Market Development Manager-Americas – Renewable Energy & Power Generation
ABB Electrification Products Division
When selecting components for energy storage power control systems, traditional designs are the right choice in some cases. For automatic transfer switches and current monitoring systems, it’s a smart idea to consider today’s smarter digital devices.
When it comes to power control systems (PCS) for energy storage applications, panel builders make a smart move when they rely on certain “dumb” components. For example, you would have a hard time finding a “smart” contactor. Ditto for disconnect switches for isolation. Each of these components performs critical functions, but there really isn’t much advantage to adding intelligence.
When it comes to certain panel devices, though, smart PCS builders know that it’s a smart move to consider smart components. Doing so not only creates more- capable panels, but also smaller, lower-maintenance panels. When it comes to identifying energy storage PCS components that benefit from built-in intelligence, two top contenders are automatic transfer switches (ATS) and current monitoring systems (CMS).
Automatic transfer switches
Renewable-energy-generation installations increasingly include power storage, typically in the form of battery storage systems (BES). The functionality and availability of utility-scale BES have been accompanied by lower system costs, driving more farm operators to incorporate these systems as a way to reduce the variability of their generation. Optimizing the utility of BES requires technology to seamlessly transfer between power sources, the function performed by the ATS.
A smart ATS can automatically sense when it’s time to switch between storage and generation. This can enable the BES to ride through the momentary dips in voltage when a cloud passes over a solar farm or there’s a lull in the breeze blowing over the wind turbines.
While this is the most critical purpose of the ATS, it’s not the only function it can perform. Today’s smart ATS devices incorporate monitors or sensors to ensure the quality of the power being fed to the grid- interconnection point. Voltage, current, and phase can all be monitored and the ATS programmed to respond appropriately when issues are detected.
While most current-generation ATS can be connected to external power-quality sensors, some ATS incorporate these sensors as part of their on-board intelligence. Relying on these all-in-one ATS versions means fewer components. That equates to simpler installation, reduced wiring, and – thanks to fewer connections – fewer potential maintenance needs. And because these multi-function ATS eliminate the number of components, they reduce panel space requirements.
Current monitoring systems
Current monitoring systems (CMS) are another logical place to consider more-intelligent models. They have some significant advantages compared to traditional current transformers (CTs). The typical CT design hasn’t changed much in the decades since this technology was first deployed. The more-recent, more-intelligent designs greatly advance their capabilities and their accuracy.
Some CMS versions available today also feature a design that greatly facilitates installation, whether in new renewable farms or retrofits. For retrofits, this includes the fact that you don’t have to shut down operations, disconnect cables, and then reconnect, which creates huge time and cost savings.
The intelligence built-in to these CMS enables operators to measure direct, alternating, or mixed currents. The higher sensitivity compared to CTs makes it possible to more accurately measure generation performance. Beyond the basic measurement functionality, they can also measure the status of fuses, miniature circuit breakers, surge protection devices, disconnectors, and open- enclosure doors, as well as temperature inside the combiner box. All of that information can be put to good use by operators, enhancing control capabilities and ensuring fewer maintenance surprises.
Hand in hand with the increased intelligence is the ability to transmit the related data to automated control applications and/or operations-center dashboards. These intelligent devices can proactively transmit status messages, alerts, and alarms – enabling corrective action, whether through automated responses or human intervention, prior to serious system problems developing.
The combination of digital capability with communication also enables remote-control functionality, reducing the need to dispatch maintenance or engineering staff to a particular panel or turbine.
Some ATS and CMS devices are now available with Bluetooth® capability. Maintenance and engineering tasks are simplified and made safer by the ability to monitor and capture PCS data without opening the panel and making a physical connection.
Applications in vehicle charging systems
The majority of applications for these smarter devices today are in renewable-energy-generation farms. In the near future, though, there’s little doubt they will also find greatly increased use in commercial- / utility-scale electrical vehicle (EV) charging stations that operate at 10kW and above.
EVs are seen by many industry experts as the solution to the renewable-energy-storage dilemma. Most EVs spend the vast majority of their lives tethered to a charging station. While connected, they represent a large and rapidly growing reservoir of electric-energy storage.
As with solar and wind farms, these charging stations can also be configured, using ATS and CMS technology, to effectively monitor and manage power flows to and from the EVs.
The smart shift to smart devices
Smart components may seem to cost more initially, but that’s not actually the case when considering the total cost of all the functions – and therefore devices – they combine. In addition, there’s the added up-front cost reduction of the smaller PCS enabled by fewer components. The enclosure is often the single-most- costly element of a PCS. Using smaller, smarter devices typically reduces the panel size by 20%.
Even where the total up-front cost of the smart devices is more, the total cost of ownership adds additional savings that almost certainly make them the more economical choice. Renewable-energy farm owners and operators will improve generation efficiency and reliability while reducing maintenance and operation issues. That makes specing smart ATS and CMS in power control systems a smart choice.