Automatic Transfer Switch(ATS) for renewable energy and generator set, Thesis of Engineering

Download Automatic Transfer Switch(ATS) for renewable energy and generator set and more Thesis Engineering in PDF only on Docsity!

i

Table of Contents

List of Figures..............................................................................................................vi List of Tables..............................................................................................................viii

• CHAPTER I.................................................................................................................... Abstract.......................................................................................................................ix
• INTRODUCTION............................................................................................................
  • 1.1 Overview of the Study......................................................................................................
  • 1.2 Statement of the Problem................................................................................................
  • 1.3 Objectives........................................................................................................................
  • 1.4 Significance of the Study..................................................................................................
  • 1.5 Scope and Limitations......................................................................................................
• CHAPTER II...................................................................................................................
• LITERATURE REVIEW....................................................................................................
  • 2.1 Introduction.....................................................................................................................
  • 2.2 Transfer Switch................................................................................................................
  • 2.3 Types of Transfer Switch..................................................................................................
    • 2.3.1 Manual Transfer Switch.................................................................................................................
    • 2.3.2 Automatic Transfer Switch.............................................................................................................
  • 2.4 Typical Applications.........................................................................................................
    • 2.4.1 Utility — Generator........................................................................................................................
    • 2.4.2 Generator — Generator...............................................................................................................
    • 2.4.3 Three-source System....................................................................................................................
  • 2.5 Power Electronics...........................................................................................................
    • 2.5.1 Diodes...........................................................................................................................................
    • 2.5.2 Description of Solid State Relays.................................................................................................
    • 2.5.3 Diac...............................................................................................................................................
    • 2.5.4 Triac..............................................................................................................................................
    • 2.5.5 Transistor.....................................................................................................................................
  • 2.6 Arduino..........................................................................................................................
    • 2.6.1 Hardware......................................................................................................................................
    • 2.6.2 Software.......................................................................................................................................
  • 2.7 Review on Related Literature.........................................................................................
• CHAPTER III................................................................................................................
• METHODOLOGY..........................................................................................................
  • 3.1 Introduction...................................................................................................................
  • 3.2 Data Gathering...............................................................................................................
  • 3.3 Topology Selection.........................................................................................................
    • 3.3.1 Open-transition transfer switches...............................................................................................
    • 3.3.2 Closed-transition transfer devices...............................................................................................
    • 3.3.3 Soft closed-transition devices......................................................................................................
  • 3.4 Project Flow Chart..........................................................................................................
  • 3.5 Project Design................................................................................................................
    • 3.5.1 Voltage Regulator........................................................................................................................
    • 3.5.2 Opto-isolator................................................................................................................................
    • 3.5.3 Solid State Relay...........................................................................................................................
    • 3.5.4 Relay Switching Stage..................................................................................................................
    • 3.5.5 Contactor......................................................................................................................................
    • 3.5.6 Arduino Microcontroller..............................................................................................................
  • 3.6 Constructing the Circuit..................................................................................................
    • 3.6.1 Design for Circuit Board...............................................................................................................
    • 3.6.2 Copper Patterning........................................................................................................................
    • 3.6.3 Etching..........................................................................................................................................
    • 3.6.4 Drilling..........................................................................................................................................
    • 3.6.5 Soldering the Components..........................................................................................................
    • 3.6.6 Microcontroller............................................................................................................................
  • 3.7 Programming the Microcontroller..................................................................................
• CHAPTER IV................................................................................................................
• RESULTS AND DISCUSSION..........................................................................................
  • 4.1 Topology........................................................................................................................
    • 4.1.1 Delayed Transition.......................................................................................................................
  • 4.2 Circuit Design.................................................................................................................
  • 4.3 Modes............................................................................................................................
    • 4.3.1 Mode 1 (Grid to Generator Backup)............................................................................................
    • 4.3.2 Mode 2 (Grid to Renewable Backup)...........................................................................................
  • 4.4 Manual Operation..........................................................................................................
  • 4.5 Test and result...............................................................................................................
  • 4.6 Oscilloscope simulation..................................................................................................
    • 4.6.1 Grid to Generator delay timing....................................................................................................
    • 4.6.2 Generator to Grid Delay Timing...................................................................................................
  • 4.7 Bill of Materials..............................................................................................................
  • 4.8 Specs of the Automatic Transfer Switch.........................................................................
  • 4.9 Comparison of Prices......................................................................................................
    • 4.9.1 Developed Automatic Transfer Switch........................................................................................
  • 4.10 Product from the Market.............................................................................................
• CHAPTER V.................................................................................................................
• CONCLUSION AND RECOMMENDATION......................................................................
  • 5.1 Conclusion......................................................................................................................
  • 5.2 Recommendation...........................................................................................................
• Bibliography...............................................................................................................
• Appendices.................................................................................................................
  • Appendix A: DIY-Duino........................................................................................................
  • Appendix B: Triac BT136......................................................................................................
• Appendix C: PC817 Optocoupler..........................................................................................
• Appendix D: MOC3021.........................................................................................................
• Appendix E: Documentation................................................................................................
• Appendix F: Comparison of Prices (based on the market)....................................................
• Figure 1 Manual Transfer Switch........................................................................................ List of Figures
• Figure 2 Manual Load Transfer Switch...............................................................................
• Figure 3 Standard Application Utility - Generator............................................................
• Figure 4 Standard Application Generator - Generator.......................................................
• Figure 5 Three Source System...........................................................................................
• Figure 6 Device Package and Schematic...........................................................................
• Figure 7 The internal circuitry of a typical solid state relay..............................................
• Figure 8 DIAC Symbol......................................................................................................
• Figure 9 TRIAC schematic symbol...................................................................................
• Figure 10 Symbol of a Transistor......................................................................................
• (d) layout............................................................................................................................ Figure 11 BJT transistor: (a) PNP schematic symbol, (b) physical layout (c) NPN symbol,
• Figure 12 Types of Field-Effect Transistors......................................................................
• Figure 13 Schematic Diagram of the Automatic Transfer Switch.....................................
• Figure 14 System Circuit Diagram....................................................................................
• Relays and Manual Disable Switch................................................................................... Figure 15 Photograph of Automatic Controller Installed on the Wall showing the Timers,
• Figure 16 Circuit of a 5V Regulated Power Supply..........................................................
• Figure 17 Solid State Relay Circuit...................................................................................
• Figure 18 ATMega328.......................................................................................................
• Figure 19 Design in Eagle Software..................................................................................
• Figure 20 Design for the PCB............................................................................................
• Figure 21 PCB Ironing.......................................................................................................
• Figure 22 Etching the Layout............................................................................................
• Figure 23 PCB Output.......................................................................................................
• Figure 24 Circuit of the Arduino.......................................................................................
• Figure 25 Open Transition.................................................................................................
• Figure 26 Circuit of the ATS.............................................................................................
• Figure 27 Photograph of the Actual automatic Transfer switch........................................
• Figure 28 Timing Diagram for Generator..........................................................................
• Figure 29 Main Source is on-state.....................................................................................
• Figure 30 Error Indicator...................................................................................................
• Figure 31 Generator Setup.................................................................................................
• Figure 32 Timing Diagram for Renewable........................................................................
• Figure 33 Photograph of the Switch..................................................................................
• Figure 34 Manual Switch...................................................................................................
• Figure 35 Manual Operation for the Mains and Backup source........................................
• Figure 36 Grid to Generator delay timing..........................................................................
• Figure 37 Generator to Grid Delay Timing.......................................................................
• Figure 38 50-Amp, 11KW, Manual and Automatic Transfer Switch, single phase..........
• Figure 39 50-Amp, 10kw Automatic Transfer Switch w/ 10-Circuit Load Center
• Figure 40 Automatic transfer switch grid-generator, integrated 62Amp...........................
• Figure 41 Critical Rate of Rise Test Circuit......................................................................

List of Tables Table 1 Summary of Tests and Results.............................................................................. 47 Table 2 Bill of Materials.................................................................................................... 50 Table 3 Other Expenditures............................................................................................... 51 Table 4 Index of Arduino Board........................................................................................ 57 viii

generator and shifts the load to the generator as well as if the backup source is renewable it directly shifts the load to the renewable. The controller keeps on monitoring the grid voltage and when it comes back on the system turns off the generator or renewable and transfers the load to the grid. The methods employed in designing the ATS involve the use of contactors, voltage detector, solid-state relay and a microcontroller (atmega328) as the main components of the system and also to improve the speed of the system. The system also has an alarm system for indicating generator failure. In this paper the researcher proposed a low cost system which can be built using the commonly available components such as relays, contactors, diodes, capacitors and microcontroller. x

CHAPTER I

INTRODUCTION

1.1 Overview of the Study Electricity is one of those discoveries that have changed the daily life of everybody on the planet. Electricity is the key component to modern technology and without it most of the things that we use every day simply could not work, and would never have been created. Our mobile phones, our computers, the Internet, our heating systems, our televisions, and our light bulbs - nearly everything in the home would be completely different. There would be completely different systems put in place in the home to ensure that we can remain warm, and to ensure that we can live properly every day. That is why many facilities uses generator sets (gensets) to supply or to maintain power when there is an outage or major power failure. Homes with standby generators may use a transfer switch for a few circuits or the whole home. Different models are available, with both manual and automatic transfer. A transfer switch prevents the utility power and the generator power from powering your household circuits at the same time. When the utility power goes out, you simply plug your generator into the transfer switch, start it up, and flip the transfer switch or switches from the utility position to the generator position. Direct connection without a transfer switch can result in damage to your home and generator and great harm to utility workers. With a manual transfer switch in place, the homeowner would first have to make his way to the service entrance panel. Many times, this would be done in the dark with a flashlight in hand. Prior to switching over to standby power, the homeowner would have to shut off individual breakers for nonessential branch circuits so as to shed part of the load and size it down to match the capability of the standby power plant. 1

applicable if you have a renewable power source or generator set. Automatic transfer switch is a good one since it is safer, extremely convenient to use and has a low cost. 1.5 Scope and Limitations The scope of the study will focused on implementing a small scale and low cost automatic transfer switch for renewable energy and generator set and compare it with the result of the simulation test. The study limits specifically, a 5kW or less automatic transfer switch. 3

CHAPTER II

LITERATURE REVIEW

2.1 Introduction Power instability in developing countries has necessitated the need for automation between public power supply and alternative generators to back up the utility power supply, and as the rate of power instability becomes predominantly high the need for automation also becomes high. And since most industrial and commercial processes require uninterrupted power supply, if the process of power supply changeover is manual, it will not only waste time by slowing the process, but could also cause device, process or product damage. There could also be error during the manual changeover as a result of human factor, and this in some cases can lead to massive loss of revenue. One of the most critical needs of an embedded system such as this is to decrease cost and space and this is achieved in this work. It has been observed over the years that power instability has caused companies to lose millions of dollar each time there is power failure, as a result of the time lag between power failures and when power is restored. This can be seen clearly in companies like telecommunications, breweries, cold rooms to mention but a few. This system was designed to offer solution to the shortcomings of the already existing manual changeover by performing power swap from public power to generator automatically and vise-versa. It has the ability to eliminate the stress of manually switching on the generator when there is public power failure. 2.2 Transfer Switch A transfer switch is an electrical switch that switches a load between two sources. Some transfer switches are manual, in that an operator effects the transfer by throwing a 4

2.3.1.1 Turning on the Generator Manually In order to turn the generator on, the user moves the generator ON/STOP switch to ON position, AC ON/OFF switch to OFF position and pushes the self-start button momentarily for 2-3 seconds. 2.3.1.2 Connecting the Load to the Generator Manually When the generator starts, the user waits a couple of seconds for the generator prime mover to stabilize to a constant rpm. When the voltage stabilizes, the user moves the AC ON/OFF switch to the ON position to connect the load to the generator. It normally takes 2-3 seconds for the output of the generator to stabilize. 2.3.1.3 Transferring the Load Manually between the Generator and Grid If there are two power sources such as a grid and the generator, the load has to be shifted between them. When the grid power is available, the load is connected to the grid. Otherwise, the user starts the generator manually and connects the load to the generator. If the load has to be connected or disconnected from the grid and transferred to generator and back, the user needs a double pole double throw (DPDT) switch which 6 Figure 2 Manual Load Transfer Switch

disconnects the one power source and connects the other power source to the load. This is shown in Fig. 2. 2.3.1.4 Monitoring the Grid Power Manually In order to monitor the grid power, the user installs an indicator light directly on the grid voltage before the load switching circuitry as shown in Fig. 2 and keeps monitoring the indicator from time to time to find out that the power has resumed and then returns the load to the grid by changing the position of the DPDT switch. [1] 2.3.1.5 Turning Generator Off Manually The generator is turned off by switching the generator ON/STOP button to STOP position. Below are some of the limitations of manual changeover switch box. (i) Time wasting whenever there is power failure (ii) It is strenuous to operate (iii) It is causes device, process or product damage (iv) It can cause fire outbreak (v) It makes a lot of noise. (vi) Maintenance is more frequent as the changeover action causes wears and tears. 2.3.2 Automatic Transfer Switch This type of changeover system has an automatic transfer switch, which monitors the alternating current (AC) voltage coming from the utility company line for power failure conditions. Upon detection of power failure for predetermined period of time, the standby generator is activated (started), after which the load is transferred from utility to 7

short enough to connect the backup power source all the while meeting city, state and federal codes. James Naas, Generator Sales Manager at Diesel Service and Supply, stated that many companies will also buy an uninterruptible power supply battery to restrain any time delays. Once normal power is restored, another time delay is needed to ensure the load is stable enough to switch from backup power. Typically, this delay is between zeros to thirty minutes. The control panel should automatically bypass this time delay in returning to the normal source if the new or used generator fails and the normal source of power is working properly again. The third most common time delay involves a cool down period for the engine. During this time period the controls run the engine unloaded before shutting it off. In most instances it is usually desirable for the load to be transferred to the backup generator as soon as the proper voltage and frequency are reached. However, in some situations end users want to sequence different transfer switches onto the backup generator. When this application is required the controls should include an additional time delay which can be adjusted on each transfer switch so that the loads can be transferred to the new or used generator in whatever order desired. 2.4 Typical Applications 2.4.1 Utility — Generator Transfer switches are traditionally applied between a utility and a generator set for emergency and standby power systems. 9

2.4.2 Generator — Generator Transfer switches are sometimes applied between two generator sets for prime power use, often in remote installations. In such applications, source power is periodically alternated between the generator sets to equally share run time between the two. 10 Figure 3 Standard Application Utility - Generator Figure 4 Standard Application Generator - Generator