Wide Output Voltage Range Applications Research Articles

An MV Hybrid Isolated DC Transformer for Wide Output Voltage Range Applications

DC transformer (DCT) is the key energy conversion equipment that converts medium voltage dc to low voltage dc. Aiming at the industrial loads requiring wide output voltage range and unidirectional power flow, a hybrid isolated DC transformer (HIT) as an alternative to the traditional MMC-DCT is proposed in this paper. It is composed by thyristors, diodes, and submodule (SM) based arms. The operation principle, circuit performance, and control strategy are introduced in detail. Particularly, a discontinuous input and continuous output currents (DICO) operation mode is further proposed to suppress submodule capacitor voltage ripple. Compared with the traditional MMC-DCT, HIT can save 50% SMs, 28% semiconductor cost and 46.3% total SM capacitance. The effectiveness and the theoretical analysis have been confirmed by both simulation and experimental results.

Multimode Control of WPT Systems for Efficiency Improvement in Wide Output Voltage Range Applications

Multimode Control of WPT Systems for Efficiency Improvement in Wide Output Voltage Range Applications

Hybrid full‐bridge converter with wide output voltage for high‐power applications

A hybrid full-bridge converter that consists of a secondary-side phase-shift full-bridge converter (SPS-FBC) and a full-bridge LLC converter is proposed in this study. The wide zero-voltage switching (ZVS) range of the primary switches can be achieved and the series inductor of the SPS-FBC converter does not need to be specially designed to help achieving the soft switching operation with a set of shared high frequency inverter circuits. The dual outputs of the proposed hybrid converter are connected in series, reducing the voltage stress of the power device in the secondary side. The whole dc-output voltage can be regulated by primary-side phase-shift and secondary-side phase-shift dual-mode control scheme within the desired voltage range, by which the two output voltages are regulated independently and free from cross-regulation. Therefore, the proposed converter is suitable for high voltage, high power and wide output voltage range applications. The working principle and steady-state characteristics of the proposed converter are presented and verified in experiment of a 3 kW prototype. The experimental results show that the proposed converter maintains high efficiency throughout the voltage range, and the peak efficiency is 97.43%.

An Improved LLC Resonant Converter With Reconfigurable Hybrid Voltage Multiplier and PWM-Plus-PFM Hybrid Control for Wide Output Range Applications

This paper proposes an improved LLC resonant converter with reconfigurable hybrid voltage multiplier for wide output voltage range applications. By adopting three legs and two active switches, the rectifier can be reconfigured to three configurations, i.e., full-bridge rectifier, hybrid voltage-multiplier rectifier and voltage-multiplier rectifier, covering the range of more than three times of the minimum output voltage. Compared with conventional LLC converter, the operating range of each configuration is narrowed so that the magnetizing inductance is optimized and switching frequency range is narrowed to achieve higher efficiency. Pulsewidth plus pulse-frequency modulation strategy is employed to achieve smooth transition between these operation modes. Zero-voltage switching of all power mosfet s and zero-current switching of all secondary-side diodes are achieved as well. Detailed operational principles, characteristics, design consideration, and control stagey of the proposed converter are analyzed. A 3.3 kW 150–450 V output prototype is built and tested to verify the effectiveness and advantages of the proposed converter.

Isolated Buck‐Boost converters with AC‐TLR and dual‐transformer structure for wide output voltage range applications

A novel isolated buck-boost (IBB) converter with a dual-transformer (DT) and an active-controlled three-level rectifier (AC-TLR) is proposed in this study. A new family of IBB converters is derived with different implementations of the AC-TLR. The two transformers in the converter supply power to the output alternatively through the phase-shift control of the active switch in the AC-TLR. A voltage-doubler configuration is built and three voltage levels are generated with the DT and AC-TLR structure. Therefore, the diodes and switches in the rectifier sustain only half of the high-output voltage and turns ratios of the transformers are reduced. In addition, the zero-voltage-switching operation of all the active switches on both the primary and secondary sides is achieved and the reverse-recovery problem of all the diodes is alleviated in the wide operation range. Furthermore, the output voltage of the converter is regulated in a wide range due to the buck and boost voltage conversion characteristics of the converter. The operational principles, modulation and characteristics of the converter are presented. Finally, a 400 V input and 350-750 V output prototype is built and tested to verify the effectiveness of the proposed converters.

Interleaved LLC Resonant Converter With Hybrid Rectifier and Variable-Frequency Plus Phase-Shift Control for Wide Output Voltage Range Applications

A family of two-phase interleaved LLC (iLLC) resonant converter with hybrid rectifier is proposed for wide output voltage range applications. The primary sides of the two LLC converters are in parallel, and the connection of the secondary windings in the two LLC converters can be regulated by the hybrid rectifier according to the output voltage. Variable frequency control is employed to regulate the output voltage and the secondary windings are in series when the output voltage is high. Fixed-frequency phase-shift control is adopted to regulate the configuration of the secondary windings as well as the output voltage when the output voltage is low. The output voltage range is extended by adaptively changing the configuration of the hybrid rectifier, which results in reduced switching frequency range, circulating current, and conduction losses of the LLC resonant tank. Zero voltage switching and zero current switching are achieved for all the active switches and diodes, respectively, within the entire operation range. The operation principles are analyzed and a 3.5 kW prototype with 400 V input voltage and 150–500 V output voltage is built and tested to evaluate the feasibility of the proposed method.

A Novel Phase-Shift Dual Full-Bridge Converter With Full Soft-Switching Range and Wide Conversion Range

This paper proposes a novel phase-shift dual full-bridge converter with shared leading leg and dual outputs in series. Full soft-switching range of the active switches can be achieved based on the parallel full-bridge configuration of the converter, and the dual outputs of the proposed converter are connected in series. The output voltage can be regulated by primary-side phase-shift and secondary-side phase–shift dual-mode control scheme, and a wide conversion range can be achieved. Furthermore, the circulating current in the primary-side full-bridge circuits can be extinguished. Therefore, the proposed converter would be useful for constant peak power and wide output voltage range applications. Steady-state operation and relevant analysis results of the proposed converter are presented and verified on a 1.5-kW hardware prototype. The experimental results show that the proposed converter can achieve a peak efficiency of 95.3%.