Double Output Induction Generator Research Articles

Influence of idling and short circuits on the self-excitation of a classical double-output induction generator

Experimental results for the capacitor self-excitation of an induction generator with a short-circuited phase rotor and a classical double-output induction generator are compared. The influence of the preceding conditions on the capacitor self-excitation of a classical double-output induction generator is the opposite of that for an induction generator with a short-circuited phase rotor. For the classical double-output induction generator, self-excitation is better after a three-phase short circuit than after idling.

Effect of wind speed and load power factor variation on optimal sizing of the machine and converters for double output induction generator based stand-alone wind energy conversion systems

In this paper, an algorithm for finding out the optimal ratings of the machine and power electronic converters of a wind turbine driven stand-alone double output induction generator based variable speed constant frequency generation system is reported, which seeks to minimize the cost of energy generation. The nonlinear constrained optimization technique employed includes, among others, the reactive power balance constraints, which are not often considered for stand-alone systems. For this purpose, the load power factor is modeled as a random variable with known probability density function. The total energy captured is calculated for a given wind velocity density function and load power factor density function. The proposed method finally finds the optimum combination of machine and converter ratings, which results in minimum cost of energy. The effects of changes in load power factor and wind velocity distribution are also discussed in detail.

Decoupled, Reduced Order Model for Double Output Induction Generator Using Integral Manifolds and Iterative Separation Theory

Decoupled, Reduced Order Model for Double Output Induction Generator Using Integral Manifolds and Iterative Separation Theory

Steady and transient state experimental investigation of the double output induction generator in autonomous operation

The operation and the experimental verification of an induction machine operating as double output induction generator, in autonomous situation, suitable for a wind energy conversion system are presented in this work. The system performance is studied considering the variations of the excitation voltage, and frequency and of the speed of rotation of the driving machine. The obtained results show the limits of stable operation and also indicate the possibilities of this system to achieve better utilisation of the available wind energy.

Discussion on the qd/qd model of slip energy recovery drive

The transient and steady-state models of slip energy recovery drive (SERD) are obtained in synchronously rotating reference frame in [P.C. Krause, O.Wasynczuk, M.S. Hildebrandt, Reference frame analysis of a slip energy recovery system, IEEE Trans. Energy Convers. 3 (2) (1988) 404–408; E. Akpinar, R.E. Trahan, A.D. Nguyen, Modeling and analysis of closed-loop slip energy recovery induction motor drive using a Linerizatio technique, IEEE Trans. Energy Convers. 8 (4) (1993) 688–697; S.A. Papathanassiou, M.P. Papadopoulos, State-space modeling and eigenvalue analysis of slip energy recovery drive, IEE Proc. Electr. Power Appl. 144 (1) (1997) 27–36; M.Y. Üçtuğ, İ. Eskadarzadeh, H. İnce, Modelling and output power optimization of a wind turbine driven double output induction generator, IEE Proc. Electr. Power Appl. 141 (2) (1994) 33–38]. The steady-state solution is provided in [P.C. Krause, O.Wasynczuk, M.S. Hildebrandt, Reference frame analysis of a slip energy recovery system, IEEE Trans. Energy Convers. 3 (2) (1988) 404–408; M.Y. Üçtuğ, İ. Eskadarzadeh, H. İnce, Modelling and output power optimization of a wind turbine driven double output induction generator, IEE Proc. Electr. Power Appl. 141 (2) (1994) 33–38]. A fourth and fifth order transient models are obtained in [E. Akpinar, R.E. Trahan, A.D. Nguyen, Modeling and analysis of closed-loop slip energy recovery induction motor drive using a Linerizatio technique, IEEE Trans. Energy Convers. 8 (4) (1993) 688–697; S.A. Papathanassiou, M.P. Papadopoulos, State-space modeling and eigenvalue analysis of slip energy recovery drive, IEE Proc. Electr. Power Appl. 144 (1) (1997) 27–36], respectively. These models can be used to predict the performance, when the effect of overlap angle and rectifier input current harmonics are ignored, and the rectifier input power factor is also assumed to be unity. In this paper, both models are solved in Matlab and results are compared to the results of Simulink model of the SERD.

Operation of induction generator in the magnetic saturation region as a self-excited and as a double output system

This paper presents the development of two dynamic models for simulating the operation of an induction machine with saturation considered, operating either as self-excited or as double output induction generator in autonomous wind systems. Both systems’ steady state as well as transient performance during switching on and off from the bank of capacitors or the power line, respectively, is studied considering different wind speed and excitation conditions. A polynomial approximation of the variation of mutual inductance versus magnetizing current is used for the proper account of the effects of core saturation. The transient voltage and current built-up of the two systems, the harmonic distortion as well as the damping of the transient process are obtained from a laboratory autonomous wind generating system. From a comparison between the outputs generated by the two systems the results show that the double output induction generator can be installed for the better use of the wind energy.

Development of an experimental investigation procedure on double fed electric machine-based actuator for wind power systems

The implementation and the experimental validation of a double fed machine-based actuator operating as double output induction generator in a wind energy conversion system are presented. The system performance is studied considering the variations of the excitation voltage, the excitation frequency and that of the wind speed. The obtained results show the limits of stable operation and also indicate the possibilities of this system in order to better utilise the wind energy.

00/02008 Sliding mode control for efficiency optimization of wind energy systems with double output induction generator

00/02008 Sliding mode control for efficiency optimization of wind energy systems with double output induction generator

Sliding mode control for efficiency optimization of wind energy systems with double output induction generator

This paper deals with generation efficiency maximization of wind energy conversion systems (WECS) with double output induction generator (DOIG). In the first place, to design a sliding mode controller, an apropos model of the DOIG with electronic drive in the rotor is developed. Then, conditions of maximum power generation are obtained. Finally, a sliding mode control strategy for this type of WECS is presented. The proposed strategy varies the firing angle of the electronic drive in order to set the extreme control values equal to the maximum and minimum available control action of the system. Consequently, robustness to 001Uparametric uncertainties and external disturbances is maximised. Copyright © 2000 John Wiley & Sons, Ltd.

Dynamic behavior of variable speed wind turbines under stochastic wind

It is recognized that the most important advantage of the variable speed wind turbines (VS WTs) over the conventional constant speed (CS) machines are the improved dynamic characteristics, resulting in the reduction of the drive train mechanical stresses and output power fluctuations. In this paper alternative configurations of the electrical part of a VS WT are considered, using a squirrel cage induction generator and voltage or current source converters, as well as a double output induction generator with a rotor converter cascade. The WT operation is simulated for typical wind speed time series and the examined schemes are comparatively assessed. It is shown that, using suitable converters and controls, a great reduction of the mechanical stresses and output power fluctuations can be achieved, compared to the CS mode of operation of the WT.

Analysis and modeling of the steady state behavior of the static Kramer induction generator

A steady state analysis of the static Kramer variable speed double output induction generator is conducted using a hybrid dq model wherein stator variables only are transformed onto a reference frame fixed to the rotor. Rotor variables are retained in their natural abc form, allowing diode bridge overlap together with switching effects in the rectifier and inverter to be catered for. For constant speed operation, the system equations are reduced to a set of linear differential equations with constant coefficients which are solved analytically to predict generator performance. Simulated performance is verified experimentally showing very good agreement with measurement.

Performance evaluation of a wind driven DOIG using a hybrid model

This paper presents the performance analysis of a wind-driven double output induction generator (DOIG) operating at varying shaft speeds. A periodic transient state analysis of DOIG equipped with two controlled power converters is carried out using a hybrid induction machine model. It is shown that practical aspects of power converters such as overlap and harmonics reduce the power output of the DOIG system and limit the operating shaft speed range, especially in the subsynchronous region near the synchronous speed. The validity of the mathematical model used in the analyses and the corresponding computer simulation results are verified experimentally.

WIND-DRIVEN, VARIABLE-SPEED, VARIABLE-FREQUENCY, DOUBLE-OUTPUT, INDUCTION GENERATORS

ABSTRACT In this paper the performance of a self-excited, wind-driven, variable-speed, variable-frequency, double-output induction generator (VSVF-DOIG ) is presented This Generator will be used to supply frequency insensitive loads such as space heating. For the capacitor-excited machine, the stator frequency varies with the rotor speed, thereby yielding a small value of slip. Thus, the minimum capacitance under load can be approximately predicted in terms of the wind speed. The control methodology is the following. The rotor is short-circuited. As the rotor speed increases, the capacitance is diminished until the stator current, the stator voltage and the rotor speed reach their rated values. With further increases of the rotor speed, the capacitance, the stator current and the rotor current are held constant and additional power is extracted from the system by adjusting the resistive load in the rotor circuit. Hence this control strategy allows more than rated power to be extracted from the induction machine without overheating it. The theoretical results of this investigation are verified experimentally.

OPTIMAL PERFORMANCE OF DOUBLE OUTPUT INDUCTION GENERATOR USED IN WECS

ABSTRACT In this paper a new technique for optimizing the power generated by a double output induction generator (DOIG) is established. The proposed control strategy ensures stable operation of the DOIG within a wide speed range without overheating the machine. The proposed scheme employed a controllable rectifier, a d. c. link, an inverter, and an isolating transformer in the rotor circuit. Variation of firing angles, overlap angle, voltages, and powers with speed are deduced. Experimental results are given. Results showed that twice the rated machine power is generated at S=-l.

Maximum power tracking for a wind driven induction generator connected to a utility network

The paper proposes a simple control strategy that is applied to a grid connected wind driven system to facilitate harnessing maximum power. The principles of this strategy are demonstrated in a system which comprises a double-output induction generator driven by a variable-speed wind turbine. This strategy is based on controlling the slip power, which is extracted from the rotor circuits and fed to the grid though a rectifier/inverter branch. The firing angle of the inverter is used to control the slip power and, hence, the operating point. A mathematical model is presented to analyse the behaviour of the system and to demonstrate the capability of the proposed control strategy. An experiment has been conducted to verify the validity of the control strategy and the calculation methodology. A good agreement with the computed results has been obtained.

Modelling and output power optimisation of a wind turbine driven double output induction generator

In the paper, a double output induction generator (DOIG) driven by a wind turbine is studied. The reference frame model of the system including a fully controlled rectifier on the rotor side is derived. Based on this model, the steady-state equations are obtained in terms of the stator and rotor currents, rotor voltage and the slip. These equations are solved both with a model of a wind turbine and that of a DC motor driving the DOIG. The results are compared with experimental ones. Finally, an optimisation problem is formulated to investigate the conditions of transferring maximum power from the wind turbine to the grid system, and it is shown that using a DOIG in either subsynchronous or supersynchronous modes, it is possible to transfer maximum power to the network in a wide range of wind speeds without exceeding the ratings of the induction generator.

Double-output induction generator operating at subsynchronous and supersynchronous speeds: steady-state performance optimisation and wind-energy recovery

The paper covers the steady-state analysis of a wound-rotor induction generator operated at varying shaft speeds in the subsynchronous and supersynchronous regions, by control of both the magnitude and direction of slip power. A modified equivalent circuit is used in the analyses in which core losses and harmonics are ignored. The resulting nonlinear algebraic equations are solved numerically. An optimum control strategy, which maximises the total electrical power output of the double output induction generator is determined, and theoretical results are verified experimentally with particular emphasis on the system including naturally commutated convertors. The limitations of naturally commutated convertor circuits and their effects on the output power characteristic of the system are also discussed. This system shows considerable advantage in the field of wind-energy conversion. Its performance is optimised on the basis of annual energy production by calculating optimum values of gear ratio and generator size for the given turbine characteristic and site wind regime. Also, a comparison is made among optimised versions of alternative induction generator schemes used in wind-energy conversion systems, on the bases of annual energy production and transfer characteristic for the same site and turbine.

Microprocessor control of double output induction generation. I. Inverter firing circuit

The design and implementation of a firing scheme using the INTEL 8086 microprocessor to control the inverter firing angle of the variable-speed constant-frequency double-output induction generator (VSCF-DOIG) are described. The microprocessor is used to control the phase shift of the DC-linked inverter of the VSCF-DOIG. It computes the voltage signals from a reference voltage potentiometer and then outputs the calculated firing-angle shifting time (as opposed to deriving it from a table lookup method) to the interface timer. This gives full-range control of the firing angle between 0 degrees and 180 degrees , and updates the phase-shifting timer in each cycle on the basis of the values of the previous three cycles. The control circuit is designed for multitask purposes. The hardware, software, interface, input/output, and experimental results are presented.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Microprocessor Control of Double Output Induction Generator, Part I: Inverter Firing Circuit

This paper investigates the design and implementation of a firing scheme using the INTEL 8086 microprocessor to control the inverter firing angle of the Variable Speed Constant Frequency Double Output Induction Generator (VSCF-DOIG). The INTEL 8086 microprocessor is used to control the firing angle of the DC-linked inverter of the VSCF-DOIG. In this system, the microprocessor computes the voltage signals from a reference voltage pot and then outputs the calculated firing angle shifting time (as opposed to deriving it from a table look-up method) to the interface timer. This gives full range control of the firing angle between 0° and 180°, and updates the phase shifting timer in each cycle based on the values of the past three cycles. The control circuit is designed for multi-tasked purpose. The hardware, software, interface, I/O, and experimental results are presented in this paper.

Analysis of the Double Output Induction Generator Using Direct Three-phase Model Part II - Harmonic Analysis

This paper investigates the harmonic content of the rotor current, rotor voltage and the torque of the variable speed constant frequency double output induction generator (VSCF-DOIG). The waveforms of these variables were generated using a direct three-phase model and then analyzed numerically for their harmonic content using a Fourier series subroutine. In addition, this paper investigates the stator distortion currents that are being induced in the stator windings by the rotor current harmonics at frequencies which are not an integral multiple of the stator fundamental frequency. As a check on the analysis the calculated stator current waveform is compared with the experimental oscillogram.