Parallel Power Converter Disconnection Detection
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Solution Overview
Problem
In power conversion systems with two devices connected in parallel, detecting abnormal disconnection on the output side of each device is challenging due to the difficulty in distinguishing between normal and abnormal voltage values, and increasing resistance values to enhance detection leads to energy loss and heat generation issues.
Innovation Solution
A power conversion system with an equalization control unit that corrects voltage command values using an output correction voltage to equalize output currents and an abnormal disconnection determination unit that identifies the source of disconnection based on changes in the output correction voltage, correlating with resistance value differences between the devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If resistance values are increased to enhance abnormal disconnection detection, then detection accuracy is improved, but energy loss and heat generation increase
Solution Approach 1:
The patent introduces an intermediary parameter (output correction voltage) to detect abnormal disconnections. Instead of directly measuring resistance changes which would require increasing resistance values, the system uses the output correction voltage generated during equalization control as an indirect indicator. When abnormal disconnection occurs, the output correction voltage changes in a detectable manner, allowing accurate detection without increasing actual resistance values and avoiding associated energy losses.
2Measurement precision
If resistance values are increased to enhance abnormal disconnection detection, then detection accuracy is improved, but heat generation increases
Solution Approach 1:
The patent uses output correction voltage as an intermediary measurement parameter to detect abnormal disconnections. By monitoring changes in the output correction voltage during equalization control, the system can identify abnormal disconnections without needing to increase resistance values. This approach prevents the heat generation that would result from increased resistance values while maintaining high detection accuracy.
3Stability of the object's composition
If equalization control is performed to equalize output currents, then current balancing is improved, but the complexity of determining abnormal disconnection increases
Solution Approach 1:
The patent employs feedback through the equalization control mechanism to simplify abnormal disconnection determination. During equalization control, the system continuously adjusts output correction voltages to balance output currents between parallel power conversion devices. The abnormal disconnection determination unit monitors the output correction voltage generated by this feedback process - when abnormal disconnection occurs, the feedback mechanism produces characteristic changes in the output correction voltage that clearly indicate the faulty device, thereby simplifying the determination process despite the complexity of the equalization control itself.
Data Source
AI summary
A control device is applied to a power conversion system including a first DDC and a second DDC connected in parallel with a common power supply target. The control device performs the equalization control of correcting, with an output correction voltage, at least any of a voltage command value of the first DDC and a voltage command value of the second DDC to equalize an output current. Moreover, while the equalization control is being performed, it is determined on which one of an output side of the first DDC or an output side of the second DDC abnormal disconnection has been caused based on the output correction voltage.