Power Converter Phase-Jump Control Using Virtual Resistance
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Solution Overview
Problem
Power converters experience overvoltage and power backfeed due to phase jumps in the power grid, leading to instability and potential breakdown when traditional phase-locked loop control methods fail to synchronize with the grid voltage.
Innovation Solution
A power converter control method that sets fixed d-axis and q-axis current reference values and calculates a total modulation voltage using a virtual resistance parameter to compensate for phase angle differences, ensuring synchronization and reducing power backfeed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional phase-locked loop control methods are used, then the power converter can synchronize with the grid voltage under normal conditions, but the system becomes unstable and experiences overvoltage when phase jumps occur in the power grid
Solution Approach 1:
The control method dynamically switches between different control strategies based on the detected phase angle difference. When the phase angle difference exceeds the threshold, the system transitions from traditional phase-locked loop control to a control mode using fixed d-axis and q-axis current reference values, allowing the system to adapt to changing grid conditions and maintain stability during phase jumps
Solution Approach 2:
The invention changes the control parameters (current reference values) based on the phase angle difference detection. By setting fixed d-axis and q-axis current reference values when phase jumps occur, the system modifies its operating parameters to prevent overvoltage and maintain stable operation under abnormal grid conditions
2Productivity
If the phase-locked loop continuously tracks the grid voltage phase, then normal power transmission is maintained, but power backfeed occurs when phase jumps exceed the tracking capability
Solution Approach 1:
The system performs preliminary detection of the phase angle difference and takes preventive action by switching to fixed current reference values before the phase jump causes severe power backfeed. This anticipatory control prevents the harmful effect rather than reacting after it occurs
Solution Approach 2:
The invention converts the potentially harmful phase jump condition into a manageable situation by using the detected phase angle difference as a trigger to switch control modes. The phase jump information, which would normally cause instability, is transformed into a control signal that activates the protective fixed reference value mode, turning a harmful condition into a beneficial control mechanism
3Loss of time
If the power converter uses generator terminal voltage as power grid voltage for control, then control response time is improved, but measurement precision is reduced due to the large distance between the power grid and the power converter
Solution Approach 1:
The system uses only the necessary portion of voltage information (terminal voltage) for control purposes, accepting the trade-off of reduced precision in exchange for faster response. The fixed current reference value control mode compensates for the measurement imprecision by using a more robust control strategy that is less sensitive to voltage measurement errors
Data Source
AI summary
A power converter control method includes: determining a phase angle difference between a phase angle of a voltage output by the power converter and a phase angle of a power grid voltage; and if the phase angle difference is greater than or equal to a first angle threshold, setting a d-axis current reference value and a q-axis current reference value that are used to determine a modulation voltage of the power converter to preset fixed values; calculating a first modulation voltage of the power converter based on the d-axis current reference value, the q-axis current reference value, and a power grid current; calculating a compensation voltage of the power converter based on a preset virtual resistance parameter and the power grid current; and using a sum of the first modulation voltage and the compensation voltage as a total modulation voltage.