Power control in power systems

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)

CONSTRAINTS:

CONSTRAINTS MEANS LIMITATIONS OR BASIC OPERATING CONDITIONS IN POWER SYSTEM

FOUR CONSTRAINTS ARE THERE.

1.ACTIVE POWER CONSTRAINT2.REACTIVE POWER CONSTRAINT3.VOLTAGE MAGNITUDE CONSTRAINT4.LOAD ANGLE CONSTRAINT

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)

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.

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 .

Reactive Power Compensation Devices

Series Compensation (Capacitors or Reactors) Shunt Compensation (Capacitors or Reactors) Synchronous Condensors Static VAR Compensators Static Synchronous Compensator (STATCOM)

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

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

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.

05/01/2023 10On-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.

OTHER METHODS OF VOLTAGE CONTROL

Using shunt reactors Using shunt capacitors Using static shunt compensation Using synchronous condenser Using series capacitors Using FACT devices

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.

Causes: Sudden increase in load Sudden change in excitation to the generator

Control of load angle By using automatic voltage regulators

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

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

BUS CLASSIFICATION

(a) LOAD BUS (OR) P-Q BUS

(b) GENERATOR BUS (OR) P-V BUS

(c) SLACK BUS

BASIC POWER FLOW CONDITIONS:

1.REACTIVE POWER IS PROPORTIONAL TO BUSBAR VOLTAGE

2.ACTIVE POWER IS PROPORTIONAL TO LOAD ANGLE

CASE - 1:CONSIDER THE DIAGRAM

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

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