Unsa ang Solid-State Transformer? 2025Tech, Iginuhit ang Struktura ug mga Prinsipyo

Larangan: Diseño ug Pagsulay

Australia

1. Ano ang Solid-State Transformer (SST)?

1.1 Pundamental ug Limitasyon sa mga Tradisyonal nga Transformers

Ang artikulo muna nagbalikan sa kasinatian (e.g., ang patente ni Stanley sa 1886) ug mga pundamental nga prinsipyo sa mga tradisyonal nga transformers. Batasan sa electromagnetic induction, ang mga tradisyonal nga transformers gisangpot sa silicon steel cores, copper o aluminum windings, ug insulation/cooling systems (mineral oil o dry-type). Sila nagoperar sa fixed frequencies (50/60 Hz o 16⅔ Hz), na may fixed voltage transformation ratios, power transfer capabilities, ug frequency characteristics.

Ang mga advantage sa mga tradisyonal nga transformers:

Mura
High reliability (efficiency >99%)
Short-circuit current limiting capability

Ang mga disadvantage kinahanglan:

Dako kaayo ug heavy weight
Sensitive sa harmonics ug DC bias
Walay overload protection
Fire ug environmental risks

1.2 Definision ug Origin sa Solid-State Transformers

Ang Solid-State Transformer (SST) usa ka alternative sa mga tradisyonal nga transformers batas sa power electronics technology, na may origin nga nagpuyo hangtod sa McMurray's "electronic transformer" concept sa 1968. Ang SSTs nakamit ang voltage transformation ug galvanic isolation pinaagi sa Medium-Frequency (MF) isolation stage, samtang naghatag og multiple intelligent control functions.

Ang basic structure sa SST includes:

Medium-Voltage (MV) interface
Medium-Frequency (MF) isolation stage
Communication ug control links

2. Design Challenges sa SSTs

2.1 Challenge: Handling Medium Voltage (MV)

Ang medium-voltage levels (e.g., 10 kV) labi na dako sa voltage ratings sa existing semiconductor devices (Si IGBTs up to 6.5 kV, SiC MOSFETs ~10–15 kV). Busa, kailangan adunay multi-cell (modular) o single-cell (high-voltage device) approach.

Advantages sa multi-cell solutions:

Modular ug redundant design
Multi-level output waveforms, reducing filter requirements
Support for hot-swapping ug fault tolerance

Advantages sa single-cell solutions:

Simpler structure
Suitable for three-phase systems

2.2 Challenge: Topology Selection

Ang SST topologies makakategorisahan isip:

Isolated Front-End (IFE): Isolation before rectification
Isolated Back-End (IBE): Rectification before isolation
Matrix converter type: Direct AC-AC conversion
Modular Multilevel Converter (M2LC)

2.3 Challenge: Reliability

Ang mga tradisyonal nga transformers labi na reliable, nganong ang SSTs adunay daghan nga semiconductors, control circuits, ug cooling systems, making reliability usa ka critical concern. Ang paper nag-introduce sa Reliability Block Diagrams (RBD) ug failure rate (λ in FIT) models, indicating na ang redundancy makapadako sa system reliability.

2.4 Challenge: Medium-Frequency Isolated Power Converters

Common topologies include:

Dual Active Bridge (DAB): Power flow controlled via phase shift, enabling soft switching
Half-Cycle Discontinuous Mode Series Resonant Converter (HC-DCM SRC): Achieves ZCS/ZVS, exhibiting "DC transformer" characteristics

2.5 Challenge: Medium-Frequency Transformer Design

Ang medium-frequency transformers nagoperar sa kHz-level frequencies, facing challenges such as:

Smaller magnetic core volume
Conflict between insulation ug thermal management
Uneven current distribution in Litz wire

2.6 Challenge: Isolation Coordination

Ang medium-voltage units nanginahanglan og high insulation to ground, necessitating consideration of:

Combined 50 Hz power frequency ug medium-frequency electric field stress
Dielectric losses ug risk of localized overheating

2.7 Challenge: Electromagnetic Interference (EMI)

Ang common-mode currents generated during MV switching can flow to ground through parasitic capacitance ug must be suppressed using common-mode chokes.

2.8 Challenge: Protection

Ang SSTs nanginahanglan mog handle overvoltage, overcurrent, lightning strikes, ug short circuits. Ang traditional fuses ug surge arresters remain applicable but should be combined with electronic current limiting ug energy absorption strategies.

2.9 Challenge: Control

Ang SST control systems complex ug nanginahanglan og hierarchical structure:

External control: Grid interaction, power dispatch
Internal control: Voltage/current regulation, redundancy management
Unit-level control: Modulation ug protection

2.10 Challenge: Construction of Modular Converters

Building practical MV modular systems involves:

Insulation design
Cooling systems
Communication ug auxiliary power
Mechanical structure ug hot-swappable support

2.11 Challenge: Testing of MV Converters

MV testing facilities complex ug nanginahanglan:

High-voltage, high-power sources/loads
High-precision measurement equipment (e.g., high-voltage differential probes)
Backup test strategies (e.g., back-to-back testing)

3. Applicability ug Use Cases sa SSTs

3.1 Grid Applications

Ang SSTs makapagamit sa power grids para sa:

Voltage regulation ug reactive power compensation
Harmonic filtering ug power quality improvement
DC interface integration (e.g., energy storage, photovoltaics)

But, compared to conventional Line Frequency Transformers (LFTs), ang SSTs face an "efficiency challenge":

LFT efficiency can reach 98.7%
SSTs typically achieve only ~96.3% due to multi-stage conversion
Limited reduction in size ug weight (~2.6 m³ vs. 3.4 m³)
Significantly higher cost (>52.7k USD vs. 11.3k USD)

3.2 Traction Applications

Ang traction systems (e.g., electric locomotives) adunay stringent requirements sa size, weight, ug efficiency, diin ang SSTs nagsugyot sa clear advantages:

Significantly reduced transformer size through higher operating frequencies (e.g., 20 kHz)
Dual optimization of efficiency ug volume reduction

3.3 DC-DC Applications

Sa DC systems (e.g., offshore wind power collection, data centers), ang SSTs ang tanging viable isolation solution, tungod kay ang ilang operating frequency mahimong freely chosen without being constrained by grid frequency.