This paper proposes a novel controllable crowbar based on fault type (CBFT) protection technique for doubly fed induction generator (DFIG) wind energy conversion system connected to grid. The studied system consists of six DFIG wind turbines with a capacity of 1.5 MW for each of them. The operation mechanism of proposed technique is used to connect a set of crowbar resistors in different connection ways via activation of controllable circuit breakers (CBs) depending on the detected fault type. For each phase of DFIG, a crowbar resistor is connected in parallel with a controllable CB and all of them are connected in series to grid terminals. The adaptive neuro-fuzzy inference system (ANFIS) networks are designed to detect the fault occurrence, classify the fault type, activate the CBs for crowbar resistors associated with faulted phases during fault period, and deactivate them after fault clearance. The effectiveness of proposed CBFT protection technique is investigated for different fault types such as symmetrical and unsymmetrical faults taking into account the single-phase to ground fault is the most frequently fault type that occurs in power systems. Also, a comparison between the behaviours of studied system in cases of using traditional parallel rotor crowbar, classical outer crowbar, and proposed CBFT protection techniques is studied. The fluctuations of DC-link voltage, active power, and reactive power for studied system equipped with different protection techniques are investigated. Moreover, the impacts of different crowbar resistance values on the accuracy of proposed technique are studied. The simulation results show that, the proposed technique enhances the stability of studied wind turbine generators and contributes in protection of their components during faults.

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This paper proposes the employment of Static Synchronous Compensator (STATCOM) in reactive power compensation to enhance the Fault Ride-Through (FRT) capability and improve the dynamic performance of a grid-connected PV/wind hybrid power system during the transient grid disturbances. The hybrid power system consisting of 9 MW Doubly Fed Induction Generator (DFIG)-based wind farm and 1 MW PV station is integrated with 100 MVAR STATCOM at the Point of Common Coupling (PCC) bus. The dynamic performance of the PV/wind hybrid power system with the proposed STAT-COM controller is analyzed and compared with another FRT control strategy during a grid voltage sag. The FRT control strategy is based on the injection of reactive power from the hybrid system to enhance the FRT capability during the grid faults, and also activation of the outer crowbar protection system to protect the DFIG. On the other hand, the proposed STATCOM controller adjusts the PCC bus voltage during the grid disturbances by dynamically controlling the amount of reactive power injected to or absorbed from the electrical grid. Modeling and simulation of the proposed hybrid power system have been implemented using MATLAB/SIMULINK software. The effectiveness of both the proposed STATCOM controller and the FRT control strategy is evaluated during a 50% grid voltage sag. The simulation results illustrate that the STATCOM controller decreases significantly the level of voltage drop during the voltage sag, maintains the injected active power from the PV station at its rated value, and protects effectively the PV DC-link voltage from overvoltage. Moreover, when the STATCOM controller is employed, the injected active power from the wind farm is improved considerably and the oscillations of the DFIG rotor speed are reduced efficiently during the fault. Furthermore, the comparison confirms the superior dynamic performance of the STATCOM controller in enhancement the FRT capability as compared with the FRT control strategy.

This paper presents a design of robust intelligent protection technique using adaptive neuro-fuzzy inference system (ANFIS) approach to detect and classify the fault types during various faults occurrence in large-scale grid-connected wind farm. Also, it is designed to determine the fault location and isolate the wind turbine generators located in the faulted zone during fault occurrence and reconnect them after fault clearance. The studied wind farm has a total rating capacity of 120 MW, where it consists of 60 doubly fed induction generator (DFIG) wind turbines each has a capacity of 2 MW. Moreover, the wind farm generators are positioned in 6 rows, where each row consists of 10 generators. The impacts of fault type, fault location, fault duration, cascaded faults, permanent fault and external grid fault on the behaviours of the generated active and reactive power are investigated. Also, the impacts of internal and external faults in cases of different transition resistances are investigated. The simulation results indicate that, the proposed ANFIS protection technique has the ability to detect, classify and determine the fault location, then isolate the faulted zones during fault occurrence and reconnect them after fault clearance. Furthermore, the wind turbines generators which are located in un-faulted zones can stay to deliver their generated active power to the grid during fault period.

The potential for utilizing clean energy technologies in Egypt is excellent given the abundant solar irradiation and wind resources. This paper provides detailed design, control strategy, and performance evaluation of a grid-connected large-scale PV/wind hybrid power system in Gabel El-Zeit region located along the coast of the Red Sea, Egypt. The proposed hybrid power system consists of 50 MW PV station and 200 MW wind farm and interconnected with the electrical grid through the main Point of Common Coupling (PCC) busbar to enhance the system performance. The hybrid power system is controlled to operate at the unity power factor and also the Maximum Power Point Tracking (MPPT) technique is applied to extract the maximum power during the climatic conditions changes. Modeling and simulation of the hybrid power system have been performed using MATLAB/SIMULINK environment. Moreover, the paper presented a comprehensive case study about the realistic monthly variations of solar irradiance and wind speed in the study region to validate the effectiveness of the proposed MPPT techniques and the used control strategy. The simulation results illustrate that the total annual electricity generation from the hybrid power system is 1509.85 GWh/year, where 118.15 GWh/year (7.83 %) generates from the PV station and 1391.7 GWh/year (92.17%) comes from the wind farm. Furthermore, the hybrid power system successfully operates at the unity power factor since the injected reactive power is kept at zero.