SUBMITED TO: SUBMITTED BY:
Mr. P.K.GANGULY MAHESH CHAND
(Seminar Coordinator) 10ESEEE047
Introduction of Power system stability
Classification of stability
Micro Grid
Interconnection of micro grid
Conclusion
Defination-
Power system stability is an ability of an electric power system for
a given initial operating condition ,To regain a state of operating
equilibrium after being subjected to a physical disturbance with
all system variables are bounded so that practically the entire
system remain intact.
Stability is a condition of equilibrium between opposing forces
instability results when a disturbance leads to a sustained
imbalance between the opposing forces.
Classification is based on the following considerations:
physical nature of the resulting instability
size of the disturbance considered
processes, and the time span involved
Ability to regain normal and stable operation after
being subjected to gradual or slow change in the load.
Concerned with upper loading of machine before
losing synchronism.
Load is assume to be applied at a rate which is slow.
System is Analysis by the set of linear equation.
Action of Voltage regulators and turbine governers are
not included.
Ability to regain normal and stable operation after
being subjected to sudden & large changes in the load.
Losses-generator excitation,transmission,switching
operations and faults.
Linearization of system equation is not permitted.
Studied on the basis of swing.
Action of Voltage regulators and turbine governer are
not included.
Same as steady state stability
Included action of turbine governers and voltage
regulators.
Study time is 4-10 sec
Power System Stability
Rotor Angle Frequency Voltage
Stability Stability Stability
Small-Signal Transient Short term Long term
Stability Stability
Ability of interconnected synchronous machines to remain
in synchronism after being subjected to a disturbance.
Depends on the ability to restore equilibrium between
electromagnetic torque and mechanical torque of each
synchronous generators.
output power of synchronous machines vary as their rotor
angle swing.
System is Instable by increasing angular swings of some
generators leading to loss of synchronism with other
generators
Transient stability of a synchronous machine is an ability to
remain in synchronism after being subjected to sudden or
large changes in rotor angle.
It’s depend on transient disturbance due to-
nonlinear power-angle relationship
The system is designed in such a way that operated so as to
be stable for a selected set of transmission faults: L-G, L-
L-G, three phases.
Stability is the ability of a power system to maintain
synchronism under small disturbances in rotor angle.
Linearization of system equations is permissible for
analysis
Instability that may result can be two forms:
due to lack of sufficient synchronizing torque
due to lack of sufficient damping torque
Frequency stability is an ability to return stable or normal
operation at rated frequency after being subjected to
imbalance between generation or load.
Instability is occurs due to sustained frequency swings
leading to tripping of generating units or loads
In a small system, frequency stability could be of concern
for any disturbance causing a significant loss of load or
generation
frequency stability problem are associated with equipment
responses, poor coordination of control and protection
systems.
Ability of power system to maintain steady state voltages at
all buses in the system after being subjected to a
disturbance.
voltage instability due to-
A disturbance
increase in load demand
change in system condition causes a progressive and
uncontrollable fall or rise in voltage of buses.
Reactive power and voltage control actions are not proper.
Voltage stability is improved by using tap changing
transformers, booster transformer , series & shunt
capacitor, synchronous phase modifiers
Short term voltage stability-
involves dynamics of fast acting load component.
study period of interest is in the order of several seconds
faults/short-circuits near loads could be important.
Long term voltage stability-
Involve Slower acting equipment .
Study period in minutes.
Power supply for small
community.
Power is generated by
renewable sources.
Generation for local load
Transmission with less
Losses
Usually using solar and
wind sources
Smart control
Reasons for connecting a micro grid to a main grid:
Availability
Operations/stability
Economics
Micro grids are typically planned with extra capacity with respect
to the local load. This extra power capacity can be injected back
into the grid in order to obtain some economic benefit
Grid interconnection allows to reduce fuel operational costs by
using the grid when electricity costs are low.
By Switchgear By Static Switch
It is the costlier option but it is also the most flexible one.
Both real and reactive power flow can be controlled.
Power system is always required normal and stable
operation at rated operating condition & it’s also required
improvement of stability .
Stability of power system is improved by using shunt &
series capacitors, governing system and Facts controllers.
Micro grid is satisfied local load areas.
Reduce transmission losses.
Power is generated by renewable energy sources and ceate a
power park.
