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In this paper modelling and analysis in autonomous mode of dual three-phase induction generator (DTPIG) with a new algorithm have been done. We develop the steady state model of a dual three-phase self-excited induction generator for stand-alone renewable generation dispensing with the segregating real and imaginary components of the complex impedance of the induction generator. The obtained admittance yields the adequate magnetizing reactance and the frequency. These two key parameters are then used to compute the self-excitation process requirements in terms of the prime mover speed, the capacitance and the load impedance on the one hand and to predict the generator steady state performance parameters on the other. Steady state performances and characteristics of different configurations are clearly examined and compared. The analytical results are found to be in good agreement with experimental results.

The power rating of an ac drive system can be increased by using multi-phase drives system which has more than three phases in the stator of the machine. Multi-phase drives system possesses several advantages over conventional three-phase drives, such as reducing the amplitude and increasing the frequency of the torque pulsation, reducing the rotor harmonic currents, reducing the current per phase without increasing the voltage per phase, lowering the dc-link current harmonics, power segmentation and high reliability [

multi-phase induction machine drives are mainly related to the high-power and/or high-current applications such as in electric ship propulsion, in locomotive traction, in aerospace applications and in electric/hybrid vehicles [

As a result, a multi-phase line with smaller dimensions can be used to transmit a larger amount of power covering entire range of transmission voltages [

An imperative step in the steady state analysis of a self-exited DTPIG is to determine the magnetizing reactance

This paper, therefore, presents detailed investigations of self-excitation process with and without load condition. The machine performances are computed by solving the mathematical method of the developed steady state model via a numerical method. The computed results are compared with the experimental ones to validate the developed model. In this context we organized a paper as follows. Section 2 gives a detailed model of the self-exited dual three-phase induction generator. System studies, simulation and experimental results including steady state performance of the self-excited DTPIG, are presented in Section 3. Conclusions are drawn in Section 4.

Often, steady state performances of SE-DTPAG are based on per phase equivalent circuit. This latter, is shown

in figure 1 where

1 and 2 resistance, rotor resistance (referred to stator), stator 1 and 2 leakage reactance, mutual leakage reactance between the two stator, magnetizing reactance, rotor leakage reactance (referred to stator), excitation capacitor reactance, load resistance and the generator slip respectively. All parameters are considered constant except the magnetizing reactance and the generator slip which vary respectively according to the saturation characteristic and the prime mover speed. In this model the core loss component is neglected.

The other assumptions are the same. The steady state equations for a dual three-phase induction generator are given:

When the self-excited DTPIG is driven by dc machine in which the shaft speed is maintained constant. All parameters are fixed but both

At note “B” in

where:

Hence, equation (2) can be written as:

Under normal operating condition, the stator voltage

This implies that both the real and imaginary parts of (6) would be separately zero.

Resolution of (7) leads to find the values of frequency

citation capacitor, speed, and electrical passive load.

At note “A” in

When the two sets of stator three-phase windings are identical, then we can write:

Using the method FZERO, we can predict the necessary parameters to evaluate the performance characteristics of the dual three-phase SEIG.

To test the validity of the proposed method of analysis, and to investigate the performance characteristics of the DTPIG, the machine parameters of the equivalent circuit and simulation results have been considered. For this purpose, a dual three-phase induction machine, 230/380 V, 0.75 A, 4-pole, 50 Hz, Y-connected, was utilized. With load and blocked rotor tests were conducted to determine the parameters of the test machine for two schemes of operation. Computer tests were carried out with the star connected capacitors banks, connected to both three-phase sets of windings. A detailed study of steady state performance of the dual three-phase asynchronous generator indicates that for different operating conditions such as change in speed and different values star capacity.

The proposed method for computing the DTPIG performance is applied to a squirrel cage induction machine. In this proposed method, no further algebraic manipulations of the equations are needed. A numerical MATLAB function “FZERO” used in order to find root of this continuous function of one variable, which is the frequency. This function Find root of continuous function of one variable. This later, is a handle function, the “@.” operator constructs a function handle Equation (7), and assigns the handle to the output variable which is the frequency F. After the evaluation of the frequency, the magnetizing inductance can be deduced. This simple method reduces the time and effort needed to predict these necessary parameters to evaluate the performance characteristics of the SE-DSAG. With this method, the changing of the load type or including the core less resistance, do not oblige us to repeat the entire program. Alternatively, the values of star-capacitance at a given speed to generate a particular terminal voltage can be obtained experimentally by using a variable capacitor bank.

A comparative study will be treated by using simulation and experiments tests. The dual stator SEIG supplied two individual three-phase resistive loads after switching-in a two star connected capacitor bank. To feed two- independent three-phase loads from dual three-phase generator, three-phase star connected load banks of variable resistance were connected two each three-phase winding set (figure 3).

A detailed study of steady state performance of the dual three-phase SEIG indicates that for different operating conditions such as change in speed and different values star-capacitance. Self-excitation under no-load con-

dition and loading performance under a typical resistive load are elaborated. For simulation of no-load operation,

The two star-capacitor SE-DTPIG needs a minimum value of capacitance to self-excites at no-load. The no-load terminal voltage can be computed for different value of star-capacitances using a computer algorithm for no-load conditions.

With the change in value of excitation capacitance, speed and terminal voltage both change. When the capacity believes, the generator operates more rapidly.

As shown in

Experimental and computed result for variation of terminal voltage and frequency as function of load current are given in

It is well known that for operation in self-excitation mode, the capacitive excitation is necessary to maintain the machine terminal voltage. If the speed is kept constant at

The paper discusses applicability of a dual three-phase capacitor excited asynchronous generator for supplying two individual three-phase loads and for supplying a single three-phase load, by presenting results of a simulation and an experimental study of the steady state behavior for various operating conditions. The proposed method can be easily extended to the analysis of the influence variation of excitation capacity and speed drive on the generator characteristics. Self-excitation and self-regulation under no-load condition and loading performance under a typical resistive load are elaborated. Hence, the dual three-phase SEIG offers an improved reliability, when compared to its three-phase counterpart. Further, it is also shown that the dual three-phase SEIG can be used to supply one or two independent three-phase loads. While the interaction between the two windings is inevitable, variation of the load at one winding changes operating conditions at the other winding. Very good correlation between simulation and experimental results can be observed.

This work was supported by the Arabian Saudi Ministry of Higher Education and Scientific Research and communication technology.