expert lecture
DESCRIPTION
This presentation explains aspects of power system modelling and simulation. Moreover it deals with different controls of isolated generator and their controls to to augment power system stability briefly.TRANSCRIPT
Prof. Viren B. PandyaAsst. Prof. (EED)L. D. College of Engg.Ahmedabad-380015
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*Introduction
*Modeling of Synchronous Generators
*Modeling of Transformer, Transmission line
*Load Modeling
*ALFC & AVR Modeling, Simulation & Analysis
*Load Flow Simulation & Analysis
*Short Circuit Simulation & Analysis
*Stability Studies
*Power System State Estimation
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*Current scenario of power system: large dimensionality of interconnections, complexity and problems pertaining to stability
*Need for contemporary approach to study and assess power system performance
*Accurate modeling of power system components
*Use of simulation packages (like ETAP, NEPLEN, MiPOWER, PSCAD, Dig-Silent, SKM)
* Deployment of FACT devices at EHV levels
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*What is modeling and simulation?*To express physical device/ equipment /system in terms
of mathematical expressions containing various parameters/variables (e.g. V, I, P, Q, S, f etc.) so as to make computer understand its typical behavior / characteristics.
*Simulation is the process of solving these modeled equations on digital computer with proper programming methods for predicting behavior of system under some typical given situations.
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*The most crucial component of power system
*Turbo-alternators and Hydro-generators
*Mathematical modeling requires Park’s transformations (dq0) to be used
*For load flow analysis classical model is used i.e. Constant voltage source in series with synchronous impedance/reactance
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*IEEE classification synchronous machine models for computer simulation*Model (0.0): Classical model of synchronous machine
neglecting flux decay and damper winding *Model (1.0): Field Circuit model with no damper windings
and only field winding on d-axis is considered.*Model (1.1): field circuit with only one equivalent damper
on q-axis.*Model (2.1): field circuit with one equivalent damper on d-
axis and one damper on q-axis.*Model (2.2): field circuit with one equivalent damper on d-
axis and two dampers on q-axis.*Model (3.2): field circuit with two dampers on d-axis and
two dampers on q-axis*Model (3.3): field circuit with two dampers on d-axis and
three dampers on q-axis.
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*Transformer is modelled as an impedance in percentage (pu x 100) value
*Load Tap Changer settings to be specified
i.e. taps need to be given in terms of min. and max. tap in % of rated kV alongwith total no. of taps available
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*There are two ways to model it for large system study i.e. T and
*In all software packages is preferred.
Why?
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*Three static loads: Constant power, constant impedance, constant current
*Dynamic load model: induction motor, synchronous motors
*Composite load modeling
V
P Constant current
Constant impedance
Constant power
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*Need for generator controllers
*P-f control loop: ALFC
*Q-V control loop: AVR
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Speed governing
system
Speed reg./Droop
Power system
Non-reheat turbine
Power signal from PI controller
Load/Demand variation
Frequen. error output
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Time domain response of frequency error for unit step load
Viren B. Pandya 17Drooping Characteristics of Speed Governing System or primary ALCF
loop characteristics
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Load frequency control loop with PI controller
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Time domain response of frequency error for unit step load with PI controller
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TWO AREA control
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Time domain response of frequency error for TWO AREA control
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*To brace control on terminal voltage of synchronous generator
*Reactive power control
*Q-V loop controller
*Various excitation systems like DC, controlled and uncontrolled rectifier type Brushless excitation systems with automatic voltage regulators
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DC Excitation System
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Brushless Rotating Rectifier Excitation System
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Modeling steps for brushless excitation
system without
compensation
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*To mitigate small signal oscillations in generator rotor by controlling its excitation using an auxiliary signal
*Produces component of electrical torque in such a phase so as to decrease rotor oscillation
*Frequency range is 0.1 to 2.0 Hz
*For small signal stability simulation
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*Steady state analysis of power system with solution of non-linear algebraic equation (static load flow equations) keeping total generation and load constant.
*Methods: GS, Accelerated GS, NR, FDLF
*Classical Model approach
*Data required for different models
*Swing, voltage controlled and MVAr controlled buses
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*Symmetrical and Unsymmetrical faults, simulation as per IEC and IEEE
*Use of Zbus
*To determine fault level in terms of MVAshortcircuit
bshortcircuit
pu
MVAMVA
Z
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*It is the ability of the dynamic power system to remain in synchronism under normal operating condition & to regain an acceptable equilibrium state after being subjected to perturbation.
*Broad classification according to IEEE has been taken here.
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*It is the ability of the dynamic power system to remain in synchronism under normal operating condition & to regain an acceptable equilibrium state after being subjected to perturbation.
*Broad classification according to IEEE has been taken here.
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*“Power System Stability” by Edward Wilson Kimbark
*“Power System Stability and Control” by P. S. Kundur
*“Power System Dynamics” by K. R. Padiyar
*“Power System Operation and Control” by Halder and Chakrabarti
*EEE Committee Report, “Computer Representation of Excitation
System”, IEEE Trans. on PAS, Vol. PAS-87, No. 6, June 1968.
*IEEE Committee Report, “Dynamic Models for Steam and Hydro
Turbines in Power System Studies”, IEEE Trans. on PAS, Vol. PAS-
92, No. 6, Nov./Dec. 1973.
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