Time-Domain-Based Superposition Analysis for Triple Active Bridge and Its Application for ZVS and Current Stress Optimization

In this paper, a current fed triple active bridge (TAB) based multiport converter (MPC) for DC mircrogrid (DCMG) application is analyzed considering full range variation of the input voltage and load power. A generalized frequency domain modeling approach is proposed in order to reduce the design complexity. This modeling approach can be extended to higher order MPCs with `n' winding transformer coupled converters. A modified duty ratio control scheme is proposed to minimize the transformer rms current and extend zero voltage switching range. A detailed analysis is performed to identify the zero voltage switching (ZVS) region over the whole operating range of the converter. A laboratory prototype of 2kW is built to verify the proposed modulation strategy and theoretical analysis.

The paper presents a two phase shift control strategy for Dual Active Bridge(DAB) and Triple Active Bridge(TAB) converter to eliminate the dc transients from the high frequency transformer winding currents during operating phase angle change from one cycle to the next cycle. The proposed two phase shift method controls the alternating nature of high frequency current in transformer windings in one switching cycle without using any high frequency current sensor. The proposed control strategy applies two different phase shift angles during positive and negative half cycles in order to eliminate the dc transients from transformer winding currents during steady state phase angle change. The control strategy is analyzed and applied for power flow direction reversal of Dual Active Bridge Converter and for changing power flow mode from three port scenario to two port scenario in case of Triple Active Bridge converter. The proposed control strategy study has been verified by performing experimental study on a hardware prototype.

A modified extended-phase-shift (EPS) control is proposed to decrease the control complexity and achieve full load range zero-voltage-switching (ZVS) for dual-active-bridge dc-dc converters. In the proposed solution, a fixed duty cycle is added, and the magnetizing current is utilized to achieve full load range ZVS. In addition, two control variables are decoupled, because the control of duty cycle is only determined by the voltage conversion ratio, which is not affected by the phase shift angle. The ZVS models considering junction capacitors and magnetizing inductance, ZVS regions under full load range, and derivation of control law are analyzed in detail. Finally, the effectiveness of the proposed solution is verified by experimental results from a 500W, 250kHz GaN-Based prototype.

Three-phase triple-voltage dual-active-bridge (T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -DAB) converter possesses high input voltage and large output current capacity, which can be adopted to constitute a high-power-density dc transformer. However, when employing conventional phase-shifted (PS) control strategy, zero-voltage switching (ZVS) turn-on is easily lost under light-load and voltage-mismatching situations. Hence, this article presents an optimized asymmetrical duty-cycle modulation strategy for T <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> -DAB converter, ensuring ZVS for switches and reducing the current stress over wide power and voltage ranges. The detailed model is established with a time-domain analysis method, and ZVS constraints are given with the particular consideration of dead time and parasitic capacitances of switches. Then, the MATLAB optimization toolbox is adopted to calculate the optimum duty cycle and PS angle, and the specific control scheme is introduced. Finally, a 2-kW prototype is built to verify the theoretical analysis, whose input voltage ranges from 480 to 720 V and output voltage is 200 V. The experimental results show that the proposed optimized control scheme can realize ZVS turn-on for all switches over wide voltage and power ranges, and the efficiency is improved, especially under light-load and voltage-mismatching situation.

A comprehensive procedure for the derivation of optimal, full-operating-range zero voltage switching (ZVS) modulation schemes for single-phase, single-stage, bidirectional and isolated dual active bridge (DAB) ac-dc converters is presented. The converter topology consists of a DAB dc-dc converter, receiving a rectified ac line voltage via a synchronous rectifier. The DAB comprises primary and secondary side full bridges, linked by a high-frequency isolation transformer and a series inductor. ZVS modulation schemes previously proposed in the literature are either based on current-based or energy-based ZVS analyses. The procedure outlined in this paper for the calculation of optimal DAB modulation schemes (i.e., combined phase-shift, duty-cycle, and switching frequency modulation) relies on a novel, more accurate, current-dependent charge-based ZVS analysis, taking into account the amount of charge that is required to charge the nonlinear parasitic output capacitances of the switches during commutation. Thereby, the concept of “commutation inductance(s)” is shown to be an essential element in achieving full-operating-range ZVS. The proposed methods are applied to a 3.7 kW, bidirectional, and unity power factor electric vehicle battery charger which interfaces a 400 V dc-bus with the 230 Vac, 50-Hz utility grid. Experimental results obtained from a high-power-density, high-efficiency converter prototype are given to validate the theoretical analysis and practical feasibility of the proposed strategy.

Integration of the on-board charger (OBC) and auxiliary power module (APM) in electric vehicles (EVs) can reduce the overall weight, volume and cost of the on-board charging system, as well as increase efficiency. This paper proposes optimized modulation strategies for an integrated on-board charger (IOBC) based on triple-active-bridge (TAB) converter. The proposed multiport converter is capable of charging the high-voltage (HV) and low-voltage (LV) batteries simultaneously from the grid. In addition, the HV and LV batteries can also be charged individually from the grid without the need of additional mechanical switches or relays, due to the proposed 5-degrees-of-freedom (DOF) modulation scheme. Detailed loss analysis of TAB is presented for the first time, targeting a simple and accurate estimation of the converter losses. Furthermore, four optimization schemes are proposed aiming to improve the performance of the integrated charger, including reduction of the converter total loss and zero-voltage-switching (ZVS) turn-on for all converter devices. A constant-current/constant-voltage (CC/CV) charging scheme is considered for both HV and LV batteries and the results of the optimization schemes are evaluated using a 4.3 kW experimental prototype, while the measured converter efficiency with the proposed optimization schemes reaches 96.1% at nominal power levels.

This paper presents a control technique for flying capacitor multi-level (FCML) converters to achieve zero-voltage switching (ZVS) across the full range of duty cycles, with application in high power density and high efficiency power converters. Previous works have used variable frequency control to enable ZVS at specific duty cycles in FCML converters, but have not been able to use these methods to allow ZVS across the full range. This work uses dynamic level selection and variable frequency control to increase inductor current ripple at duty cycle ranges for which ZVS was previously unattainable. An experimental 5-level FCML prototype has been built using GaN devices on a single-sided PCB to demonstrate this control technique. We demonstrate 4-level and 5-level operation with ZVS at duty cycles that are not possible with 5-level operation alone, as well as a dynamic level transition with active capacitor voltage balancing.

This paper proposes a three-level bidirectional DC-DC converter with an auxiliary inductor for wide zero-voltage switching (ZVS) in high-output voltage applications. The auxiliary inductor is connected across the middle node of the split flying capacitors and the center tap of the secondary winding in the transformer. The phase-shift angle in three-level stage can facilitate the ZVS of the switches in thee-level stage. The modulation trajectory to maintain the full-operation ZVS range with low condition loss is proposed. Finally, the experimental results verify the theoretical analyses and ZVS performance across the whole power and voltage range, and the efficiency curves demonstrate the efficiency improvement.

The paper presents two types of one cycle current control method for Triple Active Bridge(TAB) phase-shifted DC-DC converter integrating Renewable Energy Source(RES), Energy Storage System(ESS) and a output dc bus. The main objective of the current control methods is to control the transformer current in each cycle so that dc transients are eliminated during phase angle change from one cycle to the next cycle. In the proposed current control methods, the transformer currents are sampled within a switching cycle and the phase shift angles for the next switching cycle are generated based on sampled current values and current references. The discussed one cycle control methods also provide an inherent power decoupling feature for the three port phase shifted triple active bridge converter. Two different methods, (a) sampling and updating twice in a switching cycle and (b) sampling and updating once in a switching cycle, are explained in this paper. The current control methods are experimentally verified using digital implementation technique on a laboratory made hardware prototype.

The Three-level Dual-Active-Half-Bridge (TL-DAHB) reduces the voltage withstand level but increases the current stress compared to the Dual-Active-Bridge (DAB). This paper designs a current stress optimization algorithm by Karush-Kuhn-Tucker (KKT) condition to solve the problem of higher current stress in TL-DAHB and proposes the optimal control of current stress by combining with Dual-Phase-Shift (DPS) control. Finally, the feasibility of current stress optimization control is verified by building a Simulink model.

The <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter in the above-resonance operation mode is gaining popularity in high-voltage generator applications due to its favorable characteristics, including zero-voltage switching (ZVS), step-up capability, and the absorption of parasitics. Nevertheless, with the increase of the voltage gain <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G_{o}$</tex-math></inline-formula> of the resonant tank, the ZVS condition is undermined for the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter. This study aims to characterize the ZVS condition of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter in the above-resonance operation mode. For this purpose, a two-step-based ZVS analysis is carried out, incorporating the partial steady-state analysis and the dead-time analysis. The outcome of this analysis is the derivation of a set of three necessary conditions that define a sufficient ZVS condition model of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter in the above-resonance operation mode. According to the analytical dead-time analysis, a discriminator <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> representing the ZVS performance of the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter is demonstrated, and the ZVS condition can only be achieved when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$&gt;$</tex-math></inline-formula> 0. Moreover, the analysis of the sign of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\Delta$</tex-math></inline-formula> reveals that the <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter exhibits a weaker ZVS condition when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G_{o} &gt;$</tex-math></inline-formula> 1 than when <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$G_{o}$</tex-math></inline-formula> <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\leq$</tex-math></inline-formula> 1. On the basis of the proposed ZVS condition model, a design method is proposed to illustrate the influence of the ZVS condition on the output of the step-up <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter. Finally, experimental results obtained from a prototype of a 1053-V 222-W output <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$LCC$</tex-math></inline-formula> resonant converter are included to validate the accuracy of the theoretical analysis.

본 논문에서는 영전압 스위칭(ZVS)과 전류불연속 모드(DCM)에 의한 새로운 고효율의 DC-DC 컨버터에 대해 연구된다. 일반적으로 고효율의 컨버터를 만들기 위해서는 전력변환기내에 사용된 반도체 스위칭 소자의 손실을 최소화하여 이루어진다. 제안한 컨버터는 DCM에 의하여 스위치의 턴-온 동작을 영전류 스위칭(ZCS)으로 만들고, 또한 새로운 유사공진 회로를 접목하여 컨버터의 고효율을 실현시킨다. 제안한 컨버터에 사용된 제어용 스위칭 소자들은 유사공진 기법에 의해 소프트 스위칭, 즉 ZVS와 ZCS으로 동작시키고, 이에 따른 제어용 스위칭 소자들은 전압과 전류의 스트레스 없이 동작한다. 그 결과 제안한 컨버터는 스위칭 손실의 저감에 의해 고효율로 구동된다. 제안한 DCM-ZVS 컨버터의 소프트 스위칭 동작과 시스템 효율은 디지털 시뮬레이션과 실험결과를 통해 그 타당성이 입증된다. This paper is study on a new high efficiency DC-DC converter of discontinuous conduction mode (DCM) with zero voltage switching (ZVS). The converters of high efficiency are generally made that the power loss of the used semiconductor switching devices is minimized. The proposed converter is accomplished that the turn-on operation of switches is on zero current switching (ZCS) by DCM. The converter is also applicable to a new quasi-resonant circuit to achieve high efficiency converter. The control switches using in the converter are operated with soft switching, that is, ZVS and ZCS by quasi-resonant method. The control switches are operated without increasing their voltage and current stresses by the soft switching technology. The result is that the switching loss is very low and the efficiency of the converter is high. The soft switching operation and the system efficiency of the proposed DCM-ZVS converter are verified by digital simulation and experimental results.

A zero-voltage switching (ZVS) pulse-width-modulation (PWM) single-phase inverter using a ZVS transformer-isolated step-up/down dc link is presented in this paper. The proposed ZVS transformer-isolated step-up/down dc link not only makes the switches in single-phase inverter can operate at ZVS condition, but it has a step-up/down input voltage function and it provides an isolation function. Moreover, the switches in itself also operate at ZVS. Except for the switch in the ZVS-PWM auxiliary circuit of the proposed ZVS transformer-isolated step-up/down dc link, all power semiconductor devices in proposed inverter operate at ZVS turn on and turn off. The switch in the ZVS-PWM auxiliary circuit of proposed ZVS transformer-isolated step-up/down dc link operates at zero-current-switching (ZCS) turn-on and turn-off. Thus, the switching losses can be reduced. The proposed ZVS-PWM inverter operates at constant frequency. The voltage stress and current stress on the main semiconductors in the proposed ZVS-PWM inverter are the same them in conventional hard switching inverter. The analysis of operation principle and experimental results of the proposed ZVS-PWM inverter, rated 2 kW and operated at 40 kHz, are provided in this paper to verify the performance.

Two new soft-switching converters for switched reluctance motor drives are proposed and analyzed. The proposed zero-voltage-transition (ZVT) converter possesses the definite advantages that both main transistors and diodes can operate with zero-voltage switching (ZVS), as well as unity device voltage and current stresses. On the other hand, the proposed zero-current-transition (ZCT) converter offers the advantages that both the main and auxiliary switches operate with zero-current switching (ZCS), as well as minimum current and voltage stresses. Both converters have the merits of simple circuit topology, minimum component count and low cost.

For an LLC converter, it is difficult to realize the wide output range with conventional pulse frequency modulation control because of the limited operating frequency. This paper proposes a new hybrid control method. The proposed strategy combines the burst-mode control and phase-shift control methods for the LLC converter. The burst-mode control can regulate the output voltage from zero to its maximum value, and the phase-shift control can reduce the increased resonant current during burst-on time. By using this method, the wide output voltage range is realized with the low resonant current during burst-on time and zero-voltage switch (ZVS) for all switches. The reliability and efficiency of the converter can be improved accordingly. The burst duty ratio is regulated by the reference output voltage, and the phase-shift angle is derived when realizing ZVS for lagging-leg switches. Moreover, the resonant parameters and the maximum phase-shift angle are optimized under the constraints of current stress and ZVS condition. This method is easy to be implemented in a low-cost microcontroller because high-frequency real-time calculations are not necessary. A 1.5-kW prototype is built to verify the feasibility and validity of the proposed control method.