• Proceedings of the KIEE Conference
• /
• 2001.07a
• /
• pp.171-174
• /
• 2001

In this paper, an EMM(Equivalent Mechanical Model) is developed to explain the voltage collapse mechanism by reflecting the effects of reactive powers. The proposed EMM exactly represents the voltage instability mechanism described by the system equations. By the use of the EMM model the voltage collapse mechanism has been illustrated by showing the exactness of the results. It is also discussed a system transform in technique to eliminate the resistance component of the Thevenin equivalent impedance for practical applications.

• KIEE International Transactions on Power Engineering
• /
• v.12A no.1
• /
• pp.6-14
• /
• 2002

In this paper, an EMM(Equivalent Mechanical Model) Is developed to explain the voltage collapse mechanism by reflecting the effects of reactive powers. The proposed EMM exactly represents the voltage instability mechanism described by the system equations. By the use of the EMM model, the voltage collapse mechanism has been illustrated by showing the exactness of the results. The stable region has been investigated with a reactive-power-controlled two-bus system, which shows that special alerts are required when the system operates with leading power factor. It is also discussed a system transform technique to eliminate the resistance component of the Thevenin equivalent impedance for practical applications. Finally, the results adopting the proposed method fur sample systems which were transformed are listed

• Journal of Power Electronics
• /
• v.17 no.5
• /
• pp.1268-1277
• /
• 2017

Three-phase pulse width modulation (PWM) rectifiers are usually designed under the assumption of ideal ac power supply and input inductance. However, non-ideal circuit parameters may lead to a voltage collapse of PWM rectifiers. This paper investigates the mechanism of voltage collapse in three-phase PWM rectifiers. An analytical stability boundary expression is derived by analyzing the equilibrium point of the averaging state space model, which can not only accurately locate the voltage collapse boundary in the circuit parameter domain, but also reveal the essential characteristic of the voltage collapse. Results are obtained and compared with those of the trial-error method and the Jacobian method. Based on the analysis results, the system parameters can be divided into two categories. One of these categories affects the critical point, and other affects only the instability process. Furthermore, an effective control strategy is proposed to prevent a vulnerable system from being driven into the instability region. The analysis results are verified by the experiments.

• Proceedings of the KIEE Conference
• /
• 1995.11a
• /
• pp.110-112
• /
• 1995

Now days, voltage stability is well recognized as an important problem. It is well known that voltage stability is influenced by the characteristics of load. Up to present, voltage stability researches were done by the static load modeling, but it is needed that the precise analysis by the view point of dynamic load modeling. In this paper, with induction motor as dynamic load, I show the voltage collapse mechanism followed by load increase. Then I propose the protective method of voltage collapse by using TCSC.

• Journal of Adhesion and Interface
• /
• v.24 no.2
• /
• pp.60-63
• /
• 2023

The AlGaN/GaN heterostructure has high electron mobility due to the two-dimensional electron gas (2-DEG) layer, and has the characteristic of high breakdown voltage at high temperature due to its wide bandgap, making it a promising candidate for high-power and high-frequency electronic devices. Despite these advantages, there are factors that affect the reliability of various device properties such as current collapse. To address this issue, this paper used metal-organic chemical vapor deposition to continuously deposit AlGaN/GaN heterostructure and SiN passivation layer. Material and electrical properties of GaN HEMTs with/without SiN cap layer were analyzed, and based on the results, low-frequency noise characteristics of GaN HEMTs were measured to analyze the conduction mechanism model and the cause of defects within the channel.