Triple Phase Shift Modulation Research Articles

Non-inverting and Non-isolated Magnetically Coupled Buck–Boost Bidirectional DC–DC Converter

A new non-isolated dc–dc converter with non-inverting output and buck–boost operation, named magnetically coupled buck–boost bidirectional (MCB3) converter, is presented in this article. The MCB3 passive components arrangement connects the input and output ports getting an equivalent behavior to that of the dual active bridge (DAB) converter, but in a non-isolated topology. This equivalency allows applying Triple Phase Shift (TPS) modulation to MCB3. TPS is known to minimize conduction losses and to achieve soft switching at any load in the DAB converter. Throughout the article, the features of the DAB converter are used as a reference to show the main features of the proposed converter. Moreover, other modulation strategies based on TPS modulation are used in MCB3 to operate within the minimum losses path. The multiple operation modes found on the MCB3 under TPS modulation are identified, classified, and used to find the operating points that minimize the switching and conduction losses over the power range. The analysis is shown for the boost mode that is the worst case design. MCB3 and DAB topologies are designed and simulated for the same specification to validate the theoretical study. Finally, experimental measurements on 460-W prototypes for both topologies corroborate the equivalent operation and the main features of the MCB3.

Unified ZVS strategy for DAB with triple‐phase‐shift modulation in boost mode

In this study, the switching mode and working waveform of dual active bridge (DAB) converter under triple phase-shift modulation scheme is analysed, and an ALL-ZVS (zero voltage switching) control strategy of all devices for full-power range with voltage transfer ratio M > 1 is proposed. First, a feasible control domain of ALL-ZVS is derived by analysing the constraints of the control variables of ZVS for all switching devices under different operating modes. On this basis, an ALL-ZVS control strategy of current RMS quasi-optimisation under the condition of M > 1 is proposed with the existing inductor current RMS optimisation control algorithm. It can be concluded that the proposed control strategy not only eliminates the switching loss, but also reduces the conduction loss, greatly improves the efficiency of the DAB converter. Finally, an experimental platform is built, and the experimental results verify the correctness and effectiveness of the proposed control strategy.

A Simple Unified Model for Generic Operation of Dual Active Bridge Converter

This paper presents a simple and generic model of a dual active bridge converter valid throughout its range of operation. It is suitable for all operating modes and modulation strategies such as phase-shift, extended phase-shift, dual phase-shift, or triple phase-shift modulation. It hypothesizes that any mode of its operation characterized by the duty ratios ( $d_1$ , $d_2$ ) of the two full-bridge converter ac voltages and the phase shift ( $\phi$ ) between them can be decomposed into four parallel dual active bridge circuits operating in simple phase-shift modulation. The hypothesis is proven mathematically; the average and small-signal models are derived and validated through simulations and experiments on a hardware prototype.

General Analysis of Switching Modes in a Dual Active Bridge with Triple Phase Shift Modulation

This paper provides an exhaustive analysis of the Dual-Active-Bridge with Triple-Phase-Shift (DAB-TPS) modulation and other simpler ones, identifying all the possible switching modes to operate the DAB in both power flow directions, and for any input-to-output voltage range and output power. This study shows four cases and seven switching modes for each case when the energy flows in one direction. That means that the DAB operates up to fifty-six different switching modes when the energy flows in both directions. Analytical expressions for the inductor current, the output power, and the boundaries between switching modes are provided for all cases. Additionally, the combination of control variables to achieve Zero-Voltage-Switching (ZVS) or Zero-Current-Switching (ZCS) is provided for each case and switching mode, by showing which switching modes obtain ZVS or ZCS for the whole power range and all switches—independent of the input-to-output voltage ratio. Therefore, the most interesting cases, switching mode and modulation for using the DAB are identified. Additionally, experimental validation has been carried out with a 250 W prototype. This analysis is a proper tool to design the DAB in the optimum switching mode, reducing the RMS current and achieving to increase efficiency and the power density.

An Improved Generalized Average Model of DC–DC Dual Active Bridge Converters

Improvements are proposed for generalized average models of dual active bridge (DAB) converters. Generalized average modeling involves a tradeoff between accuracy and tractability. To maintain an acceptable level of complexity, existing DAB models are derived using a first harmonic approximation. These models provide accurate small-signal representations, but are limited as large-signal analysis tools due to persistent steady-state error. This study proposes a modeling framework that provides accurate large and small-signal models without significant increases in the overall complexity. The framework describes DAB operation with a triple phase shift modulation, and is easily simplified for single, dual, or extended phase shift modulation schemes. The special case of a single phase shift modulation, which experiences the most significant large-signal error, is given additional consideration. The framework is applied to open and closed-loop operation, and both large- and small-signal models are discussed. Models are validated in simulation and hardware experiments using a small scale DAB prototype.