proteus based simulation of pv inverter for rural electrical service

International Journal of Modern Engineering Research (IJMER)

www.ijmer.com Vol.3, Issue.2, March-April. 2013 pp-1212-1219 ISSN: 2249-6645

www.ijmer.com 1212 | Page

Mohammed Shoaib, 1 Prof V. Nagaraj

2

1Department Of Electrical &Electronics engineering,

2Assoc.Prof. (Senior Scale), Manipal Institute of Technology, Manipal University, Manipal, India

Abstract: In many remote or underdeveloped areas, direct access to an electric grid is impossible and a photovoltaic

inverter system would make life much simpler and more convenient. With this in mind, this paper aims to design, and

simulate PV inverter in proteus professional software. This inverter system could be used as backup power during outages,

battery charging, or for typical household applications for rural especially. The principle is to adapt the output voltage of

the solar module to the battery by using the technique of pulse width modulation (PWM). The sinusoidal pulse width

modulated (PWM) waveform is generated from inverter in laboratory by 16 bit microprocessor through program developed

using a novel technique of direct modulation strategy .The key features of the system are a true 50Hz, 230Vsinusoidal

voltage output, a wide input range, and a power output of up to 350 watts. The overall goal is to design this system while

minimizing component costs.. In addition, inverters in the lower price range typically lack most of the features. solar home

lighting systems mostly comprises of solar panel, solar charger, battery & a inverter, The main motivation of this paper or

the uniqueness of this project is to combine both the solar charger as well as inverter together to ATMEGA 32 RISC based

which works up to 16MIBS which reduces the cost as well as the system becomes compact.

Keywords: Pv, Pwm, Mcu, Proteus, Dpwm, Pwm Charger.

I. Introduction India s off-grid solar (PV) market has three major segments: captive power plants (where the majority of generation

is consumed at the source), telecom towers, and rural electrification. The market potential for these PV segments has created

an off grid solar market in India. India like other developing countries has made tremendous progress in producing energy in

agriculture sectors. However, it lags behind in meeting the entire energy demand in remote rural and its nearby suburban or

urban areas. As a result, our country is facing acute shortage of power especially in those village areas where utility grids are

either not available or its further extension is not possible due to costly affair. Even in the sub-urban or urban area of these

villages where utility grids are available, only 20% electricity is available for end users and so they lack such basics of

human need as lighting, irrigation, communication, primary health care facility, safe drinking water, education etc.

Renewable energy is the only feasible option to electrify these villages and its surrounding areas.

Along with increases of demand for the new energy, and the key technologies of use new energy sources is how to

integrate new energy into electrical energy. In this paper high computing speed, low-power single chip MCU ATMEGA 32

is used as the control chip, improve the inverter efficiency. This article also describes the structure of the inverter, control

methods, focuses on software design and finally summarized.

The primary function of a charge controller in a stand-alone PV system is to maintain the battery at highest possible

state of charge while protecting it from overcharge by the array and from over discharge by the loads [1]. Although some PV

systems can be effectively designed without the use of charge control, any system that has unpredictable loads, user

intervention, optimized or undersized battery storage (to minimize initial cost) typically requires a battery charge controller.

The algorithm or control strategy of a battery charge controller determines the effectiveness of battery charging and PV array

utilization, and ultimately the ability of the system to meet the load demands. Additional features such as temperature

compensation, alarms, meters, remote voltage sense loads and special algorithms can enhance the ability of a charge

controller to maintain the health and extend the lifetime of a battery, as well as providing an indication of operational status

to the system caretaker.

Important functions of battery charge controllers and system controls are to [2]:

Prevent Battery Overcharge: to limit the energy supplied to the battery by the PV array when the battery becomes fully

charged.

Prevent Battery Over discharge: to disconnect the battery from electrical loads when the battery reaches low state of

charge.

Provide Load Control Functions: to automatically connect and disconnect an electrical load at a specified time, for

example operating a lighting load from sunset to sunrise.

A series charge controller or series regulator disables further current flow into batteries when they are full. A shunt

charge controller or shunt regulator diverts excess electricity to an auxiliary or "shunt" load, such as an electric water

heater, when batteries are full.

Proteus Based Simulation of PV Inverter for Rural Electrical

Service




Simple charge controllers stop charging a battery when they exceed a set high voltage level, and re-enable charging

when battery voltage drops back below that level. Pulse width modulation (PWM) [2] and maximum power point tracker

(MPPT) technologies are more electronically sophisticated, adjusting charging rates depending on the battery's level, to

allow charging closer to its maximum capacity. Charge controllers may also monitor battery temperature to prevent

overheating. Some charge controller systems also display data; transmit data to remote displays, and data logging to track

electric flow over time [4].

II. System Block Diagram 2.1Inverter Drive circuit and Filter circuit design.

Figure: 1

ATMega32 microcontroller: It acts as the heart of the system. It controls and monitors entire system. The main

function of this microcontroller is to generate SPWM signals. These signals are given to Half-bridge switches to convert dc

voltage to ac voltage. Microcontroller also takes care of the protection. It protects the load from over voltage, under

voltage.This system includes a feedback network where at the output AC is converted to DC using bridge rectifier and is

properly isolated using an npn based opto coupler and a voltage divider circuit which is fed back to adc module of MCU and

output voltage is regulated by controlling the duty cycle of the DPWM.

In the present work sinusoidal pulse width modulation (SPWM) technique is used to control the switches of the

Halfe-bridge. This technique is widely used in inverter to digitize the power so that a sequence of voltage pulses can be

generated by the on and off of the power switches. The pulse width modulation inverter has been the main choice in power

electronics, because of its circuit simplicity and rugged control scheme.

After analysis and comparison, the part of the contra variance use half-bridge inverter circuit, Inverter Bridge is

composed of FET IRF3205, using 2n3906 and 2 Bc547 as a driver circuit. Single-chip generated PWM signal, go though

2n3906 to control the inverter switching devices IRF3205 the shutdown of conduction, then inverter can produce sine wave

outputs. But the sine wave contains many high-order harmonic generation, required the LC filter circuit to be smooth, non-

standard high-order harmonic generation of sine wave. The size of capacitance and inductance values required theoretical

calculations and the actual debugging to determine. In this design, we take C = 100uF, L = 40uH.

2.2 Pwm Control

A software program has been developed to generate sinusoidal pulses for N numbers in a half cycle using direct

modulation strategy (DPWM) whose widths are proportional to amplitude of sine wave at sampled points (Fig.2).

Mathematically the pulse width and corresponding notch width are expressed by (1) and (2) respectively as:

Pulse width (Pi)

= K Pwm x 2 Sin (2i - 1) π / (2*N) . (1)

Where,

i = 1, 2, 3,…..N

K = Voltage Factor (0 –1)

P wm = ( D – G ) * 2

D = 180 / (2*N)

G = Minimum Gap between pulses (say 1degree) at K=1

N = Number of PWM pulses in Half sine wave (180 degree i.e. = 10 ms)

Notch width (Ti) = 2D - [1/2(Pi – 1 + Pi)]. (2)




Figure 2: Programmable DPWM sinusoidal

Modulated (N = 3 ) half sine wave of 50 Hz . Y

axis = Amplitude (5V), X axis = Total time (T) in

half cycle i.e 180 degree =10ms.

III. System Software Design 3.1proteus Introduction

Proteus supports multiple mainstream microcontroller system simulation, such as 51 series, AVR series, PIC12

PIC16 series, PIC18 series, Z80 series, HC11 series, series, 68,000 series, etc. And provide software debugging function and

its periphery connection device of RAM, ROM, keyboard, motor, LED, LCD, AD/DA, partial SPI device.

With the development of science and technology, the computer simulation technology has become an important

sector of many design method of early. It is designed to be flexible, results, the process of unity. It can make the design time

is shortened, cost reduction, also can reduce the risk of engineering. Believe in microcontroller application of PROTEUS can

also have extensive application.

3.2Target specifications

3.2.1 Inverter specifications.

Frequency 50 Hz +/- 2Hz

Efficiency >80 %

Output 350 watts, 12VDC ~ 220 V +/- 5

Harmonics <5 %

spwm Sine wave inverter

Mobility Portable, microcontroller based

Protection circuits yes

Table1

3.2.2 Solar charge controller specification:

Prevents battery from being overcharged and damaged by the solar panel

Compatible with 12 volt battery bank

Overload, short circuit, and reverse polarity protected.

LED's indicate charging status.

3.3 Simulation Results

3.3.1 pv inverter simulation

Figure 3: (Schematic of Proposed PV Inverter with battery charger.)




Fig4. (Schematic of inverter)

Fig5. (Pulse train drawing the mosfet T=20 ms, TON=10ms &TOFF=10ms)

Fig6. (Output voltage waveform as per simulated resultsVO=228 Volts ).

Fig7. (Current wave form as per simulated results IO=1.7 Amps).

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3.4 simulation of PWM charge controller

Figure 8(schematic of pwm based charge controller)

Solar Charge controller is a device, which controls the battery charging from solar cell and also controls the battery

drain by load. The simple Solar Charge controller checks the battery whether it requires charging and if yes it checks the

availability of solar power and starts charging the battery. Whenever controller found that the battery has reached the full

charging voltage lavels, it then stops the charging from solar cell. On the other hand, when it found no solar power available

then it assumes that it is night time and switch on the load. It keeps on the load until the battery reached to its minimum

voltage levels to prevent the battery dip-discharge. Simultaneously Charge controller also gives the indications like battery

dip-discharge, load on, charging on etc

OPERATION OF SYSTEM: Pulse Width Modulation (PWM) is the most effective means to achieve constant voltage

battery charging by switching the solar system controller‟s power devices. When in PWM regulation, the current from the

solar array tapers according to the battery‟s condition and recharging needs. In the fig 8 solar charge is controlled by

controlling the duty cycle ,such that an optimum 13.75 volts is fed to battery for charging purpose.2N3055 NPN power

transistor , Packaged in a TO-3 case style, it is a 15 amp, 60 volt is used as switching device Initially 50 %duty cycle is fed in

MCU using PORT C0. As the solar voltage is unregulated the voltage is controlled by adjusting the duty cycle .Two

reference voltage is fed in MCU, whenever solar voltage is < reference voltage V1 (>> Pwm), similarly vice versa.

3.4 Simulation Results for PV Charger

The proposed charge controller is simulated by using Proreus ISIS 7 Professional for five cases listed in table 1 and

the simulation results shown in figures 8-12.

Test no Solar

voltage

Battery

voltage

Duty

cycle%

1 18 11.0 96%

2 16 11.0 99%

3 10 12.0 35%

4 17 13.5 0%

Table 2

3.4.1Algorithm for Charge Controller

As microcontroller software works as sequential basis, it will perform these steps Sequentially.

1. Power On, RESET

2. Define Input / Output of the ports

3. Setup ADC for measurement

4. Start ADC Module

5. Measure ADC2, ADC3, ADC4, ADC5. ADC2 for „Solar Voltage‟, ADC3 for „Battery High Set‟, ADC4 for „Battery Low

Set‟ and ADC5 for „Battery Voltage‟

6. If „Battery Voltage‟ < „Battery High Set‟ and „Solar Voltage‟ > „Battery Voltage‟ then

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PD1/TXD15

PD2/INT016

PD3/INT117

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PD5/OC1A19

PD6/ICP120

PD7/OC221

PC0/SCL22

PC1/SDA23

PC2/TCK24

PC3/TMS25

PC4/TDO26

PC5/TDI27

PC6/TOSC128

PC7/TOSC229

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PA6/ADC634

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a. Switch ON Battery Charging

b. Switch ON Charging LED

c. Switch OFF Battery High LED

7. If „Battery Voltage‟ > or = „Battery High Set‟ then

a. Switch OFF Battery Charging

b. Switch OFF Charging LED

c. Switch ON Battery High LED

8. If „Solar Voltage‟ < „Battery Voltage‟ then

a. Switch OFF Battery Charging

b. Switch OFF Charging LED

c. Switch ON Load

9. If „Battery Voltage‟ < or = „Battery Low Set‟ then

a. Switch OFF Load

b. Switch ON Battery Low LED

10. If „Battery Voltage‟ > „Battery Low Set‟ then

a. Switch OFF battery Low LED

11. Go to Step 5.

Figure: 9. (the above schematic refers to step no 6 of the algorithm).

Figure: 10. Simulation Result for Test number 1(channel c represents the output of the MCU PWM signal)

Figure: 11. Simulation Result for Test number 2(channel c represents the output of the MCU PWM signal).




Figure: 12. Simulation Result for Test number 3(channel crepresents the output of the MCU PWM signal)

Figure: 13. Simulation Result for Test number 4(channel crepresents the output of the MCU PWM signal)

Figure13. (The above schematic refers to step no9 of the algorithm)

Figure14. (The above graph shows switching on; of the relay once battery reaches its low set point).




IV. Conclusion The article is being simulated in the Proteus software, the hardware must be tested accordingly, Proteus not only

make many MCU visualize, but also can visualize many MCU examples. Which is 80–90 % similar to real operating device?

The above system does not require carrier signal or a comparator circuit as usually require in conventional triangular PWM

generator circuit and thus reduces the cost as well as complexity in producing PWM base drive signals.

V. Acknowledgment The authors pay their sincere gratitude to the Mr I.B rao the MD of power one Microsystems & the Management of Power

one Microsystems ,Bangalore for funding this technical work.. The author also extends their heartily thanks to R&D

Engineer Mr M. M. Venkateswaran & Mr Valache Siddalingappa, for their valuable time and effort for scrutinizing the

design of the project.

References [1] G.J. Vander et al, “150W Inverter – an optimal design for use in solar home system”, International Symposium on Industrial

Electronics, Proceedings ofISIE, 1998, Vol. 1, pp 57-62.

[2] B. Lindgrin, “A 110 W inverter for photovoltaic application”, Published in International Journal of Renewable Energy Engineering,

April 2002.

[3] S. Martínez, M. Castro, R. Antoranz, and F. Aldana, “Off-line uninterruptible power supply with zero transfer time using integrated

magnetics,” IEEE Trans. Ind. Electron, vol. 36, no. 3, pp. 441–445, Aug. 1989.

[4] M. T. Tsai and C. H. Liu, “Design and implementation of a cost-effective quasi line-interactive UPS with novel topology,” IEEE

Trans. Power Electron., vol. 18, no. 4, pp. 1002–1011, Jul 2003

[5] Adel Nasiri, Zhong Nie, Stoyan B. Bekiarov, and Ali Emadi, “ An On-Line UPS System With Power Factor Correction and Electric

Isolation Using BIFRED Converter” IEEE transaction on Industrial Electronics, vol, 55.no.2,pp. 722 - 730 ,February 2008.

[6] Ross, J., Markvart, T., and He, W.: „Modelling Battery charger Regulation for a Stand-alone Photovoltaic System‟ , Sol. Energy,

2000, 69, (3), pp. 181–190

ABOUT THE AUTHORS

MD SHOAIB has obtained his B.Tech degree in EEE from New Horizon College of engineering and currently

pursuing his MTECH in power electronics system and control in Manipal University .His area of interest is power

converters and embedded systems.

V.NAGARAJ has has obtained his ME in power systems from Mysore university, and He has 34years of teaching

experience. He has published 2 research papers at national level. His area of teaching is Applications of soft

computing systems to power Systems

proteus based simulation of pv inverter for rural electrical service

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