Power Converter Source-Mode Switching Under DC Bus Power Mismatch
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Solution Overview
Problem
Conventional power converters in new energy power generation and storage systems face challenges in maintaining stability when there is a mismatch between the power of successive stages, leading to potential shutdowns or loss of grid construction capability.
Innovation Solution
The power converter is designed with a DC/AC conversion unit and a direct current bus, allowing it to switch between current source and voltage source modes based on direct current bus voltage thresholds, thereby maintaining stability and grid support.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power converter operates in voltage source mode to provide grid construction capability, then the grid stability is improved, but when the direct current source cannot meet the power demand, the direct current bus voltage becomes unstable and may cause device damage
Solution Approach 1:
The power converter dynamically switches between voltage source mode and current source mode based on the relationship between power demand and direct current source capability. When the direct current source can meet the power demand, the converter operates in voltage source mode to maintain grid stability. When the power demand exceeds the direct current source capability, it switches to current source mode to prevent direct current bus voltage instability, thus adaptively resolving the contradiction between grid stability and voltage stability.
Solution Approach 2:
The invention changes the operating mode parameter of the power converter (from fixed voltage source mode to switchable between voltage source mode and current source mode). By detecting whether the power demand exceeds the direct current source capability, the system changes the converter's operating mode to appropriately balance grid construction capability with protection against voltage instability.
2Object-affected harmful factors
If the power converter shuts down for self-protection when power stages do not match, then device safety is improved, but the grid construction capability is lost and system stability is reduced
Solution Approach 1:
Instead of a fixed shutdown protection strategy, the invention implements a dynamic response where the power converter detects power stage mismatches and adaptively switches between operational states. When a mismatch is detected, it transitions to current source mode to continue operating safely without shutting down, thereby maintaining system stability while ensuring device safety.
Solution Approach 2:
The power converter performs self-diagnosis of the power stage matching status and automatically adjusts its operating mode without external intervention. When it detects that the direct current source cannot meet power demand, it autonomously switches to current source mode to protect itself and maintain system stability, eliminating the need for shutdown while ensuring safety.
3Duration of action of stationary object
If the power converter continuously operates without mode switching when power stages do not match, then system continuity is improved, but the direct current bus voltage becomes unstable and grid construction capability is abandoned
Solution Approach 1:
The invention introduces dynamic mode switching to maintain operation continuity. Instead of continuous operation in a fixed mode, the power converter continuously monitors the power stage matching status and dynamically switches between voltage source mode and current source mode. This ensures continuous operation while preventing direct current bus voltage instability by appropriately adjusting the operating mode according to real-time conditions.
Data Source
AI summary
The embodiments include a power converter including a DC/AC conversion unit. A direct current bus is connected to the DC/AC conversion unit and a direct current source. The DC/AC conversion unit is further connected to a power grid. When a direct current bus voltage is less than or equal to a first voltage threshold, the power converter may switch to a current source mode to output first output power to the power grid, where the first output power is equal to an output power limit of the direct current source. Then, if a fluctuation amplitude of the direct current bus voltage is less than or equal to a first fluctuation threshold, the power converter may resume outputting second output power to the power grid in a voltage source mode, so that the second output power is less than or equal to the output power limit of the direct current source.