PROJECT #1 SINE-∆ PWM INVERTER
JIN-WOO JUNG, PH.D STUDENT
E-mail: [email protected]
Tel.: (614) 292-3633
ADVISOR: PROF. ALI KEYHANI
DATE: FEBRUARY 20, 2005
MECHATRONIC SYSTEMS LABORATORY
D
EPARTMENT OF ELECTRICAL AND COMPUTER ENGINEERING
THE OHIO STATE UNIVERSITY
2
1. Problem Description
In this simulation, we will study Sine-∆ Pulse Width Modulation (PWM) technique. We will
use the SEMIKRON® IGBT Flexible Power Converter for this purpose. The system
configuration is given below:
Fig. 1 Circuit model of three-phase PWM inverter with a center-taped grounded DC bus.
The system parameters for this converter are as follows:
IGBTs: SEMIKRON SKM 50 GB 123D, Max ratings: V
CES
= 600 V, I
C
= 80 A
DC- link voltage: V
dc
= 400 V
Fundamental frequency: f = 60 Hz
PWM (carrier) frequency: f
z
= 3 kHz
Modulation index: m = 0.8
Output filter: L
f
= 800 µH and C
f
= 400 µF
Load: L
load
= 2 mH and R
load
= 5 Ω
Using Matlab/Simulink, simulate the circuit model described in Fig. 1 and plot the
waveforms of V
i
(= [V
iAB
V
iBC
V
iCA
]), I
i
(= [i
iA
i
iB
i
iC
]), V
L
(= [V
LAB
V
LBC
V
LCA
]), and I
L
(= [i
LA
i
LB
i
LC
]).
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2. Sine-∆ PWM
2.1 Principle of Pulse Width Modulation (PWM)
Fig. 2 shows circuit model of a single-phase inverter with a center-taped grounded DC bus,
and Fig 3 illustrates principle of pulse width modulation.
Fig. 2 Circuit model of a single-phase inverter.
Fig. 3 Pulse width modulation.
As depicted in Fig. 3, the inverter output voltage is determined in the following:
When V
control
> V
tri
, V
A0
= V
dc
/2
When V
control
< V
tri
, V
A0
= −V
dc
/2
4
Also, the inverter output voltage has the following features:
PWM frequency is the same as the frequency of V
tri
Amplitude is controlled by the peak value of V
control
Fundamental frequency is controlled by the frequency of V
control
Modulation index (m) is defined as:
A01A0
10
Vofcomponentfrequecnylfundamenta:)(Vwhere,
,
2/
)(
dc
A
tri
control
V
Vofpeak
v
v
m ==
∴
2.2 Three-Phase Sine-∆ PWM Inverter
Fig. 4 shows circuit model of three-phase PWM inverter and Fig. 5 shows waveforms of
carrier wave signal (V
tri
) and control signal (V
control
), inverter output line to neutral voltage (V
A0
,
V
B0
, V
C0
), inverter output line to line voltages (V
AB
, V
BC
, V
CA
), respectively.
Fig. 4 Three-phase PWM Inverter.
5
Fig. 5 Waveforms of three-phase sine-∆ PWM inverter.
As described in Fig. 5, the frequency of V
tri
and V
control
is:
Frequency of V
tri
= f
s
Frequency of V
control
= f1
where, f
s
= PWM frequency and f
1
= Fundamental frequency
The inverter output voltages are determined as follows:
When V
control
> V
tri
, V
A0
= V
dc
/2
When V
control
< V
tri
, V
A0
= −V
dc
/2
where, V
AB
= V
A0
– V
B0
, V
BC
= V
B0
– V
C0
, V
CA
= V
C0
– V
A0
