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- 1. ACEEE International Journal on Control System and Instrumentation, Vol. 1, No. 1, July 2010 PI with Fuzzy Logic Controller based APLC for compensating harmonic and reactive power Karuppanan P, Kamala Kanta Mahapatra National Institute of Technology-Rourkela, India-769008 Email: karuppanan1982@gmail.com, kmaha2@refiffmail.comAbstract— This article explores design and analysis of techniques have been proposed for theirproportional integrator (PI) along with Fuzzy Logic implementation. APFs are superior to passive filters incontroller (FLC) based Shunt active power line terms of filtering characteristics and improve theconditioners (APLC) for compensating reactive power system stability by removing resonance relatedand harmonic currents drawn by the load. The aim is tostudy different control strategies for real time problems [4]. In particular, recent remarkable progresscompensating current harmonics at different power in the capacity and switching speed of powerconditions. The compensation process is based on semiconductor devices such as insulated-gate bipolarcalculation of unit sine vector and reduces the dc transistors (IGBTs) has spurred interest in active filterscapacitor ripple voltage of the PWM-VSI by using PI with for power conditioning [5-6]. This research paperfuzzy logic controller. The switching is done according to describes of a novel controller that uses PI along withgating signals obtained from hysteresis band current Fuzzy logic controller for APLC. This computedcontroller and capacitor voltage is continuously sensing source voltage is activated unit sine vectormaintained constant. The shunt APLC is investigated calculation to generate reference currents. The PWM-through Matlab/Simulink simulation under differentsteady state and transient conditions using PI, FLC and VSI inverter ripple voltage (dc side capacitor) isPI with FLC. The results demonstrate that combination of reduced using Proportional Integrated controller as wellPI with FLC is a better solution that reduces the settling as Fuzzy logic controller. A hysteresis currenttime of the DC capacitor, suppresses harmonics and controller generates switching signals for the APLC toreactive power in the load current(s). follow the reference currents and actual sensing current within specified band-limits. The shunt APLC is Index Terms— Shunt Active Power Line Conditioners investigated under different steady state and transient(APLC), PI controller, Fuzzy Logic Controller (FLC), conditions and found to be effective for power factorHarmonics, Hysteresis Current Controller (HCC) correction and reduces ripple voltage with the proposed PI with Fuzzy logic controller. I. INTRODUCTION The ac power supply feeds different kind of linear II. DESIGN OF SHUNT APLCand non-linear loads. The non-linear type of loads The basic compensation principle of shunt APLC orproduces harmonics [1]. The reactive power and active filter is controlled to draw/supply compensatingharmonics cause poor power factor and distort the current from/to the utility. So that it cancels a currentsupply voltage at the common coupling point. This harmonic on the AC side and makes the source currentdistortion is mainly induced by the line impedance or in phase with the source voltage. A shunt active filter isthe distribution transformer leakage inductance. Passive connected to the supply through filter inductances andL-C filters were used to compensate the lagging power operates as a closed loop controlled current sourcefactor of the reactive load, but due to the drawbacks as shown in fig 1. The output voltage of the inverter isresonance, size, weight, etc., the alternative solution controlled with respect to the voltage at the point ofcame up, an APLC that provides an effective solution common coupling (PCC). The design of APLCfor harmonic elimination and reactive power containing the following parameters;compensation [2]. The controller is the heart of theactive power filter and a lot of research is being A. Source current:conducted in recent years. Conventional PI voltage andcurrent controllers have been used to control the The instantaneous current supplied by the source,harmonic current and dc voltage of the shunt APLC. before compensation and it can be written as is (t ) = iL (t ) −ic (t ) (1)Recently, fuzzy logic controllers (FLC) are used inpower electronic system and drive applications [3]. Source voltage is given by vs (t ) =Vm sin ωt ( 2)This paper combines these two techniques for efficientline conditioners. APLCs are inverter circuits, If a nonlinear load is applied, then the load current willcomprising active devices such as semiconductor have a fundamental component and harmonicswitches can be controlled as harmonic current or components, which can be represented as ∞voltage generators. Different topologies and control ∑ iL (t ) =I n=1 n sin( nω +Φ ) t n (3) 7© 2010 ACEEEDOI: 01.ijcsi.01.01.02
- 2. ACEEE International Journal on Control System and Instrumentation, Vol. 1, No. 1, July 2010 3-Phase Source Rs,Ls Non-Linear Load A PCC A R B B C C L ica,icb,icc L Current L Sensor Filter Voltage A Sensor isa,isb,isc B VD C G C Vsa,Vsb,Vsc PWM-VSI 6-pulse gate drive Inverter signal generator Vdc Hysteresis Current sensor Controller VD Reference Unit Sine Current Fuzzy PI C vector generator Logic Controlle VDC,ref Controller r Fig 1 PI with Fuzzy Logic Controller based shunt Active Power Line Conditioners systemThe instantaneous load power can be written asp L (t ) = is (t ) * vs (t ) The real/reactive power injection may result in the 2 ripple voltage of DC capacitor. The selection of CDC can = Vm sin ωt * cos φ1 + Vm I1 sin ωt * cos ωt * sin φ1 be governed by reducing the voltage ripple. The ∞ specification of peak to peak voltage ripple and the + Vm sin ωt * ∑ I n sin( nωt + Φn ) rated filter current define the capacitor [2] n =2 = p f (t ) + pr (t ) + ph (t ) ( 4) π ∗ I c1, rated C DC = (10) 3ωVdr , p − p (max)From the equation the load current should contain realor fundamental power, reactive power and harmonic C. Design of filter LC and reference voltage:power. The real power drawn by the load is The design of the filter inductance (LC) and referencep f (t ) = Vm I1 sin 2 ω t * cos φ 1 = vs (t ) * is (t ) (5) voltage (VDC,ref) components is based on the following assumption; (1) The AC source voltage is sinusoidalFrom this equation the source current supplied by the (2) To design LC the AC side line current distortion issource, after compensation is assumed to be 5%. (3) Fixed capability of reactive p f (t ) power compensation of the active filter. (4) The PWM is (t ) = = I1 cos φ1 sin ω t = I sm sin ω t (6) vs (t ) converter is assumed to operate in the linearwhere, modulation index (i.e. 0 ≤ ma ≤ 1) . I sm = I1 cos φ1 (7)The total peak current supplied by the source is III. PROPOSED CONTROL SCHEME I sp = I sm + I sl (8) The proposed control system consists of referenceIf the active filter provides the total reactive and current control strategy and PWM control method ofharmonic power, then is(t) will be in phase with the hysteresis current modulator.utility voltage and purely sinusoidal. At this time, the A. Reference current control strategy:active filter must provide the following compensationcurrent 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 byB. Design of DC side capacitor: the combination of PI with FLC. The desired reference source currents, after compensation, can be given as The DC side capacitor is maintain a DC voltage with isa * = I sp sin ωt (11)small ripple in steady state and energy storage element 0to supply real power difference between load and isb * = I sp sin(ωt −120 ) (12)source during the transient period. isc * = I sp sin(ωt + 120 ) 0 (13) 8© 2010 ACEEEDOI: 01.ijcsi.01.01.02
- 3. ACEEE International Journal on Control System and Instrumentation, Vol. 1, No. 1, July 2010Where I sp = I sm + I sl the amplitude of the desired Rule Basesource current and the phase angle is can be obtainedfrom the source voltages. The capacitor voltage is E (n) PIcompared with reference value and the error is Output Rule Evaluator Fuzzification (Decision Defuzzificationprocessed in the PI with fuzzy controller shown in fig making)2. The output of the fuzzy controller has been CE (n)considered as the amplitude of the desired sourcecurrent. The reference currents are estimated by Data Basemultiplying this peak value with the unit sine vectors inphase with the source voltages. Fig 3 fuzzy logic Control block diagramUnit sine vector: Fuzzy logic controller block diagram shown in fig 3, isThe source voltages are converted to the unit current(s) derived the transition between membership and nonwhile corresponding phase angles are maintained. The membership can be gradual. The PI controller outputunit current is defined as error is used as inputs for fuzzy processing. The outputia = sin ωt , ib = sin(ωt − 120 0 ) and ic = sin(ωt + 120 0 ) of the fuzzy controller after a limit is considered as theThe amplitude of the sine current is unit or 1 volt and magnitude of peak reference current I sp .frequency is in phase with the source voltages. This Fuzzification:unit current multiplies with peak value of fuzzy logic In a control system, error between reference and outputoutput for generate the reference current. can be labeled as zero (ZE), positive small (PS), negative small (NS), positive medium (PM), negativePI with Fuzzy controller: medium (NM), positive big (PB), negative big (NB). PI-Controller The process of converting a numerical variable (real number) convert to a linguistic variable is called Proportional fuzzification. Vdc,ref gain Fuzzy Rule Elevator: The basic fuzzy set operations needed Logic Controlle for evaluation of fuzzy rules are AND (∩) , OR ( ∪ ) and Derivativ r NOT (−) e gain Vdc AND -Intersection: µ A∩ B = min[ µ A ( X ), µ B ( x)] LPF isa Vsa X OR -Union: µ A∪ B = max[ µ A ( X ), µ B ( x)] * isb NOT -Complement: µ A = 1 − µ A ( x) Vsb Unit sine X * Defuzzification: vector isc The rules of FLC generate required output in a Vsc X * linguistic variable (Fuzzy Number), according to real Fig 2 PI with fuzzy logic Controlerl block diagram world requirements, linguistic variables have to be transformed to crisp output (Real number).Figure 3 shows the block diagram of the proposed PI Database:with fuzzy logic control scheme of an APLC. The DC The Database stores the definition of the membershipside capacitor voltage is sensed and filtered using function required by fuzzifier and defuzzifierButterworth low pass filter (LPF) at 50 HZ. This LPF Rule Base:output voltage compared with a reference value. The The Rule base stores the linguistic control rules required by rule evaluator, the rules used in this papererror e = Vdc,ref − Vdc at the nth sampling instant is used in table 1.as input for PI controller. PI controller used to control TABLE 1the PWM-VSI of dc side capacitor voltage. Its transfer RULE BASE TABLEfunction can be represented as ce(n) NM NS ZE PS PM H ( s) = K P + K I / s (14) e(n)where, K P is the proportional constant [ K P =0.3] that NM NM NM NM NS ZEdetermines the dynamic response of the DC-bus NS NM NM NS ZE PSvoltage control and K I is the integration constant [ K I ZE NM NS ZE PS PM=15] that determines it’s settling time. The PI controller PS NS ZE PS PM PMoutput having certain ripple voltage, so as well as need PM ZE PS PM PM PManother process to reduce the ripple; the FLC controllerconnected together with PI controller for rectify theripple voltage problems. 9© 2010 ACEEEDOI: 01.ijcsi.01.01.02
- 4. ACEEE International Journal on Control System and Instrumentation, Vol. 1, No. 1, July 2010B) Hysteresis Band Current Control: 4 0 i a P u n c, A cr F r t e 3 0 2 0 1 0 0Hysteresis current control is the easiest control method d) -0 1 -0 2 -0 3to implement [5]. A hysteresis current controller is -0 4 0 05 .0 0. 1 05 . 1 0. 2 05 . 2 0 .3 05 .3 0. 4 2 00 i a s V s a 1 50 1 00implemented with a closed loop control system. An 5 0 0 e) -0 5 -0 10error signal, e(t), is used to control the switches in an -5 10 -0 20 0 0 .5 0 0 . 1 05 .1 0 .2 05 .2 0 3 . 0 3 .5 0 .4 Fig.4 PI with Fuzzy logic controller based simulation results for three-inverter. This error is the difference between the phase active-power-filter under the steady state condition (a) Sourcedesired current, iref(t), and the current being injected by current after APF, (b) Load currents, (c)Reference currents by thethe inverter, iactual(t). When the error reaches an upper Fuzzy logic algorithm, (d) Compensation current by APF and (e)limit, the transistors are switched to force the current source voltage per current for unity power factordown. When the error reaches a lower limit the current First for simulation time T=0 to T=0.4s with load ofis forced to increase. The range of the error signal, emax rectifier with R L load of 20 ohms and 200 mH– emin, directly controls the amount of ripple in the respectively and after the R L load of 10 ohms and 100output current from the PWM-voltage source inverter. mH change for transient condition. The transient simulation waveforms are verified similar to steady IV.SIMULATION RESULT AND ANALYSIS state waveforms shown in fig 5.The SIMULINK toolbox in the MATLAB software in 6 0 ia u s o e r n , S c u r cr t e 4 0 2 0order to model and test the system under steady state 0 - 20 a) - 4 - 6 0 0 0 0 0 .5 0 1 . 0 . 5 1 0 . 2 0 . 25 0 . 3 0 . 35 0 . 4and transient conditions using PI, fuzzy logic and 6 0 4 0 i ao c rn LL d r , a uetcombination of PI with fuzzy logic controllers. The 2 0 0 -0 2system parameters values are; source voltage (Vs) is -0 4 -0 6 0 05 .0 0 . 1 05 .1 0 . 2 05 .2 0 . 3 05 .3 0 . 4 b) 40 i a P u n c, A cr F r e t230 Vrms, System frequency (f) is 50 Hz, Source 30 20 10 0impedance of RS, LS is 1 Ω; 0.2 mH respectively, Filter -0 1 -0 2 -0 3impedance of Rc, Lc is 1 Ω; 2.5 mH, Load impedance -0 4 0 0 .5 0 0 .1 05 . 1 0 .2 05 . 2 0 .3 05 .3 0. 4 Fig.5 PI with Fuzzy logic controller based simulation results for three-of RL, LL of diode rectifier RL load in Steady state: 20 phase active-power-filter under the transient condition (a) Source c)Ω; 200 mH and Transient: 10 Ω; 100 mH respectively, current after APF, (b) Load currents and (c) Compensation current byDC link capacitance (CDC) is 1600μF, Reference APFVoltage (VDC) is 400V and Power devices build byIGBT/Diode. The DC side capacitor voltage effectively controlled by the PI or FLC and/or combination of PI with FLCPI with Fuzzy controller shown in fig 6.PI with Fuzzy logic controller based APLC system 60 0 V , a c ro g d c ao c p it vl t a e 50 0 40 0 a)comprises of a three-phase source, a nonlinear load (six 30 0 20 0 10 0pulse diode rectifier RL load) and a PWM voltage 0 -0 10 0 02 . 0 04 . 0 06 . 0 08 .0 0. 1 02 .1 04 .1 06 .1 08 .1 0 .2 60 0source inverter with a dc capacitor. The simulation time V , c a t rvt g dc a c p io o lae 50 0 40 0 30 0T=0 to T=0.4s with load of diode rectifier R L load 20 0 b) 10 0 0parameter values of 20 ohms and 200 mH respectively. -0 10 0 02 . 0 04 . 0 06 . 0 08 .0 0 .1 02 . 1 04 . 1 06 . 1 08 . 1 0 .2 45 0 V ,a c r o g dc ao c pi t vt la e 40 0The source current after compensation is presented in 35 0 30 0 c) 25 0 20 0fig. 4 (a) that indicates the current becomes sinusoidal. 15 0 10 0 5 0 0 -0 5 0 0 .2 0 0 .4 0 06 . 0 0 .8 0 0 .1 0 .2 1 04 . 1 0 .6 1 0 .8 1 0 .2The load current is shown in (b). The actual reference Fig.6 simulation results for three-phase active-power-filter under thecurrents for phase (a) are shown in fig. 4(c). This wave steady state condition of DC side capacitor voltage controlled by (a) PIis obtained from our proposed controller. The APLC controller (b) FLC controller (c) PI with FLC controllersupplies the compensating current that is shown in Fig.4(d). The current after compensation is as shown in (a) The summarized PWM- voltage source inverter of DCwhich would have taken a shape as shown in (b) side capacitance voltage (Vdc) settling timewithout APLC. It is clearly visible that this waveform measurement in transient and steady state conditionsis sinusoidal with some high frequency ripples. We using different controller as shown in table 2have additionally achieved power factor correction as TABLE 2shown in Fig. 4(e), phase (a) voltage and current are in VDC SETTLING TIME USING PI, FLC AND PI WITH FLC CONTROLLERphase. Condition PI Fuzzy PI with Fuzzy controller controller controller 6 0 ia u s oc u n , s re r c e r t 4 0 2 0 0 Steady state 0.12s 0.11s 0.064s a) - 20 Transient 0.12s 0.118s 0.06s - 40 - 60 0 0 .0 5 0 .1 0 . 5 1 0 .2 0 .2 5 0 .3 0 . 5 3 0 .4 The active power and reactive power are calculated by 6 0 L Ldun ia o c e , a r r t 4 0 2 0 averaging the voltage-current product with a running 0 -0 2 -0 4 b) average window over one cycle of the fundamental -0 6 0 0 0 .5 0 .1 05 .1 0 . 2 0 .2 5 0 .3 05 .3 0 4 . 5 0 i a, serf R r ccr t e ee r n f en ue 4 0 3 0 frequency, shown in fig 7 2 0 1 0 0 - 0 1 - 0 2 - 0 3 - 0 4 - 0 5 0 05 .0 0 .1 05 1 . 0 .2 0 .5 2 0 .3 0 .5 3 0 .4 c) 10© 2010 ACEEEDOI: 01.ijcsi.01.01.02
- 5. ACEEE International Journal on Control System and Instrumentation, Vol. 1, No. 1, July 2010 60 00 R lpw e a oe r R c e oe e t ai v pw r 50 00 TABLE 4 40 00 30 00 a) THD PI, FLC AND PI WITH FLC CONTROLLER 20 00 10 00 0 MEASUREMENT USING - 00 10 0 05 .0 0 .1 05 .1 0 .2 0 5 .2 0 .3 05 .3 0 .4 60 00 Load Without THD measurement With APLC R lp e ea o r w 50 00 R c e oe e t aiv pwr 40 00 Condition APLC PI Fuzzy PI with 30 00 b) 20 00 10 00 0 - 0 1 0 0 0 0 5 .0 0 .1 0 5 .1 0 .2 0 5 .2 0 .3 0 5 .3 0 .4 controller controller Fuzzy logic 60 00 50 00 R lpw e a oe r R c e oe e t ai v pwr controller Steady 26.28% 3.10% 2.87% 2.52% 40 00 30 00 state 20 00 c) 10 00 0 - 0 1 0 0 0 05 .0 0 .1 05 .1 0 .2 05 .2 0 .3 05 .3 0 .4 Transient 26.37% 3.18% 2.79% 2.32% Fig.7 simulation results for three-phase active-power-filter under the steady state condition of real and reactive power analysis for powerquality improvements by different controller (a) PI controller (b) FLC controller (c) PI with FLC controller V. CONCLUSIONSThe PI with fuzzy logic controller based APLC system Proportional-Integral with fuzzy logic controller basedeffectively suppress the reactive power and improve the Shunt APLC performs quite well and it reducespower factor. The summarized Real (P) and Reactive harmonics and reactive power components. Simulation(Q) power calculation under steady state and transient results demonstrate that source current aftercondition given in table 3. compensation is sinusoidal and in phase with source voltage. The compensation process is designed based TABLE 3 on calculation of unit sine vector and it also reduces the ACTIVE AND REACTIVE POWER MEASUREMENT USING PI, FLC AND PI WITH FLC CONTROLLER ripple voltage of the dc capacitor of the PWM-voltage source inverter. The PI, FLC and PI with FLC- Load Without APLC Power measurement With APLC controllers are investigated under both steady state and Condition PI P=4.039 KW transient conditions and it is observed that PI with Q=0.081 KW FLC-controllers provides superior performance in Steady P=3.907 KW Fuzzy P=4.033 KW terms of compensation and settling time compared to state Q=0.219 KW Q=0.072 KW other methods. The APLC is in compliance with the PI with P=4.057 KW Fuzzy Q=0.075 KW IEEE-519 standards harmonics. PI P=4.97 KW Q=0.041 KW ACKNOWLEDGMENT Transient P=4.847 KW Fuzzy P=4.98 KW Q=0.268 KW Q=0.040 KW The authors would like to acknowledge to Ministry of PI with P=5.17 KW Communication and Information Technology (MCIT), Fuzzy Q=0.036 KW Govt. of India for the financial support.The Fourier analysis of the source current signal can be REFERENCEScalculating the magnitude and the fundamental or orderof harmonic component of the signals, shown in fig 8. [1] S. Saad, L. Zellouma “Fuzzy logic controller for three- Mg i u eb s do " a eP a "-P r mt g it d b s do " a eP a " - P r m t r a a ee level shunt active filter compensating harmonics and e k reactive power” Electric Power Systems Research, 10 n Bs 8 a) Elsevier, page no 1337–1341 May-2009 ee n u e a e 6 [2] S.K. Jain, P. Agrawal and H.O. Gupta “Fuzzy logic 4 aa M r a 2 0 0 2 4 6 8 10 Od r o H r o i r e f am n c 12 14 16 18 controlled shunt active power filter for power quality ek improvement”-IEE proc.electr.power.appl,Vol 149, No.5, 12 n Bs 10 Sept-2002 8 ae b) 6 [3] Karuppanan P and KamalaKanta Mahapatra “Fuzzy an d 4 t 2 0 0 2 4 6 8 10 O e o Hr o i rdr f amn c 12 14 16 18 Logic Controlled Active Power Line Conditioners for Fig.8 Fuzzy logic with PI-controller based order of harmonics Power quality Improvements” International Conference measured with respect to the magnitude under the steady state on Advances in Energy Conversion Technologies condition (a) Source current without APF, (b) source currents with (ICAECT 2010), Jan- 2010 pg no.177-181 APF [4] V. S. C. Raviraj and P. C. Sen “Comparative Study of Proportional–Integral, Sliding Mode, and Fuzzy LogicThe total harmonic distortion (THD) measured of a Controllers for Power Converters” IEEE Tran Industryperiodic distorted signal. The analysis of the shunt Vol 33, No. 2, March/Appl-1997.APLC brings the THD of the source current is less than [5] Brod D.M, Novotny D.M “Current control of VSI-PWM Inverter”-IEEE Trans on Industry Appl, Vol.21, pp.562-5% into compliance with IEEE-519 standards, shown 570- July/Aug. 1985in table 4. [6] K. K. Mahapatra, Arindam Ghosh and S.R.Doradla “Simplified model for control design of STATCOM using Three-Level Inverter”- IEEE Conference vol. 2, pp. 536- 539- 1998 11© 2010 ACEEEDOI: 01.ijcsi.01.01.02

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