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Rotor is traditionally designed as 'nested loop' a Nested-loop rotor of D-180 prototype BDFIG b Wind turbine system based on BDFIG

Rotor is traditionally designed as 'nested loop' a Nested-loop rotor of D-180 prototype BDFIG b Wind turbine system based on BDFIG

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Article
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The brushless doubly-fed induction generator (BDFIG) has substantial benefits, which make it an attractive alternative as a wind turbine generator. The aim of this work is to present a nodal-based magnetic equivalent circuit (MEC) model of the BDFIG which provides performance characteristics and flux density distributions. The model takes into acco...

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... rotor is traditionally designed as a 'nested loop' [8] ( Fig. 1a), which couples the stator magnetic fields indirectly. The coupling process, which is called 'cross coupling',i s studied in several references such as [4,9]. The number of rotor nests or poles should be equal to the summation of stator windings pole pair numbers to provide indirect coupling between PW and CW magnetic fields [8]. A wind ...
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... fields indirectly. The coupling process, which is called 'cross coupling',i s studied in several references such as [4,9]. The number of rotor nests or poles should be equal to the summation of stator windings pole pair numbers to provide indirect coupling between PW and CW magnetic fields [8]. A wind turbine system based on the BDFIG is shown in Fig. 1b. In the generating mode, the magnitude and frequency of CW excitation voltage depends on the rotor speed. The relation between CW excitation frequency with shaft speed and grid frequency is [7] f c = P r n m /60 − f p ...
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... is shorted. The magnetic characteristics of the stator and rotor cores lie on the linear region of the magnetising curve under this operating condition. The produced torque and the effective value of the PW phase current against rotor speed are measured. The steady-state measured and calculated curves of torque and PW current are compared in Figs. 10a and b, ...
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... measured and calculated curves of the PW current at different rotational speeds are shown in Fig. 10c when the PW voltage is increased to the nominal value, 240 V rms ...
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... These loss components are not modelled in the MEC which result in computational error and the imposed error is increased by deviating from natural speed. However, the calculation error is acceptable for the speed range of interest (n n ± 25%). The computational errors of the EEC and MEC methods in calculation of PW current are shown in Fig. 11 for both operating conditions. The EEC parameters of the test machine are obtained analytically and experimentally as reported in previous publications, for example [12]. Although the MEC model has satisfactory accuracy under linear and saturated conditions, the accuracy of the EEC model decreases with increasing saturation ...
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... to the steady state, where the flux lines have a uniform distribution, the transient response of the MEC model cannot be trusted because of its coarse meshing. The stator windings and rotor loops currents as well as the magnetic field of the stator and rotor teeth in simulation of the MEC model under specified operating conditions are shown in Fig. 12. The flow of two fundamental flux components with different frequencies in stator core and flux density distributions with unequal magnitudes in rotor core sections are evident in this ...
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... steady-state results of the MEC and 2D magneto-dynamic FE models under operating conditions of Fig. 12 are given in Table 3. The comparisons show good agreement between the results and confirm the validity of the modelling approach. ...

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... These are no permanent magnets, high reliability, good grid fault ridethrough capability, and the fractional rating of the power converter [1][2][3]. There have been many accomplishments in the area of modelling and designing the BDFIM [4][5][6][7][8][9][10][11][12][13][14]. In recent years the focus has been on improving the machine efficiency through finding new [8] and optimising existing [9][10][11][12] rotor structures. ...
... Note that Equation (13) exposes a characteristic feature of the magnetic field variation in BDFIM relative to that of an IM. The time-variations of the real and imaginary parts and the absolute value of the selected (radial or tangential) component of B 0 (t) at a certain coordinate and an operating point according to Equation (13) are illustrated in Figure 3, showing how the absolute value of B 0 (t) varies in time. In IM, the latter is constant in time and one would directly use a formula for the effective permeability provided in the literature [18][19][20][21]. ...
... So far we have assumed that the presence of components B p1 and B p2 on the right-hand side of Equations (13) and (14) is explicit, although in fact it requires processing the solution of Equation (11). The procedure proposed here for this purpose in Figure 5 is relatively simple, being based on the Fourier decomposition of the spatial distribution of A 0 in the circumferential direction and interpolation of the variation of the Fourier transform coefficients in the radial direction. ...
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... On the other hand, unlike the subdomain, it responds more flexibly to machine geometry. Examples of this analytical method in the literature are: surface PM machines [13,14], interior PM machines [15][16][17], switched reluctance machines [18], flux-switching PM machine [19], and induction machines [20][21][22]. ...
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... Later to calculate the flux density distribution and analyze the performance characteristics, the node-based MEC is developed for the doubly fed induction generator. 35 In Ref. 34 the authors proposed the mathematical modeling of single-phase shaded pole induction motor using winding function theory and validated the modeling with experimental results. Due to ease of manufacturing and widespread use of tangential rotor-type IPMSM, the authors used MEC to improve the driving torque and torque ripple. ...
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... As mentioned earlier, one branch is assumed between each tooth of the rotor and that of stator. The permeance of the branch between i th stator tooth and j th rotor tooth ( ( , )) depends on the rotor position and can be calculate as [16]: ...
... where , is the overlapping area between stator i th tooth and rotor j th tooth, , is fringing flux permeance in the airgap that is arised from the slotting effect of stator and rotor cores [16]. ...
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... MEC solvers are used to design induction machines 13 and other different types of electrical machines, even in transient simulations. [14][15][16] As shown by Hameyer and Hanitisch, 17 fast MEC solvers are easily embedded in optimisation procedures and even real-time applications. 18 Sizov et al 19 used MEC to model faults in induction motors with good agreement with experiments and FEM. ...
... 13 Another approach includes the use of FEM to determine the air gap reluctance, 22 or to make use of specific equations for the different situations when teeth are overlapping. 16 This article F I G U R E 1 Pie chart with common reasons for downtimes of electrical machines 1,2 investigates an improved analytical expression for the air gap permeance. In this article, furthermore, effects related to eccentric rotor positions are incorporated. ...
... The first method is based on virtual work. 16,21 The second method relies upon the space vector theory. 23 The third method uses the Maxwell stress tensor in a FEM setting. ...
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... The air-gap permeance, ( , ) , depends on the relative position of the stator in relation to the rotor [18]: ...
... where , denotes the common area between the stator i-tooth and the rotor j-tooth and , is the permeance of fringing flux [18]. ...
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