Table of Contents

Active vs Passive SCADA

Supervisory Control and Data Acquisition (SCADA) functionality is separated into two general categories: ‘active’ and ‘passive’. Both active and passive SCADA utilize ‘commands’, sent from the SCADA system, to connected equipment for the purpose of controlling the connected equipments’ behavior. The ability to ‘control’ the connected equipment, verses data acquisition (or monitoring) only is the key differentiator between a data acquisition system (DAS) and SCADA system.

• Active Control When equipment operates automatically, in response to changing conditions and operating parameters, these automated actions are referred to as ‘active’ SCADA functions.

Common Examples: - Tracking solar rows that follow the Sun’s position based on an algorithm automatically. - Increasing the output of Inverter-A to compensate for a cloud passing over the solar array associated with Inverter-B so that the aggregate power of both inverters maintains a steady output level automatically. - Charge or discharge a battery to firm the exported power while a solar array’s output is declining as the Sun is setting automatically.

• Passive Control Unlike automated operations, many equipment behaviors are modified through discrete actions triggered by an Operator’s command. An Operator sending discrete commands, and the resulting equipment responding to those commands, are referred to as ‘passive’ SCADA functions.

Common Examples: - TRIP, Reset, or CLOSE a breaker remotely - Clear an Inverter fault remotely - Change a tracker from manual-stow to automatic-tracking remotely

PPC vs EMS

Power Plant Controllers (PPCs) and Energy Management Systems (EMSs) are terms for very similar active control SCADA systems that are differentiated by their specific applications and functions. Both sets of EMS and PPC functionality are accomplished with specialized computing platforms that are dedicated to providing high-reliability automation control at program scan rates that analyze and respond to system conditions multiple times per electrical cycle (16.7ms/cycle).

These ‘controllers’ are often separate from the actual SCADA system, ensuring the automation control processing is executed by dedicated hardware and without interruptions from extraneous user interactions, graphics processing, data logging, or security verifications.

In contrast, the SCADA system performs higher level security, graphical display, alarming , and trending functions … allowing Operators to modify settings that control the behavior of the ‘controller’.

For example, when an operator sends a command to a ‘controller’ that changes a solar plant’s export limit from 5,000 kW to 3,000 kW, the command is entered in the SCADA’s HMI, logged, and sent to the ‘controller’. The ‘controller’ receives the command and then actively manages the decreased generation at a pre-determined ramp rate until the new set-point is met.

• Power Plant Controller (PPC) Typically used when a generator is used to provide grid services or manage power quality by providing real-time adjustments via voltage and frequency regulation.

Transmission interconnected generators (of all types) are commonly associated with requiring PPC functionality to support grid operations by operating within specific voltage ranges, and help stabilize the grid by bucking or boosting voltage via reactive power manipulation.

While the generator’s operation is automated by the same type of ‘controller’ as an EMS, the power management functionality required is different.

• Energy Management System (EMS) Typically used when there are multiple generation sources that need to be coordinated (like a microgrid) or when there is a scheduling aspect to the automation control’s behavior over time.

Energy storage is commonly associated with requiring EMS functionality to support charge and discharge schedules based on economic demand targets, hourly time-of-use rates, or weekday/weekend/holiday rules associated with the battery’s operation.

While the battery’s operation is automated by the same type of ‘controller’ as a PPC, the scheduling functionality required is different.

FOCUS vs Acuity vs Acuity-PPC

The plethora of terms {DAS, SCADA, passive, active, EMS, and PPC) can become confusing, and customers often have difficulty selecting solution is appropriate for what situation.

Aderis Energy has developed products that help simplify the selection of products and functionality that ensures customers have access to a broad set of functionality when they require it, without the need for re-engineering or large investment should their initial requirements change in the future.