Real-Time Innovations and Microgrids: RTI Connext DDS in Energy

RTI Connext DDS and Microgrids: How Real-Time Middleware Transforms the Energy Sector

The transition from centralized power systems to distributed microgrids demands a fundamentally new approach to data exchange between equipment. Traditional SCADA protocols cannot provide millisecond-level synchronization between solar inverters, battery storage systems, and variable frequency drives that control pumps and fans. This is why Real-Time Innovations (RTI) developed the Connext DDS platform — middleware built on the Data Distribution Service standard that operates without a central broker and ensures reliable message delivery with configurable Quality of Service (QoS) profiles.

RTI Connext DDS Compared to Other Protocols

What Is a Microgrid and Why Does It Matter

A microgrid is a localized energy system that combines generation sources (solar panels, wind turbines, diesel generators), energy storage systems (lithium-ion or LFP batteries), and consumers into a single managed cluster. Unlike the traditional grid, a microgrid can operate both in grid-connected mode and autonomously in islanded mode, switching between the two in milliseconds.

In a conventional power system, 50 Hz (or 60 Hz) frequency is maintained by massive rotating generators at thermal and nuclear power plants. Their mechanical inertia smooths out short-term load fluctuations. But when a significant share of energy comes from solar panels and wind turbines, that inertia disappears. A cloud blocking the sun for 30 seconds can cause frequency deviations capable of damaging sensitive equipment. A microgrid solves this problem because all its components exchange data in real time, and every element responds instantly to changes in the power balance.

Key Microgrid Components

• Distributed Energy Resources (DER) — solar inverters, wind turbines, microturbines, fuel cells
• Energy Storage Systems (ESS) — battery banks with inverters operating in grid-forming or grid-following modes
• Microgrid Controllers — programmable logic controllers (PLCs) executing power balancing algorithms
• Power Electronics — variable frequency drives for controlling motors in pumps, compressors, and ventilation systems
• Data Exchange Middleware — RTI Connext DDS or equivalents that provide communication between all nodes
• SCADA/HMI — visualization and supervisory control systems

RTI Connext DDS: Architecture and Operating Principles

Data Distribution Service (DDS) is a data exchange standard ratified by the Object Management Group (OMG). Unlike broker-based protocols such as MQTT, DDS uses a publish-subscribe model without a central intermediary. Each network node independently discovers other participants through an automatic discovery mechanism and subscribes only to the data it needs.

RTI Connext is a commercial implementation of the DDS standard that adds extended Quality of Service profiles, monitoring tools, secure encrypted data exchange, and cloud platform integration. The platform serves over 2,000 deployments worldwide — from medical devices to autonomous vehicles.

Quality of Service (QoS) Profiles

QoS profiles are what make DDS suitable for microgrid management. Here are the key ones used in energy applications:

• Reliability — guaranteed message delivery or best-effort delivery for non-critical data
• Durability — retaining the last known state so that a newly connected node immediately receives current information
• Deadline — monitoring the interval between messages; if data does not arrive on time, the system generates an alarm
• Lifespan — automatic removal of stale data to prevent nodes from using outdated readings
• Ownership — determining source priority when multiple publishers report conflicting data

OpenFMB: An Open Standard for DDS-Based Microgrids

Open Field Message Bus (OpenFMB) is a reference architecture developed by Duke Energy in collaboration with 25 partners, including RTI. OpenFMB defines standard data models for information exchange between distributed intelligent nodes in a microgrid. The standard has been ratified by the North American Energy Standards Board (NAESB) and the Smart Grid Interoperability Panel (SGIP).

The first reference implementation of OpenFMB was deployed at the Mount Holly microgrid, where the system demonstrated a transition to islanded mode in under 50 milliseconds. This is a critically important metric: when disconnected from the main grid, microgrid consumers experience no interruption in power supply.

Toronto Hydro: Real-World Deployment

Toronto Hydro, Canada's largest electricity distribution company, uses RTI Connext DDS to connect a network of inexpensive hardened National Instruments CompactRIO computers. This solution improved grid responsiveness, reduced operational risks, and enhanced power quality. Decentralized power management simplified oversight at feeder and substation levels.

Variable Frequency Drives in Microgrids: A Critical Role

Within a microgrid, variable frequency drives (VFDs) perform three key functions that are impossible with direct motor-to-grid connections:

1. Frequency stabilization — the VFD maintains the set motor speed regardless of microgrid frequency fluctuations. When solar generation drops sharply due to cloud cover, the VFD automatically compensates for voltage sag
2. Energy efficiency — according to the affinity laws for centrifugal machines, reducing pump speed to 80% of nominal cuts power consumption by approximately half. In a microgrid with limited generation capacity, this keeps critical equipment running while reducing power to non-critical loads
3. Energy regeneration — modern frequency converters with active front ends can return braking energy back to the microgrid network or batteries

Practical Example: Solar-Powered Water Supply

In agricultural microgrids, a variable frequency drive controls a submersible pump powered directly by solar panels. The MPPT (Maximum Power Point Tracking) algorithm built into the VFD tracks the panels' maximum power point and adapts pump speed to available energy. In the morning, as irradiance increases, the pump gradually ramps up output. In the evening, it slows down rather than stopping abruptly, protecting the pipeline from water hammer.

Integrating PLCs and VFDs via DDS in a Microgrid

Programmable logic controllers in a microgrid serve as local coordinators. A PLC collects sensor data (voltage, frequency, power, temperature), processes it using local algorithms, and publishes results to the DDS network. Other nodes — the central microgrid controller, neighboring PLCs, energy storage systems — subscribe to this data and make decisions accordingly.

A typical DDS-based data exchange architecture in a microgrid looks like this:

• Level 0 — Sensors and actuators: measurement transformers, temperature sensors, variable frequency drives, contactors
• Level 1 — Local controllers: PLCs with embedded DDS agents publishing topics with generation, load, and equipment status data
• Level 2 — Microgrid controller: a centralized or distributed controller subscribing to all topics and performing optimization based on minimum cost or maximum reliability criteria
• Level 3 — Supervisory control: SCADA/HMI for operators, visualizing microgrid status and enabling manual intervention

Advantages of the DDS Decentralized Approach for Microgrids

The classic approach with a central SCADA server has a critical vulnerability: if the server fails, the entire control system stops working. In a microgrid that must provide uninterrupted power supply during emergencies, this is unacceptable.

DDS addresses this problem through several architectural solutions:

• No single point of failure — each node can continue operating autonomously, even if part of the network goes down
• Automatic discovery — new devices (e.g., a mobile generator during an emergency) automatically join the network without manual configuration
• Selective subscription — each node receives only the data needed for its operation, reducing network traffic
• Deterministic latency — for critical commands (disconnecting a faulted segment, switching to islanded mode) DDS guarantees delivery within a defined timeframe

Applications of Frequency Converters in Renewable Energy

The VFD market continues to grow, with renewable energy becoming one of the key drivers. Modern VFDs optimize equipment operation under variable generation conditions: when a solar panel delivers maximum output at noon, the VFD accelerates the pump to optimal speed; as irradiance decreases, it smoothly reduces RPM rather than shutting the motor down.

Key benefits of VFDs in microgrids:

• Soft starting — eliminating inrush currents of 6-8 times nominal, which is critical in microgrids with limited generation capacity
• Operation under unstable supply — modern VFDs maintain stable output frequency even with input voltage fluctuations of up to plus or minus 15%
• Communication capabilities — expansion boards enable connection to industrial networks and DDS middleware

Modularity and Scalability

A key advantage of the DDS approach is modularity. Expansion boards for frequency converters and controllers allow adding communication interfaces (Ethernet/IP, PROFINET, CANopen) without replacing the core equipment. This means that an existing industrial installation with VFDs and PLCs can be integrated into a microgrid by installing communication modules and deploying DDS agents at the controller level.

Modularity works in the other direction too: a microgrid can be scaled incrementally — from a single solar installation with a battery to a full-scale distributed energy system with dozens of generators and hundreds of consumers. Each new node is automatically incorporated into the DDS network through plug-and-play discovery.

Technology Outlook

RTI continues developing its platform for the energy sector. Development directions include integration with electric vehicle charging infrastructure (EV Charging), creation of ad-hoc microgrids for emergency situations, and support for the IEEE 2030.5 standard for distributed energy resource interoperability.

For industrial facilities planning microgrid deployment, selecting equipment with open communication protocols is critically important. Modern variable frequency drives and programmable controllers support standard industrial buses that can be integrated into a DDS network through appropriate adapters and gateways. A phased approach from concept to implementation allows gradual expansion of microgrid capacity and functionality, starting with a pilot project.