DC-DC Converter Master-Slave Control for Circulating Current Suppression
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Solution Overview
Problem
In electrical networks with DC-DC converters connected in parallel, circulating currents arise due to load fluctuations and different connection impedances, leading to energy losses and unstable control, particularly when high transmission speeds are required to prevent these currents.
Innovation Solution
Implementing a master/slave configuration for DC-DC voltage converter units, where one converter operates as a master using current mode control and the others as slaves, with a preconditioning function that evaluates output voltage to determine the operating mode and reference voltage, eliminating the need for load current transmission and allowing quick reaction to voltage dips without unstable control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If DC-DC converters are connected in parallel to increase power capacity, then the power supply capability is improved, but circulating currents arise due to load fluctuations and different connection impedances, leading to energy losses and unstable control
Solution Approach 1:
The patent divides the parallel-connected DC-DC converter system into master converters and slave converters. The master converters independently control their output based on local voltage feedback, while slave converters follow the master's reference voltage. This segmentation eliminates the need for complex inter-converter communication and prevents circulating currents by ensuring all converters operate from a unified reference without continuous data transmission.
Solution Approach 2:
Instead of using traditional active damping methods that require high-speed data transmission between converters to detect and suppress circulating currents, the patent inverts the approach by using a preconditioning function that proactively sets reference voltages to prevent circulating currents from arising in the first place. This passive prevention method eliminates the need for high transmission speeds.
2Reliability
If traditional control methods are used to prevent circulating currents, then circulating current suppression is improved, but high transmission speeds are required which lead to unstable control
Solution Approach 1:
The patent implements a preconditioning function that calculates and sets appropriate reference voltages for slave converters before circulating currents can develop. By proactively adjusting the reference voltage based on the master converter's output and system conditions, the method prevents circulating currents from arising in the first place, eliminating the need for high-speed reactive control and ensuring stable operation.
3Measurement precision
If data transmission between converters is increased to improve circulating current control, then circulating current detection is improved, but the complexity of the control system increases
Solution Approach 1:
The patent extracts the circulating current prevention function from the data transmission and communication system between converters. Instead of using complex inter-converter data exchange to detect and control circulating currents, the method uses a simplified reference voltage distribution approach where master converters publish their reference voltage and slave converters automatically adjust accordingly, eliminating the need for complex communication protocols.
4Power
If the number of DC-DC converter units is increased to handle higher power loads, then the power handling capacity is improved, but the risk of circulating currents and control instability increases
Solution Approach 1:
The patent segments the multi-converter system into master and slave roles, allowing any number of converters to be added to the parallel configuration without increasing control complexity. Each slave converter independently follows the master's reference voltage, enabling scalable system expansion while maintaining stable control and preventing circulating currents regardless of the total number of converter units.
Data Source
AI summary
A method for operating a DC-DC voltage converter apparatus having a plurality of DC-DC voltage converter units connected in parallel in an electrical network is provided. The DC-DC voltage converter units are operated in a master/slave configuration based on current mode control in order to set a desired output voltage. Here, a reference voltage, to which the output voltage is intended to be adjusted, for the slave converters is determined by way of a preconditioning function according to a predetermined calculation specification from a master reference voltage prescribed by the master converter. Stable control can therefore be ensured even in the case of fluctuating loading at the respective DC-DC voltage converter units.