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

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

2. 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

3. 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

4. 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)

5. 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

6. 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 (T&D) • High voltage dc (HVDC) and medium voltage dc • Flexible AC Transmission Systems (FACTS): Shunt and Series compensation, and the unified power flow controller

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

8. 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

9. 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)

10. Segment 3: Role of Power Electronics in Important Utility Applications • Power Electronic Loads: Adjustable Speed Drives (c)

11. Dynamic Voltage Restorers (DVR) Dual Feeders Uninterruptible Power Supplies Segment 3: Role of Power Electronics in Important Utility Applications • Power Quality Solutions for • voltage distortion • unbalances • voltage sags and swells • power outages (c)

12. HVDC MVDC Segment 3: Role of Power Electronics in Important Utility Applications • Transmission and Distribution: DC Transmission • most flexible solution for connection of two ac systems

13. Series Compensation Shunt Compensation Shunt and Series Compensation Segment 3: Role of Power Electronics in Important Utility Applications • Transmission and Distribution: Flexible AC Transmission Systems (FACTS)

14. 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

15. Voltage port Current port Voltage-Link Systems • Unifying approach: Power-Pole Building Block • building block of all voltage-link systems

16. Voltage port Current port Voltage-Link Systems • Power conversion using Pulse Width Modulation (PWM) • Power reversal with reversal of current direction • Averaged conversion

17. Voltage port Current port Voltage-Link Systems • Averaged Representation of Power Pole • Average quantities are of main interest

18. Voltage-Link Systems • Synthesis of AC voltages • voltage to be synthesized • duty ratio needed • dc side current

19. Voltage-Link Systems • Implementation of bi-positional switch (d)

20. 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)

21. 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)

22. 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