**3. Proposed Protection Control System**

The controller design for the PMSG is very important in high performance applications. The design procedure for synthesizing and applying the controllers is very similar to the controllers in other high performance generators. However, the IT-2 FLC has more features than conventional control systems, such as numerical uncertainties and modeling the uncertainties in linguistic variables. The parameters of the PI are difficult to adjust for a WECS based on high nonlinearity with uncertain operating conditions. The PI controller supplies the proper performance for a given operating point. However, new methods have been investigated to overcome numerical uncertainties and new linguistics. The type-2 fuzzy set is a new method with specific characteristics. Thus, the special characteristics of the IT-2 FLC are used to improve wind energy conversion systems in this study. The block diagram for the IT-2 FLC is given in Figure 1. An open source interval type-2 fuzzy logic system (IT2-FLS) Matlab/Simulink (R2106a, MathWorks, Natick, Massachusetts, USA) toolbox produced by Taskin and Kumbasar [31] was used in this study.

The line voltages are measured by the control system in the system runtime. The measurement voltages are compared with the reference voltage. When the measurement current value is higher than the reference current value, the switching mode is changed by the control system. A flowchart of the proposed control algorithm is given in Figure 2.

The *q* loop of the machine side converter has two switching modes. The first mode is active during normal operation. The first mode input is the active power during normal operation. An error signal is produced by comparing the measured active power (*P\* g*) with the reference active power (*Pg*). To obtain the reference current (*i* ∗ *sq*), this error signal is increased by the PI control.

The second mode is active during a grid fault. The input of the second mode is the DC link voltage. An error signal is produced by comparing the reference DC link voltage (*Vdc*) with the measured DC link voltage (*V*∗ *dc*). To obtain the reference current (*i* ∗ *sq*), this error signal is increased by the PI control during a grid fault.

**Figure 2.** Flowchart of the proposed control algorithm.

Δ*i* ∗ *sq* is produced by comparing the reference current (*i* ∗ *sq*) with the measured current (*isq*). Δ*i* ∗ *sq* is the input of the IT-2 FLC system for both the fault and normal operations. In this study, the IT-2 FLC was designed specifically to obtain efficient results in both the fault and normal operations. To obtain the required voltage (*v\* sq*) for switching signals, the IT-2 FLC output signal (*x1*) sum with both ω*eLdisd* and ω*e*ψ*f*.

In addition, the *d*-axis current reference (*i* ∗ *sd*) of the MSC is set to 0. Δ*i* ∗ *sd* is produced by comparing the reference current (*i* ∗ *sd*) with the measured current (*isd*). Δ*i* ∗ *sd* is the input of the IT-2 FLC system for both the normal and fault operations. To obtain the required voltage (*v\* sd*) for switching signals, the IT-2 FLC output signal (*x2*) is added to ω*eLqisq*.

In Figure 1, the reference voltages (*v\* sd* and *v\* sq*) are added to enhance the transient response, as expressed by

$$
\begin{pmatrix} \upsilon\_{sd}^\* \\ \upsilon\_{sq}^\* \end{pmatrix} = \begin{pmatrix} V\_{sd}' \\ V\_{sq}' \end{pmatrix} + \omega\_\varepsilon \begin{pmatrix} -L\_q i\_{sq} \\ L\_d i\_{sd} \end{pmatrix} + \omega\_\varepsilon \begin{pmatrix} 0 \\ \psi\_f \end{pmatrix} \tag{6}
$$

The *q* loop of the grid side converter has two switching modes. The first mode is active during normal operation. The first mode input is the reactive power during normal operation. The reactive power (*Q\** ) is set to 0. To obtain the reference current (*i* ∗ *q*), this error signal is increased by the PI control. The input of the second mode is the fault reactive power (*Q\* FRT*). To obtain the reference current (*i* ∗ *q*), this error signal is increased by the PI control during a grid fault.

Δ*i* ∗ *q* is obtained by comparing the reference current (*i* ∗ *<sup>q</sup>*) with the current measured (*iq*). Δ*i* ∗ *q* is the input of the IT-2 FLC system for both the fault and normal operations. In this study, the IT-2 FLC was designed specifically to obtain efficient results in both fault operation and normal operation. To obtain the required voltage (*v\* <sup>q</sup>*) for switching signals, the IT-2 FLC output signal (*x3*) is added to ω*eLdid*.

The second mode is active during the grid fault. The input of the second mode is the active power. To obtain the reference current (*i* ∗ *<sup>d</sup>*), this error signal is increased by the PI control.

Δ*i* ∗ *<sup>d</sup>* is produced by comparing the reference current (*i* ∗ *<sup>d</sup>*) with the measured current (*id*). Δ*i* ∗ *<sup>d</sup>* is the input of the IT-2 FLC system for both fault and normal operations. In this study, the IT-2 FLC was designed specifically to obtain efficient results in both the normal and fault operations. To obtain the required voltage (*v\* <sup>d</sup>*) for the switching signals, the IT-2 FLC output signal (*x4*) is combined with both the ω*eLqiq* and *E*.

In Figure 1, the reference voltages (*v\* <sup>d</sup>* and *v\* <sup>q</sup>*) are added to enhance the transient response, expressed as

$$
\begin{pmatrix} \upsilon\_d^\* \\ \upsilon\_q^\* \end{pmatrix} = \begin{pmatrix} \boldsymbol{V}\_d^\prime \\ \boldsymbol{V}\_q^\prime \end{pmatrix} + \boldsymbol{\omega}\_d \begin{pmatrix} -\boldsymbol{L}\_d \dot{\boldsymbol{u}}\_q \\ \boldsymbol{L}\_d \dot{\boldsymbol{u}}\_d \end{pmatrix} + \begin{pmatrix} \boldsymbol{E}\_s \\ \boldsymbol{0} \end{pmatrix} \tag{7}
$$
