The concept of Power control and power flow analysis are explained in this presentation

1. HIGH VOLTAGE DIRECT LINE TRANSMISSION
“POWER CONTROLAND POWER FLOW
ANALYSIS”
V.KALAIRAJAN M.E;
ASSISTANT PROFESSOR,
ELECTRICALAND ELECTRONICS ENGINEERING
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY,TRICHY
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 1

2. “POWER CONTROL”
VIEWS :
POWER CONTROL:
 CURRENT ORDER.
 VDCOL.
 SUPERVISORY CONTROL.
POWER FLOW ANALYSIS:
 SOLUTION FOR POWER FLOW PROBLEMS:
 DC SYSTEM MODEL:
 BASIC CONVERTER MODEL:
 FLEXIBLE PER UNIT SYSTEM:
 CONCLUSION
 REFERENCES
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 2

3. “POWER CONTROL”
 Power and auxiliary controller is used.
CURRENT ORDER:
 Derived from reference power (Pref) divided by DC Voltage
(Vdc).
VDCOL:
 Used to vary the Current order limits.
 Used to prevent the individual switches(SCR) carrying full current
for long time due to commutation failures.
 Designed based on time delays Transfer functions G1 (s), G2(s)
 G1(s) = 1/(1+sTdown)
 G2(s) = 1/(1+sTup)
 It provides power order to both stations (REC,INV).
 High power (Leading point) Transmit the power to Low Power
Terminal (trailing point) station.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 3

4. “POWER CONTROL”
 The power response for voltage changes is must be fast that is
done by communication links.
 To maintain current limits in both stations. And power changed by
varying voltage.
 V =IR then in a line R is high and variable (Long and different
temp lines) the current order should be calculated at only one
station.
 Transmitted to another station by communication links to maintain
power stepping and in both stations. Digital based ILC Circuits are
used for this power stepping process.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 4

5. “POWER CONTROL”
SUPERVISORY CONTROL:
 PLC used to control communication of stations.
 Acknowledgement signal is sent from Receiving end to sending
end. Based on priority power stepping takes place.
 Not received ACK means previous power maintain in the line till
the next power change and ACK occurrence.
 Auxiliary control used for frequency control of power by using
change in frequency ⌂F. For power stabilizations.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 5

6. “POWER FLOW ANALYSIS”
 Power flow analysis is essential for power system design,
planning, and operation.
 It is done by simulation, it is used to design the steady state model.
 Power and load flow analysis is done by different algorithms
computer programming.
 Newton’s method, fast decoupled load flow method, gauss seidel
method.
 The voltage correction is done by below equations,
 Pi, Qi are real and reactive power at bus.
 θ, V are Bus angle and voltage value.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW
ANALYSIS
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7. “POWER FLOW ANALYSIS”
SOLUTION FOR POWER FLOW PROBLEMS:
Two methods
 1. sequential
 2. simultaneous.
 sequential method is iterative method and it gives separate
solution for AC and DC systems.
 Simultaneous method AC and DC systems are combined after that
it solved. It is undefined method.
 These are used to design the minimize the cost and optimal power
flow system.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 7

8. “POWER FLOW ANALYSIS”
The non linear equations are,
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW
ANALYSIS
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9. “POWER FLOW ANALYSIS”
 For DC system control variables are α,γ and off nominal
transformer ratio ‘a’
 These values are some times specified by the limits.
 Two control variables for one terminal. So N number of terminal
2N specifications are there.
 Finally the real and reactive power are calculated for optimum.
DC SYSTEM MODEL:
Assumptions,
 Ac voltages are sine and constant frequency. The V, I are balanced.
 All harmonics in produced by converter is filtered and no
harmonics in AC system.
 Converter transformer has zero impedance and magnetising
current. Only leakage reactance are considered.
 The valves are ideal, zero voltage drop on that valves.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 9

10. “POWER FLOW ANALYSIS”
 Only Vdc and Idc are considered. Harmonics are neglected.
 In bipolar DC links design , two poles are balanced.
BASIC CONVERTER MODEL:
 For multi bridge system transformer reactance is take it as equal
for all bridges. And convert to single bridge with Vdc.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 10

11. “POWER FLOW ANALYSIS”
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 11

12. “POWER FLOW ANALYSIS”
FLEXIBLE PER UNIT SYSTEM:
 For convenient DC system express in per unit equation.
 For Dc system quantities are identical for all terminal like voltage.
 But no need of identical voltage for AC system voltage quantities.
It is depends the converter bus.
KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS 12

13. “POWER FLOW ANALYSIS”
CONCLUSION:
 In this above presentation we can learn about basic concept
of power control, current order, VDCOL, supervisory
control.
REFERENCES:
 Padiyar, K. R., “HVDC power transmission system”, New
Age International (P) Ltd., New Delhi, Second Edition, 2010.
 Edward Wilson Kimbark, “Direct Current Transmission”,
Vol. I, Wiley interscience, New York, London, Sydney, 1971.
 Kundur P., “Power System Stability and Control”, McGraw-
Hill, 1993.
 Google and wikipedia.
13KONGUNADU COLLEGE OF ENGINERING AND TECHNOLOGY, TRICHY POWER CONTROL AND POWER FLOW ANALYSIS