What Are Active Distribution Networks?

Active distribution networks are electric power distribution systems that incorporate distributed energy resources (DERs), advanced monitoring infrastructure, and real-time control capabilities to manage bidirectional power flows across the network. Traditional distribution networks were designed to carry electricity in one direction, from high-voltage transmission lines through substations to end consumers. Active distribution networks depart from this model by integrating generators, storage systems, and controllable loads directly within the distribution grid, requiring coordinated management at every node.

The concept emerged from the proliferation of rooftop solar photovoltaics, battery storage, combined heat and power plants, and electric vehicle chargers connected at the medium- and low-voltage level. Standards such as IEEE 1547, which governs the interconnection and interoperability of distributed energy resources, provide the technical framework under which these resources connect to and participate in distribution network operation.

Distributed Energy Resource Integration

Integrating DERs into a distribution network changes the electrical characteristics of every feeder to which they connect. Photovoltaic inverters inject real power during daylight hours, while batteries can both absorb and supply energy on short timescales. Each resource must comply with ride-through requirements, voltage and frequency response curves, and anti-islanding protections defined by grid codes and standards such as IEEE 1547 and IEEE 2030. The density of DERs that a given feeder can host without exceeding voltage or thermal limits is known as the hosting capacity, and its accurate estimation is central to active network planning. The IEEE Power and Energy Society's work on active distribution networks addresses the interplay between DER expansion and network stability.

Network Management and Voltage Regulation

Managing voltage within statutory limits is the primary operational challenge in active distribution networks. Conventional voltage regulation relied on tap-changing transformers and capacitor banks acting on aggregate load profiles. With DERs injecting variable power at scattered points, voltages can rise above limits during periods of high generation and low demand. Active management addresses this through coordinated volt-VAR optimization, where DER inverters provide reactive power support, and through distribution management systems (DMS) that issue setpoint adjustments in real time. Distribution-level energy management systems (DERMS), guided by the IEEE 2030.11 standard, coordinate large populations of DERs and provide the control layer that transforms a passive feeder into a responsive, actively managed network.

Bidirectional Power Flow and Protection

Bidirectional power flow changes how protection systems must respond to faults. Conventional overcurrent relays assume that fault current flows from the substation toward the fault. When DERs feed current toward the substation from the load side, directional relays and adaptive protection schemes are required. Reclosers and sectionalizers must account for the possibility that a distributed generator maintains voltage on an isolated section, creating an unintentional island. Protection coordination studies for active networks require load-flow solvers capable of handling the variable and distributed nature of generation, as detailed in ongoing IEEE Transactions on Power Delivery research covering active network protection coordination.

Applications

Active distribution networks have applications across multiple energy and infrastructure sectors, including:

• Utility distribution systems integrating high penetrations of solar and wind generation at the feeder level
• Microgrids serving campuses, military bases, and communities that can island from the main grid during outages
• Electric vehicle charging corridors where managed charging prevents transformer overloads during peak periods
• Industrial facilities with on-site generation and storage optimizing behind-the-meter energy costs
• Rural electrification projects where distributed generation supplements or replaces grid extension