As industry tries to do more with less — better product quality, less waste, lower labor costs — the same extends to power generation. Energy providers are trying to increase the amount of power available at the places where it's needed, with fewer people manning the switches.
It's in this capacity that programmable logic controllers (PLCs) are finding increased usage, optimizing the processes that help wind turbines, solar farms and more to produce the most energy with the least amount of resources, explained Terry Watson, account manager for PLC HMI Motion at ABB. Speaking at a session Tuesday morning at ABB Automation & Power World this week in Orlando, Fla., Watson explained how the company's PLCs and other automation components are being used, and how those processes are being optimized.
ABB, for example, is an active supplier in large wind turbines —not the kind you might see at homes or universities, but the 500-ft tall variety that typically requires the most processing. "There's a lot that goes into it that are not part of the smaller packages," Watson said, noting the electrical drive-train package, generators and converters, for example.
The turbines are optimized to provide the most torque and are continually adjusted to remain at a constant speed, Watson noted. With remote I/O monitoring, PLCs provide pitch control and direction control that are updated multiple times a second. "They control turning of the sails for optimal speed and torque," he said. "And it's happening constantly according to the wind speed measurements."
An ABB PLC is typically installed in the nacelle, a touch panel is installed in the tower base, and the two parts communicate by an Ethernet network. While large wind turbines represent a relatively small market for ABB, the scalability and modularity of the solar field make it "a much wider field than you can chase," Watson said.
Where PLCs find particular use is within technologies such as thermo solar systems with a central concentration tower, parabolic collectors and photovoltaic panels that follow the sun — all areas requiring control of either one or two axes.
Fixed PV units on a house, for example, have no need for PLCs. ABB is focused instead on solar farms whose PV panels will tilt to follow the sun as it rises and falls as the day progresses; this is a one-axis tilt. "A two-axis system will give you sun-up/sun-down, but will also tilt according to the season so your rays are perpendicular to the PV panel," Watson said.
There's actually a bit more that goes into it, Watson added, listing the tasks of a PLC in sun-tracking applications:
- Uses algorithms that rely on a real-time clock to control position;
- Calculates the position of the sun independent of weather;
- Calculates safe positioning for specific events;
- Processes control signals for frequency converters, switchgear, motors, etc.;
- Processes data from various sensors (wind speed, etc.);
- Has an HMI for manual positioning;
- Processes the voltage signal coming from the PV cell;
- Reboots after power loss.
Watson also introduced a new series of extreme-condition PLCs from ABB, the AC500-XC. Features include an extended operating temperature of -30 °C to 70 °C; extended immunity to vibration, hazardous gases and salt mist; and operating altitude up to 4,000 m above sea level.