The interruption of power supply is one of the major technical issues in rotation angle sensorless controls of PMSMs. This causes failures of inverter operation due to voltage drop in filter capacitor (FC). In order to solve this technical issue, we propose a method to achieve continuous operation of PMSMs with low inertia loads, for example compressors of air conditioners, in case of power supply interruption. In the proposed method, the current reference is determined according to the relationship between the kinetic energy of the motor and the electrical energy of the FC to effectively use the available energy. The proposed method is validated by experimental test of 1-kW class PMSM.

STATCOMs have attracted attention as var compensators on electric power distribution systems. In this study, a star-connected modular multilevel converter (MMC) was applied to STATCOM. The voltage across the strings of the star-connected MMC was 1/√3 times that of a delta-connected MMC. MMCs can be interconnected without a transformer because they have high equivalent carrier frequency through phase-shifted pulse-width modulation. The dc capacitor voltage control of a star-connected MMC is relatively complex compared with delta connected MMCs, which have a circulation current as a control parameter. Relevant literature suggests that conventional dc capacitor voltage controls of MMCs for STATCOMs might be difficult to operate when the output reactive power is zero var. This paper presents a new dc capacitor voltage control method using symmetrical components. The overall control block mainly consists of two parts: average dc and dc capacitor voltage controls. The proposed dc capacitor voltage control and reactive power control were verified through experiments.

Recently, global warming and the problems with incorporating environmental safeguards have promoted the need for a more power-efficient motor. Therefore, as a driving source, permanent magnet synchronous motor (PMSM) is widely used as an important device for a variety of fields. However, a PMSM generates electromagnetic vibration when driven by PWM inverters. This paper describes the frequency of the electromagnetic vibration of a PMSM with a distributed winding. We investigated the electromagnetic force by analyzing a circuit simulator using two-dimensional finite element analysis. It is found that the electromagnetic vibration resulted from electromagnetic force of the zeroth order of space harmonics. In addition, electromagnetic vibration mode of this order is confirmed in experiment.

This paper proposes a new fast-tracking vector control method for permanent-magnet synchronous motors (PMSMs) equipped with a set of three Hall-effect sensor (HES) elements. Vector control for PMSMs requires precise rotor position information, which is acquired from high-resolution position sensors mounted on the rotor such as an encoder and a resolver. However, these sensors have several drawbacks in terms of cost, volume, reliability etc. An HES, which provides very rough position information with a 30-degree error, is a possible candidate to overcome the drawbacks. This paper proposes a new method that can synthesize position information with sufficient precision for vector control from an HES signal. The proposed method, which is established based on the “high-frequency integral-type PLL method”, allows the control system to track a varying command of angular acceleration 500rad/s².

This paper presents a variable magnetic flux PM motor in which space harmonic power is utilized for the magnetic flux weakening, automatically. The stator has a toroidally-concentrated winding structure, and the torque generation surfaces are composed of three air-gaps, which are single radial-gaps and double axial-gaps. The radial-gap rotor is a consist-magnetized PM rotor, and the axial-gap rotor is a self-excited wound-field rotor. These rotors are coaxially fastened with opposite magnetic pole position. The magnetomotive force of axial-gap rotor can automatically retrieve space harmonic power, which is inevitably generated by a concentrated winding structure. A mechanical design of the prototype is revealed, and the operation principle of the automated-magnetic flux weakening is clarified through the mathematical approach. Then, the operation principle of the electrified reversal magnetic pole is experimentally demonstrated, and the effects of the proposed variable magnetic flux technique are verified using the prototype machine in terms of the adjustable speed drive characteristics and the variable magnetic flux range.

This study describes a Variable Leakage Flux type Interior Permanent Magnet synchronous motor (VLF-IPM) for an automobile traction motor. The proposed VLF-IPM can control the leakage flux in the rotor core depending on the armature reaction. As the motor can suppress d-axis current to reduce the back-EMF, the motor improves not only the motor efficiency but also the inverter efficiency in the high speed area. It is experimentally confirmed that the VLF-IPM can achieve the high efficiency driving in the wide speed range.

A novel three-phase sextuple voltage rectifier circuit is presented. The proposed circuit applies the diode charge pump scheme to the three-phase system and the direct output voltage is about 6 times more than the input line-to-line voltage. The validity of the proposed circuit is demonstrated using simulations and experiments.