Safety Instrumented Systems / Systems Integration / Power Supplies

Power Supplies Take Sophisticated Paths

Using Many of the Same Data Processing Tools and Software as Process Controllers, Power Supplies Are Diversifying Their Capabilities and Serving in Many New and Different Applications

By Jim Montague

We've gone way beyond "on" and "off." Yes, power supplies always had to convert and deliver appropriate volts, watts, amps and other power levels, and meet quality measures to run their machines and applications. But once configuration was done and harmonics were tested, most power supplies operated continuously—at least until an interruption or outage happened. 

Well, those set-it-and-forget-it days are long gone. Digital monitoring devices enabled by microprocessors and software are pulling power supplies up to the same awareness level as so many other process control components.

For instance, Boliden recently spent $790 million to renovate its Aitik open-pit copper mine in Gällivare, Sweden, and it used ABB's control systems and power equipment to increase Aitik's efficiency and double capacity to 36 million tons of ore per year, even though its initial ore is only 0.25% copper (Figure 1). The mine installed 650 motors ranging from 4 kilowatts (kW) to 5 megawatts (MW); 230 drives and variable-speed drives; and two 22.5-MW gearless mill drives (GMDs). These are powered by ABB's 23 distribution transformers and gas-insulated switchgear and controlled by its System 800xA DCS.

Of course, extracting metal from the 106,000 tons of ore that's crushed and chemically concentrated to 25% copper at Aitik each day requires lots of stable, high-quality power for its 7 km of conveyors, the GMDs and other equipment, which must often run 24/7/365 in very dusty conditions that can get down to -45 °C in winter. So, ABB implemented a 179-kV substation with its gas-insulated UniGear switchgear that's protected by its Relion relay protection equipment, and distributes 24-kV power throughout the mine's operations. Also, a harmonic filter and power-factor correction system help Boliden prevent damage to its own equipment and avoid disturbing the local power grid.

In addition, Aitik uses the IEC 61850 standard that defines communications within and between electrical components, which enables 800xA to provide one environment for supervising and controlling process automation equipment, power automation devices, switchgear, and transmission and distribution equipment. Boliden reports that integrating Aitik's electrical controls with its process controls increases productivity and reduces stoppages.

Custom-Made Monitoring

While most process applications aren't as big as the Aitik mine, many similar methods of monitoring and proactively maintaining electricity are being adopted by smaller power supplies in diverse applications.

"Power supplies have always been a bit of a stepchild compared to other process control devices, but users in applications from power generation to food and beverage are recognizing that power is the most critical element in their applications," says Roolf Wessels, business unit manager for monitoring and protection at Pepperl+Fuchs. "You can lose a few I/O points and networking nodes and still run an application, but losing power means losing your whole application, so it's worthwhile investing in high-reliability, high-efficiency power. As a result, users want more diagnostics in their power supplies. They already have diagnostics for predictive maintenance and asset management in their controllers and field devices, and now they want it in their power supplies, too."

As a result, Pepperl+Fuchs redesigned its PS 3500 power supply in 2009, and is scheduled to introduce its PS 3500-DM diagnostic module in January 2013. "It plugs into the power supply's backplane and monitors incoming current quality and generated dc outputs, checks for brownouts and spikes, time-stamps any events, correlates them with data from other sources, and provides alerts and alarms," says Wessels. "We even added a display on the DM module itself, so users see all their parameters locally too." 

Similarly, Emerson Network Power is integrating its uninterruptible power supplies (UPSs) with Asset Management Suite (AMS) software to monitor UPS performance. "In many cases, power systems and their backups have been reliable for decades, so users tend to forget about them after commissioning, and no longer know what to do when alerts and emergency calls eventually come in," says David Vasselin, market and business development vice president for Emerson Network Power's industrial systems division. "Now users want UPSs that are easier to understand and maintain, and this is why we've integrated them with AMS in electronic device description (EDD) software and human-centered design principles. We ran through all the UPS alert situations and added them to the EDDs to give users a hierarchy of alerts and how to troubleshoot them."

Standard Pieces for Specific Puzzles

To help reduce the time it takes to integrate power supplies with their control-based counterparts, Mark Wilkins, chief engineer at Acopian, reports his company is building IP addresses, Ethernet and USB interfaces and some control functions directly into its 0-30 kV power supplies "There's a lot more fluctuating inputs these days, typically between 90 V and 265 V, so we designed a universal input to handle them without having to flip a switch," says Wilkins. "In general, we now have more programming and communications options for applying power more efficiently, and these are allowing power supplies to interface with other equipment, talk to each other and synchronize efforts. For example, in a water ionizing application to purify water for plating, a controller can tell a power supply to turn on; it can report back in a few hundred milliseconds; and be adjusted much faster than manually for more consistent plating with less feathering."     

Likewise, some power supplies are adding intelligence that allows them to be more easily monitored and managed, according to Kai-Uwe Bronzel, product consultant for U.S. power supplies and power security at Siemens Industry. "We recently built a relay contactor module into our Sitop power supplies that can bring a signal back to upper-level control systems," says Bronzel. "This lets users check on their input and output voltages, observe trends in their 24-Vdc supplies, and prevent more interruptions and potential failures."

Sharonda Wamer, Siemens' product marketing manager for U.S. power supplies and power security, adds that many power supplies and related systems are following the lead of Europe's suppliers, and moving from 230 Vac or 120 Vac to 24 Vdc. "More customers have applications that depend on critical 24 Vdc power, so we provide solutions to maintain it," says Wamer. "These include our 'dc ups' with battery backup, redundant solutions with two power supplies for load sharing, and switched-mode power supplies. These use an electronic method that draws less current than regular mechanical supplies when reacting to short circuits, and this means fewer trips, more and better identification of potential overloads, and fewer lost circuits." 

Merging Power and Control

To combine control and power even more tightly, National Instruments and the National Renewable Energy Lab have combined NI's single-board Reconfigurable I/O (RIO) and added its standard General Purpose Inverter Controller (GPIC) board for 50-kW and up power supplies, which primarily use custom circuit boards.

In fact, Dynapower Corp. has developed power converters for grid-tied energy storage based on NI's LabView RIO architecture and RIO GPIC (Figure 2). Advanced carbon batteries are useful for grid storage because they have a long lifecycle, fast charge/discharge and deep-cycling capability, but they require a unique power conversion and inverter system such as Dynapower's to stabilize performance and provide these benefits.

"LabView and GPIC development platforms reduced our development cost and risk compared to a full-custom controller design," says Kyle Clark, Dynapower's advanced systems engineering manager. "We were able to reduce development time for our power converters from 72 weeks to 24 weeks. FPGA devices in particular, which now include embedded DSP cores inside the fabric, are a real game changer. We can precisely control the flow of power, run multiple control loops in parallel and reconfigure the hardware at a silicon level even after it's deployed to the grid."