Parallel DC/DC Converter Control for Current Balance
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Solution Overview
Problem
Conventional parallel power supply devices face challenges in independent control of bidirectional-type DC/DC converters, leading to unbalanced output currents and increased losses due to detection errors and differing polarities.
Innovation Solution
A parallel power supply device with bidirectional DC/DC converters, each comprising a transformer, full-bridge switching circuits, reactors, and a control circuit that adjusts phase shift amounts based on a corrected duty cycle to maintain balanced output currents and prevent polarity differences.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If bidirectional-type DC/DC converters are operated in parallel to enable independent control and flexibility, then adaptability and ease of operation are improved, but detection errors cause output current imbalance and increased losses
Solution Approach 1:
The control circuit incorporates feedback mechanisms that detect output current from each DC/DC converter and adjust the duty cycle accordingly. By comparing detected current with reference values and implementing corrective feedback, the system maintains current balance among parallel converters while preserving independent control capability, thereby reducing energy losses.
Solution Approach 2:
The system dynamically adjusts the duty cycle parameter of each DC/DC converter based on real-time current detection and control calculations. By changing this critical operating parameter in response to detected conditions, the system compensates for detection errors and maintains balanced output currents, reducing energy losses while keeping converters independently controllable.
2Device complexity
If conventional current detection and control methods are used, then control simplicity is maintained, but output current balance deteriorates due to detection errors
Solution Approach 1:
The control circuit uses feedback from current detection to continuously monitor and adjust duty cycles. This feedback loop compensates for detection errors by comparing actual current with target values and making real-time corrections, maintaining output current balance without requiring overly complex control architecture.
Solution Approach 2:
The control circuit acts as an intermediary that processes detected current signals, calculates appropriate duty cycle adjustments, and generates control signals for the switching circuits. This intermediary function bridges the gap between simple detection and precise current balancing, managing complexity while improving stability.
3Speed
If duty cycle is not corrected for detection errors, then control responsiveness is improved, but current balance and loss reduction deteriorate
Solution Approach 1:
The control circuit performs preliminary calculation of the duty cycle by detecting current, comparing it with reference values, and pre-calculating the corrected duty cycle before actuation. This preliminary action accounts for detection errors in advance, allowing rapid response while maintaining current balance and reducing reactive current losses.
Solution Approach 2:
The system dynamically changes the duty cycle parameter based on corrected calculations that account for detection errors. By adjusting this parameter in real-time with error compensation built in, the system maintains both fast response speed and current balance, preventing energy losses from uncorrected detection errors.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Enables independent control of DC/DC converters, balances output currents, and reduces losses by correcting duty cycles to account for detection errors, enhancing the flexibility and efficiency of the power supply system.
Implementation Method 1
a transformer (3)
Implementation Method 2
a first switching circuit (5) which is connected between the common load (1) and a first winding (3a) of the transformer (3) and performs power conversion between DC and AC
Implementation Method 3
a first reactor (9) and a second reactor (10) connected to AC input/output lines of the first switching circuit (5) and the second switching circuit (8), respectively
Data Source
AI summary
A parallel power supply device includes a plurality of DC/DC converters connected in parallel, and each DC/DC converter includes: first and second switching circuits with a transformer therebetween; first and second reactors; and a control circuit. The control circuit generates a duty cycle so that a deviation between voltage of a load and target voltage becomes 0. Correction is performed such that, when the magnitude of the duty cycle is smaller than a set value Vth, the magnitude is fixed at 0, and otherwise, the magnitude is decreased by the set value Vth. Then, the phase shift amounts for drive signals for the first and second switching circuits are determined, and the first and second switching circuits are subjected to phase shift control.