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K. Periyasamy / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.771-777Power Factor Correction Based On Fuzzy Logic Controller With Average Current-Mode For DC-DC Boost Converter K. Periyasamy*ABSTRACT Power Factor Correction (PFC) provides (SMPS’s), high power factor and low line currentwell-known benefits to electric power systems. harmonic distortion are expected to be mandatoryThese benefits include power factor correction, requirements for SMPS’s in coming years.poor power factor penalty utility bill reductions, Traditionally, the implementation of switching powervoltage support, release of system capacity, and supply has been accomplished by using analog powerreduced system losses. The performance of fuzzy factor correction (PFC). Critical to the performancelogic controller only depends on the selection of of PFC pre-regulator is the choice of current modemembership function and Inference of fuzzy rules, and control methods. The three mode of controlfuzzy logic controllers have an advantage in based on inductor current are the average current-coping with the time varying non-linearity of mode control [2],[7],[12]. the peak current-modeswitches. The Proportional & Integral controllers control and the inductor current hysteretic control.(PI) controller design requires an accurate The main distinguishing feature of ACMC, asmathematical model of the plant. Also it fails to compared with peak current mode control, is thatperform satisfactorily performance under various ACMC uses a high gain, wide bandwidth Currentparameters such as voltage variations, Error Amplifier (CEA) to force the average of onenonlinearity, load disturbance, etc. The paper current within the converter, typically the inductorpresents an advanced PFC technique by using current, to follow the demanded current referenceaverage current-mode control for DC-DC boost with very small error, as a controlled current source.converters. The PFC strategy uses PI controllersto correct the input current shape and fuzzy The superior characteristics of an averagecontroller to control the output voltage. A model current mode control such as a good trackingfor Power Factor Correction has been formed by performance of an average current, no slopeusing the MATLAB software. The produced compensation, and noise immunity have beenmodel has also been simulated by using fuzzy logic discussed. In an average current mode control, thetools. The simulation results show that the fuzzy compensation network is presented in a currentcontroller for output voltage can achieve better control loop to use the average current as a controlleddynamic response than its PI counterpart under quantity. Traditional frequency domain analoglager load disturbance and plant uncertainties. control methods are predominantly used in controller design for PFC pre-regulator [3], such as PIKeywords- Converter, Average current mode, controller. However, there are a number ofFuzzy inference systems, Fuzzy rules, drawbacks that found in a analog controller, such asMembership function. temperature drifts and aging effect of the components. The digital controller has many1. INTRODUCTION advantages [3],[6] over analog counterpart one, Worldwide, the markets of internal and including programmability, adaptability, lessexternal switch mode ac/dc power supply (SMPS) susceptibility to environmental variations, nohave been growing at a faster rate for several temperature and aging effect, and more immunity toapplications such as communications, computers, the input voltage distortion, etc…instrumentation, Industrial controls, andmilitary/aerospace area. Majority of present day Research on the theory and application ofSMPS employ analog control and are under going fuzzy logic has been growing since its firstslow evolution. A conventional SMPS employs a introduction in the mid-1960s. Among its manydiode rectifier for ac to dc conversion. This type of applications, fuzzy logic has been shown to be autility interface generates harmonics and the input powerful tool in dealing with uncertainties andpower factor (PF) and total harmonic distortion nonlinearities in control systems. In the past decade,(THD) are poor. Most usage converter for SMPS fuzzy control has been used in many industrialdesign is boost converter. applications, such as control of the PWM inverter for Due to the increased awareness of the many an ac drive [7], performance control of a dc drive,undesirable consequences of harmonic distortions in and switch control in dc/dc converters [5],[10]. Inline currents drawn by switch-mode power supplies response to the concerns, this article evaluates the feasibility employing state of the art digital control of power factor correction stage with fuzzy logic 771 | P a g e
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K. Periyasamy / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.771-777algorithm. Result of simulation shows the current multiply the fuzzy output voltage (input A) andloop with PI controller proposed in paper obtains a rectified sinusoidal voltage (input B). thishigh steady performance and the fuzzy controller for multiplication voltage is divide by fundamentaloutput voltage can achieve better dynamic response harmonic voltage(input C). The output of the MDBthan its PI counterpart under lager load disturbance is Vref. Vref is converted to Iref by adding resistor in[11]. parallel. Current error control circuit is used to obtain I in.2. METHODOLOGY Inductor current has high harmonics. So Current2.1 Circuit Description wave shape in irregular form. average current- mode The power factor correction circuit [13], has technique is used to minimize the harmonics andbeen shown in Fig.1. The power circuit is a dc-dc obtain regular current wave shape. Pulse Widthboost converter. The command circuit is the one Modulation (PWM) gives gate signal to driver circuitdescribed in [9], in which the analog controller was by comparing of reference signal and carrier signal.replaced with a Fuzzy one. The output of the Fuzzy Driver circuit gives the triggering pulse to thecontroller is Vc. The Fig. 2 shows the command MOSFET in the proper sequence. Driver circuit getprinciples of wave shapes. In average current control input from PWM. The MOSFET switch ON and OFFmethod, an input voltage sensing required to obtain a corresponding to triggering pulse. PI controller tosinusoidal reference, an analog multiplier to combine correct the input current shape and a fuzzy controllerthis reference with the output information, and an to control the output voltage. So the power factor iserror amplifier in current loop to extract the improved near unity.difference between the input current and the 2.2 . Single Phase Boost PFC Converterreference to generate the control signal formodulating the input current. There are a lot of very sophisticated researches of boost converter dynamics [1],[8],[13] The most of In average current control method [13], an PFC is based on boost converter, because of its inputinput voltage sensing required to obtain a sinusoidal inductor which reduces the total harmonics distortionreference, an analog multiplier to combine this and avoids the transient impulse from power net, thereference with the output information, and an error voltage of semiconductor device below outputamplifier in current loop to extract the difference voltage, the zero potential of Q’s source side whichbetween the input current and the reference to makes it easy to drive Q and its simple structure.generate the control signal for modulating the input Therefore, satisfied teaching of advanced powercurrent. Average Current Mode Control (ACMC) as electronics should be introduced by unity powera general purpose, high-performance all-round factor and high efficiency by dc-dc boost converter.control method for AC-DC conversion, DC-DCconversion, and DC-AC conversion (including grid-feed inverters). ACMC achieves superiorperformance. Average Current Mode Control 2.3. Simulation Model(ACMC) is typically a two loop control method This section will focus on implementation of the(inner loop, current; outer loop, voltage) for power PFC in MATLAB. The PFC with Fuzzy controllerelectronic converters. Single phase 230V, 50Hz AC and the average current-mode control is described insupply given to the circuit. The PFC Circuit bridge Fig.3 In digital implementation of average current-rectifier converts ac supply to dc supply. smoothing mode control DSP, microprocessor or FPGA are usedcapacitor or filter capacitor used to obtain smooth to calculate the duty cycle in every switching periodrectified output wave form. The DC-DC Boost based on the feedback current and the referenceconvertor output is Vo. current The switch Q is controlled by the calculated duty cycles to achieve unity Power factor. From Fig.Fig.1 Power factor correction circuit that uses the 3 can be distinguished the following essential blocks:Average current-mode the single-phase supply; the rectifier; the boostFig.2 Waveforms of the reference current and converter; the Fuzzy controller; a block used for theinductor current for PI transfer function and the PWM & Drive block.average current-mode Multiplication and Division Block (MDB)[13], is Fig.3 Schematic of PFC using Mat Lab.used to obtain the reference current Iref. The MDBhas three input voltage. First input is the fuzzy 2.4. Fuzzy Controlleroutput voltage Vc ( input A ). second one therectified sinusoidal waveform with the line frequency Fig.4 shows Block diagram of typical fuzzy logicVs (input B) and third input is the fundamental controller. Fuzzy controller is based on a Mamddaniharmonic of the voltage Vd ( input C). Input B is Fuzzy system with contain two input variables thattaken from line current. This line current convert to are defined by Eqn.1, Eqn.2 and only output variablevoltage by adding resistor in series. The MDB is Eqn.3. 772 | P a g e
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K. Periyasamy / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.771-777e = Vref - Vo (1) Simulations are performed by MATLAB toΔe = e(k) - e(k-1) (2) verify the proposed PFC control algorithm. Under theΔU = k1 e + k2 Δe (3) parameters of input voltage Vl=220V (rms), outputWhere e and Δe are the input variables, k1 and k2 are voltage Vout=400V, inductor value L=800μH,nonlinearity coefficients. ek and ek-1 are the output capacitor value 1700μF. Fig.12 shows sinusoidalvoltage error at kth and (k-1)th control period. waveform of the input voltage and rectified positive half cycle voltage wave form. Input voltage 220V is The fuzzy controller [13], control the output given to the rectifier circuit. output of the rectifiervoltage(Vo). Fuzzy controller has two input that, error circuit voltage is 218.5V. Fig.13 shows the Inputvoltage(e) and change in error voltage (Δe). The error current waveform of the boost converter. Averagevoltage is obtain from difference between output Current Mode Control (ACMC) is typically a twofeedback voltage(Vo) and reference voltage(Vref). The loop control method (inner loop, current; outer loop,change in voltage(Δe) is the difference between error voltage) for power electronic converters. Averagevoltage and previous error voltage. FIS Editor as Current Mode Control is used to correct the inputshown in fig. 5. current shape. Fig.14 shows Inductor currentFig.4 Block diagram of typical fuzzy logic waveform with some harmonics but Fig.15 showscontroller output current waveform without harmonics. outputFig.5 FIS Editor of the boost converter is 300V and output voltage The input error voltage(e) has seven waveform represented in Fig.16. an output voltagemembership function and changing error voltage(Δe) has wave form maintain around a specified average valueseven membership function. Fuzzy controller compare the with low ripple. PI controller output current andtwo voltage membership function and produce one output fuzzy controller output voltage are represented involtage membership function. This is called fuzzy output Fig.17 & 18. Table.2 shows the parameter value ofvoltage(Vc). the converter. The first input variable e in the fuzzy system Fig. 12 input voltage and rectified voltagehas seven membership functions and represented in Fig. 13 Input current waveFig.6. The second input variable Δe in the fuzzy Fig. 14 Inductor current wavesystem has seven membership functions and Fig. 15 output current waverepresented in Fig.7. The output variable has seven Fig. 16 output voltage wavemembership functions as shown in Fig.8. The rules Fig. 17 PI output currenttable according to which the decisions are made is Fig. 18 fuzzy output voltagerepresented in table1. Table.2 Parameter values of the converterFig.6 Membership functions shapes for e In Conventional Method buck converter isFig.7 Membership functions shapes for Δe used for power factor correction. It has more losses,Fig.8 Membership functions shapes for output less power factor &less efficiency. In Proposedvariable system, Boost converter is used for power factorTable.1 The fuzzy rules correction. It has several advantage, high power FAM table contain seven linguistic variable factor, high efficiency, less losses. Analog controllerfor error voltage and seven linguistic variable for is used for correcting power factor. Analog controllerchanging error voltage. Increasing of number of has several disadvantages, A Number of partslinguistic variable gives the accurate output. The 49 required in the system and their susceptibility tofuzzy rules are made by using the two input variable aging and environment variations, which lead to highmembership function. For example, cost of maintenance, Analog control once designed isIf error voltage NB and change in error voltage NB inflexible and performance cannot be optimized forthen output voltage NS various utility distortions, there are a number ofIf error voltage NB and change in error voltage NM drawbacks that found in a analog controller, suchthen output voltage NM as temperature drifts and aging effect of theIf error voltage NB and change in error voltage NS components.then output voltage NB If error Digital control is used for power factorvoltage NB and change in error voltage Z then correction and it has several advantages such asoutput voltage NB If programmability, adaptability, less susceptibility toerror voltage NB and change in error voltage PS then environmental variations, no temperature and agingoutput voltage NB. effect, and more immunity to the input voltageFig.9 to fig.11 show the rule editor, rule viewer and distortion no losses, simple control strategy. Researchsurface viewer of the fuzzy controller. on the theory and application of fuzzy logic has beenFig.9 Rule Editor growing now a day. Among its many applications,Fig.10 Rule Viewer fuzzy logic has been shown to be a powerful tool inFig.11 Surface Viewer dealing with uncertainties and nonlinearities in3. RESULTS & DISCUSSIONS control systems. Result shows that current loop with PI controller obtains a high steady performance and 773 | P a g e
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K. Periyasamy / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.771-777the fuzzy controller for output voltage can achievebetter dynamic response than its PI counterpart underlager load disturbance. In this Proposed systemAchieve high power factor during steady-stateoperation with constant load and Respond quickly toload disturbances with minimum harmonics. 1. FIGURES AND TABLES Fig. 4 Block diagram of typical fuzzy logic controllerFig. 1 Power factor correction circuit that uses theAverage current modeFig. 2 Waveforms of the reference current and Fig. 5 FISEditorinductor current for average current-modeContinuous powergui i i + - + - rectifier Lf iL i out input current L Diode D1 D3 i + - + v - i in + v inductor current v2 vout - R v3 To Workspace C t G D Vin S Clock To Workspace1 S D4 output current D2 Modulation Index Out1 M Sine Wave signal output voltage THD THD Relational Product 1 + - v1 Operator PI 1 v Constant >= PI 50 THD Out1 0.2888 Carrier Pulse input & rectified voltage Display Fig. 6 Membership functions shapes for e [t vout ] From du/dt fuzzy output voltage Workspace Fuzzy Logic Derivative Controller Gain -K-Fig. 3 Schematic of PFC using Mat Lab 774 | P a g e
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K. Periyasamy / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.771-777Fig. 7 Membership functions shapes for Δe Fig. 11 Surface ViewerFig. 8 Membership functions shapes for outputvariable Fig. 12 input voltage and rectified voltageFig. 9 Rule Editor Fig. 13 Input current waveFig. 10 Rule Viewer Fig.14 Inductor current wave 775 | P a g e
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K. Periyasamy / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 www.ijera.com Vol. 2, Issue 5, September- October 2012, pp.771-777 Table 1. The fuzzy rulesFig. 15 output current wave PARAMETER SYMBOL VALUE Input voltage Vin 220rms V Rectified Vrec 218.5 V voltage Input current Iin 2 Amps Inductor current Li 2.2 Amps Output current Iout 1.4 Amps Output voltage Vout 300 V Fuzzy output Vfuzzy 400 V voltage Resistor R 200 Ω Capacitor C 1700µ F Inductor L 800µ H PI controller Kp 0.00001 constantFig. 16 output voltage wave Diode D 0.001 Ω MOSFET S 0.1 Ω Sine wave Ref signal 1 Amplitude Triangular wave Carrier 1 Amplitude wave Modulation M 1 index Table 2. Parameter values of the converter 5. CONCLUSION The single-phase boost PFC converter, using the classic control strategy for current loop, requires that a sinusoidal reference for the current is createdFig. 17 PI output current by MDB. The fuzzy controllers are designed by using the output voltage error and the change of voltage error. The simulation results show that the high power factor can be achieved under wide output power conditions. Fuzzy logic control has a advantage of coping with larger parameter variation of the system and it overshoot limitation and sensitivity to parameter variation. REFERENCES Journal Papers: [1] Amudi A.E1, Leyva.R, "Quasi-periodic route to chaos in a pwm voltage-controlled dc-dc boost converter," IEEE Tram Circuits Syst. I, vo1.48, 110.8, pp.967-978, Aug.Fig. 18 fuzzy output voltage 2001. 776 | P a g e
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