Abstract
Single-phase to three-phase conversion using power electronics converters is use in various aims like for traction and microgrid etc. Regarding this configuration considered over the years, it can be observed two main tendencies:
1) configurations with reduced number of semiconductor switches; and
2) configurations with increased number of semiconductor switches.
The goal of PE in the aforementioned applications is to control the flow of energy from an electrical source to an electrical load, to take a specific need with high efficiency, high reliability, small size, light weight, high availability and low cost.
The single phase to three phase ac to ac direct conversion configurations and those which purpose to reduce the dc-link capacitor.
The conversion of variable frequency three phase supply from variable or fixed frequency single phase supply is possible without using DC link capacitor. Hence the size of this converter is small and also the weight of the converter is light.
CHAPTER 1: Introduction
1.1 Problem Summary and Introduction
The implementation of converters without DC energy storage contributes to lower costs, smaller size, greater reliability and longer working life of converters and as well as to whole systems. Converters without a DC-link are frequently seen as a future concept for specific applications, but despite intensive research over several decades they have until now achieved only low industrial penetration.
The absence of a DC-link energy storage electrolytic capacitor, increases power converter lifetime, subsequently making them more reliable.
1.2 Aim and objectives of the project
The main purpose of the direct conversion of variable frequency three phase supply from Fixed or variable frequency single phase supply is to remove the DC filter capacitor from the power electronics circuit to reduce the weight of the circuit and also reduce the size of the circuit and it becomes more reliable due to not using electrolytic capacitor therefore converter have more life.
The another purpose is to employ the three phase drive using single phase supply and torque and speed control the three phase motor.
The three phase drive using single phase supply is extensively used in traction system to drive the three phase traction motor and also drive the auxiliary three phase motor to drive the auxiliary load such as compressor , blowers , pump etc. more than a dozen.
The single phase to three phase converter is extensively used in domestic appliance like submersible pump motor and commercial appliance.
1.3 Why not DC link/DC Capacitor ?
The DC filter capacitor is so much Bulky.
The output of Rectifier and DC filter capacitor is not a pure DC.
The size of DC filter capacitor is Large.
1.4 Brief literature review
In the power distribution systems, the single-phase grid has been considered as an alternative for rural or remote areas, due to its lower cost feature, especially when compared with the three-phase solution. In huge countries like Brazil, the single phase grid is common due to the large area to be covered. However in other side, loads connected in a three phase arrangement present some advantages when compared to single-phase loads. This is true when motors are considered, due to the inconstant torque, constant power, reduced size, etc. There is a required for single-phase to three phase conversion systems in this scenario.
In terms of application, the first thing that is come to mind when it is considered a single-phase to three-phase conversion, it is a three-phase motor drive system. However, the authors in claim that, in rural application, feeding a three-phase induction motor is not any more the main concern for the single phase to three-phase conversion. Due to the evolution of the farm technology, some of the local loads (such as electronic power converters, computers, communication equipments, etc.) require high power quality, that is symmetrical, sinusoidal, and balanced three-phase voltage.
In the past, single-phase to three-phase conversion systems were made possible by using rectifier and inverter pair.
Block diagram of prior technology
Fig. 1.1 Block diagram of prior technology
Block diagram of converting single phase to three phase power supply consist of input, rectifier, filter, inverter, load, driving stage, micro-controlled and power supply. As we seen from the block diagram the first stage is input, input is given in two circuits, first one is given to rectifier and further towards the other and the second input is given to controller stage. Since the input is first works in rectifier which converts the ac supply into pulsating dc but after rectification also having some ac contain. So to remove that filters are used consisting of inductors and capacitors which helps to eliminate the ac contain and gives nearly pure dc.
In this method we have required DC filter capacitor which is high rating therefore it’s size and weight is more hence it’s cost is also more. In this method we are using aluminium electrolytic capacitor therefore it’s ageing of aluminium electrolytic capacitors is expressed by the increase in their internal resistance RESR. The electrolytic capacitor equivalent impedance Z (s) is modeled by an equivalent circuit according to a which consists of a series connection of the true capacitance C, an equivalent series resistance RESR representing all AC losses, and an equivalent series inductance LESL which depends on the winding design of the capacitor foils and how the foils are connected to the capacitor terminals.
Now we are using single phase three phase converter without DC link so we have compare to less component and less value of capacitor is required so we increasing its performance, smaller size, greater reliability and longer working life of converters.
Block diagram of single phase to three phase converter without DC link
Fig. 1.2 Block diagram of single to phase three phase converter without DC link
In this system we are supply single phase supply and directly convert it into three phase and give to load.
A phase converter is a device that converts electric power provided as single phase to three phase. These converters are used to produce three phase electrical power from a single phase source, thus allowing the operation of three phase equipments at a site that only has single phase electric service.
There are drawbacks of conventional power converter using electrolytic capacitors. A large capacitance electrolytic capacitor Which must Withstand a high level of DC voltage has a relatively limited operating lifetime. The effective operating life time of a power converter as whole will in general be determined by this smoothing electrolytic capacitor. Breakdown of such an electrolytic capacitor can cause serious damage to other components of the power converter, since leakage of corrosive electrolyte may occur, or the capacitor may even explode.
Because of electrolytic characteristics, other components such as balancing resistors and high frequency capacitor are required. These additional components increase not only cost but also board space to mount them.
The smoothing electrolytic capacitors occupy a relatively large amount of space Within the power converter, thereby reducing the freedom available for mechanical design of the converter, and causing the overall size of the power converter to be large.
The power converter manufacturers and research community recognize above problem and realize improvement of AC drive product can be made if electrolytic capacitors are to be replaced.
US. Pat. Nos. 5,729,450, 5,623,399, 6,115,270 and 6,449,181B1 propose to use capacitor in place of electrolytic ones to provide ripple current capability to the inverter section. US. Pat. No. 5,623,399, US. Pat. No. 6,115,270 and US. Pat. No. 6,449,181B1 are invented for new electric vehicle applications Where a battery is readily available to serve as a huge energy storage component in front of the inverter.
The other patent US. Pat. No. 5,729, 450 is in effect teaching for inverting energy from a fuel cell DC source to AC power. The fuel cell has low impedance and again serves as the huge energy storage and imposes smoothing effort on the DC link.
Conventional AC power converter has working condition Where transient energy can come back from the motor to the DC link. In this case the DC link is easily over charged, resulting in DC link over-voltage. This over voltage may damage the converter components such as the switching transistors. Thus their solution is not readily applicable to a conventional AC power converter With a diode front end rectifier.
1.5 Project Management
Project planning and scheduling
We are going to complete this project these different steps as following :
1. Project development approaches
2. Project plan
1.5.1 Project development approaches
First, we will design the power electronics circuitry which convert the variable frequency three phase supply from fixed or variable frequency single phase supply.
Then, we will simulate this power electronics circuitry by giving appropriate sequence of gate triggered pulses to turn on or turn off the power electronics device or power electronics switches.
After the simulating the power electronics circuitry called as single phase to three phase converter, we will analyze the results or output waveforms for make sure with the single phase to three phase converter is work properly.
Now, the challenges are to design the control circuit or firing circuit to drive the power electronics device or power electronics switches to produce the appropriate output waveform at the output terminal.
We will design the gate driving circuit by using ZCD (zero crossing detector) and square wave generator or function generator such a manner that they will be drive the single phase to three phase converter in appropriate manner such that they will produce the appropriate output waveform.
Finally, we will design the AC filter such that the % THD of three phase output waveform is below the permissible limit and In other words, they will reduce the harmonics at the output waveform.
1.5.2 Project plan
Now , we will prepare the plan for the complete the project work on the single phase to three phase converter without DC link.
First , we will decide that first , we will design that the power electronics circuitry such that they convert the variable frequency three phase supply from fixed or variable frequency single phase supply.
Then , we will simulate that circuit to make sure that they will perform accurately and produced a appropriate three phase output waveform.
Now , the second step is design of control circuit or firing circuit to drive the power electronics device or power electronics switches to produce the appropriate output waveform.
In the third and final step , we will design the AC filter to produce the appropriate three phase output waveform.
In the filter design , we will design the AC filter such that the % THD of three phase output waveform is below the permissible limit and In other words , they will reduce the harmonics at the output waveform.
1.6 Materials / Tools required :
Mosfet or gto
Op amp
Inductors
Capacitors
Timer IC555
PCB
Dead band generator
Zero crossing detector
Auto coupler
CHAPTER 2: Design Methodology and implementation strategy
We started with developing a way to directly convert ac to ac single phase to three phase converter without dc link hence converter becomes more reliable, less in weight and reduced size comparatively prior AC-DC-AC converter.
2.1 AEIOU Summary
Fig 2.1 : AEIOU Summary sheet
Activity
Drilling
Welding
Milling
Polishing
Pressing
Shopping
Farming
Teaching
Testing
Travelling
Environment
Noisy
Dusty
High temperature
Natural cooling
Heating
Radiation
Thermal discomfort
Ventilation
Humidity
Objects
Railway
Hoist
Air conditioner
Compressor
Submersible pump motor
Grinder
Lift
Pump
Interaction
Observations
Engineers and labours on construction site
Lab assistant and student
Managers and employee
Welder and supervisor
Professor and student
Elements
Welding machine
Lift
Drilling machine
Hoist vehicles
Testing instruments
Scene
Wiring
Driving
Testing
Measuring
Office work
Users
Metal working workshop
Railway employee
Industry worker
Welder
Engineers
Driller
Farming
Irrigation system
Vehicle servicing
2.2 EMPATHY :
Users
Irrigation system
Farmers
Vehicle servicing
Metal working workshop
Large building
Industry
Stakeholders
Farmer
Supervisor
Vehicle owner
Instrument engineer
Electrical engineer
Industry worker
Activities
Drilling
Welding
Milling
Polishing
Pressing
Driving
Farming
Wiring
Testing
Teaching
Fault repairing
Researchin
Fig. 2.2 empathy sheet
2.3 Ideation Canvas :
Fig 2.3 Ideation canvas
People
Electrician
Driver
Engineer
Farmer
Manager
Professor
Lab assistant
Researcher
Student
Railway engineer
Scientist
Supervisor
Technician
Worker
Activities
Wiring
Driving
Learning
Teaching
Traction
Inventory system
Maintenance
Working on safety system
Estimating cost
Travelling
Testing
Farming
Milling
Planting
Polishing
Drilling
Situation / Context / location
Measuring
Water pumping
Industry
Testing
Irrigation
Railways
Maintenance
Rainy
Laboratories
Cleaning
Construction site
Props / Possible Solutions
Light in weight
Less THD
Reduce in size
Reducing harmonics
LC filter required
2.4 Product Development Canvas :
Purpose
Convert single phase to three phase supply
To employ single phase to three phase electric drive
Provide variable frequency three phase supply
Reduce weight of converter
Drive three phase traction motor
Product Experience
Light in weight For Higher Frequency
Portable
Better performance Maintenance free
Efficient
Product Functions
To convert single phase to three phase supply
Light in weight
Reduce in size
Drive three phase motor
Fig 2.4 : Product Development Canvas
Customer Revalidation
Cost ****
Reliability *****
Performance *****
Portability *****
Efficiency of power transfer ****
People
Engineer
Manager
Electrician
Worker
Farmer
Lab assistant
Technician
Professor
Railway engineer
Product Features
Reliable
Portable
Better performance
Efficient
Light in weight
Components
Semiconductor devices
Op-Amp
Zero crossing detector
Indicator
Adder
Capacitor
Transformer
GTO / MOSFET
Inductor
Substractor
Dead band generator
Reject , Redesign and Retain
AC filter is required.
Harmonics
Switching loss
Converter is small in size and light in weight for higher frequency.
LC filter is small in size and light in weight for higher frequency.
This converter is implementing for less industrial application because of semiconductor’s behaviour. This converter is now research and development under scientist and researcher and students. Ac to ac converter is demanded in industry with better performance because of more reliability.
For design this converter we study converters which are single phase to three phase converter (prior technology), ac to ac converter, rectifier (ac to dc), inverter(dc to ac). For single phase to three phase converter we are using prior technology we have to use two converters rectifier and inverter and also required to large dc filter.
These canvases show the stage by stage progress that we have made for implementing the idea..
CHAPTER: 3 IMPLEMENTATION
3.1 Firing Circuit OR Control Circuit
Waveform Of Firing Pulses (Output Three Phase Supply Frequency is 100 Hz)
3.2 Firing angle table
Firing Angle
MOSFET 1
0 to 180
MOSFET 2
180 to 360
MOSFET 3
–
MOSFET 4
–
MOSFET 5
120 to 180
MOSFET 6
300 to 360
MOSFET 7
0 to 120
MOSFET 8
180 to 300
MOSFET 9
0 to 60
MOSFET 10
180 to 240
MOSFET 11
60 to 180
MOSFET 12
240 to 360
Note : The Firing angle is only for the Frequency of input single phase supply is 50 Hz and the frequency of output three phase supply is 50 Hz.
3.3 Single phase to Three Phase converter(MOSFET)
3.3.1 Power Circuit
3.3.2 Firing Circuit
3.3.3 Voltage Controlled Circuit
3.3.4 Speed of Three Phase induction Motor (1000rpm)
3.3.5 Waveform of Three Phase Output Current
3.3.6 THD of Three Phase Output Current
3.3.7 Waveform of Three Phase Output Voltage
3.3.8 THD of Three Phase Output Voltage
CHAPTER: 4 SUMMARY
4.1 Advantages of our work
1. It converts single phase to three phase with a slight unbalance in voltage.
2. Imagine a three phase motor running from three phase input then one line gets disconnected. What happens may surprise many ; the motor continues to run and deliver the load (But reduce torque) with slight drop in speed.
3. It converts single phase to three phase with a slight unbalance in current.
4. DC filter capacitor is not required.
5. Light in weight for higher output frequency because of reduce the weight of AC filter.
6. Portable
7. Reliable
Because here we are using small value of capacitor for reducing harmonics. Hence we use are not using electrolytic capacitor. Because of electrolytic characteristics, other components such as balancing resistors and high frequency capacitor are required. These additional components increase not only cost but also board space to mount them.
4.2 Limitations
1. Harmonics will be present in output waveform. AC filter (L-C filter) is required.
2. To employ VVVF (variable voltage variable frequency) drive or variable frequency drive is difficult. It can be solved by control circuit.
4.3 Unique features of project
The single phase to three phase converter is successfully drive the three phase motor using only single phase supply.
The single phase to three phase converter is successfully operate a three phase submersible pump motor on a single phase line. Proper installations can be achieved only if the recommendations and specifications of both the single phase to three phase converter and submersible pump motor manufacturers are followed.
The conversion of variable frequency three phase supply from fixed or variable frequency single phase supply is possible using only single power electronics circuitry called single phase to three phase converter. There is no need of DC filter capacitor for filter the rectifier output. So the size of the single phase to three phase converter is small and also the weight of the single phase to three phase converter is light.
If the one of the phase of three phase line is disconnected then the large voltage unbalance is not hazardous effect on power system because of the only single phase electric power is feed to the electric load.
4.4 future work.
The major scope of single phase to three phase converter in traction system to drive the three phase traction motor using only single phase supply. So only one conductor is used in track electrification. (the neutral conductor is as ground used as rail-track) So the conductor required to track electrification is reduce. So the cost of conductor is reduced and finally the cost of track electrification is reduced. And also the torque and speed control of three phase traction motor is achieved.
The another scope of single phase to three phase converter in implementation of three phase electric drive using only single phase supply. And also the torque and speed control of three phase motor.
The single phase to three phase converter is extensively used in domestic appliance like submersible motor. The single phase to three phase converter is successfully operate a three phase submersible pump motor on a single phase line. Proper installations can be achieved only if the recommendations and specifications of both the single phase to three phase converter and submersible pump motor manufacturers are followed.
The single phase to three phase converter is used extensively on railways electric locomotives for driving three phase motor load of auxiliary drives like compressors , blowers , pumps etc. more than a dozen.
The single phase to three phase converter is used extensively on Hoist, welder, wheel balancer, pumps, compressor, irrigation system, air conditionin, refrigeration unit, conveyor, crane, grain mill lathe machines, drilling machine, milling machine, grinder, saw, polisher, shaper, CNC machine etc.
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