Power Electronics in Renewable Energy Systems
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Questions and Answers

What is the primary function of the converter at the line-end in wind-electric systems?

  • To convert AC voltage to DC voltage
  • To generate a high-voltage DC output
  • To regulate the wind speed
  • To absorb or supply reactive power in a continuous manner (correct)
  • What is the typical output voltage range of the PV arrays in photovoltaic systems?

  • 120-V to 240-V AC
  • 52-V to 90-V DC (correct)
  • 480-V to 600-V AC
  • 240-V to 480-V DC
  • What is the primary advantage of photovoltaic systems over wind-electric systems?

  • Greater potential for distributed generation (correct)
  • Higher power output capacity
  • Higher efficiency
  • Lower cost of power electronic interfaces
  • What is the purpose of the power electronic system in photovoltaic systems?

    <p>To convert DC voltage to AC voltage</p> Signup and view all the answers

    What is the typical input to a fuel cell system?

    <p>Hydrogen, natural gas, or gasoline</p> Signup and view all the answers

    What is the maximum efficiency of a fuel cell system?

    <p>60%</p> Signup and view all the answers

    What is the primary reason for using power electronic converters in fuel cell systems and photovoltaic systems?

    <p>To interface with the utility</p> Signup and view all the answers

    Why is a power-electronic interface necessary in micro-turbine systems?

    <p>To vary turbine speed based on loading</p> Signup and view all the answers

    What is the primary benefit of energy storage systems in power systems?

    <p>Load-leveling and peak-shaving</p> Signup and view all the answers

    What type of energy storage system requires a power electronic interface, as shown in Figure 10?

    <p>Flywheel storage</p> Signup and view all the answers

    What is an example of poor power quality?

    <p>Distorted voltage waveforms</p> Signup and view all the answers

    What is the primary purpose of a power-electronic interface in power systems?

    <p>To interface with the utility</p> Signup and view all the answers

    What are the main power system components?

    <p>Transmission lines, substations, and distribution networks</p> Signup and view all the answers

    What is the primary function of a series capacitor in a power system?

    <p>Increasing transmission capability</p> Signup and view all the answers

    What type of power electronic device is used for shunt-compensation and injecting reactive power for voltage control?

    <p>Solid-state switch</p> Signup and view all the answers

    What is the main advantage of using a phase shifting transformer in a power system?

    <p>Increasing power transmission</p> Signup and view all the answers

    What is the primary function of a synchronous condenser in a power system?

    <p>Reactive power compensation</p> Signup and view all the answers

    What is the main characteristic of a solid-state switch in a power system?

    <p>Ability to turn-on or off in an ac circuit with a delay less than one-half a cycle</p> Signup and view all the answers

    Study Notes

    Power Electronics in Power Systems

    • Power electronics converters are necessary to interface with the utility for fuel cell systems and photovoltaic systems.

    Micro-Turbines

    • Micro-turbines use highly efficient aircraft engines with natural gas as the input fuel.
    • To improve efficiency, the turbine speed should be allowed to vary based on loading.
    • This causes the frequency of the generated output to vary, requiring a power-electronic interface.

    Energy Storage Systems

    • Energy storage systems offer benefits such as load-leveling and peak-shaving in power systems.
    • Energy is stored, usually at night when the load demand is low, and supplied back during peak-load periods.
    • Energy can be stored in lead-acid batteries, Super-conducting Magnetic Energy Storage (SMES) coils, and in the inertia of flywheels.

    Power Quality Solutions

    • Poor quality of power can imply distorted voltage waveforms, unbalances, swells and sags in voltage, power outages, and more.

    Main Power System Components

    • Transmission bottlenecks must be identified when operating electrical power systems, including:
      • Steady-State Power Transfer Limit
      • Voltage Stability Limit
      • Transient Stability Limit
      • Thermal Limit
      • Short-Circuit Current Limit

    Conventional System Solutions

    • Conventional systems enhance transmission capability by:
      • Series Capacitors (X)
      • Switched Shunt-Capacitor and Reactor (V drop solution)
      • Transformer Tap-changer LTC’s (V drop solution)
      • Phase Shifting Transformers (δ – power transmission)
      • Synchronous Condensers (V - drop solution)

    Categorizing Power Electronic Systems

    • Power electronic systems can be categorized as:
      • Solid-State Switches
      • By connecting two thyristors in anti-parallel (back-to-back) as shown in Figure, a solid-state switch can be realized that can conduct current in both directions and turn-on or off in an ac circuit with a delay less than one-half a cycle.

    Photovoltaic (PV) Systems

    • Photovoltaic systems are the ultimate in distributed generation and have a greater potential than wind-electric systems.
    • PV arrays provide a voltage of 52-V to 90-V DC, which the power electronic system converts to 240 V/50 Hz sinusoidal voltage suitable for interfacing with the single-phase utility.

    Fuel Cell Systems

    • The input to the fuel cell can be hydrogen, natural gas, or gasoline, and the output is a dc voltage.
    • The efficiency of fuel cell systems can be as high as 60%.

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    Description

    This quiz explores the importance of power electronics converters in fuel cell systems, photovoltaic systems, and micro-turbines. Learn about the role of power electronics in improving efficiency and interfacing with the utility. Topics include variable turbine speed and adjustable-speed drives.

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