Fixed Speed Wind Turbine Research Articles

Sensorless control of a power converter for a cluster of small wind turbines

This study presents a new sensorless control for small wind turbine clusters with a single power converter with a direct torque control algorithm. The proposed system consists of a wind farm connected to a back-to-back power converter that interfaces the wind farm with the AC grid. The studied wind turbines are based on fixed-speed wind turbines equipped with squirrel cage induction generators with individual pitch control. The presented structure permits to reduce the number of converters and allows to accomplish the grid codes (fault ride through capability and reactive power support). Furthermore, the generated active power can be reduced according to grid operator requirements. The presented control scheme can be applied to wind turbine repowering projects, wind farms connected to a microgrid, even, new small onshore and offshore power plants. The system performance and stability is studied and validated by means of dynamic simulations.

Fault ride-through enhancement of fixed speed wind turbine using bridge-type fault current limiter

The interaction between wind energy turbines and the grid results in two main problems, increasing the short-circuit level and reducing the Fault Ride-Through (FRT) capability during faults. The objective of this paper is to solve these problems, for fixed speed Wind Energy Systems (WECS), utilizing the bridge-type Fault Current Limiter (FCL) with a discharging resistor. A simple cascaded control system is proposed for the FCL to regulate the terminal voltage of the generator and limit the current. The system is simulated on PSCAD/EMTDC software to evaluate the dynamic performance of the proposed WECS compensated by FCL. The simulation results show the potentials of the FCL as a simple and effective method for solving grid interconnection problems of WECS.

DFIG WIND TURBINES CONTROLL BY PSO ALGORITHM

Wind turbine is system that uses a number of blades, wind energy and get it into usable mechanical energy. Variable speed wind turbines is quickly replacing with fixed speed wind turbine Because of the better power quality. On the other hand, DFIG generators due to injection and reactive power control and no need for capacitor banks, assigned more usages. The existence of active and reactive power controller for controlling the power output of the wind turbine based on DFIG provides the context interference controllers system with other modes. in this paper we used the PSO algorithm because of the its merits including increasing the accuracy and improving the results. With this algorithm can improve application speed and control the rate of degradation using the mutation operator. That's why in this article to control the DFIG wind turbines PSO algorithm is used.

Recognition and assessment of different factors which affect flicker in wind turbines

Similar to other distributed generation sources, wind turbines cause power quality disturbances (PQDs) issues in power systems. One of the most important PQDs that has bad effects on sensitive loads is flicker. In this study, an algorithm is presented for assessment and recognition of different factors causing flicker of wind turbines. Some aerodynamic factors (wind shear and tower shadow) and some mechanical factors (blade pitching errors, gearbox tooth crash and turbine blade break down) are modelled using fixed speed wind turbines. Then, wavelet transform and S-transform are used to extract some dominant features voltage. Then, in order to avoid large dimension of feature vector, Relieff feature selection method is applied to extracted features. The probabilistic neural network (PNN) is used to classify above-mentioned factors. The only adjusted parameter of the PNN classifier is determined by using the particle swarm optimisation technique. Moreover, the short-term severity of flicker (Pst) is calculated for each type of fault as extra features to increase the severability of extracted features. Results show that the classifier can detect different causes of flicker event with high detection accuracy.

SSR Damping in Fixed-Speed Wind Farms Using Series FACTS Controllers

Subsynchronous resonance (SSR) damping in fixed-speed wind turbine generator systems (FSWTGS) by using two series flexible ac transmission system (FACTS) devices, the thyristor-controlled series capacitor (TCSC), and gate-controlled series capacitor (GCSC) are studied in this paper. The former is a commercially available series FACTS device, and the latter is the second generation of series FACTS devices using gate turnoff (GTO) or other gate-commuted switches. The GCSC is characterized by a fixed capacitor in parallel with a pair of antiparallel gate-commuted switches enabling rapid control of series impedance of a transmission line. It is shown that the SSR damping with a GCSC is limited to changing the resonance frequency, in comparison with a fixed capacitor, which may not be adequate to damp out the SSR. Therefore, a supplementary SSR damping controller (SSRDC) is designed for the GCSC. Moreover, it is proven that the GCSC equipped with a well-designed SSRDC can effectively damp the SSR in FSWTGS. In order to verify the effectiveness of the GCSC in SSR damping, its performance is compared with the TCSC, which is an existing series FACTS device. In addition, time-frequency analysis (TFA) is employed in order to evaluate and compare the SSR time-varying frequency characteristics of the GCSC and TCSC. The IEEE first benchmark model on SSR is adapted with an integrated FSWTGS to perform studies, and extensive simulations are carried out using PSCAD/EMTDC to validate the result.

Improved Low Voltage Ride through Capability of a Fixed Speed Wind Generator Using Dynamic Voltage Restorer

Wind energy is one of the fastest growing renewable energy technologies in world. The new grid code proposes that the wind turbine should remain connected to the grid during voltage disturbances. Three phase voltage sags and faults cause reduction in voltage at the point of interconnection to the grid when fixed speed wind turbines connected to squirrel cage induction generators are employed resulting in disconnection of wind turbine from the grid. Dynamic voltage restorer is a series connected custom power device used for voltage compensation during sags and swells. In this paper, the Low voltage ride through capability of a fixed speed wind turbine is improved using dynamic voltage restorer. Simulation studies are done to determine the transient stability of a fixed speed wind turbine with squirrel cage induction generator using Matlab Simulink.

Literature Review Paper on Analysis and Control of Small Signal Stability with DFIG based Wind Power System

As a result of the increasing demand for electric power and environmental problems, the generation of electrical energy from renewable sources has increased recently. In particular, the wind power plants are integrated in large numbers to power system networks to satisfy the demand. For wind turbine energy generation, doubly fed induction generators are highly implemented owing to more advantages over fixed speed wind turbine systems. These generators can enhance the stability and power quality of the power networks. More attention had been paid by researchers so far on various issues with respect to grid integration of DFIG system. This review paper provides in-depth analysis and discussion on various aspects of DFIG fed wind power systems and its grid integration till date and also suggestions for further growth in this area for effective wind power energy management systems.

A novel control system design to improve LVRT capability of fixed speed wind turbines using STATCOM in presence of voltage fault

Abstract The design and implementation of a new control system for reactive power compensation and mechanical torque, voltage regulation and transient stability enhancement for wind turbines equipped with fixed-speed induction generators (IGs) in power systems is presented in this study. The designed optimal linear quadratic regulator (LQR) controller provides an acceptable post fault performance for both small and large perturbations. Large disturbance simulations demonstrate that the designed controller enhances voltage stability as well as transient stability of the system during low-voltage ride-through transients and thus enhances the LVRT capability of fixed-speed wind generators. Further verifications based on detailed time-domain simulations are also provided. Calculations, simulations and measurements confirm how the increased STATCOM rating can provide an increased transient stability margin and consequently enhanced LVRT capability. A concept of critical clearing time has been introduced and its utility has been highlighted.

A site-specific design of a fixed-pitch fixed-speed wind turbine blade for energy optimization using surrogate models

This work seeks to add a new approach to optimize a wind turbine blade's performance by implementing a surrogate model using the Kriging function with the chord, twist and the use of 3 different airfoils as design variables for the maximization of the Annual Energy Production. A combination of Genetic Algorithms and the SQP method for Local Search are used to exploit the model. A baseline design of the blade starts with a replica of the Phase VI blade utilized in a NASA-Ames experiment and a MatLab script utilizes the Blade Element Momentum Theory (BEM) for the aerodynamic analysis. Results show a 23% improvement in energy production by using this method.

Voltage booster scheme for enhancing the fault ride‐through of wind turbines

This study presents a new scheme for a continuously variable (CV) series braking resistor (SBR) with independent per phase controller. The CV-SBR is a CV and not stepwise. A novelty of the work presented is that the CV-SBR operates on the whole range of wind speeds. The proposed scheme is applicable to fault ride-through (FRT) of fixed speed wind turbines (FSWTs). The CV-SBR scheme is compared to the single-step (SS) and multi-steps (MS) SBRs. The CV-SBR scheme is modelled and simulated in PSCAD/EMTDC™. The performance of the wind turbine is studied for balanced and unbalanced fault scenarios. The CV-SBR scheme is advantageous over the other two candidates with its ability to limit the fault current and reduce the turbine speed deviation at any wind speed. The CV-SBR is employed with a static synchronous compensator (STATCOM) to allow FRT of FSWT connected to weak grid during nearby faults and to deliver the reactive current required by some grid codes. The CV-SBR scheme is successful in reducing voltage disturbance's consequences on the generator's mechanical system. Simulation results show that the CV-SBR allows FRT of FSWT connected to weak grid where the STATCOM alone is not able to sufficiently enhance the FRT of FSWT during nearby faults.

HIGHER STAGE DEVELOPMENT OF A FUZZY PI CONTROLLER FOR A GRID CONNECTED WIND ENERGY AND CONVERSION SYSTEM

In recent years power generation from renewable energy sources has gained importance in view of supplementing the power obtained from conventional sources. Out of all the renewable energy sources, wind energy conversion system is the greatest contributor to the power generations. During the recent years use of variable speed of the wind turbine is gaining much more importance than the fixed speed wind turbine. Important factors regarding variable speed operation are that it is easy to control and is even more efficient. Therefore, it is important to study the machine modelling of the double fed induction generator (DFIG) for a wind energy conversion system (WECS). One of the major areas in renewable power control includes the grid connected DFIG based WECS. Typically a DFIG based WECS consists of a Wind turbine connected to a DFIG and then the turbine-coupled DFIG is connected to the grid through a power electronic AC-AC converter. In this Paper a grid connected wind energy conversion system using a simple PI controller is developed and then a fuzzy PI controller is designed to resolve the problem. Finally a comparison has been made to fuzzy controller from the simulation results, observing the efficiency of variation of DC link voltage variation. --------------------------------------------------------------------***------------------------------------------------------------------

A Combined Approach of Using an SDBR and a STATCOM to Enhance the Stability of a Wind Farm

This paper presents a method to enhance the stability of a grid-connected wind farm composed of a fixed-speed wind turbine generator system (WTGS) using a combination of a small series dynamic braking resistor (SDBR) and static synchronous compensator (STATCOM). The SDBR and STATCOM have active and reactive power control abilities, respectively, and a combination of these units paves the way to stabilize well the fixed-speed wind farm. In this paper, a centralized control scheme of using an SDBR and a STATCOM together is focused, which can be easily integrated with a wind farm. Different types of symmetrical and unsymmetrical faults are considered to evaluate the transient performance of the proposed control scheme, applicable to a grid-connected wind farm. The effect of a multimass drive train of a fixed-speed WTGS in fault analysis, along with its importance in determining the size of the SDBR to augment the transient stability of a wind farm, is investigated. Extensive simulation analyses are performed to determine the approximate sizes of both SDBR and STATCOM units. Dynamic analysis is performed using real wind speed data. A salient feature of this work is that the effectiveness of the proposed system to minimize the blade-shaft torsional oscillation of a fixed-speed WTGS is also analyzed. Simulation results show that a combination of a small SDBR and STATCOM is an effective means to stabilize the wind farm composed of a fixed-speed WTGS.

Generalized State Estimation of Flexible AC Power Systems Considering Wind Generators and Primary Frequency Control

This paper proposes a practical approach to incorporate the mathematical models of both fixed-speed and variable-speed wind turbine generators, automatic load frequency controls as well as voltage magnitude and frequency dependent loads into a weighted least squares-based state estimation algorithm suitable for the analysis of flexible alternating current (AC) transmission systems. As opposed to conventional static state estimators, where the inclusion of these electric components has been neglected so far, the proposed approach permits the determination of the steady state operation of a power system in the event of a supply-demand unbalance by estimating the magnitude of the frequency deviation from its nominal value. The state estimation is based on measurements related to those that should be obtained by a supervisory control and data acquisition (SCADA) system and phasor measurement units. For the purpose of this paper, the set of values associated with SCADA measurements (nodal power injections, power flows, and voltage magnitudes) and phasor measurement unit (PMU) measurements (voltage and current phasors) are generated from a power flow analysis of the network under study. Lastly, numerical simulations are reported to demonstrate the effectiveness of the proposed approach.

Automated on‐line fault prognosis for wind turbine pitch systems using supervisory control and data acquisition

Current wind turbine (WT) studies focus on improving their reliability and reducing the cost of energy, particularly when WTs are operated offshore. A supervisory control and data acquisition (SCADA) system is a standard installation on larger WTs, monitoring all major WT sub-assemblies and providing important information. Ideally, a WT's health condition or state of the components can be deduced through rigorous analysis of SCADA data. Several programmes have been made for that purposes; however, the resulting cost savings are limited because of the data complexity and relatively low number of failures that can be easily detected in early stages. This study proposes a new method for analysing WT SCADA data by using an a priori knowledge-based adaptive neuro-fuzzy inference system with the aim to achieve automated detection of significant pitch faults. The proposed approach has been applied to the pitch data of two different designs of 26 variable pitch, variable speed and 22 variable pitch, fixed speed WTs, with two different types of SCADA system, demonstrating the adaptability of the approach for application to a variety of techniques. Results are evaluated using confusion matrix analysis and a comparison study of the two tests is addressed to draw conclusions.

Improving Transient Stability in a Grid-Connected Squirrel-Cage Induction Generator Wind Turbine System Using a Fuzzy Logic Controller

A common problem in wind power plants involves fixed-speed wind turbines. In fact, being equipped with a squirrel-cage induction generator (SCIG), they tend to drain a relevant amount of reactive power from the grid, potentially causing voltage drops and possible voltage instability. To improve SCIG power quality and transient stability, this paper investigates a new control strategy for pitch angle control based on proportional-integral (PI) controller and a fuzzy logic controller (FLC), considering both normal and fault ride-through (FRT) schemes. In the literature, often, the mechanical torque output is assumed constant for a specific wind speed. This might not be accurate, because the mechanical torque-speed typical of a wind turbine depends also on the power coefficient or pitch angle. In this paper, an analytic model of transient stability is proposed using the equivalent circuit of the SCIG and using the concepts of stable and unstable electrical-mechanical equilibrium. The method has been evaluated by comparing the results obtained by the analytic method with the dynamic simulation. The results show that the proposed hybrid controller is effective at smoothing the output power and complying with FRT requirements for SCIG in the power system.

Incorporation of fixed speed wind turbine generators in load flow analysis of distribution systems

Small scale wind farms are increasingly being integrated into distribution systems. This paper proposes a simple model of a fixed speed wind farm and incorporates that model into a standard load flow program of a distribution system. For each wind farm, the proposed model augments the size of the network by two buses that allow including all parameters of the generator. For a given wind speed, the mechanical power of the wind turbine is first determined from manufacturer's supplied data and then it is incorporated into one of the new buses as a negative load. This would allow evaluating the load flow results of the system using any standard load flow program without modifying the source codes of the program. The effectiveness of the proposed method is then evaluated on a simple system as well as on two distribution systems consisting of 33 and 69 buses.

Low voltage ride-through enhancement of fixed-speed wind farms using series FACTS controllers

This paper studies the application and control of three series flexible AC transmission system (FACTS) devices namely, the gate-controlled series capacitor (GCSC), the thyristor controlled series capacitor (TCSC), and series braking resistor (SBR), in order to enhance the low voltage ride-through (LVRT) in fixed-speed wind turbine generator systems (FSWTGS). Modeling and simulations are carried out in order to investigate and compare the performance of these devices, considering (1) successful reclosing of circuit breakers (CBs), (2) unsuccessful reclosing of CBs, and (3) connection of a dynamic load to the point of common coupling (PCC). Simulation results exhibit significantly enhanced transient stability of FSWTGS due to the employment of the GCSC. Furthermore, the GCSC is competitive with the TCSC and the SBR, and it requires less power rating to stabilize the wind generator system. Therefore, the proposed GCSC can be considered an effective tool to improve the LVRT of FSWTGS.

A STATCOM with Supercapacitors for Low-Voltage Ride-Through in Fixed-Speed Wind Turbines

Fixed-speed wind generator (FSWG) technology has an important presence in countries where wind energy started to be developed more than a decade ago. This type of technology cannot be directly adapted to the grid codes, for example those requirements related to the immunity level under voltage dips. That behavior is typically referred as low-voltage ride through (LVRT), and it usually implies certain reactive and active power injection requirements, both during a voltage dip and during the voltage recovery. In this context, a review is presented of the LVRT exigencies present in some of the countries with the most advanced grid codes (Denmark, Germany, Spain and the United Kingdom). In this paper, the capabilities of STATCOM-based devices for fulfilling the LVRT requirements in FSWGs are analyzed. For this purpose, two technologies are considered: a STATCOM with a supercapacitor, which improves its energy storage features; and a STATCOM with a supercapacitor and a DC-DC converter, to achieve higher discharge levels.

Wind Energy Conversion Based on Matrix Converter

In recent years renewable sources such as solar, wave and wind are used for the generation of electricity. Wind is one of the major renewable sources. The amount of energy from a Wind Energy Conversion System (WECS ) depends not only on the wind at the site, but also on the control strategy used for the WECS. In assistance to get the appropriate wind energy from the conversion system, wind turbine generator will be run in variable speed mode. The variable speed capability is achieved through the use of an advanced power electronic converter. Fixed speed wind turbines and induction generators are often used in wind farms. But the limitations of such generators are low efficiency and poor power quality which necessitates the variable speed wind turbine generators such as Doubly Fed Induction Generator (DFIG) and Permanent Magnet Synchronous Generator (PMSG). A high-performance configuration can be obtained by using Scherbius drive composed of a DFIG and a converter in combination AC-DC-AC connect between stator & rotor points for providing the required variable speed operation. DOI: http://dx.doi.org/10.11591/ijpeds.v5i1.6025

Comparative Study of the Behavior of a Wind Farm Integrating Three Different FACTS Devices

Improving grid connection of wind farms is a relevant issue to be addressed, especially for fixed-speed wind turbines. Certain elements, such as FACTS (Flexible AC Transmission Systems), are able to perform voltage and reactive power regulation in order to support voltage stability of wind farms, and compensate reactive power consumption from the grid. Several devices are grouped under the name of FACTS, which embrace different technologies and operating principles. Here, three of them are evaluated and compared, namely STATCOM (Static Synchronous Compensator), SVC (Static Var Compensator) and SSSC (Static Synchronous Series Compensator). They have been modeled in MATLAB / Simulink, and simulated under various scenarios, regarding both normal operation and grid fault conditions. Their response is studied together with the case when no FACTS are implemented. Results show that SSSC improves the voltage stability of the wind farm, whereas STATCOM and SVC provide additional reactive power.