Description
Abstract
This project is based on cascaded inverter and quasi z source techniques. This five-level inverter is cascaded of the two inverter circuits and also included a quasi z source circuit in front of the inverter circuit. A quasi z source circuit is used to boost the dc voltage and the dc voltage is applied to the inverter. So inverter output voltage range is increased.
Introduction
The multilevel inverter provides a suitable solution for medium and high power systems to synthesize an output voltage which allows a reduction of harmonic content in voltage and current waveforms. The solar photovoltaic (PV) modules directly convert the light energy into electrical energy, but energy obtained from the PV module acts as a low voltage DC source and has relatively low conversion efficiency. In order to improve the efficiency and convert low voltage DC source into usable AC source, the power electronics converters are used to transform DC into AC.
Proposed System
This project is proposed to single-phase quasi z source cascaded multilevel inverter. This quasi circuit act like a boost converter circuit. The power transformer ac supply is applied to the bridge rectifier and the dc voltage is applied to the quasi z source network. Quasi z source network has two inductors for boosting the dc voltage. And also have a diode, that diode is used to avoid the voltage reversal. The boosted dc voltage is applied to the inverter circuit. The inverter circuit output is cascaded to generate the five-level AC output. The five-level output voltage waveform is shown below.
Block Diagram
Block Diagram Explanation
- Pulse generator: ? Here we have used a PIC microcontroller (PIC 16F877A) to make a switching signal.
- Driver circuit: -It can be used to amplify the pulses and provide isolations using an optocoupler. It has two functions,
- Amplification
- Isolation
- Bridge Rectifier: It converts AC to DC Supply.
- Quasi z Source: This circuit is used to boost the input dc voltage.
- Inverter: It converts DC to AC Supply.
Driver Board
Pic Controller Board
Working
The pic controller is used to generate the PWM pulses for the converter and inverter circuit. The pic controller pulses are given to the driver circuit as input. Driver board is mainly used to isolate and amplify the input signals from the controller. The amplified driver output will be connected to the main power circuit devices. And the devices are turned on by using the PWM pulses. The power transformer is directly connected to the bridge rectifier. The bridge rectifier converts the ac voltage into a dc voltage. Dc voltage is converted into ac voltage by using a multilevel inverter circuit. The multilevel inverter output waveform is shown below.
Circuit Diagram For Dc To Ac Multilevel Inverter (5 levels)
Advantages
- Reduce the switching loss.
- High efficiency.
- Reduced THD.
Applications
- Industrial machines
- Automobiles medical equipment
- Airplanes
- High Power Applications
Conclusion
In this project it reduces the uneven degradation of power switches, switching losses when compared to the conventional PWM technique and harmonics are reduced and the output waveform level is increased. And also increase the efficiency.
Multilevel inverter
Multilevel Inverter Output
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