Hag-Wone Kim

Design and Analysis of Position Tracking Observer Based on Instantaneous Power for Sensorless Drive of Permanent Magnet Synchronous Motor

This paper proposes a simple position observer based on the instantaneous power and a tuning procedure for the proposed observer in driving the surface-mounted permanent magnet synchronous motor. In the instantaneous power of a three-phase system, the imaginary and real powers have the information related to the position and velocity. Using the instantaneous power, the difference between real rotor position and estimated rotor position is calculated. For easy design, gain parameters are described as a bandwidth of position observer. The proper bandwidth is expressed in terms of the desired load transient response, system inertia, and permitted acceleration range. Also, the sensitivity of phase resistance and inductance is analyzed. The described mathematical results show the necessity of accurate parameter information. Simulation and experimental results show the validity of the proposed design method and analysis.

Simple switch open fault detection method of voltage source inverter

Recently, permanent magnet synchronous motors are applied to various applications such as electric vehicle, aerospace, medical service, and military applications due to several outstanding characteristics. Because of the importance of high reliable operation in these areas, many researches which are related to the fault detection and diagnosis of inverter systems are conducted. In this paper, a new simple fault detection method of voltage source inverter for permanent magnet synchronous motor is proposed. The feasibility of the proposed method is proved by simulation and experiment. By the simulation and experiments, rapid detection characteristic of the proposed method has been proved without any additional voltage sensor.

Analysis of LLC Resonant Converter with Current- Doubler Rectification Circuit

In this paper, LLC series resonant converter with current-doubler as a rectification circuit for secondary side is proposed. The current-doubler circuit is generally used for the high voltage input and low voltage output application to get high efficiency characteristics with reduced transformer turn ratio. However, an inductive circuit is not used in a secondary side for the LLC series resonant converter generally. When there is inductive circuit like current-double on the secondary side, the resonant characteristics are changed. In this paper, LLC converter with the current-doubler using coupled inductor is proposed. We verify that the secondary side current-doubler using coupled inductor is not affect to the resonant characteristic of primary LLC by the mathematical analysis. Finally, the analysis results are proved by the simulation and experiments.

A common-mode voltage reduction PWM method for three-phase unidirectional rectifier

In the present paper, a pulse width modulation (PWM) method that enables common-mode noise reduction in three-phase, three-level Vienna rectifiers is presented, and the losses in this system are compared and analyzed in relation to those of existing PWM methods. The proposed common-mode voltage reduction PWM method increases the number of times of switching compared to existing space vector modulation methods. The PWM method enables common-mode voltage reduction, and it is introduced through simulations; the losses are compared with other approaches to demonstrate the usefulness of the proposed PWM method.

Dead time compensation using MRAS observer for a permanent magnet synchronous motor

A dead time of the PWM inverter for variable speed motor drives generates the distortion in the phase currents. The current distortion is one of the sources of torque ripples in a PM synchronous motor. In this paper, the effect of the dead time to the torque ripple of a PM synchronous motor is investigated. To reduce the current distortion caused by the dead time, the dead time compensation by the estimated output voltage distortion using the MRAS observer is investigated. Also, the effectiveness of the dead time compensation methods by abc reference frame and dq reference frame are compared.

Design and analysis of position estimator based on instantaneous power for sensorless drive of permanent magnet synchronous motor

This paper proposes a simple position estimator based on instantaneous power and a tuning procedure for the proposed estimator in driving surface mounted permanent magnet synchronous motor. In the instantaneous power of three phase system, the imaginary and real power has the information related to the position and velocity. Using the instantaneous power, the difference between real rotor position and estimated rotor position is calculated. For easy design, gain parameters are described as bandwidth of position estimator. And, the proper bandwidth is expressed as the desired load transient response, system inertia and permitted acceleration range. Also, the sensitivity of phase resistance and inductance is analyzed. The described mathematical results show the necessity of accurate parameter information. Simulation and experimental results show the validity of the proposed design method and analysis.

Current control of PMSM in overmodulation region

This paper presents a study on a current control of a PM synchronous motor which is fed by two-level voltage source inverter in the large modulation index area. In order to increase dynamic response and extend speed limit caused by voltage limit, overmodulation method is generally used. But, the voltage ripple generate current ripple in overmodulation region. This current ripple reduce current controller bandwidth. In this paper, an improved current controller has been proposed for overmodulation region. The methods are described and analyzed and the experimental results are presented.

DC/DC converter circuit to solve unbalanced power by multiple input transformers

Large-capacity DC/DC converter with high-input voltage and low-output voltage generally has a serial-input parallel-output structure with several stages for efficiency and miniaturization. However, error values in active and passive elements in the power supply unit of a multi-stage DC/DC converter causes a power imbalance in each terminal. This degrades the reliability of the DC/DC converter because of both the increase in stress on elements and excessive heat. Therefore, this study proposes a method to solve this problem by using multiple input transformers that share magnetic coupling to improve the power imbalance of a DC/DC convert at each level.

Sensorless control of a PM synchronous motor in over modulation regions for high speed operation

For the sensorless control of a PM synchronous motor without using rotor position sensors, the information on the actual voltages and actual currents of the motor are required. In the model based rotor position estimator of a PM synchronous motor, the reference voltages, which are the output of the current controller, are commonly used. The reference voltages in over modulation regions for high speed operation are different from the actual voltages applied to the motor so that the estimated rotor position and rotor speed may fail to track the real rotor position and real rotor speed. In this paper, the sensorless control for a PM synchronous motor in over modulation regions for high speed operation is proposed. Three phase voltages applied to the motor are measured by using additional voltage detection circuits, and the rotor position estimator based on the measured three phase voltages is validated through experiment.

Post-fault operation of open-circuit fault in three-phase PWM converter

In this paper, a simple and low-cost post-fault operation of open-circuit fault for three-phase pulse-width modulated (PWM) converter is proposed. An open-circuit fault causes the current difference in the switches and increases the harmonics and output voltage ripples, which significantly degrades the system performances. It is because of a zero-vector affected by the open-circuit fault. Therefore, the proposed postfault operation method is based on changing the original PWM switching patterns into modified PWM switching patterns which is totally substituting faulted zero-vector to healthy zero-vector. With the proposed method, the current difference in the switches can be significantly reduced and the output voltage ripples can also be minimized. The simulation and experiment are conducted to show the usefulness of the proposed method for the three-phase PWM converter.