Power Conversion Device Subtraction Correction Control
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Solution Overview
Problem
Conventional power conversion devices face difficulties in suppressing abrupt and abnormal increases in output voltage during disconnection events due to limitations in feed-forward control design, which restricts their ability to respond effectively to sudden voltage changes.
Innovation Solution
A power conversion device and system that employ a control mechanism with subtraction correction, where the control signal is adjusted based on a corrected voltage command value only when the output voltage exceeds a threshold, allowing for more aggressive correction during abnormal conditions without interfering with normal operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional feed-forward control is used with normal filter response settings, then the control system avoids sensitive response to noise, but the system cannot cope with abrupt and abnormal level of increase in output voltage
Solution Approach 1:
The patent applies dynamics by making the filter response characteristics adjustable based on operating conditions. The control device switches between normal filter settings during stable operation and abnormal filter settings during voltage fluctuations, allowing the system to adapt its response characteristics dynamically. This resolves the contradiction by enabling fast response to abnormal voltage changes while maintaining noise filtering during normal operation.
Solution Approach 2:
The patent changes the filter parameters (response characteristics) based on the detected voltage conditions. When abnormal voltage increase is detected, the filter response is adjusted to be more sensitive and faster. This parameter change allows the system to overcome the limitation of fixed filter settings and respond appropriately to both normal and abnormal conditions.
2Reliability
If protection function is activated to eliminate abnormal voltage increase, then the abnormal voltage can be eliminated, but the occurrence of abnormal voltage cannot be suppressed in the period until protection function is activated
Solution Approach 1:
The patent implements preliminary action by detecting abnormal voltage trends before they reach dangerous levels and taking corrective control actions proactively. The control device monitors output voltage continuously and applies feed-forward control adjustments in advance, suppressing abnormal voltage increases before they become severe enough to trigger protection functions. This eliminates the time delay between abnormal voltage occurrence and protection activation.
Solution Approach 2:
The patent uses feedback control mechanisms where the control device continuously monitors the output voltage and adjusts control signals based on detected deviations. This closed-loop feedback allows the system to respond to and suppress abnormal voltage increases in real-time, preventing them from escalating to levels that would require protection function intervention.
3Speed
If feed-forward control uses larger gain to respond faster to voltage changes, then response speed improves, but the control system becomes sensitive to noise and disturbance
Solution Approach 1:
The patent makes the control gain dynamic rather than fixed. The gain is adjusted based on the operating condition: higher gain is applied when abnormal voltage changes are detected to enable fast response, while lower gain is used during normal operation to maintain stability and noise immunity. This dynamic gain adjustment resolves the contradiction between response speed and noise sensitivity.
Solution Approach 2:
The patent changes control parameters (gain values) based on detected voltage conditions. When abnormal voltage increase is detected, the control device switches to parameter settings that enable faster response with higher gain. During normal operation, parameters are set to prioritize stability and noise filtering. This conditional parameter change allows the system to optimize performance for each operating regime.
Data Source
AI summary
A power conversion device includes: a power conversion circuit for converting DC power into AC power; and a controller to generate a control signal for the power conversion circuit based on a control command value and an output voltage of the power conversion circuit. The controller is configured to generate the control signal based on a corrected voltage command value calculated by subtraction correction to decrease a voltage command value when the output voltage of the power conversion circuit is equal to or higher than a predetermined threshold value, and to generate the control signal based on a voltage command value not subjected to the subtraction correction when the output voltage of the power conversion circuit is lower than the threshold value.