Analysis of Cuk Converters for Power Factor Correction Applications

Analysis of Cuk Converters for Power Factor Correction Applications

S. Sivajanani @ Santhoshma

Department of Electrical and Electronics Engineering Manakula Vinayagar Institute of Technology Puducherry, India

N. Veeramuthulingam

Department of Electrical and Electronics Engineering Surya Group of Institutions

Villupuram, India

N. Arunkumar

Department of Electrical and Electronics Engineering Manakula Vinayagar Institute of Technology Puducherry, India

D. Balaji

Department of Electrical and Electronics Engineering Manakula Vinayagar Institute of Technology Puducherry,India

AbstractThis paper presents the clear view of need for power factor correction. It also discussed the conventional types of power factor correction methods employed by the use of power electronic converters. The drawbacks of the conventional converter are overcome and new proposed converters with three different configurations are analyzed in this paper. The working of all the three types of converters is illustrated with the waveforms. The theoretical concepts are followed by the simulation results of all the three proposed converters. The simulation results are justified by the hardware implementation of the Cuk Converters.

Keywordsdicontinuous mode of operation; power factor correction; less ripple current; cuk converters.

1. INTRODUCTION

   Most of the equipments involved in the sophistication of the people are made to operate with power supplies of unity power factor. The machines operating with fixed power supplies along with active power factor are applied in many areas like communication, computer, automotive & biomedical industries. The fixed power supply can be achieved by means of power electronic components. Also to meet out the harmonic regulations & standards, Power Factor Correction (PFC) is needed. The active power factor correction is needed for the efficient working of the equipments. The active power factor correction using power electronics components found to be economical, efficient & reliable. So, this paper will present an idea about power factor correction using Cuk converters. The conventional power factor corrective methods and their drawbacks are discussed in the Section II. Section II discusses the proposed method for power factor correction. Its theoretical analysis along with the explanation of three types of proposed circuit. Section III presents the simulation results of the proposed method along with the output and input voltage waveforms and with tables tabulating the values of power factor for many loads. Section IV gives the hardware implementation of the proposed method with the relevant waveforms. Finally, Section V discussed the conclusion of the work presented in this paper.

2. CONVENTIONAL POWER FACTOR CORRECTION METHODS

   Power factor correction using conventional converters are analyzed in this section. The PFC scheme has been configured in three different converters. The PFC schemes are analyzed in Boost, Buck and Cuk converters topology.

   1. Drwabacks of using Boost converter for PFC applications

      The boost converter when operated in discontinuous current mode (DCM) leads to the output current with high ripple content. This disadvantage has made it not suitable for the power factor applications.

   2. Drawbacks of using Buck converter for PFC applications

      In the operation of the buck converter in DCM, the input current does not follow the input line voltage. Moreover, the output voltage ratio is nearly reduced to half. The efficiency of the buck converter is also poor because of the high harmonic distortion at the output side and reduced power factor.

   3. Analysis of Cuk converter for PFC applications

   The cuk converter designed for power factor correction can be operated in both continuous and discontinuous current modes has many advantages like easy implementation of the transformer isolation, protection against high inrush current, low current ripple and also less Electromagnetic Interference (EMI). The conventional Cuk converter is illustrated in the Fig. 1.

   The conventional Cuk converter has a diode bridge at the front end of the circuit. The diodes conduct in both positive and negative cycles and leads to large conduction loss and so efficiency is reduced. It acts as the major reason for the development of new PFC topology using bridgeless Cuk converter. The detailed working of these conventional converters is discussed in Thus, the Section II has briefly demonstrated the conventional methods of PFC and their

   drawbacks.

   Fig. 1. Conventional Cuk converter

   The proposed Cuk converter is the combination of two dc- dc rectifiers, each one conducts for one half cycles. There is only one or two semiconductors in the process of connecting the input voltage to the output side which means that the conduction losses and the stress upon the switches are also greatly reduced thereby increasing the efficiency of the proposed scheme. The new topology has another advantage of low EMI when compared with the conventional one. The circuit consists of two semiconductor switches which can be operated depending upon the voltage ratio required by any load.

   The circuit also has an additional inductor which improves the thermal performance of the circuit. The three inductors can be coupled on the same magnetic core for reducing the cost and size of the circuitry also. The working of type -1 converter is discussed in detail in [1]-[10]. The working of type-2 converter is not discussed in [19].

3. PROPOSED CUK CONVERTER FOR POWER FACTOR CORRECTION APPLICATIONS

   This chapter discusses about the need for new topology of PFC. New experiments were conducted to improve the efficiency by replacing the front end bridge by two switches alone. By doing so, the efficiency of converter increased also it is found to be economical.

   Fig. 2 Types of the Proposed Cuk Converter

   1. OPERATION OF TYPE 3 CUK CONVERTER

      Before analyzing the converter, the following assumptions are made,

      1. The circuit is working in steady state with pure sine wave at its input side,

      2. Lossless components,

      3. The capacitors are large to maintain the voltage constant and to have zero ripple voltage.

         During the positive half cycle, the first dc-dc cuk circuit, L1

         – Q1 – C1 L01 D01 are active through the diode Dp thereby connecting the input voltage to the output side load. During the negative half cycle, the second dc-dc cuk converter circuit, L2 Q2 C2 L02 D02 are active through the diode Dn.

         The proposed converter operates in DCM mode which has another advantage of near unity power factor. The switches are turned on at zero current and also the output diodes are turned off at zero current, thereby reducing the conduction losses.

         Unfortunately the DCM operation has a disadvantage of limiting this topology to low power application alone. (<300W). The working of converter is very similar to the conventional cuk converter with three distinct stages in one switching period Ts.

         The theoretical waveforms of cuk converter with DCM for positive half cycle alone are depicted in Fig. 3.

   2. Stage 1 (t 0 to t 1 )

      In this stage, the switch Q1 is in ON state. Diode Dp is forward biased by the inductor current I L1. The diodes Dn, D01 and D02 are reverse biased. The current through the inductors L1 , L01 are linearly raised.

      But, the current through L02 is zero due to the fixed capacitor voltage across C2.

      The peak curent reached in this stage is given in (1).

      I Q1,pk = (Vm / Le )* (D1 Ts ) (1)

      Where, V m is the maximum amplitude of the input voltage and D1 is the duty cycle and Le is the parallel combination of inductors L1 and L01.

      Fig. 3. Theoretical Waveforms of Type 3 converter operating in DCM

      The second stage period can be derived and shown in (2) where, M is the voltage conversion ratio (V0 /Vm) ,

      D2 = (D1/M) * sin t (2)

      The working of the type 1 converter is very similar to the type 3 except for the stress across the output load side. Thus this Section III discussed about the working of Type 3 converter with necessary diagrams.

4. SIMULATION RESULTS OF THE PROPOSED CUK CONVERTER

   The new Cuk converter discussed in section III is validated by the simulation results. Type1, Type 2 & Type 3 converters are chosen for the simulation process and the simulation is done by using MATLAB software package. The simulation parameters of the converter are listed in Table I.

   Table . I Simulation Parameters

   Parameters	Values
   Input Voltage , Vs	120*1.414
   Inductors L1, L2	1mH
   Capacitors C1 , C2	1µF
   Output capacitor, C0	12000µF
   Output inductor, L0	22µH
   Input frequency, fs	50 Hz
   Switching frequency	50 KHz
   Output resistor	50

   The waveforms obtained by the simulation of all the three types converters is shown in the Fig. 4. text edit has been completed, the paper is ready for the

   1. Stage 2 (t1 to t2 )

      In this stage, the switch Q1 is turned off but diode D01 is turned ON to provide a continuous current path for the inductors L1, L01. This stage ends when the current through D01 reaches zero and it become reverse biased. The current through the inductors are found be linearly decreasing. The magnitude of the decreasing current is shown in the waveform itself.

   2. Stage 3 (t 2, t s )

   This stage operates with only one diode Dp in conduction to provide a current path for IL1. The inductors will now behave as constant current sources and so no voltage across all the three inductors. Capacitor C1 is charged by the inductor current IL1. This stage ends when Q1 getting turned ON.

   Fig. 4. Simulated Output Voltage waveforms of Type 1, Type 2 and Type 3 Cuk converters

   It is inferred from the waveforms that the type 3 converter is working efficiently. The waveforms across inductors and capacitors are illustrated in the Fig. 5.

   Fig. 5. Simulated Voltage and current waveforms across the inductors and capacitors

   Thus, this section discussed about the simulation results of all the converters along with the waveforms.

5. HARWARE IMPLEMENTATION OF TYPE 3 CONVERTER

   The type 3 converter discussed so far is now implemented in hardware. The output and the input voltage waveforms for this type of converter is shown in Fig. 6.

   Fig. 6. Hardware implementation of type 3 converter with output load resistor of 15.

6. CONCLUSION

This paper discussed about the power factor correction converters using Cuk Topology. It also discussed about the conventional converters drawbacks and the proposed converters advantages. The proposed converter is simulated and the results are produced in this paper along with the hardware implementation. It is also concluded that among the three types, type 3 proves to be best and economical.

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S.Sivajanani @ Santhoshma received her B.Tech in Electrical and Electronics Engineering from Pondicherry University in 2010 and also she completed her M.Tech in Electrical Drives & Control in Pondicherry Engineering College in 2012. Presently, she is working as Assistant Professor in the

Department of Electrical and Electronics Engineering, Manakula Vinayagar Institute of Technology, Pondicherry, India. Her area of interest includes power electronics,harmonic analysis, multilevel inverter modulation techniques, power factor corrective methods.

N.Veeramuthulingam was born on 16th Feb 1988, in, Pondicherry India.He received his B. Tech. and M.tech. Degrees from the Electrical And Electronics Engineering of Pondicherry University, Puducherry, in Electrical And Electronics Engineering and Electric Drives and Control Power Engineering in 2009 and

2011.Currently, he is assistant Professor of electrical engineering department of Surya Group of Institution, Villupuram, Tamilnadu, India. His main research in- pulse width modulation strategies, Harmonics Analysis in power converter.

D.Balaji received his B.Tech in Electrical and Electronics Engineering from Pondicherry University in 2007 and also he completed his M.Tech in Electrical Drives & Control in Pondicherry Engineering College in 2009. Presently, he is working as Assistant Professor in the Department of Electrical and Electronics Engineering, Manakula Vinayagar Institute of

Technology, Pondicherry, India. His area of interest includes power electronics, harmonic analysis, machines.