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Tampere University of Technology
Electrical Engineering

Enrigue Acha

Ouestion 1:

Flexible Transmission Systems DEE-24126 16.10. 2014

Programmable calculator allowed 5 guestions/ 6 p

A) Describe the term characteristic harmonics in connection with a six-pulse thyristor-

B)

Ouestion 2:

The TCR eguivalent susceptance is: Bp =

controlled reactor (TCR). (2p)

A static var compensator (SVC) connected to bus 7 through a connecting power
transformer, injects reactive power O to bus / of the power network, as shown
schematically in Fig. 1. The nominal reactance of the TCR's linear inductor and the
capacitor are 0.05 and 0.10 p.u., respectively. The leakage reactance of the power
transformer is 0.10 p.u. Determine the amount of reactive power that the SVC would
need to produce to keep the nodal voltage magnitude at bus / at 1.04 p.u. for the case

when the thyristor's firing angle Grcr is 120%. (4p)

  
  
 

V=1.04/0p.u.

jX=j0.10 p.u.

JX7 =j 0.05 p.u.
= -jXc = -j 0.10 p.u.
Orcrx"

Figure 1

2(7-a)+sin2a
NT ;

 

A) State two practical power systems applications of a STATCOM. (2p)
B) Explain the working principles of the bipolar, sinusoidal PWM control when operating

in its linear region and in connection with a three-phase, two-level converter. In
particular, refer to the amplitude modulation index and to the freguency modulation
index, in your discussion. Use any eguations and figures that you may find useful to
enhance your explanation. (4p)

16)

 
 

 

Tampere University of Technology
Electrical Engineering

Enrigue Acha

Ouestion 3:

Ouestion 4:

Flexible Transmission Systems DEE-24126 16.10. 2014

Programmable calculator allowed 5 guestions/ä 6 p

A) Contrast the main constructional and operational differences of the so-called static var
compensator and the STATCOM.. (2p)

B) For the circuit shown in Fig. 3 determine the nodal voltage solution at the end of the first
iteration of the power flow Newton-Raphson method. Take bus 1 to be the slack bus.
The voltage magnitude at bus 2 is kept at the specified value by action of the SVC
connected at the bus. To start the iterative solution, assume the following starting values:

V1=1 p.v.; G=0rad;V,=1 p.v.; 0=0.1rad ; Bse=0.5 p.u.

The iterative power flow solution yields information of the voltage phase angle at bus 2
and the value of SVC susceptance. (4p)

P=1p.u.

0,=0.5p.u.

 

Figure 3

The schematic diagram of a conventional HVDC link is shown in Fig. 4. It uses two 6-pulse
converters rated at 50 MW and 80 kV, to link a wind farm on an island to a load supply point
in the mainland, some 70 km away. The island electrical subsystem is referred as System 1
and the mainland subsystem is referred as System 2. The line-line voltage at the high-voltage
side of System 1?s converter transformer is 192 kV and the freguency is 50 Hz. Its source
inductance is 5 mH. The phase voltage at the high-voltage side of System 2?s converter
transformer is 270 kV and the freguency is 50 Hz. Its source inductance is 7 mH. The cable
has a DC resistance of 3.75 9. If the HVDC link is carrying constant current of 400 A and
delivering 30 MW into the inverter station, find the firing advance angle of the inverter and
the firing angle of the rectifier. (6p)

 

 

 

 

 

 

 

Figure 4

203)
 

 

 

Tampere University of Technology
Electrical Engineering

Flexible Transmission Systems DEE-24126 16.10. 2014

Enrigue Acha Programmable calculator allowed 5 guestions/ & 6 p

Ouestion 5: — Describe in detail the main physical and operational characteristics of a FACTS eguipment
of your choice, emphasizing those Characteristics that can be accommodated within the
Power Flow application using the Newton-Raphson algorithm. Use as many diagrams and
eguations as you may deemed necessary to carry out a comprehensive description. (6p)

303)