Grid-Connected Inverter Overcurrent Control via D-Q Axis Voltage Variation
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Solution Overview
Problem
Grid-connected inverters experience overcurrent trips due to rapid variations in grid voltage, which existing technologies fail to adequately prevent.
Innovation Solution
An apparatus and method that includes a grid voltage sensor, voltage variation calculator, and output current controller to detect rapid grid voltage variations, reducing the output current before it exceeds safe thresholds, thereby preventing overcurrent trips. This involves calculating D-axis and Q-axis voltage variations and controlling the inverter to maintain output current within predetermined limits.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the grid-connected inverter operates in synchronization with the output current reference value, then the power generation efficiency is improved, but when an abnormal grid voltage occurs, the output current varies rapidly causing overcurrent trips
Solution Approach 1:
The control apparatus performs preliminary detection of grid voltage abnormalities and proactively adjusts the output current reference value before overcurrent occurs. By detecting voltage deviations and predicting current variations in advance, the system pre-modifies the current reference to prevent overcurrent trips, thus maintaining both high productivity and reliability.
Solution Approach 2:
The control apparatus continuously monitors grid voltage and uses this feedback to dynamically adjust the output current reference value. When voltage abnormalities are detected, the feedback mechanism triggers real-time modification of the current reference, creating a closed-loop control system that prevents overcurrent while maintaining efficient power generation.
2Speed
If the output current is rapidly adjusted to respond to grid voltage changes, then the response speed is improved, but the overcurrent protection capability deteriorates
Solution Approach 1:
Instead of reacting after overcurrent occurs, the system performs preliminary detection of voltage abnormalities and pre-adjusts the current reference value. This anticipatory approach maintains fast response to grid changes while preventing the harmful overcurrent effect from occurring in the first place.
Solution Approach 2:
The control apparatus introduces an intermediary calculation process that computes the output current reference value based on grid voltage conditions. This intermediary step acts as a buffer between rapid voltage changes and the actual current output, allowing fast response while filtering out harmful overcurrent variations through calculated reference adjustment.
3Device complexity
If the inverter maintains constant output current reference value, then the control simplicity is improved, but the ability to prevent overcurrent during voltage abnormalities deteriorates
Solution Approach 1:
The control apparatus dynamically changes the current reference value parameter based on detected grid voltage conditions. By modifying this key parameter in response to voltage abnormalities, the system achieves effective overcurrent protection without requiring complex hardware modifications, maintaining relatively simple device architecture while improving reliability.
Data Source
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AI summary
An apparatus for controlling overcurrent of a grid-connected inverter due to an abnormal grid voltage includes: a grid voltage sensor configured to sense a grid voltage according to an output current of the grid-connected inverter; a voltage variation calculator configured to calculate a D-axis voltage and a Q-axis voltage of the grid voltage to obtain variation values of the D-axis voltage and the Q-axis voltage; and an output current controller configured to determine whether at least one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds a set value of the grid voltage variation, and decrease the output current by a predetermined value when one of the D-axis voltage variation value and the Q-axis voltage variation value exceeds the set value of the grid voltage variation.