Distributed Inverter Mode Switching for Grid Voltage Jumps
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Solution Overview
Problem
Inverters in distributed power systems face issues with high output voltages when disconnected from the grid, leading to potential damage to local loads due to frequent shutdowns during high voltage ride through events, disrupting continuous power supply.
Innovation Solution
The inverter switches from a current source mode to a voltage source mode when rapid voltage changes exceed a threshold, maintaining stable power output and performing islanding detection to prevent shutdowns during high voltage events.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the inverter triggers protection and shuts down when voltage exceeds threshold, then the local load is protected from high voltage damage, but power supply to the local load is interrupted
Solution Approach 1:
The inverter dynamically switches between grid-connected mode and independent mode based on real-time voltage detection. When grid voltage is normal, the inverter operates in grid-connected mode; when voltage exceeds threshold, it transitions to independent mode to supply power to local loads, thereby maintaining continuous power supply while protecting loads from high voltage damage
Solution Approach 2:
The control system changes operational parameters by detecting voltage levels and adjusting the inverter's working mode accordingly. When voltage exceeds the preset threshold, the system changes from grid-connected operation to independent operation, enabling continuous power supply to local loads during grid abnormalities
2Productivity
If the inverter operates in grid-connected mode as a current source, then power can be supplied to the grid, but the inverter cannot control output voltage when grid connection is lost
Solution Approach 1:
The inverter dynamically adjusts its operational mode based on grid connection status. In grid-connected mode, it operates as a current source to supply power to the grid. When grid connection is lost or voltage is abnormal, it transitions to independent mode where it becomes a voltage source to control output voltage and supply power to local loads, thereby maintaining both power supply capability and voltage control
3Reliability
If the inverter switches to voltage source mode when voltage jumps are detected, then output voltage can be controlled within safety range, but the inverter may shut down unnecessarily during high voltage ride through events
Solution Approach 1:
The system performs preliminary voltage detection and rate-of-change analysis before triggering mode switching. By detecting both the absolute voltage level and the rate of change (dv/dt), the system can distinguish between genuine abnormalities requiring intervention and transient high voltage ride through events, thereby avoiding unnecessary shutdowns while maintaining voltage control
Solution Approach 2:
The control system continuously monitors output voltage and feeds this information back to the control unit. The control unit analyzes both the voltage magnitude and its rate of change, enabling intelligent decision-making about when to switch modes. This feedback mechanism allows the system to maintain voltage control while avoiding unnecessary shutdowns during transient events
Data Source
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AI summary
Embodiments of this application relate to the field of control technologies, and provide a control method and a distributed power system. The distributed power system includes a plurality of distributed power supply units, and all the plurality of distributed power supply units are connected to an alternating current grid. The method includes: controlling an inverter to work in a current source mode, where the current source mode means that the inverter serves as a current source to convert a direct current generated by a power supply device into an alternating current and output the alternating current to the alternating current grid; and controlling the inverter to switch from the current source mode to a voltage source mode when it is detected that a voltage at a first target port jumps. In this way, an output voltage of the inverter may be controlled within a safety range, so that a local load can be protected before a cause of an abnormal voltage is detected, and comparatively, power may be continuously supplied to the local load.