Yo-Chan Son

A new active common-mode EMI filter for PWM inverter

This paper presents a new active common-mode electromagnetic interference (EMI) filter for the pulse-width modulation (PWM) inverter application. The proposed filter is based on the current sensing and compensation circuit and it utilizes a fast transistor amplifier for the current compensation. The amplifier utilizes an isolated low-voltage DC power supply for its biasing and it is possible to construct the active filter independent of the source voltage of the equipment. Thus the proposed active filter can be used in any application regardless of its working voltage. The effectiveness of the proposed circuit has been verified by experimental results.

Generalization of active filters for EMI reduction and harmonics compensation

This paper analyses general active filters that can be applicable to EMI filter, active power filter, etc. It gives generalized equations presenting insertion losses and input impedances of various kinds of active filters, from which the requirements and limitations of active filters can be identified. Based on this analysis, the effectiveness of the active filters presented in several literatures is investigated. With the results of this study, an appropriate topology of an active filter for a specific application can be selected with a good rationale.

Current measurement issues in sensorless control algorithm using high frequency signal injection method

This paper presents the current measurement issues in sensorless control of a permanent magnet (PM) machine based on the fluctuating high frequency voltage signal injection (HFI) method. In such a sensorless control of the PM machine, the accuracy of the rotor position estimation mainly depends on the accuracy of the current measurement of the drive system. The accuracy of current measurement mainly depends on the current scaling errors, offset currents, and the quantization errors of the analog-to-digital (A/D) converter. In this paper, the effects of the current measurement errors on the accuracy of the rotor position estimation in sensorless control of the PM machine based on the HFI method is analyzed using an example of current measurement system and sensorless control scheme. The simulation and experimental results are shown in order to verify the validity of the analysis results.

Conducted EMI in PWM inverter for household electric appliance

This paper presents the characteristics of the conducted EMI in the PWM inverter for household electric appliances and proposes a new active common-mode EMI filter. The conducted EMI spectrums are measured with changing the active/passive filter stages and the common-mode EMI is extracted from the total conducted EMI spectrums in order to identify the dominant source of the conducted EMI. For better understanding of the conducted EMI, the noise sources are identified and the characteristics of the noise source and its propagation paths are investigated from the conducted EMI spectrums measured. Based on the measurement and analysis of the conducted EMI in the PWM inverter, the effective method and procedure of designing filter stages are developed in order to attenuate the conducted EMI effectively.

Sensorless operation of permanent magnet motor using direct voltage sensing circuit

In this paper, position-sensorless operation of the permanent magnet motor is introduced. To estimate the rotor position and speed, a new closed-loop flux observer is proposed for wide speed operation. To extend the operation range of the proposed algorithm, a direct voltage sensing circuit is proposed that enables correct disturbance voltage rejection and stable operation of the proposed flux observer at extremely low speed. Experimental results of position-sensorless torque control are shown in order to verify the feasibility of the new algorithm using the proposed voltage sensing circuit.

A novel active common-mode EMI filter for PWM inverter

This paper presents a novel active common-mode EMI filter for the PWM inverter application. The proposed filter is based on the current sensing and compensation circuit and it utilizes a fast transistor amplifier for the current compensation. The amplifier utilizes an isolated low-voltage DC power supply for its biasing and it is possible to construct the active filter independent of the source voltage of the equipment. Thus the proposed active filter can be used in any application regardless of its working voltage. The effectiveness of the proposed circuit is verified by experimental results.

A new space vector pulsewidth modulation strategy for reducing ground to stator-neutral voltage in inverter-fed AC motor drives

This paper proposes a new two-phase PWM scheme that can reduce the ground to stator neutral voltage in three-phase diode rectifier/inverter system with corner grounded delta-connected input source. According to the sign of voltage difference between ground and DC-bus midpoint voltage, the proposed PWM use only one zero space vector in one control period. Thus, the peak-to-peak value of ground to stator neutral voltage can be reduced to 2/3 compared with conventional three-phase SVPWM. Without any degradation of control performance of inverter, the proposed PWM scheme can be easily implemented in software and requires no extra hardware except a simple neutral voltage measurement circuit.

Analysis and compensation of current sampling error in AC drive with discontinuous PWM

This paper addresses the issue of current sampling in high performance AC motor drive systems fed by a discontinuous PWM inverter. The effect of the sampling error due to the measurement delay produced by the low pass filter and A/D converter is described in case of discontinuous PWM. To compensate the error, a method to estimate the delay time of the whole measurement system based on the measured current is proposed and its effectiveness is verified by experimental results. The proposed algorithm can automatically estimate the system delay introduced by low pass filter and A/D converter at the commissioning stage. Through delaying the current sampling by the estimated value, experimental results reveal more than 50% reduction of current ripples.

Integrated MOSFET inverter module for low-power drive system

This paper introduces a new MOSFET inverter module for driving small brushless dc motors used in fans and water-pump applications. The proposed power module integrates six MOSFETs and three dedicated gate-driving high-voltage integrated circuits (HVICs) in a transfer-molded full-pack package. It provides optimized loss and epoxy molding compound characteristics by using particularly designed MOSFET and dedicated HVIC. This paper describes the package design, the MOSFET, and the HVIC of the proposed module used in motor-drive applications, where power dissipation, electromagnetic interference, and noise immunity are primary concerns.