DFIG Wind Farm Research Articles

A new fragled series resonance-bridge fault current limiter with fuzzy logic controller to enhance fault ride through capabilities in DFIG-wind farms

A new fragled series resonance-bridge fault current limiter with fuzzy logic controller to enhance fault ride through capabilities in DFIG-wind farms

Wind-DFIG wireless controlled using EGPRS standard applied to the ancillary services in a smart grid environment

This paper presents an alternative topology analysis for reactive power control in wind farms with wireless communication link integration. The co-simulation environment with telecommunication, machine control, and power system demonstrate in this analysis, that it can be an useful solution for planning the operation of modern power systems and their ancillary services in a smart grid scenario. A low cost and easy implementation EGPRS standard wireless link was adopted to perform the communication from the smart grid operator and the wind farm with the objective of maintain the voltage levels under established limits. The wireless communication was used to send the value of measured voltage of one critical bar to the operator and to return the reactive power reference to the wind farm. The studied scenario is represented by a seven bar power system model connected to a DFIG wind farm. The results obtained by this co-simulation endorse this original proposal and show its operability.

Optimized strategy for DFIG wind farm considering turbine fatigue

In wind farms, the fatigue of a wind turbine reduces its life cycle. Additionally, when turbines are subjected to non-uniform fatigue loads, they tend to fail at certain high fatigue loads, which weakens the reliability of the wind farm and increases operating running costs. To operate the wind farm economically, the concept of equivalent fatigue of wind turbines is proposed, based on which an optimal strategy of active and reactive power dispatching of the wind farm is established. This considers the active power output of the wind farm and the fatigue of the wind turbines simultaneously. The swarm intelligence algorithm is used to solve the global optimal problem. Focusing on the profits of the wind farm, the reference values of optimal active and reactive output power of each turbine are calculated. Simulation results under the condition of free output and limited output verify that the proposed strategy can reduce the fatigues of wind turbines and decrease the losses of the wind farm. Thus, the life span of each wind turbine is extended, and the wind farm profits are increased.

Stability Assessment on Doubly Fed Induction Generator (DFIG) Wind Turbine Micro Grid Power System

As of late, expanding interest of renewable energy and consumption of non-renewable energy source have prompted developing advancement of renewable energy technology, for example, wind energy. Wind energy has turned out to be one of the reliable sources of renewable energy, which requests extra transmission capacity and better methods for sustaining system reliability. As of now, doubly fed induction generator wind turbine is the most well-known wind turbine. This paper focuses on DFIG wind farm design using MATLAB/SIMULINK and also investigates the issues of the system stability of the DFIG wind turbine micro grid power system. This analysis includes the changes of voltage, current, real power and reactive power based on various conditions of the power system.

Frequency drift of sub-synchronous oscillations caused by the DFIG wind farms when the wind speed varies

This paper examines the frequency drift of sub-synchronous oscillations (SSOs) caused by the DFIG wind farms when the wind speed varies. The examination is carried out by applying the analysis about the open-loop modal coupling, a newly appeared concept to investigate power system oscillations. Analysis is presented in the paper to reveal that when the wind speed varies, the open-loop electromechanical oscillation mode of the DFIG moves on the complex plane. When it moves close to an open-loop SSO mode of the rest of power system, the open-loop modal coupling occurs to lead to the damping degradation of the SSOs caused by the DFIG. Thus, the variation of wind speed may possibly cause the open-loop modal coupling between the DFIG’s electromechanical oscillation mode and different open-loop SSO modes of the power system. Consequently, poorly or even negatively damped SSOs happen at different SSO frequency. Therefore, the paper provides a better understanding on and deeper insight into the mechanism about how the change of wind speed causes the frequency drift of the SSOs from the standpoint of the open-loop modal coupling.

Adaptive fractional integral terminal sliding mode power control of UPFC in DFIG wind farm penetrated multimachine power system

With an aim to improve the transient stability of a DFIG wind farm penetrated multimachine power system (MPN), an adaptive fractional integral terminal sliding mode power control (AFITSMPC) strategy has been proposed for the unified power flow controller (UPFC), which is compensating the MPN. The proposed AFITSMPC controls the dq- axis series injected voltage, which controls the admittance model (AM) of the UPFC. As a result the power output of the DFIG stabilizes which helps in maintaining the equilibrium between the electrical and mechanical power of the nearby generators. Subsequently the rotor angular deviation of the respective generators gets recovered, which significantly stabilizes the MPN. The proposed AFITSMPC for the admittance model of the UPFC has been validated in a DFIG wind farm penetrated 2 area 4 machine power system in the MATLAB environment. The robustness and efficacy of the proposed control strategy of the UPFC, in contrast to the conventional PI control is vindicated under a number of intrinsic operating conditions, and the results analyzed are satisfactory.

Modelling and control of a VSC medium‐voltage DC distribution network with DFIG wind farm

Modelling and control of a VSC medium‐voltage DC distribution network with DFIG wind farm

SSR Damping Controller Design and Optimal Placement in Rotor-Side and Grid-Side Converters of Series-Compensated DFIG-Based Wind Farm

This paper deals with subsynchronous resonance (SSR) phenomena in a capacitive series-compensated DFIG-based wind farm. Using both modal analysis and time-domain simulation, it is shown that the DFIG wind farm is potentially unstable due to the SSR mode. In order to damp the SSR, the rotor-side converter (RSC) and grid-side converter (GSC) controllers of the DFIG are utilized. The objective is to design a simple proportional SSR damping controller (SSRDC) by properly choosing an optimum input control signal (ICS) to the SSRDC block, so that the SSR mode becomes stable without decreasing or destabilizing the other system modes. Moreover, an optimum point within the RSC and GSC controllers to insert the SSRDC is identified. Three different signals are tested as potential ICSs including rotor speed, line real power, and voltage across the series capacitor, and an optimum ICS is identified using residue-based analysis and root-locus method. Moreover, two methods are discussed in order to estimate the optimum ICS, without measuring it directly. The studied power system is a $\mathbf{100\;{\rm MW}}$ DFIG-based wind farm connected to a series-compensated line whose parameters are taken from the IEEE first benchmark model (FBM) for computer simulation of the SSR. MATLAB/Simulink is used as a tool for modeling and designing the SSRDC, and power system computer aided design/electromagnetic transients including dc (PSCAD/EMTDC) is used to perform time-domain simulation for design process validation.

Control of Grid Voltage and Power of Doubly Fed Induction Generator wind turbines during grid faults

This paper presents the design of a voltage control strategy for DFIG wind turbines, which enhances the fault ride-through capability of DFIG wind turbines and their contribution to support the grid, i.e. to the voltage control in the power system, during grid faults. The performance of the presented DFIG protection and voltage control strategy during grid faults is assessed and discussed by means of simulations of a large DFIG wind farm connected to a power transmission system generic model. The simulation results show how a DFIG wind farm equipped with the presented voltage control can help a nearby active stall wind farm to ride-through a grid fault. Index Terms: Doubly Fed Wind Turbine, Power System Control, Grid Faults, Voltage control, Pitch Angle.

Research on Intelligent Reactive Power Optimization Method for Distribution Network with DFIG Wind Farm

In order to ensure the voltage stability of distribution network with doubly fed induction generator, it is more significant to determine the reactive power distribution of the grid reasonably except installation of on load tap changing transformer and shunt capacitor bank. However, the reactive power control capability of doubly fed induction generator is not fully implemented in the reactive power optimization of distribution network. In this paper, on the premise of utilizing wind energy maximally, the wind farm with doubly fed induction generator is considered as a continuous reactive power source to participate in the reactive power optimization. Then the constructed reactive power optimization problem is converted to a nonlinear mixed integer optimization problem which is solved by intelligent genetic algorithm. Finally, the IEEE 16 node system is chosen as an example for simulation, the computation results verify the effectiveness of the proposed algorithm.

Capability curve based enhanced reactive power control strategy for stability enhancement and network voltage management

Reactive power has become a vital resource in modern electricity networks due to increased penetration of distributed generation. This paper examines the extended reactive power capability of DFIGs to improve network stability and capability to manage network voltage profile during transient faults and dynamic operating conditions. A coordinated reactive power controller is designed by considering the reactive power capabilities of the rotor-side converter (RSC) and the grid-side converter (GSC) of the DFIG in order to maximise the reactive power support from DFIGs. The study has illustrated that, a significant reactive power contribution can be obtained from partially loaded DFIG wind farms for stability enhancement by using the proposed capability curve based reactive power controller; hence DFIG wind farms can function as vital dynamic reactive power resources for power utilities without commissioning additional dynamic reactive power devices. Several network adaptive droop control schemes are also proposed for network voltage management and their performance has been investigated during variable wind conditions. Furthermore, the influence of reactive power capability on network adaptive droop control strategies has been investigated and it has also been shown that enhanced reactive power capability of DFIGs can substantially improve the voltage control performance.

Modified Dynamic Phasor Estimation Algorithm for the Transient Signals of Distributed Generators

In this paper, a modified dynamic phasor estimation method for protection relays is proposed to calculate the dynamic phasor of a fundamental frequency component with time-variant amplitude. The fault current is assumed to be the combination of a decaying dc offset, a decaying fundamental frequency component and harmonics with constant amplitude. The exponential functions of the decaying dc offset and fundament frequency component are replaced by Taylor series. Then, the LS (Least Square) technique is used to estimate the magnitudes and the time constants of decaying components. The performance of the algorithm is evaluated by using computer-simulated signals based on simple equations and fault current signals collected from DFIG wind farm model in MATLAB Simulink. The test results indicate that the proposed algorithm can accurately estimate the decaying amplitude and the time constant of the fundamental frequency component.

Ride-through and direct model reference adaptive internal model controller with rule-based adjustment mechanism for DFIG wind farms

This paper presents a direct model reference adaptive internal model controller (DMRAIMC) for a doubly fed induction generator used in wind farms for voltage sag ride-through. The dynamic response of the machine under fault causes voltage sag which affects the behaviour of the machine. This phenomenon is simulated using MATLAB/SIMULINK and presented. Here, the DMRAIMC is developed and it is tuned using fuzzy rules, and fuzzy rules adjustment mechanism is used in this controller to exchange the reactive power during voltage sag. The d- and q-axis rotor currents are controlled directly with DMRAIMC to improve the reactive power exchange of the system. The performance is compared with the conventional DMRAIMC with MIT rule adjustment mechanism. The flexibility of the proposed method in shunt connection with grid is illustrated.

Power Control Based on Pub/Sub for DFIG Wind Farm

Power control in large wind farm has a big impact on the Grid, especially in low connectivity ratio. Publish subscribe technology is asynchronous loosely coupled, and multi-to-multipoint communication as adapted for large distributed real-time control of network communications needs in the wind farm. This paper presents publish subscribe-based real-time power command-delivery method. It is well used to deliver the control of wind farm, reducing the time-delay in control loops. Simulation results show that the method further improves the quality of the power control of common coupling in large wind farms.