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Assignment 1

This document contains an assignment for an HVDC and FACTS course. It includes 4 problems related to thyristor converters and HVDC transmission systems. Problem 1 has 11 parts analyzing the operation of a 3-phase thyristor rectifier, including voltage and current waveforms. Problem 2 involves simulating another thyristor rectifier and calculating power quality metrics. Problem 3 requires calculating power flows in an HVDC system. Problem 4 analyzes line notching from a thyristor rectifier and compares the results to limits.

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248 views4 pages

Assignment 1

This document contains an assignment for an HVDC and FACTS course. It includes 4 problems related to thyristor converters and HVDC transmission systems. Problem 1 has 11 parts analyzing the operation of a 3-phase thyristor rectifier, including voltage and current waveforms. Problem 2 involves simulating another thyristor rectifier and calculating power quality metrics. Problem 3 requires calculating power flows in an HVDC system. Problem 4 analyzes line notching from a thyristor rectifier and compares the results to limits.

Uploaded by

champion2007
Copyright
© © All Rights Reserved
We take content rights seriously. If you suspect this is your content, claim it here.
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Download as PDF, TXT or read online on Scribd
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ECE661

HVDC and FACTS


Fall 2016
Assignment #1
Due date: October 11th, 2016
Problem#1:
A three-phase thyristor converter is shown in Fig. P-1. In the first part of the problem, assume the line
inductance to be neglected. The line voltage rms value is 230V and 50Hz (sinusoidal). The load current
is 10A.
P
T1

T3

T5

ia
a
ib

n
b

vd

Id

ic
c
T4

T6

T2

Fig. P-1
(a)

From the figure, it can be seen that vd = vPn vNn. Make a sketch of these three voltages
for the case that the gate currents are constantly present (=0).

(b)

For the same conditions as in (a), sketch ia, ib, and ic. Indicate in the sketch when the
thyristors are conducing.

(c)

List the conditions needed for a thyristor to start conducting. What are the conditions for
it to stop conducting

(d)

Sketch vd, vPn and vNn for the firing angle, , equal to 60o.

(e)

Find the equation for the average value of the dc voltage vd, where the firing angle is a
variable.

(f)

Calculate the ac power passing through the rectifier when the firing angle is 60o

For the rest of the problem, assume Ls = 5mH, in all the phases.
P
T1
Ls

T3

T5

ia

Ls

ib

vd

Ls

Id

ic

c
T4

T6

T2

(g)

Sketch vd, vPn and vNn keeping , still equal to 60o.

(h)

Find the equation for the average value of the dc voltage vd, where the firing angle is a
variable, taking the influence of the line inductance Ls into the consideration

(i)

Calculate the firing angle that provides the same power as in (f).

(j)

Find the commutation angle u in this case.

(k)

What is the maximum value of in the inverter mode that doesnt cause commutation
failure if the 6 thyristors ratings: 620A, 1200V and tq=30s.

Problem #2:
A three-phase thyristor converter is supplied by a 480-V (line-to-line), 60-Hz source. Its internal
inductance Ls1 = 0.2 mH. The converter has a series inductance LS2 = 1.0 mH. The load is represented
as shown in Fig. P-2, with L = 5 mH, R = 0, and E = 600 V and the delay angle = 20o.
1. Simulation the system using PSCAD/EMTDC, PSIM or PSpice and obtain the waveforms of
Vd, Id, ia, Vab,source, Vab,PCC and Vab,terminal
2. Calculate Ia1, Ia, DFia, DPF, PF and %THDia, %THDva,PCC, %THDva,terminal.

Fig. P-2

Problem#3:
Consider the following HVDC transmission system:

Fig. P-3
Find the following:
1. Id, Pd, DC linelosses, ur, ui, DPFr, DPFi, Ir1, Ii1,
The the magnitude and dirction of P1, P2, Q1 and Q2
2.
Problem#4:
In the circuit of Fig. P-4, Ls1 corresponds to the leakage inductance of a 60-Hz transformer and it is
equal to 27.65 m . Assume Ls2 is due to a 200-ft-long cable, with a per-phase inductance of 0.1 H/ft.
If the ac input voltage is 460 V line to line and the dc side of the rectifier is delivering 25 kW at a
voltage of 525 V,
1. calculate the notch width in microseconds and the line notch depth in percentage at PCC.
2. calculate the area for a deep line notch at PCC in volt-microseconds and
3. compare your answers with the recommended limits.

Fig. P-4

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