Supervisory Control and Data Acquisition (SCADA) systems have been facilitating industrial automation for decades now. The term “SCADA” was coined in the early 1970s. Over the period, SCADA revolutionized industrial automation resulting in increased productivity through efficient and optimized utilization of available resources. A SCADA system is also widely used in a power system to collect, analyze, and observe the power system’s data effectively. As the power system is transitioning to renewable energy sources, especially Inverter Based Resources (IBRs) like PV-Solar, SCADA systems provide monitoring and control capabilities in many of these areas.
Variability of renewable energy resources like PV-Solar, due to dependence on climatic conditions, diminishes their reliability as the only source of energy. R&D triggered by these limitations prompted use of energy storage system (ESS) especially BESS to increase the reliability and efficiency of such systems. Achieving operational efficiency has become a challenge due to the increased size of renewable power plants (PV-Solar/PV-Solar+BESS/BESS only) and has added complexity of ESS (BESS). SCADA systems provide flexibility in controlling and monitoring different plant components including inverters, trackers, circuit breakers, substations, and meters. It also facilitates plant performance assessment based on data collected from meteorological stations and other field devices.
The U.S. Energy Information Administration (EIA) considers a power plant to be ‘utility scale’ if its total generation capacity is 1 megawatt (MW) or greater. There are currently over 10,000 solar photovoltaic (PV) plants that meet this definition.
SCADA systems used for Inverter Based Resource (IBRs) are centralized systems capable of monitoring and controlling various IEDs at power plants, meteorological stations, and substations. A SCADA system for PV-Solar power plants is expected to facilitate Data acquisition, processing, control, and display.
A typical on-site SCADA system in context with a PV-Solar power plant may consist of the following three main parts:
- SCADA Rack with Power Plant Controller for PV plant and Substation.
- Field network for communication with field devices.
- Meteorological station(s) to measure the amount of solar radiation reaching the surface of the PV modules.
At Nor-Cal Controls, many customers inquire about the full capability of our typical SCADA build, with questions ranging from the ability to control various IEDs onsite, to our capacity for storing historical data.
Typically, a SCADA Rack for a PV-Solar power plant may consist of:
- SCADA/Historian Servers with required SCADA/Historian software: Redundancy can be applied based on project size and requirements.
- HMI/User Interface with custom plant-specific displays and alarm notification software.
- Firewalls: To isolate the plant from the outside world, route internal traffic, provide remote access and maintain cybersecurity compliance. Redundancy here can also be applied based on project size/requirements.
- Power Plant Controller (PPC)/Energy Management System (EMS)/Master Plant Controller (MPC) with required software: Redundancy can be applied based on project size and requirements. The PPC/EMS/MPC is responsible for monitoring plant output at the POI and issuing commands to generator resources (Inverters) and substation IEDs to ensure the plant complies with interconnection requirements.
- Substation Data concentrator: Interface for Substation Data points (provided by Substation SCADA integrator).
- Root switches: Layer 2/3 network switches facilitating connectivity of field and substation devices to the SCADA Rack.
- Data Concentrator: Facilitates protocol conversion for communication between field devices, PPC and SCADA Rack.
- UPS equipped with a battery for power backup for the SCADA Rack
SCADA rack configuration may vary based on the site-specific services, redundancy and/or for meeting owner and AHJ requirements.
Successful operation of PV-Solar power plants greatly depend on reliable communication between the SCADA rack and field devices. Field network communication is typically achieved via field network communication enclosures at every skid/power block in the field, connected by a fiber optic network. A typical field network enclosure (FNE) will consist of:
- Managed network switches
- Patch panels for fiber optic interface
- IO modules for MV transformer monitoring
- UPS with battery for power backup
Meteorological (MET) stations provide quality meteorological data that can help measure the amount of solar radiation reaching the surface of the PV modules. Quality meteorological data helps in measuring the efficiency and performance of PV-Solar plants. Real-time data helps operators to monitor any fluctuations in power generation and schedule O&M activities to improve energy output and ROI. MET station may include:
- MET tower along with requisite hardware
- MET enclosure with:
- Data logger
- UPS with battery backup and solar panel backup.
- MET sensors like POA, GHI, Albedometer, Soiling stations etc.
The quantity of MET stations and selection of MET sensors is determined based on the capacity and geographical spread of the site.
There is no one size fit all SCADA system for PV-Solar/BESS power plants. SCADA systems enable monitoring and control of the substation devices, PV/BESS inverters and meteorological stations. They help to automate the control of power generation and synchronization of power output to meet POI requirements. They facilitate historizing of all charge/discharge logs to meet ITC/PTC requirements and provide alarms and notifications for performance analysis. They are designed to allow for the PPC/EMS/MPC to be taken off-line for short intervals for maintenance or configuration changes without disrupting generation. The PPC/EMS/MPC can receive real power setpoints from multiple sources including ISO, local HMI, or the owner’s control center.
As the PV-Solar and BESS project requirements are evolving, it’s fair to say that the ideal SCADA system for PV-Solar plants with and without BESS is a dynamic system and needs custom logic and control schemes based on the specific project and AHJ requirements. Nor-Cal Controls has the capability to meet the dynamic and evolving SCADA system requirements of your existing or upcoming PV-Solar/PV-Solar + BESS/BESS only projects.
Collaborator: Nate Kelleher