Renewable Energy Automation: How PLC and SCADA Run Solar, Wind and Battery Plants

Renewable energy automation is the control and monitoring layer of solar farms, wind turbines and battery storage: inverter and tracker control, a power plant controller that meets the grid operator's requirements, SCADA that collects data from every device, and substation automation at the grid connection. The skills are PLC, SCADA, networks and power systems.

The work looks different from a factory, but the building blocks are familiar. Controllers read sensors and drive actuators, a SCADA system supervises, and networks connect them. What changes is the scale (hundreds of inverters or dozens of turbines spread over kilometres) and the grid connection, which brings its own rules.

Solar PV plants

A utility-scale solar plant is mostly inverters, and most of its automation is about coordinating them.

• Inverters convert DC from the module strings to AC and report power, energy, voltages, faults and their own status. The plant SCADA polls each one.
• String and combiner monitoring measures current per string or group, so a failed string or blown fuse shows up as a gap against its neighbours.
• Trackers, on plants that use them, turn rows of modules to follow the sun. A single-axis tracker controller calculates the sun's position from time and location, uses backtracking to stop rows shading each other when the sun is low, and moves to a safe stow position in high wind.
• The meteorological station measures irradiance in the plane of the modules, module and air temperature, and wind. These are the reference for judging performance, commonly expressed as a performance ratio; IEC 61724-1 covers PV performance monitoring.
• The power plant controller (PPC) is the brain at the grid connection. It measures at the point of connection and sends setpoints to the inverters so the whole plant follows the grid operator's instructions for active power, reactive power, power factor or voltage.

Wind turbines and parks

Each turbine has its own controller that manages pitch (blade angle, to control power and to stop the rotor), yaw (turning the nacelle into the wind), the generator and converter, and many protective functions. The park SCADA collects data from every turbine, typically as ten-minute statistics plus events and alarms, and passes commands such as curtailment from a park-level controller. IEC 61400-25 extends the IEC 61850 approach to communication with wind power plants, though vendor-specific interfaces are still common.

Battery energy storage

In this lesson by Circuit Masterclass, from our free Battery Energy Storage Systems course, a BESS is explained part by part: its layout, the PCS, EMS and BMS, and its working principle. The three control layers below are the ones it introduces.

A battery system has three control layers. The battery management system (BMS) protects the cells, watching voltage, temperature and state of charge and disconnecting if limits are exceeded. The power conversion system is the bidirectional inverter. The energy management system (EMS) decides when to charge and discharge: for frequency response, shifting solar output into the evening, or reducing a site's peak demand. Around them sit safety systems for fire detection and suppression, and the HVAC that keeps the batteries within temperature.

The communication stack

Two protocols from the utility world are worth learning early. [IEC 61850](https://webstore.iec.ch/en/publication/6028) defines how substation protection relays and controllers model their data and communicate, including GOOSE messages for fast peer-to-peer signals such as trips and interlocks. IEC 60870-5-104 and [DNP3](https://www.dnp.org/About/Overview-of-DNP3-Protocol) are common for telecontrol links to grid operators and control centres, with the choice depending on the country and utility. On the plant side, many inverters implement SunSpec information models over Modbus, which gives devices from different makers a common register layout.

Grid codes

Every grid operator publishes rules a generating plant must meet to connect: how it behaves during voltage dips (fault ride-through), how much reactive power it provides, how it responds to frequency changes and how fast it ramps. In the United States, IEEE 1547 sets interconnection requirements for distributed energy resources. The details differ from country to country, and the power plant controller is where the automation engineer implements them. Compliance tests at commissioning prove the plant meets them.

What the controls work looks like

Renewables automation jobs fall into a few recognisable kinds of work, and most of them are familiar to anyone who has commissioned a process plant.

• Commissioning. Checking every inverter, tracker controller and meter communicates, that each value arrives with the right scaling and units, and that commands from SCADA reach the right device. On a large solar plant this is hundreds of near-identical devices, so a disciplined point-by-point checklist matters more than cleverness.
• Power plant controller testing. Stepping setpoints for active power, reactive power and voltage and recording how quickly and accurately the plant responds, often witnessed by the grid operator.
• SCADA and data. Building screens, alarms and reports, and making sure data reaches the owner, the operations team and any monitoring platform with correct time stamps. The SCADA training guide covers that layer in depth.
• Operations support. Finding why one string, inverter or turbine produces less than its neighbours, which is mostly careful comparison of data against the meteorological reference.
• Security. Plants are often remote and reached over the internet, so secure remote access and segmentation are part of the design, not an add-on; see OT cybersecurity and IEC 62443.

Much of the effort goes into consistency: naming conventions, tag structures and templates that make the thousandth device behave exactly like the first.

A learning route

If you already work with PLCs in manufacturing, you have the first three steps. The new material is power: single-line diagrams, protection, short-circuit levels and how a substation is automated. If you come from electrical engineering, start with the PLC and network steps. Free PLC basics are on our free PLC courses page, and our guide to free SCADA courses with certificate covers the supervision layer.

Free courses for renewable energy automation

• PVsyst Solar Power Plant Design: meteo data, string sizing against the inverter's MPPT window, shading, the loss model and the simulation report.
• Industrial Communication: serial, Modbus, PROFINET, EtherNet/IP and OPC UA, with hands-on configuration.
• ETAP Power System Analysis: load flow, short circuit, protection coordination and arc flash.
• IEC 61850 Substation Automation: the object model, SCL files, GOOSE and IEC 60870-5, for engineers who already work with relays and SCADA.

The power systems engineer path puts related courses in order. Every course is free in full, with credited video lessons, notes, practice tasks and one final assessment; no card is needed.

The optional EDWartens Certificate of Completion is a small one-off fee that follows the course level, so the advanced IEC 61850 course costs a little more than these intermediate ones. Anyone can check it at edwartens.com/verification. It is not a vendor, IEC or grid-operator qualification and is not accredited. Create a free account to start.

Take the free course

Free

Renewable energy · Intermediate · Free

PVsyst Solar Power Plant Design

Free

Industrial networks · Intermediate · Free

Industrial Communication: Serial, Fieldbus, Ethernet, Modbus, PROFINET and OPC UA

Free

Electrical · Intermediate · Free

ETAP Power System Analysis: Load Flow, Short Circuit, Protection, Arc Flash and Stability

Free

Power systems · Advanced · Free

IEC 61850 Substation Automation: GOOSE, SCL and IEC 60870-5