IJIRST International Journal for Innovative Research in Science & Technology Volume 1 Issue 6 November 2014 ISSN (online): 2349-6010 Implementation Soft Switching Bidirectional DC- DC Converter For Stand Alone Photovoltaic Power Generation System M Swami Nathan. R Rajasakeran. M.E Student Assistant Professor Department of electronics and electrical engineering Department of electronics and electrical engineering Sri lakshmi ammaal engineering college, Chennai 73 Sri lakshmi ammaal engineering college, Chennai 73 Abstract In this paper hybrid storage system is proposed for the transient load management. Battery act as a primary source and supercapacitor act as a secondary source. This hybrid system is controlled by the canonical switching system designed in this converter. This proposed converter is derived simply adding switches in each leg. Zero voltage source is achieve for all the switches, by placing inductor in front of each switches. In this topology two unidirectional and two bidirectional power flow has designed for manage the power balance for this system. Circuit analysis and design consideration are proposed by the MATLAB modeling. Simulation results has verify by the close-loop design and confirm its ability to achieve independent control over power flow. The proposed converter reduced the component losses for to harvest from the renewable energy. Keywords: multi-input converters, battery, supercapacitor, ZVS, fuzzy controller. I. INTRODUCTION In all the counters, renewable energy based single energy storage system implementing for transient load demand. Due to this system indirectly increases the component cost and also reduces the overall efficiency of the system. Major drawback of SSS based standalone renewable energy systems are not suitable for transient load conditions. Bidirectional DC DC converter is designed to power management between supercapacitor, battery, source and load. Control and power management algorithm is developed based on the load voltage. Where supercapacitor, batteries are connected to bidirectional port and source to load are connected to the unidirectional port. Storage devices SCs and batter are used for smoothing the power output, improving startup transitions and dynamic characteristics, and enhance the transient power capacity. So they are best placed in applications where high power levels are needed during a short period of time, from milliseconds to few hundreds of seconds. In this hybrid storage system has the ability to provide high quality and high efficient power. Traditional converters are replaced into multi-input converter (MIC), which combines different power sources in a simple power structure. This converter has providing the centralized control, bidirectional power flow for the storage element, high reliability, and reduce cost and size. The pulsating voltage source is supplied as a input for MICs. Besides, a systematic method to synthesize MICs is proposed. MIC has the ability to operating in different converter topologies and directional operation without any additional transformer. SOLAR PANNEL SCAP DC/DC BIDIRECTIONAL CONVERTER BATTERY CONTROLLER SINGLE SOURCE MULTILEVEL INVERTER AC LOA D All rights reserved by www.ijirst.org 298
Fig. 1: Block Diagram of MICs A P&O power management algorithm is realized to achieve maximum power point tracking (MPPT) of the PV source. This paper is organized as follows. The converter structure and operation modes are explained in Section II. Section III describes the control system of the proposed converter. Section IV determines the operation mode. Section V represents the simulation and experimental verifications and Section VI concludes this paper. II. CONVERTER STRUCTURE AND OPERATION MODES The Structure of Proposed DC-DC bidirectional Converter topology is represented in fig 2. This converter interface two storage elements SCs, battery and a PV source. In this topology is suitable alternative for hybrid storage system. Nearly same voltage level all the ports are designed in this topology. By this construction the power management is lossless. Fig. 2: Circuit of DC-DC Bidirectional Converters Consist of full bridge inverter or rectifier on the load side to drive the AC load. this circuit consist of nine switches where Si1, Si2, Si3, Si4 are the inverter connected switches, Sc1, Sc2 are the switches connected with the super capacitor, Sb1, Sb2 were connected to the battery and switch Ss is connected with parallel to the PV. Canonical switching cell structures are introduced in this converter. Full bridge converter for converting DC-AC and regeneration. Maximum power point tracking (MPPT) is achieved through switch Ss from the PV array. In this circuit consist of both boost and buck operation. When the Switches Sc1, Sb1 and Ss are in ON condition it will act as a boost converter. And Switches Sc2, Sb2 are in ON condition it act as a buck converter. These operations are also denoted as charging and discharging mode. III. MODES OF OPERATION A. Mode-1: Energy harvested from solar is equal to load, SuperCapacitor and Battery are Ideal. PV array generate power to equal to the load, boost operation from the PV array by the switch Ss in turn ON condition. Sd is the blocking diode to block the reverse powerflow to the PV. When switch Ss turn ON and turned OFF condition for charging and discharging the inductor L1. B. Mode-2: Energy harvested from solar is less than the load and Steady State Operation Solar PV panel and Battery are Share the load Super Capacitor is Ideal. When the PV generated power is less than the load then switches Sb1 turned ON to discharge power stored in the battery to compensate to the load. When switch Ss, Sb1 is turned ON for boost operation. For Steady State Operation Solar PV panel and Battery are Share the load. Switches Sc1,Sc2 turned OFF condition. C. Mode-3: Energy harvested from solar is less than the load and Transient Load Solar PV panel, Supercapacitor and Battery are Share the load. When the load initial source power start is required more than the steady state operation. On this condition dynamic power required to the load, switch Sc1 turned ON to discharge the energy from the supercapacitor. In this condition Ss, Sb1,Sc1 are turned ON and boost operation takes place. D. Mode-4: ENERGY harvested from solar is greater than the load and Load is steady state Solar PV panel is operating load and battery is charging Supercapacitor is ideal. When PV generated energy is more than the load then the energy is stored to the battery with the buck operation. When switch Sb2 is in ON condition. Supercapacitor is in ideal condition. All rights reserved by www.ijirst.org 299
E. Mode-5: Energy harvested from solar is greater than the load and Load is transient Solar PV panel is operating load and supercapacitor is charging Battery is ideal. PV array generated energy is more than load. When the battery is charged then the supercapacitor will be charging. Switch Sc2 will be turned ON condition. F. Mode-6: Energy is harvested from solar and No load Solar PV energy is transferred to supercapacitor and Battery. When in the no load condition PV array generated energy will be stored in the battery and supercapacitor. Switches Sc2 Sb2 were turned ON and Sc1 and Sb1 were turned OFF condition. Fig. 3: Source To Load Fig. 3: Battery Discharging Fig. 4: Battery and Super Capacitor Discharging Fig. 5: Battery charging All rights reserved by www.ijirst.org 300
Fig. 6: Super Capacitor Charging Fig. 7: No Load Condition IV. CONTROL ANALYSIS Fuzzy controller is implemented inthis proposed system. In the membership function edition of input and output status were aliened by in the triangle waves. In the input membership function has the three triangle waves, which has denotes the membership function points are Low, High, Normal. Where the input membership function parameters [0 10 420], [-50.32-10.32 29.68], [-40 0 30.03], [-111 69.05 249]. Then the output membership function has the two triangle waves, which has denotes membership function points are ON and OFF. Where the output membership function parameters [-0.199 0.201 0.5595], [-0.2413 0.1587 0.5587], [-0.2704 0.1296 0.5296], [-0.4 0 0.4537], [-0.2624 0.1376 0.5376]. Rule is defined as the making the decision to the controller it know as rule base or knowledge base system. For the designed controller formed rules were given below. The ripple power in the three phase system. P P sin(2 t) r r_peak Depending on the ripples the output has some disturbances. The output voltage is adjustable based on the duty cycle of the transistor. Fig. 8: Rule Editor All rights reserved by www.ijirst.org 301
V. SIMULATION RESULT The input voltage of the photovoltaic cell is energy 84V and DC bus voltage is 410 volt. AC induction motor is connected to full bridge inverter and battery and supercapacitor voltages are fixed based on the load voltage. The fuzzy logic interference is imbued in this simulation, for control the various modes of operation. Fig. 9: Proposed Converter Simulation A. Matlab Simulation Result 1) Source Waveform: The simulation input voltage, which is measured across the input side by connecting a voltage measurement with scope bus voltage is 416.9-416.57V, RMS voltage 416V, solar voltage 400V, solar current 0.8A. Fig. 10: Result of The Input 2) Battery Paramete: In this simulation battery voltage and current parameters are determined. When the battery current is inverse to the battery voltage. And battery SOC parameter vary to.2 values. Fig. 11: Battery Waveform All rights reserved by www.ijirst.org 302
3) Supercapacitor Parameter: In this simulation supercapacitor voltage and current parameters are determined. When the supercapacitor current is inverse to the supercapacitor voltage. And supercapacitor SOC parameters vary to.2 points. Dynamic variation is identified. Fig. 12: Super Capacitor Waveform 4) Variable Load Waveform: The simulated output for the variable load with the distraction is measured across the load side by connecting the voltage and current measurement with scope. Fig. 13: Result of the Variable Load 5) Load Output: The simulated output and input voltage, which is measured across the output of motor load by connecting a voltage measurement and current measurement with scope. For the three phase output are given, load voltage has the disturbances are shown. The simulated output and input voltage, which is measured across the output of motor load by connecting a voltage measurement and current measurement with scope. For the three phase output are given, load voltage has the disturbances are shown. Fig. 14: Result of the Motor Load All rights reserved by www.ijirst.org 303
VI. CONCLUSION The proposed converter is applied to hybridize a pv, an scs, and a battery storage system. Energy storage has to be used in the system to provide the energy when the energy from these renewable energy sources is low and supply when the energy from these energy sources is high. In order to increases the lifecycle and dynamic behavior of the system supercapacitor and battery hybrid system is proposed. To integrate different storage devices, a new multi-port dc-dc power converter is proposed because of the better performance, lower cost, higher efficiency and system-level control. Also under wide range of different operating points, including normal load, large load, small load, even no load, the system can remain stable and controlled. As the simulation results show, the converter control system provides good transient and steady state operation for the converter with different step changes in the PV power generation and the load condition. The simulation results are verified by a low power range. The proposed converter has the merits of making use of low-voltage batteries, working in stable margin operating points. Meager advantage is bidirectional power flow to the storage port, simple structure, and low-power components. REFERENCES [1] A. Khaligh, J. Cao, and Y. Lee, A multiple-input DC DC converter topology, IEEE Trans. Power Electron., vol. 24, no. 3, pp. 862 868, Mar. 2009. [2] A.Kwasinski, Identification of feasible topologies formultiple-input DC DC converters, IEEE Trans. Power Electron., vol. 24, no. 3, pp. 856 861, Mar. 2009. [3] Farzam Nejabatkhah, Saeed Danyali, Seyed Hossein Hosseini, Mehran Sabahi,and Seyedabdolkhalegh Mozaffari Niapour, Modeling and Control of a New Three-Input DC DC Boost Converter for Hybrid PV/FC/Battery Power System IEEE transactions on power electronics, vol. 27, no. 5, may 2012 [4] F. Baalbergen, P. Bauer, and J. A. Ferreira, Energy storage and power management for typical 4Q-load, IEEE Trans. Ind. Electron., vol. 56,no. 5, pp. 1485 1498, May 2009. [5] G. Su and L. Tang, A reduced-part, triple-voltage DC-DC converter for EV/HEV power management, IEEE Trans. Power Electron., vol. 24, no. 10, pp. 2406 2410, Oct. 2009. [6] H. Krishnaswami and N. Mohan, Three-port series-resonant DC DC converter to interface renewable energy sources with bidirectional load and energy storage ports, IEEE Trans. Power Electron., vol. 24, no. 9 10, pp. 2289 2297, Oct. 2009. [7] Mamadou Baïlo Camara, Hamid Gualous, Frederic Gustin, Alain Berthon,and Brayima Dakyo, DC/DC Converter Design for Supercapacitor and Battery Power Management in Hybrid Vehicle Applications Polynomial Control Strategy IEEE transactions on industrial electronics, vol. 57, no. 2, february 2010 [8] M. B. Camara, H. Gualous, F. Gustin, and A. Berthon, Control strategy hybrid sources for transport applications using supercapacitors and battery, in Proc. IEEE, IPEMC, Shanghai, China, Aug. 13 16, 2006,vol. 1, pp. 1 5. [9] N. D. Benavides and P. L. Chapman, Power budgeting of a multiple input buck-boost converter, IEEE Trans. Power Electron., vol. 20, no. 6, pp. 1303 1309, Nov. 2005. [10] Y. Liu and Y. M. Chen, A systematic approach to synthesizing multi input DC DC converters, IEEE Trans. Power Electron., vol. 24, no. 2, pp. 116 127, Jan. 2009. All rights reserved by www.ijirst.org 304