A grid-tied inverter has to do something a standalone one never does: inject current into a stiff voltage source it does not control, at exactly the right frequency and phase, and disconnect itself if that source disappears. This project models the whole chain in Simulink — PV array, boost converter running maximum power point tracking, a three-phase inverter under dq current control, a phase-locked loop that tracks the grid angle, and an LCL filter — then studies what happens under an irradiance step, a grid voltage sag and an islanding event. It needs no hardware budget, which is the point: this is the project for a team with a laptop and no money.
Not just the parts. Teams budget from a component list, then run out in week six on wire, connectors and the driver board they destroyed. These are the lines that catch them.
| Line | Cost |
|---|---|
Components and materials From the bill of materials | Rs 0 |
Report, printing and binding Two or three bound copies, plots and the plagiarism check | Rs 400 to Rs 1,200 |
| Total | Rs 400 to Rs 1,200 |
| Each, split 3 ways | Rs 133 to Rs 400 |
Indicative bands last checked in August 2026 — a guide, not a quotation. Prices move and vary by seller, and anything you can borrow from the lab comes straight off the total. The 3.9 week figure assumes 9 person-weeks of work shared between 3; students past 4 add coordination rather than output, so the estimate stops improving there.
The same chain in words
The array model produces its current against voltage curve from irradiance and cell temperature, so the whole system can be driven with a realistic day profile rather than a constant source.
The boost stage runs the maximum power point tracker and pushes whatever power the array can make into the DC link. The DC link voltage would rise without limit if nothing removed that power.
The inverter's outer loop therefore regulates DC link voltage: if the link is rising, the array is making more power than is being exported, so the inverter is told to export more. That outer loop produces the d-axis current reference.
Measured grid currents are transformed into the dq frame using the angle from the PLL. In that frame a balanced sinusoidal current becomes two DC quantities, so ordinary PI controllers can drive the error to zero — which they cannot do on a sinusoid.
The q-axis reference sets reactive power. Setting it to zero exports at unity power factor; setting it non-zero is how a modern inverter supports grid voltage.
The LCL filter removes the switching harmonics before the current reaches the grid, and the islanding block lets the protection response be tested.
This is the chapter that separates an engineering project from an assembly job. Every value below carries the formula that produced it and the assumptions it rests on — check them against your own ratings before you use them, because your motor is not this motor.
Vdc must exceed the peak line-to-line grid voltage
1.414 x 415 = 587 V. If the DC link falls below that peak the inverter loses control of the current for part of the cycle and the waveform distorts badly. The margin also gives the current controller headroom to act.
D = 1 - Vin / Vout
1 - 400/700 = 0.4286. The string voltage moves with irradiance and temperature, so the duty cycle range must be checked at the extremes of the array's operating window, not just at the nominal point.
about a tenth of the switching frequency
Faster than that and the controller starts responding to the switching ripple it is supposed to ignore. The DC link voltage loop then sits about ten times slower again, at roughly 100 Hz.
place it between ten times the grid frequency and half the switching frequency
Below that band it interferes with the fundamental control; above it the filter no longer attenuates the switching harmonics. The resonance also needs damping, either a series resistor or an active damping term, or the filter rings.
fast enough to track the grid, slow enough to ignore its distortion
A fast PLL follows harmonics and unbalance into the angle estimate, which corrupts the dq transformation and therefore the current control. A slow one cannot follow a real phase jump. This trade-off is worth a figure in the report.
detect and disconnect within the limit the standard sets
An inverter that keeps energising a disconnected section of network is a danger to line workers and can damage equipment on reconnection. Simulating the islanding case and showing the trip is what makes this a power systems project rather than a converter one.
| Item | Qty | Unit cost |
|---|---|---|
MATLAB with Simulink and Simscape Electrical College or student licence Use the institutional licence. PSIM or PLECS are alternatives worth naming if none is available. | 1 | — |
Computer Any machine that runs the simulation in reasonable time Your own laptop or a lab machine — nothing to buy. | 1 | — |
Specifications are written as ratings rather than brands, so any equivalent part works. Where a line says to borrow from the lab, do — it is usually the largest number on the page, and the total drops to Rs 400 at the low end without them.
None of these blocks you — they are learnable inside a semester. Each one you do not have costs a couple of weeks, so count them into your plan.
Anything marked required is a blocker, not a difficulty. Arrange the access before you commit to the project, not after.
Use these when your guide says the scope is too small, or when you want something in the results chapter that nobody else in your batch will have.
The structure below is what a project report is marked against, with the mistake that costs marks in each chapter. There is no template to download and there will not be one: the writing is your work, and a site that did it for you would be helping you cheat rather than helping you pass.
A mini project report runs to about 40 to 50 pages, and the literature survey is usually brief. Guides expect one clear objective, met and measured. A final year report is normally 60 to 90 pages with a substantial literature survey, and many departments expect a paper submission alongside it.
The full report guide — front matter, conventions and page countsOne paragraph covering what the problem is, what you built, and what the result was. Written last, even though it appears first.
Loses marks: Describing the problem and the method but never stating a result. If there is no number in your abstract, it is not finished.
Why the problem matters, the context it sits in, and a clear statement of the objectives your project set out to meet.
Loses marks: Objectives written so vaguely that nobody can tell at the end whether they were met. Write objectives you can tick off in the conclusion.
What has already been done, what each approach achieved, and the specific gap your work addresses.
Loses marks: A list of paper summaries with no comparison and no gap. The survey exists to justify your design choice, so end it by saying what you chose and why.
The system as a whole: the block diagram, what each block does, and the signal or power path between them.
Loses marks: A block diagram copied from a datasheet or another report. Draw yours to match what you actually built, including the parts that are inconvenient.
Every component value and rating, with the formula, the assumptions and the arithmetic that produced it. This is the chapter that distinguishes an engineering project from an assembly job.
Loses marks: Component values with no justification. If a resistor is 10 kOhm, the report must say why it is not 1 kOhm.
The circuit as built, the PCB or wiring, the flowchart, and the parts of the code that carry the actual logic.
Loses marks: Twenty pages of pasted source listing. Include the flowchart and the few functions that matter, and put the full listing in an appendix.
What you measured, in tables and graphs, compared against what you predicted in the design chapter — including where they disagreed.
Loses marks: Photographs of the working model presented as results. A photograph is evidence that it exists, not evidence that it works. Results are measurements.
Whether each objective was met, what the measured performance was, and what the honest next step would be.
Loses marks: Future scope written as a wish list of unrelated features. It should follow from a limitation you actually hit.
Every source in a consistent style, plus datasheets, full code listings and the complete bill of materials.
Loses marks: Citing a blog or a video where a datasheet or a standard exists. Cite the primary source for anything you relied on.
The demonstration is half the assessment. These are the questions this project invites, and the answers are written the way you would give them out loud.
Because in the abc frame the quantities to be controlled are sinusoids, and a PI controller cannot drive a sinusoidal error to zero — it always leaves magnitude and phase error. Transforming to a frame rotating with the grid turns a balanced set of sinusoids into DC quantities, and a PI controller does drive a DC error to zero. That is the whole reason for the transformation.
It estimates the grid voltage angle continuously, so the controller knows where the grid is in its cycle at every instant. That angle is what the abc-to-dq transformation needs. Without it the rotating frame is not aligned with the grid, the d and q axes no longer correspond to real and reactive power, and the whole control scheme falls apart.
Because the DC link voltage is the visible sign of a power imbalance. If the array is producing more than the inverter exports, the surplus charges the capacitor and the voltage rises. Regulating that voltage therefore automatically exports exactly what the array produces, without needing to measure array power at all, and it protects the capacitor from overvoltage.
An LCL filter attenuates the switching harmonics far more steeply — sixty decibels per decade against twenty — so the same harmonic performance is achieved with much less total inductance, which means less cost, less size and less voltage drop at the fundamental. The price is a resonance that must be damped and a more complex control design.
Islanding is when a section of the network is disconnected from the utility but the inverter keeps energising it. It is dangerous because line workers expect a disconnected line to be dead, and because when the utility recloses onto the island the two sources are out of phase, which can destroy equipment. Standards therefore require the inverter to detect the condition and disconnect within a specified time.
The reactive power the inverter is asked to exchange with the grid. Zero q-axis current means unity power factor, exporting real power only. A positive or negative value injects or absorbs reactive power, which is how modern inverters support or reduce the voltage at their connection point during a disturbance.
Normally taken as a B.E. mini project (5th/6th sem) or B.E. final year project (7th/8th sem) project. If yours is a different course, the extensions above scope it up and the simpler half of the design scopes it down — the arithmetic does not change. Back to all projects.