Transients of Modern Power Electronics

Hua Bai, Chris Mi

• Publisher: Wiley
• Year: 2011
• ISBN:
  9781119972761
• Edition: 1
• Topic: Technology & Engineering
• Subtopic: Power Resources
• Index: Technology & Engineering

In high power, high voltage electronics systems, a strategy to manage short timescale energy imbalances is fundamental to the system reliability. Without a theoretical framework, harmful local convergence of energy can affect the dynamic process of transformation, transmission, and storage which create an unreliable system.

With an original approach that encourages understanding of both macroscopic and microscopic factors, the authors offer a solution. They demonstrate the essential theory and methodology for the design, modeling and prototyping of modern power electronics converters to create highly effective systems. Current applications such as renewable energy systems and hybrid electric vehicles are discussed in detail by the authors.

Key features:

• offers a logical guide that is widely applicable to power electronics across power supplies, renewable energy systems, and many other areas
• analyses the short-scale (nano-micro second) transient phenomena and the transient processes in nearly all major timescales, from device switching processes at the nanoscale level, to thermal and mechanical processes at second level
• explores transient causes and shows how to correct them by changing the control algorithm or peripheral circuit
• includes two case studies on power electronics in hybrid electric vehicles and renewable energy systems

Practitioners in major power electronic companies will benefit from this reference, especially design engineers aiming for optimal system performance. It will also be of value to faculty staff and graduate students specializing in power electronics within academia.

Chapter 1

Power Electronic Devices, Circuits, Topology, and Control

1.1 Power Electronics

Power electronics is a branch of engineering that combines the generation, transformation, and distribution of electrical energy through electronic means. In 1974, W. Newell described power electronics as a combination of electrical engineering, electronics, and control theory, which has been widely accepted today [1].

Power electronics has merged into various residential, commercial, and industrial domains. Application of power electronics encompasses renewable energy, transportation, defense, communication, manufacturing, utilities, and appliances. In the renewable energy field, power electronics covers distributed generation, control of electric power quality, wind power generation, and solar energy conversion. Modern power electronics consists of the research and development of novel power electronic semiconductors, new topologies, and new control algorithms. Power electronics is an interdisciplinary subject that involves traditional electrical engineering, electromagnetics, microelectronics, control, thermal fluid dynamics, and computer science.

More specifically, research in power electronics includes but is not limited to:

1. Theory, manufacture, and application of power electronic semiconductor devices.

2. Power electronic circuits, devices, systems and their relevant modeling, simulation, and computer-aided design.

3. Prediction and improvement of system reliability.

4. Motor drive design, traction, and automation control.

5. Techniques for electromagnetic design and measurement.

6. Power electronics-based flexible AC transmission systems (FACTSs).

7. Advanced control techniques.

The study of power semiconductor devices is the foundation of modern power electronics. It began with the introduction of thyristors in the late 1950s. Today there are several types of power semiconductor devices available for power electronics applications, including gate turn-off thyristors (GTOs), power Darlington transistors, power metal oxide semiconductor field effect transistors (MOSFETs), insulated-gate bipolar transistors (IGBTs), and integrated-gate commutated thyristors (IGCTs). Recently, new materials with wideband energy gaps, such as silicon carbide (SiC) and gallium arsenide (GaS), are leading the direction of next-generation power semiconductor devices.

With the development of computer science and control theory, power electronics began to be utilized for industrial applications, for instance in motor drive and traction applications. Various remarkable control algorithms, such as field-oriented control (FOC) and direct torque control (DTC), have been developed for induction motor drives and permanent magnet motor drives [2–5].

With the development of power electronic technology, especially the maturity of high-voltage and high-power semiconductors, power electronics began to play an active role in power systems, improving their performance, cost, and controllability. FACTS is a typical example of power electronics in power system applications. The static reactive-power compensator (STATCOM) can eliminate excessive reactive power in the system so as to make the local power system more robust, environmentally friendly, and flexible [6–8].

Power supply is another area for the most popular power electronics applications. Spanning a wide range of power ratings, from ultralow power of a few milliwatts to several megawatts, and from a few volts to more than a thousand volts, power supplies based on power electronics occupy a large amount of market share. DC–DC converters [9], DC–AC inverters [10], AC–DC rectifiers [11], and AC–AC cyclo-converters [12] are typical of this field. Research in these power electronic technologies helps diversify topologies and the control methods. Furthermore, all of these topologies can be mathematically described, modeled, and simulated. For example, in order to mitigate thermal generation by the switching losses in hard-switched converters, soft-switching techniques were developed where nearly all circuits have their own unique topology mathematically modeled according to their own operation modes [13–17]. Advanced control algorithms and diverse topologies can all be validated through the use of sophisticated analytical and numerical analysis tools, especially after the feasibility and accuracy of such tools have been validated widely in consumer and industrial applications.

1.2 The Evolution of Power Device Technology

Power semiconductors are the fundamental building blocks of power electronics. Each generation of semiconductors determines its corresponding generation of power electronic technology. The first power electronic device ever created was the mercury arc rectifier in 1900. The grid-controlled vacuum rectifier, ignitron, and thyratron followed later. These devices were found in numerous applications in industrial power control until 1950. At this time, the invention of the transistor in 1948 marked a revolution in the field of electronics. It also paved the way for the introduction of the silicon-controlled rectifier, announced by General Electric in 1957, commonly known nowadays as the thyristor.

All of these semiconductor devices can be classified as the following three types:

1. Uncontrolled devices: devices that do not need any trigger signals to control their on/off action, such as a rectifying diode.

2. Semi-controlled devices: devices that can be triggered on but cannot be turned off through control signals. A typical example is a thyristor, where the only way to turn it off is to reverse the polarity of the voltage across it and wait until the current reaches zero.

3. Fully controlled devices: also known as self-controlled devices, these devices can be turned on and off by the gate signals. Typical examples include bipolar junction transistors (BJTs), IGBTs, MOSFETs, GTOs, and IGCTs.

The common aspects of thyristors and GTOs are their high power ratings (most recently reaching over 6000 V/6000 A) and slow switching speed. They have always been the primary choice in high-voltage and high-power inverters (voltage source or current source inverters) until IGCTs emerged. Due to their slow switching speed, the switching frequency of thyristors and GTOs cannot be too high, otherwise a large switching loss will eventually damage the device. In medium-voltage applications, thyristors and GTOs have been replaced by high-voltage IGBTs or IGCTs. However, in high-voltage DC applications, thyristors and GTOs still dominate.

BJTs and MOSFETs were developed simultaneously in the late 1970s. BJTs are current-controlled devices while MOSFETs are voltage-controlled devices. Power BJTs have gradually been phased out while MOSFETs and IGBTs have become dominant in power electronics, especially in low- to medium-power applications. Compared to BJTs, MOSFETs can operate at higher switching frequencies while having lower switching losses. The only disadvantage of MOSFETs is their higher on-state voltage compared to that of IGBTs.

An IGBT is basically a combination of a BJT and a MOSFET [18]. It has been an important milestone in the history of power semiconductor devices. Its switching frequency can be much higher than that of BJTs, and its electrical capabilities are much higher than those of MOSFETs. Currently, IGBTs can reach 6000 V/600 A or 3500 V/1200 A. The operational details of IGBTs will be further explained in the next few chapters.

IGCTs were introduced by ABB in 1997 [19]. Presently they can reach 4500 V/4000 A. Essentially, a gate-controlled thyristor (GCT) is a four-layer thyristor, being simple to turn on but difficult to turn off. However, with the introduction of “integrated gates,” the turn-off process is accelerated by shifting all the current from the GCT to its gate. Therefore, in the turn-off process, an IGCT behaves as a transistor. The advantages of IGCTs over GTOs include: faster switching, uniform temperature distribution within the junction, and snubber-free operation. One of the IGCT's disadvantages is that a short circuit is formed across its terminals during failure, which is not desirable in most power electronics applications.

Power semiconductor device development now extends beyond just semiconductor design. With the increase in various power electronics applications, more and more power devices tend to integrate gate-drive circuits, overcurrent protection, and other additional functions inside the module. Thus intelligent power modules (IPMs) have emerged for up to several hundred kilowatts for IGBTs [20]. IGCTs are typical IPMs. An IGCT integrates the gate with a GCT. Some types of IGCTs can even process self-diagnosis and feed back their status to the microcontroller.

The above semiconductors are silicon based. It is expected that in the future silicon devices will still keep th...

Table of contents

• Cover
• Title Page
• Copyright
• About the Authors
• Preface
• Chapter 1: Power Electronic Devices, Circuits, Topology, and Control
• Chapter 2: Macroscopic and Microscopic Factors in Power Electronic Systems
• Chapter 3: Power Semiconductor Devices, Integrated Power Circuits, and their Short-timescale Transients
• Chapter 4: Power Electronics in Electric and Hybrid Vehicles
• Chapter 5: Power Electronics in Alternative Energy and Advanced Power Systems
• Chapter 6: Power Electronics in Battery Management Systems
• Chapter 7: Dead-band Effect and Minimum Pulse Width
• Chapter 8: Modulated Error in Power Electronic Systems
• Chapter 9: Future Trends of Power Electronics
• Index