Modeling and Simulation of Neutral Point Clamped Multilevel Inverter ...

IEEE - International Conference on Advances in Engineering and Technology-(ICAET 2014)

Modeling and Simulation of Neutral Point Clamped Multilevel Inverter for Solar Photovoltaic System Nikhil Kumar [email protected]

Deepak Verma [email protected] Department of Electrical Engineering, Maulana Azad National Institute of Technology Bhopal M.P. India

Abstract-Now a day’s multilevel inverters have become more popular with less disturbances and they can function at lowerswitching frequencies than ordinary two-level inverters. This paper presents modeling of neutral point clamped multi level inverter for solar photovoltaic (PV) system as it is the most reliable renewable energy source. In this paper mathematical model of PV system have been presented and study of its performance have been done under varying climate and load condition so as to implement for real time applications also the PV model has been connected with MultiLevel inverter (MLI) and the results for three level, five level, seven level, nine level and eleven level are presented. Models have been developed for different level of inverter in MATLAB to achieve this purpose.

Index Terms— modeling of PV array; neural point MLI; Solar simulator; THD I. INTRODUCTION All Renewable and sustainable energy sources such as photovoltaic (PV) and fuel cells (FC) require power electronic conditioning. Increasing demand of energy has been created a major dispute in developing country. As the conventional sources of power generation were creating environmental issues like “Green House Effect” or “ Global Warming “ Recently, the installation of PV generation systems is rapidly increasing due to concerns related to environment. Photovoltaic is gaining popularity during the last several years as a free and promise renewable energy source. The main disadvantages of PV energy system are the high cost of manufacturing of silicon solar panels and lower efficiency. With the latest techniques of manufacturing crystalline design, it is possible to make the PV system cost effective. The development of cost effective power conversion instrument for PV energy will have much impact in the future. Out of all renewable energy sources solar energy has been emerged as one of the best source of energy supplier, as solar energy is clean, green, environmental friendly and inexhaustible. Globally fossil fuel are the main source of power generation .That is the reason why the cost of generation is less as compare to other and many power plants are dependent on fossil fuels. Though numbers of solar plants are less which is connected to the grid, so they are getting more attention in the fast growing country like India, Germany, Japan. Two major utility in solar system are grid connected and standalone systems.

Suresh K. Gawre [email protected]

The PV system directly converts the incident sun light into direct current electricity. Normally the voltage generated by PV cell is very low which cannot be used for any consumer load. For achieving high voltage many cells should be connected in series and for achieving reasonable current cells should be connected in parallel. Alternating current is required for domestic and industrial application hence generated dc power should be converted in to ac for the utilization at end utility. Generally Solar panels are designed in such a manner to have output voltage of about 23-38 V at maximum power point (MPP) and rated power around 160 W at a radiation level of 1000 W/m2. In the next stage solar panels are connected to DCDC converter. This stage is also responsible for tracking the maximum power with the help of maximum power point algorithm and keeping the output remain synchronized with loads. [1] Due to this reason power electronics devices have been become an indispensable part for renewable energy systems (RES). So for obtaining desired voltage level, boost converter employed which increases the generated solar panels voltage and inverter converts the DC in to an AC. Another methods can be use as Multilevel Inverter (MLI)[2] Solar simulator can be used as testing for any maximum power point algorithm or Power-Voltage (P-V) or Voltage Current (V-I) or any characteristic of PV solar panel in any weather condition. Before stepping towards power electronics system, it is required to think about the PV panels design corresponding to load. Based on the assigned load it required to decide what will be the numbers of cells required to be connected in series or parallel as per the requirement. So the requirement of PV simulator is essential to evaluate the performance of PV system along with electronics devices under various environmental conditions. The power electronics can be used in this work i.e. MLI as MLI replace the use the conventional two level inverter which reduce total harmonic distortion (THD) that is reason why it is being more popular now a days. There are many Multi Inverter Topologies are being used. In this paper Neutral Clamped Inverter topology have been adopted. This results in increase deficiency and reliability. This paper mainly focus on modeling and simulation PV system using Matlab/Simulink and the output PV is fed to

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IEEE - International Conference on Advances in Engineering and Technology-(ICAET 2014)

NPCMLI and response have been presented for nine level and eleven level. Results shows that NPCMLI is the most preferred topology for PV system. II. MODELLING OF PV SYSTEM PV arrays can be build with the help of series and parallel combination of solar cells, which can be simply represented by the electrical equivalent circuit model such as one given in the following figure(1),

Fig. 2. Experimental setup of PV

III. EXPERIMENTAL VALIDATION OF SOLAR CELL CHARACTERISTIC Fig. 1. Electrical equivalent circuit of a PV cell

The output of PV cell is a function of photon current that can be also determined by load current depending upon the solar insolation during its operation equation. 1

1

1

Where: C), e: Electron charge (1.602 10 k: Boltzmann constant, I: Cell output current, A, Iph: Photon generated current, Io: Reverse saturation current for diode D, Io2: Reverse saturation current for diode D2, Rs: Series resistance of cell, Rsh: Shunt resistance of cell, V: Cell output voltage, VT : Thermal voltage = VT=(Ns*N*k*T)/q , T: cell operating temperature, q: Charge on an electron, N: Diode emission coefficient or quality factor of the diode D, N2: Diode emission coefficient or quality factor of the diode D2. Thus PV panel output is dependent on solar insolation and temperature. A two diode model has been given in MATLAB in ‘SIMSCAPE’ library and results or characteristic of solar cell have been obtained by simulation under different irradiation and temperature. The behavior of solar module can also verify by the experimental setup given in fig.2.

The modeling of PV pannel has been done by using two diode model and one simulator has been employed for the study of and IV (Current versus Voltage) and PV (Power versus Voltage) characteristic under various environmental condition. An experiment has been conducted with the help of solar simulator designed and developed by Western Regional Instrumentation Centre, University of Mumbai and IIT bombay shown in fig. 3.

Lamp Control

Fan

4 Quadrant Supply Heater Ammeter Temperature Controller Potentiometer

Voltmeter Power Switch

Fig. 3. Solar Simulator

By the help of solar simulator different characteristic of solar cell can obtained like IV characteristic and PV characteristic for different insolation, for different operating temperature. The specification of solar cell used in solar simulator is given in table I Standard test Condition: Insolation 1000 W/m2 at 250C Voc 600 mV Isc 490 mA Solar cell area 16 cm2

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IEEE - International Conference on Advances in Engineering and Technology-(ICAET 2014)

Fig. 8 shows IV Characteristic of Solar Cell with 1000 W/m2 insolation at temperature equals to 00C, 300C and 600C 0.55

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Fig. 8. IV characteristic of solar cell at different temperature

Fig. 4. Solar Simulator Fig.5 shows the IV and PV characteristic of solar cell which is also verified by the experiment on solar simulator

Fig. 9 shows PV Characteristic of Solar Cell with 1000 W/m2 insolation at temperature equals to 00C, 300C and 600C and constant solar insolation i.e 1000 w/m2. 0.35

Power Current

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Fig. 5. IV and PV characteristic

Fig. 9. PV Characteristic of solar cell at different temperature

Fig. 6 shows IV Characteristic of Solar Cell with different insolation at 250C 0.5

1000 w/m2 0.45

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The volatge of the cell decreses as the temperature increases proportionaly and. short circuit current will be decreasing logrithmically. As from the IV Characteristic, solar cell can be modeled as Current source because about 70-80% of its characteristic is similar to that of current source of DC type. Hence for the AC load the output of the cell (or pannel) should be inverted that can be done by either conventional two level inverter or by multilevel inverter. Here in this paper DC to AC convertion is done by Nutral point clamped multi level inverter.

Current (Amp)

IV. INTERFACING OF SOLAR CELL WITH NEUTRAL POINT CLAMPED MULTILEVEL INVERTER

Fig. 6. IV Characteristic of solar cell

Fig. 7 shows PV Characteristic of Solar Cell with different insolation at 250C 0.25

1000 w/m2 25 0 C

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Fig. 7. PV characteristic of solar cell

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In this paper simulation for three, five, seven, nine and eleven level Multilevel inverter, have been done and results has shown. Interface between PV pannel and Nutral Point Clamped Multilevel Inverter (NPCMLI) have been shown in the fig. 10 for three level inverter. The output of inverter will contain three level shown in fig. 12. This circuit have many advantages like simple, improved waveform due to this it will reduce the total harmonic distortion. Because solar cell given in the SIMSCAP library of MATLAB that’s why it gives output in the form of physical signal to convert physical signal into the simulink signal ‘physical signal to simulink converter’ used which convert physical signal into unitless simulink signal.

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IEEE - International Conference on Advances in Engineering and Technology-(ICAET 2014)

Fig. 10. Matlab simulation model of 36 solar cell connected in series, interfaced with 3 three level neutral point clamped inverter

As the number of level increases, it will be more close to the sinusoidal waveform hence it will reduce the total harmonics distortion and also reduce the smaller harmonics hence it will reduce the cost and size of filter as the number of switches will be increasing it will reduce the rating of switches as compare to the conventional inverter of same power due to its modular structure [3]. PV is connected to NPCMLI having different output level. For switching Sine Pulse Width Modulation Technique has been employed in which Phase Opposition Dispossion (POD) carrier scheme used. The output voltage for three five seven nine and eleven level are shown in fig. 11, fig. 12, fig. 13, fig. 14 and fig. 15 respectively.

Fig. 13. Output Voltage of PV fed 7 level NPCMLI

Fig. 14. Output Voltage of PV fed 9 level NPCMLI

Fig. 11. Output Voltage of PV fed 3 level NPCMLI

Fig. 15. Output Voltage of PV fed 11 level NPCMLI

V. CONCLUSION

Fig. 12. Output Voltage of PV fed 5 level NPCMLI

Renewable energy sources are the promising energy source among the existing resources of energy out of which solar PV is most popular due to its significant advantages over other type of renewable energy resources. PV system has been modeled in the matlab and the obtained results have been compared with the experimental set up, solar simulator. It is the proof that the results obtained from the model works in the similar manner to that of real solar cell. PV panel has been simulated and its characteristic is explored.

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PV panel has been interfaced with Neutrral Point Clamped Multi level inverter. Carrier based PWM teechnique has been applied. As the number of level increases in response the number of switches also increases. It havingg the advantage of reduced harmonics, switching losses, lower rating r for switches, reduction in THD reduced size and cost of fillter. So application where high power required it serves as a goood topology to be interfaced. REFERENCES [1] A. Chitra, S. Himavathi “Modeling and a Experimental validation of Solar PV system for Cascade H-Bridge H Multilevel Inverter”, International Conference on Poower, Energy and Control (ICPEC). pp. 260- 265, 2013. [2] R.G.G. Raju, N.P Subramaniam, “Operatioon and modeling of photovoltaic power generators” , IEEE CONFE ERENCE on Recent Advances in Space Technology Services annd Climate Change (RSTSCC) VOL. 55, NO. 7, pp. 466- 469, 20010. [3] J. Rodriguez, S. Bernet, P.K. Steimer, I.E Lizama, L “A Survey on Neutral-Point-Clamped Inverters Volum me: 57 Issue: 7, pp. 2219- 2230, 2010. [4] Jih-Sheng Lai, Fang ZhengPeng, “Multiilevel inverters: a survey of topologies, controls, and appplications” IEEE Transaction on Industrial electronics,Volumee:49 pp. 724- 738 , 2002. [5] F. Bouchafaa, D. Beriber, M.S Boucheriit, “Modeling and control of a gird connected PV generatiion system” IEEE Transaction on Industrial electronics , pp 3155- 320, 2010. [6] M. Kaliamoorthy, R.M. Sekar, R. Rajaram m, “A new singlephase PV fed five-level inverter topologyy connected to the grid” IEEE International Conference onn Communication Control and Computing Technologies (ICC CCCT) , pp. 196203, 2010. [7] L. G. Franquelo, J. Rodriguez, J. I. Leon, S. Kouko, R. Portillo, and M. A. M. Prats, “The age of multilevel converters c arrives,” IEEE Ind. Electron. Mag., vol. 2, no. 2, pp. 28–39, 2 Jun. 2008. [8] J. Kwon, et al. "Photovoltaic Power Conditiooning System With Line Connection", IEEE T Transactions on Industrial Electronics, vol. 53, no. 5, pp. 10448-1054, 2006. [9] G. Carrara, S. Gardella, M. Marchesoni, R. Salutari, S G. Sciutto, “A New Multilevel PWM method: A Theoretical Analysis,” IEEE Trans. Power Electronics., vol. 7, no. 3, pp. 497 - 505, July. 1992. [10] V. G. Agelidis, D. M. Baker, W. B. Lawrancce, C. V. Nayar, “A Multilevel PWM Inverter Topology for Photovoltaic Application,” in Proc. IEEE ISIE’97, Guuimaraes, Portugal, 1997, pp. 589-594. [11] Muhammad H. Rashid, Power electronics: Circuits, Devices, H 2004, pp.267. and Applications, 3rd ed. Pearson Prentice Hall, [10] Esram T, Chapman P.L, “Comparisoon of Photovoltaic Array Maximum Power Point Tracking Techniques,” T IEEE Trans. Energy Conversion, vol. 22, no. 2, pp. p 439- 449, June 2007. [12] Femia N., Petrone G., Spagnuolo G., Vitellli M: “Optimizing duty-cycle perturbation of P&O MPPT technique” Power Electronics Specialists Conference, 2004. PE ESC 04. 2004 IEEE 35th Annual Volume 3,20- 25 June 2004 pp. 1939 - 1944 Vol.3 [13] Liu X., Lopes L.A.C.: “An improved perturbation and observation maximum power point trackingg algorithm for PV arrays” Power Electronics Specialists Conference, 2004. PESC 04. 2004 IEEE 35th Annual Volume 3, 200-25 June 2004 pp.

2005 - 2010 Vol.3. [14] S.. Kouro, J.. Rebolledo, J. Rodriguez, "Reduced SwitchingFrequency-Modulation Algorrithm for High- Power Multilevel Inverters," IEEE Trans. on Inndustrial Electronics, vol. 54, no. 5, pp. 2894-2901, Oct. 2007. [15] S. J. Park, F. S. Kang, M. H. Lee, C. U. Kim, “A New SinglePhase Five-Level PWM Innverter Employing a Deadbeat Control Scheme,” IEEE Tranns. Power Electronics., vol. 18, no. 18, pp. 831-843, May. 2003. [16] L. M. Tolbert, T. G. Habeetler, “Novel Multilevel Inverter Carrier-Based PWM Metthod,” IEEE Trans. Industry Application., vol. 35, no.5, ppp.. 1098-1107, Sept/Oct 1999. [17] M. Calais, L. J. Borle, V. G. Agelidis, “Analysis of Multicarrier PWM Methodss for a Single-Phase Five-Level Inverter,” Power Electroniccs Specialists Conference 2001. PESC 01. 2001 IEEE 32th Annnual Volume 3, 17-21 June 2001 pp: 1173 - 1178 Vol.3 C “A General Circuit Topology [18] N. S. Choi, J. G. Cho, G. H. Cho, of Multilevel Inverter,” Power Electronics Specialists Conference, 1991. PESC’ 91.. 1991 IEEE 22th Annual Volume, 24-27 June 1991 pp. 96 – 1033.

Nikhil Ku umar was born in Varanasi Town, Uttaar Pradesh State, India in 1990. He receiveed the B.E. degree in Electrical and Electtronics engineering from the Uttar Praadesh Technical University, Lucknow in 2012. Currently, he is pursuing M.Tech from Maulana Azad National Innstitute of Technology, Bhopal. His research interests include multilevel inverters, alternative energy sources, energy convversion, power quality, active harmonic analysis and Facts deevices analysis and control. V received BE degree in Deepak Verma Electrical Engineering from RGTU, Bhopal (20008) and the ME degree (2010) from MAN NIT, Bhopal, India. Currently he is pursuing Ph.D degree from MANIT Bhopal, India. I His research interest includes Solar Photovoltaic, MPTT, Grid interconnecction of renewable energy and residential photovoltaic energy storage system.

Suresh K. K Gawre has received his B.E. (2000) andd M. Tech. (2006) in Electrical Engineerinng and pursuing Ph.D. from MANIT (Formally MACT) Bhopal, India. He is currently working as Assistant Professor in the Department of Electrical Engineering MANIT, Bhopal. Apart froom power system his area of interest is power quality analysis, monitoring and solar power inttegration.

978-1-4799-4949-6 @ 2014 IEEE