Wide Input Output Voltage Research Articles

Variable Switching Frequency for ZVS over Wide Voltage Range in Dual Active Bridge

The Dual Active Bridge (DAB) converter is known for its advantageous characteristics, including bidirectionality, galvanic isolation, and soft-switching operation. However, achieving Zero Voltage Switching (ZVS) across the complete operation range is not guaranteed, particularly through a wide input–output voltage ratio. This paper explores the integration of the switching frequency as a control variable in the DAB converter to ensure ZVS operation across a wide voltage range, employing Single Phase Shift (SPS) modulation. The study evaluated the RMS and reactive currents under variable switching frequency, presenting the advantages of this approach. Moreover, it includes a design-oriented analysis of the ZVS limits and their relationship with the switching frequency, aiming to ensure ZVS at any operating point. Experimental results validated the theoretical analysis, while presenting the main advantages of variable switching frequency implementation.

Bidirectional Interface Resonant Converter for Wide Voltage Range Storage Applications

In this paper, a bidirectional zero voltage switching (ZVS) resonant converter with narrow control frequency deviation is proposed. Wide input–output voltage range applications, such as flywheel or supercapacitors storage units are targeted. Due to symmetrical topology of resonant circuit interfaces, the proposed converter has similar behavior in bidirectional operating mode. We call it Dual Active Bridge Converter (DABC). The proposal topology of the converter is subjected to multi resonant circuits which make it necessary to study with multiscale approaches. Thus, first harmonic approximation and use of selective per unit parameters are established in (2) Methods. Then, the forward direction and backward direction of power flux exchange are detailed according to switching sequences. Switching frequency control must be completed within a narrow range. So, the frequency range deterministic parameters are emphasized in the design procedure in (3) Methods. A narrow range of switching frequency and a wide range voltage control must be ensured to suit for energy storage units, power electronic devices capabilities and electromagnetic compatibility. A 3 kW test bench is used to validate operation principles and to proof success of the developed design procedure. The interest of proposed converter is compared to other solutions from the literature in (4) Results.

Analysis of a Synergetically Controlled Two-Stage Three-Phase DC/AC Buck-Boost Converter

Three-phase DC/AC power electronics converter systems used in battery-powered variable-speed drive systems or employed in three-phase mains-supplied battery charger applications usually feature two power conversion stages. In both cases, typically a DC/DC stage is attached to a three-phase DC/AC stage in order to enable buck-boost functionality and/or a wide input-output voltage operating range. However, a two-stage solution leads to a high number of switched bridge-legs and hence, results in high switching losses, if the degrees of freedom available for controlling the overall system are not utilised. If the DC/DC stage is used to vary the DC link voltage with six times the AC-side frequency, a pulse width modulation (PWM) of always only one phase of the DC/AC stage is sufficient to achieve three-phase sinusoidal output currents. The clamping of two phases (denoted as 1/3 PWM) leads to a drastic reduction of the DC/AC stage switching losses, which is further accentuated by a DC link voltage which is lower than for the conventional modulation schemes. This paper details the operating principle of a three-phase buck-boost converter system using 1/3 PWM and outlines an appropriate control system design. Subsequently, the switching losses and the voltage/current stresses on the converter components are analytically derived. There, a more than 66% reduction of the DC/AC stage switching losses is calculated without any increase of the stress on the remaining converter components. The theoretical considerations are finally verified on a hardware demonstrator, where the proposed modulation strategy is experimentally compared against several conventional modulation techniques and its clear performance advantages are validated.

A Family of Ultrahigh Efficiency Fractional dc–dc Topologies for High Power Energy Storage Device

The application of a nonisolated bidirectional fractional dc–dc topology is proposed for high power energy storage device in this article. The proposed topology has the benefits of ultrahigh efficiency, simple structure, and low cost because it processes only a fractional of the total power. With the existence of an extra-low voltage (LV) power source, the converter voltage stress is only the difference between the dc bus and high voltage (HV) power source, therefore, low-cost LV transistors can be used in HV high power applications. Since a majority of the power is transferred directly between the energy storage device and dc bus, ultrahigh system efficiency can be achieved. Converter operating principle and design considerations such as battery capacity calculation methodologies and over voltage protection (OVP) are presented. A GaN transistor-based prototype is fabricated. Experimental results of a 1.2-kW battery energy storage prototype are presented to validate the analysis. The system efficiency is higher than 99% when a wide input–output voltage range is achieved. The fractional converter is convincing in achieving high efficiency and high conversion power with reduced cost for energy storage devices.

Zero-Voltage Switching Control of an Interleaved Bi-Directional Buck–Boost Converter With Variable Coupled Inductor

This paper investigates an approach for achieving zero-voltage switching of an interleaved bi-directional buck–boost converter over a wide input–output voltage operating range by utilizing a coupled inductor with a variable coupling coefficient. The approach is based on regulating the value of the coupling coefficient by means of a direct current depending on the converter conversion ratio, thereby controlling the amplitude and duration of the resonant voltage transition. The impact of the controllable value of the coupling coefficient on the equivalent inductance, the zero-voltage transition period, and the resonant amplitude is analyzed in detail by applying analytical modeling. In comparison to the converter with a fixed coupled inductor operating over a wide input–output voltage span, the variable coupled inductor significantly improves the soft-switching range and reduces the circulating energy. Outside of the controllable resonant amplitude region, the converter with a variable coupled inductor still achieves reduction in the duration of the resonant transition period. To validate theoretical analysis, experimental results are recorded on the gallium nitride interleaved bi-directional buck–boost converter prototype. Improvements in efficiency at both full and half loads in comparison to the prototype with a fixed coupled inductor are achieved.