In this paper, the small signal model for a four-level flying capacitor multilevel (FCML) totem-pole PFC converter is presented. In contrast to conventional PFC converters, the state space equations for the FCML PFC converter in a complete switching cycle change over the line cycle. If the standard state space averaging technique is applied, it will only evaluate a single combination of state space equations corresponding to only one segment of the line cycle. Since the four-level FCML PFC converter consists of three different segments in one half-line cycle, this technique is not applicable to derive a comprehensive small signal model of the converter that is required for regulation and transient stability. Moreover, the effects of flying capacitors on the FCML PFC dynamics are nulled out using the average model due to their natural balancing capability. In this work, the Fourier analysis of time-interval modulated switched network is used to determine the closed form small-signal control to output frequency response and verify its accuracy with the experimental results. The dynamic characteristic of the FCML converter is also evaluated for the variations in the converter passive elements. Finally, a hardware prototype is designed, fabricated, and tested for ac input 120 Vac, 400-V dc output, and 1-kW power rating demonstrating peak efficiency of 98.48%, power factor 0.995 and THD of 4.26% to observe the system behavior under load step changes.

This paper centers around analyzing the impacts of device and circuit mismatches on paralleling the silicon carbide (SiC) MOSFETs in a high-frequency power converter. A multi-variable time dependent analytical model for the gate to source voltages ($V_{GS}$) of paralleled devices is developed for a comprehensive theoretical analysis. Consequently, this paper reveals the design method for the gate resistors for mitigating the influences of device and circuit parasitic components that are inherently present in a group of paralleled MOSFETs. Furthermore, a real-time dead-time tracking, based on the parameters extracted from the derived gate-charge analytical model to prevent false triggering due to the coupling effect between two devices having ultra-high voltage slew rate (dv/dt) in the mismatched half-bridge module, is carried out in the digital signal processor (DSP) environment. Case-by-case study incorporating a single parasitic component at a time is simulated and presented to validate the design process derived from the multi-variable analytical model. Experimental results captured from a modular Non-Inverting Buck-Boost (NIBB) prototype validate the theoretical analysis corresponding to the gate driver design process of paralleled devices and the dead-time optimization to suppress false triggering in the mismatched half-bridge. Finally, the proposed mechanism is employed to guide the gate driver peripheral circuitry design for a 200W all-SiC based modular PWM converter proof-of-concept.

With an objective to actively decouple the power flow of the output bridges of a Triple Active Bridge (TAB) converter topology, a novel control strategy is proposed in this paper. Closed form equations of power flow between the three bridges are obtained by modelling and characterizing the TAB structure as a three-port transmission network connected via line inductances using fundamental harmonic approximation (FHA). Various control parameters such as full-bridge duty ratios and phase-shift angles along with their effect of the port voltages and the power flows are explained in depth, that portray the interdependency of the power flows between the three ports. With the correlation obtained between the power flows and the control parameters, a Multi-Input-Multi-Output (MIMO) based control strategy is introduced that regulates the power flow for both the output side bridges independently. This is achieved by including cross-gain terms in the conventional control scheme that actively cancels out the coupling effect between the control loops. Further, to elucidate the effectiveness of the proposed control scheme, detailed simulation analyses have been presented. The results describe that due to the decoupled control scheme, the secondary side output voltage stays constant with a maximum variation of ±4%, for a sudden load reduction in the tertiary bridge. In addition to that, a 300W laboratory prototype is developed to observe the performance of the proposed control scheme and the results portray strong coherence with the simulation results, along with an end-to-end efficiency of 94.4%.

This paper presents the design and development of a Silicon Carbide (SiC) technology-based Non-Inverting Buck-Boost (NIBB) DC-DC power conversion unit for harsh space environment application with very high temperature (HT) (>150°C) and high radiation level. This work evaluates the capability of SiC bare dies for high temperature (>150°C) power electronics. The selection of critical passive components of the power converter is done through rigorous characterization of their performance metrics such as capacitance, inductance, leakage current, etc. under influence of increasing operating temperature. In this work, the design, prototype development, operation, and testing of a 100kHz, 100W NIBB DC-DC converter over the 25° - 200° C ambient temperature range is demonstrated. The designed converter provides up to a 3.5A output load and convert the input side battery voltage levels of 28V, 120V, and 160V to a configurable output voltage from 30V to 48V, used as a standard for NASA space missions. The converter power stage, including the power semiconductor devices, inductor, and ceramic input and output filter capacitors, were placed inside a temperature controlled chamber for testing and temperature-variant characterization. The MOSFET gate drive circuit, input power source, and output load were placed external to the environmental chamber. Results at 200°C environment report a peak full load efficiency of 91.3%, which validates the developed converter architecture to be a suitable candidate for high-frequency HT power conversion.

Shunt Active Power Filters (SAPF) are universally used to curtail current harmonics appearing in the utility grids due to abundance of non-linear loads. This paper elucidates a detailed design and operation of a two level SAPF. Various control schemes are described and a novel, but easily implementable control scheme is proposed so as to enhance the overall performance of SAPF. The proposed controller is self-adaptive in nature and does not require complex computations pertaining to current error limitation, as a standard Space Vector Pulse Width Modulation (SVPWM) technique is used. The proposed current controller overcomes inherent limitations of random voltage vector switching encountered in conventional hysteresis current controller based SAPFs and inconsistent switching leading to spurious spikes appearing in a modified approach of hysteresis current control. The compensation in terms of considerable curtailment of current harmonics is provided by the proposed controller, thus ensuring the best possible results. Detailed theoretical analyses and simulation studies are presented in the paper and the claimed performance of the proposed controller is evident from results. Additionally, the proposed controller ensures the scalability for any multi-level converter topology used for SAPFs. To verify the effectiveness of the proposed control, the SAPF system is simulated in MATLAB Simulink environment, and the results portray favorable outcomes with 1.28% lower source current THD and better EMI performance.

This paper presents a novel mathematical modeling and analysis technique for inductive wireless charging systems. Typically, LC resonance is the most common and basic physical phenomena enabling inductive power transfer (IPT). The work in this paper describes the limitations and inaccuracy of the fundamental harmonic approximation (FHA), which is widely used in the analysis of any resonant based compensation network. Our work introduces a new comprehensive analysis approach for modeling an IPT system, i.e. extended harmonics analysis (EHA), which accounts for the effects of multiple other odd order harmonics on the power transfer, voltage gain, voltage and current stresses on the devices; and hence, provides more accurate design guidelines. As verification of this concept, a laboratory prototype of the wireless charging system is built and tested up to 1 kW and analyzed using both FHA and EHA. It is shown that the deviation of the current estimates from the experimental measurements using EHA is reduced to ~1 % from a maximum deviation of ~11 % obtained from FHA. Also, the use of EHA modeling has reduced the deviation from experimentally measured voltage gain to 9.6% from 28% in the case of FHA modeling.

This paper proposes a novel resonant active-clamped soft-switching method for a three-phase six-switch boost power factor correction rectifier, where all the main switches can undergo zero voltage switching (ZVS). It is realized by an additional efficient auxiliary circuit. The additional soft-switching circuit consists of three active switches and one resonant inductor. The ZVS for all the six switches can be ensured by proper selection of resonant parameters. Although the soft-switching auxiliary circuit consumes 3 active switches, the analysis in this manuscript shows that zero-voltage switching can also be achieved in these auxiliary switches, without any extra losses for the auxiliary circuit. A 2.2-kW three-phase boost PFC prototype with the additional auxiliary circuit for soft-switching is developed and tested to verify the occurrence of ZVS at the six switches with the proposed circuit. The experimental results show a reduction in total loss by 40% and hence, an increase in conversion efficiency from 98.2% to 99% at 2.2kW load power with maintaining unity power factor.