expert lecture

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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