Abstract
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.
Highlights
In the last few decades, Energy problems are increased rapidly due to fast depletion of the fossil fuel and its highly cost, renewable energy plays an alternative way in order to overcome the expected power crisis
Many researches introduce different crowbar protection techniques such as series crowbar resistors connected with stator windings, parallel crowbar resistors connected with rotor windings, and outer crowbar resistors connected between the doubly fed induction generator (DFIG) terminals and electrical grid [10,11,12,13,14,15,16,17,18]
The operation of DFIG wind turbines in case of using the proposed adaptive neuro-fuzzy inference system (ANFIS) crowbar based on fault type (CBFT) protection technique is more stable, where it can return to steady state conditions in a short time after fault clearance comparing with the traditional parallel rotor crowbar and classical outer crowbar protection techniques
Summary
In the last few decades, Energy problems are increased rapidly due to fast depletion of the fossil fuel and its highly cost, renewable energy plays an alternative way in order to overcome the expected power crisis. The crowbar protection technique is necessary to avoid a disconnecting of DFIG wind turbines during grid faults. This paper proposes a novel controllable CBFT protection technique driven by ANFIS for studied DFIG wind turbines. The proposed protection technique is structured as a combination of three crowbar resistors that connected to wind turbine generator terminals. The behaviours of studied DFIG wind turbines equipped with classical outer crowbar and proposed ANFIS CBFT protection techniques during different fault types are investigated. The output value for each rule is calculated by using the value of normalized firing strength from previous layer and polynomial of Takagi-Sugeno model The output of this layer is given as follows: O4;i 1⁄4 wi  zi ð19Þ where o4,i is the output of node i for layer 4. Ðwi  ziÞ 1⁄4 i X ð20Þ i wi i where o5,i is the output of node i for layer 5
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