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International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016 Power Factor Improvement using Dual Boost Converter Miss. R. S. More, Prof .D.D.Ahire 1, 2 Electronics & Telecommunication Matoshri College of Engineering & Research Center, Nashik, India Abstract – The DC to DC converter are electronics devices used whenever there is change in DC electrical power efficiently from one voltage level to another. When the supply voltage is too high or too low, the equipment fails to operate at maximum efficiency. So, in some application boost converter will used to change level of voltage from low to high. There are two types of boost converter. They are single boost and dual boost converter. By applying same dc input voltage from bridge rectifier to both boost converters, then different voltages for both boost converters will obtained. But dual boost output voltage should be greater than single boost output voltage and it should be Vo>Vi. If a electrical device has a power factor less than 1, that means more input current must be supplied for a given output power dissipation and more powerful source is required to deliver the required output power. Hence, there is a continuous need for power factor improvement and reduction of line current harmonics. The aim of this paper is to develop a circuit for power factor correction by implementing two boost converters arranged in parallel to boost the input voltage, improve the power factor device and current quality for reducing current harmonics & switching losses. Key words – Boost converter, Dual boost converter, power factor correction (PFC), MATLAB. I. INTRODUCTION An ac to dc converter consisting of a diode bridge rectifier with a large output filter capacitor is cheap, but demands a harmonic rich ac line current. As a result, the input power factor is poor [1]. Various power factor correction (PFC) techniques are used to overcome these power quality problem [2]. The boost converter topology has been used in various ac/dc and dc/dc applications. In fact, the ac/dc power supplies with power factor correction (PFC) is almost implemented with boost topology [4], [7], [8]. The use of power factor correction is necessary in order to comply the recent international standards, such as IEC-1000-3-2 and IEEE-519 [5]. This paper introduces Dual boost PFC converter which provides high boost factor and proper controlling [5]. Here Average Current Control method is used for better control. This paper initially involves simulation of basic power electronic conventional rectifier circuits and the analysis of the current and voltage waveforms. voltage and power factor is called as lagging. In capacitive circuit, current leads the voltage and the power factor is called as leading. Fig1:Power Triangle Power Factor = A. Linear Systems In a linear system, the load draws purely sinusoidal current and voltage; hence power factor is determined by the phase difference between voltage and current. B. Nonlinear Systems In a nonlinear system like power electronics system, due to the nonlinear behavior of the active switching of power devices, the phase angle alone is not valid. A nonlinear load draws distorted line current from the line. For sinusoidal voltage and nonsinusoidal current the PF is given as follows : Power Factor = (2) = Power Factor = = (3) , ← [0,1] Where, is the displacement factor of the voltage and current. is the purity or distortion factor. Another important parameter that measures the percentage of distortion is known as the current total harmonic distortion (THDi). Which is given as follows : II. POWER FACTOR WITH LOADS Power factor is defined as the cosine of the angle between voltage and current in an ac circuit. If the circuit is inductive, the current lags behind the ISSN: 2231-5381 (1) http://www.ijettjournal.org = (4) Page 153 International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016 THDi = (5) All the types of switching converter produce harmonics because of the nonlinear relationship between voltage and current across the switching device. It creates harmonics and electromagnetic interference (EMI). It has poor power factor. It produces high losses. It requires over-dimensioning of parts. It reduces maximum power capability from the line. III.RECTIFIERS Rectifiers convert the AC supply into DC voltage for either directly connecting to loads such as heater coils, DC motors, etc. or for further conversion as in the UPS system, variable frequency AC drives (VFD), switched mode power supplies (SMPSs), induction heating inverters etc. There are two types of rectifiers called uncontrolled and controlled rectifiers. A. Uncontrolled Rectifiers Uncontrolled rectifier are used in SMPS, VFDs, DC power supplies, and some UPSs. The cicuit diagram of single phase uncontrolled rectifier is shown in Fig2. It is directly connected to a DC smoothing capacitor. Fig 3: Single phase controlled rectifier V.PURPOSE OF PFC Fig2 :Phase uncontrolled rectifier B. Controlled Rectifiers Controlled rectifiers are used in variable speed DC drives, DC power plants, induction heating and welding furnace control, etc. Fig3 shows the circuit diagram of single phase fully controlled rectifier. And it is normally connected to a smoothing inductor on the DC side. Thus output current of controlled rectifier could be considered as constant. Voltage distortions takes place due to two factors namely, commutation notches and voltage clamping. IV.NEED FOR IMPROVEMENT OF POWER FACTOR Conventional AC rectification is a inefficient process, resulting in waveform distortion of the current drawn from the mains. This produces large harmonics signals that may interfere with other equipment. At higher power level severe interference with other electronics equipment may become apparent due to these harmonics sent into the power utility line. Conventional AC rectification has following main disadvantages: ISSN: 2231-5381 Low power factor means poor electrical efficiency, the higher the apparent power drawn from the distribution network. When an electric load has a PF lower than 1, the apparent power delivered to the load is greater than the real power which the load consumes. Only real power capable of doing work, but apparent power determines the amount of power that flows into the load. In power system, wasted energy capacity also known as poor power factor. It can result in poor reliability, safety problems and higher energy costs. The lower power factor means the less economically the system operates. So for this reason, power factor correction is necessary [5]. Power factor correction circuit is to minimize the input current waveform distortion and make it in phase with the voltage one. A. Active PFC It is the most effective way to correct power factor of electronics supplies. In this approach place different Active PFC converters between the bridge rectifier and the load. The converter tries to maintain a constant DC output voltage and draws a current that is in phase with and at the same frequency as the line voltage. Active PFC has following main Advantages: Active wave shaping of the input current. Filtering of the high frequency switching. Feedback sensing of the source current for waveform control. Feedback control to regulate output voltage. http://www.ijettjournal.org Page 154 International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016 VI.BOOST CONVERTER The principle that drives the boost converter is the tendency of the inductor to resist the changes in the current. When being charged it acts as a load and absorbs energy like resistor [8], [9]. When being discharged it acts as an energy source like a battery. The voltage produced during discharge phase is related to the rate of change of current, and not to the original charging voltage, thus allowing different input and output voltages. The Fig 4 shows boost converter. current is employed in the feedback loop of the switch mode power converters. It has given new avenues of analysis and at same time introduced complexities in terms of multiple loops. VII. SIMULATION AND RESULTS This paper involves simulation of basic power electronic circuits and the analysis of the current and voltage waveforms. It starts with simple circuits with a gradual increase in complexity by inclusion of new components and their subsequent effect on the current and voltage waveforms. It will focus on the objective of improving the input current waveforms i.e. making it sinusoidal by tuning the circuits. All the simulation work is done in MATLAB simulink. Fig 4:Boost converter A. Dual boost converters Boost converters are used as active power factor correctors. However, a recently PFC is to use dual boost converter (Fig.5) i.e. two boost converters connected in parallel. Where choke Lb1 and switch Tb1 are for main PFC while Lb2 and Tb2 are for active filtering, the filtering circuit serves two purposes i.e improves quality of line currents and reduces the PFC total switching loss. The reduction in switching losses occurs due to different values of switching frequency and current amplitude for the two switches. It involves phase shifting of two or more boost converters connected in parallel and operating at the same switching frequency. This converter provides regulated dc output voltage. The control of output voltage should be performed in closed loop manner using principle of negative feedback. There are two technique of closed loop PWM dc-dc converter namely voltage mode control and current mode control. Fig 6: Current control mode A. Simulation and results for Conventional converter Fig 7 shows that this circuit consist of two groups of diodes: top group with diodes 1 and 3 and bottom groups with diodes 2 and 4. It is easy to see the operation of each group of diodes with Ls=0. The current id flows continuously through one diode of the top group and one diode in the bottom group. The circuit is simulated using Simulink and input current with respect to input voltage waveforms are plotted in graph as shown in the Fig 8 and output waveforms are plotted in graph as shown in Fig 9. The input current waveform consists of Total Harmonics Distortion. The Fig 7 shows THD of input current and THD percentage is 97.54. This problem will effect at the supply side equipments. Fig 5: Dual boost converter B. Current mode control In this mode of control as shown in Fig 6 signals in current waveform has advantage over voltage over voltage signals. Voltage being an accumulation of flux, which is slow in time as far as control mechanism, is concerned. This led to the development of a new area in switch mode power supply design using Current mode control. Here, the average or peak ISSN: 2231-5381 http://www.ijettjournal.org Fig 7: Conventional Rectifier Page 155 International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016 It is clear from Fig 10 that the power factor is 0.90 which is very low and it needs to be improve by using proceeding methods. The circuit is simulated using Simulink and input current with respect to input votage waveform are potted in graph as shown in the Fig12 and output waveforms are plotted in graph as shown in the fig 13. (a) Fig 10: Power factor (b) Fig 8: (a) Input voltage and (b) Input current waveforms Fig11:THD of Conventional Rectifier Fig 9: Output voltage waveforms as function of time B. Simulation and results for rectifiers circuit with PFC Boost Converter Boost converter is a DC-DC Converter which provides output voltage is grater than input voltage. Here, the inductor responds to changes in current by inducing its own voltage to the change in current, and this voltage adds to the source voltage while the switch is open. If a diode and capacitor combination is placed in parallel to the switch, the peak voltage can be stored in the capacitor, and the capacitor can be used as a DC source with an output voltage greater than the dc voltage driving the circuit. This boost converter acts like a step- up transformer for DC signals is shown in Fig 12. Fig 12: Boost converter (a) ISSN: 2231-5381 http://www.ijettjournal.org Page 156 International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016 (b) Fig 13 : (a) Input voltage and (b) Input current C. Simulation and results for Dual boost converter Fig 17 shows inductors L1 and L2 have the same values, the diodes D5-D6 are the same type and the same assumption was for the MOSFET( M1 & M2). Each inductor has its own switch and thus is similar with the paralleling of two single converters. When the MOSFETS M1 and M2 are in ON state, the proposed topology transfers energy from the dc source (Vb) into the inductors L1 and L2. Here, the current divides and equal current are flowing through inductor L1 and inductor L2. The output current flowing through load RL and C where C is the smoothing capacitor. Fig17 : Dual boost converter Fig 14 : Output voltage waveform as a function of time The Fig 15 shows that the power factor is 0.989 which is improved from previous model. The boost converter could not provide high boost factor. The power factor can be improved nearly unity by using dual boost converter Input current with respect to input voltage waveform are plotted in graph as shown in the Fig 18 and output waveforms are plotted in graph as shown in the Fig 19 . here, the input current waveform is nearly sinusoidal. The power factor increased from 0.989 to 0.9926 as shown in fig 20. It is made nearly equal to unity using dual boost converter. (a) Fig 15 : Power Factor Fig 18 : (a) Input voltage and (b) Input current Fig16:THD of Boost Converter ISSN: 2231-5381 http://www.ijettjournal.org Page 157 International Journal of Engineering Trends and Technology (IJETT) – Volume-42 Number-3 - December 2016 VIII: CONCLUSION The power factor correction with different converters are simulated with MATLAB simulink. In this paper conventional converter, boost converter and dual boost converter using current mode control are discussed. It is noticed that the power factor is better for dual boost converter circuit. And it is noticed that THD is less for dual boost converter. This can be further improved by using PI and Fuzzy controllers. REFERENCES Fig 19 :output voltage as a function of time Sr no Circuit topolologies 1 Conventional rectifier Boost converter Dual boost converter 2 3 [1] Input power factor 0.90 THD Output voltage 94.77 16 0.989 36.89 310 0.9926 3.40 360 [2] [3] [4] Table 1: Analysis of PF and THD [5] [6] [7] [8] [9] Fig 20 : Power factor Hussain S.Athab, IEEE Member, P.K .Shadhu khan, senior IEEE Member, “ A cost effective methods of reducing THD in single phase boost rectifier” May 2007 IEEE. Tiago Kommers Jappe & Samir Ahmad Mussa, Federal University of santa catarina, power electronics institude, “Current control techniques applied in PFC boost converter at instantaneous power interruption” June 2009 IEEE. Shikha Singh G. Bhuvaneswari Bhim singh, Department of Electrical Engineering, Indian institude of Technology, Delhi Hauz, New Delhi, India, “ Multiple output SMPS with improved input power quality” 2010 IEEE. Yungtaek Jang, senior Member, IEEE, Milan M. Jovanovic, fellow, IEEE, Kung- Hui Fang , “ High power factor soft switched boost converter” IEEE transaction on power electronics, vol.21, no.1, Jan 2006 IEEE. C. Attaianese, senior member, IEEE- V. Nardi, member, IEEE department of Automation, Electromagnetism, computer science , “ Predictive control of parallel boost converters ” 2008 IEEE. JFJ van Rensburg, MJ case and DV Nicolate, vaal university of technology, faculty of engineering & technology , “ Double boost DC to DC Converter” Jan 2009 IEEE. Yasunobu Suzaki, Toru Teshima Isao Sugawara Akira, “ Experimental studies on Active and Passive PFC circuits” 2009 IEEE. Paul Nosike Ekemezie, P.N.Ekemezie is with the department of electronics engineering “ Design of a power factor Correction AC-DC converter ”May 2007 IEEE. N. Vishwanathan, Dr. V.Ramanarayanam power electronics group, Dept of electrical engineering, Indian Institude of Science, Bangalore, India, “ Average Current mode of high voltage DC power supply for pulsed load application ”,2005 IEEE. Fig21:THD of Dual Boost Converter ISSN: 2231-5381 http://www.ijettjournal.org Page 158