Hyung-Min Ryu

Analysis of multiphase space vector pulse-width modulation based on multiple d-q spaces concept

Multiphase motors are usually designed to have the concentrated winding and nonsinusoidal air gap flux density distribution in order to maximize the torque per ampere. This means that the phase voltage of a multiphase motor has the nonsinusoidal waveform. Accordingly, the conventional analysis on a multiphase space vector pulse width modulation (SVPWM), which is confined to a sinusoidal phase voltage, should be extended to a nonsinusoidal phase voltage. In this paper, based on a multiple d-q spaces concept a novel analysis on a multiphase SVPWM to synthesize an arbitrary nonsinusoidal phase voltage is proposed. Through out this paper, a five-phase inverter is used as a practical example. The basic concepts can be easily extended to an n-phase inverter.

Synchronous frame current control of multi-phase synchronous motor - part II asymmetric fault condition due to open phases

In this paper, the synchronous frame current controller of a multi-phase synchronous motor with open phases is proposed. The proposed method can not only possess the superiority of a linear controller over the conventional hysteresis-type current controller but it also enables the current to be regulated without a steady state error. The key idea is that all the harmonics of the current and voltage, which can still contribute to the torque positively, can be equivalently represented as dc components even under asymmetric fault conditions. Through out this paper, a five-phase synchronous motor with one open phase is used as a practical example and the basic concepts can be easily extended into an n-phase ac motor with multiple open phases, which has the arbitrary number or configuration of the remaining healthy phases. Experimental results prove the validity of the proposed modeling and control algorithm.In this paper, a synchronous-frame current controller of a multiphase synchronous motor with open phases is proposed. The proposed method cannot only possess the superiority of a linear controller over the conventional hysteresis-type current controller but it also enables the current to be regulated without a steady-state error. The key idea is that all the harmonics of the current and voltage, which can still contribute to the torque positively, can be equivalently represented as dc components even under asymmetric fault conditions. Throughout this paper, a five-phase synchronous motor with one open phase is used as a practical example, and the basic concepts can be easily extended into an n-phase ac motor with multiple open phases, which has the arbitrary number or configuration of the remaining healthy phases. Experimental results prove the validity of the proposed modeling and control algorithm

Drive systems for high-speed gearless elevators

The authors present a new standardized type of gearless traction machine drive system with a PM motor for high-speed elevators. Some control functions which are indispensable for improving the performance of elevator systems have been addressed. Stringent evaluation, environment and life tests ensure that the presented system is not only high-performance but long-lasting and more reliable.

A new sensorless thrust control of linear induction motor

This paper presents the field-oriented thrust control of a linear induction motor without flux or speed sensor. The induction motor is structurally symmetrical but it has the difference of the reluctances between the flux axis and the quadrature axis due to the main flux saturation. This electrical saliency can be utilized to estimate an instantaneous flux angle by high frequency signal injection. In the case of a rotary induction motor, it has been verified that this high frequency signal injection method gives reasonable torque controllability at zero or low stator frequency even under a heavily loaded condition. In this paper, it is shown that the electrical saliency also exists in the linear induction motor and the comparison with the rotary induction motor is described. From this result, the sensorless field-oriented thrust control of a linear induction motor in low operating frequency region is presented and the sensorless control in the overall frequency range is implemented by the combination with an adaptive observer.

Dynamic load simulator for high-speed elevator system

This paper describes the load simulator for a high-speed elevator, which can emulate a 3-mass system as well as the equivalent 1-mass system. In order to implement the equivalent inertia of the entire elevator system, the conventional simulators have generally utilized mechanical inertia (flywheel) with large radius, which makes the entire system large and heavy. In addition, the mechanical inertia should be replaced each time in order to test another elevator system. In this paper, the dynamic load simulation methods using electrical inertia are presented so that the volume and weight of the simulator system are greatly reduced and the adjustment of inertia value can be achieved easily by software. Experimental results show the feasibility of this simulator system.

Position control for direct landing of elevator using time-based position pattern generation

In this paper, the position control system for direct landing of an elevator is addressed. Conventional systems have employed independent microprocessors for speed, car, and group control respectively and the car controller usually generates a velocity command by combining the time-based and distance-based velocity pattern. In the scheme, it is inevitable that an elevator creeps or stops abruptly in the vicinity of target position. The proposed position control system uses only one high-performance microprocessor, which can execute the car and group control algorithm as well as the speed control algorithm. It simply generates the desired position trajectory (s-curve) based on time and corrects on-line a velocity pattern to make the position error zero. Experimental results show the feasibility of the proposed control scheme.