This paper proposes an improved analytical stray capacitance model for inductors. It considers the capacitances between the winding and the central limb, side limb, and yoke of the core. The latter two account for a significant proportion of the total capacitance with the increase of the core window utilization factor. The potential of the floating core/shield is derived analytically, which enables the model to apply not only for the grounded core/shield, but also for the floating core/shield cases. Based on the improved model, an analytical optimization method for the stray capacitance in inductors is proposed. Moreover, a global Pareto optimization is carried out to identify the trade-offs between the stray capacitance and ac resistance in the winding design. Finally, the analysis and design are verified by finite element method (FEM) simulations and experimental results on a 100 kHz dual active bridge (DAB) converter.

The photovoltaic (PV) output voltage varies over a wide range depending on operating conditions. Thus, the PV-connected converters should be capable of handling a wide input voltage range while maintaining high efficiencies. This paper proposes a new series resonant dc-dc converter for PV microinverter applications. Compared with the conventional series resonant converter (SRC), a dual-mode rectifier (DMR) is configured on the secondary side, which enables a twofold voltage gain range for the proposed converter with a fixed-frequency phase-shift modulation scheme. The zero-voltage switching (ZVS) turn-on and zero-current switching (ZCS) turn-off can be achieved for active switches and diodes, thereby minimizing the switching losses. Moreover, a variable dc-link voltage control scheme is introduced to the proposed converter, leading to a further efficiency improvement and input-voltage-range extension. The operation principle and essential characteristics (e.g., voltage gain, soft-switching, and root-mean-square current) of the proposed converter are detailed in this paper, and the power loss modeling and design optimization of components are also presented. A 1-MHz 250-W converter prototype with an input voltage range of 17 V - 43 V is built and tested to verify the feasibility of the proposed converter.

In dual active bridge (DAB) converters, there can be transformer current ringing, especially when the transformer turns ratio is high. It is induced by high dv/dt generated by fast switching as well as the low impedance of the magnetic tank at the high-frequency range. To quantify the influence of the magnetic tank, its impedance model is thoroughly modeled by considering all the parasitic components. It is found that the parasitic capacitors of the magnetics do not equally affect the current ringing, and thereby the critical one is addressed. On top of that, the design guide of the inductor is provided for the mitigation of the current ringing. Additionally, the impact of dv/dt is also studied. The models and analyses are verified on a 2.5-kW DAB prototype.

Due to the parasitic capacitances of the transformer and inductor in Dual Active Bridge (DAB) converters, resonance happens in the transformer currents. This high frequency resonant current flowing into the full bridges will worsen their soft-switching performance and thereby reduce its efficiency. In order to study the generation mechanism of this current resonance, the impedance of the transformer and inductor with parasitic components is modelled in this digest. Then, based on the impedance model, an approach is proposed to mitigate the current resonance. Finally, both the impedance model and the current resonance mitigation approach are verified by simulated results.

The insulation coordination design against electric-originated complex operation conditions is one of the critical challenges for high-power, high-voltage, high-frequency transformers (H ³ Ts) in solid-state transformers. The connection between the insulation performance and the operational parameters of H ³ T is tightly coupled, but their interaction has been ignored till now. In this letter, an active control method is proposed by adjusting the voltage amplitude, frequency, and temperature to decrease partial discharge (PD) to improve the high reliability of H ³ T. At first, PD versus voltage level, frequency, and temperature in existing typical insulation are identified. Then, the PD rules of different parameters are utilized to provide feedback information and guideline for the control of H ³ T. This letter aims to improve the reliability of H ³ T through active control of PD activities.

The analytical modeling of parasitic capacitances in inductors is commonly based on the energy-conservation law. Yet, in order to calculate the equivalent capacitances of inductors, the floating voltage potential of magnetic core is required to be preknown in all previous modeling methods. This letter proposes an analytical method for calculating the parasitic capacitances of the inductors with low-resistivity cores, which does not require any prior knowledge of the floating core potential. The proposed modeling method can be extended to the transformers as well as multiterminal magnetic devices. The experimental results verify the effectiveness of the proposed method.