A Novel Microgrid Based DC-DC Converter for Rural Telephony

Transcription

1 Volume 2, Issue 2, April-June, 2014, pp , IASTER Online: , Print: ABSTRACT A Novel Microgrid Based DC-DC Converter for Rural Telephony Renugadevi.V 1, Margaret Amutha.W 2, Dr. Rajini.V 3 1 PG Scholar, 2 Research Scholar, 3 Professor Department of EEE, SSN College of Engineering, Chennai, India Nowadays, we are facing a major problem of power cut in many parts of the country. It not only affects the domestic and industrial applications but also the telecom applications. Telecom towers are energized by base transceiver stations (BTS) which require continuous power supply. Telecom providers are facing a tough challenge in providing continuous reliable service. This case is more worse especially in remote areas. The use of diesel generators cause high fuel cost and is not environment friendly as it emits hazardous green house gases like CO 2, etc. Various researches in the area of renewable energy sources shows good results in getting energy from them. This provides an effective solution for this problem. Traditionally they use single input converters for each source but later they were replaced by multiple input converters which reduce the component count and cost. The proposed dual input Cuk-Buck converter is simulated using MATLAB software and hardware implementation is done for the proposed system. Keywords: Cuk-Buck Converter, Hybrid Solar-Wind Source, Gate Pulse generation, Power circuit design, Hardware Implementation of the Converter 1. INTRODUCTION Telecommunications plays a major role all over the world. It includes both urban and rural areas. Non availability of continuous power supply especially in rural areas affects the reliable telecom service. So to provide continuous power supply renewable energy sources are preferred than diesel generators. The renewable energy sources are the sources which are inexhaustible. Renewable sources like solar, wind, hydro, etc, are mainly used to provide continuous power supply. Hybrid sources like solar and wind can be used to supply the load separately or simultaneously depending on the requirement[1]. First they use single input converters for each source which is complex and are costly. So the use of multiple input single output converters reduces the cost and component count[2]. Investigations on various DC-DC converters prove that the combination of Cuk-Buck converter suits this application the best [3]. The cuk converter draws energy from the solar source and the Buck converter draws energy from the wind source. This Combination provides the maximum efficiency compared to other combinations like cuk-cuk, buck-buck, buck-cuk, etc. 2. BLOCK DIAGRAM The figure below shows the block diagram of the proposed system of dual input Cuk-Buck converter. Here the solar and wind energy is processed by a single fused converter instead of single converter for each source. The circuit diagram of the proposed system is shown at Fig.2 below. 25

2 Fig.1. Block Diagram of Proposed System Fig.2.Topology of Cuk-Buck Converter The various operating modes of the proposed converter is shown below. Fig.3.Mode 1-D1 & D2 OFF When both the systems are supplying, S1 and C1 are connected in series to charge the inductor L2. Fig.4.Mode 2- D1 & S2-OFF In mode 2, it is clear that D2 provides path for inductor L2. Energy stored in C1 is transferred to L2 and solar charges the inductor L1. Fig.5.Mode 3-S1&D2 OFF In mode 3, L1 and C1 are connected in series. Energy stored in L2, wind source capacitor is transferred to C2. 26

3 Fig.6. Mode 4-S1 &S2-OFF In mode 4, both the diodes D1, D2 are connected to charge inductor L1, L2. 3. SIMULATION RESULTS The Simulation results of the above proposed converter are given below. The fig.7 shows the output voltage across the load. The figures 8,9,10 and 11 show the voltage across the switch S1, Switch S2, Inductor L1 and Inductor L2 respectively. Fig.7.Output Voltage across the Load Fig.8.Voltage across the Switch S1 Fig.9.Voltage across the switch S2 Fig.10.Voltage across the inductor L1 27

4 4. HARDWARE IMPLEMENTATION Fig.11.Voltage across the inductor L2 Hardware implementation of the proposed Cuk-Buck Converter is done with the two sources each of 12 Volt. This section consists of Power Supply circuit, gate pulse generation circuit, Optocoupler circuit and Cuk-Buck converter circuit. They are explained in brief below Design of Power Circuit Hardware implementation is done for the power circuit. The components required for the design of power circuit is given below: Transformer 220V/12V,5A Bridge Rectifier 12V,5A Capacitor 1000 µf,50v Voltage Regulator 7812 Connecting wires Multimeter CRO Fig.12 shows the design of power circuit output. The 220V AC is stepped down to 12V AC with the help of step down transformer. The 12V AC is then converted to 12V DC with the help of diode bridge rectifier. Then it is filtered by capacitor and finally an output voltage of 12V DC is obtained across the voltage regulator. Figure 13 shows the output of power circuit in multimeter. Fig 12 Design of Power Circuit Fig.13.Power Circuit Design Showing Result Across Multimeter 28

5 4.2.Design of Cuk-Buck Converter The hardware of the Cuk-Buck Converter is shown below. The design consists of 12 volt power supply circuit for the cuk-buck converter, PIC 18 with 15 volt power supply for gate pulse generation and Optocoupler circuit to provide the generated pulse to the switches. The components required for the design of cuk-buck converter is given below: 12 Volt DC power supply, 2 Amps (Source 1) 12 Volt DC power supply, 5 Amps (Source 2) Optocoupler circuit with 15 Volt power supply PIC18F2550 with 5 Volt power supply Inductor L1 2mH Inductor L2 3mH Capacitor C µf, 100 Volt Capacitor C µf, 100 Volt MOSFET IRF840 Power diode Fig.14. Design of Cuk-Buck Converter The fig.14. Shows the design of Cuk-Buck converter in which the Mosfet switch is triggered by the pulses generated by the PIC controller. The pulses are made to trigger the switch through the Optocoupler circuit Gate Pulse Generation Fig.15.Gate Pulses for the Switches The fig.15 above shows the gate pulses for the switches S1 and S2 for 0.5 and 0.8 duty cycle respectively. The gate pulses can be generated by various methods like by using 555 timer, FPGA, PIC controller etc. Here the gate pulse is generated by using PIC controller. The PIC used here is 18F2550. This PIC 18 family of devices offer the advantage of high computational performance at an economical price - with an addition of 29

6 high endurance, enhanced flash program memory. In addition to these features, this family introduces design enhancements that make these microcontrollers a logical choice for many high performances, power sensitive applications. This device significantly reduces power consumption during operation. Fig.16.Gate Pulse Generation Circuit The fig.16 shows the gate pulse generation circuit in which the PIC controller is energised by the 5 volt power supply and the pulses generated from the PIC is given to the MOSFET through the Optocoupler circuit. The Optocoupler circuit is energised by 15 volt power supply Results The hardware results of the proposed Cuk-Buck converter recorded in DSO are given here. The fig.17. shows the output voltage of 112 volt for an input of source voltage 12V, 2Amps and 12V, 5Amps shown respectively in figures 18 & 19. Fig.17.Output voltage of 112 V Fig.18. First Source Voltage of 12 V Fig.19.Second Source Voltage of 11.9 V 30

7 Fig.20. Voltage across Switch S1. Fig.21.Voltage across Switch S2 Fig.22.Voltage across Diode D1 The figures 20,21,22,23 & 24 shows the voltage across the Switch S1, Switch S2, Diode D1, Diode D2 and Inductor L1 respectively. Fig.23.Voltage across Diode D2 Fig.24.Voltage across Inductor L1 31

8 5. CONCLUSION Renewable power sources can be used to reduce storage and fuel consumption in conventional telecom power systems. This thesis presents an integrated hybrid solar/wind energy converter for telecom power supply which uses grid only for back-up. The proposed system consists of a new dual input dc-dc converter for extracting power from renewable sources. The features of the proposed system are high efficiency and reduced component count, simple control and flexibility in power sharing. The hardware implementation of the proposed converter is done and the output is presented. REFERENCES [1] B.Mangu, K.Kiran Kumar and B.G.Fernandes, Efficiency improvement of Solar-Wind based Dual input converter for telecom power supply, EEIC, 11 th International Conference, pp , [2] B.Mangu, K.Kiran Kumar and B.G.Fernandes, A novel grid interactive Hybrid power supply system for telecom application, INDICON, Pg 1-5, Annual IEEE, [3] W.Margaret Amutha, Dr.V.Rajini, and V.Renugadevi Investigation of Efficiency of Dual Input Dc/Dc Converter, SEISCON, Proceedings of IET Chennai 4 th International Conference on Sustainable Energy and Intelligent System, [4] P.Neema, R.K.Nema and S.Rangnekar, Pre-feasibility Study of PVSolar/Wind Hybrid Energy System for GSM Type Mobile Telephony Base Station in Central India, in Proc. 2nd Int. Conf. on Computer and Automation Engineering,Vol. 5,No 2, pp , Feb [5] P.K.Panigrahi, A.G.Gulati and U.K.Srivastava, First report of the committee on Hybrid Wind/Solar Power for Rural Telephony- Green Solution to Power Problems, Department of Telecommunications, India. Nov [6] O.C.Onar, O.H.A.Shirazi and A.Khaligh, Grid Interaction of a Telecommunications Power System With a Novel Topology for Multiple- Input buck-boost Converter, IEEE Trans. Power Del.,Vol. 25, No. 4, pp , Oct [7] O.H.A.Shirazi, O.Onar and A.Khaligh, A Novel Telecom Power System, in Proc. Int. Telecommunications Energy conf., 2008, pp [8] H. Matsuo, T.Shigemizu, F.Kurokawa, and N.Watanabe, Characteristics of the multiple-input DC- DC converter, IEEE Trans. Ind. Electron.,Vol. 51, No. 3, pp , June [9] P.Bajpai, N.P.Prakshan and N.K.Kishore, Renewable Hybrid Standalone Telecom Power System Modelling and Analysis, in Proc. TENCON2009, IEEE Region-10 Conf.,pp [10] Y.C.Liu, and Y.M.Chen, A Systematic Approach to Synthesizing Multiple-Input DC/DC Converters, IEEE Trans. Power Electron.,Vol. 24, No. 1, pp , Jan [11] Y.Li, X.Ruan, D.Yang, F.Liu and C.K.Tse, Synthesis of Multiple- Input DC/DC Converters, IEEE Trans. Power Electron., Vol. 25, No. 9, pp , Sep [12] A.Kwasinski and P.T.rein, A Microgrid-based telecom power System using Modular Multiple- Input DC-DC Converters, in Proc. Int.Telecommunications Energy conf., 2005,pp [13] A.Naikodi, Solar-Wind Hybrid Power for Rural Indian Cell Sites, in Proc. Energy Con.,2010, pp [14] B.G., and Chapman, P.L., A multiple-input dc-dc converter, IEEE Power Electron. Lett., 2003, pp