Teaching Utility Applications of Power Electronics in a First Course on Power Systems

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Teaching Utility Applications of Power
Electronics in a First Course on Power Systems
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Outline

• Importance of teaching power electronics in a
  power systems course
• Description of proposed approach consisting of
  four segments
• Functional aspects of power electronics
• Power device capabilities and Power Electronic
  Structures
• Role of power electronics in utility applications
• Details of the power electronics structures

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Importance

• Increasing applications of Power Electronic
  Equipment in Power Systems
• Availability of high power semiconductor devices
• Decentralized renewable energy generation
  sources
• Increased power transfer with existing
  transmissionsystem
• Effective control of power flow needed in a
  deregulated environment
• Norms for Power quality

Future Power System
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Approach

• Top Down approach consisting of four segments
• Function of power electronics as an interface,
  and the listing of utility applications requiring
  power electronics interface (1 lecture)
• Power device capabilities and the resulting
  structures of power electronic interfaces to
  exploit them (1 lecture)
• Importance and the role of power electronic
  interfaces in various applications (2 lectures)
• Discussion of power electronics interface in
  appropriate detail (3 lectures)

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Segment 1 Function of Power Electronics in
Utility Applications

• Enabling technology providing interface between
  two (ac/dc) electrical systems
• E.g.
• Interconnection of two asynchronous ac systems
• dc to ac conversion is required to connect fuel
  cells or photovoltaics to the utility grid

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Segment 1 Listing of Power Electronic
Applications

• Distributed generation (DG)
• Renewable resources (wind and photovoltaic)
• Fuel cells and micro-turbines
• Storage batteries, super-conducting magnetic
  energy storage, flywheels
• Power electronics loads Adjustable speed drives
• Power quality solutions
• Dual feeders
• Uninterruptible power supplies
• Dynamic voltage restorers
• Transmission and distribution (TD)
• High voltage dc (HVDC) and medium voltage dc
• Flexible AC Transmission Systems (FACTS) Shunt
  and Series compensation, and the unified power
  flow controller

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Segment 2 Power Device Capabilities Resulting
Power Electronic Structures

• Power Semiconductor Devices and their
  Capabilities
• Polarity of voltage blocked and direction of
  current conduction
• Switching speeds and power ratings

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Segment 2 Structure of Power Electronic Systems

• Voltage-Link Systems
• Transistors and diodes that can block voltage of
  only one polarity
• Current-Link Systems
• higher power bipolar voltage-blocking
  capabilities of thyristors
• Solid State Switches
• bidirectional voltage blockingand current
  conduction

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Segment 3 Role of Power Electronics in Important
Utility Applications

• Distributed Generation (DG) ApplicationsPower
  electronic interface depends on the source
  characteristics

Wind Power Generation with Doubly Fed Induction
Motors
Photo-voltaics Interface
(c)
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Segment 3 Role of Power Electronics in Important
Utility Applications

• Power Electronic Loads Adjustable Speed Drives

(c)
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Segment 3 Role of Power Electronics in Important
Utility Applications

• Power Quality Solutions for
• voltage distortion
• unbalances
• voltage sags and swells
• power outages

(c)
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Segment 3 Role of Power Electronics in Important
Utility Applications

• Transmission and Distribution DC Transmission
• most flexible solution for connection of two ac
  systems

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Segment 3 Role of Power Electronics in Important
Utility Applications

• Transmission and Distribution Flexible AC
  Transmission Systems (FACTS)

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Segment 4 Discussion of Power Electronics
Interface

• Fundamental concepts for understanding the
  operation of the power electronic structures
• voltage-link systems
• current link systems
• solid state switches

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Voltage-Link Systems

• Unifying approach Power-Pole Building Block
• building block of all voltage-link systems

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Voltage-Link Systems

• Power conversion using Pulse Width Modulation
  (PWM)
• Power reversal with reversal of current direction
• Averaged conversion

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Voltage-Link Systems

• Averaged Representation of Power Pole
• Average quantities are of main interest

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Voltage-Link Systems

• Synthesis of AC voltages
• voltage to be synthesized
• duty ratio needed
• dc side current

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Voltage-Link Systems

• Implementation of bi-positional switch

(d)
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Current-Link Systems

• Exclusively thyristor based
• One of (T1, T2, T3) and (T2, T4, T6)conduct at a
  time
• Average dc voltage controlled by firing angle
• Power flow reversed by reversing voltage polarity

(d)
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Solid State Switch

• Can conduct current in both directions
• Turn-on or off in an ac circuit in one-half of a
  line-frequency cycle

(d)
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Conclusion

• Teaching utility applications of power
  electronics in a power systems course is very
  important
• A top down approach, starting with functional
  aspects and going to implementation details is
  suggested
• Topics outlined in the four segment proposed
  structure will introduce students to future
  practices and technologies in power engineering
• The proposed structure may be adapted based on
  individual preferences