Effectiveness of Increased and Efficient Sine wave in PWM Architecture

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 4 ISSUE 2 – APRIL 2015 - ISSN: 2349 - 9303

Effectiveness of Increased and Efficient Sine wave in PWM Architecture P.Thangam1

R.Rajesh Kanna2

Department of EEE, Hindusthan college of Engineering & Technology, thangamsusi@gmail.com

Assistant Professor, Department of EEE Hindusthan college of Engineering & Technology mrrajeshkanna@live.com

Abstract— The pure sine inverter, which is also referred to as a "true" wave, utilizes so as to produce your appliances with power. A wave, that is created by rotating AC machinery, is that the sort of wave that is usually provided by the utility company with the assistance of a generator. The benefits of using a pure sine wave inverter includes Square wave output is sometime harmful for the electrical devices. All equipment currently on the market is designed for use with function waves. Some appliances, notably microwaves and variable speed motors, won’t turn out full output if they are doing not use sine wave power. Some appliances, such as light dimmers and bread manufacturers, won’t work all while not wave power. A real wave supply is created most simply for prime power applications through rotating electrical machinery like armed services gas-turbine generators, house-hold diesel or gasolene backup generators, or the varied generators utilized by power firms that use a shaft source to make associate AC current.

Index terms: PWM, Pure Sine Wave Inverters, PSIM. ——————————  ——————————

I INTRODUCTION Inverters square measure circuits that convert dc to ac. We are able to simply say that inverters transfer power from a dc supply to an ac load. The objective is to create an ac voltage when only a dc voltage source is available. A variable output voltage can be obtained by varying the input dc voltage and maintaining the gain of the inverter constant. On the opposite hand, if the dc voltage is mounted & not manageable, a variable output voltage are often obtained by varied the gain of the inverter, that is often accomplished by pulse-width-modulation (PWM) control within the inverter. The inverter gain are often outlined because the magnitude relation of the ac output voltage to dc input voltage.

associate in input modulating signal, so as to generate the turn-on and turn-off signals for the switch mode inverter(shown in FIG:10). Gate drive circuits interface these switching signals to the semiconductor power switches in the inverter. The output voltage of the inverter is typically a quasi-rectangular ac. waveform with significant harmonic content.

Figure 1:Block diagram of typical DC-AC inverter II METHODS OF MAKING INVERTER There are different types of method Some of the techniques are shown below.

for

generating

PWM.

2.1Typical dc-ac conversion Most inverters do their job by converting the incoming DC into AC . We can a PWM signal by using A PWM generating chip (eg: SG3524,MC3PHAC) or op-amp. But in these conventional inverters the voltage gain is very low. In this model of op amp is used as a comparator which requires comparison of a triangular carrier, Vtriwith

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Figure 2: Circuit diagram of typical PWM inverter.

For applications requiring near-sinusoidal voltage with reduced harmonic distortion, a low-pass output filter is connected at the inverter output terminals before driving the load. FIG:11 shows the circuit for a MOSFET-based inverter in the full-bridge configuration. The unfiltered output voltage can be controlled by appropriate switching combinations of the MOSFET.

INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 4 ISSUE 2 – APRIL 2015 - ISSN: 2349 - 9303 wave. Those sampling value will go in PDC Register. And the PTMR register will generate the Triangular wave. Then the signal becomes Sinusoidal PWM signal with dead time. The microcontroller checks whether the generation is completed or not, if yes, take another sampling of the sine wave table, if not, it waits until completion This program is written in micro c.

2.2 Using a transformer By using a transformer an inverter can be made by using its polarity. It is also possible to step up the resulting AC. But it increases the weight and size of the inverter. It even have a negative impact on output due to the saturation of the core. A model of this method is shown below:

Figure 3: Inverter stepped up by transformer Two switches (q1, q2) are with the terminal of primary side of centre tap transformer. When q1 is on then polarity appears in the terminal of the transformer. When q2 is on, then reverse type of polarity appears in the terminal of the transformer.

For this type of sequential switching technique results a sinusoidal wave.

2.3 Using Microcontroller All the above mentioned methods are analog designs of inverter. We also like mention digital implementation of inverter using microcontroller. The proposed different approach is to replace the conventional method with the use of microcontroller. The use of microcontroller brings the flexibility to change the real-time control algorithms without further changes in hardware. It is also low price and has a little size of control circuit for the single phase full bridge inverter.

For generating SPWM we have chosen microcontroller PIC 16F877A. Basically we have studied about the detailed information about microcontroller and the mechanism of generating PWM. It can be done by using a micro c program.

Figure 4: Flow chart of SPWM Then using this code we need to burn the microcontroller with the help of INFRA PIC WRITER. An external oscillator is connected to the output port. Then oscillator shows the pulse width modulation output.

III PRINCIPLE OF OPERATION 2.4 Algorithm for generating SPWM Figure .4 shows the flow chart of single phase sinusoidal PWM signal. In this flow chart ―initialize variables‖ means initialize the user outlined memory cell, ―initialize port‖ initializes the ports in software by which the ports work as output ports. After that ―Initialize PCPWM‖ initializes the modules which are used to generate PWM. Then ―set all interrupts‖ initializes all interrupts which area associated with all kinds of desired interrupts. Then ―Initialize Sine Look up Table‖ stores the sampling value of sine

The proposed boost inverter achieves dc–ac conversion, by connecting the load differentially across two dc–dc converters and modulating the dc–dc converter output voltages sinusoidally. The blocks A and B represent dc–dc converters. These converters turnout of dcbiased sine wave output, in order to that every supply solely produces a unipolar voltage. The modulation of every converter is 180 out of phase with the other, that maximizes the voltage excursion across the load. The load is connected differentially across the converters.

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INTERNATIONAL JOURNAL FOR TRENDS IN ENGINEERING & TECHNOLOGY VOLUME 4 ISSUE 2 – APRIL 2015 - ISSN: 2349 - 9303 Thus, where as a dc bias appears at every finish of the load, with reference to ground, the differential dc voltage across the load is zero.

The generating bipolar voltage at output is solved by a push– pull arrangement. Thus, the dc–dc converters need to be current bidirectional.

FIG 5: The proposed dc–ac boost converter A circuit implementation of the boost dc–ac converter is shown in Fig.5.For a dc–dc boost converter, by exploitation the averaging concept the voltage relationship can be obtained for the continuous conduction mode by V1/Vin =1/1-D ; D= Duty Cycle. The voltage gain, for the boost inverter, can be derived as follows: assuming that the two converters are 180 out of phase, then the output voltage is given by Vo=V1-V2= Vin/(1-D)- Vin/D Vo/Vin=(2D-1)/D(1-D).The gain characteristic of the boost inverter Shon in figure 6.. It is interesting to note that the feature of zero output voltage is obtained for D=0.5.

Figure 7: Circuit diagram of SPWM inverter But the current still tends to keep flowing through the switch, that induces a high voltage across the switch. The faster the current decreases, the higher the induced voltage becomes. It may reach to sufficiently high level to destroy the switch. If the switch is unable to withstand the high induced voltage, it will be destroyed, and can no more block the current as an OFF-state switch. To avoid this, an auxiliary network is connected across the switch that prevents the induced voltage from going too high. The network is called a snubber.

By simulating this circuit we’ve got a sinusoidal ac output after appropriate switching combination. This circuit is simulated for 50 Hz and 4v peak amplitude.

V CONCLUSION

FIG 6: DC gain characteristics IV IMPLEMENTATION OF AN INVERTER CIRCUIT In this circuit we have used two DC-DC converters connected according t o f igur e 6 . To make the gate pulse we have used two op-amps. It works as a comparator with a triangular signal (carrier signal) and sine wave (reference signal) connected through a voltage follower to remove the effect of the impedance of supply signal.

We have used IGBT as switches. Circuits around the switches are placed to reduce the pressure on switches. This is called snubber circuit. once a switching device changes its state from ON-state to OFF-state, the ohmic resistance of the device shortly jumps to a very high level, blocking the current.

In looking at the components selected and the simulations created before the actual construction of the inverter, everything was built in mind for the aim of efficiency and keeping power losses to a minimum. This project is a stepping stone to a cheaper and efficient pure sine wave inverter, by using the information collected during this report as well as the schematics and recommendations the product produced here can be improved upon. A dc–ac voltage source converter has been proposed and studied both theoretically by experimentation. According to our opinion, the boost inverter is suitable for applications where the output ac voltage needs to be larger than the dc input and can offer economic and technical advantages over the conventional VSI. the transformer can be connected in order to increase the output voltage. The op-amps employed in that circuit will simply get replaced by microcontroller for obtaining the pulses. In that case there is no need of external components for base isolation because, every pin of microcontroller has separate ground.

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AUTHOR’S PROFILE

Thangam.P obtained her B.E. in Electronics and Communication Engineering,(Anna university, Chennai 2013), M.E. in Applied Electronics (Anna university of Chennai, 2015).She is currently doing her project work on Power Electronics and Drives

R.Rajesh kanna received the B.E., degree in Electrical and Electronics Engineering and the M.E., degree in Power Electronics and Drives. He has about 10 years of teaching experience. He is now Assistant professor in Electrical and Electronics Engineering, Hindusthan College of Engineering and Technology, Coimbatore. and He is pursuing in Ph.d in Anna university Chennai

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