The ability to concurrently power multiple loads has been a new feature for the inductive power transfer (IPT) system in more applications, such as the gate driver powering in the modular multilevel converter. As one of the applicable configurations, the domino-type IPT system cannot only transfer power over a longer distance but also achieves load-independent outputs. This article reviews the existing multiple-load IPT systems and aims to provide a methodology to systematically construct suitable domino-type IPT topologies with multiple load-independent constant-current (CC) or constant-voltage (CV) outputs. There are three innovative contributions. First, three kinds of resonant circuits are summarized to achieve the compensation network, including the series–series, T-type, and Π-type topologies. Second, nine CC and nine CV topologies are proposed, analyzed, and evaluated as candidates for various applications. The optimal CC and CV topologies are identified, and the integrated magnetic coupler designs are provided accordingly. Third, the power transfer capability is investigated, considering the parasitic resistances of passive components. The attenuation of load currents/voltages and the system efficiency relationship with load resistance, coupling coefficient k , quality factor Q , and load number N are analyzed, providing the guideline to design the load-independent domino system with high system efficiency. A single-input-four-output domino-type IPT system is implemented to validate the effectiveness of the proposed design methodology. Experimental results have shown consistency with the analysis results, and the efficiency can reach 89.79% when k = 0.193, Q = 320, and N = 4.

This article introduces a 4 kV/120 A solid-state dc circuit breaker (DCCB) based on discrete SiC mosfets. The DCCB is designed in a five-layer tower structure. Each layer consists of a circular main conduction branch and an attached gate driver. There are two primary benefits of the proposed DCCB. First, it reduces conduction loss with multiple devices in parallel. Second, it achieves an ultrafast response speed with SiC mosfets. Moreover, the gate drivers of the DCCB are powered by a domino inductive power transfer (IPT) system. It achieves the load-independent constant-voltage output characteristics, which means the outputs are immune to load variations. An IPT system prototype is implemented to test the power transfer performance. At 500-kHz frequency, the total output power reaches 15.73 W, which is sufficient to power on five gate drivers, with a peak transfer efficiency of 75.4%. The IPT system is tested to power a 4 kV/120 A DCCB prototype. It validates that the DCCB is effective to turn off 120 A current within 3.5 μs.

This article proposes a load-independent domino-type inductive power transfer (IPT) system for multiple loads with a simple structure and a long-distance transfer capability. Hybrid constant-current (CC) and constant-voltage (CV) outputs are achieved. Compared to existing designs, there are two innovative contributions. First, the proposed domino-type IPT topology uses fewer coils and ferrite materials to achieve load-independent outputs, which significantly simplifies system structure and improves power density. Second, a unipolar domino coupler configuration is proposed, enabling the long-distance power transfer capability as well as suppressing the cross-coupling effect. With the proposed IPT topology, the magnetic coupler design is provided and validated by three-dimensional finite-element analysis. Impacts of parasitic resistances are analyzed, revealing the practical output attenuation versus load variation and the efficiency relationship with load resistance, coupling coefficient k, quality factor Q, and load number N. With an efficiency-based parameter design method provided, a 330-W single-input-four-output prototype is implemented over a total transfer distance of 0.9 m with a 300 mm×300 mm domino coupler. Experimental results validate the load-independent CC and CV outputs, and the efficiency can reach 83.78% at N = 4 and k = 0.055.

Metal oxide varistors (MOVs) are usually applied to clamp the voltage across a DC circuit breaker (DCCB). This letter focuses on the transient process of a DCCB turn-off and has three contributions. First, it reveals that snubber circuit inductance, the internal and external stray inductances of an MOV could cause a significant overvoltage across a DCCB, which exceeds 47.5% of its clamping voltage. The overvoltage mechanism is clearly analyzed, providing equations to estimate overvoltage. Second, a non-linear model of an MOV is proposed to simplify the calculation and provide an accurate estimation. Third, a new arrangement of series submodules (SMs) with discrete MOVs is proposed to suppress overvoltage. A hybrid 500 kV/25 kA DCCB prototype with series IGBTs is implemented to validate the proposed analysis. The series-IGBT rating voltage is 1440 kV, and the MOV with a nominal clamping voltage of 800kV is used to protect IGBTs. However, a 25kA turn-off experiment clearly shows that the overvoltage increased to 1203 kV by an external stray inductance of 39.5μH and di/dt of 1480 A/μs. The relative error between measurements and simulations is within 3%. Besides, simulations on the new arrangement show the overvoltage is decreased by 23.4% than before.

In the HVdc circuit breaker testing process, a thyristor is used to generate high current for the testing purpose. However, the reverse recovery process (RRP) of a thyristor can induce a significant overvoltage problem, which jeopardizes the reliable operation. It is important to model the RRP of a thyristor. The existing modeling methods usually omit the stray inductances in the circuit, which cannot describe the hard-switching process accurately. Therefore, this article proposes a novel method to model the RRP, considering the stray inductances. There are mainly three original contributions. First, the physical mechanism of the RRP is analyzed, describing the internal charge behavior and dividing the RRP into two stages. Second, this article provides a novel trigonometric exponential (TE) model of the thyristor voltage and current with analytical equations. Third, the extraction method of model parameters is also provided based on external circuit parameters and thyristor characteristics. In order to verify the proposed modeling method, a 1 kV/830 A IGBT-based circuit breaker is implemented with a thyristor to initialize the current. The experimental results show that the negative peak voltage induced by the RRP is as high as 4.26 kV, and the proposed TE model can precisely predict the overvoltage with a relative error of 7.51%.

This study proposes a detuned resonant capacitor selection strategy to eliminate the influence of the changed coupling coefficient on the transferred power and efficiency of a wireless power transfer (WPT) system using the LCC-S resonant topology. The output characteristics of the conventional tuned LCC-S system and the novel detuned system are analyzed and compared in detail, the different effects of the detuned parameters on the system output performance are expounded by simulations, and an optimal detuned parameter design process is presented. By adjusting the compensated capacitors on the transmitting side, the output voltage can be constant under varying coupling conditions without changing the switching frequency. Experiments with a 1.5kW power scale were conducted to verify the proposed theoretical analysis. The results show that the fluctuation of the output voltage is restricted to 8.2% in the optimized system when the coupling coefficient changes from 0.18 to 0.38. Under the rated coupling conditions, the experimental results demonstrate that compared with ZPA (88.29%) and ZVS (90.66%), ZCS (91.52%) operating conditions are more suitable for a WPT system equipped with IGBTs to improve the overall efficiency.