Optimization of Auxiliary Power at Thermal Power Plant using Variable Frequency Drive (VFD)

Scope of

Project

Efficiency

Revision

Pollution

Control

Energy

Saving

Aspects of Project

Analysis of Auxiliary Power

Crux of Excessive Power Consumption

Scope of Power Saving

Introduction Of Variable Frequency Drive for 3 phase Induction motors

Power saving and simulation model of VFD

Power required to run various pumps and motors

Power required for the instrumentation and control room

Power required to charge the unit and station buses

Power required to run the basic auxiliary and necessary equipment’s for the starting and subsequent operation of Power

Apparatus

Auxiliary Power

Auxiliary Power

BFP, 4000 kW

ID Fan, 1300kW

PA Fan, 1250kW

Secondary Crusher, 750kW

FD Fans, 750kW

CE Pumps, 600kW

Conveyer Belts, 280kW Primary Crusher, 225kW

Induction Motor

•Singly Excited•Runs at constant speed, constant torque,

constant slip at fixed frequency

•Speed can change if frequency changes •Torque is given as

s

2

2

222

2

3

( )

THind

s

TH TH

V R

sRR X X

s

fr

Torque Speed Characteristics of IM

Induction Motors at Thermal Power PlantUse:•Reciprocating Pumps•High Pressure Pumps•Boiler Feed Pumps•Compressors•Draft Fans

Need of Optimal Draft

•Draft is a negative pressure that has to be maintained between stacks and boiler

•Dependency on Load Factor•To improve the efficiency of Rankine

Cycle•To reduce the carbon foot print•To improve the boiler efficiency

How Negative Draft is Maintained?•By controlling the flow of flue gases.

1) By varying the speed of Motor 2) By varying the cross section through which gases are being passed away

•Dampers are used to control the flow.

Dampers

•Provides the negative draft proportional to the flue gases produced

•Installed at the outlet of pump•Are operated as per the load demand•Controlled by Servo Mechanism •Control signal is calibrated with Electro

Governing System

Energy consumption and DampersWith varying position of dampers current drawn by motor varies.

As load increases, flue gases increases

Variation in Damper Openings with Flow

Variable Frequency Drive

Machine

Power Electronics

Measurement

Control System

Power Saving without VFD

Power Saving with VFD

Options for Variable Frequency

Grid Frequency

Generation of Variable Frequency AC by using Inverter

Schematic Approach of VFD

•Inverter is used to generate the 3 phase power supply that is fed in the 3 phase IM

•Frequency of inverted 3 phase supply is controlled by controlling the firing angle of respective switching device

•Thus by varying the frequency speed of motor is varied

Firing Angle Control

•Redirecting the Electro Governing Signal•Calibration of externally excited source

with the load demand•Measurement of flow and electrical

analogous signal corresponding to that flow •Thermocouple interfaced with RTD’s in a

balanced bridged circuit•Capacitive transducer that responds

against the flow and density• PLC interfacing with the Load Curve

Response

Characteristics of VFD

V = K * f * FV is Voltage across induction motorf is supplied frequency to motorF is fluxK is constant

Without VFD With VFD

Motor Speed Constant Variable

Damper Position

Variable Constant

Power Saving Calculation

Program for Power Saving

Power Saving Using VFD

Simulation Model of VFD

Output from Inverter (Variable frequency with test signal)

DC Output

VFD Executed Motor Response

Thanks….