An induction heating system is proposed as a new circuit topology for induction heating cookers that can be used with all metals. This system has the mechanism to drive an IGBT and a MOSFET in parallel that switch the inverter between full-bridge or modified half-bridge configuration according to the cookware material. When cookware made of a low-resistivity material such as copper or aluminum is heated, the inverter is switched to the half-bridge configuration, which turns off the IGBT leg earlier than the MOSFET leg. When cookware made of a high-resistivity material such as iron or magnetic stainless steel is heated, the inverter is switched to the full-bridge configuration. We confirmed a turn-off timing for the IGBT where the loss of the switching element in the parallel drive was minimized by an experiment. The proposed inverter effectively improved the electricity conversion efficiency for all metals pan heating with the utilized IGBT and MOSFET legs.
A high conversion efficiency is always required for photovoltaic power conditioners to utilize PV-generated DC power with minimal loss. The cooperative control method has been developed as one of the control methods that improves the conversion efficiency, which is applicable to non-isolated power conditioners consisting of a boost converter and an inverter. In the cooperative control method, the boost converter creates part of the AC voltage waveform, and either the boost converter or inverter performs switching only during a required period. Therefore, it has the advantage of reducing switching losses. In this paper, we present a study of a cooperative-control-type power conditioner assuming its use in grid-connected operation and the results of a performance verification of prototype power conditioner. A microcontroller is used for cooperative control. The experimental results show that the prototype power conditioner integrated with SiC MOSFETs and the cooperative control method achieves an efficiency of 97.4% at an output of 5.5kW.
In recent years, various storage battery systems, such as home battery system, V2H/V2G system, and UPS system, have spread rapidly all over the world. We propose a new power conversion system for use in the previously-stated storage battery systems. This paper describes operation analysis of this system for bi-directional power conversion with fundamental grid-interconnection. Good output follow-up controllability characteristics of the proposed system are shown through experimental results.
This paper presents a novel prototype of a single-stage zero voltage soft-switching (ZVS) pulse-width-modulation (PWM) -controlled AC-AC converter with a silicon carbide (SiC)-MOSFET/SiC-SBD power module for high frequency (HF) induction heating (IH) applications. The newly developed AC-AC converter can achieve higher efficiency than a Si-IGBT/Si-PNdiode power module-based prototype thanks to a low ON-resistance of SiC-MOSFET and a low forward voltage of SiC-SBD under the condition of high frequency switching. The performances of the new prototype converter are evaluated by experiment with a single-phase IH utensil of ferromagnetic stainless metal, after which the high-efficiency and low switching noise characteristics due to the all SiC power module are actually demonstrated.
A new inverter technology for packaged air conditioners based on the indirect matrix converter topology was used for practical applications. The selected unidirectional power conversion characteristics of the power circuit were suitable for air conditioning. Furthermore, a new modulation method suitable for microcomputer control was introduced. The evaluations showed that there was an increase in the conversion efficiency and the conformity with the harmonic standard was realized. Product development confirmed the reductions in noise and number of passive components.
Electric energy storage systems are very important as one of the solutions to global warming. Step-up/step-down characteristics are required for electric energy storage systems. In addition, such systems must have high efficiency, low cost, and small scale. Therefore, the authors proposed a single-phase step-up/step-down bidirectional converter with voltage-fed and current-fed hybrid-type operation. The proposed converter consists of a two-quadrant dc-dc converter and a single-phase voltage-fed converter. The circuit has several advantages such as low switching loss, use of very small capacitance, and so on. In this paper, the authors compare a comparison of the switching losses with a simple analysis.
Recently, wireless charging via magnetic resonance coupling has gained attention because it has the potential of efficient midrange wireless charging. Here, functions such as sensing at the transmitter and wireless communication from the target are the essential elements to realize a standard wireless charging system. Currently, the sensing and communication protocol of the hardware (i.e., the high-frequency power source and antenna configuration) compatible with wireless charging is gaining attention in terms of its cost and space reduction due to the use of common components for multiple functions. However, this protocol has the problem of narrow effective areas due to the fact that the sensing range depends on the fixed Q factor of the antenna. To overcome this problem, the concept of wide-area sensing based on a Q controllable antenna is proposed, and the effectiveness is verified through a theoretical analysis and an experiment. As a result, it is clarified that the effective area can be expanded up to a ratio of the distance g between the transmitting and receiving antennas to the inner diameter d of the antenna g/d =5.0.
In this paper, to provide a reduction in the size and weight of a motor, improvements in the torque density by the use of a three-dimensional bent core were examined. A motor using a three-dimensional bent core can collect flux leakage. The torque density could be improved by 10% by effectively using the magnetic flux. As a result, reductions in the size and weight of the motor are possible, and an increase in the performance of an automobile or a robot can be expected.
This paper describes a 750-Vdc, 100-kW, 20-kHz bidirectional isolated dual-active-bridge (DAB) dc-dc converter using SiC-MOSFET modules without free-wheeling diodes, focusing on the output voltage ripple and power conversion efficiency. Intermittent operation brings higher conversion efficiencies in a low-power range to the dc-dc converter than does continuous operation because it makes a significant contribution to reducing switching (snubber) and iron losses. Experimental results reveal that the efficiency at 10kW (10% of the rated power) is 95.1% in continuous operation, whereas it is improved to 98.2% in intermittent operation. The combination of intermittent operation with continuous operation makes the efficiencies in a power range from 3 to 100kW higher than 98%, excluding power losses produced by the control and gate-drive circuits. However, the intermittent operation may bring additional voltage ripples to the dc output terminals. Theoretical analysis confirms that the voltage ripples in a power range from 1 to 18kW are lower than 7V in peak-to-peak, which is only 0.9% of 750Vdc. Theoretical results are confirmed by comparison to simulated and experimental ones.
This letter describes a current sensor embedded in a laminated bus bar. The proposed sensor is based on the Rogowski coil principle, and it can detect the magnetic flux that corresponds to a derivative waveform of the current inside the bus bar. The current sensor for the laminated bus bar has been used in a buck converter circuit. The experimental results confirmed that the proposed current sensor can measure switching waveforms without any propagation delay.