PI with Fuzzy Logic Controller based APLC for compensating harmonic and reactive power
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PI with Fuzzy Logic Controller based APLC for compensating harmonic and reactive power

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This article explores design and analysis of ...

This article explores design and analysis of
proportional integrator (PI) along with Fuzzy Logic controller
(FLC) based Shunt active power line conditioners (APLC) for
compensating reactive power and harmonic currents drawn
by the load. The aim is to study different control strategies for
real time compensating current harmonics at different power
conditions. The compensation process is based on calculation
of unit sine vector and reduces the dc capacitor ripple voltage
of the PWM-VSI by using PI with fuzzy logic controller. The
switching is done according to gating signals obtained from
hysteresis band current controller and capacitor voltage is
continuously maintained constant. The shunt APLC is
investigated through Matlab/Simulink simulation under
different steady state and transient conditions using PI, FLC
and PI with FLC. The results demonstrate that combination
of PI with FLC is a better solution that reduces the settling
time of the DC capacitor, suppresses harmonics and reactive
power in the load current(s)

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PI with Fuzzy Logic Controller based APLC for compensating harmonic and reactive power PI with Fuzzy Logic Controller based APLC for compensating harmonic and reactive power Document Transcript

  • ACEEE Int. J. on Control System and Instrumentation, Vol. 02, No. 02, June 2011 PI with Fuzzy Logic Controller based APLC for compensating harmonic and reactive power Karuppanan P and Kamala Kanta Mahapatra National Institute of Technology-Rourkela, India-769008 Email: karuppanan1982@gmail.com, kmaha2@refiffmail.comAbstract— This article explores design and analysis of APFs are superior to passive filters in terms of filteringproportional integrator (PI) along with Fuzzy Logic controller characteristics and improve the system stability by removing(FLC) based Shunt active power line conditioners (APLC) for resonance related problems [4]. In particular, recent remarkablecompensating reactive power and harmonic currents drawn progress in the capacity and switching speed of powerby the load. The aim is to study different control strategies for semiconductor devices such as insulated-gate bipolarreal time compensating current harmonics at different power transistors (IGBTs) has spurred interest in active filters forconditions. The compensation process is based on calculationof unit sine vector and reduces the dc capacitor ripple voltage power conditioning [5-6]. This research paper describes of aof the PWM-VSI by using PI with fuzzy logic controller. The novel controller that uses PI along with Fuzzy logic controllerswitching is done according to gating signals obtained from for APLC. This computed sensing source voltage is activatedhysteresis band current controller and capacitor voltage is unit sine vector calculation to generate reference currents.continuously maintained constant. The shunt APLC is The PWM-VSI inverter ripple voltage (dc side capacitor) isinvestigated through Matlab/Simulink simulation under reduced using Proportional Integrated controller as well asdifferent steady state and transient conditions using PI, FLC Fuzzy logic controller. A hysteresis current controllerand PI with FLC. The results demonstrate that combination generates switching signals for the APLC to follow theof PI with FLC is a better solution that reduces the settling reference currents and actual sensing current within specifiedtime of the DC capacitor, suppresses harmonics and reactivepower in the load current(s). band-limits. The shunt APLC is investigated under different steady state and transient conditions and found to beIndex Terms— Shunt Active Power Line Conditioners (APLC), effective for power factor correction and reduces ripplePI controller, Fuzzy Logic Controller (FLC), Harmonics, voltage with the proposed PI with Fuzzy logic controller.Hysteresis Current Controller (HCC) II.DESIGN OF SHUNT APLC I. INTRODUCTION The basic compensation principle of shunt APLC or The ac power supply feeds different kind of linear and active filter is controlled to draw/supply compensating currentnon-linear loads. The non-linear type of loads produces from/to the utility. So that it cancels a current harmonic onharmonics [1]. The reactive power and harmonics cause poor the AC side and makes the source current in phase with thepower factor and distort the supply voltage at the common source voltage. A shunt active filter is connected to the supplycoupling point. This distortion is mainly induced by the line through filter inductances and operates as a closed loopimpedance or the distribution transformer leakage controlled current source shown in fig 1. The output voltageinductance. Passive L-C filters were used to compensate the of the inverter is controlled with respect to the voltage at thelagging power factor of the reactive load, but due to the point of common coupling (PCC). The design of APLCdrawbacks as resonance, size, weight, etc., the alternative containing the following parameters;solution came up, an APLC that provides an effective solution A. Source current:for harmonic elimination and reactive power compensation[2]. The controller is the heart of the active power filter and a The instantaneous current supplied by the source, beforelot of research is being conducted in recent years. compensation and it can be written asConventional PI voltage and current controllers have beenused to control the harmonic current and dc voltage of the is (t )  iL (t )  ic (t ) (1)shunt APLC. Recently, fuzzy logic controllers (FLC) are used Source voltage is given byin power electronic system and drive applications [3]. This vs (t )  Vm sin t (2)paper combines these two techniques for efficient line If a nonlinear load is applied, then the load current will haveconditioners. APLCs are inverter circuits, comprising active a fundamental component and harmonic components, whichdevices such as semiconductor switches can be controlled can be represented asas harmonic current or voltage generators. Differenttopologies and control techniques have been proposed for their implementation. i L (t )  I n 1 n sin(nt  n ) (3) 29© 2011 ACEEEDOI: 01.IJCSI.02.02.109
  • ACEEE Int. J. on Control System and Instrumentation, Vol. 02, No. 02, June 2011 Fig 1 PI with Fuzzy Logic Controller based shunt Active Power Line Conditioners systemThe instantaneous load power can be written as B. Design of DC side capacitor: The DC side capacitor is maintain a DC voltage withpL (t )  is (t ) * vs (t ) small ripple in steady state and energy storage element to  Vm sin 2 t * cos 1  Vm I1 sin t * cos t * sin 1 supply real power difference between load and source during the transient period. The real/reactive power injection may     Vm sin t *    I n sin(nt   n )   result in the ripple voltage of DC capacitor. The selection of CDC can be governed by reducing the voltage ripple. The  n2   p f (t )  pr (t )  ph (t ) ( 4) specification of peak to peak voltage ripple and the rated filter current define the capacitor [2]   I c1, ratedFrom the equation the load current should contain real or C DC  (10)fundamental power, reactive power and harmonic power. The 3Vdr , p  p (max)real power drawn by the load is C. Design of filter LC and reference voltage: 2p f (t )  Vm I1 sin t * cos 1  vs (t ) * is (t ) (5) The design of the filter inductance (LC) and reference voltage (VDC,ref) components is based on the followingFrom this equation the source current supplied by the source, assumption; (1) The AC source voltage is sinusoidal (2) Toafter compensation is design LC the AC side line current distortion is assumed to be p f (t ) 5%. (3) Fixed capability of reactive power compensation ofis ( t )   I1 cos 1 sin  t  I sm sin  t (6) the active filter. (4) The PWM converter is assumed to operate v s (t ) in the linear modulation index (i.e. 0  ma  1) .where, I sm  I1 cos1 (7) III. PROPOSED CONTROL SCHEMEThe total peak current supplied by the source is The proposed control system consists of referenceI sp  I sm  I sl (8 ) current control strategy and PWM control method ofIf the active filter provides the total reactive and harmonic hysteresis current modulator.power, then is(t) will be in phase with the utility voltage and A. Reference current control strategy:purely sinusoidal. At this time, the active filter must providethe following compensation current as The peak value of the reference current I sp can be ic (t )  iL (t )  is (t ) (9) estimated by controlling the DC side capacitor voltage. The DC side capacitor voltage effectively controlled by 30© 2011 ACEEEDOI: 01.IJCSI.02.02.109
  • ACEEE Int. J. on Control System and Instrumentation, Vol. 02, No. 02, June 2011the combination of PI with FLC. The desired reference source where, K P is the proportional constant [=0.3] that determinescurrents, after compensation, can be given the dynamic response of the DC-bus voltage control and isa *  I sp sin t (11) K I is the integration constant [=15] that determines it’s s 0 isb *  I sp sin(t  120 ) (12) settling time. The PI controller output having certain ripple voltage, so as well as need another process to reduce the isc *  I sp sin(t  120 0 ) (13) ripple; the FLC controller connected together with PI controller for rectify the ripple voltage problems.I sp  I sm  I sl the amplitude of the desired source currentand the phase angle is can be obtained from the sourcevoltages. The capacitor voltage is compared with referencevalue and the error is processed in the PI with fuzzy controllershown in fig 2. The output of the fuzzy controller has beenconsidered as the amplitude of the desired source current.The reference currents are estimated by multiplying this peakvalue with the unit sine vectors in phase with the sourcevoltages.Unit sine vector: Fig 3 fuzzy logic Control block diagram The source voltages are converted to the unit current(s) Fuzzy logic controller block diagram shown in fig 3, iswhile corresponding phase angles are maintained. The unit derived the transition between membership and noncurrent is defined as membership can be gradual. The PI controller output error isia  sin t , ib  sin(t  1200 ) and ic  sin(t  1200 ) used as inputs for fuzzy processing. The output of the fuzzyThe amplitude of the sine current is unit or 1 volt and controller after a limit is considered as the magnitude of peakfrequency is in phase with the source voltages. This unit reference current I sp .current multiplies with peak value of fuzzy logic output for Fuzzification:generate the reference current. In a control system, error between reference and output canPI with Fuzzy controller: be labeled as zero (ZE), positive small (PS), negative small (NS), positive medium (PM), negative medium (NM), positive big (PB), negative big (NB). The process of converting a numerical variable (real number) convert to a linguistic variable is called fuzzification. Rule Elevator: The basic fuzzy set operations needed for evaluation of fuzzy rules are AND() , OR  and NOT () AND -Intersection:  A B  min[ A ( X ),  B ( x)] OR -Union:  A B  max[ A ( X ),  B ( x)] NOT -Complement:  A  1   A ( x ) Defuzzification: The rules of FLC generate required output in a linguistic variable (Fuzzy Number), according to real world requirements, linguistic variables have to be transformed to crisp output Fig 2 PI with fuzzy logic Controlerl block diagram (Real number). Figure 3 shows the block diagram of the proposed PI withfuzzy logic control scheme of an APLC. The DC side capacitor Database:voltage is sensed and filtered using Butterworth low pass The Database stores the definition of the membershipfilter (LPF) at 50 HZ. This LPF output voltage compared with function required by fuzzifier and defuzzifiera reference value. The error e  Vdc,ref  Vdc at the Rule Base: The Rule base stores the linguistic control rules required bynthsampling instant is used as input for PI controller. PI rule evaluator, the rules used in this paper in table 1.controller used to control the PWM-VSI of dc side capacitorvoltage. Its transfer function can be represented as H (s)  K P  K I / s (14) 31© 2011 ACEEEDOI: 01.IJCSI.02.02.109 View slide
  • ACEEE Int. J. on Control System and Instrumentation, Vol. 02, No. 02, June 2011 TABLE 1 RULE BASE TABLEB) Hysteresis Band Current Control: Hysteresis current control is the easiest control methodto implement [5]. A hysteresis current controller is implementedwith a closed loop control system. An error signal, e(t), isused to control the switches in an inverter. This error is thedifference between the desired current, iref(t), and the currentbeing injected by the inverter, iactual(t). When the error reachesan upper limit, the transistors are switched to force the currentdown. When the error reaches a lower limit the current isforced to increase. The range of the error signal, emax – emin,directly controls the amount of ripple in the output current Fig.4 PI with Fuzzy logic controller based simulation results forfrom the PWM-voltage source inverter. three-phase active-power-filter under the steady state condition (a) Source current after APF, (b) Load currents, (c)Reference currents IV. SIMULATION RESULT AND ANALYSIS by the Fuzzy logic algorithm, (d) Compensation current by APF and (e) source voltage per current for unity power factor The SIMULINK toolbox in the MATLAB software in First for simulation time T=0 to T=0.4s with load of rectifierorder to model and test the system under steady state and with R L load of 20 ohms and 200 mH respectively and aftertransient conditions using PI, fuzzy logic and combination of the R L load of 10 ohms and 100 mH change for transientPI with fuzzy logic controllers. The system parameters values condition. The transient simulation waveforms are verifiedare; source voltage (Vs) is 230 Vrms, System frequency (f) is similar to steady state waveforms shown in fig 5.50 Hz, Source impedance of RS, LS is 1 Ω; 0.2 mH respectively,Filter impedance of Rc, Lc is 1 Ω; 2.5 mH, Load impedance ofRL, LL of diode rectifier RL load in Steady state: 20 Ω; 200 mHand Transient: 10 Ω; 100 mH respectively, DC link capacitance(CDC) is 1600µF, Reference Voltage (VDC) is 400V and Powerdevices build by IGBT/Diode.PI with Fuzzy controller PI with Fuzzy logic controller based APLC systemcomprises of a three-phase source, a nonlinear load (six pulsediode rectifier RL load) and a PWM voltage source inverterwith a dc capacitor. The simulation time T=0 to T=0.4s with Fig.5 PI with Fuzzy logic controller based simulation results forload of diode rectifier R L load parameter values of 20 ohms three-phase active-power-filter under the transient condition (a)and 200 mH respectively. The source current after Source current after APF, (b) Load currents and (c) Compensationcompensation is presented in fig. 4 (a) that indicates the current by APFcurrent becomes sinusoidal. The load current is shown in The DC side capacitor voltage effectively controlled by(b). The actual reference currents for phase (a) are shown in the PI or FLC and/or combination of PI with FLC shown in figfig. 4(c). This wave is obtained from our proposed controller. 6.The APLC supplies the compensating current that is shownin Fig. 4(d). The current after compensation is as shown in (a)which would have taken a shape as shown in (b) withoutAPLC. It is clearly visible that this waveform is sinusoidalwith some high frequency ripples. We have additionallyachieved power factor correction as shown in Fig. 4(e), phase(a) voltage and current are in phase. Fig.6 simulation results for three-phase active-power-filter under the steady state condition of DC side capacitor voltage controlled by (a) PI controller (b) FLC controller (c) PI with FLC controller 32© 2011 ACEEEDOI: 01.IJCSI.02.02.109 View slide
  • ACEEE Int. J. on Control System and Instrumentation, Vol. 02, No. 02, June 2011The summarized PWM- voltage source inverter of DC side The total harmonic distortion (THD) measured of acapacitance voltage (Vdc) settling time measurement in periodic distorted signal. The analysis of the shunt APLCtransient and steady state conditions using different brings the THD of the source current is less than 5% intocontroller as shown in table 2 compliance with IEEE-519 standards, shown in table 4. TABLE 2 VDC SETTLING TIME USING PI, FLC AND PI WITH FLC CONTROLLER TABLE 4 THD MEASUREMENT USING PI, FLC AND PI WITH FLC CONTROLLER The active power and reactive power are calculated byaveraging the voltage-current product with a running averagewindow over one cycle of the fundamental frequency, shownin fig 7 V. CONCLUSIONS Proportional-Integral with fuzzy logic controller based Shunt APLC performs quite well and it reduces harmonics and reactive power components. Simulation results demonstrate that source current after compensation is sinusoidal and in phase with source voltage. The compensation process is designed based on calculation of unit sine vector and it also reduces the ripple voltage of the dc capacitor of the PWM-voltage source inverter. The PI, FLC and PI with FLC-controllers are investigated under both Fig.7 simulation results for three-phase active-power-filter under the steady state condition of real and reactive power analysis for steady state and transient conditions and it is observed that power quality improvements by different controller (a) PI PI with FLC-controllers provides superior performance in controller (b) FLC controller (c) PI with FLC controller terms of compensation and settling time compared to other The PI with fuzzy logic controller based APLC system methods. The APLC is in compliance with the IEEE-519effectively suppress the reactive power and improve the standards harmonics.power factor. The summarized Real (P) and Reactive (Q) powercalculation under steady state and transient condition given ACKNOWLEDGMENTin table 3. The authors would like to acknowledge to Ministry of TABLE 3 ACTIVE AND REACTIVE POWER MEASUREMENT USING PI, FLC AND Communication and Information Technology (MCIT), Govt. PI WITH FLC CONTROLLER of India for the financial support. REFERENCES [1] S. Saad, L. Zellouma “Fuzzy logic controller for three-level shunt active filter compensating harmonics and reactive power” Electric Power Systems Research, Elsevier, page no 1337– 1341 May-2009 [2] S.K. Jain, P. Agrawal and H.O. Gupta “Fuzzy logic controlled shunt active power filter for power quality improvement”- IEE proc.electr.power.appl,Vol 149, No.5, Sept-2002 The Fourier analysis of the source current signal can be [3] Karuppanan P and KamalaKanta Mahapatra “Fuzzy Logiccalculating the magnitude and the fundamental or order of Controlled Active Power Line Conditioners for Power qualityharmonic component of the signals, shown in fig 8. Improvements” International Conference on Advances in Energy Conversion Technologies (ICAECT 2010), Jan- 2010 pg no.177-181 [4] V. S. C. Raviraj and P. C. Sen “Comparative Study of Proportional–Integral, Sliding Mode, and Fuzzy Logic Controllers for Power Converters” IEEE Tran Industry Vol 33, No. 2, March/Appl-1997. [5] Brod D.M, Novotny D.M “Current control of VSI-PWM Inverter”-IEEE Trans on Industry Appl, Vol.21, pp.562-570- July/Aug. 1985 [6] K. K. Mahapatra, Arindam Ghosh and S.R.Doradla “Simplified Fig.8 Fuzzy logic with PI-controller based order of harmonics model for control design of STATCOM using Three-Level measured with respect to the magnitude under the steady state Inverter”- IEEE Conference vol. 2, pp. 536-539- 1998condition (a) Source current without APF, (b) source currents with AP F 33© 2011 ACEEEDOI: 01.IJCSI.02.02.109