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Three-phase CLLC resonant converters provide higher power conversion capability as compared to half-bridge and full-bridge structures. In addition to the unique features of CLLC converters for bidirectional applications, the three-phase structure provides significantly reduced output current ripple (smaller output capacitor), parallel power processing (reduced components size and current peak stress), and better thermal distribution (smaller heatsinks). However, with practical, i.e., nonzero, resonant component tolerances, these benefits are normally less, and sometimes significantly less than expected in the ideal case. In this article, the unbalanced behavior of the converter with 15 unknown resonant components is identified and analyzed. A new analysis methodology is proposed to investigate the worst-cases of current-sharing among above 32 000 possible scenarios in three-phase CLLC resonant converters. In addition, this article shows that phase-shifting techniques can be effective to mitigate the unbalanced behavior of the converter. The proposed analysis in this article helps to determine the highest admissible tolerance in the components to keep the converter working within a certain range of unbalanced behavior without requiring any balancing techniques. The proposed analytical framework is verified with experimental and simulation results of a 3-kW bidirectional three-phase CLLC experimental prototype. [ABSTRACT FROM AUTHOR]

Charge control for resonant converters introduces an inner feedback loop that improves the system dynamic characteristics. However, small-signal modeling is not as straightforward with charge-controlled resonant converters as it is with current mode hard-switching topologies, due to the nature of resonant behavior. Conventional small-signal models for charge-controlled resonant converters are developed based on the converter input and output energy balance. This simplified approach overlooks the dynamics of the magnetizing inductor current and generates errors in small-signal frequency response. To improve the analytical model and enable high-bandwidth design, this article proposes a new methodology for modeling charge-controlled resonant converters. The energy stored in the resonant tank is analyzed using the theory of extended describing function, which accounts for the effect of the magnetizing current. This methodology applies to a wide range of charge control variants, such as bang-bang charge control and hybrid-hysteretic control. To demonstrate the modeling procedure, this article considers a high-order, five resonant-component half-bridge CLLC resonant converter as a case study. The proposed analytical model is applied to a 1 kW, 400-V/3.3-A power supply prototype for simulation and experimental validation. The proposed model successfully predicts the frequency response of the resonant converter across frequency and load conditions, providing rapid frequency-domain evaluation in the design process. [ABSTRACT FROM AUTHOR]

Three-phase pulsewidth-modulated converters require closed-loop controllers to meet the performance requirements and to achieve reliable responses over the entire operating range. Conventionally, by using the synchronous reference frame (SRF) representation, different linear and nonlinear control strategies have been proposed to improve the converter's dynamic performance. However, the achieved improvements cannot be objectively assessed due to the absence of a performance limit standard reference of the converter's dynamics. In this article, the theoretical minimum time solutions for three-phase converters in the SRF are derived and analyzed, providing an objective reference point for the system's dynamic performance evaluation. The normalized dynamic model of the converter in the SRF is derived and combined with the time-optimal control principle to find the theoretical minimum transient time solutions. The state-plane representation of these minimum time responses enables a straightforward and comprehensive interpretation of the converter's dynamic behavior, and it simplifies the derivation of closed-form expressions that characterize the minimum time transient parameters. The introduced analysis, minimum time dynamic responses, derived transient's expressions, and dynamic performance evaluation are validated by simulation and experimental results. [ABSTRACT FROM AUTHOR]