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1 Two-phase Boost converter fed DC motor 1 Divyashree.V, 2Ashwini.A, 3Sumathi.S 1 Student, Dept. of EEE, BNM Institute of Technology, Bangalore, India. 2 Assistant Professor, Dept. Of EEE, BNM Institute of Technology, Bangalore, India. 3 Assistant Professor, Dept. Of EEE, BNM Institute of Technology, Bangalore, India. Abstract--Multi-phasing of dc-dc converters has been power to an output load and a duty cycle controller for known to give technical and economic benefits to low controlling the duty cycle of the power switch. These known voltage high power buck regulator modules. The major design commonly allow input current to be split among the advantage of multi-phasing dc-dc converters is the phase circuits, thereby increasing the efficiency of the power improvement of input and output performances in the converter, in addition, the operation of the phase circuits at boost converter. The conventional boost converter is the different phase angles can cancel input ripple current and cascaded to step-up the voltage to higher level and the output ripple voltage of the power converters. first boost stage is multi-phased to avoid high input current stress on the switch. The multi-phase Power supplies based on the paralleling a number of configuration significantly reduces the input current switching converters offer several advantages over a single ripple and the output voltage ripple due to the operation high power centralized power supply, such as low of the parallel paths and hence reducing the filter size. component stresses, increased reliability ,ease of maintenance and repair, improved thermal management,etc. Index Terms-- Boost converter, parallel operation of boost Paralleling of standardized converters will continue to be a converter, input current ripple, output voltage ripple. popular approach adopted in distributed power systems for both front-end and load converters. One basic objective of I. INTRODUCTION parallel connected converters is to share the load current DC to DC converters are widely used in regulated switch among the constituent converters. A variety of approaches, mode power supplies, telecommunications and dc motor with varying complexity and current sharing performance, drive applications and are extremely important in battery have been proposed in the past two decades. In general, powered electronic devices. The electronic devices often methods for paralleling dc-dc converters are described in contain several sub-circuits, each requiring a voltage level terms of connection styles, control configurations and different than that supplied by the battery. It is always feedback functions. desired to produce well regulated output voltage in the presence of variations in the input voltage and load current DC-DC converters being widely used, it was much preferred [5]. to design a dc to dc boost converter with an interleaved or multiphase technique to meet the higher power demands. Various multiphase power converters are known having a This type of circuit is used to ‘step-up’ a source voltage to a plurality of phase circuits connected in parallel. Typically, higher regulated voltage, allowing one power supply to each phase circuits includes a power switch for delivering provide different driving voltages and meeting the increased 2 power demands. In this work, parallel operation of the boost an inductor to resist changes in current by creating and converter using destroying a magnetic field. In a boost converter, the output are voltage is always higher than the input voltage. A schematic fed to MATLAB/SIMULINK DC drive software is and simulated the results compared with that of conventional boost converter fed to of a boost power stage is shown in Figure 1. DC drives. Converter controlled electrical machine drives are very important in modern industrial applications. The speed of the DC motor is controlled by controlling DC voltage across its armature terminals. Hence two phase boost converters can be used to control the speed of the DC drives. II. BOOST CONVERTER A boost converter is simply a particular type of dc to dc converter with an output DC voltage greater than the input DC voltage. This type of circuit is used to ‘step-up’ a source voltage to a higher, regulated voltage, allowing one power Figure 1. Boost converter supply to provide different driving voltages. Step up A. DESIGN EQUATIONS choppers for DC to DC power conversion find widespread The duty ratio (D) of a typical boost converter is given by applications in different areas. However its operation mode [9]: and control scheme strongly depend on the specific D= --- (1) application and the available components. This work presents a detailed design and analysis of the two-phase boost converter fed DC motor. Where Vout - output voltage and Vin - input voltage. The inductor shown in figure 1 can be designed using the expression: This is an interesting technique, having the features of parallel operation, and increased frequency of operation. In multiphase operation, converters are connected in parallel and are controlled by interleaved switching signals, which L= --- (2) Where L–Inductance, f–switching frequency and Irippleinductor input ripple current. The value of capacitance [9] is given by the expression: have the same switching frequency and the same phase shifting. The switching instants are sequentially phase shifted by equal fractions of a switching period. This C= --- (3) Where ∆V- output ripple voltage. arrangement lowers the net ripple amplitude and raises the effective ripple frequency of the overall converter without III. PARALLEL BOOST CONVERTER increasing switching losses or device stresses. The resulting Even though the input inductor makes the source current cancellation of low frequency harmonics allows eventually smooth the boost converter suffers from the disadvantage of the reduction of size and losses of the filtering stages. The discontinuous current injected to the load. The size of the obvious benefit is an increase in the power density without capacitor is therefore large. Further, the ripple current in the the penalty of reduced power conversion efficiency. There is capacitor is as much as the load current. Hence the ripple still a penalty of increased circuit complexity [3].The key current and the ESR specification of the tank capacitor are principle that drives the boost converter is the tendency of quite demanding. In standard designs it is uncommon to see 3 tank capacitors one or two orders of magnitude higher than Figure 3 illustrates the timing signals for the two phases the ideally required capacitance. A way to overcome this (switches Q1 and Q2) for the duty cycles 50% and 30% problem is using parallel operation. Each phase of the respectively. The frequency multiplication effect is clearly parallel boost converter works in the same way as that the shown on the combined Iin waveform as having its period single phase boost converter does. The two power stages half that of individual inductor current. One advantage that operate 180ᵒ out of phase, cancelling the ripple in the input is not apparent from the figure is the amount of peak to peak current and output voltage. The inductor current varies twice ripple on the input current which should be half that of each in every cycle of the input current. Input voltage varies twice individual inductor current. This is called the ripple in every cycle of the input voltage. The duty cycle therefore cancellation effect in multiphase scheme [4]. varies in the full range of zero to one. The parallel-boost approach which uses forced current sharing between the power stage could deliver substantially more power than the other, which would defeat the ripple cancellation[1]. Figure 2 shows the basic 2-phase boost converter. One advantage that is evident from the figure is that the multiphase configuration allows the combination of output capacitor from each individual boost into just a single capacitor Co. Due to the frequency multiplication property of the multiphase, the output voltage will actually have ripple component twice the operating switching frequency of each individual boost converter. This may further reduce the output filtering requirement. The frequency multiplication effect also occurs at the input side of the boost and hence reducing the input filtering requirement as well as improving the quality of the input current. In turns, both input and output sides of the multiphase boost will emit less dv/dt and Figure 3: Inductor current waveforms of two phase boost converter. di/dt noises back to the system connected to them. IV. SIMULATION AND RESULTS The simulation block diagram of the single phase boost converter fed dc motor is as shown in figure 4. For the given DC motor, the MOSFET is designed to have a switching frequency of 25 kHz with 50% duty cycle. The input current waveform and output voltage waveform of a single phase boost converter is as shown in figure 5 and figure 6 respectively. It can be seen from figure 5 that the input ripple current in Figure 2: Two phase boost converter the single phase boost converter is 0.5 Amps and from the 4 figure 6 it can be inferred that the output voltage ripple is output voltage. The inductor current varies from zero to 0.0125Volts. nominal current twice in every cycle of the input current as shown in figure 8. The input ripple current and output ripple voltage in the two phase boost converter is found to be 0.1Amps and 0.001Volts respectively and the corresponding waveforms are as shown in figure 9 and 10 respectively. Figure 4: Simulation block diagram of Single phase boost converter Figure 7: Simulation block diagram of two phase boost converter Figure 5: Input current waveform of single phase boost converter Figure 8: Inductor currents in two phase boost converter Figure 6: Output voltage waveform of single phase boost converter The simulation block diagram of two phase boost converter is as shown in figure 7. The circuit is designed for the same requirements as that of single phase boost converter shown in figure 4. But the two power stages operate 180ᵒ out of Figure 9: Input current waveform of two phase boost phase, cancelling the ripple in the input current and the converter 5 Table II Specifications of Motor and Various Parameters Armature resistance (Ra) 02.581Ω Armature inductance(La) 0.028 H Armature voltage (Va) 240 V Mechanical inertia (Jm) 0.10225Kg.m2 Friction coefficient (Bm) 0.002953N.m/rad/sec Rated speed 1750 rpm Field voltage (Vf) 300 V Input voltage(Vin) 120V Duty cycle 50% L 3.131mH C 1277.95uF Figure 10: Output voltage waveform of two phase boost converter. Table I Comparison of Performance of Single Phase Boost Converter and Two Phase Boost Converter CONVERTER SINGLE PHASE INPUT RIPPLE OUTPUT RIPPLE CURRENT VOLTAGE (Amperes) (Volts) 0.5 0.0125 V1.REFERENCES [1] R.Mirzaei and V.Ramanarayananm “Polyphase Boost Converters for automotive and UPF applications”, BOOST European CONVERTER Power Electronic Conference, Dresden, Germany, September 2005. TWO PHASE 0.1 0.001 [2] BOOST Dodi Garinto, “New converter architecture with multiinterleaving technique for future microprocessors.”IEEE CONVERTER INTELEC 2006. V.CONCLUSION [3] Marcos Prudente, Luciano L. Pfitscher, Gustavo Parallel boost converters are used in high power applications Emmendoerfer, Eduardo F. Romaneli, and Roger Gules, where it is not possible to obtain the required power level “Voltage Multiplier Cells Applied to Non Isolated DC– with a single stage converter. There are two advantages of DC Converters,” IEEE TRANSACTIONS ON POWER multi-phase or interleaving technique. The first point lies in ELECTRONICS, VOL. 23, NO. 2, MARCH 2008 the parallel architecture, which allows higher power [4] Taufik, Tadeus Gunawan, Dale Dolan and Makbul operation, and the second point is increasing the net Anwari ,“Design and Analysis of Two-Phase Boost DC- operating frequency in input/output of the system without DC Converter “, International Science Index Vol:4, No:7, increasing the switching frequency. By paralleling the 2010 waset.org/Publication/9970. converter, characteristics such as maintenance, repair, loss- [5] J. Chen, D. Maksimovi´c, and R. W. Erickson, “Analysis heat dissipation, reliability and fault tolerance are improved. and design of a low-stress Buck-Boost Converter in Thus parallel boost topology provides superior performance Universal-Input PFC Applications,” IEEE Trans. on over single phase. Power Electronics, vol. 21, pp. 320– 329, Mar. 2006. 6 [6] W. Wen and Y. S. Lee, “A Two-Channel Interleaving Boost Converter with Reduced Core Loss and Copper Loss,” IEEE Power Electronic Specialist Conference, pp. 1003–1009, 2004. [7] S. Luo, Z. Ye, R. L. Lin, and F. C. Lee, “A Classification and Evaluation of Paralleling Methods for Power Supply Modules,” IEEE Power Electronic Specialist Conference, vol. 2, pp. 901–908, Jun.-Jul. 1999. [8] R. and Seyezhai B.L. Mathur ,“Design and implementation of fuel cell based Interleaved Boost Converter”, At the International Conference on Renewable Energy, University of Rajasthan, Jaipur, ICRE 2011 Jan 17-21, 2011. [9] W. Li, Y. Zhao, Y. Deng, and X. He, “Interleaved converter with voltage multiplier cell for high step-up and high-efficiency conversion”, Trans. on Power Electronics IEEE 1, 2397–2408 (2010).