Hello , I need help with a Power Electronics projects about Electric train systems in Australia , it involves simulation using Mathlab and a written report.

LITERATURE REVIEW
Overview of project:
The complete structure of project is shown in fig.1. single phase supply of 25kV ac supply is
taken from substation through pantograph. It is given to step down transformer where it get step
down 2000V ac. 2000V ac supply is converted to DC voltage by using AC-DC converter. DC
output is given to DC bus link which will connect to various DC to AC converter which is shown
in fig.1.
Fig.1 : complete block diagram of Electric traction .
The main parts of projects are AC-DC converters and DC-AC converters. The Detail study of
these converter is done below.
AC-DC converters
The single phase fully controlled rectifier permits adaptation of single phase AC into DC.
Usually this is used in various uses such as battery charging, speediness control of DC motors
and obverse end of UPS (Uninte
uptible Power Supply) and SMPS (Switched Mode Power
Supply).
All four component used are thyristors. The turn-on moments of these devices is decided by
firing signals that are given. Turn-off occurs when the cu
ent over the device reaches zero and it
is reverse biased at least for period equal to the turn-off time of the device defined in the data
sheet.
an uncontrolled (diode) converter is to be simulated, all 4 devices should be fired at a delay
period of 0⁰. When a semi-converter is to be simulated, the lower two devices can be excited at
0⁰ and 180⁰ respectively and the higher two devices are fired at α and 180⁰+α.

Normally in a fully controlled converter, the cu
ent transmission takes place from T1 to T2
immediately without any time delay. But when a source inductance is there so the stored energy
in Ls has to be used before the cu
ent transfer or commutation takes place from T1 to T2.
Because of this, T1 and to T2 will conduct instantaneously from α to α+u (where u is the overlap
angle) producing short circuiting of the DC load during the overlap period u. This is called as
commutation overlap.
Fig.2: single phase Full controlled Rectifier.
When the thyristor converter has a resistive load, both DC cu
ent and voltage will be in the
same phase. As soon as the +ve half-cycle ends, the cu
ent over thyristors T1 and T11 will be
attaining zero after which they would be reverse biased due to the supply voltage boarding into
negative half-cycle. This causes the voltage pulses to be distributing from firing angle α to π as
shown in the Fig.3. Both the cu
ent in the DC connection (Idc) and the cu
ent in the source (Is)
will be intermittent.
Fig .3: Waveforms of single-phase converter with resistive load for a firing angle of 30°
Fig 4 :Waveforms for a firing angle of 60° with extremely inductive load and Ls being present zero
voltage period (in Vdc- DC output voltage) from about 43.5 to 45 msec indicates the commutation
overlap interval

DC TO 3-PHASE AC CONVERSION
a 3-phase
idge type VSI with square wave end voltages has been measured. The output from
this inverter is to be fed to a 3-phase balanced load. Fig. 5 shows the power circuit of the 3Ø
inverter. This circuit may be recognized as three single-phase half-
idge inverter circuits put
across the similar dc bus. The specific pole voltages of the 3-phase
idge circuit are matching to
the square pole voltages output by 1Ø half
idge or full
idge circuits. The three pole voltages
of the 3-phase square wave inverter are moved in time by one third of the output time duration.
These pole voltages along with some other applicable waveforms have been shown in Fig. 6.
Fig. 5: A 3-phase Voltage Source Inverter (VSI) feeding a balanced load
Fig. 6: Some relevant voltage waveforms output by a 3-phase square wave VSI
FAULT PROTECTION
Electric traction consist of both AC...