1

POWER GENERATION OPERATION AND CONTROL

Presentation by

Bruce F. Wollenberg

University of Minnesota

2

Course is based on textbook by Allen J. Wood Bruce F. Wollenberg Gerald B. Shebl

3 3 3

Power System Operations

Operations is a 24 hours/day, 365 days/year job

Photo courtesy Xcel Energy, Minneapolis MN

Large economic effect on

power delivery costs

Economic Dispatch

Unit Commitment

Hydro Scheduling

Fuel Scheduling

4

ECONOMIC DISPATCH

5

Fuel Input$/ton$/bbl$/cuft

Power Output

MW

Students learn to use Lagrange functions and the KKT optimal conditions and how to interpret Lagrange multipliers

Fuel Input$/ton$/bbl$/cuft

Power Output

MW

Fuel Input$/ton$/bbl$/cuft

Power Output

MW

How do we allocate MW output to the generators to minimize the total cost of operating all generators

Scheduling Generation to meet hourly

load the Unit Commitment Problem

0 20 40 60 80 100 120 140 160 1801000

1200

1400

1600

1800

2000

2200

2400

2600

2800

3000

Hours

MW

Hourly load for one week

Sunday Monday Tuesday Wednesday Thursday Friday Saturday

6

Students learn how To use Dynamic Programming and Lagrange Relaxation

Hydro units on river networks and

fuel delivery networks

Schedule oil usage so as to not empty storage tank until new supplies are available

7

Schedule hydro to avoid overflow of reservoirs

Students learn to use Linear Programming

Transmission System

8

9 9 9

Power System Security

Lightning, rain, wind, and vehicles can cause a transmission line to fail

Failure can result in other lines overloading and voltages to sag

Operations must take transmission

system into account

All lines and transformer flows within limit

All bus voltage magnitudes within limit

No first contingency outages will result in any flow or

voltage limit violations (the (N-1) rule)

Any violations must be corrected

Economic dispatch must account for transmission losses

10

Students use Newton and Decoupled Power Flow, Linear Power Flow and PTDF and LODF factors

11 11 11

What Happens If We Ignore

System Security?

Times Square, New York City, August 14, 2003

12

Control of Generation, frequency,

and power interchange

L O A

D

G O

V

Pre f

G 3

G 4

G O

V

G O

V

Pre f

Pre f

G O

V

Pre f

C o n tro l A re a R e d C o n tro l A re a B lu e

A G C T ie F lo w

Fr e

qu

en

cy

Ge

ne

ra

t or O

ut p

ut

Ge

ne

ra

to

r O

utp

ut

Automatic Generation Control

(AGC)

13

Students learn the importance of well thought out practical control systems

Large Mathematical Applications

State Estimation (least squares and orthogonal decomposition)

Calculate the power flow state from real time measurements

Detect and identify bad measurements

Optimal Power Flow (incremental LP and interior point optimization)

Minimize operating cost

Power flow for entire transmission system as set of constraints

Extend to market calculation of demand and supply

Optimal Power Flow with flow

and line outage constraints

15

Power System Operations

16

Short Term Demand Forecasting

17

Function Forecast Horizon Forecast Intervals

Automatic Generation Control (AGC) Next 15 Minutes 5 Seconds

Economic Dispatch (ED) Next Hour 30 Seconds

Power Flow (PF) Next 2 Days Five Minutes

Optimal Power Flow (OPF)

Contingency Analysis (CA) Next 2 Days Ten Minutes

Situational Awareness (SA) Next Hour 120 Samples Per Second

Voltage Stability (VS) Next Hour 120 Samples Per Second

Unit Commitment (UC) Next 14 Days Hourly

Transaction Evaluation & Management (TEM) Next 14 Days Hourly

Wind Forecasting Next 5 60 minutes 30 seconds

Hydro Forecasting Next 14 days Hourly

Fuel Scheduling Next 1 6 months Weekly

Students are introduced to basic time series modeling such as Box Jenkins, weighted least squares, innovations estimation etc.

Thank you

18