Doubly-fed Wind Power Generation System Research Articles

Research on Modeling and Simulation of Doubly Fed Induction Wind Turbine Based on Matlab/Simulink

This paper first introduces the structure of doubly-fed wind power generation system and the working principle of doubly-fed induction generator in detail, and establishes the corresponding mathematical model of doubly-fed wind power generation unit. The control part of wind power generation system based on doubly-fed induction generator includes rotor side control and stator side control. The rotor side control adopts the vector control strategy based on stator flux orientation of the double-fed induction generator connected to the grid, and the working principle is analyzed in detail, and the main part of the simulation modeling is given. Stator side control adopts vector control strategy of grid-connected inverter control, and its working principle is analyzed in detail, and the main part of simulation modeling is also given. In order to verify the correctness and feasibility of the system, the simulation experiment platform of doubly fed wind turbine under this control strategy is built by using Matlab/Simulink simulation platform, and its simulation analysis is carried out in detail.

Cause analysis of doubly-fed wind turbine faults

Doubly-fed wind turbine is the mainstream model at present. This paper first introduces the working principle of a doubly-fed wind power generation system, counts the fault frequency and fault duration of a doubly-fed wind turbine, and makes an in-depth analysis of the fault data in the recent two years. Then it summarizes the fault components and fault types of doubly-fed wind turbines, and on this basis, analyzes the causes of the faults, which can be used as a reference for wind farms to formulate fault prevention schemes for doubly-fed wind turbines.

Stability Modeling and Analysis of Grid Connected Doubly Fed Wind Energy Generation Based on Small Signal Model

Stable wind power generation can ensure the quality of power transmitted by the grid. The application of large-scale grid-connected wind power systems will induce problems such as grid oscillation and frequency instability. In order to solve the problem of abnormal power system interaction caused by large-scale wind power access and improve the stability of grid-connected doubly-fed wind power generation, this paper proposes a stability modeling analysis of grid-connected doubly-fed wind power generation based on small signal model. First, the operating conditions of the grid-connected DFIG are analyzed, and the vector diagrams of the three operating conditions are given. When the grid-connected DFIG is in the super-synchronous working state, the sub-synchronous working state and the synchronous working state. According to the operating conditions of the grid-connected doubly-fed generators, the grid-connected doubly-fed wind power generation system is linearized. According to the relationship between the actual speed and the synchronous speed of the doubly-fed generator, the operating conditions of the doubly-fed generator are analyzed. By introducing the small-signal model, we analyze the small-signal of the grid-connected doubly-fed wind power generation system. The indirect current control circuit is used to perform reactive power compensation for grid-connected doubly-fed wind turbines. By calculating the reactive power loss of the grid-connected DFIG and the reactive power loss of the transmission line, the compensation capacity of the grid-connected DFIG is calculated. The transient voltage of the wind turbine is controlled by the rotor-side frequency converter, combined with the pitch angle control model. So far, this paper has realized the modeling analysis of grid-connected doubly-fed wind power generation stability. The simulation results show that the modeling analysis in this paper is reasonable for the small-signal analysis results of the stability of grid-connected doubly-fed wind power generation. In the rotor voltage simulation test, after the oscillation occurs for 1 s, the model starts to simulate and eliminate the fault. During the simulation period of 0.7 s∼1.0 s, the output voltage of the converter decreased to 168 V, and the voltage waveform did not fluctuate greatly after 1.0 s. The experimental results show that this method can improve the stability of grid-connected doubly-fed wind power generation.

A Sub-Synchronous Oscillation Suppression Strategy for Doubly Fed Wind Power Generation System

During the power transmission of doubly-fed induction generator (DFIG), due to the influence of series compensating capacitance and long-distance transmission, DFIG is prone to sub-synchronous oscillation, which damages the stability of the system. By establishing the mathematical model of DFIG system, the cause of sub-synchronous oscillation and its influence on the control strategy of DFIG system are discussed. In order to solve the problem of performance degradation of traditional phase-locked loop (PLL) under sub-synchronous oscillation, an improved PLL is proposed to replace the traditional PLL. Aiming at the problem that the control of rotor side converter(RSC) and grid side converter(GSC) in doubly-fed wind power generation system under sub-synchronous oscillation is disturbed by harmonic signals, a control method of adding a quasi resonant controller in the control link of RSC and GSC to suppress sub-synchronous oscillation is proposed, and the feasibility of the method is verified by simulation and experiment. Finally, based on the research process of RSC direct resonance control, the sub-synchronous oscillation suppression strategy based on harmonic current extraction is proposed for the frequency adaptability of the quasi resonant controller. The actual performance of the sub-synchronous oscillation suppression strategy is verified through simulation and experiment. The experimental results show that the strategy is effective.

The Role of Doubly-fed Motor with Low Voltage Ride Through by Controlling Converter in Wind Power Generation

To improve the performance of the doubly-fed wind power converter system, according to the doubly-fed wind turbine system and its mathematical model, a vector control based on doubly-fed wind power converter control strategy and the rotor side stator flux linkage attenuation in the grid voltage drop of the doubly-fed wind power system are proposed. MATLAB/Simulink software is used to simulate different voltage sags and to compare and analyze the changes of stator flux and zero-sequence current between original control and stator flux attenuation control based on rotor side. It is found that when the grid voltage drops by 20%, the impact on the system is small, and when it falls to 80%, it would cause huge damage to the converter. And compared with the original control, the low voltage crossing control based on stator flux attenuation on the rotor side can restore the stable running state of the system more quickly. The results show that the stator flux decay control based on rotor side can make the doubly-fed wind machine transit the process quickly and reach a stable state, which lays a foundation for better control of power grid and reactive power support. The results of this study are intended to provide a basis for the control strategy of the converter in the doubly-fed wind power generation system and the stable operation of the system.

A control strategy of Hamilton realization and mechanics Lagrangization in doubly-fed wind power generation system

Abstract With the nonlinear characteristic of doubly-fed wind power generation (DFWPG) system, Hamilton realization based on analytical mechanics plays a significant role in the system problems of stability analysis and controller design. Hamilton system expression of grid-side converter (GSC) and machine-side converter (MSC) is obtained and the stability control is designed with Lagrange theory of analytical mechanics in this paper. Firstly, to obtain the differential equations which satisfy satisfies self-adjoint conditions, coordinate transformations of dynamic equations of GSC and MSC are conducted. The system Hamilton function and Hamilton realization expression are determined based on Euler–Lagrange process and generalized force method. On the basis of feedback control theory the controller is designed, which can make the system tend to be asymptotically stable in the neighborhood of the equilibrium point. With Hessian matrix positive-definite the Hamilton system is determined to be stable. Additionally, within Matlab/Simulink environment, the transient simulation of DFWPG system is carried out and the effectiveness of controller derived in this paper is verified, by comparisons of response effects with PI control and regulation performances under different wind speeds. The rapid response of the dc bus voltage control, grid-side unit power factor control, a maximum capture of wind energy can be realized, using control design process of Hamilton realization. The system analysis and control design process of Hamilton realization have broad prospects of applications and developments.

Gearless Continuously Variable Transmission Technology and its Application in Wind Power Generation

Based on gearless continuously variable transmission technology, a cascaded wind power generation system with Variable Speed Constant Frequency (VSCF) is presented in this paper. The system has combined the advantages of doubly-fed and direct-drive wind power generation system. The raising-speed gear box has been done away with, and the system reliability has been improved. Reducing the power capacity of the aspects of the variable frequency speed regulation, the function of grid-connected electricity generation can be achieved with less cost. Synchronous generator directly connects to grid, which helps to optimize power quality. The topological structure of system is discussed in this paper, and its operating principle is analyzed, revealing its characteristics and engineering application prospects.

A Control Strategy for Transient Stability Improvement of Doubly-Fed Wind Power Generation System

A novel inverter control strategy to enhance the transient stability of grid-connected wind farm based on doubly-fed induction generator (DFIG) is presented. Adding transient angle control strategy in the rotor side converter active control loop, this can dissipate the system unbalancing energy and restrain the system oscillations by the variation of wind turbine speed. Adding transient voltage control strategy in reactive control loop, this can provide fast reactive power compensation and support the restoration and reconstruction of the grid voltage when fault occurred. The control strategy which can improve the transient Angle stability and transient voltage stability at the same time is put forward. Finally, a testing system including a DFIG-based wind farm is realized using DigSILENT/Power Factory, the strategy validation and the contribution to power system stability enhancement are verified by simulation.

An operating condition fuzzy assessment strategy for large scale doubly-fed wind power generation system

Timely and accurate assessment of wind turbine operating condition can save the maintenance cost effectively, because equipment repair and replacement for large wind turbine are expensive. Therefore, an efficient operating condition assessment strategy for wind turbine is proposed based on fuzzy synthesis method. First, the traditional fuzzy assessment process is introduced briefly a foundation for comparison. Second, a wind turbine assessment model is established and assessed in detail, with an improved fuzzy prediction strategy and de-fuzzy strategy. Finally, a comparison between the improved strategy and the traditional strategy is studied based on wind turbine operation data, and the results validate that the strategy proposed in this paper can alarm operation fault more promptly and efficiently, which is better for wind turbine operation safety and maintenance.

The Research for Control Strategy of Low Voltage Ride-through Based on DFIG

The doubly-fed wind power generation system containing crowbar protection circuit will change from reactive power source to reactive power load during the low voltage ride-through, which is likely to aggravate burdens to the fault system. Aiming at solving this problem, the paper will introduce the STATCOM compensation device, and put forward a comprehensive control strategy. Under the coordinated control strategy, the STATCOM will cooperate with the compensation capacity of the doubly-fed generator to support the reactive power. The voltage at point of common coupling will be raised and the ability of low voltage ride-through of the wind turbines will be improved. A simulative model of doubly-fed induction generator is established in MATLAB and the strategys rationality and effectiveness will be verified by the simulative results.

Experimental evaluation of a variable-speed, doubly-fed wind-power generation system

Experimental evaluation of a variable-speed, doubly-fed wind-power generation system