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  1. 1. Teaching Utility Applications of Power Electronics in a First Course on Power Systems Ned Mohan, Amit Jain, Philip Jose University of Minnesota and Raja Ayyanar Arizona State University
  2. 2. OutlineImportance of teaching power electronics in a powersystems courseDescription of proposed approach consisting of foursegments 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 2
  3. 3. ImportanceIncreasing applications of Power ElectronicEquipment in Power Systems Availability of high power Control Center semiconductor devices Central Power Solar Power Plants Station Decentralized renewable  CHP House energy generation sources Combined Heat and Power Wind Power Plants Plant (CHP)  Village Increased power transfer Factory  Commercial with existing transmission Commercial Building House Building system Apartment Building Micro-Turbine Effective control of power Fuel Cell  Hospital  Commercial  Smart House flow needed in a  Performance Building deregulated environment Building Norms for Power quality Future Power System 3
  4. 4. ApproachTop 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) 4
  5. 5. Segment 1: Function of Power Electronics in Utility Applications Converter Source Load ControllerEnabling technology providing interface between two(ac/dc) electrical systemsE.g. Interconnection of two asynchronous ac systems dc to ac conversion is required to connect fuel cells or photovoltaics to the utility grid 5
  6. 6. Segment 1: Listing of Power Electronic ApplicationsDistributed generation (DG) Renewable resources (wind and photovoltaic) Fuel cells and micro-turbines Storage: batteries, super-conducting magnetic energy storage, flywheelsPower electronics loads: Adjustable speed drivesPower quality solutions Dual feeders Uninterruptible power supplies Dynamic voltage restorersTransmission and distribution (T&D) High voltage dc (HVDC) and medium voltage dc Flexible AC Transmission Systems (FACTS): Shunt and 6 Series compensation, and the unified power flow controller
  7. 7. 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 108 Thyristor Power (VA) IGCT 106 Thyristor IGCT IGBT 104 102 MOSFET 101 102 103 104 IGBT MOSFET Switching Frequency (Hz) 7
  8. 8. Segment 2: Structure of Power Electronic SystemsVoltage-Link Systems Transistors and diodes that can block voltage of only one polarity AC1 AC2Current-Link Systems higher power bipolar voltage- AC1 AC2 blocking capabilities of thyristorsSolid State Switches bidirectional voltage blocking and current conduction 8
  9. 9. Segment 3: Role of Power Electronics in Important Utility Applications Distributed Generation (DG) Applications Power electronic interface depends on the source characteristics Wound rotor Induction Generator Isolated PWM DC-DC Converter Converter AC DC Wind UtilityTurbine DC AC 1f Max. Power- Generator-side Grid-side point Tracker Converter Converter Wind Power Generation with Photo-voltaics Interface Doubly Fed Induction Motors 9
  10. 10. Segment 3: Role of Power Electronics in Important Utility Applications Power Electronic Loads: Adjustable Speed Drives Switch-mode Utility Converter Motor Rectifier Controller 10
  11. 11. Segment 3: Role of Power Electronics in Important Utility Applications Power Quality Solutions for voltage distortion unbalances Power Electronic Load Interface voltage sags and swells power outages Dynamic Voltage Restorers (DVR) Feeder 1 Critical Rectifier Inverter Filter Load Load Energy Feeder 2 Storage Dual Feeders Uninterruptible Power Supplies 11
  12. 12. Segment 3: Role of Power Electronics in Important Utility Applications Transmission and Distribution: DC Transmission most flexible solution for connection of two ac systemsAC1 AC2 AC1 AC2 HVDC MVDC 12
  13. 13. Segment 3: Role of Power Electronics in Important Utility Applications Transmission and Distribution: Flexible AC E1 E2 P= sin δ Transmission Systems (FACTS) X Series Compensation E2 E3 E1 E1 E3 E2 I - + jXUtility STATCOM Series Shunt converter converter Shunt Compensation Shunt and Series Compensation 13
  14. 14. Segment 4: Discussion of Power Electronics InterfaceFundamental concepts for understanding theoperation of the power electronic structures voltage-link systems current link systems solid state switches 14
  15. 15. Voltage-Link SystemsUnifying approach: Power-Pole Building Block building block of all voltage-link systems AC1 AC2 idA + iA d A Ts Voltage Vd port + Current vA - - port q A = 1 or 0 vcontrol PWM 15
  16. 16. Voltage-Link Systems Power conversion using Pulse Width Modulation (PWM) Power reversal with reversal of current direction idA + iA d A Ts Voltage vA VdVd vA port + Current vA t port d ATs - - Ts q A = 1 or 0vcontrol PWM Ton Averaged conversion vA = Vd = d AVd Ts 16
  17. 17. Voltage-Link Systems Averaged Representation of Power Pole Average quantities are of main interest idA idA + iA + iA d A Ts d A TsVd Voltag Vd + e + Current vA vA - port - port - - q A = 1 or 0 1: d Avcontrol PWM vcontrol PWM v A (t ) = d A (t ) × d V idA (t ) = d A (t ) ×iA (t ) 17
  18. 18. Voltage-Link SystemsSynthesis of AC voltages vA voltage to be synthesized Vd Vd ¶ v AN (t ) = + ∆V sin ω t Vd ¶ ∆v 2 2 duty ratio needed 0 ωt 1 ¶ iA d A = + ∆d sin ω t 2 $ I 0 ωt dc side current 1 ¶  φ i dA (t ) =  + ∆d sin ω t ÷× a (t ) i  2  1 ¶  ˆ =  + ∆d sin ω t ÷×I sin(ω t − φ ) 2  2 { 1ˆ ¶ ¶ } = I ∆d cos φ + sin(ω t − φ ) − ∆d cos(2ω t − φ ) 18
  19. 19. Voltage-Link Systems Implementation of bi-positional switch idA + qA d A Ts iA + iA VdVd - + vA - - q′ A q A = 1 or 0 q′ =1 −q A A 19
  20. 20. Current-Link SystemsExclusively thyristor based AC1 AC2 T1 One of (T1, T2, T3) and (T2, T4, T6) T3 conduct at a time T5 + ia Average dc voltage controlled by ‘firing angle’ La ib vd Id Lb 3 2 3 ic Vd = VLL cos α − ω Lc I d π π Lc T4 - Power flow reversed by reversing T6 voltage polarity T2 20
  21. 21. Solid State SwitchCan conduct current in both directionsTurn-on or off in an ac circuit in one-half of a line-frequencycycle 21
  22. 22. ConclusionTeaching utility applications of power electronics in apower systems course is very importantA top down approach, starting with functional aspectsand going to implementation details is suggestedTopics outlined in the four segment proposed structurewill introduce students to future practices andtechnologies in power engineeringThe proposed structure may be adapted based onindividual preferences 22