Katsuji Shinohara

New current-controlled PWM rectifier-voltage source inverter without DC link components

The voltage-source inverters are normally equipped with an electrolytic capacitor in their DC link, the electrolytic capacitor has several disadvantages such as increasing size, limiting converter life and reliability. Therefore several approaches for removing the DC link capacitor have been studied. This paper proposes a new voltage source inverter without DC link components, whose rectifiers are controlled by suitable current feedback to adjust near-sinusoidal AC source current waveforms at unity power factor. The calculated characteristics are described for a 0.75 kW induction motor driven by this inverter.

Four-step commutation strategy of PWM rectifier of converter without DC link components for induction motor drive

In this paper, we describe a method of generating gate signals of the PWM rectifier section of the converter without DC link components, which is able to remove snubber circuits. In the snubber circuits, losses have been dissipated every time the switches of the rectifier section are turned on and off. The commutation strategy of the proposed method consists of four steps during the switching process. The proposed method is verified by experimental tests on an induction motor drive. It is concluded that it decreases losses in the rectifier section.

Characteristics of permanent-magnet synchronous motor driven by PWM inverter with voltage booster

The steady-state characteristics of an interior permanent-magnet (IPM) motor driven by a pulse-width-modulation (PWM) inverter with voltage booster are analyzed and the transient behavior is investigated. The PWM inverter with voltage booster consists of a conventional PWM inverter and a voltage booster to control the DC-link voltage. The current trajectory on the i/sub d/-i/sub q/ plane is illustrated and the torque, voltage, and current versus speed characteristics are represented. Furthermore, the analytical and simulated results are compared to the experimental results for a 1.5 kW IPM motor and the validity of the analysis and simulation is confirmed by their agreement.

Small-signal stability analysis of vector control system of induction motor without speed sensor using synchronous current regulator

This paper presents a stability analysis of a speed sensorless vector control (SSVC) system of an induction motor. The stability analysis takes into account the effects of three current control loops. The poles and zeros of the transfer functions for the rotor speed are calculated to investigate the influences of controller parameters and motor parameters. The theoretically derived step responses are compared with the experimental results. Also, the Bode diagrams of the transfer functions for the torque producing current are calculated. The settling time of the step responses of the rotor speed for the various designs of the current regulator (CR) is studied. This paper discusses the suitability of different CR methods for the SSVC system of an induction motor.

A study of dead-time of PWM rectifier of voltage- source inverter without DC link components and its operating characteristics of induction motor

A voltage-source inverter without dc-link components is an ac-to-ac converter having dual bridges of a pulsewidth-modulated (PWM) rectifier and a PWM inverter that can be controlled independently. While conventional matrix converters have disadvantages, such as a complicated commutation scheme and necessity of a large-sized clamp circuit, commutation, and protection of our inverter can be implemented easily. In order to control the PWM rectifier and the PWM inverter independently, snubber circuits for the PWM rectifier are required to assure the path of load current during dead time. In this paper, analytical method of a snubber circuit and operating characteristics of a snubber circuit are described when a 0.75-kW induction motor is driven by our inverter.

Characteristics of permanent magnet synchronous motor driven by PWM inverter with voltage booster

The steady state characteristics of the interior permanent magnet (IPM) motor driven by the PWM inverter with voltage booster are analyzed and the transient behavior is investigated. The PWM inverter with voltage booster consists of a conventional PWM inverter and a voltage booster to control the DC link voltage. The current trajectory on the i/sub d/-i/sub q/ plane is illustrated and the torque, voltage and current versus speed characteristics are represented. Furthermore, the analytical and simulated results are compared to the experimental results for 1.5 kW IPM motor and the validity or the analysis and simulation is confirmed by their agreement.

Comparison between flux weakening and PWM inverter with voltage booster for permanent magnet synchronous motor drive

The operation by the PWM inverter with voltage booster is compared with the flux weakening operation for 1.5 kW interior permanent magnet synchronous motor drives. Equations are derived and performances are analyzed for both operations. Current trajectories in the i/sub d/-i/sub q/ plane are shown. In addition, torque, voltage, current and efficiency versus speed characteristics, which are obtained from analysis for both operations, are compared. The results show some advantages of the operation by the PWM inverter with voltage booster.

Zero-switching-loss PWM rectifier of converter without DC link components for induction motor drive

A new commutation strategy for the PWM rectifier section of the converter without DC link components is described. The advantages of the system are the zero-switching-loss and the snubberless circuit of the PWM rectifier section. During the zero voltage vector period of the inverter section, the load current does not flow in the PWM rectifier section. So, if each switching operation of the PWM rectifier section are done in the zero voltage vector period, zero current commutation can be possible. The proposed strategy is verified by computer simulation and experimental test on an induction motor drive.

Stability improvement of vector control system of induction motor without speed sensor using synchronous current regulator

This paper presents a stability analysis of a speed sensorless vector control (SSVC) system of an induction motor. The stability analysis takes into account the effects of three current control loops. The poles and zeros of the transfer functions for the rotor speed are calculated to investigate the influences of controller parameters and motor parameters. The theoretically derived step responses are compared with the experimental results. Also, the Bode diagrams of the transfer functions for the torque producing current are calculated. This paper discusses the suitability of different current regulator (CR) methods for the SSVC system of an induction motor.

Magnet configurations and current control for high torque to current ratio in interim permanent magnet synchronous motors

Usually, Permanent Magnet Synchronous Motors (PMSM) are designed so that they may induce the sinusoidal electromotive force (EMF), at least for the line-to-line voltage, because of necessity to suppress the torque ripples when they am driven by sinusoidal current. Thus, the size for using the magnets is restricted. In this paper an extended magnet type (thickness of magnet is not changed) interior PMSM (EPMSM) Inducing the non sinusoidal EMF is proposed. Two suitable current waveforms will be calculated that maximizing of torque, minimizing of copper losses and torque ripple less have been taken Into the consideration. The calculated performance of this type EPMSM model Is compared with that of conventional sinusoidal EMF type IPMSM model driven by sinusoidal current. We found that the torque increased about 15% while the width of magnet had been increased about 20%, and we could confirm that the ripple less output torque was given when the motor was driven by the non sinusoidal current.