Seung-Soo Choi

A novel reclosing and rebreaking DC solid state circuit breaker

There is no zero crossing of the current in DC power circuits. Thus unless you cut off the short-circuit current quickly, the electrical fire caused by electric arc or spark can occur. And after the initial fault breaking operation the long-duration sustained interruption without fault recovery may cause a lot of serious economic losses. Therefore this paper proposes a new DC SSCB that has quick reclosing and rebreaking capabilities, and thus can perform the operating duties of reclosing and rebreaking required by the industrial standards and regulations. The proposed DC SSCB can perform rapid breaking, thus the material costs of power facilities can be reduced as the rapid breaking of DC SSCB enables selecting lower specification devices and minimizing auxiliary SCR. Also it can perform the operating duty of reclosing and rebreaking even in the state that short circuit lasts on load side. The operating characteristics of the proposed SSCB are verified by simulations and experiments on short circuit fault.

New DC Solid State Circuit Breaker with reclosing and rebreaking capabilities

Recently according to the development of DC transmission which is high efficiency, stability of DC grid has become a major concern. Therefore, the reliable DC SSCB (Solid-State Circuit Breaker) is required in order to secure high safety. The previous DC SSCB is unstable and many elements are required in order to perform the operating duty. This paper proposes a new DC SSCB. Since the proposed DC SSCB does not cause delay of breaking operation caused by charging operation, it can break an accident quickly. Also, since it can perform the operation duty with a few elements, it is economical. The operating characteristic of the proposed DC SSCB is verified by simulations on short circuit fault. Also, this paper suggests the design guidelines so that it can be applied to any other DC grid.

A New Reclosing and Re-breaking DC Thyristor Circuit Breaker for DC Distribution Applications

The DC circuit breaker is essential for supplying stable DC power with the advent of DC transmission/distribution and sensitive loads. Compared with mechanical circuit breakers, which must interrupt a very large fault current due to their slow breaking capability, a solid-state circuit breaker (SSCB) can quickly break a fault current almost within 1 [ms]. Thus, it can reduce the damage of an accident a lot more than mechanical circuit breakers. However, previous DC SSCBs cannot perform the operating duty, and are not economical because many SCR are required. Therefore, this paper proposes a new DC SSCB suitable for DC grids. It has a low semiconductor conduction loss, quick reclosing and rebreaking capabilities. As a result, it can perform the operating duties of reclosing and rebreaking. The proposed DC SSCB is designed and implemented so that it is suitable for home dc distribution at a rated power of 5 [kW] and a voltage of 380 [V]. The operating characteristics are confirmed by simulation and experimental results. In addition, this paper suggests design guidelines so that it can be applied to other DC grids. It is anticipated that the proposed DC SSCB may be utilized to design and realize many DC grid systems.

A Novel AC Solid-State Circuit Breaker with Reclosing and Rebreaking Capability

These days, the widespread use of sensitive loads and distributed generators makes the solid-state circuit breaker (SSCB) an essential component in power circuits to achieve a high power quality for AC Grids. In traditional AC SSCB using SCRs, some auxiliary mechanical devices are required to make the reclosing operation possible before fault recovery. However, the proposed AC SSCB can break quickly and then be reclosed without auxiliary mechanical devices even during the short-circuit fault. Moreover, its fault current breaking time is short and its SSCB reclosing operation is fast. This results in a reduction of the economic losses due to fault currents and power outages. Through simulations and experiments on short-circuit faults, the performance characteristics of the proposed AC SSCB are verified. A design guideline is also suggested to apply the proposed AC SSCB to various AC grids.

Design of variable output voltage power supply for power amplifier of underwater acoustic sensor

The paper proposes a new multilevel variable output voltage AC/DC Converter for power supply of power amplifiers used in underwater acoustic sensors. The proposed multilevel variable output voltage AC/DC Converter is composed of two converter sections. One as the input section is a high efficiency phase-shifted PWM full bridge DC-DC converter to get multiport power sources. The other as the output section is composed of two flying-capacitor 3-level DC-DC converters and a diode bridge circuit to get fast-response and multilevel variable output voltage for an envelope amplifier. The paper suggests the detailed circuit topology and design guideline of multilevel variable output voltage AC/DC converter. It also proposes the power balanced control method between 3-level converters and the voltage balanced algorithm for flying capacitors. Its characteristics should be verified by the detailed simulation results. It is anticipated that the proposed converter will work very well for power amplifiers used in underwater acoustic sensors.

A novel reclosing and rebreaking AC thyristor circuit breaker

These days, widespread use of sensitive loads and distributed generators makes solid-state circuit breaker (SSCB) an essential component in power circuits to achieve a high power quality for AC Grids. In the case of previous AC SSCB using SCRs, some auxiliary mechanical devices are required to make the reclosing operation possible before fault recovery. However, the proposed AC SSCB can break quickly and then be reclosed without auxiliary mechanical devices even while the short-circuit fault lasts. Moreover, its fault current breaking time is short and its SSCB reclosing operation is fast, thus resulting in the reduction of economic losses due to fault currents and power outages. Through simulations and experiments of the short-circuit faults, the performance characteristics of the proposed AC SSCB are verified. The design guideline is also suggested to apply the proposed AC SSCB for various AC grids.

Design of compact and high-efficiency power supply and power amplifier for parametric array transducer

Parametric array transducers are used for highly directional speaker in an air environments. The power amplifiers for them should have sufficient linear output characteristic to amplify high-frequency ultrasonic waves with low THD, and also have high efficiency to avoid system heating and fuel problems. Piezoelectric micromachined ultrasonic transducers for parametric array transducers need DC-biased voltage driving signals in order to get high-directional quality-sound features. The existing power amplifier such as class A amplifiers has low efficiency and require large volume heatsinks. To overcome the above-mentioned disadvantages of the conventional amplifier, this paper proposes a new power amplifier and also its power supply. The proposed power amplifier system ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier, and furthermore gets high efficiency by providing the DC-DC converter-type power supply of energy recovery feature as well as applying the peak envelope tracking technique. Also the paper suggests the detailed circuit topology. Its characteristics are verified by the detailed experimental results.

Comparison on current source rectifier and inverter topologies of induction heating power supply for forging applications

Induction heating can convert electrical energy to thermal energy with high conversion efficiency and quick heating. Currently, a current source rectifier/inverter-fed parallel resonant circuit is widely used as an induction heating power supply for forging applications. However, the conventional induction heating power supplies composed of phase-controlled rectifier and SCR inverter have low efficiency and low power factor at input side, and require additional starting circuitry. So this paper proposes new induction heating power supply topologies for forging applications which have high power factor, high efficiency, and large output power, and compares their characteristics and performances.

Design of multi-level output voltage power supply for high-efficiency linear power amplifier

Parametric array transducers are used for long-range and highly directional communication in underwater environment. The power amplifiers for parametric array transducers should have sufficient linear output characteristic and high efficiency to avoid communication errors, system heating, and fuel problems. But the conventional power amplifier with fixed source voltage is very low efficient due to large power loss by the big difference between the fixed source voltage and the amplifier output voltage. Thus to solve the problems this paper proposes a new multilevel variable output voltage AC/DC Converter for power supply of power amplifiers used in underwater acoustic sensors. The proposed multilevel variable output voltage AC/DC Converter is composed of two parts. One as the input section is the high efficiency phase-shifted PWM full bridge DC-DC converter to get multiport power sources. The other as the output section is composed of two flying-capacitor 3-level DC-DC converters and a diode bridge circuit to get fast-response and multilevel variable output voltage for an envelope amplifier. Also the paper proposes the power balanced control method between 3-level converters and the voltage balanced algorithm for flying capacitors. Its characteristics should be verified by the detailed simulation results. It is anticipated that the proposed converter will be used very well for power amplifiers used in underwater acoustic sensors.

Design of high-efficiency power amplifier system for high-directional speaker

Parametric array transducers are used for highly directional speaker in an air environments. Piezoelectric micromachined ultrasonic transducers for parametric array transducers need DC-biased voltage driving signals in order to get high-directional quality-sound features. The existing power amplifier such as class A amplifiers has low efficiency and require large volume heatsinks. To overcome the above-mentioned disadvantages of the conventional amplifier, this paper proposes a new power amplifier system. The proposed power amplifier system ensures high linearity of output characteristic by utilizing the push-pull class B type amplifier. Furthermore, the proposed power amplifier system gets high efficiency because it contains the matching circuit and the DC-DC converter-type power supply which can perform energy recovery and envelope tracking function. Also the paper suggests the detailed circuit topology. Its characteristics are verified by the detailed experimental results.