Ano ang mga pangunahing konsiderasyon sa pagpili ng photovoltaic transformer?

Prinsipyong Pagsukat at Teknikal na mga Parameter ng Photovoltaic Transformers

Ang pagsukat ng photovoltaic transformers ay nangangailangan ng komprehensibong pag-considera ng maraming factor, kasama ang capacity matching, voltage ratio selection, setting ng short-circuit impedance, determination ng insulation class, at thermal design optimization. Ang mga pangunahing prinsipyong pagsukat ay sumusunod:

(I) Capacity Matching: Batayan para sa Load Bearing

Ang capacity matching ay ang core prerequisite sa pagsukat ng photovoltaic transformers. Ito ay nangangailangan ng tumpak na pagtugma ng kapasidad ng transformer sa inilapat na kapasidad ng photovoltaic system at inaasahang maximum output power, upang matiyak ang stable na operasyon sa layunin na load. Ang formula ng pagsukat ng kapasidad ay:

kung saan ang U₂ ay kumakatawan sa secondary-side voltage ng transformer (karaniwang 400V). Tinitingnan ang inherent variability ng photovoltaic systems (halimbawa, pagbabago ng liwanag ng araw at load changes), ang calculation ay dapat kumakatawan sa safety margin (1.1–1.2 times), load-rate fluctuation coefficient (halimbawa, KT = 1.05, at power factor (karaniwang 0.95).

Halimbawa: Para sa isang photovoltaic system na may peak power output na 500kW, maaaring pipiliin ang 630kVA, 800V/400V transformer upang makapag-adapt sa iba't ibang kondisyon ng liwanag ng araw at load. Bukod dito, ayon sa Technical Guidelines for Distributed Photovoltaic Grid Connection, ang kapasidad ng iisang distributed photovoltaic power station ay hindi dapat lampa sa 25% ng maximum load sa power supply area ng upper-level transformer, upang maiwasan ang grid impacts.

(II) Voltage Ratio Selection: Pag-aadapt sa Fluctuations at Voltage Regulation

Ang voltage ratio ay dapat tugma sa output characteristics ng photovoltaic system (inverter voltage karaniwang nagfluctuate ng ±5%) at grid connection requirements, na may dynamic adjustment capabilities. Mayroong dalawang pangunahing paraan ng adjustment:

• Tap-changer adjustment: Applicable sa off-load tap-changing transformers, karaniwang may tatlong ±5% taps (halimbawa, 10.5kV/10kV/9.5kV), na nangangailangan ng power-off operation.

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

Sa aktwal na operasyon, ang angkop na taps ay dapat pipiliin batay sa load characteristics: 5% tap para sa light loads, at 2.5% o 0% taps para sa heavy loads, na nagbibigay ng balanse sa voltage rise sa mataas na photovoltaic generation at voltage drop sa gabi na peak loads.

(III) Setting ng Short-Circuit Impedance: Balanse ng Proteksyon at Stability

Ang short-circuit impedance ay dapat idisenyo ayon sa short-circuit current level ng sistema at uri ng transformer (oil-immersed/dry-type), na may formula ng pagsukat:

Oil-immersed: 4%–8%; dry-type: 6%–12%. Para sa malalaking transformers (halimbawa, 9150kVA), taasan ang impedance ( Zk ≥ 20% ). Gawan ng temperature correction (75°C para sa oil-immersed, 120°C para sa dry-type).

(IV) Insulation Class

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

(V) Thermal Design

Optimize ayon 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. Ang isang desert station ay gumagamit ng micro-channel liquid cooling (7:3 deionized water + ethylene glycol) para sa 3× efficiency.

V. Sizing & Inspection para sa Iba't Ibang Scenarios

Solutions para sa typical scenarios:

(I) Grid-Connected

Sizing: Saklawin ang inverter/auxiliary power + 1.15× margin (halimbawa, 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% ng factory value).

(II) Off-Grid

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

(III) High-Temperature

Sizing: Dry-type + forced air o oil-immersed + naphthenic oil. Gamitin ang 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: Ang tumpak na pagtugma ng capacity, voltage, impedance, insulation, at thermal design, plus thorough inspection, ay nag-uugnay sa ligtas, efficient, at mahabang-buhay na operasyon, na sumasang-ayon sa distributed PV development under carbon goals.