1

Computer Control of Power Systemsand Energy Management Systems

2

Outline

• Introduction

•Conceptual Model of the EMS

• EMS Functions and SCADA Applications.

• Time decomposition of the power system operation.

• Open Distributed system in EMS

• OOPS

3

EMS

- Enhance the scope of SCADA by providing the power application software to assist the operator in monitoring and control of the electrical network.

It consists of three important phases:

1. Gathering Information: Acquisition of real-time data and man machine information.

2. Decision Making.

3. Action by Transmitting Control Orders either

- Directly [Centralized Remote Control]

- Indirectly [Decentralized remote control or load

control].

4

Conceptual Model of EMS

Fig 1. Typical EMS Architecture

5

Real Time Modeling of the system

• Network Configuration Analysis

• Observability Analysis

• State Estimation and Data processing

• Network Application Functions

6

EMS Application and SCADA Functions

       1. Real-Time Functions

·         Topological Analysis

·         State Estimation

·         Network Equivalent Calculation

·         Security Analysis

·         Generation Dispatch

·         Voltage and Reactive Optimization

 2. Extended Real-Time Functions

·         Short term Load Forecast

·         Operator Load Flow

·         Short Circuit Calculation

7

Online and Off line Tasks in an EMS

8

The Functions in the EMS can be classified as

1. Primary Analysis (Perform decision making tasks)

     Programs for Message Switching.

Control of Information Display Systems.

Recording of Status and events.

Information Processing for telecommand and control

2. Secondary Analysis(Operational planning tasks)

           State Estimation

Optimal Power flow

Network Security Analysis

Load Prediction

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Time Decomposition Of Power System Operation

PRE - DISPATCH

DISPATCH

POST - DISPATCH

NETWORK TRAINING

SIMULATOR

10

Application Functions in Pre-Dispatch, Dispatch and Post-Dispatch modes of an EMS.

11

Hierarchical Control in EMS

• Load frequency Control.

• Economic Dispatch.

• Power Exchange with Interconnected utilities.

• Unit commitment.

• Maintenance Scheduling

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AUTOMATIC GENERATION

CONTROL

CONTINGENCY EVALUATION

RESERVE DETERMINATION

BASE DATA

LOAD FORECASTING

FUEL MANAGEMENT

MAINTENANCE SCHEDULING

LOAD FLOW

OPTIMAL

LOAD FLOW

TELEMETERED

INPUTS

AND

IMPROVEMENT

(STATE

ESTIMATION

ON-LINE

POWERFLOW)

ON-LINE OFF-LINE

On line and Off line Functions

13

Application Programs in an Energy Control Centre

14

E,I

NORMAL

E,I

ALERT

E, I

EMERGENCY

E, I

RESTORATIVE

E, I

INEXTERMIS

SECURE

IN-SECURE

SYSTEM INTACT SYSTEM NOT INTACT

Operating States of Power system

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No Operating State E: Equality Constraint

I: Inequality Constraint

1 Normal

2 Alert

3 Emergency

4 In-Extremis

5 Restorative

E

E

E

E

E

I

I

I

I

I

Description of the Operating states

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No Operating State From To

1 Preventive Alert Normal

2 Preventive Emergency Through

Alert

Normal

3 Corrective Emergency Normal

Different Types of Control Action

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Framework for computer aids for decision

making in control centers.

REAL TIME DATE

PREDICTIVE DATA

TOPOLOGICAL

ANALYSIS

STATE ESTIMATION

NETWORK EQUIVALENT

SECURITY ANALYSIS

GENERATION DISPATCH

VOLTAGE AND

REACTIVE OPTIMIZATION

LOAD FOREAST

GENERATION SCHEDULING

INTERACTIVE LOAD FLOW AND SECURITY ANALYSIS

SHORT CIRCUIT CALCULATION

REAL TIME CONTROL EXTENDED REAL TIME CONTROL

18

Applications for Energy Management Systems and Energy trading Systems

INTER-FACE

ENERGY

TRADING SYSTEM (ETS)

ENERGY

MANAGEMENT

SYSTEM

(EMS)

19

Block Diagram of an Integrated EMS

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Open Distributed Systems

Closed System vs. Open System

Closed system software

- Restricted to run on a proprietary platform.

- Data sharing with other computers extremely difficult.

Open System software

No longer relied on the single vendor to supply all the hardware and software for the EMS

- Select the each individual subsystem within the EMS from

different vendors

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Impact of Open Systems in EMS

- Purchase the hardware and software requirements for the

sufficient capacity only

- Incrementally upgrade the system as and when required.

- This helps in reducing the financial burden on the utilities

to change from the closed system to the open system.

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Object Oriented Programming

1. Encapsulation (Data Hiding)

2. Polymorphism (Over Loading)

3. Inheritance (Specialization)

Advantages:

1. Reusability

2. Expandability

3. Portability

Features of OOPS:

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