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This study provides a survey overview of the literatures with the goal of maximizing the efficiency of DC‐AC power conversion from an engineering science perspective. With the advent of wide band gap power semiconductors, the published literature on realizing high efficiency DC‐AC converters has increased. Therefore, a literature survey of high‐efficiency DC‐AC inverters was first conducted. We demonstrated the importance of the measurement accuracy in measuring high efficiency losses, and then presented the literature on new measurement methods, as well as examples of analysis of the breakdown of these losses. Furthermore, we reviewed the literature on high‐efficiency inverters. We presented measurement data (99.83%) on an inverter with a high efficiency energy conversion system circuit topology using Silicon Carbide (SiC) and Gallium Nitride (GaN) devices to demonstrate how the procedure was used to achieve loss minimization. We summarized the challenges hindering high efficiency. © 2022 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC. [ABSTRACT FROM AUTHOR]

This article proposes a new optimization method and its platform for automatically adjusting the control parameters of a digital active gate driver while operating a pulse-width modulation (PWM) inverter. The proposed optimization method applies the searching parameters for some sectors in an ac current cycle and fixed parameters for the other sectors. This enables us to find the optimal operating points of power devices so as to reduce the surge voltage and switching loss with the consideration of their dependency on the load current. Additionally, the proposed optimization method also can find the operating points while the inverter performs a continuous switching operation. For this reason, the proposed optimization method can be applied to a continuous running test of PWM inverters, for example, in a manufacturing process. The validity of the proposed method and platform was evaluated by using a 10-kW three-phase PWM inverter with digital gate drives. The experimental results confirmed that the proposed optimization method makes it possible to find the optimal operating points for reducing the surge voltage and/or the power loss. [ABSTRACT FROM AUTHOR]

This article presents a flying-capacitor linear amplifier (FCLA) that achieves high efficiency, low harmonic distortion, and low electromagnetic interference (EMI). A conventional class-B linear amplifier cannot be used in power conversion applications, because the power loss generated in active-state MOSFETs is high compared with the loss generated in switching operations. In the proposed FCLA, multiple series-connected MOSFETs are used, and only one MOSFET operates in the active state at a time. Thus, the power loss generated in the MOSFETs can be reduced, and the FCLA can achieve high efficiency without performing the switching operation. In this study, the features of the FCLA and conventional linear amplifiers are theoretically compared and evaluated. Moreover, a voltage balancing control for flying capacitors is proposed and verified through simulations and experiments. It is demonstrated that the prototype 12-series FCLA achieves over 89% efficiency and generates low harmonics and low EMI. The proposed configuration is useful for increasing the number of series MOSFETs, and it contributes to realizing a power converter with advantages such as low harmonic distortion, low EMI, and high efficiency. [ABSTRACT FROM AUTHOR]

DC microgrids have been emerging as next-generation small-scale electric power networks, where the line impedance is very low. This phenomenon causes large currents in the microgrids, even for a slight change in voltage; therefore, it is critical for a power flow controller to have faster transient response and precise power flow control. In this study, multi-level converters are applied as the power flow controllers to realize high-speed and high-precision power flow control in a dc microgrid. The output filter can be small, as a multi-level converter is used. This paper also presents the design of the output LC filter of a multi-level converter to satisfy a requirement of current ripple. We experimentally verified that a multi-level converter with a smaller filter can realize high-speed and high-precision power flow control for low line impedance conditions compared with the conventional two-level converters. [ABSTRACT FROM AUTHOR]

The requirements for peripheral circuits of power converters are becoming more restrictive due to the enhancement of Si-based power devices and due to practical use of SiC device. In the design of modern high-speed switching converters, the stray inductances and capacitances both in the device package and in the gate drive circuit in addition to those in the main circuit of the power converter must be considered. In these situations, the gate driving technique represents the key technology for enhancement of high-speed switching ability of power devices, as there are design limitations to reduce the stray inductances and capacitances. So far, several active gate control methods have been proposed. Most conventional active gate drivers are configured using analog circuits such as transistors and diodes. Thus, it is difficult to reconfigure their control parameters to fit the stray inductances and capacitances after the implementation of power converter and gate circuits. As a solution to these problems, the authors have proposed a programmable gate driver IC, which is a digitally controlled circuit. This gate driver IC can control the gate current at 63 separate levels, operated by programmable fully digital 12-bit and clock signals. In this paper, an active gate current control based on the load current in a half-bridge inverter with two programmable gate driver ICs is demonstrated. This developed gate control is different to the general current feedback control followed the reference value. It is verified that the proposed active gate control can effectively improve the tradeoff relationship between the surge voltage and switching loss of the pulsewidth modulation half-bridge inverter circuit. [ABSTRACT FROM AUTHOR]

Multilevel inverters have very attractive features, such as lower harmonics in the output, lower EMI, and reduction of the required voltage rating of power semiconductor devices. Among them, lower harmonics in the output can reduce the volume of the output harmonic filter and additional losses caused by the harmonics. Therefore, multilevel inverters are expected to realize higher power density and higher efficiency. In this paper, as a basis of the quantitative investigation of these features, the harmonics in the PWM output voltage of multilevel inverters are analyzed theoretically. As an application of the theoretical results, the usefulness of the theoretical results is verified by the prediction of the harmonic contents of the load current. [ABSTRACT FROM AUTHOR]

SUMMARY Multilevel converters can essentially reduce harmonics even when their switching frequency is low. Among the various topologies of the multilevel converters, flying capacitor converters are considered to be promising converters for realizing high power density. However, the main circuit of the flying capacitor converters has many capacitors. Therefore, in this study, the volume of the capacitors in the flying capacitor converters is determined by taking into consideration the allowable ripple voltage and temperature rise in the capacitor. © 2013 Wiley Periodicals, Inc. Electr Eng Jpn, 186(4): 81-91, 2014; Published online in Wiley Online Library (wileyonlinelibrary.com). DOI 10.1002/eej.22361 [ABSTRACT FROM AUTHOR]