Powersystem Op and Con

8/13/2019 Powersystem Op and Con

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Power System Operation andControl


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Introduction

Hans Christian Oersted discovered electromagnetism in1820

In 1831, Michael Faradays many years of efforts rewarded when hediscovered electromagnetic induction

Later, he invented the first generator and the first dynamo

Today, electric energy technologies have a central role in social and economicdevelopment at all scales

Energy is closely linked to environmental pollution and degradation, toeconomic development and quality of life

Today, we are mostly dependent on nonrenewable fossil fuels that have beenand will continue to be a major cause of pollution and climate change

Finding sustainable alternatives is becoming increasingly urgent

Distributed energy system will no longer leave the end energy users totallydependent on central power station


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Definitions

Electric Capacity is a term that defines the rated continuous load-carryingability, expressed in megawatts (MW) or megavolt-amperes (MVA) ofgeneration, transmission, or other electrical equipment

Electric Energy is the term that defines the generation or use of electric powerby a device over a period of time. It is expressed in kilowatt-hours (kWh),

megawatt-hours (MWh), or gigawatt-hours (GWh)


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Laws

Many states have mandated the use of renewable energy.

The Ohios Alternative Energy Portfolio Standard has recently beenpassed into law.

It requires:

Investor owned utilities obtain 25% of their electricity from renewable

and advanced energy sources by 2025.

A 0.5% set aside has been put in for solar PV energy sources.

Penalties of $450 per MWh for non-compliance with solar benchmarksand $45 per MWh for non-compliance with other benchmarks startingin 2009.

Benchmarks can be met by purchasing Renewable Energy Credits(REC) each equal to 1 MWh of renewable energy.

Purchasers of the product could sell RECs into the REC market.

Their current value is around $37.50 because several states have a$45.00 non-compliance rates. It is expected that solar RECs will sell at

much higher rates because of Ohios $450 per MWh solar non-compliance rate.


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Smart Grid with High Penetration of Renewable EnergySources


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Electric Power System Planned

Operation.

Operational objectives of a power system have been to provide acontinuous quality service with minimum cost to the user. Theseobjectives are:

The term continuous service can be translated to mean secure andreliable service

First Objective: Supplying the energy user with quality service, i.e., atacceptable voltage and frequency

Second Objective: Meeting the first objective with acceptable impact

upon the environment.

Third Objective: Meeting the first and second objectives continuously,i.e., with adequate security and reliability.

Fourth Objective: Meeting the first, second, and third objectives withoptimum economy, i.e., minimum cost to the energy user.


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Integrated Objectives

The direction of the arrows indicates the priority in which the objectivesare implemented

Interrelated objectives of operation of a power system

Economically constrained operation of a power system.


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Planned Operation

The problem of attaining the stated objectives may be described asmanagement of facilities and resources over a specified period of time.

The facilities of a large power system consist of many generating units,transmission lines, transformers, circuit breakers, DC/DC converters &DC/ AC converters which are to scheduled for orderly operation &

maintenance The energy resources of a large power system consist of hydro, nuclear,

fossil power and renewable energy sources such as wind farm,photovoltaic and green energy sources such as fuel cells, combinedpower and heat (CHP) and micro turbines.

These facilities are to be managed and utilized to satisfy load demand ofa power system.

The load demand of a power system is cyclic in nature and has a dailypeak demand over a week period, weekly peak demand over a monthperiod, and monthly peak demand over a year period.

Overall objectives of planned scheduling operation are to manage

facilities and optimize resources for satisfying the peak demand of eachload cycle, such that the total cost of operation is minimized.


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The Twenty Four Hour Load Variation Sampled Every Five Minutes


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The Weekly Load Variation Sampled Hourly


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Task Division

1) Operations planning

2) Operations control

3) Operations accounting

Interrelated tasks of planned scheduling operation


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Task Division

Energy management system and its functions vs. decision time


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Operation Control

The primary functions of operations control are satisfying theinstantaneous load on a second-to-second and minute-to-minute basis.Some of these functions are:

Load Frequency Control

Automatic Generation Control (AGC) Network Topology Determination (NTD)

State Estimation (SE)

On-Line Load Flow

Schedule of Transactions (ST)

Economic Dispatch Calculation (EDC)

Operating Reserve Calculation (ORC)

Load Management System (LMS)


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Operation ControlContd.

Load Frequency Control(LFC). This function is also referred to asgovernor response. As the load demand of the power system increases,the speed of generators will decrease and this will reduce the systemfrequency. Similarly, as system load demand decreases, the speed ofthe system generators would increase and this will increase the system

frequency. The power system frequency control must be maintained forthe power system grid to remain stable. We will discuss this functionlater.

Automatic Generation Control (AGC): The primary objective of AGC is tomatch area generation to area load, i.e., to match the tie-lineinterchanges with the schedules and to control the system frequency.

Network Topology Determination: This function uses the real time database, substation topology and network configuration for determining thenetwork model for real-time steady state analysis. This function isneeded for determining the voltage of the system busses.


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State Estimation: State estimation of a power system is the process ofestimating the power system bus voltages (magnitudes and angles) frommeasurements made in real time on power system grid. The mainfunction of state estimation is to eliminate measurement noise and toreconcile the redundant measurement into a consistent set system

states. Online Load Flow (OLF): This function generally utilizes the output of

network topology, i.e. the real time network model, and the businjections from state estimation for purpose of security monitoring,security analysis and penalty factor calculations. This function performsif then condition to determine the possible system states (voltages) in

face of system outages such loss of a line due to weather condition orsudden loss of a generator.

Schedule of transactions (ST): The schedule of transactions adjusts thescheduled net interchange (tie-line interchanges) of a power system toreflect the summation of all interchange scheduled transactions. That isST computes a table of net scheduled values for use of AGC function.


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Economic Dispatch Calculation: Economic dispatch calculation of a powersystem determines the loading of each generator on a minute-by-minute basisso as to minimize the operating costs.

Operating Reserve Calculation: The objective of operating reserve calculationis to calculate the actual reserve carried by each unit and to check whether or

not there is a sufficient reserve in a system. The operating reserve consists ofspinning reserve (synchronized), non-spinning reserve (non-synchronized), andinterruptible load. The minimum reserve criteria is published by the NorthAmerican Power Systems Interconnection Committee (NAPSIC).

Load Management System: Load management is a process for modifyingelectric power demand patterns into more desirable profiles using smart meters

and real time pricing of power. The services which are required to maintainsystem reliability and meet operating criteria, such services include spinning,non-spinning, replacement reserves, regulation (AGC), voltage control andblack start capability are commonly referred to as ancillary services.


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Interrelated tasks for planned scheduling operation

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