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A

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AC-DC conversion

by Yee Wei Law - Monday, 12 February 2024, 2:36 PM
 
  • Single-phase: See 👇 attachment or the latest source on OneNote.
  • Three-phase: See 👇 attachment or the latest source on OneNote.

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Applications of control: examples

by Yee Wei Law - Wednesday, 5 July 2023, 8:39 AM
 
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Applications of power electronics: examples

by Yee Wei Law - Wednesday, 3 April 2024, 2:54 PM
 

From the computer we are now using to the Internet-of-Things devices that increasingly permeate our everyday reality (see Fig. 1); from variable speed drives (see Fig. 2) to renewable energy systems (see Fig. 3); from automobiles (see [BM11, Ch. 4], [Bad13, Sec. 3.4], [Ras18, Ch. 32]) to aircraft (see [KE01, WB14, SM15]); from particle accelerators (see Fig. 4) to satellites (see Fig. 5), power electronics is everywhere.

Wherever there is a need to electrically power a device or system in a certain way, there is a need for power electronics.

Fig. 1: The buck-boost DC-DC converter TPS63900A from Texas Instruments is marketed as a highly efficient product designed for Internet-of-Things (IoT) applications. Figure also shows a Texas Instruments medical/consumer wearable reference design [Tex20] for wireless ECG, SpO2, PTT and heart rate monitoring.

Fig. 2: A classic representative of an industrial power electronic system is a variable-speed drive (VSD) [Gey17, Ch. 1]. A well-known example of a medium-voltage VSD is ABB’s ACS 6000, as pictured above.

A VSD enables the operation of an electrical machine at an adjustable speed and at an adjustable torque. This is achieved by decoupling the grid electrically from the machine. Such a system consists of a step-down transformer connected to the grid, a rectifier, a DC link, an inverter, and an electrical machine driving a mechanical load.

The rectifier, which can be a diode rectifier or more commonly an active front end, converts the grid’s fixed-frequency AC quantities (at either 50 or 60 Hz) to DC quantities.

The DC link serves as an energy storage element, and decouples the rectifier from the inverter.

The inverter transforms the DC quantities back to AC at a variable frequency that is proportional to the rotational speed of the mechanical load.

Fig. 3: This example is about Kakosimos et al.’s highly cited work [KKM13] on maximum power point tracking (MPPT).

MPPT refers to the tracking of the maximum power point on the current-voltage curve associated with a photovoltaic (PV) system in order to extract maximum power from said system. Kakosimos et al. designed and developed an MPPT controller for the boost converter at the output of the solar panels.

Above, (a) shows the system setup, (b) shows the solar panels, (c) shows the boost converter hardware, and (d) shows the boost converter schematics in relation to the controller running on a TMS320F2812 Digital Signal Processor [KKM13, Figures 13-14].

Fig. 4: In high-energy physics experiments, the search for physically significant particle generation/disintegration events requires the capability of 1️⃣ detecting particle trajectories in real time, 2️⃣ applying predefined selection criteria to identify events of interest, and 3️⃣ storing all data related to the identified events of interest.

This capability imposes stringent performance requirements on the sensors and associated signal processing and control electronics. The operational frequency of these electronics depends on the event generation rate, which can be as high as several tens of MHz. The requirements are so demanding that all these electronics have to be located inside the sensor array for tracking particle trajectories and measuring their energy.

For large-scale experiments like the Large Hadron Collider experiments, the required number of sensors and associated electronic components is so large that it becomes impractical to supply power from outside the chamber through cables. The solution is point-of-load (POL) converters, i.e., DC-DC converters that are physically located as close as possible to their electrical load. This means the power supply circuits are located on the same boards where the signal processing and control electronics are located, i.e., inside the sensor array. The design of POL converters is challenging because of the size constraints and highly hostile environmental conditions (radiation, temperature, magnetic field) they operate in.

Fig. 5: VPT, Inc. provides power conversion solutions (e.g., radiation-tolerant DC-DC converters) for use in avionics, military, space, and industrial applications. Its products have been used in Japan’s Hayabusa-2 Mission, the United States’ GPS III SV03 satellite, and NASA’s Mars Perseverance Rover Mission.

Applications of power electronics are too many to list exhaustively, but most textbooks provide a list — check the bibliography at the end of each lecture!

Below, Table 1 has a list of applications taken from [Ras14, TABLE 1.1].

Table 1: Some applications of power electronics [Ras14, TABLE 1.1].

Those who are not content with Table 1 are encouraged to browse relevant journals, e.g.,

References

[Bad13] F. Badin, Hybrid Vehicles - From Components to System, Editions Technip, 2013. Available at https://app.knovel.com/hotlink/toc/id:kpHVFCS008/hybrid-vehicles-from/hybrid-vehicles-from.
[BM11] H. Bai and C. Mi, Transients of modern power electronics, Wiley, 2011. https://doi.org/10.1002/9781119971719.
[Gey17] T. Geyer, Model predictive control of high power converters and industrial drives, John Wiley & Sons, Ltd, 2017. https://doi.org/10.1002/9781119010883.
[KE01] M. D. Kankam and M. E. Elbuluk, A Survey of Power Electronics Applications in Aerospace Technologies, Technical Memorandum NASA/TM-2001-211298, IECEC2001-AT-32, NASA, November 2001. Available at https://ntrs.nasa.gov/citations/20020013943.
[KKM13] P. E. Kakosimos, A. G. Kladas, and S. N. Manias, Fast photovoltaic-system voltage- or current-oriented MPPT employing a predictive digital current-controlled converter, IEEE Transactions on Industrial Electronics 60 no. 12 (2013), 5673–5685. https://doi.org/10.1109/TIE.2012.2233700.
[Ras14] M. H. Rashid, Power Electronics: Devices, Circuits, and Applications, 4th ed., Pearson Education Limited, 2014. Available at https://ebookcentral.proquest.com/lib/unisa/detail.action?docID=5176110.
[Ras18] M. H. Rashid (ed.), Power Electronics Handbook, 4th ed., Butterworth-Heinemann, 2018. https://doi.org/10.1016/C2016-0-00847-1.
[SM15] B. Sarlioglu and C. T. Morris, More electric aircraft: Review, challenges, and opportunities for commercial transport aircraft, IEEE Transactions on Transportation Electrification 1 no. 1 (2015), 54–64. https://doi.org/10.1109/TTE.2015.2426499.
[Tex20] Texas Instruments, Wireless ECG, SpO2, PTT and Heart Rate Monitor Reference Design for Medical and Consumer Wearables, Design Guide: TIDA-01580 Rev. B, October 2020. Available at https://www.ti.com/tool/TIDA-01580.
[WB14] P. Wheeler and S. Bozhko, The more electric aircraft: Technology and challenges, IEEE Electrification Magazine 2 no. 4 (2014), 6–12. https://doi.org/10.1109/MELE.2014.2360720.

C

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Common mode

by Yee Wei Law - Saturday, 17 June 2023, 4:46 PM
 

There are two main types of electromagnetic interference (EMI), namely conducted emission and radiated emission.

Conducted emission can further be classified into two types, namely differential-mode noise and common-mode noise, as shown in Fig. 1.

Fig. 1: Differential-mode noise versus common-mode noise [ROH18].

For differential-mode noise, the noise source appears across power supply lines and is in series with the power supply line.

The noise current flows in the same direction as the power supply current.

Noise is so-called “differential-mode” because the outgoing and return currents are oppositely directed.

For common-mode noise, the noise current that has leaked via a stray capacitance or the like passes through ground and returns to the power supply line.

A noise voltage does not appear across the power supply lines.

Noise is so-called “common-mode” because the direction of the noise currents on the positive (+) and the negative (−) sides of the power supply have the same direction.

References

[ROH18] ROHM, Differential (normal) mode noise and common mode noise - causes and measures, Tech Web Basic Knowledge article, 2018. Available at https://techweb.rohm.com/knowledge/emc/s-emc/01-s-emc/6899.

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Control systems: introduction

by Yee Wei Law - Wednesday, 5 July 2023, 8:38 AM
 
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DC-DC step-down / buck conversion

by Yee Wei Law - Sunday, 20 August 2023, 12:24 AM
 
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DC-DC step-up / boost conversion and buck-boost conversion

by Yee Wei Law - Sunday, 20 August 2023, 12:25 AM
 
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Frequency response

by Yee Wei Law - Sunday, 27 August 2023, 10:16 PM
 
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G

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Galvanic isolation

by Yee Wei Law - Sunday, 18 June 2023, 9:09 PM
 

Those who have worked with high-voltage equipment before can readily appreciate the benefits of electrical isolation.

When two devices or circuits are in communication, DC currents and AC signals typically flow freely.

In low-voltage systems, this is a safe way for two parts of the system to work.

However, when high voltage enters into one or more parts of the system, freely-flowing DC current and some AC signals can cause errors, physical damage, and/or create hazardous conditions of operation [Tex20a].

A solution to this problem is galvanic isolation:

Definition 1: Galvanic isolation

A means of preventing DC and unwanted AC currents between two parts of a system while still allowing signal and power transfer between those two parts [Tex20a].

Alternative definitions:

  • IEC’s definition is high-level: “Arrangement within equipment that permits the transfer of signals or power between two circuits without any direct electrical connection between the two.”
  • IEEE’s definition [IEE14, p. 2] takes effort to interpret: “A method of electrical isolation where neither the signal nor the common of the output of the isolator is dc-coupled to the signal or common of the input of the isolator, except for low-level leakage associated with nonideal components.”

Galvanic isolation can help 1️⃣ protect human operators from electrical shocks, 2️⃣ prevent ground loops, and 3️⃣ improve noise immunity (and thus maintain signal integrity); see Fig. 1.

Fig. 1: Sample applications of galvanic isolation.

In Fig. 1,

  • A ground loop is a potentially detrimental loop formed when two or more points in an electrical system that are nominally at ground potential are connected by a conducting path such that not all points are at the same ground potential [IEE19, p. 91].
  • For improving noise immunity, an isolator with high common-mode transient immunity (CMTI) is necessary.

    CMTI is the maximum tolerable rate of rise or fall of the common-mode voltage applied between two isolated circuits [ZB18].

Isolator devices are available in three primary technologies as shown in Fig. 2: 1️⃣ optical, 2️⃣ inductive, and 3️⃣ capacitive.

Fig. 2: Three types of galvanic isolation: optical, inductive and capacitive.

Each technology uses a different insulator material with different dielectric strengths.

  • Dielectric strength is a measurement used to describe the maximum applied electric field, in volts per meter, that a material can withstand without undergoing electrical breakdown and becoming electrically conductive [Tex20a].

Here is how the technologies compare [Sch17, Tex20a]:

Optical isolators, also called opto-isolators or optocouplers, typically use air, epoxy or mold compound as the dielectric, which has a low dielectric strength.

These isolators have high immunity to electrical and magnetic noise, but their communication rate is limited by LED switching speed.

They also suffer from LED aging issues and higher power dissipation than other types of isolators.

Inductive/magnetic isolators typically use polyimide as the dielectric, which has a moderate dielectric strength.

These isolators enjoy a long lifetime, and their passive barrier can withstand surges/spikes much higher than their continuous voltage rating.

However, their inductive coupling via magnetic fields renders them susceptible to magnetic interference. Nevertheless, some new designs manage to certifiably overcome this susceptibility in industry standard tests.

Inductive isolation is the oldest among the three technologies.

Capacitive isolators typically use SiO2 as the dielectric, which has a high dielectric strength.

These isolators have high magnetic immunity, and can support a higher bandwidth than optical isolators.

However, their usage of electric fields for data transmission renders them susceptible to electrical interference.

Power converters are typically isolated using use either transformer or coupled inductor as shown in Fig. 3.

Fig. 3: General layouts of (a) nonisolated and (b) isolated converters [Bla18, FIG. 1.1].

Besides galvanic isolation, the isolator also serve the purpose of voltage level shifting, or providing multiple outputs [Bla18, Sec. 1.1.1].

However, nonisolated converters are often preferred in applications where galvanic isolation is not a necessity, because they are less bulky, less costly, more efficient and more reliable.

Example 1

Here is an example of an isolated DC-DC converter, the 700DNC40-12-xG, from Bel Power Solutions rated at 4 KW, suitable for use in hybrid and electric vehicles:

The topic of galvanic isolation can easily occupy an entire course if we really go into the details, but please take advantage of Texas Instruments’ “Introduction to isolation” video series as well as Digi-Key Electronics’ resources [Sch17, Bak18, Pin20].

References

[Bak18] B. Baker, How to isolate high voltages in single-supply industrial robotic systems, DigiKey Electronics article, 2018. Available at https://www.digikey.com/en/articles/how-to-isolate-high-voltages-industrial-robotic-systems.
[Bla18] F. Blaabjerg (ed.), Control of Power Electronic Converters and Systems, Academic Press, 2018. https://doi.org/10.1016/C2015-0-02427-3.
[IEE14] IEEE, IEEE Standard for Rail Transit Vehicle Event Recorders, IEEE Std 1482.1-2013 (Revision of IEEE Std 1482.1-1999), 2014. https://doi.org/10.1109/IEEESTD.2014.6756929.
[IEE19] IEEE, IEEE Recommended Practice for Monitoring Electric Power Quality, IEEE Std 1159-2019 (Revision of IEEE Std 1159-2009), 2019. https://doi.org/10.1109/IEEESTD.2019.8796486.
[Pin20] A. Pini, The basics of isolation transformers and how to select and use them, DigiKey Electronics article, 2020. Available at https://www.digikey.com/en/articles/the-basics-of-isolation-transformers-and-how-to-select-and-use-them.
[Sch17] B. Schweber, How to Select the Right Galvanic Isolation Technology for IoT Sensors, Digi-Key Electronics article, 2017. Available at https://www.digikey.com/en/articles/how-select-galvanic-isolation-technology-for-iot-sensors.
[Tex20a] Texas Instruments, Introduction to isolation: What is Galvanic Isolation?, TI video library, March 2020. Available at https://www.ti.com/video/6138482962001.
[ZB18] W. Zhang and M. Begue, Common Mode Transient Immunity (CMTI) for UCC2122x Isolated Gate Drivers, Application Report SLUA909, Texas Instruments, August 2018. Available at https://www.ti.com/lit/an/slua909/slua909.pdf.

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Heuristic tuning of controllers

by Yee Wei Law - Monday, 28 August 2023, 9:36 PM
 
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K

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Kalman filter

by Yee Wei Law - Sunday, 13 August 2023, 9:34 AM
 
See 👇 attachment: 1️⃣ l_kf.pdf for an introduction to the Kalman filter, 2️⃣ l_derivekf.pdf for a derivation of the Kalman filter.

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Modelling of power-electronic circuits and controller design

by Yee Wei Law - Tuesday, 26 September 2023, 3:22 PM
 
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PID control

by Yee Wei Law - Thursday, 10 August 2023, 8:44 AM
 
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Power-electronic devices: overview

by Yee Wei Law - Sunday, 10 September 2023, 3:31 PM
 
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Power electronics: introduction

by Yee Wei Law - Wednesday, 3 April 2024, 5:37 PM
 

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See also overview of power-electronic devices.


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Power transistors

by Yee Wei Law - Tuesday, 15 August 2023, 4:02 PM
 
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Stability

by Yee Wei Law - Sunday, 27 August 2023, 10:32 PM
 
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State-space equations

by Yee Wei Law - Sunday, 27 August 2023, 1:19 PM
 
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System dynamics and modelling

by Yee Wei Law - Tuesday, 26 September 2023, 3:28 PM
 

See 👇 attachment for modelling of linear system dynamics using differential equations, transfer functions and state-space equations.

State-space equations are covered in more details in a separate knowledge base entry.

Modelling of power-electronic circuits is covered in a separate knowledge base entry.

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Thyristors

by Yee Wei Law - Tuesday, 26 September 2023, 3:40 PM
 
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Time response

by Yee Wei Law - Sunday, 27 August 2023, 10:16 PM
 
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