PHOTOVOLTAIC (PV) power supplied to the utility grid is gaining more and more visibility, while the world’s power demand is increasing. Solid state inverters have been shown to be the enabling technology for putting Photovoltaic PV system into the grid. 2-level inverters are used to convert the DC voltage obtained from the Photovoltaic system to AC voltage fed to the utility
Increasing attention has been paid to multilevel dc/ac inverters in recent years to obtain output voltage of high quality. One of the more flexible topology is the cascaded multilevel inverter, which will be employed in the project to improve the quality of the output voltage by reducing the harmonic contents. The project consists of two modules: power circuit and control circuit. The power circuit consists of two H_bridges, five level cascaded multilevel inverter. For each inverter stage the 48V DC supply was given from the solar panel. The multilevel inverter used to convert input DC voltage into AC voltage. The control circuit include the using of PIC microcontroller and drive unit used to produce 12 V pulses required for driving the H-Bridges to generate the five level output voltage.
Experimental and simulation results using matlab /simulink will be presented to show the improving of the power quality using the multilevel inverter.
The main reason to choose this project that we believe that the world developed more and more and we should at least know what happened in photovoltaic model (PV).
Power generated by PV modules and injected into the grid is gaining more and more visibility in the area of PV applications. And the PV modules was in the past the major contributor to the cost of the systems. So the cost of the inverters is for the same reason becoming more visibly in the total.
There for The energy demand in the world is steadily increasing and new types of energy sources must be found in order to cover the future demands, since the conventional sources are about to be emptied. One type of renewable energy source is the photovoltaic (PV) cell, which converts sunlight to electrical current, without any form for mechanical or thermal interlink. The topologies of multilevel inverters are classified in to three types the Flying capacitor inverter, the Diode clamped inverter and the Cascaded bridge inverter. Two primary types of PV technologies available commercially are crystalline silicon and thin film.
After that we can brief why we select PV system?
People select PV systems for a variety of reasons. Some common reasons for selecting a PV system include:
• Cost: When the cost is high for extending the utility power line or using another electricity-generating system in a remote location, a PV system is often the most cost-effective source of electricity.
• Reliability: PV modules have no moving parts and require little maintenance
Compared to other electricity-generating systems.
• Modularity- PV: systems can be expanded to meet increased power requirements by adding more modules to an existing system.
• Environment-PV : systems generate electricity without polluting the environment
And without creating noise.
In our project we using many IC to built it and to have at the end multilevel inverter .Multilevel converter consists of an array of semiconductors switches and capacitors voltage sources(IGBT). Through specific commutations of the semiconductors switches, it is possible to synthesize high quality AC waveforms from several DC sources.
There are three type of multilevel Converter topologies
The main three topologies that have been proposed for the multilevel converter are:-
1- Diode clamped (Neutral clamped)
2- Capacitor clamped (flying capacitor)
3- Cascade multilevel converter with separate DC sources.
And we select cascade multilevel converter with separate DC sources for the following reason.
Each inverter level can generate five different voltage outputs, +2Vdc, +Vdc,0, –Vdc and -2Vdc.