• The Transactions of the Korean Institute of Electrical Engineers C
• /
• v.50 no.7
• /
• pp.329-333
• /
• 2001

The pulsed poser system has been widely used to many applications, such as E/P(Electrostatic Precipitator), DeNox/DeSOx power system, ozon generator, etc. A pulse energy efficiency for load depends on the rising time, peak value, pulse duration and impedance matching, etc. The pulse generator generally required for short pusle duration and high peak value was forced to consider its volume and economy. In this study, developing a compact pulse generator that applied for cascading method to be made of two pulse transformers, we compared cascading voltage with non cascading one by applying the pulse energy to load. Adopting cascading technique to pulse transformer, we found that average cascading voltage was about 60[%] of theoretical value. Maximum cascading ratio was calculated at 60 times compared with non cascading voltage.

• Journal of Electrical Engineering and Technology
• /
• v.10 no.6
• /
• pp.2240-2248
• /
• 2015

The integration of the large-scale wind power brings great challenge to the stability of the power grid. This paper investigates and studies the fault on May 14, 2012 of the large-scale cascading trip-off of wind turbines in North China. According to the characteristics of the voltage variation, the fault process is divided into three stages: the pre-event stage, the critical stage before cascading, and the cascading stage. The scenes in the fault are reproduced, using the full-size actual power system model. Simulation models of double-fed induction generators (DFIGs) and SVCs including protection settings and controller strategies are carefully chosen to find out the reason of voltage instability in each stage. Some voltage dynamic that have never been observed before in the faults of the same kind are analyzed in detail, and an equivalent voltage sensitive dynamic model of DFIG is proposed for the fast computation. The conclusions about the voltage dynamics are validated by the actual PMU observation evidence.

• Journal of the Korea Computer Industry Society
• /
• v.2 no.3
• /
• pp.363-368
• /
• 2001

This paper introduced cascading technique as a new technology composed of two pulse transformers and presented the experimental data and results. To obtain the stable pulse voltage adopted cascading technique, we designed and tested a compact pulse generator by adjusting the load resistors and input voltage. Adopting cascading technique to load, we found that average cascading voltage was about 62$\%$ of theoretical value. Cascading ratio was calculated at almost 19 compared with non cascading voltage.

• Journal of Power Electronics
• /
• v.4 no.2
• /
• pp.112-116
• /
• 2004

The pulsed power systems have been widely used many other countries and their new applications have been developed by many researchers, such as E/P(Electrostatic Precipitator) to remove the industrial dust, DeNOx/DeSOx power systems, ozone generators and power sources of the laser beam, etc. In this paper, we studied the cascading technique as a new technology consisted of two pulse transformers and obtained their experimental data and results. To obtain the high pulsed voltage adopted cascading technique, we designed our compact pulse generator and tested by adjusting the value of the load resistors to obtain high pulsed voltage with steep rising time and duration time. We explained their experimental results that obtained by adopting cascading technique. Also, we compared theoretical value with measured value obtained by using the cascading method.

• Proceedings of the KIEE Conference
• /
• 2000.07c
• /
• pp.1865-1867
• /
• 2000

The pulse power system has been widely used to many applications. such as E/P(Electrostatic Precipitator), DeNOx/DeSOx power system, ozon generator. etc. A pulse energy efficiency for load depend on the rising time, peak value, pulse duration, impedance matching. etc. The pulse generator generally required for short pulse duration, high peak value was forced to consider its size and economy. In this study, developing a compact pulse generator that applied for Cascading method to be made of two pulse transformer, we compared cascading voltage with no cascading one by applying the pulse energy to load.

• The Transactions of the Korean Institute of Electrical Engineers P
• /
• v.63 no.1
• /
• pp.1-6
• /
• 2014

An electric power system sometimes fails because of disturbances that occur unexpectedly, such as the uncontrolled loss of load that developed from cascading blackout. Which make stability through a little of under voltage load shedding should work. The development of phasor measurement unit(PMU) makes network supervision possible. The information obtained from PMU is synchronized by global positioning system(GPS). There are many real-time algorithms which are monitoring the voltage stability. This paper presents the study on the VILS(Voltage Instability Load Shedding) using PMU data. This algorithm computes Voltage Stability Margin Index(VSMI) continuously to track the voltage stability margin at local bus level. The VSMI is expressed as active and reactive power. The VSMI is used as an criterion for load shedding. In order to examine the algorithm is effective, applied to KEPCO system.

• Proceedings of the KIEE Conference
• /
• 2001.11b
• /
• pp.340-343
• /
• 2001

In an electrical network, electrical power are transmitted by a various of protection, isolation and control electric circuit devices. This thesis deals with the protection function between circuit-breakers. The protective coordination concerns the behaviour of two devices placed in series in an electrical network, with a short-circuit downstream circuit-breaker. It has two basic principles: First, discrimination which is an increasing requirement of low voltage electrical distribution systems. Second, which is less well known: cascading, which consists of installing a device, whose breaking capacity is less than the three-phase short-circuit current at its terminals and helped by main circuit-breaker. The important advantage of cascading is to be able to install at a branch circuit-breaker of a lesser performance without endangering the safety of the installation for more economical usage. To determine and guarantee co-ordination between two circuit breakers, it is necessary to carry out a theoretical approach, first, and then confirm the results by means of standard tests. This is illustrated in appendix A of IEC 947-2.

• Journal of Sensor Science and Technology
• /
• v.33 no.1
• /
• pp.12-17
• /
• 2024

Floating inverter amplifiers (FIAs) have recently garnered considerable attention owing to their high energy efficiency and inherent resilience to input common-mode voltages and process-voltage-temperature variations. Since the voltage gain of a simple FIA is low, it is typically cascaded or cascoded to achieve a higher voltage gain. However, cascading poses stability concerns in closed-loop applications, while cascoding limits the output swing. This study introduces a gain-enhanced FIA that features cross-coupled body biasing. Through simulations, it is demonstrated that the proposed FIA designed using a 28-nm complementary metal-oxide-semiconductor technology with a 1-V power supply can achieve a high voltage gain (> 90 dB) suitable for dynamic open-loop applications. The proposed FIA can also be used as a closed-loop amplifier by adjusting the amount of positive feedback due to the cross-coupled body biasing. The capability of achieving a high gain with minimum-length devices makes the proposed FIA a promising candidate for low-power, high-speed sensor interface systems.

• Journal of Electrical Engineering and Technology
• /
• v.13 no.1
• /
• pp.60-67
• /
• 2018

The presence of induction motor loads in a power system may cause the phenomenon of delayed voltage recovery after the occurrence of a severe fault. A high proportion of induction motor loads in the power system can be a significant influence on the voltage stability of the system. This problem referred to as FIDVR(Fault Induced Delayed Voltage Recovery) is commonly caused by stall of small HVAC unit(Heating, Ventilation, and Air Conditioner) after transmission or distribution system failure. This delayed voltage recovery arises from the dynamic characteristics associated with the kinetic energy of the induction motor load. This paper proposes the UVLS (Under Voltage Load Shedding) control strategy for dealing with FIDVR. UVLS based schemes prevent voltage instability by shedding the load and can help avoid major economic losses due to wide-ranging cascading outages. This paper review recent topic about under voltage load shedding and compare decentralized load shedding scheme with conventional load shedding scheme. The load shedding strategy is applied to an actual system in order to verify the proposed FIDVR mitigation solution. Simulations demonstrate the effectiveness of the proposed method in resolving the problem of delayed voltage recovery in the Korean Power System.

• KIEE International Transactions on Power Engineering
• /
• v.5A no.2
• /
• pp.144-151
• /
• 2005

This paper presents a framework for determining control strategies against unwanted tripping actions during relay operation that plays a very important role in cascading events leading to voltage collapse. The framework includes an algorithm for quick identification of possible zone 3 relay operation during voltage instability. Furthermore, it comes up with the control strategy of load shedding at the selected location with active power and relay margin criteria. In addition, Quasi Steady-State (QSS) simulation is employed to obtain time-related information that is valuable in the determination of control strategy. As a case study, an example applying the framework is shown with the modified New England 39-bus system.