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To realize a soft-switching inverter with small volume and high efficiency, a synchronous auxiliary resonant commutated pole (SARCP) soft-switching inverter with improved load adaptability is proposed, which only contains two auxiliary inductors. In one switching cycle, all commutation processes can be synchronously assisted by an auxiliary inductor. Soft switching is achievable for all switches of the SARCP inverter. Compared with the auxiliary resonant commutated pole (ARCP) inverter, the SARCP inverter has improved load adaptability, especially in the light load current condition, which is beneficial to reduce the total power loss and the dc-link capacitance. The equivalent circuits of the SARCP inverter are given under different operation modes. The operation principle, soft-switching implementation conditions, parameter optimization design methods, and the characteristics of the SARCP inverter are analyzed. Finally, simulation and experimental results verify the effectiveness of the SARCP inverter. [ABSTRACT FROM AUTHOR]

This article proposed a grid-connected photovoltaic (PV) converter based on modular multilevel converter (MMC), which can realize long-distance dc transmission while realizing the local consumption of PV. In addition to the advantage that there is no PV power mismatch between the upper and lower arms, the isolation transformer couples the two submodules of the upper and lower arms on a three-port transformer, and the differential-mode components of the capacitor voltage ripples in the upper and lower arms can be canceled between each other. Besides, through the double fundamental frequency circulating current control, the power exchange among MMC phase units can be realized, thereby eliminating the common-mode component of the capacitor voltage ripple. Through the combination of topology and control strategy, the low-frequency components of the voltage ripple can be completely canceled. Since the decoupling capacitance is reduced dozens of times, the volume and cost of the system are significantly reduced. Therefore, the life and reliability of the system are increased. Simulation and experimental results verify the effectiveness of the proposed topology and its control strategy. [ABSTRACT FROM AUTHOR]

LLC resonant converter can achieve zero voltage switching (ZVS) for primary-side devices and zero current switching (ZCS) for secondary-side rectifiers. However, the reverse recovery and junction capacitance (Cj) of secondary-side diode critically affect the ZVS condition of primary-side switches. The effect of Cj has been discussed in literature, but not the reverse recovery. In this paper, the reverse recovery charge (Qrr) is converted to an equivalent capacitance $(C_{{\rm rr}\_{\rm eq}})$ for the study of primary-side ZVS performance. An accurate model during deadtime is derived and further applied to characterize ZVS performance with different reverse recovery charges in different regions. The concept of establishing parameter Ctotal to consider both Cj and $C_{{\rm rr}\_{\rm eq}}$ is proposed to evaluate the effect of the secondary-side rectifiers. This concept provides the guideline for diode and synchronous rectification mosfet selection to ensure ZVS condition for LLC converters. To verify the concept and the derived model, a 200/400 V 400 W LLC resonant converter prototype operating from 200 to 700 kHz is built and its ZVS performances with different diodes are compared. Two issues caused by Qrr effect, including $V_{\rm ds}$ reverse charging and asymmetrical waveform during deadtime, are explained thoroughly as well. [ABSTRACT FROM AUTHOR]

Lifetime is an important performance factor in the reliable operation of power converters. However, the state-of-the-art LC filter design of a buck dc–dc converter is limited to the specifications of voltage and current ripples and constrains in power density and cost without reliability considerations. This paper proposes a method to optimize the design of the LC filters from a reliability perspective, besides other considerations. An enhanced model is derived to quantify the lifetime of the capacitor in the filter considering the electrothermal stress on it. Furthermore, the influence of different design aspects such as the value of capacitance, the value of inductance, and the type of the capacitor have been discussed, focusing on their impacts on the key design objectives, which are the cutoff frequency, lifetime, and volume. Based on the analysis, an optimized design is proposed among different parameter sets. A 1-kW converter prototype is applied to verify the theoretical analysis and simulation. [ABSTRACT FROM AUTHOR]