THREE PHASE INVERTER USING ARDUINO Project report submitted in partial fulfillment of the requirements for the award of the degree of BACHELOR OF TECHNOLOGY IN ELECTRICAL AND ELECTRONICS ENGINEERING
A. SIVA SAI
09241A02A3
A. SRI RAM
10241A0205
M. VENKATESH
10241A0232
P. RAM SREEDHAR
10241A0244
Under the guidance of G. SWAPNA (Assistant Professor)
Department of Electrical and Electronics Engineering GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING & TECHNOLOGY, BACHUPALLY, HYDERABAD-72, 2014 1
GOKARAJU RANGARAJU INSTITUTE OF ENGINEERING AND TECHNOLOGY Hyderabad, Andhra Pradesh. DEPARTMENT OF ELECTRICAL & ELECTRONICS ENGINEERING
CERTIFICATE: This is to certify that the project report entitled “ THREE PHASE INVERTER USING ARDUINO” that is being submitted by A. SIVA SAI, A. SRI RAM, M. VENKATESH, P. RAM SREEDHAR in partial fulfillment for the award of the Degree of Bachelor of Technology in Electrical and Electronics Engineering to the Jawaharlal Nehru Technological University is a record of bonafide work carried out by him under my guidance and supervision. The results embodied in this project report have not been submitted to any other University or Institute for the award of any graduation degree.
Prof. M. Chakravarthy HOD, EEE GRIET, Hyderabad
G. Swapna ASSISTANT PROFFESSOR
GRIET, Hyderabad (GUIDE) 2
Acknowledgement This is to place on record my appreciation and deep gratitude to the persons without whose support this project would never seen the light of day. I have immense pleasure in expressing my thanks and deep sense of gratitude to my guide G. Swapna, Assistant Professor G.R.I.E.T for her guidance throughout this project. I also express my sincere thanks to Prof. P.M. Sarma, Research and Development Dean for extending his help. I express my gratitude to Prof. E.Venkateshwaralu, Project Supervisor G.R.I.E.T for his valuable recommendations and for accepting this project report. Finally I express my sincere gratitude to all the members of faculty and my friends who contributed their valuable advice and helped to complete the project successfully.
A. SIVA SAI A. SRI RAM M. VENKATESH P. RAM SREEDHAR
3
Table of Contents
Abstract
List of figures
Page No
Chapter I : Introduction………………………………………….…..8
Chapter II : Background ……………………………………….….9 2.1: Pulse Width Modulation Control ……………………..9 2.2: Unipolar and bipolar modulation ……………………..10 2.3: Three phase inverters ……………………………........11 Chapter III : Methodology…………………………………………..14 3.1: Three phase inverters (180° conduction)…………........14 3.2: Filter circuits configurations…………………………...16
Chapter IV : Arduino Mega…………………………………………18 4.1: overview………………………………………….........18 4.2: Summary………………………………………….........20
Chapter V: Interfacing of PS21765………………………………....26 5.1: Interfacing………………………………………………27 5.2 : 15V Power supply(Vcc)…………………………...........31
4
5.3 : Three phase bridge rectifier…………………………...31 5.4 : Applications…………………………………………...33
Chapter VI: Results and Output……………………………….........34 6.1: Simulation results………………………………….........34 6.2: Conclusions……………………………………………..38 6.3: References………………………………………………38
5
ABSTRACT This project deals with study of a Sinusoidal Pulse Width Modulated Inverter and all the parameters used to reduce the harmonics and give the good efficiency of the inverter. The project will be commenced by a basic understanding of the circuitry of the SPWM Inverter using arduino, the components used in its design and the reason for choosing such components in this circuitry. Generally, only single phase SPWM inverters are used industrially, and certain instabilities have been found in their operation. With improper selection of system parameters, the inverter suffers different type of instabilities and many types of harmonics. Our attempt will be to observe the same for three phase SPWM inverter and analyze its parameters used to get a pure sinusoidal output waveform and fewer harmonic in its output current and voltage waveform. Three phase inverters are essential in many industrial applications for providing adjustable-frequency power. Arduino is an open source electronic prototyping platform based on flexible easy to use hardware and software. It is intended for artists, designers, hobbyists and anyone interested in creating interactive objects or environments. The effectiveness of using arduino is that it will directly generates the required pulses for switching the full bridge inverter effectively
6
List of Figures
Page No
Fig 1. Unipolar and Bipolar modulation…………………………………………...11
Fig 2. Basic Circuitry of a three phase inverter…………………………………....12 Fig 3. Pulses of 180-degree conduction…………………………………………..15
Fig 4. Output voltage in 180-degree conduction…………………………………16
Fig 5. L filter topology…………………………………………………………….16 Fig 6. L-C filter topology………………………………………………………….17 Fig 7. Arduino Mega………………………………………………………………19 Fig 8. Application Circuit of PS21765……………………………………………26 Fig 9. PS21765……………………………………………………………….…..30 Fig 10. Connection Diagram……………………………………………………...32 Fig 11. PWM signals from pin 8-13………………………………………………34-37 Fig 12. Output Voltage Waveforms……………………………………………….37
7
CHAPTER I Introduction What if we cannot use the stored power in a battery when we don’t have power supply? Since the energy stored in a battery is in dc form so to use this stored power in battery we need to convert this dc form of energy to ac form. So here comes the concept of power inverters. The devices which can convert electrical energy of DC form into AC form is known as power inverters. They come in all sizes and shapes, from a high power rating to a very low power rating, from low power functions like powering a car radio to that of backing up a building in case of power outage. Inverters can come in many different varieties, differing in power, efficiency, price and purpose. The purpose of a DC/AC power inverter is typically to take DC power supplied by a battery, such as a 12 volt car battery, and transform it into a 120 volt AC power source operating at 60 Hz, emulating the power available at an ordinary household electrical outlet. DC-AC inverters have been widely used in industrial applications such as uninterruptible power supplies, static frequency changes and AC motor drives. Recently, the inverters are also playing important roles in renewable energy applications as they are used to link a photovoltaic or wind system to a power grid. Like DC-DC converters, the DC-AC inverters usually operate in a pulse width modulated (PWM) way and switch between a few different circuit topologies, which means that the inverter is a nonlinear, specifically piecewise smooth system. In addition, the control strategies used in the inverters are also similar to those in DC-DC converters. For instance, current-mode control and voltage-mode control are usually employed in practical applications. In the last decade, studies of complex behavior in switching power converters have gained increasingly more attention from both the academic community and industry.
8
CHAPTER II Background Devices that convert dc power to ac power are called inverters. The purpose of an inverter is to change a dc input voltage to ac output voltage which will be symmetric and will have desired magnitude and frequency. The output voltage can be varied by varying the input dc voltage and keeping constant inverter gain, however, if the input dc voltage is fixed and cannot be controlled, the gain of the inverter has to be varied to obtain variable output voltage. Varying the gain of the inverter is mainly done by a scheme which is known as Pulse Width Modulation (PWM). The inverter gain is basically the ratio of ac output voltage to the dc input voltage. Based on the power supply, inverters can be broadly classified into two types: Voltage Source Inverter and Current Source Inverter. A VSI has small or negligible impedance at its input terminal that is, it has a stiff dc voltage source, whereas for a CSI, it is fed with adjustable current from a dc source with high impedance in this case. For the purpose of our project, all analysis throughout this paper has been done for Voltage Source Inverters (VSI). These can be classified into two types which are Single Phase Inverters and Three Phase Inverters. Either type can use controllable turn-on and turn-off devices e.g. BJTs, MOSFETs, IGBTs etc. Generally PWM control is used to obtain ac output voltage of desired frequency and magnitude.
2.1 Pulse Width Modulation control This is a method in which fixed dc input voltage is given to an inverter and the output is a controlled ac voltage. This is done by adjusting the on and off periods of the inverter components. The advantages of PWM control are: 1. No additional components are required with this method. 2. Lower order harmonics are eliminated or minimized along with its output voltage control. Hence, the filtering requirements are minimized since higher order harmonics can be filtered easily.
9
Different schemes of pulse-width modulation: 1. Single-pulse modulation 2. Multi-pulse modulation 3. Sinusoidal-pulse modulation
Since our project deals with Sinusoidal Pulse Width modulated Inverters, the basic concepts of Sinusoidal PWM are explained below. In this method of modulation, several pulses per half cycle are used and the pulse width is a sinusoidal function of the angular position of the pulse in a cycle. A high frequency triangular carrier wave Vc is compared with a sinusoidal reference wave Vr of the desired frequency. The switching instants and commutation of the modulated pulse are determined by the intersection of Vc and Vr waves. The carrier and reference waves are mixed in a comparator. When the sinusoidal wave has higher magnitude, the comparator output is high, else it is low. The comparator output is processed in a trigger pulse generator in such a way that the output voltage wave has a pulse width in agreement with the comparator pulse width.
2.2 Uni polar and bipolar modulation: If the half-cycle sine wave modulation, the triangular carrier only in a positive or negative polarity range of changes, the resulting SPWM wave only in a polar Range, called unipolar control mode. If the half-cycle sine wave modulation, triangular carrier in continuous change between positive and negative polarity, the SPWM wave is between positive and negative changes, known as bipolar control. Unipolar and bipolar modulations are shown in Figure.
10
Fig 1: Unipolar and bipolar modulation
2.3 Three Phase Inverters: Three phase inverters are generally used for high power applications. Three single phase half bridge inverters are to be connected in parallel to form a three phase inverter. The inverter is fed by a fixed dc voltage and has three phase-legs each comprising two transistors and two diodes. With SPWM control, the controllable switches of the inverter are controlled by comparison of a sinusoidal control signal and a triangular switching signal. The sinusoidal control waveform determines the desired fundamental frequency of the inverter output, while the triangular waveform decides the switching frequency of the inverter. The ratio of the frequencies of the triangle wave to the sinusoid is referred to as the modulation frequency ratio.
11
Fig 2: Basic Circuitry of a three phase inverter
12
The switches of the phase legs are controlled based on the following comparison:
V control (phase a) > V triangle, Ta+ is on V control (phase a) < V triangle, Ta- is on V control (phase b) > V triangle, Tb+ is on V control (phase b) < V triangle, Tb- is on V control (phase c) > V triangle, Tc+ is on V control (phase c) < V triangle, Tc- is on
The gating signals of single phase inverters should be advanced or delayed by 120° with respect to each other to get 3 phase balanced voltages. The transformer primary winding must be isolated from each other whereas secondary winding may be connected in wither Y or Δ. The secondary winding of the transformer is usually connected in Δ to get rid of triple harmonic appearing on the output voltages. Output voltages of single phase inverters are not balanced in magnitude or phase. A three phase output may also be obtained by a configuration of six controllable switches and six diodes. Two types of control signals can be applied to these switches which are 120° and 180° modes of conduction.
13
CHAPTER III Methodology 3.1 180° mode of operation: Each transistor conducts for a period of 180°. Three of the transistors remain on at any instant of time. When Ta+ is switched on, terminal a is connected to positive terminal of dc input voltage. When Ta- is switched on, terminal a is brought to negative terminal of dc input. There are six modes of operation in a cycle and duration of each mode is 60°. T
State
State No.
Vab
Vbc
Vca
Ta+, Tc- and l Tb- are on
1
VDC
0
- VDC
Tc-, Tb+ and
2
0
VDC
- VDC
a b
e
T + are on 1 a
3
- VDC
VDC
0
4
-VDC
0
VDC
5
0
-VDC
VDC
6
VDC
-VDC
0
s T + , T + and a b t Tc+ are on
7
0
0
0
a Ta-, Tb- and
8
0
0
0
: Tb+, Ta- and
Tc- are on STa-, Tc+ and wTb+ are i
on
t Tc+, Tb- and c Ta- are on h Tb-, Ta+ and
Tc+ are on
t T - are on c Three phase voltage source inverter (VSI) for 180 degree conduction 14
The load can be connected in either Y or Δ. Switches of any leg of the inverter cannot be switched on at the same time since this would result in a short circuit across the dc link voltage supply. Similarly to avoid undefined states and thus undefined ac output line voltage, the switches of any leg of the inverter may not be switched off simultaneously since this can result in voltages that depend on respective line current polarity. However, for practical applications, 180° mode of conduction is preferred since each transistor is better utilized in case of 180° mode of conduction as compared to 120° mode of operation for similar load conditions. Nevertheless, the analysis of the output waveforms of the inverter will not vary much for 120° since only the amplitude will vary for the two modes and not the vital characteristics. This conductive angle is used in many industries. It results in six modes for each period, considering the number of transistors, which each of them is on for a half a period.T1, T5 andT6 transistors turn on in first half time and other transistors are off. AC voltage is produce, by repeating the same process in the next modes. Figure. 2 shows pulses and output voltage for an ohmic load.
Fig 3. Pulses of 180-degree conduction
15
Fig 4. Output voltage in 180-degree conduction
3.2: Filter circuits configurations: The three main existing harmonic filter topologies for three-phase inverters follow.
L-Filter — First order: Attenuation of the basic inductor filter shown in Figure 7 is –20 dB/decade over the whole frequency range. Using this filter, the inverter switching frequency has to be high in order to sufficiently attenuate the inverter harmonics.
Fig 5: L filter topology 16
LC–Filter — Second order: The LC-filter in Figure 8 is a second order filter Giving –40 dB/decade attenuation. Since the previous L-filter achieves low attenuation of the inverter switching components, a shunt element is needed to further attenuate the switching frequency components. This shunt component must be selected to produce low reactance at the switching frequency. But within the control frequency range, this element must present a high magnitude impedance. A Capacitor is used as the shunt element. The resonant frequency is calculated from. The resonant frequency is calculated from the following equation. f= 1/2π√LC The LC-filter in Figure 9 has been investigated in UPS systems with a resistive load. This LC-filter is suited to configurations where the load impedance across C is relatively high at and above the switching frequency. The cost and the reactive power consumption of the LC-filter are more than to the L-filter because of the addition of the shunt element.
Fig 6: L-C filter topology The limitation of the LC filter is that the shunt element is ineffective when connected to a stiff grid network, where the grid impedance is insignificant at the switching frequency. The output current ripple is the same as the inductor current ripple with an L-filter, where the attenuation depends solely on the filter inductance. 17
CHAPTER IV Arduino Mega 4.1 Overview: The
Arduino
Mega
2560
is
a
microcontroller
board
based
on
the ATmega2560 (datasheet). It has 54 digital input/output pins (of which 15 can be used as PWM outputs), 16 analog inputs, 4 UARTs (hardware serial ports), a 16 MHz crystal oscillator, a USB connection, a power jack, an ICSP header, and a reset button. It contains everything needed to support the microcontroller; simply connect it to a computer with a USB cable or power it with a AC-to-DC adapter or battery to get started. The Mega is compatible with most shields designed for the Arduino Duemilanove or Diecimila. The Mega 2560 is an update to the Arduino Mega, and it has following features: Stronger RESET circuit Atmega 16U2 replace the 8U2 Schematic, Reference Design & Pin Mapping. EAGLE files : arduino-mega2560_R3-reference-design.zip. Schematic
: arduino-mega2560_R3-schematic.pdf.
Pin Mapping : PinMap2560 page.
18
Fig 7 : Arduino Mega
Pinout: added SDA and SCL pins that are near to the AREF pin and two other new pins placed near to the RESET pin, the IOREF that allow the shields to adapt to the voltage provided from the board.In future, shields will be compatible both with the board that use the AVR, which operate with 5V and with the Arduino Mega that operate with 3.3V. The second one is a not connected pin, that is reserved for future purposes.
19
4.2 Summary:
Microcontroller
ATmega2560
Operating Voltage
:
5V
Input Voltage (recommended)
:
7-12V
Input Voltage (limits)
:
6-20V
Digital I/O Pins
:
54 (of which 15 provide PWM o/p)
Analog Input Pins
:
16
DC Current per I/O Pin
:
40 mA
DC Current for 3.3V Pin
:
50 mA
Flash Memory
:
256 KB of which 8 KB used by bootloader
SRAM
:
8 KB
EEPROM
:
4 KB
Clock Speed
:
16 MHz
20
4.3 Power: The Arduino Mega can be powered via the USB connection or with an external power supply. The power source is selected automatically. External (non-USB) power can come either from an AC-to-DC adapter (wall-wart) or battery. The adapter can be connected by plugging a 2.1mm center-positive plug into the board's power jack. Leads from a battery can be inserted in the Gnd and Vin pin headers of the POWER connector. The board can operate on an external supply of 6 to 20 volts. If supplied with less than 7V, however, the 5V pin may supply less than five volts and the board may be unstable. If using more than 12V, the voltage regulator may overheat and damage the board. The recommended range is 7 to 12 volts. The power pins are as follows:
VIN. The input voltage to the Arduino board when it's using an external power source (as opposed to 5 volts from the USB connection or other regulated power source). You can supply voltage through this pin, or, if supplying voltage via the power jack, access it through this pin.
5V. This pin outputs a regulated 5V from the regulator on the board. The board can be supplied with power either from the DC power jack (7 - 12V), the USB connector (5V), or the VIN pin of the board (7-12V). Supplying voltage via the 5V or 3.3V pins bypasses the regulator, and can damage your board. We don't advise it.
3V3. A 3.3 volt supply generated by the on-board regulator. Maximum current draw is 50 mA.
GND. Ground pins.
4.4 Memory: The ATmega2560 has 256 KB of flash memory for storing code (of which 8 KB is used for the bootloader), 8 KB of SRAM and 4 KB of EEPROM (which can be read and written with the EEPROM library).
21
4.5 Input and Output: Each of the 54 digital pins on the Mega can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 5 volts. Each pin can provide or receive a maximum of 40 mA and has an internal pull-up resistor (disconnected by default) of 20-50 kOhms. In addition, some pins have specialized functions: Serial: 0 (RX) and 1 (TX); Serial 1: 19 (RX) and 18 (TX); Serial 2: 17 (RX) and 16 (TX); Serial 3: 15 (RX) and 14 (TX). Used to receive (RX) and transmit (TX) TTL serial data. Pins 0 and 1 are also connected to the corresponding pins of the ATmega16U2 USB-to-TTL Serial chip. External Interrupts: 2 (interrupt 0), 3 (interrupt 1), 18 (interrupt 5), 19 (interrupt 4), 20 (interrupt 3), and 21 (interrupt 2). These pins can be configured to trigger an interrupt on a low value, a rising or falling edge, or a change in value. See the attachInterrupt() function for details. PWM: 2 to 13 and 44 to 46. Provide 8-bit PWM output with the analogWrite() function. SPI: 50 (MISO), 51 (MOSI), 52 (SCK), 53 (SS). These pins support SPI communication using the SPI library. The SPI pins are also broken out on the ICSP header, which is physically compatible with the Uno, Duemilanove and Diecimila. LED: 13 There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off. TWI: 20 (SDA) and 21 (SCL). Support TWI communication using the Wire library. Note that these pins are not in the same location as the TWI pins on the Duemilanove or Diecimila. The Mega2560 has 16 analog inputs, each of which provide 10 bits of resolution (i.e. 1024 different values). By default they measure from ground to 5 volts, though is it possible to change the upper end of their range using the AREF pin and analogReference() function. There are a couple of other pins on the board: 22
AREF : Reference voltage for the analog inputs. Used with analogReference(). Reset : Bring this line LOW to reset the microcontroller. Typically used to add a reset button to shields which block the one on the board.
4.6 Communication: The Arduino Mega2560 has a number of facilities for communicating with a computer, another Arduino, or other microcontrollers. The ATmega2560 provides four hardware UARTs for TTL (5V) serial communication. An ATmega16U2 (ATmega 8U2 on the revision 1 and revision 2 boards) on the board channels one of these over USB and provides a virtual com port to software on the computer (Windows machines will need a .inf file, but OSX and Linux machines will recognize the board as a COM port automatically. The Arduino software includes a serial monitor which allows simple textual data to be sent to and from the board. The RX and TX LEDs on the board will flash when data is being transmitted via the ATmega8U2/ATmega16U2 chip and USB connection to the computer (but not for serial communication on pins 0 and 1). A SoftwareSerial library allows for serial communication on any of the Mega2560's digital pins. The ATmega2560 also supports TWI and SPI communication. The Arduino software includes a Wire library to simplify use of the TWI bus; see the documentation for details. For SPI communication, use the SPI library.
4.7 Programming: The Arduino Mega can be programmed with the Arduino software (download). For details, see the reference and tutorials. The ATmega2560 on the Arduino Mega comes preburned with a bootloader that allows you to upload new code to it without the use of an external hardware programmer. It communicates using the original STK500 protocol (reference, C header files). You can also bypass the bootloader and program the microcontroller through the ICSP (In-Circuit Serial Programming) header; see these instructions for details. 23
The ATmega16U2 (or 8U2 in the rev1 and rev2 boards) firmware source code is available in the Arduino repository. The ATmega16U2/8U2 is loaded with a DFU bootloader, which can be activated by: On Rev1 boards: connecting the solder jumper on the back of the board (near the map of Italy) and then resetting the 8U2. On Rev2 or later boards: there is a resistor that pulling the 8U2/16U2 HWB line to ground, making it easier to put into DFU mode. You can then use Atmel's FLIP software (Windows) or the DFU programmer (Mac OS X and Linux) to load a new firmware. Or you can use the ISP header with an external programmer (overwriting the DFU bootloader). See this user-contributed tutorial for more information.
4.8 Automatic (Software) Reset: Rather then requiring a physical press of the reset button before an upload, the Arduino Mega2560 is designed in a way that allows it to be reset by software running on a connected computer. One of the hardware flow control lines (DTR) of the ATmega8U2 is connected to the reset line of the ATmega2560 via a 100 nanofarad capacitor. When this line is asserted (taken low), the reset line drops long enough to reset the chip. The Arduino software uses this capability to allow you to upload code by simply pressing the upload button in the Arduino environment. This means that the bootloader can have a shorter timeout, as the lowering of DTR can be wellcoordinated with the start of the upload. This setup has other implications. When the Mega2560 is connected to either a computer running Mac OS X or Linux, it resets each time a connection is made to it from software (via USB). For the following half-second or so, the bootloader is running on the Mega2560. While it is programmed to ignore malformed data (i.e. anything besides an upload of new code), it will intercept the first few bytes of data sent to the board after a connection is opened. If a sketch running on the board receives one-time configuration or other data when it first starts, make sure that the software with which it communicates waits a second after opening the connection and before sending this data. The Mega2560 contains a trace that can be cut to disable the auto-reset. The pads on either side of the trace can be soldered together to re-enable it. It's labeled "RESET24
EN". You may also be able to disable the auto-reset by connecting a 110 ohm resistor from 5V to the reset line; see this forum thread for details.
25
CHAPTER V INTERFACING OF PS21765 PS21765 is a 600V, 20 Ampere short pin DIP Intelligent Power Module.
Fig 8 : Application Circuit of PS21765 1) Input drive is active-high type. There is a 2.5k(min.) pull-down resistor integrated in the IC input circuit. To prevent malfunction, the wiring of each input should be as short as possible. When using RC coupling circuit, make sure the input signal level meets the turn-on and turn-off threshold voltage. See application notes for details. 2) Internal HVIC provides high voltage level shifting allowing direct connection of all six driving signals to the controller.
26
3) FO output is an open collector type. Pull up resistor (R3) should be adjusted to current sink capability of the controller. 4) To prevent input signal oscillations, minimize wire length to controller (~2cm). Additional RC filtering (C5 etc.) may be required. If filtering is added be careful to maintain proper dead time and voltage levels. See application notes for details. 5) All capacitors should be mounted as close to the terminals as possible. (C1: good temperature, frequency characteristic electrolytic type, and C2, C3: good temperature, frequency and DC bias characteristic ceramic type are recommended.) 6) Shows short circuit protection disabled. See application notes for use of short circuit protection. 7) Local decoupling frequency filter capacitors must be connected as close as possible to the module’s pins. 8) The length of the DC link wiring between C5, C6, the DIP’s P terminal and the shunt must be minimized to prevent excessive transient voltages. In particular C6 should be mounted as close to the DIP as possible. 9) Use high quality, tight tolerance current sensing resistor. Connect resistor as close as possible to the DIP’s N terminal. Be careful to check for proper power rating. See application notes for calculation of resistance value. 10) Inserting a Zener diode (24V/1W) between each pair of control supply terminals to prevent surge destruction is recommended.
5.1: Interfacing: The PWM pulses required for the switching mode of the inverter are generated using arduino software program illustrated below:
Program: #include GraphSeries pin8 = GraphSeries("Pin 8"); GraphSeries pin9 = GraphSeries("Pin 9"); GraphSeries pin10 = GraphSeries("Pin 10"); GraphSeries pin11 = GraphSeries("Pin 11"); GraphSeries pin12 = GraphSeries("Pin 12");
27
GraphSeries pin13 = GraphSeries("Pin 13"); GraphSeries input= GraphSeries("input voltage");
void setup() { pinMode(8,OUTPUT); pinMode(9,OUTPUT); pinMode(10,OUTPUT); pinMode(11,OUTPUT); pinMode(12,OUTPUT); pinMode(13,OUTPUT); Serial.begin(9600); }
void loop() { double d = 3.333; // 180 degree conduction mode - s1:0-180,s2:60-240,s3:120-300,s4:180-360,s5:24060,s6:300-120 digitalWrite(8,HIGH); delay(d); pin8.SendData(2); digitalWrite(12,LOW); digitalWrite(9,HIGH); 28
delay(d); pin9.SendData(3); digitalWrite(13,LOW); digitalWrite(10,HIGH); delay(d); pin10.SendData(4); digitalWrite(8,LOW); digitalWrite(11,HIGH); delay(d); pin11.SendData(5); digitalWrite(9,LOW); digitalWrite(12,HIGH); delay(d); pin12.SendData(6); digitalWrite(10,LOW); digitalWrite(13,HIGH); delay(d); pin13.SendData(7); digitalWrite(11,LOW); } The above program generates the gate pulses in which each switch conducts for a period of 60 degrees following 180 degree conduction mode. This inverter kit is designed in our college and it consists of the following circuits which are mounted on it. 29
Fig 9. PS21765
30
5.2: 15V POWER SUPPLY (Vcc): The 15v DC level required for PS21765 is taken from a rectifier circuit using voltage regulator LM7815.
5.3: THREE PHASE DIODE BRIDGE RECTIFIER: The DC input to the inverter is taken from a three phase diode bridge rectifier comprising of 6 power diodes connected in full bride rectifier mode.
31
Fig 9 : Connection Diagram
32
ARDUINO PINS
PS 21765 PINS
8
S1
9
S2
10
S3
11
S4
12
S5
13
S6
GND
GND
3.3V
3.3V
Table 2 : Connections of Arduino to PS21765 The interconnections between the arduino mega and the PS21765 were connected as illustrated above.
5.4: APPLICATIONS:
Refrigerators
Air Conditioners
Small Servo Motors
Small Motor Control
Solar panels
33
CHAPTER VI RESULTS AND OUTPUT Input of 26V is taken from the diode bridge rectifier and is applied to the inverter, the following results were obtained during simulation process.
6.1: Simulation result
PWM Signal going to pin 8:
34
PWM Signal going to pin 9:
PWM Signal going to pin 10:
35
PWM Signal going to pin 11:
PWM Signal going to pin 12:
36
PWM Signal going to pin 13:
OUTPUT:
Output Voltage R-Phase
37
Output VoltageY-Phase
38
Output Voltage B-Phase
39
6.2: Conclusions: Pulse width modulated (PWM) inverters, can provide higher quality of output voltage. The PWM inverter may be a preferred choice on account of its simplicity and low cost. The switch control circuit is very simple and the switching frequency is significantly lower. This results in low switching losses.
6.3: References: 1. Bhimbra P.S., “Power Electronics”, Khanna Publishers, 4th edition 2. Chattopadhyay and Rakshit P.C., “Electronics, Fundamentals and Applications”, New Age International P Limited, Publishers, 2007 3. Arduino Mega Reference – “arduino.cc”. 4. PS21765 Application note.
40
