Download Sine Pulse Width Modulation (SPWM)

Sine Pulse Width
Modulation (SPWM)
Sine Pulse Width Modulation
(SPWM)
Introduction
 Sinusoidal PWM has been a very popular technique used in AC motor
control. This is a method that employs a triangular carrier wave
modulated by a sine wave and the points of intersection determine the
switching points of the power devices in the inverter.
 Though this method is unable to make full use of the inverter’s supply
voltage and the asymmetrical nature of the PWM switching
characteristics produces relatively high harmonic distortion in the supply
it is still popular for its simplicity.
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Sine Pulse Width Modulation
(SPWM)
Block Diagram
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Sine Pulse Width Modulation
(SPWM)
Hardware Requirements
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8051 series Microcontroller
MOSFET
Gate Driver
Crystal Oscillator
Toggle Switches
Resistors
Capacitors
Diodes
Transformer
Regulator
Opto-isolators
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Sine Pulse Width Modulation
(SPWM)
Software Requirements
 Keil compiler
 Languages: Embedded C or Assembly
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Sine Pulse Width Modulation
(SPWM)
Power Supply
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Sine Pulse Width Modulation
(SPWM)
Power Supply
 The 230V AC supply is first stepped down to 12V AC using a step
down transformer.
 This is then converted to DC using bridge rectifier.
 The AC ripples is filtered out by using a capacitor and given to the
input pin of voltage regulator 7805.
 At output pin of this regulator we get a constant 5V DC which is used
for MC and other ICs in this project.
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Sine Pulse Width Modulation
(SPWM)
Microcontroller
 It is a smaller computer
 Has on-chip RAM, ROM, I/O ports.
CPU
I/O
Port
RAM ROM
Serial
Timer COM
Port
A single chip
Microcontroller
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Sine Pulse Width Modulation
(SPWM)
Features of Micro Controller
 8K Bytes of In-System Programmable (ISP) Flash Memory
 4.0V to 5.5V Operating Range
 Fully Static Operation: 0 Hz to 33 MHz
 256 x 8-bit Internal RAM
 32 Programmable I/O Lines
 Three 16-bit Timer/Counters
 Eight Interrupt Sources
 Full Duplex UART Serial Channel
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Sine Pulse Width Modulation
(SPWM)
Microcontroller Pin Description
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Sine Pulse Width Modulation
(SPWM)
Power On Reset Circuit
+
10
uF
8.2
K
31
30
pF
30
pF
11.0592
MHz
EA/V
X1
19 PP
18
X2
9 RST
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Sine Pulse Width Modulation
(SPWM)
Opto-Isolator
 Opto coupler is a 6 pin IC. It is a combination of 1 LED and a transistor.
 Pin 6 of transistor is not generally used and when light falls on the BaseEmitter junction then it switches and pin5 goes to zero.
 If input of the diode is zero and other end of diode is GND then the output is
one.
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Sine Pulse Width Modulation
(SPWM)
Opto-Isolator
 When logic zero is given as input then the light doesn’t fall on transistor
so it doesn’t conduct which gives logic zero as output.
 When logic 1 is given as input then light falls on transistor so that it
conducts, that makes transistor switched ON and it forms short circuit
this makes the output is logic zero as collector of transistor is
connected to ground.
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Sine Pulse Width Modulation
(SPWM)
MOSFET
 The MOSFET (Metal Oxide Semiconductor Field
Effect Transistor) is a Voltage controlled device.
 This means that a voltage at the gate control the
current flows from the drain to the source.
 There are three terminals: Gate - connected to the
input device.
 Drain - connected to the positive, since electrons
drain away to the positive. Source - the source of
the electrons.
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Sine Pulse Width Modulation
(SPWM)
MOSFET
 USES OF MOSFETS High power devices like motors and light bulbs give a
large current output for a very tiny current input.
 So a MOSFET can act as the interface between an integrated circuit that can
give only a tiny current, and the motor that takes a big current.
 In complimentary pairs they are used in hi-fi power amplifiers.
 They produce less distortion as they are more linear than bipolar transistors.
 Integrated circuits, as they can be made very compact.
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Sine Pulse Width Modulation
(SPWM)
IR2101 Features
 Floating channel designed for bootstrap operation Fully operational to
+600V Tolerant to negative transient voltage dV/dt immune.
 Gate drive supply range from 10 to 20V.
 Undervoltage lockout.
 3.3V, 5V, and 15V logic input compatible.
 Matched propagation delay for both channels.
 Outputs in phase with inputs (IR2101) or out of phase with inputs (IR2102)
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Sine Pulse Width Modulation
(SPWM)
IR2101 Description
 The IR2101(S)/IR2102(S) are high voltage, high speed power MOSFET and
IGBT drivers with independent high and low side referenced output
channels.
 Proprietary HVIC and latch immune CMOS technologies enable ruggedized
monolithic construction.
 The logic input is compatible with standard CMOS or LSTTL output, down to
3.3V logic.
 The output drivers feature a high pulse current buffer stage designed for
minimum driver cross-conduction.
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Sine Pulse Width Modulation
(SPWM)
Working
 A star lamp load can be used to view the waveform only. This project uses
an 8051 family microcontroller duly interfaced to the Opto-isolators for
feeding to the bridge drivers. 3 no’s of dual bridge drivers are used to feed
3 phase bridge inverter with the DC supply developed from single phase
AC after rectification.
 Powering the circuit is achieved by a pair of control transformers with
bridge rectifier and filter capacitors. One set of this power is used for the
microcontroller and the other one is used for driving circuits of the three
phase bridge.
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Sine Pulse Width Modulation
(SPWM)
The working principle of SPWM includes the following points
 The frequency of triangular wave is the frequency of PWM.
 Frequency of control voltage controls the fundamental frequency.
 The peak value of control voltage controls the amplitude.
 Modulation Index is defined by:

 Where Vao1 = Fundamental component of Vao.
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Sine Pulse Width Modulation
(SPWM)
The working principle of SPWM includes the following points
For Phase A:
 If Vcontrol > Vtriangle then Vao = Vd/2.
 If Vcontrol < Vtriangle then Vao = -Vd/2.
For Phase B:
 If Vcontrol > Vtriangle then Vbo = Vd/2.
 If Vcontrol < Vtriangle then Vbo = -Vd/2.
For Phase C:
 If Vcontrol > Vtriangle then Vco = Vd/2.
 If Vcontrol < Vtriangle then Vco = -Vd/2.
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Sine Pulse Width Modulation
(SPWM)
Advantage
 The main advantage of PWM is that power loss in the switching
devices is very low.
 When a switch is off there is practically no current, and when it is on,
there is almost no voltage drop across the switch.
 Power loss, being the product of voltage and current, is thus in both
cases close to zero.
 PWM also works well with digital controls, which, because of their
on/off nature, can easily set the needed duty cycle.
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Sine Pulse Width Modulation
(SPWM)
Applications
 In many industrial applications, Sinusoidal Pulse Width
Modulation (SPWM), is used to control the inverter output
voltage.
 SPWM maintains good performance of the drive in the entire
range of operation between zero and 78 percent of the value
that would be reached by square-wave operation.
 If the modulation index exceeds this value, linear relationship
between modulation index and output voltage is not
maintained and the over-modulation methods are required.
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Sine Pulse Width Modulation
(SPWM)
Conclusion
 For the generation of pure sinusoidal signal, SPWM is the most popular
technique. In SPWM a digital waveform is generated and the duty cycle
is modulated such that the average voltage of the waveform is
corresponds to a pure sine wave. SPWM moves the voltage harmonic
components to the higher frequencies. The SPWM technique treats
each modulating voltage as a separate signal and compared to the
common carrier triangular waveform.
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