"Station-area energy storage: A flexible transformation of the distribution network's 'last mile'."

"Station-area energy storage: A flexible transformation of the distribution network's 'last mile'."

In China’s distribution network, the low‑voltage station area has always been the “last mile” that connects the main grid to every household. However, it is precisely this final stretch that has long been under dual pressure from both power supply quality and renewable energy integration. Especially in rural areas, old urban districts, and regions with high penetration of distributed photovoltaics, problems such as voltage sags, three‑phase imbalance, and distribution transformer overloading are becoming increasingly prominent, constituting a core bottleneck that constrains power supply reliability and power quality.The conventional response – distribution capacity expansion and renovation – not only involves lengthy approval processes and long construction periods, but also suffers from low equipment utilisation when dealing with seasonal or time‑varying loads, making it difficult to keep up with the rapidly changing power consumption landscape. In this context, a more flexible and cost‑effective solution has come into the industry’s spotlight: station‑area energy storage.

"Three major pain points force a technological breakthrough."

Low‑voltage issues: Long supply radii and undersized conductors cause significant voltage drops at the far end during peak load periods, often pushing the voltage below the national standard permissible range (for 220 V single‑phase supply, the deviation is required to be within +7% / –10%). As a result, air conditioners in households may fail to start, and lights dim – leading to frequent customer complaints.

Three‑phase imbalance: The haphazard connection of large numbers of single‑phase loads and single‑phase PV systems results in severe asymmetry among the three‑phase currents in the station area. Conventional mitigation measures can address only about 30% of the unbalanced load; the remaining imbalance translates into increased line losses and accelerated equipment ageing, compromising both economic efficiency and operational safety.

Distribution transformer overload: With the proliferation of electric‑vehicle charging piles and the rising power ratings of household appliances, coupled with the reverse power flow generated during midday peaks of distributed PV generation, transformers face the risk of both forward and reverse overload. Reverse load rates sometimes exceed 80%, threatening the safe operation of the equipment.In the face of these intractable problems, station‑area energy storage – with its advantages of fast response, precise control, and flexible deployment – acts as a precise “flexible scalpel” to address them effectively.

“Policy tone-setting: From auxiliary accommodation to grid substitution.”

By the end of 2025, the industry positioning of station‑area energy storage underwent a fundamental shift. At the national level, Document No. 1710 formally incorporated it into the key tasks for high‑quality development of the power grid, granting it the strategic status of “grid‑substituting energy storage.” This means that station‑area energy storage is no longer merely an auxiliary measure to facilitate renewable energy accommodation, but is now regarded as an active infrastructure solution that can effectively replace conventional grid expansion and retrofitting projects.

The policy explicitly encourages priority deployment in areas where distribution network expansion is constrained or in remote regions, with the aim of enhancing power supply reliability for weak links at lower cost and higher efficiency. According to industry estimates, compared with traditional transformer capacity expansion or line upgrading schemes, the total investment cost of station‑area energy storage can be reduced by more than 70%, indicating substantial market potential.

“Technical core: The four‑quadrant capability behind precise regulation.”

Although a station‑area energy storage system consists of common components such as PCS (Power Conversion System), batteries, and EMS (Energy Management System), its operational logic is fundamentally different from that of commercial and industrial energy storage. The core distinction lies in the fact that it does not simply charge and discharge according to fixed time schedules; instead, it dynamically intervenes in grid parameters such as voltage, power flow, and unbalance through the four‑quadrant power regulation capability of the PCS, based on real‑time grid conditions.

Taking the mitigation of low voltage at the line end as an example, the system operates as follows: When the monitored voltage drops below a preset threshold (e.g., 210 V), the energy storage system immediately switches to discharge mode, injecting active power into the station area. This effectively adds a local power source at the far end, directly compensating for line voltage drops. At the same time, the PCS can also output capacitive reactive power to offset the additional voltage drop caused by inductive reactive power, further stabilising the voltage. Before the arrival of peak loads, the system stores energy in advance and releases it during peak periods, achieving a "dynamic capacity enhancement" effect that prevents voltage sags from occurring in the first place.

“Site‑specific access and control strategies.”

The deployment approach for station‑area energy storage is not fixed. When mitigating low‑voltage issues at the line end, storage devices should be placed near the load end or at targeted remediation points; whereas for addressing regional reverse overload and overvoltage caused by distributed PV, it is more appropriate to arrange them centrally at the head end of the distribution network. Regardless of the approach, the operational control must collect real‑time voltage and current signals from the station area, and issue commands via the EMS or smart terminals to achieve intelligent regulation based on actual power flow, rather than relying on empirical time‑based strategies.

It is worth noting that there are a large number of single‑phase loads and single‑phase PV systems in the station area, and power quality issues often occur only on a particular phase. Therefore, the PCS used in station areas must adopt a three‑phase four‑wire topology and be capable of independently controlling active and reactive power for each phase. The four‑leg topology unique to Yingbo Smart Storage demonstrates superior performance in this regard, enabling precise mitigation of complex problems such as three‑phase imbalance and low voltage at the line end.

“After mitigation”

“From single to collaborative governance.”

The role of station‑area energy storage continues to expand. To date, a variety of integrated management models have emerged, including flexible interconnection between station areas, seamless switching between grid‑connected and islanded modes for backup power supply, and coordinated operation with 10 kV centralized energy storage. These new applications not only enhance the power supply reliability and disturbance resilience of the station area itself, but also lay the groundwork for future flexible interaction between the distribution network and the main grid.

“Seamless On/Off‑Grid Switching for Power Backup.”

In summary, this "flexible scalpel" of the distribution network is reshaping the peripheral nerves of the power system through distributed deployment and collaborative interaction. It is not only one of the keys to resolving the current "red zone" predicaments, but also an indispensable cornerstone for building a new-type power system with high resilience, high flexibility, and high interactivity. This transformation taking place in the "last mile" of the distribution network is ushering in a brand‑new energy era for us.