This paper presents an alternative method for achieving more efficient and reliable DC-DC conversion and balancing operations for low-power applications in a stacked voltage domain. This work comprehensively analyzes the operating principles and power conversion loss of a proposed capacitorstacking balancing circuit at the system level. The analysis and design of the capacitor-stacking balancing circuit in the stacked voltage domain, including the time-domain operation, voltage equation, and dead-time effect, are explored and implemented. This study provides an opportunity to achieve a highly optimized system with high efficiency. A comprehensive analysis of efficiency at the system level shows the advantages and limitations according to each stacking method under a given system condition. Considering the redundancy issues of the previous method at system-level analysis, the capacitor-stacking balancing method is a preferable choice for low-power, high-reliability, and high-efficiency applications under light load conditions. This study also provides an analytical efficiency model under current imbalance, which is a notable difference from previous research and case studies concerning power converters. Prototype board with lithium-ion battery power and a core voltage of 0.825 V-a low-power application-was built to verify the proposed model and analysis. The experimental efficiency reached 94.9% at 20% of the maximum workload.
In AC/DC power distributions networks, power converters are interfacing buses to ensure DC voltage regulation and power distribution. Active front ends are used between AC and DC buses and two typical control schemes that can be implemented are voltage regulation or power regulation. On the DC side, open‐loop operated DC transformers could be used between two DC buses to provide voltage adaptation, isolation and natural power flow. In this context, power flows and DC bus voltages in the power distribution network are dependent on the combined operation of the active front ends and the DC transformer. Mainly studied from a stability perspective, this interdependency between active front ends and DC transformers has lacked investigations in terms of dynamics. Fast dynamics is nevertheless important to operate optimally a network. In this paper, the assessment of the dynamic performance for distribution systems with DC transformers is performed for different mixes of voltage regulating and power regulating active front ends. The influence of DC line length and DC transformer power reversal method on the system is further investigated. A model of the system is proposed, validated experimentally and can be used to aid system level design and analysis of future DC systems.
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