Frequency Controlled Refrigeration

Traditional refrigeration devices control the temperature by operating the compressor in binary mode (i.e.) ON or OFF. Once the required temperature is achieved, the compressor trips down. This method deemed to be inefficient as it involves substantial deviation from the desired temperature. Moreove

Project Title

Frequency Controlled Refrigeration

Project Area of Specialization

Electrical/Electronic Engineering

Project Summary

Traditional refrigeration devices control the temperature by operating the compressor in binary mode (i.e.) ON or OFF. Once the required temperature is achieved, the compressor trips down. This method deemed to be inefficient as it involves substantial deviation from the desired temperature. Moreover, the initial electric jerk (while turning the compressor ON) causes a voltage dip which affects nearly all home appliances.

This FYP addresses the above-mentioned problems by operating the traditional compressor at multiple frequencies (instead of 2 digital level (i.e.) 0 or 50 Hz) using single phase variable frequency drive (VFD). The compressor will run at a different speed (frequency) for the different temperature to provide efficient temperature control and power saving. As this approach ensures the continuous operation of the compressor, thus it will yield the eradication of the ON/Off jerks as well. The aforementioned idea will result in the smart use of electrical power.

Project Objectives

The basics objectives and aim of our project is to make prototype of all this working principles which are necessary in this power saving phenomenon. It contains hardware and software implementation, through which we not only have to run the refrigeration device through VFD phenomenon also have to elaborate how this idea is using in it to make the device working efficiently.

First objective is to make VFD design using the necessary operation to make it. It has main parts; i.e. rectifier, inverter and microcontroller which can control the process of VFD. After implementation all this we integrated it with the compressor of refrigeration device. At last our main objective is to prove the power saving phenomenon through different PWM techniques.

Project Implementation Method

The project comprises of three main parts, making of variable frequency derive, integration with refrigeration device and verifying the saved power through different PWM techniques.

Firstly design WAPDA-Excited 1?-Variable Frequency Derive (VFD), by taking line to ground 220V AC from WAPDA as source, which is fed into rectifier where 220V AC are converted into 311V DC, then it is supplied to inverter of H bridge topology. H Bridge consists of Power Mosfets with their gate driver circuitry separately. Correspondingly, Microcontroller (PIC18F452) using PWM techniques through which the pulses are generated to control the frequency of inverter output AC voltages. Moreover, Optocoupler is connected between microcontroller and inverter to provide electric insulation.

This working VFD having output AC with controlled voltage and frequency is integrated with the compressor of refrigeration device. With the help of temperature sensors to detect the cooling through VFD process and analyze the saved power. At the end, applying each PWM technique individually and compare each results of saving energy. The paper cover three main parts of this project i.e. inverter, PWM techniques and Analysis of different techniques to compare and quantify the best one to reduce power consumption. The main requirements of the project.

• Inverter
• Microcontroller based PWM
• Analysis of Pulse Modulation techniques

Inverter

The main working unit of VFD module is inverter, which required PWM technique to generate square wave having controlled frequency output voltages. Inverter design offer different topology, the simple one is H-Bridge. It based on four Power Mosfets which have fast switching speed of high deliverable power rating so they are used in VFD. Power Mosfets also requires tlp250 as their gate driver circuitry which also offers electrical insulation between inverter and Microcontroller. 

Microcontroller based PWM

Microcontroller PIC18F452 is used to generate PWM techniques which are supplied to the H-Bridge inverter. Firstly, using    Sinusoidal Pulse Width Modulation (SPWM) to generate square wave and pulse modulated square wave to feed into gate driver circuitry, which results in to control the frequency of output AC voltages. It helps to modify the frequency of resultant signal in a wide range of (30-50) Hz.

Analysis of PWM techniques

After complete working of VFD design and its integration with Induction motor, using SPWM to conclude the results of saved power. This paper also covers other PWM techniques to analyze each findings and figure out the technique that help consumers to save most power. These are as under;

• Modified Pulse Width Modulation (MPWM)
• Harmonic injection modulation (HIM)
• Hysteresis Pulse Width Modulation (HPWM)

Benefits of the Project

The basic function of a VFD in multiple applications is to provide energy savings. By controlling speed of a motor rather than switching ON and OFF it several times, energy savings can be substantial. A speed reduction of 20% can yield energy savings of 50%.  It help in describing that when speed reducing it yield energy savings, which is the main benefit of this project. For the country like Pakistan having energy crisis must need to decrease the power consumption to fulfill the consumers need. It is a great idea to reduce power consumption of the devices, to make life easier and working of applications more efficient.

Single phase induction motor are used all over the world, they have many number of benefits in our real life. So, with the help of VFD design we reduce the frequency and voltages of refrigeration devices. All around the work through this technique DC inverter AC and refrigerator works. Now a days, refrigerator is a basic need in life so it help to every home in saving their electricity cost and also benefits for the Power house to utilize the saving power in other areas. Moreover, the DC inverter Air conditioner and microwave oven also have great demand it also help in it.

Its number of benefits are as under:

• A VFD may be used for control of process temperature, pressure or flow without use of a separate controller. Suitable sensors and electronics are used to interface driven equipment with VFD. 

• Maintenance costs will be lower down, since lower operating speeds enhance life span for bearings and motors. 

• Eliminating throttling valves and dampers also does away with maintaining these devices and all associated controls. 

• A soft starter for motor is not required. 

• Controlled ramp-up speed in a liquid system can eliminate water hammer problems. 

• Benefit of VFD is to limit torque to a user selected level which helps to protect driven equipment that cannot tolerate excessive torque.

Since, in a developing country like Pakistan, where the demand and supply gap of the electrical energy is already swelling steadily, the modifications in the traditional refrigeration devices to reduce the impact of their inefficient power usage are not only important rather inevitable.

Technical Details of Final Deliverable

It contains the entire Frequency controlled refrigeration project with hardware implementation as well as software procedure. It’s hardware patching consists of Variable frequency derive through H-Bridge inverter and integration of Variable frequency derive with refrigeration device such as refrigerator or Air conditioner or water dispenser which used sensors.

 Similarly, the software of the project contains microcontroller coding through different PWM techniques and by comparing different techniques to show the power consumption is low and energy is saved. It also includes all research papers which are studied to provide information about what is change from previous VFD device based project. It elaborates through graph how the power saving technique works.

Final Deliverable of the Project

HW/SW integrated system

Core Industry

Energy

Other Industries

Others

Core Technology

Others

Other Technologies

Sustainable Development Goals

Decent Work and Economic Growth, Responsible Consumption and Production

Required Resources

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