Solid-State Transformer Power Sharing via Embedded Digital Equalization
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
ISOP-based solid-state transformers (SSTs) in data center applications face challenges with unequal power distribution and sharing among cells due to component tolerances, complicating control and increasing complexity and cost.
Innovation Solution
A power electronics multilevel converter with closed-loop control adjusts cell voltage references based on power reference deviations to equalize power among cells, using AC/DC and DC/DC converters with series and parallel connections, respectively, and a closed-loop control mechanism to manage power distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If ISOP-based multilevel converter topology is used to interface MV AC grid with LV DC grid, then power conversion capability and voltage rating distribution are improved, but control complexity and device complexity increase due to unequal power distribution among cells
Solution Approach 1:
The patent implements a feedback mechanism where each cell's closed-loop control continuously monitors its own power output and compares it with the average power of all cells. Based on this feedback, each cell autonomously adjusts its voltage reference to equalize power distribution across all cells, thereby reducing control complexity while maintaining power conversion capability
Solution Approach 2:
Each cell is equipped with independent closed-loop control that autonomously regulates its power output without requiring centralized control. The control system uses local measurements and self-adjusts voltage references, enabling self-service operation that simplifies overall system control while achieving equal power sharing among cells
2Ease of manufacture
If component tolerances are considered in ISOP topology, then manufacturing feasibility is improved, but power distribution equality deteriorates leading to unequal power sharing among cells
Solution Approach 1:
The patent dynamically changes the voltage reference parameter for each cell based on its measured power output. By adjusting this key parameter in real-time, the system compensates for component tolerances and manufacturing variations, achieving equal power distribution despite differences in cell characteristics
Solution Approach 2:
Each cell receives individualized voltage reference adjustment based on its specific power output characteristics. The control system applies local quality principles by treating each cell independently with customized control parameters, allowing compensation for manufacturing variations while maintaining overall system power equality
3Device complexity
If open-loop series resonant converter is used for DC/DC conversion, then device complexity is reduced, but power regulation precision and adaptability deteriorate
Solution Approach 1:
The AC/DC converter incorporates closed-loop control that continuously monitors cell power output and adjusts the voltage reference accordingly. This feedback mechanism provides the adaptability normally associated with complex control systems, enabling the simple series resonant DC/DC converter to operate effectively with precise power regulation
Solution Approach 2:
The system performs preliminary action by pre-adjusting the voltage reference of each cell before power conversion based on measured power deviations. This proactive adjustment ensures that the simple open-loop series resonant converter operates at optimal conditions, compensating for variations before they affect power distribution
Data Source
AI summary
A power electronics multilevel converter comprises one or more phase legs. Each respective phase leg of the one or more phase legs comprises a plurality of cells. Each respective cell of the plurality of cells comprises an alternating current (AC)/direct current (DC) converter, a closed-loop control and a DC/DC converter. The closed-loop control is configured to regulate the cell power transmitted by the AC/DC converter to a DC link of the respective cell in accordance with a cell power reference. The cell power reference depends on a cell voltage reference. The closed-loop control is further configured to adjust the cell voltage reference in dependence of a cell power reference deviation from an average power per cell. The average power per cell depends on the cell power references of the plurality of cells of all phase legs.