This document discusses power control in power systems and summarizes key concepts. It outlines four main constraints: 1) active power constraint, 2) reactive power constraint, 3) voltage magnitude constraint, and 4) load angle constraint. It then defines active and reactive power, explains the need for reactive power compensation, and lists various reactive power compensation devices. The document also discusses excitation control and voltage regulation in generating stations, voltage control using tap changing transformers, and other voltage control methods.

1. POWER CONTROL IN
POWER SYSTEMS
PRESENTED BY:
G.Abhinash(1608-12-734-001)
C.Shiva (1608-12-734-303)
CH.Sandeep(1608-12-734-317)

2. CONSTRAINTS:
CONSTRAINTS MEANS LIMITATIONS OR
BASIC OPERATING CONDITIONS IN
POWER SYSTEM
FOUR CONSTRAINTS ARE THERE.
1.ACTIVE POWER CONSTRAINT
2.REACTIVE POWER CONSTRAINT
3.VOLTAGE MAGNITUDE CONSTRAINT
4.LOAD ANGLE CONSTRAINT

3. ACTIVE POWER
 The actual amount of power being used, or dissipated in a
circuit is called active power
 It is also called as true power
 True power is a function of a circuit’s dissipative elements,
usually resistances(R)
 It is measured in watts(symbolized by the capital letter P, as
always)

4. Reactive Power
Power is referred as the product of voltage and current
P = V x I
 In an ac transmission, when the voltage and current go up
and down at the same time, i.e. when voltage and current are
in phase or in synch, only real power is transmitted and when
there is a time shift between voltage and current both active
and reactive power are transmitted.

5. Need for Reactive Power Compensation
 Reactive power generated by the ac power source is stored in a
capacitor or a reactor during a quarter of a cycle and in the next
quarter of the cycle it is sent back to the power source. Therefore the
reactive power oscillates between the ac source and the capacitor or
reactor at a frequency equals to two times the rated value (50 or 60
Hz). So to avoid the circulation between the load and source it
needs to be compensated .
 Also to regulate the power factor of the system and maintain the
voltage stability we need to compensate reactive power .

6. Reactive Power Compensation Devices
 Series Compensation (Capacitors or Reactors)
 Shunt Compensation (Capacitors or Reactors)
 Synchronous Condensors
 Static VAR Compensators
 Static Synchronous Compensator (STATCOM)

7. Excitation Control and Voltage
Regulation in generating Stations
 The induced emf of synchronous generator (E) depends upon the
excitation current (field current). The terminal voltage V of synchronous
generators are given by V = E – IX The generators have excitation and
automatic voltage regulation systems (AVR). The function of this systems
are:
 To control the load under steady state operating conditions for operating
near steady state stability limit
 To regulate voltage under fault conditions (faults in the grid system
beyond generator protection zone)
 To enable sharing of reactive power. The reactive power shared by a
generator depends upon its excitation level The terminal voltage of the
synchronous generator is held within the permissible limits by automatic
voltage regulators (AVR) systems

8. Voltage Control by Tap changing in
transformers
 The voltage control of transmission and distribution
systems is obtained basically by tap-changing Tap
changers are either on-load or off load tap changers.
By changing the turns ratio of the transformer the
voltage ratio and the secondary voltage is changed and
voltage control is obtained. Tap changing is widely used
voltage control method employed at every voltage level
 The voltage control of the range + 15 to -15 % can be
achieved by tap changing transformers

9. Off load tap changing voltage control
 Adjustment of voltage ratio can be made by off-circuit tap changing.
These adjustments are usually for seasonal load variations of special
operational requirement of local substations and adjusting the
voltage in distribution transformer at consumer end.

10. On-Load tap changing voltage
control
 Such an arrangement of on-load tap changing is employed
for changing the turn-ratio of the transformer to regulate the
system voltage while the transformer is delivering load.

11. OTHER METHODS OF
VOLTAGE CONTROL
 Using shunt reactors
 Using shunt capacitors
 Using static shunt compensation
 Using synchronous condenser
 Using series capacitors
 Using FACT devices

12. WHAT IS LOAD ANGLE..?
 Load angle “delta” is angle between the generator induced
E.M.F & Generator terminal voltage.
 Physically, this is the angle by which the reference line made
on the generator shaft front deviates from no load to load
condition.

13. Causes:
 Sudden increase in load
 Sudden change in excitation to the generator
Control of load angle
 By using automatic voltage regulators

14. 1.ACTIVE POWER CONSTRAINT:
Pmin < P < Pmax
2.REACTIVE POWER CONSTRAINT:
Qmin < Q < Qmax
3.VOLTAGE MAGNITUDE CONSTRAINT:
|V|min < |V| < |V|max
4.LOAD ANGLE CONSTRAINT:
min < max

15. LOAD FLOW ANALYSIS:
* IT IS A BALANCED MECHANISM
BETWEEN DEMAND AND GENERATION
UNDER INCREMENTAL LOADING
CONDITIONS
*AT PRESENT,, FOR SAFE OPERATION
OF THE SYSTEM AND IN FUTURE,, FOR
THE EXTENSION OF POWER SYSTEM

16. BUS CLASSIFICATION
(a) LOAD BUS (OR) P-Q BUS
(b) GENERATOR BUS (OR) P-V BUS
(c) SLACK BUS

17. BASIC POWER FLOW CONDITIONS:
1.REACTIVE POWER IS
PROPORTIONAL TO BUSBAR
VOLTAGE
2.ACTIVE POWER IS
PROPORTIONAL TO LOAD ANGLE

18. CASE - 1:
CONSIDER THE DIAGRAM

19. CASE - 2:
CAPACITANCE EXISTS IN SHUNT, DISTRIBUTED
ALONG THE LINE AS SHOWN IN THE FIGURE