Unsa ang mga pangunahon nga konsiderasyon alang sa pagpili og photovoltaic transformer?

Prinsip Sizing ug mga Teknikal nga Parametro sa Photovoltaic Transformers

Ang pag-size sa photovoltaic transformers nanginahanglan og komprehensibong pagkonsidera sa daghang mga faktor, kasagaran ang capacity matching, voltage ratio selection, short - circuit impedance setting, insulation class determination, ug thermal design optimization. Ang key sizing principles mao kini:

(I) Capacity Matching: Fundamental para sa Load Bearing

Ang capacity matching mao ang core prerequisite sa sizing sa photovoltaic transformers. Kini nagkinahanglan og eksaktong pag-match sa capacity sa transformer sa installed capacity sa photovoltaic system ug sa expected maximum output power, siguradohon ang stable operation sa intended load. Ang formula sa capacity calculation mao kini:

diin ang U₂ mao ang secondary-side voltage sa transformer (kasagaran 400V). Tungod sa inherent variability sa photovoltaic systems (e.g., fluctuations sa sunlight ug load changes), ang calculation kinahanglan mag-include og safety margin (1.1–1.2 times), load-rate fluctuation coefficient (e.g., KT = 1.05, ug power factor (kasagaran 0.95).

Example: Para sa photovoltaic system nga may peak power output sa 500kW, mahimo mopili og 630kVA, 800V/400V transformer aron matugutan ang uban-uban nga kondisyon sa sunlight ug load. Padayon pa, sumala sa Technical Guidelines for Distributed Photovoltaic Grid Connection, ang capacity sa usa ka distributed photovoltaic power station dili dapat mogawas sa 25% sa maximum load sa power supply area sa upper-level transformer, aron mas evitar ang grid impacts.

(II) Voltage Ratio Selection: Adapting sa Fluctuations ug Voltage Regulation

Ang voltage ratio kinahanglan mag-align sa output characteristics sa photovoltaic system (inverter voltage kasagaran nag-fluctuate sa ±5%) ug grid connection requirements, adunay dynamic adjustment capabilities. Adunay duha ka pangunihang adjustment methods:

• Tap-changer adjustment: Applicable sa off-load tap-changing transformers, kasagaran adunay tulo ka ±5% taps (e.g., 10.5kV/10kV/9.5kV), giginahan sa power-off operation.

• Automatic voltage regulation module adjustment: Applicable sa on-load tap-changing transformers, nag-enable sa online dynamic adjustment sa response time ≤200ms.

Sa aktwal nga operasyon, ang appropriate taps kinahanglan mopili batas sa load characteristics: 5% tap para sa light loads, ug 2.5% o 0% taps para sa heavy loads, balancing voltage rise sa high photovoltaic generation ug voltage drop sa nighttime peak loads.

(III) Short-Circuit Impedance Setting: Balancing Protection ug Stability

Ang short-circuit impedance kinahanglan idesign sumala sa system's short-circuit current level ug transformer type (oil-immersed/dry-type), ang formula sa calculation mao kini:

Oil-immersed: 4%–8%; dry-type: 6%–12%. Para sa large transformers (e.g., 9150kVA), i-increase ang impedance ( Zk ≥ 20% ). Gibuhat temperature correction (75°C sa oil-immersed, 120°C sa dry-type).

(IV) Insulation Class

Fit outdoor environments. Prefer Class F (155°C) o H (180°C). Gamiton ang H-class sa deserts, salt-spray-resistant materials sa coasts, moisture-resistant sa high humidity. Consider thermal aging: +6°C doubles aging; -6°C halves it.

(V) Thermal Design

Optimize batas sa environment. Cooling methods: natural/forced air cooling, oil-immersed self-cooling. Para sa high-temp areas: forced air o hybrid; high-humidity: dry-type + axial ducts; high-dust: IP54 + filters. Usa ka desert station gamiton micro-channel liquid cooling (7:3 deionized water + ethylene glycol) para sa 3× efficiency.

V. Sizing & Inspection para sa Different Scenarios

Solutions para sa typical scenarios:

(I) Grid-Connected

Sizing: Cover inverter/auxiliary power + 1.15× margin (e.g., 1092.5kVA). Match ±5% voltage, 4%–8% impedance, ≥Class F, natural/oil-air cooling. Inspection: Check insulation, THD ≤ 5%, voltage regulation (±2.5%), impedance (±2% of factory value).

(II) Off-Grid

Sizing: 1.2–1.5× load power. Adapt to inverter (e.g., 800V/400V), 6%–12% impedance, ≤200ms voltage regulation, 400V + 220V windings. Inspection: Test overload (≥120%), voltage regulation response, voltage balance, and system fluctuations.

(III) High-Temperature

Sizing: Dry-type + forced air or oil-immersed + naphthenic oil. Use high-temp insulation, IP55, 80°C-start/60°C-stop fans. Inspection: Quarterly thermography, semi-annual oil tests, check cooling, monitor winding temp.

(IV) High-Humidity/Coastal

Sizing: IP65 epoxy dry-type, 316L + fluorocarbon coating, salt-resistant insulation, increased spacing. Inspection: Check coating, oil moisture/gases, salt-spray test (≤5% power drop), monitor hydrogen.

(V) High-Dust

Sizing: Fully sealed, IP54, three-stage filters, enlarged cooling area, wear-resistant windings. Inspection: Replace filters quarterly, thermography, check dust-proofing, clean regularly.

(VI) Electromagnetic Interference

Sizing: Sandwich windings (≤500pF), LC filters ( THD ≤ 4% ), meet EMC (GB/T 21419-2013), dual-redundant comms. Inspection: Annual EMC tests, monitor harmonics/unbalance, check grounding (≤0.5Ω), test bit error 10^-8.

(VII) PV-Energy Storage Integration

Sizing: Integrate PCS (Modbus RTU), 400V + 220V windings, ≤200ms reactive compensation, consider combined loads. Inspection: Verify PCS compatibility, voltage balance (≤1%), test voltage regulation (≤±2%), check storage connections.

Summary: Accurate matching of capacity, voltage, impedance, insulation, and thermal design, plus thorough inspection, ensures safe, efficient, and long-life operation, aligning with distributed PV development under carbon goals.