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Copy of Grid Tie Inverter

First Presentation of the Final Year Project
by

umer sohail

on 16 April 2013

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Transcript of Copy of Grid Tie Inverter

Design and Fabrication of Single-Phase Grid Tie Inverter
Group Members:
Zenab Ali - EE656
Mr. Ikram Qureshi
Mr. Sohail Zaki Scope of the Project
To design and fabricate a single phase Grid Tie Inverter (GTI) which harvests energy from renewable sources and feeds it into the National Power Grid (e.g. WAPDA, KESC etc.)

Proposed capacity of 250 Watts
Vision We imagine a world in which every single household is a powerhouse of clean, sustainable energy and the sum of all this energy is enough to ensure a habitable planet for our future generations
A grid tie inverter enables its users to sell the excessive electricity generated from renewable power systems.

Such incentives, if given by utility companies in Pakistan can help solve the energy crisis.

Competitive Analysis Basic Operation
GTI takes DC power and inverts it to AC.

The grid tie inverter must synchronize its frequency with that of the grid (e.g. 50 or 60 Hz) .

A high-quality GTI should have a close to unity power factor.

The output voltage from the GTI should be slightly higher than the grid voltage in order to enable the transmission of power from GTI to the grid.

Basic Single Phase GTI Circuit
Important Stages of a GTI Grid Sensing A stepped-down voltage from the grid will be sampled and used to generate the SPWM signal.

Thus the frequency of the output voltage from the GTI will have the same frequency as the grid.

Another possibility is to generate the sine wave from an analog oscillator or from a micro-controller.
Switching/SPWM The control strategy is used to switch the IGBTs/MOSFETs present in the H-Bridge, to convert the DC input to AC.

The output from the H-Bridge is not a perfect sine wave, therefore, it is passed on to the Filtering stage.
Filtering Filtering is done to get a perfect sine wave that can be fed to the load as well as into the Grid.

For this purpose we use a Low Pass LC filter at the output side of the Power Circuit.

This filter reduces the Harmonic Content in the Signal and also provides a smoother form of a signal.
Anti-Islanding Protection To make our device compliant with the safety requirements of utility companies we plan on adding a mechanism that disconnects the inverter from the grid if the grid shuts down.

These protections eliminate the chance that a distributed generation system will inject power into the disconnected utility wires or switchgear and cause a hazard to utility personnel.

Proposed Methods for Anti-Islanding Protection Manual Disconnection

Automated Disconnection
Manual disconnection could be automated through the use of signals sent through the grid, periodically checking for signals from the utility and disconnecting either on command, or if the signal disappears for a fixed time. This system is relatively expensive.

Use of SCADA (Supervisory Control And Data Acquisition)
An alarm could sound or a switch can be operated if the SCADA system detects voltage on a long where a failure is known to be in progress.

Current Transformer controlled Protective Relay
THD is caused by delay times and Voltage drops across switches, this can be reduced by using optimum switching algorithms.

Low Pass LC filters can be used to eliminate higher order harmonics. An extensive market research can help in finding the right components in time.
Safety Features It should be less than 5%. Proposed Scheme for SPWM The sine wave is sampled from the grid, this sampled sine wave is rectified by a precision rectifier. The precision rectifier will rectify the sine wave from the grid to DC. Switching Procedure
Besides having the SPWM signal for the switching of the IGBTs/MOSFETS, the proposed GTI will also have square wave signal for the switching.

A micro-controller is employed which will ensure that the square wave signal that is generated by the analog circuit is in phase with the sampled sine wave and the triangle wave used for SPWM generation is in the correct sequence. The total harmonic distortion(THD), of a signal is a measurement of the harmonic distortion present and is defined as the ratio of the sum of the powers of all harmonic components to the power of the fundamental frequency.

Un-availability of the required components in the local Market.
Expected Problems Proposed Specifications Gantt Chart in the long run Thank You Scheme of Presentation Scope of Project
Vision
Competitive Analysis
Proposed Specifications
Basic Working
Important Stages of a Grid Tie Inverter (GTI)
Safety Features
Problems and Solutions