1.1 Systems, Power Converters, and Power Semiconductor Devices

• Significance of Power Electronics Technology Development: A global driver for energy efficiency, serving as a technological backbone to enhance power system efficiency amid climate change, energy security challenges, and urbanization.
• Evolution of Power Conversion Technology:
  • Mechanical conversion (bulky, high loss, narrow control bandwidth) → Power electronics converters (high-frequency, high-efficiency, flexible control).
• IEEE Definition of Power Electronics Technology: Encompasses the effective use of electronic components, application of circuit theory and design techniques, and development of analysis tools, focusing on the efficient electronic conversion, control, and regulation of electrical energy.

1.1.1 Basic Principles of Power Converters

• Functional Objective: Achieve efficient power conversion and control via semiconductor devices (efficiency ~95%).
• Core Components:
  • Power semiconductors (switching devices) + Passive components (energy storage) + Control units (control and feedback).
• Underlying Principle: Discretize continuous energy flow into “energy packets,” process them, and reconstruct continuous energy flow at the output.
• Division of Labor for Three Core Components:
  • Power semiconductors (IGBT, MOSFET, etc.): Control energy flow via switching.
  • Passive components (inductors/capacitors): Transient energy storage and filtering.
  • Control units: Implement switching control of power devices and system diagnostics.
• Significance of Switching Mode Operation:
  • Discrete energy processing reduces losses.
  • High-frequency switching minimizes passive component size.
  • Balances efficiency and cost.

1.1.2 Converter Types and Device Selection

• Classification and Comparison of Converter Types:
  • Voltage Source Converter (VSI):
    • Uses capacitor energy storage; must drive inductive loads at the terminal. Requires a reverse freewheeling path (body diode or external freewheeling diode).
    • Trends toward low loss and compactness (dominant in the market).
  • Current Source Converter (CSI):
    • Uses inductor energy storage; requires symmetric blocking devices (e.g., GCT or series diodes).
    • High short-circuit resistance but larger volume and lower efficiency.
• Device Selection Criteria:
  • Voltage/current blocking margins, switching frequency, cooling method.
  • Topology (two-level/multilevel), packaging technology (modular PEBB).

1.2 Application and Selection of Power Semiconductors

• Six Dimensions for Converter Design Decisions:
  • Device type (unipolar/bipolar) and ratings (current/voltage/frequency limits).
  • System switching frequency.
  • Converter hardware design (minimizing stray inductance/capacitance, skin effect).
  • Topology (two-level/multilevel, hard-switching/soft-switching).
  • Device control methods.
  • System control design.
• Mainstream Device Technologies:
  • Thyristors (high-power, low-frequency), IGBTs (medium-high frequency, medium-power), MOSFETs (high-frequency, low-power).
  • Packaging technologies: Discrete devices (<10 kW), modules (MW-level), press-pack (GW-level).
  • Emerging technologies: SiC/GaN devices (high-frequency, low-loss), soft-switching technology (increasing frequency-power product to 5×10⁹ VA/s).

1.3 Applications of Power Semiconductor Devices

1.4 Power Electronics Equipment for Carbon Emission Reduction

• Energy Efficiency Revolution:
  • Data: IGBT technology reduced 33.4 billion tons of CO₂ emissions over 20 years (data from 2013 APEC meeting, equivalent to 390 1GW coal-fired power plants operating for 20 years).
• Energy Saving and Cost Reduction Potential:
  • Motor systems: 50% of global electricity is used for motors; variable frequency drives can reduce power losses.
  • Lighting systems: 21% of global electricity is used for lighting; LED + electronic ballasts save 61% energy compared to traditional solutions.
  • Information technology (IT, including data centers and 5G base stations): Global energy consumption accounted for ~15% in 2017. 400V DC systems achieve 70% efficiency vs. 5% for AC systems.
  • Renewable energy: The unit power cost of wind/solar converters is comparable to 50Hz standard transformers.
• Market and Technology Forecasts:
  • By 2050, the power semiconductor market will grow 10x compared to 2010.
  • Power electronics supports global carbon neutrality via “high-efficiency conversion” and “intelligent control.”
  • Future technologies must break through “efficiency limits” and “system cost” to achieve full-chain decarbonization in energy production-transmission-consumption.