Identifying Harmonics By Empirical Mode Decomposition For Effective Control Of Active Filters During Electric Vehicle Charging

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Identifying Harmonics By Empirical Mode Decomposition For Effective Control Of Active Filters During Electric Vehicle Charging Powered By Docstoc
					                                                 (IJCSIS) International Journal of Computer Science and Information Security,
                                                 Vol. 9, No. 9, September 2011
 
 


 Identifying Harmonics by Empirical Mode
Decomposition for Effective Control of Active
  Filters During Electric Vehicle Charging
                                     B. V. Dhananjay and T. Senthil

                    B.V. Dhananjay,                                             Dr.T.Senthilkumar,
                Research Scholar,                                        Professor, Automobile Engineering,
          Vinayaka Mission’s University,                                     Bharathidhasan University,
                   Salem,India                                                   Trichirapalli, India



Abstract-This paper provides Hilbert Huang                       affecting charging are temperature, state of charge,
Transform(HHT) method (an empirical mode                         plate area, impurities, gassing.
decomposition(EMD)) for identifying the presence of                   Electric vehicles (EV) will become an
harmonics during electric vehicle battery charging               attractive alternative to internal combustion engine
when harmonics are generated into the electric line,
due to switching actions of the power electronics.
                                                                 vehicles in the event that their range can be
Activation of the active filters based on the difference         extended. One way to achieve this in the short term
between load current and fundamental current                     is to provide a fast charger infrastructure. Such a
measured from the line is done. By using active power            structure would provide greater mobility for the EV
filter (APF) injection of the required current to                user, since during short stops (<1 hour) the EV
minimize the harmonics is done. As part of                       batteries could be charged from typically 20 to 80
simulation, the accuracy of the HHT is above 95%.                % of nominal charge. This would significantly
By correctly recognizing the harmonics using HHT                 extend the EV range.Fast charger infrastructure
and injecting the compensating current into the line,            cost is high. Chargers adversely affect the grid
the charging time of the battery can be reduced. The
reduction in the charging time also depends on the
                                                                 power quality due to presence of power electronic
battery condition.                                               loads like diode rectifiers and thyristor bridge
                                                                 converters in the distribution network that result in
      Keywords-Hilbert Huang Transform; active power
                                                                 voltage distortion and current harmonics, (Akagi
filter.                                                          1996).
                                                                      High increase of problems in the electric
                                                                 power distribution networks due to the presence of
                I     INTRODUCTION                               harmonics. Loads that use switching control with
                                                                 semiconductor devices are the main cause. One of
                                                                 the most important tools for correcting the lack of
     The battery is the primary source of electrical             electric power quality are the active power filters
energy. It stores chemicals. Two different types of              (APF), (Udom et al. 2008). The objective of this
lead in an acid mixture react to produce an                      work has been proving that back propagation
electrical pressure. This electrochemical reaction               neural networks, previously trained with a certain
changes chemical energy into electrical energy. A                number of distorted waveforms, are an alternative
battery can be of primary cell, secondary cell, wet              to the rest of the techniques used and proposed at
charged, dry charged and low maintenance type. A                 the present time for controlling the APF's, as the
fully charged battery contains a negative plate of               ones based on the use of the Fast Fourier
sponge lead(Pb), a positive plate of lead                        Transform (FFT). A large number of these control
dioxide(Pbo2) and an electrolyte of sulphuric acid               techniques are based on ANN’s, (Pecharanin et al.
(H2So4) and water (H2o). During charging, sulphate               1994).
leaves the plates and combines with hydrogen(H2)
to become sulphuric acid (H2So4). Free oxygen
combines with lead on the positive plate to form                         II   MATERIALS AND METHODS
lead dioxide. Gassing occurs as the battery nears
full charge and hydrogen bubbles out at the
negative plates, oxygen at the positive. Factors                     A    Materials


                                                                                                                          
 
                                                           109                              http://sites.google.com/site/ijcsis/
                                                                                            ISSN 1947-5500
                                                   (IJCSIS) International Journal of Computer Science and Information Security,
                                                   Vol. 9, No. 9, September 2011
 
 
          Figure 1shows a three-phase diagram of                                              M=
                                                                                                    (a + b)                         (1)
an HHT controlled shunt APF. A load current                                                            2
signal iLis acquiredand used by the ANN to obtain
the distortion current waveform as reference signal                         Where a = Maximum_envelope and b =
for the control of the APF.The power converter                              Minimum_envelope.
injects the necessary compensation current iLin the                4. Obtain a new signal using the following
power circuit, achieving thus a sinusoidal source                     equation:
current.                                                                           h 11 (t) = X(t) − M 11 (t) (2)

                                                                      Where h11(t) is called first IMF. Subsequent
                                                                      IMF’s had to be found if there are some
                                                                      overshoots and undershoots in the IMF. Hence,
                                                                      the envelope mean differs from the true local
                                                                      mean and h11(t) becomes asymmetric.
                                                                           In order to find the additional IMF’s, h11(t)
                                                                  is taken as the new signal. After nth iteration, we
                                                                  have:
                                                                                           h1n (t) = h1(n −1) (t) − M1n (t) (3)

                                                                      Where M1n(t) is the mean envelop after the nth
                                                                      iteration and h1(n-1)(t) is the difference between
                                                                      the signal and the mean envelope at the (k-1)th
                                                                      iteration.
                                                                                                  

                                                                   5. Calculate C2F as follows:
                                                                                                          C2F1 = IMFn               (4)
              Figure 1     APF control using HHT

                                                                     Where     IMFn =    final IMF obtained
       B   Methods                                                                                        C2F2 = IMFn + IMF(n −1)   (5)

Empirical Mode Decomposition (Huang) and                              Similarly,
Hilbert Transform
         A signal can be analyzed in details for its
frequency, amplitude and phase contents by using                                C2Fn = IMFn + IMF(n −1) + ....... + IMF1
                                                                                                                                    (6)
EMD followed by HT (Jayasree et al. 2010 and
Stuti et al. 2009), The EMD produces the mono                          Where C2Fn is the original signal.
components called IMFs from the original signal.
In a given frame of signal, there can be many
IMFs. Each IMF will contain a wave form of                         6. Calculate F2C as follows:
different amplitude. Hilbert Transform is applied                                         F2C1 = IMF1                               (7)
on an IMF to obtain, IF and IA. It is mandatory that
a signal be symmetric regarding the local zero
mean, and should contain same number of extreme                                             F2C 2 = IMF1 + IMF2                     (8)
and zero crossings.
The steps involved in EMD of a signal X(t) with                                             F2C n = IMF1 + IMF2 + ....... + IMFn    (9)
harmonics into a set of IMFs are as follows.

    1. Identify all local maxima of X(t). Connect the                  Where F2Cn is the original signal.
       points using a cubic spline. The interpolated               7. Hilbert transform is applied for each
       curve obtained. The upper line is called the                   IMF and analytical signal is obtained.
       upper envelope (Maximum_envelope).                             A complex signal is obtained from each
    2. Identify all local minima of X(t) connect the
       point using a cubic spline.. The lower line is
                                                                      IMF:
       called         the      lower        envelope                     Analytic(I MF) = real(IMF) + imag(IMF) (10)
       (Minimum_envelope) obtained by cubic spline. 
    3. Compute the average by:


                                                                                                                                           
 
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                                                                                                    ISSN 1947-5500
                                                         (IJCSIS) International Journal of Computer Science and Information Security,
                                                         Vol. 9, No. 9, September 2011
 
 

    8. Instantaneous frequencies are obtained                            a simulation are presented where a step load change
       from analytical signal using                                      occurs at time 60 ms. One additional resistance is
                                                                         connected in parallel with the load, increasing the
       IF =
            0.5 × (angle( − X(t + 1) × conj(X(t − 1))) + π) (11)         total load current.
                           2× π
                                                                                   Figure 4 shows the EMD process. In the
                                                                         sample harmonics signal considered, only one
    9. Instantaneous amplitudes are obtained                             instantaneous mode function is present. A flat
       from the analytical signal using the                              residue signal is also presented. This plot is only
       following                                                         for 1000 samples. This will be repeated for the
                                                                         remaining length of the signal. Figure 5 shows the
                     IA = real(IMF) 2 + imag(IMF) 2 (12)
                                                                         extraction of different signals present from the fine
                                                                         level to coarse level. Similarly, Figure 5 shows the
                                                                         extraction of different signals present from the
                                                                         coarse level to fine level. Figure 7 presents the
           III EXPERIMENTAL SIMULATION                                   instantaneous frequency present in every sample of
                                                                         the signal. Figure 8 presents the instantaneous
                                                                         amplitude present in every sample of the signal.
                                                                         Figure 9 and Figure 10 presents statistical values of
                                                                         instantaneous frequencies and instantaneous
                                                                         amplitudes. Based on the statistical values, the
                                                                         amount of harmonics will be estimated and
                                                                         appropriately, required compensating current will
                                                                         be injected into the line.
                                                                                                                   V     CONCLUSION
                                                                                  A Hilbert Huang Transform method has
                                                                         been used at the control of a shunt active power
                                                                         filter. Based on the amount of harmonics
                                                                         recognition, the APF is activated. By correctly
                                                                         injecting the compensating current into the line, the
                                                                         charging time of the battery can be reduced. The
                                                                         circuit has to be verified with the implementation
                                                                         of HHT in real time for improved charging of the
                                                                         EV battery. The reduction in the charging time also
                                                                         depends on the battery condition.
           Figure 2        Power circuit with HHT controlling
                             active power filter
                                                                                                                                                v=0.1pu,cy=50
         The model of Figure2 has been created                                                                                                  v=0.1pu,cy=50
using Matlab 10. Different sets of parameters have                                           400                                                v=0.1pu,cy=50
                                                                                                                                                v=0.1pu,cy=50
been employed at the power circuit and APF. In
                                                                                             200                                                v=0.1pu,cy=50
most cases the reference current obtained by the
                                                                         V o l ta g e (V )




HHT controller was accurate enough to enable the
                                                                                               0
APF to compensate harmonic distortion. If an
elevated content of high order harmonics were
                                                                                       -200
present in the load current, the HHT controller
helps in obtaining reference signal.                                                   -400
                                                                                          6
System parameter used:                                                                                4                                     1
Power circuit:Phase voltage = 220 VRMS ,                                                                       2                 0.5
Frequency = 50 Hz , Source resistance = 0.1 Ω,                                                                     0 0
                                                                                             Signal patterns
Load resistance = 20 Ω, Load inductance = 30 mH                                                                                Time(Sec)
APF:Vdc = 500 V, R = 10 Ω, L = 30 mH,
Switching frequency = 40 KHz.                                                                      Figure 3            Sample plot of signals for harmonics


             IV RESULTS AND DISCUSSION

         More than 500 different harmonics
waveforms (Figure 3) have been used in HHT
analysis with different load changes.The results of

                                                                                                                                                                 
 
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                                                                                                                              ISSN 1947-5500
                                                                                   (IJCSIS) International Journal of Computer Science and Information Security,
                                                                                   Vol. 9, No. 9, September 2011
 
 
                                            Empirical Mode Decomposition                                                             50.1




         s ig n a l
                                                                                                                                 50.05




                                                                                                    F re q u e n c y s p e c tru m
                                                                                                        In s ta n ta n e u o s
                                                                                                                                      50


                                                                                                                                 49.95
        200
im f1




                0                                                                                                                    49.9


      -200
                                                                                                                                 49.85
                                                                                                                                    0.015               0.02                0.025           0.03                                          0.035               0.04
                                                                                                                                                                                 Time (sec)

        200                                                                                                                                       Figure 7                    Instantaneous frequency
re s .




                0                                                                                                  231.5


      -200
                          0.01      0.02       0.03      0.04     0.05     0.06    0.07
                          Figure 4              Empirical mode decomposition




                                                                                                    Am plitude
                                                                                                                             231
                                                        f2c
             s ig n a l




                                                                                                                   230.5
                                                                                                                      0.015                            0.02               0.025        0.03                                              0.035             0.04
                                                                                                                                                                              Time (sec)

        200                                                                                                                                       Figure 8                    Instantaneous amplitude
f2 c 1




                0                                                                                                              150                                                                                10




                                                                                                                                                                                               S td o f F re q u e n c y
                                                                                                       F re q u e n c y




       -200                                                                                                                    100
                                                                                                        M ean of




                                                                                                                                                                                                                           5
                                                                                                                                     50
        200
s ig n a l




                                                                                                                                      0                                                                                    0
                0                                                                                                                      0          1                2             3                                          0       1               2           3
                                                                                                                                                        Imf                                                                               Imf
       -200
                                                                                                                                                                                                          150
                          0.01       0.02       0.03     0.04     0.05     0.06    0.07                                                                                                                                                  Maximum Frequency
                                                                                                                          1500
                                                                                                                                                                                                                                         Minimum Frequency
                                                                                                    F re q u e n c y




                                                                                                                                                                                           F re q u e n c y


                                                                                                                                                                                                          100
                                                                                                     N o rm o f




                                 Figure 5              Fine to coarse signals                                             1000

                                                                                                                                                                                                                  50
                                                                                                                               500

                                                         c2f                                                                          0                                                                                    0
                                                                                                                                       0          1                2             3                                          0       1               2           3
        200                                                                                                                                             Imf                                                                               Imf
s ig n a l




                0                                                                                                                           Figure 9                   Statistical values of the instantaneous
                                                                                                                                                                               frequencies
       -200
                          0.01       0.02       0.03      0.04     0.05     0.06     0.07
                                                                                                                                                                                                         10
                                                                                                                                 300
                1
                                                                                                                                                                                       A m p litu d e
                                                                                                          A m p litu d e
                                                                                                           M ean of




                                                                                                                                 200
                                                                                                                                                                                         S td o f
     c 2 f1




                0                                                                                                                                                                                               5
                                                                                                                                 100
               -1
                 0        0.01       0.02       0.03     0.04     0.05     0.06    0.07     0.08
                                                                                                                                      0                                                                         0
                                                                                                                                       0          1            2             3                                   0              1               2         3
        500                                                                                                                                                                                                                             Imf
                                                                                                                                                        Imf
s ig n a l




                0
                                                                                                                                                                                                  300
                                                                                                                            4000                                                                                                                Maximum Amplitude
       -500
                                                                                                     A m p litu d e




                                                                                                                                                                                       A m p litu d e




           0              0.01       0.02       0.03     0.04     0.05     0.06    0.07     0.08                                                                                                                                                Minimum Amplitude
                                                                                                      N o rm o f




                                                                                                                                                                                                  200
                                 Figure 6              Coarse to fine signals                                               2000
                                                                                                                                                                                                  100

                                                                                                                                      0                                                                         0
                                                                                                                                       0          1            2             3                                   0              1               2         3
                                                                                                                                                        Imf                                                                             Imf
                                                                                                                                            Figure 10                  Statistical values of the instantaneous
                                                                                                                                                                                amplitudes


                                                                                                                                                                                                                                                            
 
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                                                                                                                                                                                     ISSN 1947-5500
                                                        (IJCSIS) International Journal of Computer Science and Information Security,
                                                        Vol. 9, No. 9, September 2011
 
 
                      REFERENCES

[1]   HAkagi., ”New Trends in Active Filters for Power
      Conditioning”, IEEE Trans. on Industry Applications, vol.
      32, No 6, Dec. 1996, pp 1312-1322.
[2]   TJayasree., DDevaraj., RSukanesh.,”Power quality
      disturbance classification using Hilbert transform and RBF
      networks”, Neurocomputing , Vol 73 Issue 7-9, March,
      2010, pp. 1451-1456.
[3]   NPecharanin., MSone., HMitsui., “An application of
      neural network for harmonic detection in active
      filter”,IEEE World Congress on Computational
      Intelligence.,IEEE International Conference on Neural
      Networks, Vol.6, pp. 3756-3760, 1994.
[4]   StutiShukla, S. Mishra, and BhimSingh,”Empirical-Mode
      Decomposition With Hilbert Transform for Power-Quality
      Assessment”, IEEE transactions on power delivery, Vol.
      24, No. 4, October 2009.
[5]   Udom. Khruathep, SuittichaiPremrudeepreechacharn,
      YuttanaKumsuwan,“Implementation of shunt active power
      filter using source voltage and source current detection”,
      IEEE, pp.2364-2351, 2008.




                                                                                                                                 
 
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