Rotor Side Converter Of Doubly Fed Induction Generator Research Articles

Experimental Investigation of DFIG-based Wind Energy Conversion System Using Fuzzy Logic Control

In this paper, an experimental study of a Wind Energy Conversion System (WECS) is performed. A test bench with a power of 1.5 kW is setup. The system consists of a Doubly-Fed Induction Generator (DFIG) and a wind emulator based on a DC motor associated with a Maximum Power Point Tracking (MPPT) control. The proposed emulator is driven by a four quadrants DC/DC converter to produce a real wind turbine behavior. The aim of this work is to improve the DIFG performances by using the fuzzy logic-based intelligent controller. This control technic is designed to monitor the stator reactive and active powers. This can be achieved by the DFIG rotor side converter (RSC) using the field-oriented control. The experimental setup uses a dSPACE DS1104 device, MATLAB/Simulink software and a ControlDesk interface. The paper shows that, the desired amount of active and reactive powers has been independently controlled and the implementation is successfully verified the effectiveness of the proposed control scheme achieved using the FLC strategy.

Approach Control of DFIG Rotor Side Converter Based on Grid Frequency Coordinated Control

Abstract. This paper presents an approach frequency coordinated control of Doubly Fed Induction Generator (DFIG) applying in the Rotor Side Converter (RSC) using an order reference active power (Pref ). Pref is obtained from the frequency deviation, speed regulation and kinetic energy stored in the DIFG. The Pref is employed as a main controller parameter of the dq-axis currents in the RSC under two case studies. In case1 study, the Pref is used to regulate the q-axis reference current and the grid reactive power controlled d- axis reference current. Whilst in case2 study, the d- axis reference current is produced by Pref , and the rotormechanical speed responsible to generate the q-axis reference current. The modified vector control method is used to control the Grid Side Converter (GSC) in two case studies. The transient performance of two case studies is simulated by PSCAD/EMDTC program under constant, step and variable wind speeds. A comparative result between two case studies shown that the frequency coordinated control has an ability to control both rotor dq-axis currents, and it enhancing the system frequency as well as improved DFIG voltage stability.However, case2 study has a better response than case1 study during system operated under random wind speed.

Adaptive hybrid intelligent MPPT controller to approximate effectual wind speed and optimal rotor speed of variable speed wind turbine

Operating wind power generation system at optimal power point is essential which is achieved by employing a Maximum Power Point Tracking (MPPT) control strategy. This literature focuses on developing a novel particle swarm optimization algorithm enhanced radial basis function neural network supported TSR based MPPT control strategy for Doubly Fed Induction Generator (DFIG) based wind power generation system. The proposed hybrid MPPT control strategy estimates the effective wind speed and estimates the optimal rotor speed of the wind power generation system to track the maximum power. The proposed controller extremely reduces the speed dissimilarity range of wind power generation system, which leads to rationalizing the pulse width inflection of DFIG rotor side converter. This in turn, increases the system’s reliability and delivers an effective power tracking with reduced converter losses. Furthermore, by utilizing the proposed MPPT controller, the converter size can be reduced to 40%. Therefore, the overall cost of the system can be gradually decreased. To validate the performance of the proposed MPPT controller, an extensive simulation study has been carried out under medium and high wind speed conditions in MATLAB/Simulink. The obtained results have been justified using experimental analysis.

Reactive power control of DFIG wind turbines for power oscillation damping under a wide range of operating conditions

This study analyses the effect of replacing existing synchronous generators (SGs) equipped with power system stabilisers (PSS) by doubly fed induction generator (DFIG) based wind farms on the damping of power system oscillations in a multi-machine power system. A power system stabiliser was designed to enhance the capability of DFIG to damp power systems oscillations. The validity and effectiveness of the proposed controller are demonstrated on the widely used New England 10-machine 39-bus test system that combines conventional SGs and DFIG based wind farms using eigenvalue analysis and non-linear simulation. The non-linear simulation is used to demonstrate how the damping contribution of DFIG based wind farms is affected by different operating conditions within the same wind farm and stochastic wind speed behaviour. The results show that installing conventional fixed parameters PSS within reactive power control loop of DFIG rotor side converter has a positive damping contribution for a wide range of operating conditions. Furthermore, the results clearly show that DFIG based wind farms equipped with the proposed farm level PSS can damp power system oscillations more effectively than SGs PSS.

Direct Torque Control of Saturated Doubly-Fed Induction Generator using High Order Sliding Mode Controllers

The present work examines a direct torque control strategy using a high order sliding mode controllers of a doubly-fed induction generator (DFIG) incorporated in a wind energy conversion system and working in saturated state. This research is carried out to reach two main objectives. Firstly, in order to introduce some accuracy for the calculation of DFIG performances, an accurate model considering magnetic saturation effect is developed. The second objective is to achieve a robust control of DFIG based wind turbine. For this purpose, a Direct Torque Control (DTC) combined with a High Order Sliding Mode Control (HOSMC) is applied to the DFIG rotor side converter. Conventionally, the direct torque control having hysteresis comparators possesses major flux and torque ripples at steady-state and moreover the switching frequency varies on a large range. The new DTC method gives a perfect decoupling between the flux and the torque. It also reduces ripples in these grandeurs. Finally, simulated results show, accurate dynamic performances, faster transient responses and more robust control are achieved.

Coordinated Control of DFIG's RSC and GSC Under Generalized Unbalanced and Distorted Grid Voltage Conditions

This paper proposes a coordinated control of the rotor-side converter (RSC) and grid-side converter (GSC) of a doubly fed induction generator (DFIG)-based wind-turbine generation system under generalized unbalanced and/or distorted grid voltage conditions. The system behaviors of the RSC and GSC during supply imbalance and distortion are investigated. To enhance the fault ride-through operation capability, the RSC is properly controlled to eliminate the torque oscillations, whereas the GSC is carefully designed to ensure constant active power output from the overall DFIG generation system. To achieve simultaneous regulation of the positive-/negative-sequence currents and fifth-/seventh-order harmonic currents for both the RSC and GSC, a novel current controller, consisting of a conventional proportional-integral regulator and a dual-frequency resonant compensator, is proposed and implemented in the positive (dq)+ reference frame. The simulation and experiment studies demonstrate the correctness of the developed model and the effectiveness of the suggested control strategy for DFIG-based wind-turbine systems under such adverse grid conditions.

A Novel Vector-Based Hysteresis Current Regulator for Doubly-Fed Induction Generator Wind Turbines Under Non-Ideal Supply Conditions

This paper proposes a novel vector-based hysteresis current regulator (VBHCR) in the rotor-side converter of doubly-fed induction generator (DFIG) based wind turbine to enhance its operation under non-ideal supply voltage conditions. First, the induction generator is modelled using the “Γ-form” equivalent circuit and the stator-voltage-oriented vector control of DFIG is introduced. Then, the principle and practical implementation of the proposed VBHCR in the rotor-side converter of DFIG is presented. This current regulator employs two sets of hysteresis comparators working in three-phase and rotor reference frames, integrated with a switching table. Compared to the commonly-used proportional-integral current regulators, it reveals very fast transient response with a simple control structure. Simulation results, obtained for a 1.5 MW DFIG, show the validity of the proposed control scheme under normal operation conditions, as well as its desirable steady-state performance. Furthermore, the advantages of the proposed current regulator under non-ideal supply voltage conditions (including unbalance and harmonic distortions) are illustrated.

Enhanced Fault Ride-through Scheme for Mitigating Rotor Speed Instability of Doubly Fed Induction Generator Based Wind Farms

This paper analyzes and proposes a novel scheme with suitable control strategy to increase the probability of successful fault ride-through (FRT) as well as to enhance the rotor speed stability of doubly fed induction generator (DFIG) based wind farms. The proposed FRT scheme consists of an uncontrolled rectifier, two sets of IGBT switches, a diode and an inductor connected between the rotor circuit and dc link capacitor, in parallel with the rotor side converter of DFIG. In the proposed scheme, during a fault event, the input mechanical energy of the wind turbine is stored as electromagnetic energy in the inductor. Consequently, torque balance between the electrical and mechanical quantities is maintained and the rotor speed deviation is thereby reduced. This results in reduced reactive power requirement and rapid reestablishment of terminal voltage on fault clearance. Moreover, the stored electromagnetic energy in the inductor is transferred into the dc link capacitor on fault clearance; thereby relieving the grid side converter from charging the dc link capacitor. The proposed FRT scheme is validated through an extensive time domain simulation study employing PSCAD/EMTDC software. Simulation results demonstrate the effectiveness of the proposed FRT scheme in achieving successful fault ride-through and rotor speed stability of DFIG based wind farms.