s)** The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 14. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 3.78 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly returned to its pre-fault value. The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 14. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 3.78 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly returned to its pre-fault value.

**Figure 13.** Per unit rms terminal voltage (Va) of the studied wind farm main coupling point under single-line to ground fault occurrence. The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 14. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 3.78 kW. In the case of using the proposed The reactive power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 15. As shown, the reactive power was adjusted at zero value (unity power factor) before the fault occurrence. Following the clearance of the fault, in the case of "without using the proposed crowbar", the absorbed reactive power, by the BDFRG from the grid, reached about 2.115 kvar. In the case of using the proposed crowbar, after fault clearance, the absorbed reactive power was reduced to 1.158 kvar only and quickly improved until reaching its pre-fault value.

crowbar, during the fault, the active power was effectively improved and quickly re-

turned to its pre-fault value.

**-0.5**

**0**

**0.5**

**8**

**9**

**Without the proposed crowbar**

**Crowbar resistance= 10 × secondary resistance**

*Energies* **2022**, *15*, x FOR PEER REVIEW 12 of 29

**Figure 14.** Active power of BDFRG with and without the proposed crowbar under single-line to ground fault occurrence. **Figure 14.** Active power of BDFRG with and without the proposed crowbar under single-line to ground fault occurrence. clearance, the absorbed reactive power was reduced to 1.158 kvar only and quickly improved until reaching its pre-fault value.

**Figure 15.** Reactive power of BDFRG with and without the proposed crowbar under single-line to ground fault occurrence. **Figure 15.** Reactive power of BDFRG with and without the proposed crowbar under single-line to ground fault occurrence.

**Figure 15.** Reactive power of BDFRG with and without the proposed crowbar under single-line to **0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 T i m e (s) Without the proposed crowbar Crowbar resistance= 10 × secondary resistance** The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 16, which has a reference value equals to 1160 rpm. During fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated and the rotor The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 16, which has a reference value equals to 1160 rpm. During fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated and the rotor speed reached about 1184 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4794 as shown in Figure 17. In the case of using the proposed crowbar, the rotor speed increased instantaneously to about 1186 rpm, but with damped oscillations than in the other case, then quickly improved.

> The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 16, which has a reference value equals to 1160 rpm. During fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated and the rotor

ground fault occurrence.

**-2.5**

**-2**

**-1.5**

**-1**

oscillations than in the other case, then quickly improved.

oscillations than in the other case, then quickly improved.

*Energies* **2022**, *15*, x FOR PEER REVIEW 13 of 29

**Figure 16.** Rotor speed of BDFRG with and without the proposed crowbar under single line to ground fault occurrence. **Figure 16.** Rotor speed of BDFRG with and without the proposed crowbar under single line to ground fault occurrence. ground fault occurrence.

**Figure 16.** Rotor speed of BDFRG with and without the proposed crowbar under single line to

speed reached about 1184 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4794 as shown in Figure 17. In the case of using the proposed crowbar, the rotor speed increased instantaneously to about 1186 rpm, but with damped

speed reached about 1184 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4794 as shown in Figure 17. In the case of using the proposed crowbar, the rotor speed increased instantaneously to about 1186 rpm, but with damped

**Figure 17.** Power coefficient of wind turbine with and without the proposed crowbar under single-**T i m e (s) Figure 17.** Power coefficient of wind turbine with and without the proposed crowbar under singleline to ground fault. **Figure 17.** Power coefficient of wind turbine with and without the proposed crowbar under single-line to ground fault.

line to ground fault. The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 18 and 19 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased, the primary current was increased to about 190% (17.68 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 181% (23.58 A) of the pre-fault value (13.05 A), The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 18 and 19 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased, the primary current was increased to about 190% (17.68 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 181% (23.58 A) of the pre-fault value (13.05 A), The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 18 and 19 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased, the primary current was increased to about 190% (17.68 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 181% (23.58 A) of the pre-fault value (13.05 A), while in the case of using the proposed crowbar, as shown in Figures 18b and 19b, during the fault, both the primary and secondary currents were effectively improved.

**Figure 18.** Primary current of BDFRG without and with the proposed crowbar protection under single-line to ground fault: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar. **Figure 18.** Primary current of BDFRG without and with the proposed crowbar protection under single-line to ground fault: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar.

while in the case of using the proposed crowbar, as shown in Figures 18b and 19b, during

the fault, both the primary and secondary currents were effectively improved.

The dc link voltage of the BDFRG (with and without using the proposed crowbar) is shown in Figure 20, which has a reference value equal to 710 V. Under the fault occurrence, in the case of "without using the proposed crowbar", the dc link voltage was decreased to about 642 V. In the case of using the proposed crowbar, the dc link voltage increased to about 800 V, but with damped oscillations than in the other case, then the dc link voltage improved and returned to its pre-fault value.

5.2.2. Line to Line Fault (The Fault Is Applied at Phases a and b)

The per unit rms terminal voltage of the BDFRG, as shown in Figure 21, at the instant of fault occurrence, the terminal voltage dropped to 0.5 p.u. for 150 ms due to the occurrence of the studied line to line fault, then after fault clearance, the terminal voltage returns to its original value (1 p.u.).

**Figure 19.** Secondary current of BDFRG without and with the proposed crowbar under single-line to ground fault: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar **Figure 19.** Secondary current of BDFRG without and with the proposed crowbar under single-line to ground fault: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar.

The dc link voltage of the BDFRG (with and without using the proposed crowbar) is shown in Figure 20, which has a reference value equal to 710 V. Under the fault occurrence, in the case of "without using the proposed crowbar", the dc link voltage was decreased to about 642 V. In the case of using the proposed crowbar, the dc link voltage increased to about 800 V, but with damped oscillations than in the other case, then the dc The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 22. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 1.99 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly returned to its pre-fault value.

link voltage improved and returned to its pre-fault value.

**760**

**800**

**820**

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**Figure 20.** DC link voltage of BDFRG with and without the proposed crowbar under single-line to ground fault occurrence. **Figure 20.** DC link voltage of BDFRG with and without the proposed crowbar under single-line to ground fault occurrence. turns to its original value (1 p.u.).

**Reference**

**Without the proposed crowbar**

**Crowbar resistance= 10 × secondary resistance**

**Figure 21.** Per unit rms terminal voltage (Va) of the studied wind farm main coupling point under line to line fault occurrence. **Figure 21.** Per unit rms terminal voltage (Va) of the studied wind farm main coupling point under line to line fault occurrence.

**Figure 21.** Per unit rms terminal voltage (Va) of the studied wind farm main coupling point under line to line fault occurrence. **0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 T i m e (s)** The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 22. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 1.99 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly returned to its pre-fault value. The reactive power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 23. As shown, the reactive power was adjusted at zero value (unity power factor) before the fault occurrence. Following the clearance of the fault, in the case of "without using the proposed crowbar", the absorbed reactive power, by the BDFRG from the grid, reached about 3.364 kvar for a certain period. In the case of using the proposed crowbar, after fault clearance, the absorbed reactive power was reduced to 1.325 kvar only and quickly improved until reaching its pre-fault value.

> The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 22. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 1.99 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly re-

turned to its pre-fault value.

**-0.5**

**0**

**6**

**7**

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**Figure 22.** Active power of BDFRG with and without the proposed crowbar under line to line fault occurrence. **Figure 22.** Active power of BDFRG with and without the proposed crowbar under line to line fault occurrence. and quickly improved until reaching its pre-fault value.

**Figure 23.** Reactive power of BDFRG with and without the proposed crowbar under line-to-line fault occurrence. **Figure 23.** Reactive power of BDFRG with and without the proposed crowbar under line-to-line fault occurrence.

**Figure 23.** Reactive power of BDFRG with and without the proposed crowbar under line-to-line **0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4 T i m e (s) Without the proposed crowbar Crowbar resistance= 10 × secondary resistance** The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 24, which has a reference value equal to 1160 rpm. During the fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated and the The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 24, which has a reference value equal to 1160 rpm. During the fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated and the rotor speed reached about 1196 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4787 as shown in Figure 25. In the case of using the proposed crowbar, the rotor speed increased instantaneously to about 1198 rpm, but with damped oscillations than in the other case, then quickly improved.

> The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 24, which has a reference value equal to 1160 rpm. During the fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated and the

fault occurrence.

**-3.5**

**-3**

**-2.5**

**-2**

**-1.5**

damped oscillations than in the other case, then quickly improved.

damped oscillations than in the other case, then quickly improved.

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**Figure 24.** Rotor speed of BDFRG with and without the proposed crowbar under line to line fault occurrence. **Figure 24.** Rotor speed of BDFRG with and without the proposed crowbar under line to line fault occurrence. occurrence.

**Figure 24.** Rotor speed of BDFRG with and without the proposed crowbar under line to line fault

rotor speed reached about 1196 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4787 as shown in Figure 25. In the case of using the proposed crowbar, the rotor speed increased instantaneously to about 1198 rpm, but with

rotor speed reached about 1196 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4787 as shown in Figure 25. In the case of using the proposed crowbar, the rotor speed increased instantaneously to about 1198 rpm, but with

**T i m e (s)**

**Figure 25.** Power coefficient of wind turbine with and without the proposed crowbar under line to **Figure 25.** Power coefficient of wind turbine with and without the proposed crowbar under line to line fault occurrence. **Figure 25.** Power coefficient of wind turbine with and without the proposed crowbar under line to line fault occurrence.

line fault occurrence. The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 26 and 27 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased; the primary current was increased to about 220% (20.47 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 215% (28.04 A) of the pre-fault value (13.05 A), The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 26 and 27 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased; the primary current was increased to about 220% (20.47 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 215% (28.04 A) of the pre-fault value (13.05 A), The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 26 and 27 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased; the primary current was increased to about 220% (20.47 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 215% (28.04 A) of the pre-fault value (13.05 A), while in the case of using the proposed crowbar, as shown in Figures 26b and 27b, during the fault, both the primary and secondary currents were effectively improved.

**Figure 26.** Primary current of BDFRG without and with the proposed crowbar under line to line fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar. **Figure 26.** Primary current of BDFRG without and with the proposed crowbar under line to line fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar.

while in the case of using the proposed crowbar, as shown in Figures 26b and 27b, during

the fault, both the primary and secondary currents were effectively improved.

**Figure 27.** Secondary current of BDFRG without and with the proposed crowbar under line-to-line fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar. **Figure 27.** Secondary current of BDFRG without and with the proposed crowbar under line-to-line fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar.

The dc link voltage of the BDFRG (with and without using the proposed crowbar) is shown in Figure 28, which has a reference value equal to 710 V. Under the fault occurrence, in the case of "without using the proposed crowbar", the dc link voltage was decreased to about 584 V. In the case of using the proposed crowbar, the dc link voltage, during the fault, at first decreased to 690.5 V and then increased to about 777 V, then the dc link voltage improved and returned to its pre-fault value. The dc link voltage of the BDFRG (with and without using the proposed crowbar) is shown in Figure 28, which has a reference value equal to 710 V. Under the fault occurrence, in the case of "without using the proposed crowbar", the dc link voltage was decreased to about 584 V. In the case of using the proposed crowbar, the dc link voltage, during the fault, at first decreased to 690.5 V and then increased to about 777 V, then the dc link voltage improved and returned to its pre-fault value.

*Energies* **2022**, *15*, x FOR PEER REVIEW 21 of 29

**Figure 28.** DC link voltage of BDFRG with and without the proposed crowbar under line-to-line fault occurrence. **Figure 28.** DC link voltage of BDFRG with and without the proposed crowbar under line-to-line fault occurrence. fault occurrence. 5.2.3. Double Line to Ground Fault (The Fault Is Applied at Phases a and b)

5.2.3. Double Line to Ground Fault (The Fault Is Applied at Phases a and b) 5.2.3. Double Line to Ground Fault (The Fault Is Applied at Phases a and b) The per unit rms terminal voltage (Va) of the BDFRG, as shown in Figure 29, at the

The per unit rms terminal voltage (Va) of the BDFRG, as shown in Figure 29, at the instant of fault occurrence, the terminal voltage dropped to zero p.u. for 150 ms due to the occurrence of the studied double line to ground fault; then, after fault clearance, the terminal voltage returns to its original value (1 p.u.). The per unit rms terminal voltage (Va) of the BDFRG, as shown in Figure 29, at the instant of fault occurrence, the terminal voltage dropped to zero p.u. for 150 ms due to the occurrence of the studied double line to ground fault; then, after fault clearance, the terminal voltage returns to its original value (1 p.u.). instant of fault occurrence, the terminal voltage dropped to zero p.u. for 150 ms due to the occurrence of the studied double line to ground fault; then, after fault clearance, the terminal voltage returns to its original value (1 p.u.).

**0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4**

**Figure 29.** Per unit rms terminal voltage of the studied wind farm main coupling point under double **T i m e (s) Figure 29.** Per unit rms terminal voltage of the studied wind farm main coupling point under double line to ground fault occurrence. **Figure 29.** Per unit rms terminal voltage of the studied wind farm main coupling point under double line to ground fault occurrence.

line to ground fault occurrence. The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 30. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 1.373 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly re-The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 30. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 1.373 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly returned to its pre-fault value. The active power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 30. As obvious in the case of "without using the proposed crowbar", during the fault, the active power dropped to 1.373 kW. In the case of using the proposed crowbar, during the fault, the active power was effectively improved and quickly returned to its pre-fault value.

turned to its pre-fault value.

**Without the proposed crowbar**

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**Figure 30.** Active power of BDFRG with and without the proposed crowbar under double line to ground fault occurrence. **Figure 30.** Active power of BDFRG with and without the proposed crowbar under double line to ground fault occurrence. ground fault occurrence. The reactive power of the BDFRG (with and without using the proposed crowbar) is

The reactive power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 31. As shown, the reactive power was adjusted at zero value (unity power factor) before the fault occurrence. Following the clearance of the fault, in the case of "without using the proposed crowbar", the absorbed reactive power, by the BDFRG from the grid, reached about 5.15 kvar for a certain period. In the case of using the proposed crowbar, after fault clearance, the absorbed reactive power was reduced to 1.63 kvar only and quickly improved until reaching its pre-fault value. The reactive power of the BDFRG (with and without using the proposed crowbar) is shown in Figure 31. As shown, the reactive power was adjusted at zero value (unity power factor) before the fault occurrence. Following the clearance of the fault, in the case of "without using the proposed crowbar", the absorbed reactive power, by the BDFRG from the grid, reached about 5.15 kvar for a certain period. In the case of using the proposed crowbar, after fault clearance, the absorbed reactive power was reduced to 1.63 kvar only and quickly improved until reaching its pre-fault value. shown in Figure 31. As shown, the reactive power was adjusted at zero value (unity power factor) before the fault occurrence. Following the clearance of the fault, in the case of "without using the proposed crowbar", the absorbed reactive power, by the BDFRG from the grid, reached about 5.15 kvar for a certain period. In the case of using the proposed crowbar, after fault clearance, the absorbed reactive power was reduced to 1.63 kvar only and quickly improved until reaching its pre-fault value.

**0.9 0.95 1 1.05 1.1 1.15 1.2 1.25 1.3 1.35 1.4**

**Figure 31.** Reactive power of BDFRG with and without the proposed crowbar under double line to **T i m e (s) Figure 31.** Reactive power of BDFRG with and without the proposed crowbar under double line to ground fault occurrence. **Figure 31.** Reactive power of BDFRG with and without the proposed crowbar under double line to ground fault occurrence.

ground fault occurrence. The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 32, which has a reference value equals to 1160 rpm. During the fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated; then, The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 32, which has a reference value equals to 1160 rpm. During the fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated; then, The rotor speed of the BDFRG (with and without using the proposed crowbar) is shown in Figure 32, which has a reference value equals to 1160 rpm. During the fault, in the case of "without using the proposed crowbar", the rotor rapidly accelerated; then, after fault clearance, the rotor speed reached about 1294 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4605 as shown in Figure 33. While in

*Energies* **2022**, *15*, x FOR PEER REVIEW 23 of 29

about 1206 rpm, then quickly improved.

*Energies* **2022**, *15*, x FOR PEER REVIEW 23 of 29

the case of using the proposed crowbar, the rotor speed increased instantaneously to about 1206 rpm, then quickly improved. about 1206 rpm, then quickly improved.

after fault clearance, the rotor speed reached about 1294 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4605 as shown in Figure 33. While in the case of using the proposed crowbar, the rotor speed increased instantaneously to

after fault clearance, the rotor speed reached about 1294 rpm, which led to a decrease in the power coefficient of the WT from 0.48 to less than 0.4605 as shown in Figure 33. While in the case of using the proposed crowbar, the rotor speed increased instantaneously to

**Figure 32.** Rotor speed of BDFRG with and without the proposed crowbar under double line to ground fault occurrence. **Figure 32.** Rotor speed of BDFRG with and without the proposed crowbar under double line to ground fault occurrence. **Figure 32.** Rotor speed of BDFRG with and without the proposed crowbar under double line to ground fault occurrence.

**T i m e (s)**

line to ground fault occurrence.

**Figure 33.** Power coefficient of wind turbine with and without the proposed crowbar under double **Figure 33.** Power coefficient of wind turbine with and without the proposed crowbar under double line to ground fault occurrence. **Figure 33.** Power coefficient of wind turbine with and without the proposed crowbar under double line to ground fault occurrence.

The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 34 and 35 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased; the primary current was increased to about 233% (21.69 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 224% (29.29 A) of the pre-fault value (13.05 A), The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 34 and 35 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased; the primary current was increased to about 233% (21.69 A) of the pre-fault value (9.32 A)and the secondary current was increased to about 224% (29.29 A) of the pre-fault value (13.05 A), The primary and secondary currents of the BDFRG (without and with using the proposed crowbar) are shown in Figures 34 and 35 in the same order. In the case of "without using the proposed crowbar", during the fault, both currents were increased; the primary current was increased to about 233% (21.69 A) of the pre-fault value (9.32 A) and the secondary current was increased to about 224% (29.29 A) of the pre-fault value (13.05 A), while in the case of using the proposed crowbar, as shown in Figures 34b and 35b, during the fault, both the primary and secondary currents were effectively improved.

**Figure 34.** Primary current of BDFRG without and with the proposed crowbar under double line to ground fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar. **Figure 34.** Primary current of BDFRG without and with the proposed crowbar under double line to ground fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar.

while in the case of using the proposed crowbar, as shown in Figures 34b and 35b, during

the fault, both the primary and secondary currents were effectively improved.

**Figure 35.** Secondary current of BDFRG without and with the proposed crowbar under double line to ground fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar. **Figure 35.** Secondary current of BDFRG without and with the proposed crowbar under double line to ground fault occurrence: (**a**) Without the proposed crowbar; (**b**) With the proposed crowbar.

The dc link voltage of the BDFRG (with and without using the proposed crowbar) is shown in Figure 36, which has a reference value equal to 710 V. Under the fault occurrence, in the case of "without using the proposed crowbar", the dc link voltage was decreased to about 595.5 V. In the case of using the proposed crowbar, the dc link voltage, during the fault, at first decreased to 667.2 V and then increased to about 766.4 V; then, the dc link voltage improved and returned to its pre-fault value. The dc link voltage of the BDFRG (with and without using the proposed crowbar) is shown in Figure 36, which has a reference value equal to 710 V. Under the fault occurrence, in the case of "without using the proposed crowbar", the dc link voltage was decreased to about 595.5 V. In the case of using the proposed crowbar, the dc link voltage, during the fault, at first decreased to 667.2 V and then increased to about 766.4 V; then, the dc link voltage improved and returned to its pre-fault value.

**Figure 36.** DC link voltage of BDFRG with and without the proposed crowbar under double line to ground fault occurrence. **Figure 36.** DC link voltage of BDFRG with and without the proposed crowbar under double line to ground fault occurrence.

#### **6. Conclusions 6. Conclusions**

To improve the capability of the BDFRG WTs to satisfy the grid code requirements concerning remaining the wind turbines connected to the grid under the occurrence of grid disturbances, many complex and expensive techniques were used such as using AN-FIS control systems. This work proposes a new controllable crowbar as a new simple and economic solution to enhance the performance of the BDFRG WT under the occurrence of heavy faults. To examine the efficacy of the proposed controllable crowbar, the performance of the BDFRG WT under the occurrence of heavy different types of faults was studied twice, one without using the proposed controllable crowbar and the other with using it. To ensure that the proposed crowbar would be examined under the most extreme fault conditions, the location of the studied faults was chosen at the beginning of the transmission line next to the "wind farm" main point of common coupling. Not only that, but also to ensure accurate monitoring of the total actual performance of the BDFRG WT under the studied faults, all the protection system devices were deactivated. The terminal voltage, active power, reactive power, rotor speed, power coefficient, primary current of the BDFRG, secondary current of the BDFRG and DC link voltage were monitored and analyzed. Simulation results showed that in the case of fault occurrence without using the proposed controllable crowbar, all the monitored parameters were badly affected and the BDFRG WT would be rapidly disconnected from the network. On the other hand, simulation results showed that the proposed controllable crowbar effectively improved all the To improve the capability of the BDFRG WTs to satisfy the grid code requirements concerning remaining the wind turbines connected to the grid under the occurrence of grid disturbances, many complex and expensive techniques were used such as using ANFIS control systems. This work proposes a new controllable crowbar as a new simple and economic solution to enhance the performance of the BDFRG WT under the occurrence of heavy faults. To examine the efficacy of the proposed controllable crowbar, the performance of the BDFRG WT under the occurrence of heavy different types of faults was studied twice, one without using the proposed controllable crowbar and the other with using it. To ensure that the proposed crowbar would be examined under the most extreme fault conditions, the location of the studied faults was chosen at the beginning of the transmission line next to the "wind farm" main point of common coupling. Not only that, but also to ensure accurate monitoring of the total actual performance of the BDFRG WT under the studied faults, all the protection system devices were deactivated. The terminal voltage, active power, reactive power, rotor speed, power coefficient, primary current of the BDFRG, secondary current of the BDFRG and DC link voltage were monitored and analyzed. Simulation results showed that in the case of fault occurrence without using the proposed controllable crowbar, all the monitored parameters were badly affected and the BDFRG WT would be rapidly disconnected from the network. On the other hand, simulation results showed that the proposed controllable crowbar effectively improved all the monitored parameters and enabled the studied BDFRG WT to remain in service under the studied faults.

studied faults. **Author Contributions:** Conceptualization, M.R. and M.N.; methodology, M.R. and M.N.; software, M.R. and M.N.; validation, M.R., M.N. and A.E.-S.; formal analysis, M.R. and M.N.; investigation, M.R. M.N., and A. E.; resources, M.R., A. E., A.E.-S. and M.N.; data curation, M.R. and M.N.; writing—original draft preparation, M.R. and M.N.; writing—review and editing, M.R. M.N. A. E and **Author Contributions:** Conceptualization, M.R. and M.N.; methodology, M.R. and M.N.; software, M.R. and M.N.; validation, M.R., M.N. and A.E.-S.; formal analysis, M.R. and M.N.; investigation, M.R., M.N. and A.E.-S.; resources, M.R., A.E.-S. and M.N.; data curation, M.R. and M.N.; writing original draft preparation, M.R. and M.N.; writing—review and editing, M.R., M.N. and B.H., A.E.-S.;visualization, M.R.; supervision, A.E.-S., M.R. and B.H.; project administration, A.E.-S.; funding acquisition, A.E.-S. All authors have read and agreed to the published version of the manuscript.

monitored parameters and enabled the studied BDFRG WT to remain in service under the

B.H., A.E.-S.; visualization, M.R.; supervision, A. E., M.R. and B.H.; project administration, A.E.-S.; funding acquisition, A.E.-S. All authors have read and agreed to the published version of the man-**Funding:** This research received no external funding.

uscript. **Institutional Review Board Statement:** Not applicable.

**Institutional Review Board Statement:** Not applicable.

**Funding:** This research received no external funding. **Informed Consent Statement:** Not applicable.

**Data Availability Statement:** The data presented in this study are available on request from the corresponding author. The data are not publicly available due to their large size.

**Conflicts of Interest:** The authors declare no conflict of interest.
