The position sensorless control using electromotive force with 120-degree conduction drive is proposed to satisfy the cost, size and weight requirements of PMSM drive systems for home appliances driven by batteries. This method cannot detect the rotor position at low-speed. Therefore, a method is used to accelerate the motor by forcibly switching the conductive pattern. However, this method has problems such as switching to a position sensorless drive and deteriorating efficiency under load condition. In this study, we propose various methods to improve the performance of the position sensorless drive of small IPMSMs with 120-degree conduction drive. In addition, the effectiveness of the proposed method is shown by experimental results.

High step-up boost converters with large input current capacity are necessary for low-voltage renewable energy sources, such as photovoltaic panels and fuel cells. Interleaved converters are a suitable topology for low-voltage, large input current applications. Conventional interleaved converters, however, face a variety of challenges, such as the necessity of additional current control loops for active current balancing, increased voltage stress of semiconductors, and poor extendibility. In this paper, highly extendable interleaved high step-up boost converters with a passive current balancing and reduced semiconductor voltage stresses are proposed. Current capacities and step-up conversion ratios of the proposed converters can be arbitrarily enhanced by extending the number of phases and voltage multiplier (VM) stages, respectively. The experimental results of 500-W prototypes demonstrated passive current balancing, reduced semiconductor voltage stresses, and enhanced step-up conversion ratios.

This study reports experimental results of a wound-field synchronous motor that non-contactly feeds field current via a three-phase air-core rotary transformer. As a feature, the rotary-transformer is configured as a Bandpass Filter (BPF) whose resonance frequency is twice the carrier harmonics generated in motor control. The field magnetomotive force can be passively supplied without interfering with the fundamental current vector control system. First, the operational principle of the proposed system and new rotary transformer will be described. Subsequently, the prototype and the experimental setup will be introduced. Finally, the experimental results of the proposed principle is reported.

Grid-forming inverter control plays an important role in ensuring frequency and voltage stability in a microgrid (MG). This paper proposes a novel power and voltage control in the αβ domain. The proposed method includes two control loops; an outer loop for power droop control and an inner loop for output voltage control. With the proposed controller, active and reactive powers can be controlled according to simple complex power control principles described only in the αβ-domain. Controller gain tuning for both the outer droop and the inner voltage regulator is also proposed; the droop control gains are tuned based on transfer functions around an operating point and the voltage regulator is tuned by a linear quadratic regulator (LQR). The proposed control method is investigated and validated by simulations with a C control program and by experiments with a DSP-based digital control system.

This paper proposes the concept of using a universal smart power module (USPM) for the modularization of power converters. The USPM realizes the main circuit, filter, and controller as one. The power conversion system is composed of a combination of multiple USPMs. This paper proposes a control method for a master controller and a USPM controller for single-phase MMC. The proposed control method is a power cooperative control method for the coordinated operation of each USPM. Furthermore, this paper proposes a method for generating a correction value to suppress the deviation of the load voltage caused by cooperative control. The validity and effectiveness of the proposed control method were clarified by experiments using a prototype. It was confirmed that the output voltage was suppressed to a deviation of 2% by the compensation values from the master controller.

In this paper, a direct matrix converter combined with pulse density modulation control is used as a high-frequency single-phase to low-frequency single-phase power converter connected between the power receiving side of wireless power transmission and commercial grid. Accordingly, a power decoupling circuit is applied to the direct matrix converter to reduce the power pulsation in the proposed system.