The low-voltage distribution transformer district flexible energy storage system is a customized flexible energy storage solution specially developed for 0.4kV distribution districts. Relying on energy storage units, bidirectional converters and an intelligent energy management platform, it realizes flexible power regulation. It can solve common problems including district overload, voltage fluctuation, three-phase unbalance and accommodation of distributed photovoltaic power. Large-scale reconstruction of power lines and transformers is not required. The system takes grid stability, cost reduction & efficiency improvement and emergency power supply into comprehensive consideration, and is mainly composed of six categories of products as follows:
I. Energy Storage Battery System (Energy Source)
- Lithium iron phosphate cell / Sodium-ion cell
- Battery Module → Battery String → Energy Storage Cabinet / Container (50～500kWh)
II. Flexible PCS (Core, Differentiated from Conventional Energy Storage)
- Low-voltage four-bridge-arm PCS (100/200/300kW)
- Core Capabilities: Independent phase-separated control, three-phase unbalance mitigation, millisecond-level response
- Supported Functions: Seamless grid-connected/off-grid switching, Virtual Synchronous Machine (VSG)
III. BMS Battery Management System
- BMS Master Unit + Slave Units: Monitor voltage / current / temperature / SOC / SOH
- Protection Functions: Overcharge & overdischarge protection, overcurrent protection, overtemperature protection, low-temperature protection, cell equalization management
IV. Flexible EMS / District Coordination Controller (System Brain)
- On-site district energy storage controller (core of flexible regulation)
- Functions: Peak shaving & valley filling, voltage & frequency regulation, three-phase unbalance governance, anti-reverse power flow, grid-connected/off-grid strategy control, multi-district power mutual support
- Cloud Platform: Remote monitoring, virtual power plant aggregation, AI dispatching optimization
V. Flexible Power Distribution & Grid-Connection Equipment
- Flexible grid-connection cabinet / Grid-connected & off-grid switching cabinet (0.4kV side)
- AC & DC combiner cabinet, SVG reactive power compensation module (optional)
- Intelligent district integrated terminal, electricity meter, communication gateway
VI. Temperature Control + Fire Protection + Auxiliary System
- Temperature Control: Air cooling / Liquid cooling (cabinet air conditioner, liquid cooling unit)
- Fire Protection: Smoke detector, temperature detector, heptafluoropropane / aerosol fire suppression
- Security Protection: Camera, access control, UPS, earthing system
VII. Typical Integrated Products (Common Models)
- 50kW/100kWh integrated flexible energy storage cabinet (integrated with battery + PCS + BMS + EMS)
- 125kW/250kWh outdoor flexible energy storage container (IP54 protection grade, floor area ＜ 3㎡)
Differences Between Flexible System and Conventional District Energy Storage
- Conventional Energy Storage: Only realizes peak shaving & valley filling and basic grid connection
- Flexible Energy Storage: Added functions including three-phase unbalance mitigation, millisecond-level voltage regulation, seamless grid-connected/off-grid switching and interconnection & power mutual aid among multiple districts. It serves as the core equipment for "flexible upgrading" of distribution networks.
