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LOAD FLOW STUDY IN POWER SYSTEM
A THESIS SUBMITTED IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
Bachelor of Technology
In
Electrical Engineering
BY
BHABANI SANKAR HOTA (107EE007)
& AMIT KUMAR MALLICK (107EE016)
Department of Electrical Engineering National Institute of Technology Rourkela-769008 ,
LOAD FLOW STUDY IN POWER SYSTEM
A THESIS SUBMITTED IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
Bachelor of Technology
In
Electrical Engineering
BY
BHABANI SANKAR HOTA (107EE007)
& AMIT KUMAR MALLICK (107EE016)
Under the guidance of
Prof. P.C.PANDA
Department of Electrical Engineering
National Institute of Technology
Rourkela-769008 ,
ACKNOWLEDGEMENT
I would like to express my deepest sense of gratitude towards my
supervisor, Prof. P.C.Panda who has given me much suggestion,
guidance and support.
I would like to thank all the staff members of Department of
Electrical Engineering for their extended cooperation and guidance.I
also take this opportunity to give thanks to all others who have
given me support for the project or in other aspects of my study at
National Institute of Technology.
Bhabani Sankar Hota
107ee
Amit Kumar Mallick
107ee
Date: 09.05.
Place: Rourkela
LOAD FLOW STUDY IN POWER SYSTEM
Abstract
This paper presents a brief idea on load flow in power system, bus
classification ,improving stability of power system ,flexible ac system, various
controllers of FACTs and advantages of using TCSC in series compensation .It
presents the modeling scheme of TCSC and the advantages of using it in power
flow network. The plots obtained after simulation of network using matlab
both with and without TCSC gives fair idea of advantages on use of reactive
power compensators.
3.7 Thyristor controlled Series
LIST OF FIGURES PAGE NO
CHAPTER I
INTRODUCTION TO LOAD
FLOWS
1.1 INTRODUCTION
In a three phase ac power system active and reactive power flows from the generating station to the load through different networks buses and branches. The flow of active and reactive power is called power flow or load flow. Power flow studies provide asystematic mathematical approach for determination of various bus voltages, there phase angle active and reactive power flows through different branches, generators and loads under steady state condition. Power flow analysis is used to determine the steady state operating condition of a power system. Power flow analysis is widely used by power distribution professional during the planning and operation of power distribution system.
Fig 1.
There three methods for load flow studies mainly #Gauss siedel method
Newton raphson method
Fast decoupled method.
VARIABLES AND BUS CLASSIFICATION
Buses are classified according to which two out of the four variables are specified
Load bus : No generator is connected to the bus. At this bus the real and reactive power are specified.it is desired to find out the volatage magnitude and phase angle through load flow solutions.It is required to specify only Pd and Qd at such bus as at a load bus voltage can be allowed to vary within the permissible values.
Generator bus or voltage controlled bus : Here the voltage magnitude corresponding to the generator voltage and real power Pg corresponds to its rating are specified.It is required to find out the reactive power generation Qg and phase angle of the bus voltage.
Slack (swing) bus : For the Slack Bus, it is assumed that the voltage magnitude | V | and voltage phase Θ are known,whereas real and reactive powers Pg and Qg are obtained through the load flow solution.
CHAPTER II
INTRODUCTION TO FACTS
2.2 FACTS SYSTEM CONTROLLER
TYPES ATTRIBUTES
NGH- SSR Damper Damping of oscillation,series impedance control, transient stability
SVC-static var-compensator Voltage control,var-compensation damping of oscillation
TCSC-Thyristor controlled series capacitor Power control,voltage control,series impedance control,damping of oscillations,transient stability Static-condensor Voltage control,var-compensator damping of oscillations,transient stability. Thyristor controlled phase angle regulator Power control,voltage control,var- compensator,damping of oscillation,transient stability. Thyristor controlled dynamic brake Damping of oscillation,transient stability.
SVC - Uses thyristor valves to rapidly add or remove shunt connected reactors and or capacitors often in coordination with mechanically controlled reactors and/or capacitors. NGH-SSR damper - a resonance damper:- A thyristor ac-switch connected in series with a small inductor and resistor across the series capacitor.
Statcon(static condenser) :- A 3 phase inverter that is driven from voltage across a
dc storage capacitor and whose there output voltages are in phase with the ac system voltage.when the output voltages are higher or lower than the ac system voltage the current flow is caused to lead or lag and difference in voltage amplitudes determine how much current flows.Reactive power and its polarity can be controlled by controlling voltage.
Phase Angle Regulator :-The phase shift is accomplished by adding or
subtracting a variable voltage concept that is perpendicular to the phase voltage of the line
Unified powercontrol :- In this concept an ac voltage vector generated by a thyristor based inverter is injected in series with phase voltage.The driving dc voltage for inverter is obtained by rectifying the ac to dc from the same transmission line. In such an arrangement the injected voltage may have any phase angle relationship to the phase voltage. It is possible to obtain a net phase and amplitude voltage change that confers control of both active and reactive power. Dynamic Brake :- A shunt connected resistive load, controlled by thyristor switches. such a load can be selectively applied in each pass, half cycle by half cycle to damp any specific power flow oscillation, so that generating unit run less risk of losing synchronism ,as a result more can be transferred over systems subjected to stability constraints.
A thyristor controlled resistor in parallel with the transmission line can be used effectively to damp power swing oscillations in the transmission system.
FACT technology ensures power flow through prescribed routes, maximization of capacity, securing loading capacity enhancement under various scenanious of uprating or upgrading the lines thermal current capacity.
One of the important function of FACT is VAR compensation.
2.3 VAR -compensation is defined as the management of reactive power to improve the
performance of ac power systems;maximizing stability by increasing flow of active power.
Problems forced while reactive power compensation :-
- Load compensation
- Voltage support.
Load compensation objectives are to increase the value of the system power factor to balance the real power drawn from the ac supply,compensate voltage regulation and to eliminate current harmonic components produced by large and fluctuating non – linear industries loads.
Voltage support objectives:- Its generally required to reduced voltage fluctuations at a given terminal of a transmission line.
Var compensation helps to maintain a substantially flat voltage profile at all levels of power transmission improves HVDC conversion terminal performance increases transmission efficiency ,controls steady state and temporary over-voltage and can avoid disastrous blackout.
CHAPTER III
PRINCIPLES OF REACTIVE
POWER COMPENSATION
3.1 REACTIVE POWER
Power factor is defined as the ratio of real power to apparent power. This definition is often mathematically represented as Kw/Kva ,where the numerator is the active (real) power and the denominator is the (active+reactive) or the apparent power
Power Factor = Active power/Apparent power = kW/kVA
= Active power/ (Active Power +Reactive Power) = kW/(kW+kVAr)
The higher kVAr indicates low power factor and vice versa.
HOW TO IMPROVE POWER FACTOR
Power factor can be improved by adding consumers of reactive power in the system like Capacitors or Synchronous Motors.
It can also be improved by fully loading induction motors and transformers and also by using higher rpm machines. Usage of automatic tap changing system in transformers can also help to maintain better power factor.
PRINCIPLES OF REACTIVE POWER COMPENSATION
In a linear circuit the reactive power is defined as the ac- component of the instantaneous power with a frequency equal to 100hz in 50hz system ( 120 hz in 60 hz system).The reactive power generated by the ac power source is stored in a capacitor or a reactor during a quarter cycle and in the next quarter cycle is sent back to the power source. Eg reactive power oscillates between ac source and the capacitor or reactor.
3.2 SHUNT COMPENSATION : By supplying reactive power near load, tension on lines ,
power losses minimizes and hence improving voltage regulation.
This can be achived in three ways:
(a) With a capacitor
(b)Voltage source
(c) Current source
