100 W LOW COST INVERTER FOR 100
W LOW COST INVERTER FOR
SOLAR ENERGY CONVERSION
PROJECT INDEX: PRJ 027
BY:
KETTER RONALD KIPKOECH
SUPERVISOR: DR. MWANGI MBUTHIA
EXAMINER:
MR OGABA
MR.
Introduction
• An
An inverter is a device that takes a DC inverter is a device that takes a DC
(Direct Current) input and produces a AC (Alternating Current) output
(Alternating Current) output. • Th
The objective of the project was to bj ti
f th
j t
t
design and implement a low cost t
transformer‐less
f
l
i
inverter for solar energy t f
l
conversion.
Overview Design Topology
Overview Design Topology Switched Capacitor DC‐DC Converters
¾It is used to obtain a voltage higher than the ¾I
i
d
b i
l
hi h h
h
supply voltage or a voltage with reverse polarity.
polarity
¾ Accomplish voltage conversion using capacitors and semiconductor switches –
it
d
i d t
it h
Inductorless
¾Ad t
¾Advantages: 1. Do not require magnetic components
2. Simple, small, low cost
Switched Capacitor Push‐Pull
Switched Capacitor Push
Pull Design
Design
¾When one set of charge pump is ¾When
one set of charge pump is
being charged, the other is charging th
the output .
t t
¾ In this architecture, one of the pump capacitors is always delivering pump
capacitors is always delivering
charge to the output.
DC‐DC Converter Stage‐
g
Switched Capacitor Push‐Pull Design
Switched Capacitor Push‐Pull Design
p
g
¾With switches in phase A closed the equivalent circuit is as shown
equivalent circuit is as shown
¾All capacitors except the output capacitor across the load R are placed in parallel with
across the load R are placed in parallel with the input voltage source Vin
Switched Capacitor Push‐Pull
Switched Capacitor Push
Pull Design
Design
¾With switches in phase B closed the equivalent circuit is:
i l
i i i
¾The capacitors placed are in series with Vin deliver charge to the output
Vin, deliver charge to the output.
Inverter Stage ‐Full Bridge Design
g
g
g
¾Was implemented using N‐MOSFETs IRF740
3
Q2
Q1
PWM Signal 1
5
4
IRF740
IRF740
Vdc
Load
1
Q3
PWM Signal
Si
l2
PWM Signal
g
2
2
Q4
7
6
IRF740
IRF740
0
PWM Signal
Si
l1
Digital Control Circuit
Digital Control Circuit
• Atmel ATtiny26L microcontroller was used to obtain the control signals required in both b i h
l i l
i di b h
stages.
• A pair of anti‐phase 10 kHz square wave signal used to switch the MOSFETs in the Dc‐Dc converter stage was obtained from port B pin 6 and pin 7.
• Another pair of anti‐phase 50 Hz square wave signal used in H‐Bridge was obtained from g
g
port A pin 1 and pin 2.
Gate Drive Circuit
Gate Drive Circuit
¾The output of microcontroller is 2.3V. This cannot turn on MOSFET due to large stray capacitance
turn on MOSFET due to large stray capacitance.
¾A simple driver circuit was used as shown Simulated Results‐
Dc‐Dc Stage
Simulation of three modules, produced an output of 47.78V
output of 47.78V
Full Bridge Inverter Stage
Full Bridge Inverter Stage
A square wave of 47.12Vpk‐pk was obtained
Prototype
• A
A three module prototype was built and three module prototype was built and
tested on breadboard as shown
Prototype Results
Prototype Results
¾A voltage of 46. 8V was obtained from the Dc‐
D
Dc converter while the inverter output was a hil h i
45.6V.
¾ With the ideal expected voltage being 48V for this prototype. This results in efficiency greater than 95% Conclusion
• From
From the results obtained from both the the results obtained from both the
simulation and the prototype, the inverter can be easily scaled up since the DC‐DC
be easily scaled up since the DC
DC boost boost
stage is modular in structure.
• In addition, the proposed design has lower In addition the proposed design has lower
cost and high efficiency than the conventional transformer based inverters
transformer based inverters. Recommendation and Future Work
Recommendation and Future Work
A. In
In future the H
future the H‐Bridge
Bridge circuit can be circuit can be
eliminated and PWM techniques applied to the output of the switched capacitor boost converter using microcontroller to achieve sinusoidal output.
B. The MOSFETs used as switches in the DC‐DC boost converter stage can be eliminated by use of better switching techniques to reduce fb
i hi
h i
d
power losses.
Thank You