International Journal of Electrical Engineering & Technology (IJEET) Volume 8, Issue 2, March- April 2017, pp. 101 107, Article ID: IJEET_08_02_012 Available online at http://www.iaeme.com/ijeet/issues.asp?jtype=ijeet&vtype=8&itype=1 ISSN Print: 0976-6545 and ISSN Online: 0976-6553 Journal Impact Factor (2016): 8.1891 (Calculated by GISI) www.jifactor.com IAEME Publication CONTROL METHOD FOR LCC CURRENT OUTPUT RESONANT CONVERTER P. Kowstubha Department of Electrical and Electronics Engineering, Chaitanya Bharathi Institute of Technology, Hyderabad, India ABSTRACT The main objective of this paper is to provide a self-oscillating control method for series parallel (LCC) resonant converter. The linear control methods ensure stability and good control, but only in small vicinity around the operating point. Since these controllers are sensitive to the operating points and also parameter variations, a high degree of accuracy cannot be expected from them. So, intelligent methods using the PI controller are used in this design. The results are obtained using MATLAB simulation. The circuit developed can be stabilized for line and load disturbances and the output voltage can be stabilized for the disturbance. Keywords: LCC Resonant converter, PI controller, MALAB, switching losses. Cite this Article: P. Kowstubha Control Method for Lcc Current Output Resonant Converter. International Journal of Electrical Engineering & Technology, 8(2), 2017, pp. 101 107. http://www.iaeme.com/ijeet/issues.asp?jtype=ijeet&vtype=8&itype=1 1. INTRODUCTION- SERIES PARALLEL RESONANT CONVERTER The benefits of Series resonant converter (SRC) and Parallel resonant converter (PRC) are found in seriesparallel resonant converter (SPRC). Figure 1 Circuit Diagram of LCC Resonant Converter http://www.iaeme.com/ijeet/index.asp 101 editor@iaeme.com
P. Kowstubha The SPRC has an additional capacitor or inductor connected in the resonant tank. Fig 1 shows an LCC type SPRC, in which an additional capacitor is placed in series with the resonant inductor. The resonant tank of SPRC is considered as the combination of SRC and PRC. SPRC combines the good characteristics of PRC and SRC [1]-[4]. With load in series with series tank L s and C s, the circulating energy is smaller compared with PRC. With the parallel capacitor C p, SPRC can regulate the output voltage at no load condition [5]-[6]. In this paper an intelligent controller called PI controller is implemented on LCC converter. The proportional-plus integral controllers (PI controllers) produce an output signal consisting of two termsone proportional to error signal and the other proportional to the integral of error signal. In PI-controller, u(t) { e(t)+} Therefore, u(t)= K p e(t)+ Where K p = proportional gain And T i = integral time On taking laplace transform of equation with zero initial conditions we get, U(s)= K p E(s)+ Therefore, =1+ ) The equation gives the output the PI controller for the input E(s) and the other equation is the transfer function of the PI controller. The block diagram of the PI controller is shown below in Fig 2. Figure 2 Block diagram of PI controller The proportional action increases the loop gain and makes the system less sensitive to variations of system parameters and the integral action eliminates or reduces the steady state error for a PI controller. 2. SIMULINK CIRCUIT DIAGRAMS & SIMULATION RESULTS In this section the simulation for LCC Resonant Converter is performed for both open loop and closed loop configurations. Simulation schematic of LCC Resonant Converter is given in Fig 3 and its output response is given in fig 4. http://www.iaeme.com/ijeet/index.asp 102 editor@iaeme.com
Control Method for Lcc Current Output Resonant Converter Figure 3 Simulation Schematic of LCC Resonant Converter in open loop configuration. Figure 4 Output voltage of LCC Resonant Converter in open loop configuration. From Fig 4 it is observed that an output voltage of 29V for an input of 65V for LCC Reonant Converter in open loop system.. Fig 5 represents LCC Resonant Converter in closed loop configuration. http://www.iaeme.com/ijeet/index.asp 103 editor@iaeme.com
P. Kowstubha Figure 5 Simulation Schematic of LCC Resonant Converter in open loop configuration. Fig 6. shows the output voltage of a SPRC under closed loop control, which is tested for an output voltage set point of 25 volts and the following results are obtained. It is observed that the output voltage settles at a value which is around 25V Figure 6 Output voltage of LCC Resonant Converter in closed loop configuration. Fig 7 shows the circuit to find switching losses across a single switch http://www.iaeme.com/ijeet/index.asp 104 editor@iaeme.com
Control Method for Lcc Current Output Resonant Converter Figure 7 Circuit to calculate switching losses The circuit for calculating switching losses which is shown as a sub-system above, is shown below in Fig 8 Figure 8 Loss circuit When the above circuit is designed for normal PWM converters and resonant converters, it is observed that the loss across a normal switch is 35W; whereas for a resonant switch the loss is observed to be 9W. This is depicted by the graph drawn below in Fig 9 and Fig 10. http://www.iaeme.com/ijeet/index.asp 105 editor@iaeme.com
P. Kowstubha Figure 9 Switching losses across a single switch in a PWM converter Figure 10 Switching losses across an LCC resonant Converter 3. CONCLUSIONS In this paper, a self-oscillating control method for series parallel (LCC) resonant converter is discussed. For this converer, it is understood that there is good control on output voltage in closed loop configuration, where the intelligent controller called PI -controller is implemented. The simulation work is carried out with MATLAB SIMULINK. The circuit developed can be stabilized for line and load disturbances and the output voltage can be stabilized for the disturbance ACKNOWLEDGEMENTS The author wish to thank Chaitanya Bharathi Institute of Technology authorities for permitting to publish http://www.iaeme.com/ijeet/index.asp 106 editor@iaeme.com
Control Method for Lcc Current Output Resonant Converter REFERENCES [1] 1.A.Jangiraman, N. Madhanakumar, Dr. T.S.Sivakumaran and Rahul Kumar Gupta Self-oscillating Control Methods for the LCC current output Resonant Converter, 2010 second international conference on Computing, Communication and Networking Technologies. [2] Muhammad H. Rashid, Power Electronics-Circuits, Devices, and Application, 3rd ed., 2004, Pearson Education. [3] Ned Mohan, Tore M. Underland, William P.Robbins, Power Electronics-Converters, Application and Design, 3rd ed., 2003, John Wiley & Sons. [4] AJ.Gilbert, D.A.Stone and C.M. Bingham, Design of an LCC current output resonant converter for use as a constant current source, in Proc Eur Conf Power Electron Appl, Sep.2-5, 2007, pp. 1-6 [5] Resonant converter topologies by M. Bildgen,www.datasheetcatalog.org. [6] Resonant conversion, Chapter 19, ecee.colorado.edu/copec/book/slides/ch19slide.pdf ABOUT THE AUTHOR Kowstubha. P received her four-year B.Tech degree from Sri Venkateswara University in 1995 and M.E from Bangalore University in 2003. Her fields of interests are Power Electronics and Integrated circuits. http://www.iaeme.com/ijeet/index.asp 107 editor@iaeme.com