Low-Voltage Electrical PV Power Generation Solution
Complete 380V/220V distributed photovoltaic electrical system — from DC-side protection to grid-connection acceptance, covering protection, distribution, metering, lightning protection, monitoring, and grid safety.
Full-System LV PV Electrical Architecture
Household rooftop & industrial/commercial distributed PV — AC 400V low-voltage grid-connection, following GB/T 19964, GB/T 16895.32, NB/T 32014.
DC Side System
PV Modules to Inverter
PV modules → PV-dedicated DC cables → Intelligent combiner box → DC circuit breaker / isolation switch → Inverter DC input.
- DC breakers mandatory — AC switches strictly prohibited (continuous DC arc risk)
- Select DC1000V / DC1500V PV-dedicated components
- Cable: PV1-F PV-dedicated cable, sun-proof, anti-rolling, ± separated
Intelligent Combiner Box
Household (small): No combiner box — modules direct to micro/string inverter.
Industrial/commercial (multi-string): 4/8/12/16-way intelligent combiner box.
- DC fuse + DC isolation switch + DC SPD (Level II)
- String current acquisition + temp/humidity monitoring
- Large projects: AFCI DC arc fault protection (fire prevention)
AC Side & Grid-Connected System
Inverter AC Output Protection
Each string inverter AC outlet: molded-case / miniature circuit breaker + residual current protection (RCD). Isolates internal inverter faults and AC leakage — prevents single-inverter failure from affecting the whole system.
LV PV Grid-Connected Cabinet
Cabinet: outdoor stainless steel SMC / indoor GGD/MNS. Standard configuration:
- Grid-connected breaker (4P) with overcurrent & short-circuit protection
- Isolation knife switch (visible disconnection point)
- Anti-islanding device (mandatory, action ≤ 2 s)
- AC Level II SPD + bidirectional smart meter (0.5S grade)
- Temp/humidity controller + heater (anti-condensation)
Optional: Anti-backflow controller, power quality module, remote comms (Modbus/4G).
Operating Modes
- Self-use + surplus grid-connected (preferred for I&C)
- Full grid-connected
- Self-generation, anti-backflow (no grid export)
Complete Protection Scheme
DC Side Protection
- Overcurrent: DC fuse
- Busbar short-circuit: DC circuit breaker
- Lightning: DC SPD (Level II)
- Advanced: AFCI DC arc fault (recommended for I&C roofs)
- Equipotential grounding: brackets & combiner box shells
AC Side Protection
- Anti-islanding (mandatory) — quick disconnect on grid loss
- Over/undervoltage & over/under-frequency (dual redundancy)
- Short-circuit & overload: grid-connected breaker
- Leakage: AC/A-type RCD for personal shock protection
- Surge: AC SPD at inverter terminal & grid cabinet
Anti-Backflow Protection
When surplus grid export is not allowed: anti-backflow controller monitors grid current in real time. On reverse power detection, reduces inverter output until blocked.
Lightning & Grounding System
Graded protection: Level I (optional, PV array) → DC Level II (combiner) → AC Level II (grid cabinet).
- Grounding: <100 kW → ≤10 Ω; ≥100 kW → ≤4 Ω
- All cabinets & brackets unified to PV main grounding grid
- Grounding main: ≥50 mm² copper conductor
Metering & Intelligent O&M
Metering Scheme
Self-use + surplus: Bidirectional smart meter at boundary point (forward purchase + reverse sale). Optional inverter-side meter for internal stats.
Full grid-connected: Unidirectional meter for total PV generation. Transformer: 0.5S grade, independent secondary circuit per DL/T448.
Monitoring Solutions
Basic: Inverter local display + mobile app for generation & fault alarms.
I&C centralized: Gateway collects inverter & grid cabinet data → cloud platform. Remote alarm, generation stats, fault location, power quality analysis. Large parks can connect to existing SCADA.
Household Simplified Scheme (≤10kW)
PV modules → string inverter (single-phase) → AC breaker → PV grid box (4P air switch + SPD + bidirectional meter) → household distribution box.
Single-phase access generally limited to ≤8 kW; beyond → switch to 3-phase 380V.
Design Risk Red Lines
❌ Never use AC breakers on PV DC circuits
❌ Never omit grid-point isolation fracture & anti-islanding device
❌ Always match SPD failure alarms — lost in thunderstorm without them
❌ Multiple scattered grounding points must form unified equipotential
❌ Breaker selective coordination — faults must not trigger upstream trips
❌ Coastal areas: select C5 anti-corrosion grade, outdoor cabinets IP54+
Active Sensing, Regulation & Grid Optimization
Modern LV electrical systems evolving from "passive protection" to "active sensing and regulation" — safe, stable, harmonious coexistence between PV generation and the municipal grid.
Core Grid-Connection Protection & Isolation
PV-Dedicated Grid-Connected Switch
Voltage-loss tripping (auto-disconnect on grid outage, prevent reverse power). Voltage-detection closing (auto-close on grid recovery). Integrated short-circuit & overload protection — the "first line of defense."
Anti-Islanding Protection Device
Real-time monitoring of grid voltage & frequency. On abnormality detection (outage, V/f exceeding limits), immediately cuts PV–grid connection — preventing "island" operation that threatens maintenance personnel safety.
Smart PV Circuit Breaker
New-gen "electromechanical separation, modular design" — protection function separated from primary equipment. Supports hot-plugging: faulty module replaced in minutes without power outage, minimizing generation loss during maintenance.
Intelligent "Four Capabilities" Regulation
Observable & Measurable
Smart IoT meters + PV interaction modules collect real-time voltage, current, power, and generation data. Uploaded to cloud or grid master station for panoramic generation perception — solving the "invisible & uncontrollable" problem.
Adjustable & Controllable
Flexible control: Grid/user system sends commands to PV inverter — real-time output adjustment based on grid capacity. Proactively reduces output during peak generation & grid congestion.
Rigid control: Emergency open/close via smart circuit breakers for extreme cases.
Power Quality Comprehensive Management
PV Grid-Connected LV Cabinet
Hub for grid-connection integrating protection + metering. Optional active power filter (APF) to control harmonic distortion within national standards (e.g. 5%), purifying the grid environment.
Dynamic Reactive Compensation (SVG)
For voltage fluctuations: SVG dynamically and rapidly adjusts reactive power, stabilizes grid voltage — especially effective during sudden irradiance changes.
PV-Dedicated Voltage Regulator
Solves "lunchtime voltage rise" in substation areas caused by excessive generation. Dynamically adjusts voltage in real time, stabilizing grid-connected voltage within compliance (e.g. <243V) — preventing inverter overvoltage trip and shutdown.
Energy Storage Coupling & Grid Optimization
LV Coupled Energy Storage
Connect storage on LV side of PV grid-connection. Store during peak PV / low tariff → release during peak usage / high tariff. Alleviates grid pressure, enhances project revenue through peak-valley arbitrage.
AC/DC Hybrid Microgrid
Innovative AC/DC hybrid structure for remote or weak-grid areas. PV DC power directly charges storage or supplies DC loads via DC lines — no inversion needed. Reduces conversion losses, solves low-voltage and PV consumption issues from long-distance supply.
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