Parallel DC/DC Converter Load Sharing via Series Compensation Voltage
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Solution Overview
Problem
Existing electrical DC/DC converters, when operated in open-loop with fixed modulation parameters, experience unequal current distribution among paralleled converters, leading to potential overloading and reduced output power due to variations in electric and thermal losses.
Innovation Solution
A method and controller for a converter arrangement that includes auxiliary converters in series with primary converters, adjusting compensation voltages to balance current distribution by determining and applying compensation signals based on current differences, ensuring equal loading and preventing overloading.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If several electrical converters are operated in open-loop with fixed modulation parameters, then the converter operation is simplified, but the current distribution becomes unequal and some converters may be overloaded
Solution Approach 1:
The patent introduces auxiliary converters as intermediary devices connected in series with each primary converter. These auxiliary converters generate compensation voltages that act as mediators to balance the current distribution among parallel converters, allowing the system to maintain simple open-loop operation while achieving reliable current balancing
Solution Approach 2:
The patent changes the voltage parameter by introducing compensation voltages from auxiliary converters. By dynamically adjusting these compensation voltages based on current differences, the system modifies the effective voltage across each primary converter to achieve equal current distribution without changing the primary converters' operating parameters
2Power
If several electrical converters are parallel connected to increase output power, then the available output current increases, but the current distribution becomes unequal due to variations in losses and parasitic elements
Solution Approach 1:
Auxiliary converters serve as intermediary devices that compensate for manufacturing variations and parameter deviations in primary converters. By introducing adjustable compensation voltages, they mask the effects of unequal losses and parasitic elements, enabling uniform current distribution across all parallel converters
Solution Approach 2:
The system implements feedback by monitoring current values from each primary converter and using these measurements to determine appropriate compensation voltages. The controller continuously adjusts the compensation voltages based on the detected current differences, creating a closed-loop control mechanism that maintains equal current distribution
3Reliability
If compensation voltages are applied to balance current distribution, then equal loading is achieved, but additional auxiliary converters are required
Solution Approach 1:
The patent segments the voltage generation function by separating it into two parts: the primary converters generate the main output power, while the auxiliary converters generate only the small compensation voltages needed for current balancing. This segmentation allows the system to maintain simple primary converters while adding only small, low-power auxiliary converters for control purposes
Data Source
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AI summary
A method for operating a converter arrangement (20) is described. The converter arrangement (20) is configured for converting a first DC bus voltage into a second DC bus voltage and comprises a first electrical converter (22) and a second electrical converter (24) being electrically arranged in parallel to the first electrical converter (22), and each being configured for converting a first DC voltage (V1) into a second DC voltage (V2), and a first auxiliary converter (30) electrically arranged in series with the first electrical converter (22) and a second auxiliary converter (32) electrically arranged in series with the second electrical converter (24). The method comprises: receiving a first current value (I1) being representative of a first current through the first electrical converter (22); receiving a second current value (I2) being representative of a second current through the second electrical converter (24); determining a first difference between the first and second current values (I1, I2); determining a first compensation voltage value (VC1) depending on the first difference such that the first current corresponds to the second current when a first compensation voltage corresponding to the first compensation voltage value (VC1) is added by the first auxiliary converter (30) to the first DC bus voltage applied to the first electrical converter (22) or when the first compensation voltage is added to a first output voltage generated by the first electrical converter (22); determining a second compensation voltage value (VC2) depending on the first difference such that the first current corresponds to the second current when a second compensation voltage corresponding to the second compensation voltage value (VC2) is added by the second auxiliary converter (32) to the first DC bus voltage applied to the second electrical converter (24) or when the first compensation voltage is added to a second output voltage generated by the second electrical converter (24); sending a first compensation signal to the first auxiliary converter (30), wherein the first auxiliary converter (30) is configured to add the first compensation voltage to the first DC bus voltage applied to the first electrical converter (22) or, respectively, to the first output voltage generated by the first electrical converter (22) upon receiving the first compensation signal; and sending a second compensation signal to the second auxiliary converter (32), wherein the second auxiliary converter (32) is configured to add the second compensation voltage to the first DC bus voltage applied to the second electrical converter (24) or, respectively, to the second output voltage generated by the second electrical converter (24) upon receiving the second compensation signal.