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SIMULATION OF NOVEL HYBRID SHUNT ACTIVE FILTER TO REDUCE THE HARMONICS DUE TO NON LINEAR LOADS IN 415V, 50Hz DISTRIBUTION SYSTEM

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SIMULATION OF NOVEL HYBRID SHUNT ACTIVE FILTER TO REDUCE THE HARMONICS DUE TO NON LINEAR LOADS IN 415V, 50Hz DISTRIBUTION SYSTEM Powered By Docstoc
					Mr. S. Sellakumar* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES
                                                                                     Vol No. 2, Issue No. 2, 147 - 151




         SIMULATION OF NOVEL HYBRID SHUNT ACTIVE FILTER TO
         REDUCE THE HARMONICS DUE TO NON LINEAR LOADS IN
                  415V, 50Hz DISTRIBUTION SYSTEM
  Mr.S.Sellakumar1                                                            Dr.M.Vijayakumar2
  1                                                                           2
      Research Scholar, Sathyabama University                                     Registrar, JNTU, Anantpur
  sellakumarin@gmail.com                                                      mvk_2004@rediffmail.com
  ABSTRACT
  This paper deals with the hysteresis current                    impedance may occur. Also, the effective
  control based hybrid shunt active filter to                     compensation with the variation of the voltage
  reduce the harmonics produced by non linear                     cannot be carried out with passive filters. The filter
  loads in distribution line. The main harmonic                   performance of shunt active power filter does not
  sources of distribution lines are the non linear                depend on the power system impedance or any
  loads and frequent switching of industrial                      other constant parameters. The compensation of




                                                                            T
  loads.     The     non     linear  loads     take               harmonic and reactive power can be achieved
  discontinuous current and thus it injects                       dynamically in the case of APF. The research in
  harmonics. The switching of loads produces                      this field has been done for many years and
  voltage sag and swells which leads to                           researchers proposed several methods of
  harmonics in the lines. The proposed hybrid                     improving THD value up to 4% by eliminating
  shunt active filter is fully characterized by                   harmonics selectively or reducing it by using
  series LC and shunt DC link connectedES                         different filtering techniques in the active filters.
  through 3-phase active filter. The disturbances                 The References papers have reported field test
  in the supply voltage and load current due to                   results of active filters intended for installation on
  the non linear loads such as rectifiers and                     power distribution systems. The active filter is
  converters are observed in the simulation. The                  characterized by behaving like a resistor for
  same is studied after connecting the designed                   harmonic frequencies, resulting in damping out
  active filter to the line. The simulation results               the harmonic amplification throughout a
  obtained from the proposed method proves                        distribution line. Since the proposed distribution
  that it gives comparatively better THD value.                   system consists of four distribution lines, installing
  KEYWORDS— Hysteresis Current Control [HCC],                     the active filter on the end bus of each line is
  Active Power Filter [APF], Distributed Generators               effective in harmonic damping.
  [DG], Distribution Systems [DS], shunt active filters,          II. HYBRID ACTIVE FILTER FOR A DS’
                     A
  Voltage Regulation [VR] and Total Harmonic
  Distortion [THD]
  I. INTRODUCTION
  The distribution system supplies power to different
  types of industrial loads. The speed control of
  industrial load is made simpler using the power
  electronic converters. But as a counter effect they
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  all inject the harmonic and hence its pollution and
  reactive power in the power system are the                      Fig1: one line diagram of typical DS with active filter
  important power quality problems. With the
  proliferation of non-linear loads in industrial                 A. Harmonics
  applications and frequent switching of loads in the             The Inductor in the fig 1 is the resultant of a
  distribution systems, the compensation of                       leakage inductance of a distribution transformer to
  harmonic and reactive power is becoming                         line inductances. The Capacitors are the PFC
  increasingly concerned. The filters are designed                capacitors installed by consumers. It is observed
  not only to reduce the harmonics also to supply                 that the fifth and seventh harmonic voltages
  the reactive power requirement so that the power                present in the system. The “harmonic
  factor and power quality can be improved. In this               amplification” is resulting from resonance between
  contest the design of filters and their dynamic                 the inductance and the capacitance on the line
  behaviour have been widely discussed. However,                  and its effect is more during day time compared to
  the performances of the filters are very sensitive              night time. The shunt active filter for damping out
  to the power system impedance and series or                     harmonic propagation is connected to a
  parallel resonance with the power system                        distribution system. Fig. 2 shows the simplified



  ISSN: 2230-7818                  @ 2011 http://www.ijaest.iserp.org. All rights Reserved.                         Page 147
Mr. S. Sellakumar* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES
                                                                                     Vol No. 2, Issue No. 2, 147 - 151




  Distribution System having a shunt hybrid active                                           value, the hybrid filter can damp out harmonic
  filter proposed in this paper. The transformer in                                          propagation effectively.
  the pure filter is replaced by a capacitor in the                                          III. EXPERIMENTAL SYSTEM [proposed]
  hybrid filter. The purpose of the capacitor is to
  impose high impedance to the fundamental
  frequency so that the fundamental voltage
  appears exclusively across the capacitor. This
  means that no fundamental voltage is applied
  across the active filter.




                                                                                             Fig 3: Single line diagram of experimental system
                                                                                                      In the experimental the harmonics are




                                                                                                          T
                                                                                             generated either by switching the load frequently
                                                                                             or by connecting a non linear load. A three-phase
                                                                                             power distribution feeder simulator rated at 230 V,
                                                                                             50 Hz, and 20 kW is used for the laboratory
  Fig1: 3 Ф DS with Hybrid Active Filter                                                     experiments. Table I summarizes the line
  Fig 2 shows the detailed power circuit of the                                              simulator parameters. When a lossless line is
  hybrid filter, which consists of a three-phase                                             assumed, the characteristic impedance of the
  voltage-fed PWM inverter and [switches are
  named as per their conduction sequence] a series
  connection of L and C per phase. Note that the
  tuned frequency of L and C is not the fifth-
  harmonic frequency but around the seventh-
  harmonic frequency. The reason is that the
  seventh-tuned LC filter is less bulky than the fifth-
                                                             ES                              feeder simulator Zo can be calculated as
                                                                                             Zo=sqrt(L/C) ------------------------------------------- (2)
                                                                                             A shunt hybrid active filter component values
                                                                                             given in the table – II is connected to the bus. The
                                                                                             dc-bus voltage of the PWM inverter is controlled
                                                                                             to be 40 V. Note that the dc-bus voltage as low as
                                                                                             40 V in the 230-V system corresponds to a dc-bus
  tuned LC filter as long as both filters have the                                           voltage as low as 1.3 kV. This means that
  same inductor as L. The dc-bus of the PWM                                                  adopting a diode-clamped three-level inverter
  inverter has only a capacitor without external                                             allows us to use 1200-V IGBTs that are easily
  supply, and the dc-bus voltage is controlled by the                                        available on the market at low cost. Referring to
                              A
  hybrid filter. The hybrid filter is controlled so as to                                    [7], the control gain Kv should be set to the
  draw the compensating current ic from the                                                  inverse of the characteristic impedance of the
  distribution line.                                                                         feeder.
  B. Operating Principle                                                                     C. IEEE STANDARD OF VOLTAGE DISTORTION
  The compensating current of the hybrid shunt                                               LIMITS
  active filter consists of a fundamental component                                                                       Voltage
  and harmonic components and they are                                                               Bus Voltage                            THD (%)
                                                                                                                          Distortion
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  determined by the impedance of the LC filter and                                              [less than or equal
  are controlled by the active filter. Three-phase                                                                  3.0   5.0
                                                                                                       69 kV]
  voltages and currents are detected at the
  installation bus. The harmonic voltage Vh in each
                                                                                               69.0001 kV - 161 kV  1.5   2.5
  phase is extracted from the detected three-phase                                                 > 161.001 kV     1.0   1.5
  voltage, and then the harmonic voltage is                                                  D. NON-LINEAR LOAD HARMONIC CURRENT
  amplified by a control gain Kv. Thus the harmonic                                          SPECTRUM Ih / I1
  current reference ich is given by
  ich = Kv*Vh ------------------------------------------------------------------------ (1)   HARMONI
                                                                                                            3       5      7       9      11       13       15
  The actual harmonic compensating current ich is                                            C ORDER
  extracted from the detected compensating current                                              PC        0.81     0.53   0.25    0.09   0.05     0.04      0.03
  ic. Assuming that it is equal to its reference ich, the
                                                                                                                                                            0.00
  hybrid filter behaves as a damping resistor of1/Kv                                          Flu.light   0.16     0.08   0.029   0.02   0.014    0.008
                                                                                                                                                              4
  [V/A] for harmonic frequencies. The optimal value
  of Kv is equal to the inverse of the characteristic                                           ASD                0.17   0.111          0.045    0.029
  impedance of the distribution feeder. With this




  ISSN: 2230-7818                                      @ 2011 http://www.ijaest.iserp.org. All rights Reserved.                                  Page 148
Mr. S. Sellakumar* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES
                                                                                     Vol No. 2, Issue No. 2, 147 - 151




  III. HCC PRINCIPLE                                              i3a=                        ---------------------------           (4)
                                                                  When the bidirectional switch Sa is on, the
                                                                  corresponding equation is
                                                                  L                            --------------------------            (5)
                                                                  Since the phase a current ia rises from (irefa –0.5Iw)
                                                                  to (irefa + 0.5Iw) within time t1, hence (5) can be
                                                                  expressed as
                                                                  L                       ---------------------------- (6)
                                                                  From (6) t1 can be expressed as             t1 =
                                                                                                                 ---- (7)
                                                                  When bidirectional switch Sa is switched off and
                                                                  diode D1 is on, phase a current ia falls from irefa +
                                                                  0.5 Iw to irefa – 0.5Iw within the transit time t2
  The bidirectional switches shown in Fig. 2 are




                                                                               T
                                                                  L          - 0.5Vdc -------------------------------- (8)
  controlled with hysteresis current control
  technique. In the balanced three phase system                   From (8) t2=                        ----------------------         (9)
  and unity power factor operation, the three-phase               But 0.5Vdc > va. Substituting (7) and (9) in (3)
  voltages and reference currents are equal in                    i1a=        irefa ----------------------------------------- (10)
  magnitude and displaced by 1200. The switches
  S1, S3, and S5 conduct when corresponding Phase                 B. Operation during the Negative Interval of
                                       ES
  voltage is in positive half cycle and the
  bidirectional switch is in the switch-off state.
  Similarly, switches S4, S6, and S2 conduct when
  corresponding phase voltage is in negative half
  cycle and the bidirectional switch is in the switch-
  off state. In order to prove the instantaneous
  power balance between ac source and dc bus, the
                                                                  irefa
                                                                           During this condition, the phase a voltage
                                                                  is in negative half cycle and the Switch S1 is
                                                                  reverse-biased and the phase a current will flow
                                                                  through Switch S4.It is similar to the operation of
                                                                  positive interval of irefa.
                                                                  Similar to expression (10), i2a is also calculated as
  local average method is adopted [5]–[6]. In fig 4,              i2a=        irefa ------------------------------------------- (11)
  phase a current ia is controlled to track the                   Similarly the phase b and phase c currents can be
  reference current within the window width Iw and                obtained as
  same way the other two phases are carried out.
                    A
  Fig 4.Currents within one switching period                             1b                                                 ---- (12)
            The phase a current being switched
  between upper and lower bounds to track the
  reference current(upper trace); Switch S1 current                      2b                                                 ---- (13 )
  (mid-trace);bidirectional switch Sa current (lower
  trace) in the balanced three phase system and
  unity power factor operation.                                                                                             ---- (14)
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                                                                         1c
  A. Operation during the Positive Interval of irefa:
            It is explained by taking phase “a”
  parameters and the other phase parameters are                          2c                                                  ----   (15)
  assumed to be same. During 0<t<t1, the supply
  current ia flows through the bidirectional switch Sa,           The sum of the upper diode currents i1a, 1b, 1c
  rising from (irefa - 0.5Iw) to (irefa +0.5Iw) and during        gives the upper dc link currents i1 and the sum of
  t1<t< (t1+t2), the switch Sa is off and the currents in         the lower diode currents i2a, 2b, 2c gives the lower
  the input inductor continues to flow through the                dc link currents.
  freewheeling diode D1.It is assumed that the time               The total instantaneous dc power pdc is
  period (t1+t2) is so concise that irefa is considerably
  constant. From fig.3 Let i1a be the current flowing             pdc =                   = va irefa + vb irefb + vc irefc ------ (16)
  through the upper switch S1 and i3a be the current              Without considering the losses for a balanced
  flowing through the bidirectional switch Sa. The                three phase system with unity power the
  average currents i1a and i3a are                                instantaneous power can be expressed as
                                                                  pdc = 3Vp I ref = pac ---------------------------- (17)
  i 1a=              dt ≈           --------------   (3)




  ISSN: 2230-7818                  @ 2011 http://www.ijaest.iserp.org. All rights Reserved.                                    Page 149
Mr. S. Sellakumar* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES
                                                                                     Vol No. 2, Issue No. 2, 147 - 151




  The reference supply current under unity power                        The above diagram shows the switching pulses
  factor can be obtained as                                             produced by the HCC for the switches of active
                                                                        filter.
  i ref =       Idc        --------------------------------- (18)
                                                                        The THD value without filter is 22.91%. The large
  Thus whenever there is any variation on the load                      amount of harmonics in the distribution line
  the reference current can be adjusted by the                          produces high value of THD. This value may vary
  output power estimator and dc link voltage                            time to time due to switching of new loads and
  regulator, the ac side neutral current in1 can be                     their types. Hence a dynamic filtering system is
  zero in magnitude and expressed as                                    required to reduce the harmonics.
  in1= √2Iref [sinωt + sin (ωt -       ) +sin(ωt +       )]-(19)
  Substituting iref in i1 and i2 and summing them the
  injection current in2 is obtained. Thus in2 consists of
  the sum of the currents through three bidirectional
  switches, and is given as
  in2 = i2 – i1 =     sin (3ωt)        --------------------- (20)




                                                                                  T
  Thus the expressions 18, 19 and 20 are used to
  calculate the amount of current to be injected in
  order to minimize the harmonics. The same can
  be implemented in simulation model.
  IV. SIMULATION RESULTS
                                              ES
  The distribution line currents are observed and it
  has deteriorated from its sinusoidal.
                        A
                                                                        The HCC based hybrid shunt active filter is connected
                                                                        to the distribution system and simulated. The THD
                                                                        value has reduced to as low as 3.46%.
IJ

  These are the filter currents injected in to the line
  to compensate the harmonics.




  ISSN: 2230-7818                        @ 2011 http://www.ijaest.iserp.org. All rights Reserved.                   Page 150
Mr. S. Sellakumar* et al. / (IJAEST) INTERNATIONAL JOURNAL OF ADVANCED ENGINEERING SCIENCES AND TECHNOLOGIES
                                                                                     Vol No. 2, Issue No. 2, 147 - 151




                  Typical Circuit diagram of HCC Based Active filter for Distribution System




                                                                                T
  V. CONCLUSIONS
  The harmonic pollutions in the 415V, 50Hz
                                           ES
  distribution system due non linear loads and the
  switching of industrial loads are analysed with the
  simulation and measured results. The HCC
                                                                       [5]. B. R. Lin, “High power factor AC/DC/AC converter
                                                                      with random PWM,” IEEE Trans. Aerosp. Electron.
                                                                      Syst., vol. 35, no. 2, pp. 935–944, Jul. 1999
                                                                      [6].     Norikazu Kanao, Member, IEEE, Mitsunori
                                                                      Yamashita, Hikoni Yanagida, Munehisa Mizukami,
                                                                      Yasuhiro Hayashi, Member, IEEE, and Junya Matsuki,
  principle and its implementation are explained                      Member, IEEE “Power System Harmonic Analysis
  with mathematical proof. The dynamically                            Using State-Estimation Method for Japanese Field
  produced triggering pulses for the hybrid shunt                     Data” IEEE transactions on power delivery, vol. 20, no.
  active power filter fetches good results for this                   2, April 2005
  method. The results of this method can be                                       S.Sellakumar was born in Tamilnadu
                      A
  validated and it will be the future scope of this                               India, on June 25, 1978. He received
  study.                                                                          the B.E (first class) from University of
  IX.REFERENCES                                                                   Madras, M.E (First class with
    [1]. Experimental Study and Comparison of Hybrid                              honours)         from      Sathyabama
  Active Filter with Parallel Active Filter, Xiao Xiangning,                      University. Currently he is doing
  Xu Yonghai, Liu Hao, Ma Yulong Department of                        research in harmonics in the power system due to
  Electrical Engineering, North China Electric Power                  non linear loads and working as Assistant
IJ

  University, Beijing China 102206                                    Professor in Jeppiaar Engineering College,
  [2]. Power System Harmonic Analysis Using State-
  Estimation Method for Japanese Field Data, Norikazu
                                                                      Chennai, India. His research interests include
  Kanao, Member, IEEE, Mitsunori Yamashita, Hikoni                    power electronics, active filtering, and control
  Yanagida, Munehisa Mizukami, Yasuhiro Hayashi,                      systems.
  Member, IEEE, and Junya Matsuki, Member, IEEE                                   Dr.M.Vijayakumar, Graduated from
  TRANSACTIONS ON POWER DELIVERY, VOL. 20, NO. 2, APRIL                           NBKR Institute of Science and
  2005
  [3]. Natchpong Hatti, Student Member, IEEE, Kazunori
                                                                                  Technology, Vidyanagar, A.P, India
  Hasegawa, and Hirofumi Akagi, Fellow, IEEE “A 6.6-kV                            1988. He obtained M.Tech Degree
  Transformerless Motor Drive Using a Five-Level Diode-                           from Regional Engineering College,
  Clamped PWM Inverter for Energy Savings of Pumps                    Warangal, India in 1990. He received Doctoral
  and Blowers” IEEE Transactions on power electronics,                Degree from JNT University Hyderabad, India in
  vol. 24, no. 3, march 2009[4]. Ali I. Maswood, Senior               2000. 1 Ph.D is awarded under his guidance and
  Member, IEEE, and Fangrui Liu, Student Member,                      guiding 6 Ph.Ds at present. He is the recipient of
  IEEE “A Unity Power Factor Front-End Rectifier with                 “Pandit Madan Mohan Malaviya” memorial
  Hysteresis Current Control” IEEE trans. on energy                   prize. Currently he is the Registrar of JNTU
  conversion, vol. 21, no. 1, march 2006
                                                                      Anantapur University, Anantapur



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DOCUMENT INFO
Description: This paper deals with the hysteresis current control based hybrid shunt active filter to reduce the harmonics produced by non linear loads in distribution line. The main harmonic sources of distribution lines are the non linear loads and frequent switching of industrial loads. The non linear loads take discontinuous current and thus it injects harmonics. The switching of loads produces voltage sag and swells which leads to harmonics in the lines. The proposed hybrid shunt active filter is fully characterized by series LC and shunt DC link connected through 3-phase active filter. The disturbances in the supply voltage and load current due to the non linear loads such as rectifiers and converters are observed in the simulation. The same is studied after connecting the designed active filter to the line. The simulation results obtained from the proposed method proves that it gives comparatively better THD value