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Analytical Study of Rotor Eccentricity Effects on Brushless Doubly Fed Machines Vibration

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
   
           
        
         
       
 
     

         
      
       
        
      
     
     
        
          
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0<1A83644<08;4B0=01386<08;2<
20=8BF8C 0AF82:0=D502CDA8=6AD?
=8E4AB8C 50AF82:E4=CA  4<08;
A<2<0=F0AF82:02D:
1C08034 8BF8C 0<E4AC428<8C438=6B4364B03
0<1A83644<08;401C0803420<E4AC422D:
       
    


           
I
        
      
  
         

         
    
        
       

     
   H I    
       
>         I
        
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         
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64=4A0CA0=3 BC0=35A<028=4B8348=E4AC4A0=36A83B834
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    I    
         
   
        
   >   
        

       
 
       

    
       
          
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        
      
I      
  
        
      
       
>       
 
       


         
    >
   


       
    
    
      
      

  
         
 
          

       

       
        
       

   
          
    I  

        
        
          
        
        
         
     H    
I   
   

          
         
        
>      
       
      
>         
    >  
       
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        
       
        
       
     
           
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>  
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   
        
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         
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    
    
    
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         
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     >    
          
      
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         

       
      
       
 
         
         
 
         
 
        
       

  
        

  
         
          

B(
θ
,t)=
π
2B1cos( p1
θ
+
ω
1t+
φ
1)+B2cos( p2
θ
+
ω
2t+
φ
2)
1
()

Authorized licensed use limited to: UNIVERSITY OF SOUTHAMPTON. Downloaded on April 29,2021 at 13:22:03 UTC from IEEE Xplore. Restrictions apply.
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         
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         
>       
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       
         
       
    
        
  

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 #$       #%  #  
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   &%&
  

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θ

I
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   



         
     
   %      
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   
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   
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"# ! #%!
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v(
θ
,t)=−K
v
[1
((2 p
1
)
2
1)
2
B
1
2
cos(2 p
1
θ
+2
ω
1
t+2
φ
1
)
+1
((2 p
2
)
2
1)
2
B
2
2
cos(2 p
2
θ
+2
ω
2
t+2
φ
2
)
+2
(( p
1
p
2
)
2
1)
2
B
1
B
2
cos(( p
1
p
2
)
θ
+(
ω
1
ω
2
)t+(
φ
1
φ
2
))
+2
(( p
1
+p
2
)
2
1)
2
B
1
B
2
cos(( p
1
+p
2
)
θ
+(
ω
1
+
ω
2
)t+(
φ
1
+
φ
2
))]
Kv
=3D
a
D
c
3
π
2
64E
ym
μ
0
y
c
3
3
()
B(
θ
,t)=
μ
0
g
1
(
θ
,t)D
a
2J
m
(
θ
,t)d
θ
g
1
(
θ
,t)=g
0
1
+g
s1
1
cos(
θ
+
φ
s1
)+g
d1
1
cos(
θ
+
ω
r
t+
φ
d1
)+...
=g
0
1
1+d
s1
cos(
θ
+
φ
s1
)+d
d1
cos(
θ
+
ω
r
t+
φ
d1
)+...
J
m
(
θ
,t)=ˆ
J
m1
cos( p
1
θ
+
ω
1
t+
φ
1
)+ˆ
J
m2
cos( p
2
θ
+
ω
2
t+
φ
2
)
B
i
=D
a
π
g
0
1
μ
0
p
i
ˆ
J
mi
B
1
B
2
B
1
d
s
1
/2
B
1
d
s
1
/2
B
2
d
s
1/2
B
2
d
s
1/2
B
1
d
d
1/2
B
1
d
d
1/2
B
2
d
d
1/2
B
2
d
d
1/2

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        
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p
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p
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
Authorized licensed use limited to: UNIVERSITY OF SOUTHAMPTON. Downloaded on April 29,2021 at 13:22:03 UTC from IEEE Xplore. Restrictions apply.
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86:0=3C4;03<028=4=C4BCA86
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        

 
>
        
        
          

>

      
         

      
 


   >
       
>         
      

        
>         
        

        

      
      
300 350 400 450 500 550 600 650 700
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4
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8
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Speed (rpm)
Vibration velocity (mm/s rms)

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       
      
        
        

0A?<ACAB?443
1A?<ACAB?443
86 81A0C8=0<?;8CD34B?42CAD<0CC4<028=4B3A8E44=30C:
=;03:0A?<1A?<

        
        
 >
        
          


86<8=0=C5A4@D4=284B8=C4E81A0C8=B?42CAD<A402 B?443C4
380<=3CA80=6;40=3A42C0=6;40A4C45A4@D4=284B5;0A64BCB42=3
;0A64BC0=3C8A3;0A64BC2<?=4=CBA4B?42C8E4;4B;8330B430=3
3CC43;8=4B2AA4B?=3C 


0=3
A4B?42C8E4;
        
    >   
        
        
  
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0 50 100 150 200 250 30
0
Frequency (Hz)
-110
-100
-90
-80
-70
-60
-50
-40
-30
Vibration Amplitude (dB)
48.7 Hz
#2
63.3 Hz
#2
56 Hz
#1
72 Hz
#3
112 Hz
#4
162 Hz
#5
174 Hz
#5
214 Hz
#5
226 Hz
#5 288 Hz
#4
0 50 100 150 200 250 300
Fre
q
uenc
y
(
Hz
)
-100
-80
-60
-40
Vibration Amplitude (dB)
5.3 Hz
#3
68 Hz
#1
63 Hz
#2
136 Hz
#4 142 Hz
#5 186 Hz
#5
206 Hz
#5
210 Hz
#4
250 Hz
#6
73.3 Hz
#2
21.3 Hz
#3
300 350 400 450 500 550 600 650 700
Shaft Speed (rpm)
0
50
100
150
200
250
Frequency (Hz)
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Authorized licensed use limited to: UNIVERSITY OF SOUTHAMPTON. Downloaded on April 29,2021 at 13:22:03 UTC from IEEE Xplore. Restrictions apply.
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... Several experimental BDFMs have been built ranging from small laboratory sizes up to several hundreds of kilowatts including a 250 kW size built by the authors [3], [4] and most recently, an 800 kW machine built for hydropower generation by Chen et al. [5]. Research on the BDFM has gained a fresh momentum in recent years which has led to significant improvement in the understanding, design and control of the machine [6]- [23]. ...
Article
Full-text available
This paper presents a method to estimate the BDFM equivalent circuit rotor current from rotor bar current measurements. Rotor currents are measured using a specially designed hardware that incorporates Rogowski coils and Bluetooth wireless transmission. The measurement of rotor currents enables the parameters in the BDFM's full equivalent circuit to be extracted unambiguously. In particular, stator and rotor leakage inductances can be estimated from experimental tests, which was not possible before from terminal measurement. The method is presented for a nested-loop rotor design and experimental measurements are shown for a prototype D180 frame BDFM.
... Eccentricity measurement is an important and fundamental problem in the field of mechanical engineering [1,2]. This paper is motivated by the automatic eccentricity adjustment of two annular parts during the process of automatic assembly. ...
Article
Full-text available
Eccentricity measurement of annular parts with millimeter scale and micrometer precision requirements is widely used in mechanical engineering applications. To realize accurate eccentricity measurement for large-scaled annular parts, a vision-based and sub-pixel dimensional measurement method is proposed. First, to facilitate the eccentricity measurement, an improved auto focus algorithm is introduced to provide better focused images of the measured parts. Then the traditional Canny operator is modified in gradient direction calculation and a double threshold process to locate the pixel edge more accurately. Next, a model-based sub-pixel edge detection method is studied to extract the sub-pixel edge coordinates. Finally, the eccentricity is calculated according to these sub-pixel edge coordinates. To guarantee measurement accuracy, the pixel equivalent and manual installation error of three degree of freedom (DOF) stages are calibrated, and the verification experiments indicate that the measurement error of the proposed method is better than 1.0 µm.
Article
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This paper studies the unbalanced magnetic pull in the brushless doubly fed machine (BDFM) caused by both static and dynamic rotor eccentricities. Several parallel winding designs for the two stator windings are proposed, and the practicality of such designs is discussed with respect to direct coupling between the stator windings and with rotor undesirable harmonic fields. Once practical parallel winding designs are established, their effects on reducing deflection as a result of static and dynamic eccentricities are shown and compared with series wound stator. This study has been carried out on a prototype D400 250-kW BDFM.
Article
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Because nonmagnetic material is used in the stator, ironless permanent-magnet generators (iPMGs) have negligible normal force between the rotor and the stator, and there is low requirement for the strength of the supporting structures. Therefore, the generator can be light. This feature is attractive in offshore direct-drive energy conversion systems where lightweight design is preferred. The objective of this paper is to investigate systematically different concepts of iPMGs. A design strategy is developed, and codes for finite-element analysis are embedded in this design strategy to ensure the calculation accuracy. A genetic algorithm (GA) is used to find the optimal designs. The influences of machine types and diameter to the machine performances are presented and discussed. Furthermore, the laboratory test of an existing ironless axial-flux permanent-magnet generator confirms the high accuracy of the field and inductance calculations of this design strategy, and the comparison with the parametric study is conducted to demonstrate the excellent performance of the GA used.
Conference Paper
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In this paper some fundamental design issues concerning the brushless doubly-fed reluctance machine are addressed. The literature has several examples of electrical machines with different pole number. It has become apparent that a radially-laminated ducted rotor is a better option. In this paper it is illustrated that the pole number combination should not have pole pair number varying by one, otherwise unbalanced magnetic pull occurs. In addition, it is shown that to reduce voltage ripple due to the interaction of the slotting between the stator slots and rotor ducts, two axial rotor sections can be used with a small degree of skew between them. The example machine design is a 2 MW design as used previously, this has 48 stator slots. The machine results are couched in terms of a 4/8 pole and a 4/6 pole combination (for UMP calculation). Finite element analysis and analytical algorithms are used in the paper.
Article
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This study presents the performance analysis and testing of a 250 kW medium-speed brushless doubly-fed induction generator (DFIG), and its associated power electronics and control systems. The experimental tests confirm the design, and show the system's steady-state and dynamic performance and grid low-voltage ride-through capability. The medium-speed brushless DFIG in combination with a simplified two-stage gearbox promises a low-cost low-maintenance and reliable drivetrain for wind turbine applications.
Article
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The brushless doubly fed induction generator (BDFIG) shows commercial promise for wind power generation due to its lower cost and higher reliability when compared with the conventional DFIG. In the most recent grid codes, wind generators are required to be able to ride through a low-voltage fault and meet the reactive current demand from the grid. A low-voltage ride-through (LVRT) capability is therefore important for wind generators which are integrated into the grid. In this paper, the authors propose a control strategy enabling the BDFIG to successfully ride through a symmetrical voltage dip. The control strategy has been implemented on a 250-kW BDFIG, and the experimental results indicate that the LVRT is possible without a crowbar.
Article
Full-text available
The paper presents a low-cost variable-speed drive system comprising a brushless doubly-fed motor (BDFM) and a fractionally rated unidirectional frequency converter. A simple control algorithm is proposed for regulating the drive's speed and torque. A method of starting the BDFM in the cascade mode is presented and the starting performance is analyzed. The efficiency of the BDFM is discussed and the dynamic performance of the drive is verified by experimental results obtained from a 180 frame-size BDFM. Index Terms—Brushless doubly-fed motor (BDFM), dynamic performance, phase angle controller, unidirectional converter.
Article
The Brushless Doubly-fed Induction Generator (BDFIG) has high potential for wind energy systems, especially for offshore applications where minimum maintenance is vital. The machine low voltage ride through (LVRT) capability in the light of current grid code requirements was investigated using a precise dynamic model. This is particularly important for future multi- MW BDFIGs. This paper shows the necessity for improvements of the BDFIG LVRT capability with presenting a comprehensive analytical study during asymmetrical voltage dips. Analytical studies are conducted to extract a more precise equivalent circuit model of the BDFIG used for analyzing machine dynamic behavior under various fault conditions. In addition, a comparison between different voltage dips is performed to identify critical operating points for LVRT assessment. The results of the study are verified by coupled-circuit model, simulated in MATLAB/Simulink for a BDFIG prototype.
Article
The brushless Doubly-Fed Induction Machine (DFIM) shows great potential as a generator in large-scale wind turbines. The motion of the magnetic field in this machine is not a simple rotation, which makes it not so straight forward to understand its operating principles. This paper develops an analytical magnetic field model for the brushless DFIM that includes the effects of rotor time-harmonics and space-harmonics due to the winding distribution and slotting. By using a case study machine, the developed analytical model is then validated by comparison to FE calculations. Additionally, a two-dimensional spectral analysis is applied to the FE derived radial air-gap magnetic field as a function of time. This analysis verifies the space-time relations of the rotating magnetic field components in the air-gap of the brushless DFIM. Lastly, the developed analytical magnetic field model is used to analyse the brushless DFIM operating principles. The interaction of the stator magnetic field with the rotor nested-loops is explained, as well as the development of electromagnetic torque.
Article
This study investigates modes of vibration in brushless doubly fed machine and brushless doubly fed reluctance machine due to the interaction of its fundamental magnetic fields, via the bending forces they set up in the back iron. It is shown that the presence of two field components of different pole numbers leads to vibration components in addition to those that would be expected in single field machines such as the induction motor. Formulations for the frequencies and magnitudes of the expected vibration components are given and verified experimentally. It is shown that the strength of the vibration components is highly dependent on the choice of pole numbers in the machine, with some much worse than equivalent induction machines and some very similar. The methodology presented enables designers to determine whether their machines are likely to suffer from vibration problems in advance of construction, and to apply remedies where appropriate.
Article
In this paper, a novel brushless doubly-fed machine (BDFM) with the double-sine wound rotor (DSW rotor) for stand-alone ship shaft generator application is designed. The performance studies of the prototype DSW-rotor BDFM with 4 and 2 pole pairs by using the finite element analysis model and the experimental method are presented. The magnetic fields, air-grip flux destiny distribution and the on-load characteristics of the prototype machine are investigated. The experiment results validate the theoretical analysis results and all studies in this paper show that the prototype DSW-rotor BDFM has a good performance.