Implementation and Design of Advanced DC/AC Inverter for Renewable Energy

Transcription

1 International Journal of Electrical Energy, l. 3, No., March 2 Implementation and Design of Advanced DC/AC Inverter for Renewable Energy Ergun Ercelebi and Abubakir Aziz Shikhan Electrical and Electronic Engineering, Gaziantep University, Turkey {ergun.ercelebi, abubakir.aziz}@gmail.com fast speed, making very high sampling rate possible for digitally-controlled inverters [4]. The AC output voltage could be constant or variable frequency and voltage. This conversion can be achieved either by controlled turn on and turn off electronic switch (e.g. MOSFET, IGBT and BJT, etc.) or by forced commutated thyristors, depending on application. In the ideal inverter the output voltage waveform of should be sinusoidal []. Fig. is over all diagram of synchronous dc-ac inverter. The related works; Have used a Matlab Simulink model of a single-phase full bridge 2kVA ltage Controlled ltage Source Inverter in [6]. Development of control circuit for single phase inverter using ATMEL microcontroller Proposed in [3]. A new dc to dc boost converter using closed loop control proportional Integral (PI) and Derivative (D) mechanism for photovoltaic (PV) standalone high voltage applications presented in [7]. Designed a boost converter that was able to boost up a variable DC voltages to a controlled DC voltage with desired output voltage value proposed in [8]. A multi-input single-phase gridconnected inverter for a hybrid photovoltaic (PV)/wind power system Proposed in [9]. In this paper I designed, simulated and implemented experimentally a 6W DCAC converter, which take from a photovoltaic solar panel model vary from (9-6) lt and constant output voltage of according set point reference (Vref) from (-8) lt. Abstract An inverter is a major component of standalone solar photovoltaic (PV) system for combining with photo voltaic or battery. In this paper 6W high efficiency (%9) advanced inverter relevant to PV system has been designed and implemented. the system consist of two parts; the first is the synchronous DC-DC boost converter with variable input voltage from 9V to 6V and constant DC voltage of 8V,and second is a DC-AC inverter (voltage source inverter). The sinusoidal bipolar SPWM is used for triggering the gates of the inverter bridge. The dspic6f877a microcontroller type is used for the implementation of the inverter system. The MATLAB Simulink environment is used for simulation the system. The simulation and experimental results show the stable operation and the results obtained satisfy the system. Index Terms MATLAB Simulink, converter, dc/ac inverter I. INTRODUCTION The classical power systems such as big power generation plants are located at sufficient geographical locale produce most of the electrical power, which is then transferred to large consumption centres over long distance transmission lines. The system control centres observe and regulate the power system continuously to ensure the quality of the power, rated voltage and frequency. But, now the complete power system is changing, a large number of generation units, including both non-renewable and renewable sources such as wind turbines, wave generators, photovoltaic (PV) generators, are being developed, and installed. A wide-spread use of renewable energy sources in distribution networks and a high breakthrough level will be seen in the near future many places []. The dc-ac converter, also called as the inverter, converts dc source to ac source at desired output voltage and frequency according the system. The dc power input to the inverter is obtained from a present power supply network or from a rotating alternator through a rectifier or a battery fuel cell, photovoltaic array, or magneto hydrodynamic generator [2], [3]. PWM control is the robust technique that offers a simple process for controlling of analog systems with the processor s digital output. With the availability of minimum cost high performance DSP chips characterized by the execution of most instructions in one instruction cycle, intricate control algorithms can be executed with Figure. Over all diagram of synchronous dc-ac inverter II. The synchronous boos DC-DC converter is used to obtain a constant output voltage with variable input voltage. It s mainly used to the stabilization dc power supplies. The average output voltage of converter is always larger than the input voltage. The switching duty cycle controlled the output voltage of converter. When the switch is ON, the diode is reverse biased, and hence isolates the output stage of converter. During the switch ON the inductor gets the energy from the source and Manuscript received January, 2; revised May 8, 2. 2 International Journal of Electrical Energy doi:.72/ijoee DC-DC BOOST CONVERTER 32

2 International Journal of Electrical Energy, l. 3, No., March 2 42µH and 94μF respectively. stores it. During switch OFF case, the diode is forward biased and the output side receives the storage energy from the inductor as well as the input. Thus the energy transferred to the output from input is always greater in a given switching cycle. The ratio of output voltage to input voltage is given by; VO VI D () where, and are the input and output voltages of the boost converter, respectively, and D is the duty ratio and defined as the ratio of the on time of the switch to the total switching period [], []. The Maximum duty cycle D Figure 2. MATLAB simulation synchronous boost converter (min) ut (2) Control design for a boost PWM converter involves two steps: choice of modulation strategy, which corresponds to an open-loop boost converter control, and design of dynamic closed loop control. The instantaneous voltage control scheme is applied to the proposed circuit. The block diagram is shown in Fig. 3, of the control circuit. The output voltage is compared with a reference voltage Vr. Hence, the control scheme is simple compared with others. The classic PI (proportional-integral) controller has been used in many industrial control systems, mainly due to its simple structure that can be easily understood and implemented in practice, and its excellent flexibility made possible by adjustment of the coefficients KP, and KI [6], [7]. where, VIN (min), VOUT, and, η are the minimum input and output voltages and η is efficiency of the converter estimated 9%. The Inductor Ripple Current Estimation: IL (.2to.4) ut(max) ut (3) where, D, fs, ΔIL, IOUT(max) are duty cycle, minimum switching frequency of the converter, inductor ripple current and maximum output current necessary respectively. The maximum switch current: Isw(max) IL ut(max) 2 D (4) Inductor Calculation: (L is selected inductor value): L (ut ) IL Fs ut () Output Capacitor Selection, The maximum output voltage ripple ΔVOUT, (Δut=desired output voltage ripple) []. (6) ut. ut Cout (min) ut(max) D Fs ut (7) A. Simulation Model for Boost Converter The converter is designed using one MOSFET, antiparallel diode, rectifier diode, inductor and capacitor with the PI feedback control in Simulink. The MATLAB Simulation of synchronous DC-DC boost converter is shown in Fig. 2. The inductance and capacitance are Figure 3. MATLAB simulation PI controller feedback and set point (a) 2 International Journal of Electrical Energy 33

3 International Journal of Electrical Energy, l. 3, No., March 2 (b) Figure 4. Overall diagram dc-dc converter B. The Implemental DC-DC Booster The schematic diagrams for the Prototype synchronous dc-dc boost converter circuit shown in Fig. 4a and Fig. 4b respectively. The feedback controller concludes UC3843 used current mode controller and LM38 operation amplifier, and output port 6 of UC3843 fed the MOSFET. In the power circuit of Fig. 4, the input capacitor μf and output capacitor tow 47μF connected in parallel to decrease the ESR (equivalent series resistance). The prototype synchronous boost converter is shown in Fig.. TABLE I. SHOWS THE RECORDED OUTPUT VOLTAGE WITH VARY REFERENCE VOLTAGE (SET POINT) III THE INVERTER A. Simulation Model of PWM Inverter The single-phase full bridge inverter is constructed using 4 IGBT switches and 4 anti-parallel diodes in Simulink. In the model, sinusoidal wave at -Hz and carrier wave are compared to generate PWM signals. PWM inverter uses self-commutating IGBT solid-state power electronic switches. The switching frequency of the inverter is 2KHz. The single-phase inverter is fed from Vsynchronous boost converter. LC filter blocks high frequency harmonics caused by DC to AC conversion to reduce distortion in the output harmonic. The inductance and capacitance of the filter is mh and 47μF respectively and non-leaner load Ω mh is used. The Simulink model is shown in Fig. 6. Figure. Photograph DC-DC synchronous boost converter Table I lists the recorded output voltage. The dc output voltage is measured by ltmeter, with varying input voltage and is found to be constant according set point. Figure 6. The simulation model full bridge inverter 2 International Journal of Electrical Energy

4 International Journal of Electrical Energy, l. 3, No., March 2 ut.2 B. The Experimental Implement of The PWM Inverter The schematic diagrams for inverter, as shown in Fig. 7, which is consist of power circuit and control circuit. The PIC microcontroller6f877a is used to generate the required SPWM signals to drive and switch the fullbridge IGBTs switches, SPWM and output ports are used for the implementation. The four PWM signals have been fed to the optocoupler (NPN 4N2) for the isolation of gate drivers. Four discrete IGBTs (G4PC3UD) are used as switching devices MOSFET Trigering Figure 8c. 36V set point voltage Figure 7. The implementation full bridge inverter IV. SIMULATION AND EXPERIMENTAL RESULTS Figure 9. V set point voltage The simulation results obtain from the Matlab Simulink DC-DC converter and DC-AC inverter model developed and that were compared with experimental results for the 6W inverter are shown Fig. 8-Fig.. V inverter ut I load MOSFET Triguring Figure. Dc-Ac inverter without fillter inmatlab simulation Figure 8a. set point voltage ut MOSFET Trigering Figure. Dc-Ac inverter without fillter practical Fig. 8a, Fig. 8b and Fig. 8c show the output voltage, pulses, output current and input current for input voltage V, 36V, V respectively. Fig. 9 shows the experimental result. Fig. and Fig. show the output voltage and current of the inverter for the simulation result and experimental result without the filter and Fig. and Fig. 3 show the output voltage and current with LC filter Figure 8b. set point voltage 2 International Journal of Electrical Energy 3

5 International Journal of Electrical Energy, l. 3, No., March 2 [4] M. Tümay, K. Ç. Bayindir, M. U. Cuma, and A. Teke. (24). Experimental setup for a DSP based single-phase PWM inverter. [Online]. Available: [] R. Senthilkumar and M. Singaaravelu. Design of single phase inverter using dspic3f43, International Journal of Engineering Science and Technology, vol. 2, no., pp. 666, 2. [6] A. B. Sankar and R. Seyezhai, MATLAB simulation of power electronic converter for PMSG based wind energy conversion system, International Journal of Innovative Research in Electrical, Electronics, Instrumentation and Control Engineering, vol., no. 8, Nov. 23. [7] D. S. Karanjkar, et al., Performance analysis of fractional order cascade controller for boost converter in solar photo-voltaic system, in Proc. International Conference on Engineering, Dec. 2, pp. -6. [8] J. Faiz and G. Shahgholian, Modeling and simulation of a threephase inverter with rectifier-type nonlinear loads, Armenian Journal of Physics., vol. 2, no. 4, pp , Sep. 29. [9] R. Arulmurugan and N. S. Vanitha, Optimal design of DC to DC boost converter with closed loop control PID mechanism for high voltage photovoltaic application, International Journal of Power Electronics and Drive Systems (IJPEDS), vol. 2, no. 4, pp , Dec. 2. [] K. H. Mohamed, T. B. Ibrahim, and N. B. Saad, Boost converter design with stable output voltage for wave energy conversion system, International Journal of Information Technology and Electrical Engineering, vol. 2, no., Feb. 23. [] Y. Yang, et al., Multi-Input single-phase grid-connected inverter for hybrid PV/wind power system, International Journal of Renewable and Sustainable Energy, vol. 3, no. 2, pp. 3-42, Feb. 24. [] B. Hauke. Basic calculation of a boost converter s power stage. [Online]. Available: I load Time Figure. Dc-Ac inverter with LC fillter in MATLAB simulation Figure 3. Dc-Ac inverter with LC fillter practical V. CONCLUSION This paper presented the simulation model using Simulink-Matlab and an implementation experimental design prototype for DC-AC converter. The simulation results show the ability of the controller to obtain the constant output voltage for boost converter at different input voltage. Also the inverter simulation shows that the AC voltage obtained is approximately sinusoidal waveform. The experimental results and simulation results are very close to the others. Ergun Ercelebi received B.S. degree in Electrical and Electronics Engineering from METU, Gaziantep, Turkey in 99 and M.S. and Ph.D. degrees in Electrical and Electronics Engineering from University of Gaziantep in 992 and 999 respectively. He was the head of Computer Engineering, University of Gaziantep between 23 and 24. He is presently Professor and head of dept of electrical electronics department, University of Gaziantep. His research interests include speech processing, image processing, adaptive filters, neural networks, statistical signal processing wavelet. REFERENCES [] [2] [3] IOV, et al., Power electronics and control of renewable energy systems, in Proc. 7th International Conference on Power Electronics and Drive Systems, 27, pp P. Bhangale, P. Sonare, and S. Suralkar, Design and implementation of carrier based sinusoidal PWM inverter, International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, vol., no. 4, Oct. 2. B. Ismail, et al., Development of control circuit for single phase inverter using Atmel microcontroller, in Proc. International Conference on Man-Machine System, International Journal of Electrical Energy Abubakir Aziz Shikhan received B.Sc. degrees in Electrical Engineering from Technical College, MOSUL, IRAQ, in 23 and 27, now master student in electric and Electronic Engineering Gaziantep University. During 27-23, he stayed in machine and power electronics Laboratory, electric department in technology institute, Ministry of higher education and scientific research of Erbil, Iraq. 36