Energy Management System
*Energy Management System*
Introduction: Electrical Energy
Management System (EEMS) widely refers to a computer system which is designed
specifically for the automated control and monitoring of electric power and
utility system. The scope may span from a load dispatch center to a group of
power networks. Most of these energy management systems also provide decision
making facilities for operator in the operation and control in real time. The
data obtained from such actions are used to train operators in a control center
and for performing engineering studies for futuristic actions like planning,
optimization and maintenance scheduling, etc. on a frequent basis and to
produce trend analysis and annual consumption forecasts.
Energy Management System (EMS) is a collection of computerized
tools used to monitor, control, and optimize the performance of generation and
transmission systems. This intelligent energy management software control
system is designed to reduce energy consumption, improve the utilization of the
system, increase reliability, and predict electrical system performance as well
as optimize energy usage to reduce cost. Energy Management System applications
use real-time data such as frequency, actual generation, tie-line load flows,
and plant units’ controller status to provide system changes. Energy Management
System had its origin in the need for electric utility companies to operate
their generators as economically as possible. To operate the system as
economically as possible required that the characteristics of all generating
units be available in one location so that the most efficient units could be
dispatched properly along with the less efficient. In addition, there was a
requirement that the on/off scheduling of generating units be done in an
efficient manner as well. Energy management systems can also provide metering,
sub metering, and monitoring functions that allow facility and building
managers to gather data and insight that allows them to make more informed decisions about energy activities across
their sites.
1.1 EMS
in Power Systems:
Electrical energy management systems (EMS) are an important
function for the reliable and efficient operation of power systems. EMS is
related to the real time monitoring, operation and control of a power system.
The information from the power system is read through Remote Terminal Units
(RTUs), an integral part of SCADA to an EMS or Energy Control Centre (ECC). EMS
consists of both hardware and software. Hardware part of EMS consists of RTU,
Intelligent Electronic Device (IED), Protection, Computer networking, .etc.
Software part of EMS consists of Application programs for network analysis of
power systems. In EMS, application programs are run in a real time as well as
extended real time environment to keep the power system in a secure operating
state. Now-days, EMS is an integral part of any power system. It is used as a
part of Substation Automation System (SAS), Demand Side Management (DSM),
Protection, and Distribution Management Systems (DMS) for renewable energy and
so-on. In the next few years, EMS-DMA will change the role of power systems,
monitoring and control.
An energy management system (EMS) is a system of computer-aided
tools used by operators of electric utility grids to monitor, control, and
optimize the performance of the generation and/or transmission system. The
monitor and control functions are known as Supervisory Control and Data
Acquisition (SCADA), followed by several on-line application functions. Energy
Management Software (EMS) is a general term referring to a variety of
energy-related software applications which may provide utility bill tracking,
real-time metering and lighting control systems, building simulation and
modeling, carbon and sustainability reporting , demand response, and/or energy
audits. Managing energy can require a system of systems approach.
1.2 Objectives:
There are primary and secondary objectives of energy management
system. The primary objectives are related to the security and stability of the
system, while the secondary objectives relate to the
Primary Objectives: Security and Stability of the system
Secondary Objectives: Economic Operation and Control
Tertiary Objectives: Optimization, Operational Planning and
Maintenance Scheduling 1.2.1 Primary Objectives:
1. Maintaining the power system in a secure and stable operating
state by continuously monitoring the power flowing in the lines and voltage
magnitudes at the buses.
2. Maintaining the frequency within allowable limits.
3. Maintaining the tie-line power close to the scheduled values.
1.2.2 Secondary Objectives:
1. Economic
Operation of the power systems through real time dispatch and Control.
2. Optimal
control of the power system using both preventive and corrective control
actions.
3. Real time
Economic Dispatch through real power and reactive power control
1.2.3 Tertiary Objectives:
1.
Optimization of the power system for normal and abnormal operating scenarios.
2. Optimal
control of the power system by appropriate using both preventive and corrective
control actions
3. Maintenance
scheduling of generation and transmission systems.
The three objectives are executed at different levels by the
operator in a control Centre. While the first objective is automatic or closed
loop control without the intervention of the operator, the secondary and
tertiary are performed with the aid of the operator.
In energy management systems, voltage magnitudes and power flows
over the lines are continuously monitored through SCADA, to check for
violations. The violations in voltage are addressed by preventive control
actions, while the power flow violations are addressed by means of corrective
actions. The tie line power flows at scheduled values will be maintained by
adjusting the MW outputs of the AGC generators so as to accommodate fluctuating
load demands.
The energy management software application will also calculate the
required parameters to optimize the operation of the generation units under
energy management action. EMS is a computer-based Operation and Control System.
It is used in mentoring and controlling the system in real time. It receives
large amount of information from power Systems through SCADA. It selectively
uses Information from SCADA for computation and analysis. It Send back
‘important control signals’ to the System through SCADA.
EMS has different names, namely 1) ECC: Energy Control Centre, 2)
Load Dispatch Centre, 3) DSM: Demand side Management, 4) DMS: Distribution Management
System, etc. The main functions of these are to operate the power systems in
real time.
2. Evolution of EMS:
The evolution of EMS has a long past. It has started with control
centers in 1960s to fully developed energy management systems
1960 – Termed as Control Centre’s (CC)
These control centers were initially termed a load dispatch centers.
The important task was to control the power generation and load demand as to
match the generation with load demand. Even today, the term load dispatch
Centre’s are widely used in various state electricity boards as well as energy
control Centre’s.
1970 – Energy Control Centre’s.
Here the main task was to control the energy rather than the power.
Here energy monitoring is of main concern the matching of energy of power
demand from that of power generation is of main concern.
1990 – Energy Management Systems (EMS)
In EMS, the main task was to manage the energy through various techniques like load management (LM), demand side management (DSM), distribution management systems (DMS). EMS are computer based programs hat perform both computational tasks as well as decision making tasks so as to assist the operator for real time operation and control.
Evolution of SCADA:
The
evolution of SCADA started with monitoring and data acquisition systems plants
followed by control. These have been used prior to EMS. The main tasks of SCADA
were to continuously measure and monitor parameters for checking limit
violations and to ensure reliable and safe operation of the system being
controlled. The earlier tasks of SCADA were mostly monitoring with gradual
control tasks coming into picture.
It
becomes more beneficial when EMS and SCADA are used together
3. Functions and Benefits of EMS:
The
important benefits of an EMS can be addresses as the following functions:
Control functions:
1. Real
time monitoring and control functions.
2.
Automatic Control and automation of a power system like Automated interfaces
and electronic tagging
3.
Efficient automatic generation control and load frequency control.
4.
Optimal automatic generation control across multiple areas
5. Tie
-line control.
Operating functions
1.
Economic and optimal Operation of the generating system.
2.
Efficient operator Decision Making Improved quality of supply
Optimization functions
1.
Optimal utilization of the transmission network
2. Power
scheduling interchange between areas.
3.
Optimal allocation of resources
4.
Immediate overview of the power generation, interchanges and reserves
Planning functions
1.
Improved quality of supply and system reliability
2. Forecasting
of loads and load patterns
3.
Generation scheduling based on load forecast and trading schedules
4.
Maintaining reserves and committed transactions
5.
Calculation of fuel consumption, production costs and emissions
4. EMS Architecture:
Figure 1.1 shows the main
important entities of power systems, EMS and SCADA. EMS and SCADA are two
important entities in the real time monitoring, operation control of power
systems. The flow of Power and information between the three modules can be
observed. While Power (unidirectional) flows from Power Systems through SCADA
to EMS. Information flow (bi directional) SCADA forms the interface between
Power Systems and EMS. The power system data, both continuous and discrete, is
collected by SCADA and selectively sent to the EMS. EMS is a computerized
control of power systems consisting of several application programs which are
run / executed by the operator so as to maintain the power system in a secure
and table operating state. EMS consists of several programs interconnected in a
particular fashion so as to obtain the solution in real time.
Figure 1.2
Shows
the components in EMS-SCADA. Power Systems contain generators, transformers,
transmission lines, different loads to industry and consumers. SCADA consists
mostly of hardware components, which measure the quantities (Voltage, current,
power, etc.) from various meters. SCADA consists of collection of information
from meters distributed throughout the area through Remote Terminal Units
(RTUS).
5. Practical EMS
Figure 1.4
Shows the actual implementation of Power System Model, SCADA AND
EMS in a laboratory environment. The power system model consists of scaled down
components of three phase generators, transformers, transmission lines and
loads. The SCADA modules consist essentially of hardware for measurement
monitoring, control and protection of the power systems. SCADA monitors
information from the power system through PT, CT, etc., collects data and sends
them to the EMS. Both Analog (continuous) data and digital (discrete)
information are collected by the Remote Terminal Units (RTU). EMS consists of a
network of computers or work stations which perform computational tasks for
decision making in real time operation and control.
Both On-line and Off-Line
functions can be performed in an EMS. The operators in an EMS send signals to
the power system through SCADA. On line functions include mainly closed loop
control functions like automatic generating control (AGC), load frequency control
(LFC), voltage reactive power control (volt-var control). Open loop functions
like Economic Dispatch and Operator load flow, state estimation, security
assessment, etc. are also performed in real time as on line functions.
6. Working of EMS:
The important working of an EMS is given below
1. Real time monitoring and control over the whole distribution
network.
2. Enhanced customer service through a complete outage management
package including trouble call taking, fault localization and restoration as
well as outage statistics and customer notification.
3. Efficient work order handling via the built-in work management
tools.
4. Better crew and resource management including support for crew
scheduling and tracking, dispatching and assignments as well as follow-up and
reports.
5. Optimal network utilization using the State Estimator
functionality for optimal feeder reconfiguration and loss minimization in
balanced networks
6. Better support for all reporting with retrieval of historical
data archived in a data warehouse
Summary: