"InvertersBy: 1 ContentsAbstract .................................................................................................... Error! Bookmark not defined.Dedication ................................................................................................ Error! Bookmark not defined.Chapter 1. ............................................................................................................................................... 61.1 Introduction ............................................................................................................................ 61.2 Project Aims .................................................................................................................................. 71.3 The Project Structure .................................................................................................................... 7Chapter 2 ................................................................................................................................................ 82.1 Introduction ............................................................................................................................ 82.2 History of Inverters ................................................................................................................. 82.3 DC (Direct Current) and AC (Alternating Current) ........................................................................ 92.4 The need for inverters ................................................................................................................ 102.4.1The efficiency of converting DC to AC .................................................................................. 112.5 Benefits and functions of inverters ............................................................................................. 112.6 Types of inverters and waveforms. ............................................................................................. 122.7 Rotary Inverters .......................................................................................................................... 132.8 Static Inverter .............................................................................................................................. 142.9 Inverter use and sizing ................................................................................................................ 15Chapter 3 .............................................................................................................................................. 163.1 Sizing an inverter for an off grid load .......................................................................................... 163.2 Introduction ................................................................................................................................ 163.3 Renewable Resource at site ........................................................................................................ 17Wind Resource at the Site................................................................................................................. 173.4 Site Obstacles .............................................................................................................................. 183.5 Roughness Class .......................................................................................................................... 183.5 System Sizing ............................................................................................................................... 203.6 Battery Selection ......................................................................................................................... 213.7 Turbine Sizing .............................................................................................................................. 213.8 Turbine Selection ........................................................................................................................ 223.9 PV Sizing ...................................................................................................................................... 233.10 PV Panel Selection..................................................................................................................... 243.11 Charge Controller ...................................................................................................................... 253.12 Inverter ..................................................................................................................................... 263.12 Homer Results ........................................................................................................................... 263.13 Discussion.................................................................................................................................. 31Chapter 4 .............................................................................................................................................. 322 4.1 Introduction ................................................................................................................................ 324.2 Triangle Wave Generator ............................................................................................................ 334.3 Op Amp ....................................................................................................................................... 344.4 MOSFETS ..................................................................................................................................... 354.5 Differences between BJT and MOSFET ....................................................................................... 364.6 MOSFET as a Switch .................................................................................................................... 364.7 Types of MOSFET ........................................................................................................................ 364.8 How a MOSFET works ................................................................................................................. 374.9 Uses for MOSFETS Vs FET ............................................................................................................ 374.10 Where to connect the load on a MOSFET? Source or Drain? ................................................... 374.11 Where to connect the heat sink ............................................................................................... 374.12 What is the purpose of the body diode? .................................................................................. 374.13 Heat Sink ................................................................................................................................... 384.14 Choosing a Heat Sink ................................................................................................................. 394.15 Capacitors ................................................................................................................................. 394.16 Capacitor Circuit ........................................................................................................................ 404.17 Capacitor Applications .............................................................................................................. 414.18 Resistors .................................................................................................................................... 414.19 Resistor colour bands ................................................................................................................ 424.20 Parallel and Series Resistors ..................................................................................................... 444.21 Series Resistors ......................................................................................................................... 444.22 Parallel Resistors ....................................................................................................................... 444.23 Resistor Applications ................................................................................................................. 454.24 Voltage Dividers ........................................................................................................................ 464.25 Pull -up Resistors ....................................................................................................................... 47Chapter 5 ............................................................................................................................................... 485.1 Introduction ................................................................................................................................ 485.2 Build of the DC to AC inverter ..................................................................................................... 485.3 The Power Stage ......................................................................................................................... 525.4 Discussion .................................................................................................................................... 535.5 Appendix ..................................................................................................................................... 54References ............................................................................................................................................ 59Figure 1: Wiring circuit with an inverter. (CIRCULAR ENERGY, 2015) ................................. 6Figure 2: Power Inverter ........................................................................................................ 83 Figure 3: David Prince’s rectifier & inverter circuits. (Owen, 1966) ........................................ 9Figure 4: Modified sine wave and Sine wave. (ABS Alaskan, 2014) .................................... 13Figure 5: A typical rotary converter station. (Blalock, 2015) ................................................. 14Figure 6: Wind rose calculator ............................................................................................. 17Figure 7: Image of site ........................................................................................................ 18Figure 8: Danish wind speed calculator. .............................................................................. 20Figure 9: Vision battery ....................................................................................................... 21Figure 10: LE-V50 wind turbine ........................................................................................... 22Figure 11: Wind turbine specifications ................................................................................. 23Figure 12: PV Panel ............................................................................................................ 24Figure 13: Charge Controller ............................................................................................... 25Figure 14: Doxin Inverter. .................................................................................................... 26Figure 15: Cash Flow Summary .......................................................................................... 27Figure 16: The monthly average electricity produced. ......................................................... 27Figure 17: Cash Flow Summary .......................................................................................... 28Figure 18: The monthly average electricity produced. ......................................................... 29Figure 19: Cash flow summary ............................................................................................ 29Figure 20: Monthly average electricity production ............................................................... 30Figure 21: The different systems compared. ....................................................................... 30Figure 22: Schematic of triangular wave circuit. .................................................................. 33Figure 23: 741 Operational Amplifier. .................................................................................. 34Figure 24: MOSFET (OscarLiang.net, 2015) ....................................................................... 35Figure 25: N-Channel & P-Channel MOSFET (OscarLiang.net, 2015) ................................ 35Figure 26: N channel and P channel MOSFETs (OscarLiang.net, 2015) ............................. 36Figure 27: Heat Sink. (Parker, 2010) ................................................................................... 38Figure 28: Capacitor connected to a battery. (How Stuff Works, 2015) ............................... 40Figure 29: A capacitor, battery and bulb connected together. (How Stuff Works, 2015) ...... 40Figure 30: Resistor Symbols. (Sparkfun) ............................................................................. 41Figure 31: The internal film in resistors. (Sparkfun) ............................................................. 42Figure 32: Resistors with different values. (Sparkfun) ......................................................... 42Figure 33: Resistor colour band table. (Sparkfun) ............................................................... 43Figure 34: A 10 Kilo ohm resistor. (Sparkfun) ...................................................................... 434 Figure 35: Resistors in series. (Sparkfun) ........................................................................... 44Figure 36: Resistors in Parallel. (Sparkfun) ......................................................................... 44Figure 37: Resistor connected in series with LED. (Sparkfun) ............................................. 45Figure 38: Voltage divider circuit. (Sparkfun) ....................................................................... 46Figure 39; Pull-up resistor circuit. (Sparkfun) ...................................................................... 47Figure 40: Triangular wave circuit diagram. ......................................................................... 48Figure 41: The components are soldered onto the vero board. ........................................... 49Figure 42: The pots are connected up to the circuit. ............................................................ 50Figure 43: Square-wave on the oscilloscope. ...................................................................... 50Figure 44: Triangular wave on the oscilloscope. .................................................................. 51Figure 45: The triangular wave and the square wave on the oscilloscope. .......................... 51Figure 46: Circuit used for the Power Stage. ....................................................................... 52Figure 47: Inverting stage & Power stage. ........................................................................... 53Figure 48: IRF 520 MOSFET data sheet. ............................... Error! Bookmark not defined.Figure 49: 741 OP Amp Data Sheet. ...................................... Error! Bookmark not defined.5 Chapter 1. 1.1 IntroductionOver the years there have been significant developments in the power electronicssector. Power electronic devices have also progressed with advancements in controllingpower systems by using digital signal processors. An inverter is essentially an electronicdevice that changes Direct Current (DC) to Alternating Current (AC) power. There are manydifferent types of inverters and they can be very complex. Inverters are used in manydifferent technologies such as PV panels, wind turbines, hydro turbines or even in a car.Inverters are everywhere for instance if you are travelling a long journey and your phonebattery is nearly empty you can re charge it by plugging it into the cigarette lighter. Theconnection from the phone to the cigarette lighter is a 12v adapter which contains aninverter. Other applications such as television and DVD players can also be powered by thecar battery. Again the television/DVD player is connected to the cigarette lighter via aninverter. The inverter converts the cars 12 volt DC power to 120V AC. This allows theRMS television/DVD player to be plugged in and operated the same as you would in thehouse.Error! Reference source not found.Figure 1: Wiring circuit with an inverter.Error! Reference source not found.6 Figure one above is just one example of where inverters are used in every day. Figure oneshows a house that is connected to the grid and also the PV solar panels. The sun hits thesolar panels, the PV panels then turn the energy from the sun into electricity (direct current).The inverter is then used to change the DC power to AC power so that the power can beused in homed to power various appliances. The house is also connected to the utility gridtherefore when the PV solar panel is not producing enough electricity to need the house holddemands electricity can also bought from the utility grid. When the house hold electricitydemand is low the excess electricity can also be sold back to the grid. Error! Referencesource not found.Put in aims, objectives, etc. 1.2 Project AimsThe following bullet points are the aims that are hoped to be achieved by this project.? Research and understand the workings of a DC to AC inverter.? Build a working DC to AC inverter.? Learn from the project.1.3 The Project StructureThis project will be broken up in to two main sections. The first section will be research in towhat exactly a DC to AC inverter is and why they are necessary for everyday use. There isalso a chapter on sizing an inverter for an off grid load. The second section mainly involvesthe research of the various different components needed to build the inverter and the actualbuild of the inverter. 7 Chapter 22.1 IntroductionChapter 2 will look at the first inverters used and how inverters have developed andchanged over time to adapt to modern sensitive devices. In this section the differencesbetween DC (Direct Current) and AC (Alternating Current) are outlined. This chapter will alsoinvestigate the function of a DC to AC inverter and why inverters are needed today. Thedifferent types of inverters and waveforms are also investigated in detail, such as true sinewave inverters, square wave inverters, modified sine wave inverters. This chapter also looksat what electronic devices use inverters and why inverters are so important in moderntechnology. Figure 2: Power Inverter2.2 History of InvertersIt is very hard to pin point exactly who developed the term inverter but in 1925 David Princepublished an article in the GE Review (vol.28, no.10, p.676-81) cited “the inverter”. Thearticle wrote by David Prince contained practically all the relative and key informationrequired by the most modern inverters today. In the article David Prince describes that aninverter is a device that converts direct current (DC) to alternating current (AC). By the year1935 David Princes inverter featured in books all over the world, it was also wrote in differentlanguages to accommodate any translation difficulties. In 1925 David Prince defined inverter8 as the inverse of rectifier. The term rectifier was in common use for more than two decadesprior to 1925 which was understood to mean any stationary apparatus or rotatingcommutator for transforming AC to DC. Rotary converters which were later calledsynchronous converters were used in 1892 to convert AC power to DC power. Rotaryconverters were manufacture until the 1950s when they were replaced by germaniumdiodes.Error! Reference source not found.Figure 3: David Prince’s rectifier & inverter circuits.Error! Reference source not found.The first power inverters were electro mechanical devices. Direct current flowed down oneside of the circuit with an electromagnet. When the current reached the magnet, the magnetwas activated. This would result in pulling a wire connected to the spring arm,this wouldpush the wire to connect with the circuit. This would cause the current flow to change to theopposite side of the circuit therefore stopping power from the electromagnet. When themagnet is free the mechanism snaps the wire back, which permits the current to flow on theopposite side of the circuit and again triggering the magnet. When these inverters were inoperation they a used to make a buzzing sound. Inverters have developed over time and the most up-to-date inverters use oscillator circuitsto achieve a similar procedure. Modern inverters don’t use an arm flicking back and forth toalternate the current, instead they use transistors and semi-conductors.Error! Referencesource not found.2.3 DC (Direct Current) and AC (Alternating Current)Electricity is generated in power plants, these power plants are often located in isolatedareas miles away from where the electricity is needed. When the electricity is sent to thepower lines a lot of power is lost due to heat and some of this turns to buzzing and crackingnoises. The greater the distance the power plant is located away from the intended locationthe greater push is needed and therefore greater power losses. The longer a cable is thegreater the resistance will be i.e. a greater push is needed to force the electricity to theintended location.9 To solve the resistance problem in transmission lines the generation station has two options.The first option is to force huge quantities of electricity over the power lines which will resultin massive losses and there will only be a dribble of electricity left to power your electricrazor. This method can be compared to spitting into a straw about 40 miles long withouttaking a breath. This is how difficult it is to move DC (Direct Current) over transmission lines.DC only travels in one direction.The second option to send large quantities of electricity over long distances is to “pulsecurrent”. Pulse current is when current is sent in powerful bursts that overcome resistance.Pulse current can be again compared with spitting threw a straw, you take a big spit take adeep breath and spit again. There is a lot of power behind each spit. In Ireland electricalgenerators only “spit” out the current 50 times a second i.e. 50 hertz. This is AC (AlternatingCurrent). This is why AC is the preferred method of transporting electricity over longdistances.Error! Reference source not found.2.4 The need for invertersThe DC to AC Inverter convert DC (direct current) to AC (alternating current). An inverterraises the DC voltage and then converts it to AC before powering a specific device. Inverterscan be run in reverse to achieve the opposite effect, that’s where they got their nameinverters. Most applications operate on AC therefore DC is always changed to AC. Howeverapplications such as laptops, TV’s, phones, computers operate in DC so the AC power inchanged back to DC power for use. For example in laptops the AC power is changed back toDC power by the small box attached to the power cable. The DC power generated by windturbines or solar panels is converted into AC power by the inverter so that it complies withthe national grid, and then converted back to DC to supply power to phones, laptops etc.Usually a house has a main central inverter that converts from DC to AC however in recentyears there has been a huge emphasis on renewable energy and many house ownersinstalled solar panels which required an additional solar inverter that works independentlyand directly under each solar panel. The invers take longer to install and are moreexpensive.Error! Reference source not found.In other energy systems inverts are the main stage between a battery’s DC power and theAC power required by domestic appliances. An inverter connected to a battery bank canensure that a grid connected house will have an uninterrupted power supply in the event of apower failure. An inverter also allows the home owner to sell excess electricity generated bysolar panels, wind turbine etc. back to the grid.10 "