Wind Turbine Generator System Research Articles

Frequency Control of an Isolated Micro-Grid Using Double Sliding Mode Controllers and Disturbance Observer

A novel frequency control method based on double sliding mode (SM) controllers is proposed for isolated micro-grids with renewable sources. In the presented technique, the SM pitch angle controller is designed for wind turbine generator (WTG) system to smooth wind power output. The SM load frequency controller (LFC) is constructed for diesel generator system to restore system frequency to normal through the secondary frequency regulation. Then the adaptive SM LFC is redesigned by taking advantage of the disturbance observer and adaptive law to improve dynamic performance of the diesel generator system. The proposed strategy is tested in a typical isolated hybrid micro-grid with both PV and WTG.

Coordinated pitch & torque control of large-scale wind turbine based on Pareto efficiency analysis

For the existing pitch and torque control of the wind turbine generator system (WTGS), further development on coordinated control is necessary to improve effectiveness for practical applications. In this paper, the WTGS is modeled as a coupling combination of two subsystems: the generator torque control subsystem and blade pitch control subsystem. Then, the pole positions in each control subsystem are adjusted coordinately to evaluate the controller participation and used as the objective of optimization. A two-level parameters-controllers coordinated optimization scheme is proposed and applied to optimize the controller coordination based on the Pareto optimization theory. Three solutions are obtained through optimization, which includes the optimal torque solution, optimal power solution, and satisfactory solution. Detailed comparisons evaluate the performance of the three selected solutions and provide the optimized controller coordination suggestions according to different requirements.

Application of Optimized SFCL and STATCOM for theTransient Stability and LVRTCapability Enhancement of Wind Farms

In this paper, the combined superconducting fault current limiter (SFCL) and STATCOM are used to improve transient stability and low-voltage ride-through (LVRT) capability of the wind turbine generation system (WTGS). The SFCL absorbs the accelerating energy of the generator, and therefore, improves the WTGS transient stability. Also, STATCOM helps the restore connecting point voltage to improve LVRT capability by reactive power compensation (RPC) after fault clearing. The optimization problem of SFCL resistance and STATCOM capacity is formulated based on the transient stability and LVRT capability of WTGS. The Simulation study shows the superior improving LVRT capability of combined SFCL and STATCOM over individual SFCL or STATCOM. Also, the required capacity of STATCOM for RPC is significantly reduced. PSCAD/EMTDC software (V4.2) is used for simulation.

Interval type-2 fuzzy logic based MPPT algorithm for direct drive PMSG wind turbine system

This paper proposes a maximum power point tracking (MPPT) scheme for direct drive permanent magnet synchronous generator (PMSG) wind turbine system. In this scheme, the machine side converter (MSC) is controlled using the interval type-2 fuzzy logic control (IT2-FLC). The IT2-FLC is proposed owing to its ability to handle the uncertainties of the system parameters. The additional degree of freedom of type-2 fuzzy sets is due to the third dimension in the membership function which handles power oscillations damping and voltage recovery following parameter uncertainties in the network. The field oriented control is used to control the machine side and grid side converter. The design of the proposed control scheme of the MSC is presented in this paper. Simulation results, based on MATLAB-Simulink, for a 1.5 MW PMSG wind turbine are carried out to validate the proposed control scheme considering the various uncertainties. Also, experimental results with hardware in loop (HIL) configuration are obtained for reduced scale PMSG wind turbine to demonstrate the feasibility of the controller for real time applications. The results show a significant enhancement in speed regulation, mechanical stress reduction and power harvest with the proposed control scheme.

The Coordinated Control of Wind-Diesel Hybrid Micro-Grid Based on Sliding Mode Method and Load Estimation

In order to reduce the frequency deviation resulting from renewable energy fluctuation and load variance, the coordination control strategy for isolated wind-diesel hybrid micro-grid is proposed by taking advantage of smart neural network observer and sliding mode method. For diesel generator system side, the sliding mode load frequency control including load variance is designed to regulate the output power. For the wind turbine generator system side, the sliding mode pitch angle control considering load variance is constructed to smooth the wind turbine generator output power fluctuation. Furthermore, the different coordinated strategies are proposed to realize the plug and play for the hybrid micro-grid, it is easy to see that the control accuracy can be improved by the designed neural network adaptive observer and considering the load variation. The effectiveness of the proposed control strategy is validated through real time digital simulator platform under different operation condition.

Automatic Fault Diagnosis Method for Wind Turbine Generator Systems Driven by Vibration Signals

Automatic Fault Diagnosis Method for Wind Turbine Generator Systems Driven by Vibration Signals

Reduction in Power Output Fluctuations and Platform Motions in a Floating Offshore Wind Turbine-Generator System by Model Predictive Control

Reduction in Power Output Fluctuations and Platform Motions in a Floating Offshore Wind Turbine-Generator System by Model Predictive Control

Reduction in Power Output Fluctuations and Platform Motions in a Floating Offshore Wind TurbineGenerator System by Model Predictive Control

Reduction in Power Output Fluctuations and Platform Motions in a Floating Offshore Wind TurbineGenerator System by Model Predictive Control

Power Control of Large-scale Vertical Axis Wind Turbine-Generator Systems Based on Feedforward Manipulation of Rotor Speed Set-point

Power Control of Large-scale Vertical Axis Wind Turbine-Generator Systems Based on Feedforward Manipulation of Rotor Speed Set-point

A Virtual Synchronous Generator Based Hierarchical Control Scheme of Distributed Generation Systems

Sustainable energy-based generation systems, such as photovoltaic and wind turbine generation systems, normally adopt inverters to connect to the grid. These power electronic interfaces possess the characteristics of small inertia and small output impedance, which create difficulties to stabilize the voltage and frequency of a distributed power source. To deal with this problem, a Virtual Synchronous Generator (VSG)-based inverter control method is presented in this paper by introducing virtual inertia and damping coefficient into the control loop to emulate the dynamic behavior of a traditional synchronous generator. Based on this VSG control method, a three-layer hierarchical control scheme is further proposed to increase the control accuracy of the voltage and frequency in a VSG-based distributed generation system with parallel inverters. The principle of the VSG control method, the system stability analysis, the design process of the hierarchical control structure, and the frequency/voltage secondary regulation processes are all specified in this paper. Finally, some numerical simulations are carried out and the effectiveness of proposed control scheme is verified by the simulation results analysis.

Reliability and economic evaluation of a microgrid power system

The renewable energy resources (RERs) have been globally accepted for power generation due to the high prices of fossil fuels, environmentally friendly, low operation and maintenance (O&M) costs, no carbon emission and escalation in power demand due to rapid growth in population and industrialization. A microgrid (MG) power system that consists of the diesel generator, wind turbine generator (WTG), photovoltaic (PV) and electric storage system (ESS) is utilized in this study with the aim of improving the reliability and minimizing the cost of energy (COE) and annualized cost of the system (ACS). This objective is achieved by using the expected energy not served (EENS), loss of load expectation (LOLE), cost of load loss, loss of load probability (LOLP), net present cost (NPC), annualised fuel cost (AFC), annualised emission cost (AEC), annualised maintenance cost (AMC), annualised capital cost (ACC) and annualized replacement cost (ARC) of the system. These operating parameters are used in this work to investigate the effects of RERs in a power system. To achieve the main objective of this paper, the basic probability concept is utilized to find the reliability indices of the proposed power system as well as the development of a software in the MATLAB programming environment by using fmincon optimization tool to investigate the economic impact of RERs in a micro grid power system. The results obtained from the research work show that RERs can be used to improve the reliability and reduce the COE and ACS of a power system.

Impact of Crowbar Resistances on Low Voltage Ride Through of Doubly Fed Induction Wind Turbine Generation System

The impact of crowbar resistance on low voltage ride through (LVRT) of doubly-Fed induction generator (DFIG) is researched. The relationship between the crowbar resistance and the rotor transient current and the attenuation rate of stator rotor transient flux is derived. It is proposed to add series dynamic capacitor in crowbar circuit to decrease the absorbed reactive power. Results show that, either too large or too small crowbar resistance may weaken the ability of DFIG LVRT, the optimal crowbar resistance should be selected and the additional dynamic capacitor makes the rotor overcurrent has a smaller transient time constant and a faster recovery speed for the grid fault.

A dynamic coordinated control strategy of WTG-ES combined system for short-term frequency support

Abstract In this article, a dynamic coordinated control strategy is proposed for wind turbine generator (WTG) and energy storage (ES) combined system, which enables the combined system to participate in the short-term frequency regulation of the utility gird. The theoretical analysis of the equivalent inertia of the combined system is performed and the mechanism of the short-term frequency regulation is revealed. The coordinated control strategy is designed considering the variability of wind power and the state of charge (SoC) of ES, which ensures a good performance of the frequency support under the wind variation and the SoC changing. Case study is used to validate the proposed strategy, which indicates that, this strategy can adaptively adjust the power distribution between the WTGs and the ES units during the frequency support, keep the output power stable when the wind speed changes, and diminish the decrease of SoC of the ES units.

A compositive control method of low‐voltage ride through for PMSG‐based wind turbine generator system

Converting the surplus power into rotor kinetic energy by changing the control functions of machine side converter (MSC) and grid side converter (GSC) is considered to be an efficient way for permanent magnet synchronous generator (PMSG)-based wind turbine generator system (WTGS) to accomplish low-voltage ride through (LVRT) without additional hardware components. However, because of the time delay of grid fault detection and the control system inertia, the dc-link capacitor may still be subjected to overvoltage in the early tens of milliseconds after a grid fault happens. This study proposes a compositive control method of LVRT for PMSG-based WTGS, in which the surplus power during LVRT is converted into rotor kinetic energy by controlling the electrical power of the PMSG according to the grid-connected power of the GSC, and a crowbar circuit is reserved to consume the surplus power before MSC reacts to the grid fault. The proposed method does not change the control functions of MSC and GSC, and the related control parameters resetting can be avoid. Besides, it can also provide reactive power support to assist the grid voltage recovery. Simulations and experiments proved the proposed method to be feasible and effective.

Wind Turbine Structural Modeling Consideration for Dynamic Studies of DFIG Based System

This paper presents the dynamic analysis of a grid connected Doubly Fed Induction Generator based wind turbine generator system with the detailed mechanical structural modelling of the wind turbine. The Euler–Lagrangian approach has been used for the structural dynamics of the wind turbine. The driving input mechanical power to the wind turbine has been modelled by the Blade Element Momentum (BEM) method and same has been used to calculate the tangential force on the blades responsible for the edgewise vibration of it. A polynomial regression model and feed-forward back-propagation neural network have been used to replace the BEM algorithm for modal analysis and time-domain simulation, respectively. The different modes of the entire system at different operating points and system parameters have been found and the grid-structure interaction is analyzed. The results offer a deep understanding of the combined electromechanical, aerodynamic, and mechanical structural dynamics of the system and may further be used to design various control schemes. The structural and aerodynamic data from the NREL 5-MW three-bladed Horizontal Axis Wind Turbine were used for the simulation. The model has been validated by NREL's simulation tool, FAST v7.

Power Smoothing Control of PMSG Based Wind Generation Using Supercapacitor Energy Storage System

AbstractThis paper proposes an efficient power smoothing control strategy for variable speed grid connected permanent magnet synchronous generator (PMSG) based wind turbine generator (WTG) with supercapacitor energy storage system (SCESS). As WTG installations are increasing, these systems generate a fluctuated output power as a result of varying wind speed and need to have a power smoothing capability to have a smooth output power profile. The optimal size of the SCESS is determined and a controller is proposed and implemented to continuously charge and discharge the SCESS to achieve its objectives. The SCESS is exploited to minimize the short term fluctuation to have a smooth power profile during normal operation. A bi-directional buck boost converter is used to integrate the SCESS with the system. Two back to back connected three level Neutral Point Clamped (NPC) converters are used for the power conversion. The control strategy and the system model have been developed for the NPCs, the buck boost converter and the variable speed WTG system. The Real Time Digital Simulator (RTDS) based results conducted on 2 MW/4 kV PMSG verify the effectiveness and superiority of the proposed controller.

Multiple-feedback control of power output and platform pitching motion for a floating offshore wind turbine-generator system

Abstract An approach for multiple-feedback control of generator power and nacelle fore-aft speed employing blade pitch and generator torque manipulations was developed for a spar-type floating offshore wind turbine-generator system. The development of this approach was carried out through numerical analysis using the aeroelastic simulation model (FAST), measured high wind speed data, and simulated irregular sea waves. The novelty of this multiple-feedback control approach is the increase of the generator torque in response to the platform pitching motion to the leeward side and the control of the generator power instead of the rotational speed. First, theoretical analysis of the open loop transfer function revealed that the multiple-feedback control approach improves the stability of the generator power control in the floating offshore wind turbine-generator system. Then, the optimal parameter settings of the multiple-feedback control were determined and the effectiveness of employing a first-order lag filter for the nacelle fore-aft speed was shown through a sensitivity analysis. A comparison of system performances demonstrated that the multiple-feedback control approach reduces the power output fluctuation, the platform pitching motion, and the damage equivalent fatigue load of the fore-aft bending moment at the tower-base part by 52%, 22%, and 16%, respectively, relative to the gain-scheduled feedback control of the rotational speed.

Reliability and economic assessment of a microgrid power system with the integration of renewable energy resources

The reliability assessment of a power system has become a significant subject in the power sector for both utilities and customers due to sudden increase in demand of a reliable power supply at minimal frequency and duration of power outages. This has prompted the utilities to use the accessible renewable energy resources (RERs) as measures to increase the reliability of a power system as well as reduction of over dependence on fossil fuels. The incorporation of renewable energy technologies into a radial distribution system has changed the single power source to bidirectional and multiple power sources. This improves the reliability of the system as well as reducing the power outages that associated with the radial distribution networks. In this work, wind turbine generator (WTG), photovoltaic (PV) and battery storage system (BSS) are utilized with the aim of improving the reliability of the existing microgrid power system and reducing the cost of energy (COE) and annualised cost of the system (ACS). The objective of the research work is accomplished by using the total outage cost (TOC), COE, ACS, annualized capital cost (ACC), annualized maintenance cost (AMC), annualized fuel cost (AFC), annualized emission cost (AEC), annualized replacement cost (ARC) and net present cost (NPC) of the power system. An fmincon optimization tool is utilized in this paper to investigate the effects of RERs in a microgrid system. The stochastic characteristics of the major components of RERs and their influences on the reliability of a power system are studied by using a Markov model. The proposed method is applied on the modified Roy Billinton Test System (RBTS)to establish the fact that RERs can be used to enhance the reliability and reduce the COE and ACS of the system. A comparative analysis of RERs is also carried out by studying the effects of interest rates on the COE, NPC and ACS of a power system. The results obtained from the research work demonstrate that the application of renewable energy distributed generation technologies has achieved better results.

Fuzzy Robust H∞ Tracking Control For Wind Generator System: LMI approach

This study concerns the tracking control problem of the wind turbine generator system with uncertainties parameters and external disturbances. Based on T-S fuzzy model, a fuzzy observer-based and a fuzzy robust state feedback output tracking control are developed to reduce the tracking error by minimizing the disturbance level caused by the wind speed. Using a Lyapunov function combined with H∞ tracking criteria and a judicious of the famous Young relation, a sufficient stability condition for the robust fuzzy tracking control formulated in terms of linear matrix inequality, which can be very efficiently solved by using LMI optimization techniques. The simulation results are given to show the performance of the observer-based tracking controller.

Multiple-Vector Model Predictive Power Control for Grid-Tied Wind Turbine System With Enhanced Steady-State Control Performance

Direct model predictive control (DMPC) is a promising alternative for power electronics and electric drives. It takes the switching nonlinearity of the power converters and system constraints into consideration, without using an extra modulator. However, its one-switching-vector-per-control-interval character leads to big ripples of the control variables. Therefore, with a similar sampling frequency, its steady-state performance is not satisfying. In this paper, we propose a multiple-vector direct model predictive power control (MV-DMPPC) concept for the grid-side power converter control of a back-to-back converter permanent-magnet synchronous generator wind turbine system, using a fully field programmable gate array based solution. The proposed control scheme is compared with the classical DMPPC and two recently reported DMPPC scheme with duty cycle optimizations. Both simulation and experimental tests validate that the control performances are evidently improved with the proposed MV-DMPPC solution.