• 조명전기설비학회논문지
• /
• 제28권1호
• /
• pp.96-104
• /
• 2014

The all pass filter generates a virtual q-axis voltage component with $90^{\circ}$ phase delay but the virtual q-axis voltage cannot detect the voltage depending on the phase of the grid voltage. To overcome the problem, q-axis voltage component is generated from difference between the current and previous value of d-axis voltage component in the stationary reference frame. However, the difference voltage between the current and previous value around the zero crossing voltage is not enough to detect the voltage sag. Therefore, the new detection scheme which can detect the sag around the zero crossing voltage is proposed.

• 조명전기설비학회논문지
• /
• 제28권12호
• /
• pp.65-73
• /
• 2014

In this paper, the detection scheme of the voltage variation using a two difference voltage is proposed. The conventional sag detector is from a single-phase digital phase-locked loop (DPLL) that is based on a d-q transformation using an all-pass filter (APF). The APF generates a virtual q-axis voltage component with $90^{\circ}$ phase delay but the APF cannot generate the virtual q-axis voltage depending on the phase of the grid voltage. To overcome the problem, q-axis voltage component is generated from difference between the current and previous value of d-axis voltage component in the stationary reference frame. However, the difference voltage around the zero crossing is not enough to detect the voltage sag. Therefore, the new detection scheme using the two difference voltage which can detect the sag around the zero crossing voltage is proposed.

• Journal of Power Electronics
• /
• 제17권1호
• /
• pp.1-10
• /
• 2017

This paper presents a novel predictive digital control method for boundary conduction mode PFC converters without the need for detecting the inductor current. In the proposed method, the inductor current is predicted by analytical equations instead of being detected by a sensing-resistor. The predicted zero-crossing point of the inductor current is determined by the values of the input voltage, output voltage and predicted inductor current. Importantly, the prediction of zero-crossing point is achieved in just a single switching cycle. Therefore, the errors in predictive calculation caused by parameter variations can be compensated. The prediction of the zero-crossing point with the proposed method has been shown to have good accuracy. The proposed method also shows high stability towards variations in both the inductance and output power. Experimental results demonstrate the effectiveness of the proposed predictive digital control method for PFC converters.

• Journal of Power Electronics
• /
• 제19권1호
• /
• pp.278-287
• /
• 2019

In this study, a zero-crossing spike current issue in a totem-pole bridgeless power factor correction (PFC) converter is comprehensively investigated for the first time. Spike current occurs when input voltage crosses zero, becomes a noise source, and causes severe common mode emission issues. A generation mechanism for electromagnetic interference (EMI) is presented to investigate the EMI problem caused by zero-crossing issue, and a noise spectrum due to this issue is predicted by a theoretical analysis based on the Fourier coefficient of an approximate spike current waveform. Furthermore, a noise reduction method is proposed and then improved to reduce the spike current. Experimental measurements are implemented on a GaN-based totem-pole bridgeless PFC converter, and the spike current can be effectively suppressed through the proposed method. Furthermore, the noise spectrums measured without and with the reduced zero-crossing spike current are compared. Experimental results validate the analysis of the noise spectrum caused by the zero-crossing spike current issue.

• 한국철도학회:학술대회논문집
• /
• 한국철도학회 2010년도 춘계학술대회 논문집
• /
• pp.564-570
• /
• 2010

Last train of the vehicle for eht energy saving and improved performance PWM converters ares widely used. In the case of PWM converters by the zero detection system performance depends on whether it can be argued. Zero voltage detectio method of the hardware and software approach is to in this paper, the zero detection methods for hardware and software problems that have occured as a complemnetary technique was expained.

• 한국초전도ㆍ저온공학회논문지
• /
• 제20권4호
• /
• pp.55-59
• /
• 2018

Currently, the development of industry makes needs larger electric supply. Providers must consider the efficiency about losses and reliability of the system. In this case, DC power system can save electrical energy; long-distance transmission line losses. Relevance to switch technology with a voltage-source converter (VSC) in AC-DC conversion system have been researched. But, protection device of DC-link against fault current is still needed to study much. VSC DC power system is vulnerable to DC-cable short-circuit and ground faults, because DC-link has a huge size of capacitor filter which releases extremely large current during DC faults. Furthermore, DC has a fatal flaw that current zero crossing is nonexistence. To interrupt the DC, several methods which make a zero crossing is used; parallel connecting self-excited series LC circuit with main switch, LC circuit with power electronic device called hybrid DC circuit breaker. Meanwhile, self-excited oscillator needs a huge size capacitor that produces big oscillation current which makes zero crossing. This capacitor has a quite effective on the price of DCCB. In this paper, hybrid self-excited type superconducting DCCB which are using AC circuit breaker system is studied by simulation tool PSCAD/EMTDC.

• 전력전자학회논문지
• /
• 제27권2호
• /
• pp.134-141
• /
• 2022

This study presents a method for reducing current distortion that occurs when a dual-buck inverter generates reactive power. Dual-buck inverters, which are only capable of unity power factor operation, can generate reactive power capabilities by modifying a modulation technique. However, under non-unity power factor conditions, current distortion occurs at zero-crossing points of grid voltage and output current. This distortion is caused by parasitic capacitors, dead-time, and discontinuous conduction mode operation. This study proposes a modified modulation method to alleviate the current distortion at zero-crossing point of the grid voltage. A repetitive controller is applied to reduce this distortion of the output current. A 1 kVA prototype is built and tested. Simulation and experimental results demonstrate the effectiveness of the proposed method.

• 한국인터넷방송통신학회논문지
• /
• 제20권4호
• /
• pp.143-148
• /
• 2020

교류 전압의 위상을 검출하여 제어하는 시스템의 경우 아날로그 제어방식에서는 검출한 위상에 대해 필터링에 의한 위상 offset 부분을 보상하여 제어에 응용하고 있다. 그러나, 디지털 제어방식에서는 이러한 위상 검출을 이용하여 제어할 경우 마이크로프로세서 혹은 마이크로 컨트롤러의 동작 주파수와 입력 위상 시간과의 오차로 인하여 정밀한 제어를 이룰 수가 없다. 일반적으로 사용하는 방식이 일정한 시간이 되면 누적된 오차를 임의로 보상하여 맞추어주는 방식인데 이러한 경우 보상하기 전까지는 오차를 지속적으로 가지고 갈 수밖에 없는 상황이 발생하게 된다. 이러한 문제점을 해결하기 위해서는 실시간으로 영점을 검출하여 마이크로프로세서의 동작 주파수에 맞도록 보상하는 방법이 필요하게 된다. 따라서 이러한 오차를 줄이면서 정밀한 디지털 제어에 응용하기 위해 본 논문에서 수행하고자 하는 연구는 다음과 같다. 1) 시뮬레이션 모델링을 통해 Zero Crossing Detection 알고리즘을 구현하여 영점을 검출을 통하여 동작 주파수에 맞도록 보상하는 방법에 관해 연구. 2) Microcontroller를 이용한 Zero Crossing Detection 설계를 통하여 실시간으로 영점을 검출하여 마이크로프로세서의 동작 주파수에 맞도록 보상하는 방법에 관해 연구. 3) Zero Crossing Detection 회로를 활용하여 BLDC 전동기의 회전자 위치 추정 연구.

• 제어로봇시스템학회논문지
• /
• 제19권6호
• /
• pp.508-512
• /
• 2013

In recent years, sensorless drive schemes have been proposed widely and most of them are based on the ZCP (Zero Crossing Point) detection of the BEMF (Back Electro-Motive Force). These schemes have two main problems. One is that ZCP may not be detected at low speed and thus a forced drive is required. The other problem is that there is $30^{\circ}$ phase difference between ZCP and the motor commutation instant and to ensure proper operation, this gap should be accounted for. To solve these problems a circuit is devised for detecting ZCP of the BEMF difference through the line voltage difference. Experimental results show that the output of this circuit is identical to that of the Hall sensor signal, and velocity control of a BLDC motor is possible without the sensor.

• 대한전기학회논문지
• /
• 제36권5호
• /
• pp.352-359
• /
• 1987

The cycloconverter operating on a circulating current-free mode has many zero crossing points. If an exact zero crossing points are not detected, the three phase-unbalanced currents will flow in a motor. In this paper, the current feedback using a current reference wave is proposed to improve the problems of zero crossing detection, three phase-unbalanced voltages, currents, and torgue ripples. To prevent the saturation of the air gap flux and keep the torque constant, the constant voltage / hertz control with IR compensation is adopted. The PI-controller is designed using the linearized model of the cycloconverterinduction motor system. Alsi, Z-80A single board computer has been used to implement the proposed scheme which results in the performance improvement of cycloconterter-fed induction motor speed control system.