Converter Control for Smooth On/Off-Grid Voltage Switching
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Solution Overview
Problem
The rapid switching between on-grid and off-grid modes in power conversion systems (PCS) leads to significant voltage and current fluctuations, potentially causing severe instability and prolonged dynamic regulation times.
Innovation Solution
An on/off-grid switching control method for converter apparatuses that stabilizes the output voltage by using the current and voltage feedback loops to smoothly transition between control modes, ensuring the difference in output voltage remains within a specified threshold during mode switching.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the PCS performs control switching between on-grid and off-grid modes, then the operating mode adapts to grid conditions, but the output voltage and current fluctuate significantly causing system instability
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between duty cycle and output voltage/current in lookup tables before switching occurs. When mode switching is required, the system directly retrieves pre-computed switching parameters instead of calculating in real-time, allowing the control parameters to be prepared in advance and applied immediately, thus preventing voltage and current fluctuations during the transition between on-grid and off-grid modes
Solution Approach 2:
The patent introduces switching parameter lookup tables as an intermediary between the control mode switch and the power conversion process. These tables store pre-computed duty cycle values that serve as intermediate parameters, mediating the transition by providing smooth, pre-determined control signals that prevent direct abrupt changes in output voltage and current during mode switching
2Speed
If the PCS switches control modes rapidly, then the response time to grid changes improves, but the dynamic regulation time becomes excessively long
Solution Approach 1:
The patent applies preliminary action by pre-calculating optimal duty cycle values for different operating conditions and storing them in lookup tables. When mode switching occurs, the system immediately retrieves the pre-computed switching parameters corresponding to the target mode, enabling rapid mode transition without requiring lengthy real-time calculations, thus reducing dynamic regulation time while maintaining fast response capability
Solution Approach 2:
The patent applies skipping by directly jumping to pre-determined switching parameters from lookup tables based on the target operating mode, rather than gradually adjusting parameters during transition. This allows the system to rush through the switching process by applying the correct duty cycle values immediately, significantly reducing the time required for dynamic regulation during mode changes
3Adaptability or versatility
If the PCS switches between control loops and commands, then the control flexibility improves, but severe voltage distortion occurs
Solution Approach 1:
The patent introduces switching parameter lookup tables as an intermediary that stores pre-computed duty cycle values for different operating modes. During mode switching, the system retrieves appropriate parameters from these tables, which act as a buffer that smooths the transition between different control loops and commands, preventing severe voltage distortion while maintaining control flexibility
Solution Approach 2:
The patent applies parameter changes by switching between different sets of pre-determined duty cycle parameters stored in lookup tables, corresponding to different operating modes (on-grid vs. off-grid). This allows the system to change control parameters discretely and predictably, maintaining voltage quality while achieving the necessary control flexibility for different grid conditions
Data Source
AI summary
The field of power systems includes a switching control method for a converter apparatus in a power supply system and the apparatus. This solution may be applied to a power conversion system in scenarios such as a new energy microgrid or an electrochemical energy storage station. In the method, a voltage of the converter apparatus at a control switching moment is stored, the voltage is used as an initial value after switching is performed, and the voltage is transited to a rated voltage in a first time period.