• Journal of Power Electronics
• /
• v.18 no.3
• /
• pp.853-862
• /
• 2018

Frequency coupling in the phase domain is a recently reported phenomenon for phase locked loop (PLL) based three-phase grid-inverter systems. This paper investigates the mechanism and stabilization method for the frequency coupling to the stability of grid-inverter systems. Self and accompanying admittance models are employed to represent the frequency coupling characteristics of the inverter, and a small signal equivalent circuit of a grid-inverter system is set up to reveal the mechanism of the frequency coupling to the system stability. The analysis reveals that the equivalent inverter admittance is changed due to the frequency coupling of the inverter, and the system stability is affected. In the end, retuning the bandwidth of the phase locked loop is presented to stabilize the three-phase grid-inverter system. Experimental results are given to verify the analysis and the stabilization scheme.

• The Transactions of the Korean Institute of Electrical Engineers D
• /
• v.54 no.6
• /
• pp.409-416
• /
• 2005

For broadband high-data-rate power line communication with the allocated frequency bandwidth from 2 to 30 MHz on medium voltage (MV) distribution power lines, a signal coupling unit is developed. The coupling unit is composed of a coupling capacitor for coupling communication signal, a drain coil, and an impedance matching part. The coupling capacitor made of ceramic capacitor is designed for transmission property of better than 1 dB in the frequency range. The drain coil is used for preventing low frequency high voltage from junction of medium voltage power line in case that a coupling capacitor is not working properly any more. Also, using ferrite core, a novel broadband impedance matching transformer is developed. A complete coupling unit with a coupling capacitor, a drain coil, and a matching transformer is housed by polymer for good isolation and distinguishing from high voltage electric facilities. Each is fabricated and its frequency behavior is tested. Finally, complete signal couplers are equipped in a MV PLC test bed and their performance are measured. The measurement shows that the coupling capacitor works excellently.

• IEIE Transactions on Smart Processing and Computing
• /
• v.4 no.3
• /
• pp.149-151
• /
• 2015

Coupling with a ring of capacitors introduces in-phase coupling current in multi-stage LC oscillators, increasing coupling strength and phase spacing accuracy. Capacitive coupling is effective at high-frequency applications because it increases coupling strength with the operating frequency. However, capacitive loading from the ring lowers operating frequency and reduces the tuning range. Mathematical expressions of phase noise and phase spacing accuracy with capacitive coupling are examined here, and transistor-level simulations confirm the effectiveness of the capacitive coupling.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.18 no.9
• /
• pp.2245-2250
• /
• 1994

The normal coordinates of a nonclassically damped systems are coupled by nonzero off-diagonal elements of modal damping matrix. The relationship between modal coupling and the frequency separation of the natural modes is presented in this paper. Contrary to widely accepted beliefs, increasing the frequency separation of the natural modes does not neccessarily diminish the effect of modal coupling. Consequently, in the pratical engineering applications, wide frequency separation of the natural modes would not be sufficient for neglecting modal coupling.

• Journal of the Korean Ceramic Society
• /
• v.23 no.6
• /
• pp.66-70
• /
• 1986

The calcining temperature ranging from 900$^{\circ}C$ to 1300$^{\circ}C$ affected on the planar coupling factor and resonance characteristics of BaTiO3 ceramics doped with 0.2 wt% MnO2 have been investigated. Dielectric constant planar coupling factor and anti-resonance frequency of the sample increased with the calcining temperature up to 1,200$^{\circ}C$ and decreased above that temperature but the resonance frequency decreased slightly with the increasing calcining temperature. The planar coupling factor and anti-resonance frequency increased with the sintered density and dielectric constant while the resonance frequency was almost constant. The resonance and anti-resonance frequency increased with the sample temperature.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.21 no.2
• /
• pp.111-116
• /
• 2016

This paper proposes a high-frequency (MHz) LLC resonant converter for a capacitor coupling wireless power transfer (CCWPT). The CCWPT uses electric field in the coupling capacitor between the transmitter and receiver electrodes with a dielectric layer. Given that capacitance is very small and the impedance is large, transferring power with a simple series resonance is difficult. Therefore, the high frequency (MHz) and high Q factor LLC converter is proposed to reduce the impedance of the coupling capacitance and to obtain a high output voltage. This paper deals with the operation analysis of the proposed LLC converter and a theoretical capacitance estimation. The operation and features of the proposed CCWPT LLC converter is verified with a 4.2 W prototype for charging mobile devices.

• Journal of Power Electronics
• /
• v.16 no.5
• /
• pp.1678-1688
• /
• 2016

This paper presents a capacitive power transfer (CPT) system using a Class-E resonant inverter. A Class-E resonant inverter is chosen because of its ability to perform DC-to-AC inversion efficiently while significantly reducing switching losses. The proposed CPT system consists of an efficient Class-E resonant inverter and capacitive coupling formed by two flat rectangular transmitter and receiver plates. To understand CPT behavior, we study the effects of various coupling distances on output power performance. The proposed design is verified through lab experiments with a nominal operating frequency of 1 MHz and 0.25 mm coupling gap. An efficiency of 96.3% is achieved. A simple frequency tracking unit is also proposed to tune the operating frequency in response to changes in the coupling gap. With this resonant frequency tracking unit, the efficiency of the proposed CPT system can be maintained within 96.3%-91% for the coupling gap range of 0.25-2 mm.

• Proceedings of the KIEE Conference
• /
• 2004.11a
• /
• pp.40-42
• /
• 2004

This paper describes a method to find an optimal driving condition of vibratory gyroscope. Mechanical coupling between driving and sensing mode degrades the performance of vibratory gyroscope. When the resonant frequencies of driving and sensing parts are fixed, frequency and amplitude of driving source affect mechanical coupling. Thus, they should be optimally tuned. To investigate the influence of driving source on mechanical coupling, we measured frequency response and displacement of driving and sensing mode using laser vibromenter. The measured frequency response and displacement show that the gyroscope has minimum mechanical coupling when the frequency of driving source is set to the intermediate value of driving and sensing part resonant frequency. Measurement also shows that the mechanical coupling increases abruptly at a certain driving voltage as the voltage increases.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2002.07a
• /
• pp.123-126
• /
• 2002

A proposed multi-layer ceramic (MLC) chip type band-pass filter (BPF) is presented. The MLC chip BPF has the benefits of low cost and small size. The BPF consists of coulped stripline resonators and coupling capacitors. The BPF is designed to have an attenuation pole at below the passband for a receiver band of IMT-2000 handset. The computer-aided design technology is applied for analysis of the BPF frequency characteristics. The passband and attenuation pole depend the coupling between resonators and coupling capacitance. The frequency characterics of the passband and attenuation pole are analysed with the variance of the coupling between resonators and coupling capacitance. An equivalent circuit and structure of MLC chip BPF are proposed. The frequency characteristics of the BPF is well acceptable for IMT-2000 application.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.16 no.8
• /
• pp.740-743
• /
• 2003

A multi-layer ceramic (MLC) chip type band-pass filter (BPF) is presented. The MLC chip BPF has the benefits of low cost and small size. The BPF consists of coulped stripline resonators and coupling capacitors. The BPF is designed to have an attenuation pole at below the passband for a receiver band of IMT-2000 handset. The computer-aided design technology is applied for analysis of the BPF frequency characteristics. The passband and attenuation pole depend on the coupling between resonators and coupling capacitance. The frequency characterics of the passband and attenuation pole are analyzed with the variation of the coupling between resonators and coupling capacitance. An equivanlent circuit and structure of MLC chip BPF are proposed. The frequency characteristics of the BPF is well acceptable for IMT-2000 application.