Power electronics

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Applications

Less than 100W: Small motor drives used in home appliances (washing machine, vacuum cleaners, hand dryers, induction cooking, hood fan) ,Switched-mode power supplies for portable equipment

Less than 10kW: • Power supplies for Laptop/PC, Variable-speed motor drives used in commercial buildings

10kW up to 1MW: • High power motor drive • Traction control • Renewable energy system

More than 1MW: • Utility transmission lines • Grid connected system • Reactive Power Control

Photo Voltaic Systems: Using solar panels, an unregulated dc voltage must be boosted and then converted to AC voltage with standard grid amplitude and frequency

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Wind turbine generator: Wind turbines generate voltage with variable frequency and amplitude due to variable power and speed of wind. A power converter is needed to convert the variable AC voltage to the adjustable one suitable for grid.

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Loss generated by current

Heat increased

Efficiency decreased

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AC to DC conversion

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Power Electronics System Modules

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Input: (AC or DC) voltage or current source and a load, e.g. resistive load.

Cascade Conversion: multiple converters connected in cascade.

Power semiconductor devices: power switches to chop input voltage or current waveform to control the flow of energy.

Control system: open-loop or close-loop system implemented mainly in digital electronics (in some cases we use analog circuits)

Gate drivers: Gating circuit to provide the gate drive signals to support switching devices if the control signals would not be strong enough for switching

Circuit breakers: One or more static switches acting as a circuit breaker to run off the whole system if there is any short circuit.

Sensors: Current, voltage and thermals sensors for overvoltage, overcurrent and over temperature scenarios.

Filters: Input and output filters for immunity and emission control.

High Power and Low Power:

Power diode

Power Metal-oxide Field-Effect Transistor (Power MOSFET)

Insulated-Gate Bipolar Transistor (IGBT)

High Power:

• Silicon-Controlled Rectifier (SCR) or Thyristor

• Power Bipolar Junction Transistor (BJT)

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Thyristor:

Application in high voltage converters due to its characteristic of withstanding high voltage and delivering high current

Used in simple and cheap AC-AC converters

Gate Turn-off Thyristor (GTO) for high power applications.

MOS-Controlled Thyristor (MCT) for high power applications.

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Application of Power Converters

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Power Factor Correction

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P is not time dependent.

When θv = θi , it is a purely resistive load case.

When θv– θi = ±90o, it is a purely reactive load case.

P = 0 means that the circuit absorbs no average power.

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Power diodes

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Thyristor

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Single-phase half-wave rectifiers

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Single-phase full-wave rectifier

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