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Control of a wind-driven self-excited induction generator supplying an induction motor load for maximum utilization
Abstract
This paper presents steady-state analysis and control of a
wind-driven stand-alone 3-phase self-excited induction generator
supplying a 3-phase induction motor. The induction motor drives
mechanical load (such as a water-pump) which has a given speed-torque
characteristics. The steady-state equivalent circuit of the system is
analyzed using the node-admittance method and the results are utilized
to determine the optimum operating conditions for maximum utilization
efficiency
... This can be attributed to the demagnetization of E with decrease in b till a point where the magnetizing reactance surpasses its critical value. However research has proved that an increase in the value of excitation capacitance per phase increases the allowable speed range of an induction machine for a given range of loading [13]. A two-stage successive connection of 20 μF each in parallel to the existing 60 μF connection was applied and the above analysis was repeated. ...
This paper describes the development of a simple maximum power extracting (MPE) scheme for Wind Electric Energy Conversion System (WECS) comprising of an induction generator, capacitor banks, a diode bridge rectifier, dc link inductor and a line commutated inverter feeding the grid. Steady state analysis of Self Excited Induction Generator (SEIG) is done with the MATLAB programming. The operational speed range of SEIG is decided by proper choice of excitation capacitor banks. MPE is achieved over this speed range by the adjustment of the inverter firing angle that loads the system appropriately to extract maximum power for any given value of input rotor speed. A unique one-to-one relation between per unit rotor speed input and the predetermined inverter firing angle corresponding to MPE has been developed in the form of look-up table. The entire system has been simulated and modelled using the power system block set in MATLAB to obtain the results. The experimental and simulated waveforms validate the system performance.
This paper discusses a new control scheme of a three-phase grid-connected wind energy conversion system (WECS). The control uses maximum power point tracker (MPPT) for optimal use of the wind energy. The wind turbine generator (WTG) consists of a variable speed wind turbine and the MPPT is implemented via a dc-dc boost converter. A three-level voltage source inverter (VSI) is used as interface with the ac power grid. The switching pattern generation for the VSI is achieved using SVM. Mamdani's FLC is applied in DC bus voltage control and current control. Validation of models and control schemes is performed by using the MATLAB/Simulink.
This article deals with the hardware implementation of a static-compensator-based voltage regulator for an isolated asynchronous generator supplying induction motor loads. The asynchronous generator is driven by a constant speed prime mover to feed a set of induction motors and unbalanced loads. The static-compensator-based voltage regulator is implemented using a dSPACE DS1104 digital signal processor (DSP) controller. Extensive tests are conducted to demonstrate the capability of the controller to feed the dynamic loads and the ability to function as a voltage regulator, a load balancer, and a harmonic eliminator.
An analytical technique using the `Newton-Raphson¿ method is presented to identify the saturated magnetising reactance and the generated frequency of a self-excited induction generator for a given capacitance, speed and load. The technique is shown to be very efficient in analysing such systems under steady state. Computed results are compared with the experimentally obtained values on a laboratory machine, and a reasonable correlation has been observed. Effects of various system parameters on the steady-state performance have been studied, and the results presented provide guidelines for optimum design of such systems.
A wind energy conversion scheme using an induction machine driven by a variable speed wind turbine is described. Excitation control has been obtained by employing a single value capacitor and thyristor controlled inductor. Wind speed cube law is proposed to be followed in loading the induction machine for maximising energy conversion. Performance characteristics of the generation scheme have been evaluated over a wide speed range. Harmonic analysis of the proposed scheme shows that harmonic currents and their associated power loss is negligible.
The increasing rate of depletion of conventional energy resources and the ability of induction generators to convert mechanical power over a wide range of rotor speeds have given rise to an interest in the possible contribution of wind energy to provide fuel displacement. An arrangement using a capacitor-excited induction generator and a variable speed drive to supply resistive load is described. A method for determining the output voltage and frequency in the steady-state is presented. Comparison of the predicted behavior of this isolated system with the experimental results shows good agreement between the tow.
The role of renewable energy sources in meeting the energy needs of developing countries is examined in the context of the burgeoning fuel prices and the associated geopolitical realities and economic burdens. The acute energy needs and the unavailability of commercial fuels in the rural areas offer a rewarding opportunity for the utilization of locally available renewable energy sources. Small-scale decentralized integrated system concepts for harnessing renewable energy sources are discussed. The basic economic factors involved in the introduction of renewable energy sources in the rural areas of developing countries are outlined to assist the designer in the selection of appropriate components and system concepts.
The influence of the excitation capacitor on the steady state
performance characteristics of an isolated self-excited induction
generator feeding a balanced load is examined. It is shown that the
terminal capacitor must have its value within a certain range to sustain
self-excitation. If the value of the excitation capacitor is outside
this range, self-excitation will not be possible. Moreover, if the load
impedance is below a certain value, self-excitation will not be achieved
irrespective of the value of the excitation capacitor. In the
capacitance range where self-excitation is possible, it's value strongly
influences the induction generator performance characteristics. The
value of capacitance can be selected so that the terminal voltage is
constant, regardless of the generator output power. It is further shown
that under such condition, the value of capacitance is influenced by the
load as well as by the load power factor. The generator performance is
however independent of the load power factor and is only affected by the
magnitude of the load impedance
Photovoltaic (PV) powered DC motors driving dedicated loads (e.g.
water pumps) are increasingly used in the remote rural areas of many
developing countries. The key to their success is simplicity (direct
coupling, no DC-AC conversion, no storage batteries, etc.). Because of
the relatively high cost of the PV array, the system designer is
interested in maximizing its utilization efficiency. A PV powered DC
motor can also be used to drive a three-phase self-excited induction
generator (SEIG). This arrangement is useful as part of an integrated
renewable energy system (IRES), which takes advantage of the inherent
diversity of wind and solar energy in most developing countries to
improve power quality. The SEIG is driven by a wind-turbine, DC motor,
or both. Another advantage of this arrangement is its versatile control
characteristics through the DC motor control. This paper describes a
technique to maximize the utilization efficiency of the PV array by
controlling the field current of the DC motor through a DC chopper
Photovoltaic (PV) powered DC motors driving dedicated loads (e.g.
water pumps) are increasingly used in the remote rural areas of many
developing countries. The key to their success is simplicity (direct
coupling, no DC-AC inversion, no storage batteries, etc.). In this
paper, a PV powered DC motor is used to drive an isolated three-phase
self-excited induction generator (SEIG). It is found that due to the
unique torque-speed characteristics of the SEIG, utilization efficiency
is close to maximum at all insolation levels with no peak-power
tracking. The proposed arrangement is useful as part of an integrated
renewable energy system (IRES), which takes advantage of the inherent
diversity of wind and insolation in most developing countries to improve
power quality. The SEIG is driven by wind turbine, DC motor, or both.
Performance of the system under different insolation conditions is
analyzed
Dependency of the output voltage and frequency of the isolated
self-excited induction generator on the speed, load, and terminal
capacitance causes certain limitations on its performance. In this
study, the performance of the induction generator under a wide range of
operating conditions is examined. It is found that the machine operates
only in certain element ranges and that all generated currents and
voltages are bounded. It is also shown that a combination of these
elements exists that is optimal for maximum power generation
Alternating Current Machines
- M G Say
M. G. Say, Alternating Current Machines, London: Pitman, 5th Ed., 1983, pp. 333-336.