Design of Transformer Less Inverter for Domestic Universal Power Supply System
Project summary Due to increasing economy, Pakistan is facing the challenges of energy crisis. Pakistan is reeling under heavy load-shedding resulting in leaving citizens without electrici
2025-06-28 16:26:36 - Adil Khan
Design of Transformer Less Inverter for Domestic Universal Power Supply System
Project Area of Specialization Electrical/Electronic EngineeringProject SummaryProject summary
Due to increasing economy, Pakistan is facing the challenges of energy crisis. Pakistan is reeling under heavy load-shedding resulting in leaving citizens without electricity for long hours which deliberately involves the need to search for alternate resources. Installing UPS units and generators offset the very idea of load-shedding.
Transformerless UPS systems were first developed in the 1990s and offered a number of benefits over traditional transformer-based systems in terms of higher efficiency, reduced size and weight, and cost savings. Presently, transformerless UPS are constructed of modular building blocks that deliver high power in a lightweight, compact packaging. It has high efficiency up to 90-96 percent. The whole concept of transformerless inverter involves Rectification, voltage division, regulation, and filtering. Transformerless UPS operate in the same way, apart from one key difference. It uses metal-oxide semiconductors field effect transistors (MOSFETs) that are capable of dealing with high voltages, eliminating the need for a step-up transformer after the inverter. An input rectifier is used to convert AC to DC to maintain the DC Source i.e battery and power the DC to AC inverter. In turn, the inverter provides AC to the load. AC output voltage is then filtered to achieve a pure sine wave which is then delivered to the appliances.
The proposed system suggests that a 220V AC voltage from the feeder is fed to the appliances during the availability of electricity. But when the power outage occurs, the battery becomes the main source of power supply. Rectifier converts the input power from AC to DC. Its second main role is to recharge the batteries, while the DC power routes to the inverter too. The charge controller continuously maintains the correct charge level on the battery and ensures a seamless power transition to battery power when needed for a complete UPS power supply solution. A boost converter (step-up converter) is a DC-DC power converter that steps up voltage (while stepping down current) from its input (supply) to its output (load). This unique capability is achieved by storing energy in an inductor and releasing it to the load at a higher voltage. The inverter in which the voltage and current are forced to pass through zero crossing by using an LC-resonant circuit, is called a resonant pulse inverter. Then filtering smoothens out events such as surges and electrical noise, ensuring the final output is a pure sine waveform. A static bypass switch automatically transfers the load to the mains electricity supply when there is an internal fault or failure within the system.
Project ObjectivesProject objectives:
The project’s main objectives are
- To design of charge controller for battery:
This prevent battery from overcharging and draining completely to the point of no return and helps to keep battery more lasting
- To design of DC-DC boost converter for high voltage:
A boost converter is a DC-DC power converter that steps up voltage from its input to its output. It is a class of switched-mode power supply containing at least two semiconductors and at least one energy storage element: a capacitor, inductor, or the two in combination. This resonant pulse inverter works on 300-400 VDC, which needs DC-DC boost. It is supplied with 12VDC which is then converted to 300-400VDC as required by the Resonant inverter in next stage.
- To design of series resonant pulse inverter:
A resonant inverter is used to change direct current (DC) to alternating current (AC) through high frequency switching topology. A resonant pulse inverter is a voltage and current inverter that uses an LC-resonant circuit to drive the voltage and current to pass through zero crossing. Electrical inverters based on resonant current oscillation are known as resonant inverters. The resonating components and switching device are connected in series with the load to generate an underdamped circuit in series resonant inverters. Due to the circuit's intrinsic properties, the current via the switching devices drops to zero. The switching element is considered to be self-commutated if it is a thyristor. At a high output frequency, ranging from 20 kHz to 100 MHz, this type of inverter produces an almost sinusoidal waveform. The resonating components are minimal due to the high switching frequency.
- To design of filter to reduce THD:
A filter is a circuit capable of passing (or amplifying) certain frequencies while attenuating other frequencies. RLC circuits are used as low pass filter, high pass filter, band-pass filter and band-stop filter. RLC circuits have a resonance and are good for filtering out one frequency or making a very stable oscillator.
Project implementation method
The methodology flow for this project begins with a thorough literature review which helped in selecting an appropriate title and gather information. After proposing title, dividing it into objectives and creating a proper timeline for timely completion of project is important .Objectives helps in further circuit design and components selection. After basic circuit design and component selection we performed simulations on software (such as Proteus and Live wire). Simulation software is used widely to design equipment so that the final product will be as close to design specs as possible without expensive in process modification. Simulating on software also reduces error chance and component loss. Simulations of individual objectives and then combined were done to avoid any harm in real time implementation. Sometimes real time implementations does not provide accurate results so real time debugging and troubleshooting is necessary. After results are achieved final product is presented in form which can be easily carried in domestic use.
Implementation method for transformer less inverter is similar to that of transformer based inverter except two blocks. First Boost converter is used for stepping up 12V to high voltages which was done by transformer in transformer based and second is use of Resonant inverter for achieving resonance and power efficiency. At the end 50 Hz filter will provide pure sine wave and can be dispatched towards load.
The project aims to develop an easy to maintain inverter which is better than a traditional inverter in terms of power loss and efficiency.
It will also be budget friendly while being safer for environment than a traditional inverter.
It will also be rather compact and small package compared to a conventional UPS.
It will reduce core and winding losses which occurred in transformer based inverters.
Transformer based UPS are bulky due to heavy weight transformer while transformer less reduces this drawback.
It has less capital and maintenance cost.
New trend can be developed towards industrialization if local manufacturing takes place.
UN’s Sustainable Development Goals of the Project.
Technical details
For 220V duty cycle is adjusted at 95 % but for domestic usage load is variable. Our project provides flexibility on this point as output feedback is provided to boost and voltage is stepped up according to variation in load.
We used MOSFETS with high switching frequency for high voltages. It greatly reduces both size and price of components.
We took self-designed capacitors and Inductors values as they play major role in our project. Inductors serve as a magnetic field storage element while capacitors minimizes voltage overshoot and ripple present in output voltage so they must be designed in consideration with input /output voltage and current.
Mathematical Model:
Duty cycle:
D=1-(Vin / Vout) 
Input Current:
Iin=(V out * Iload) / V in
Inductance:
?Io=10% of Io 
L=(Vs * D)/(fo * ?Io)
Capacitance:
?V=2% of Vo 
C=(Io * D) / (fs * ?Vo) 
| Item Name | Type | No. of Units | Per Unit Cost (in Rs) | Total (in Rs) |
|---|---|---|---|---|
| Total in (Rs) | 80000 | |||
| Voltage regulators | Equipment | 20 | 200 | 4000 |
| Inductors | Equipment | 25 | 200 | 5000 |
| Capacitors | Equipment | 25 | 200 | 5000 |
| Diodes | Equipment | 40 | 350 | 14000 |
| Resistors | Equipment | 100 | 200 | 20000 |
| ICs | Equipment | 12 | 500 | 6000 |
| PWM | Equipment | 5 | 500 | 2500 |
| Mosfets | Equipment | 12 | 300 | 3600 |
| IGBTs | Equipment | 12 | 500 | 6000 |
| Arduino | Equipment | 1 | 1200 | 1200 |
| PCB | Equipment | 2 | 1350 | 2700 |
| printing | Miscellaneous | 2 | 2000 | 4000 |
| miscellaneous | Miscellaneous | 1 | 6000 | 6000 |