November, 2007
Winds of Change - Using OPC in Guaranteed Data Delivery for Wind Farms by
Eric Murphy
High oil prices and global warming concerns have
more people looking at renewable energy sources
such as wind power. Wind power installations
have unique challenges of diverse locations of
multiple generating stations. OPC can provide
continuous access to real-time information needed
for equipment monitoring and making production
decisions.
Harness the Wind
People have harnessed the wind for energy for
thousands of years, and technology has been
steadily reinvented and improved. The cost of
energy production is continually decreasing as
strides are made in material usage, rotor design
and turbine technology. This gives wind power
more competitive footing with conventional fossil
fuel based energy sources. Successful integration
of renewable energy into utility portfolios is
increasing, yet owners and operators still face
many business challenges. Optimizing operations,
effective maintenance and increasing the accuracy
and timeliness of decisions all affect the bottom
line. Not to mention issues like utility integration,
accurate data analysis and forecasting and
scheduling energy output. All these business
aspects require reliable real time data for making
effective decisions.
Wind power is converted to electricity by a wind
turbine. A wind farm consists of multiple wind
turbines in the same location, although the may not
all come from the same vendor. In addition to data
from multiple generating turbines, information is
needed about the substations and utilities, as well
as key meteorological data. Wind farm systems
may contain up to hundreds of windmills, covering
long distances and harsh environments. Users
need a reliable communication network capable of
providing standardized information monitoring and
centralized control and data storage.
The Answer is Blowing in the Wind
OPC can provide real time data access for remote
supervision, control, and data acquisition required
for operation and maintenance. It also is a means
of standardized communication among energy
management centers and regulatory bodies.
High resolution data is essential for optimizing
wind farm assets and realizing incremental gains
critical to improving the bottom line. OPC not only
overcomes the challenges of gathering data from
various sources into a centralized repository, but
also ensuring guaranteed deliver of the data, even
if it spans different manufacturers, technological
generations or geographical locations.
OPC enables interoperability between disparate
control systems, condition monitoring and
production management systems. OPC DA provides
plug-and-play connectivity between the various
wind farm data sources. The OPC specification
ensures that regardless of the underlying system
and the product vendor, the interfaces will connect
and exchange data in the same way. MatrikonOPC
has OPC DA enabled products available for common turbines protocols such as Modbus. OPC servers
are also available for common wind farm SCADA
platforms such as Rockwell Allen-Bradley, Siemens
and GE Fanuc.
For connectivity with common electrical utility
protocols like DNP 3.0 and IEC 60870-5,
MatrikonOPC offers full telemetry grade OPC servers
that include redundant communication channel
support.
Changing Winds and Constant Data
Historized data from the wind farms is used for
many functions including efficiency improvements,
statistical process control, quality assurance and
reporting. Storing the real time process data allows
wind companies to create genealogical records of
processes, track equipment conditions and better
forecast and schedule energy production.
Reliance on this critical data means it is becoming
increasingly important to guarantee that all data
from an OPC server is accurately recorded in
history. Some method is needed to ensure data is
not lost or corrupted during times of communication
loss between the historian and the OPC server.
Most ‘home grown’ or ad-hoc systems involves
a proprietary data collection
format that begins buffering data
to a custom binary file in the
event communication is lost with
the historian.
Although these
systems do the job, they have
several disadvantages over a
standard OPC HDA architecture;
1. The solutions are proprietary
to the historian manufacturer.
This makes it difficult to
standardize on a single
architecture for multiple wind
farms.
2. The interim stored data
is usually in a proprietary,
inaccessible format. Applications
must wait for communications to
the historian to be restored and
the buffer emptied before the
critical data can be accessed.
3. The solutions have not been
designed for redundant systems.
The OPC HDA (Historical Data Access) specification
standardizes on how historical data is transferred.
A guaranteed data delivery architecture using the
OPC HDA capabilities of an OPC historian as the
storage mechanism at the source offers several
advantages;
1. Configuration options on the size of the historical
data buffer.
2. Standard, at the source, access to historical
data, even during times of communication loss to
the central historian.
3. Increased flexibility on how and when the data
is backfilled to the historian.
Since OPC is a client/server model, users have
several options of which architecture best suits their
needs for retrieving the buffered data. One method
has an OPC HDA client read the history from an
OPC based data buffer and ‘push’ or write the data
into a central historian. This approach offers several
benefits.
Any compliant product that follows the OPC HDA
standard provides an architecture that can easily
be duplicated to create a redundant solution. OPC
HDA clients may also make use of the standard OPC
HDA Insert Replace functionality to ensure no data
is missed yet no duplication occurs in the historian
repository.
In addition, when deployed in a redundant mode,
a well written OPC transfer client could continually
synchronize transaction records to ensure no
data is lost. The MatrikonOPC
History Link is an example of
an OPC HDA client that employs
such guaranteed data delivery
functions (see Figure 2).
Reaping the Wind
OPC provides the means
to manage wind farms in
a standardized fashion by
providing applications with
real-time data and critical
information on each point in
the system. Most of the wind
industry is using the proprietary
or homegrown types of
applications.
Standardizing access with OPC
supplies a better way to manage
wind performance and control
assets. OPC products that gather high-resolution,
real-time data gives the end user far more
capability to analyze and affect the operation of
the wind farm, than the currently used technology.
Using OPC HDA technology guarantees the data is
always available, regardless of how hard the wind
is blowing. The way the blows may continually
change, but the need for real time data to manage
energy production systems, and the ability of OPC
to provide it is constant.
Eric Murphy is Advanced Architecture System Design Engineer, MatrikonOPC.
Eric Murphy,BSc, PEng (Alberta), Eric is a Chemical Engineer with a Process Control specialization and an OPC expert. Eric has been a part of the OPC community since its early beginnings in the mid-1990s. Eric is heavily involved with the OPC Foundation and currently acts as the chair for the OPC Historical Data Access (HDA) working group. Eric is also a member of the OPC Technical Steering Committee (TSC) and an active member of the OPC Unified Architecture (UA) working group.
Eric's Contact Information
