Power Conversion Switching for Seamless Grid-Disconnected Transition
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Solution Overview
Problem
Conventional power conversion systems experience instability in power supply when switching from grid-connected to grid-disconnected due to varying voltage amplitude and frequency with load, leading to unreliable power distribution.
Innovation Solution
A method and system that involve determining power grid abnormalities, switching from current source to voltage source mode, and controlling output parameters to smoothly transition from abnormal to rated values, ensuring seamless switching and stable power supply by using a power grid abnormality determining module, abnormal value recording module, switching module, and output control module within the power conversion system.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If droop control is used for switching between grid-connected and grid-disconnected modes, then the switching operation is simple, but the voltage amplitude and frequency vary with load resulting in power supply instability
Solution Approach 1:
The patent changes the control parameters from droop control to active/reactive power control. By controlling the active power output to match load demand and reactive power output to maintain voltage, the system eliminates the coupling between voltage and load that causes instability in droop control, while maintaining operational simplicity through automated control
2Reliability
If voltage source mode is used for grid-disconnected operation, then power supply stability is improved, but the switching complexity increases
Solution Approach 1:
The patent implements dynamic mode switching capability that allows the power conversion system to transition between current source mode (grid-connected) and voltage source mode (grid-disconnected). The system dynamically adjusts its control strategy based on grid status, maintaining stability in both modes while managing complexity through adaptive control architecture
Solution Approach 2:
The patent employs feedback control mechanisms where the controller continuously monitors grid status, voltage, and power parameters. Based on this feedback, the system automatically determines when to switch modes and adjusts control parameters accordingly, reducing the perceived complexity through intelligent decision-making algorithms
Data Source
AI summary
A method and a system for switching from grid-connected to grid-disconnected, and a power conversion system are provided. The method includes determining whether a power grid is abnormal based on a power grid parameter obtained when a PCS is grid-connected and operates in a current source mode, turning off a switching cabinet if the power grid is abnormal, switching from a current source mode to a voltage source mode, sending a command to instruct a grid-connected/grid-disconnected switch to switch from a grid-connected loop to a grid-disconnected loop, controlling an output parameter to smoothly transit from an abnormal parameter value recorded when the power grid is abnormal to a rated parameter value, and supplying power to a load according to the rated parameter value. In this way, seamless switching from grid-connected to grid-disconnected can be achieved, thereby ensuring stability of power supply.