## 2 Characterization and Modeling of the Fault Ride-Through Process in Doubly Fed Wind Turbines
### Structured Model of Electromechanical Transient of Doubly Fed Wind Turbine
#### 2.2.2 Normal Operation Active and Reactive Power Control Module  
1. Normal active and reactive power outer loop control module;  
The control block diagram of the normal operation active and reactive power control module of the structured model of the new energy unit proposed in this paper is shown in Figure 6, in which the outer-loop active power control strategy includes outer-loop control of wind turbine speed, constant power factor control, and constant DC voltage control. The outer-loop normal operation control utilizes the output variables of the mechanical side control to generate reference values for active and reactive power, thereby controlling the inner loop and achieving complete double closed-loop control. Additionally, part of the outer loop control can also directly generate the initial active and reactive current reference values in some instances, further improving the response speed of the controller. In Figure 6a, \(T_{pe}\) is the rotational speed time constant; \(K_{\text{rreq}}\) is the proportional coefficient of the rotational speed control link; \(K_{\text{rreq}}\) is the integral coefficient of the rotational speed control link; \(T_{pe}\) is the power time constant; (d\(P\)/d\(t\))max is the maximum rate of change of the power; (dP/dt)min is the minimum rate of change of the power; T1 is the time constant of DC voltage measurement; \(K_{\text{Pudc}}\) is the proportional coefficient of the DC voltage control link; \(K_{\text{iudc}}\) is the DC voltage control link proportionality coefficient; In Figure 6b, \(Z_{c}\) is the voltage compensation impedance; \(T_{r}\) is the time constant of grid-connected voltage measurement; \(K_{pu}\) is the proportionality coefficient of constant voltage control; \(K_{lu}\) is the integral coefficient of constant voltage control; \(T_{lu}\) is the time constant of reactive power measurement; \(Q_{\text{max}}\) is the maximal value of reactive power; \(Q_{\text{min}}\) is the minimal value of reactive power; \(T_{PE}\) is the time constant of active measurement; \(PF_{\text{ref}}\) is the constant power factor angle. 2. Inner loop current control module;  
The converter inner-loop current control module adopts multi-strategy independent control architecture for active and reactive power. The inverter inner-loop active current control mode includes active power direct voltage removal and active power PI control; the inverter inner-loop reactive current control mode includes reactive power direct voltage removal, reactive power PI control, and reactive power and voltage coordinated control. As  
Figure 6: Normal operation of the active and reactive power control module: (**a**) Normal active control module; (**b**) Normal reactive power control module. shown in Figure 7, in the inner-loop current control structure, the system collects the output \(P_{\text{gen}}\) and \(Q_{\text{gen}}\) in real-time and carries out the PI closed-loop control operation with the reference values of \(P_{\text{ref}}\) and \(Q_{\text{ref}}\) from the output of the outer-loop control and ultimately generates the initial active current reference value \(I^{\prime}{}_{\text{{\it{def}}}}\) and the reactive current reference value \(I^{\prime}{}_{\text{{\it{qref}}}}\). The control modes can be switched seamlessly according to the grid operation demand. Each control mode can be switched according to the grid operation requirements, where the PI control adopts an anti-saturation integral algorithm to ensure current limiting protection during the dynamic response process.