Series-Parallel DC Conversion System Voltage Balance Control
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Solution Overview
Problem
In DC/DC combined conversion systems with a high-voltage side in series and a low-voltage side in parallel, voltage and current imbalances occur due to differences in DC/DC units and loads, affecting the selection of power switches, thermal design, and overall system performance and reliability.
Innovation Solution
A DC conversion system with an upper and lower power module group, where the input terminals of the upper power module group are connected in series and the output terminals in parallel, and vice versa, coupled with a controller that samples input voltages and output currents to generate modulation signals for power switch control, ensuring voltage and current equalization across the system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single power supply is used, then the system structure is simple, but it cannot meet high voltage and high power application requirements due to voltage and current stress limitations
Solution Approach 1:
The power supply system is divided into multiple DC/DC converter units, each handling a portion of the total power. These units are connected in series on the high-voltage side to distribute voltage stress and in parallel on the low-voltage side to distribute current, enabling the system to meet high voltage and high power requirements while maintaining manageable stress levels on individual components
Solution Approach 2:
Multiple DC/DC converter units are nested within a combined conversion system architecture, where each unit operates independently but contributes to the overall system output. The series-parallel connection structure allows individual converter modules to be integrated into a larger system that achieves higher voltage and power capabilities
2Stress or pressure
If multiple DC/DC units are connected in series-parallel configuration, then voltage stress and current stress of each unit are reduced, but voltage imbalance on series side and current imbalance on parallel side occur
Solution Approach 1:
The control system continuously monitors the input voltage of each DC/DC converter unit and uses this feedback information to adjust the duty cycle of each unit's power switches. This closed-loop control ensures that voltage imbalance on the series side and current imbalance on the parallel side are actively compensated, maintaining stable operation of the combined conversion system
Solution Approach 2:
The duty cycle of each DC/DC converter unit is dynamically adjusted based on real-time voltage measurements. When voltage imbalance is detected, the control system modifies the switching duty cycles of individual units to equalize voltages on the series side and currents on the parallel side, making the system adaptable to changing operating conditions
3Ease of operation
If voltage and current imbalance occurs, then the system can still operate, but power switch selection, thermal design, and system reliability are adversely affected
Solution Approach 1:
By implementing real-time monitoring of input voltages and using feedback control to adjust duty cycles, the system maintains voltage and current balance across all DC/DC converter units. This prevents excessive stress on individual power switches, ensures proper thermal design margins are maintained, and improves overall system reliability by avoiding operation under imbalanced conditions
Data Source
AI summary
The present disclosure provides a DC conversion system and a control method thereof. The DC conversion system comprises: an upper power module group, a lower power module group, input terminals of the upper and lower power module group are connected in series, and output terminals of the upper and lower power module groups are connected in parallel; the controller configured to receive an input voltage of respective input terminal of each of the first and second power modules, a first output current of the output terminal of the upper power module group, a second output current of the output terminal of the lower power module group, and a total output signal of the output terminal of the DC conversion system, and generate a modulation signal according to them to control a power switch of the corresponding power module.