Power Converter Mode Switching for DC Bus Voltage Stability
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Solution Overview
Problem
Conventional power converters in new energy power generation and storage systems face challenges in maintaining stability when the power of one stage does not match the power of the previous or next stage, leading to potential device damage and instability in the entire system.
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 the direct current bus voltage and fluctuation thresholds, thereby maintaining stability and preventing device damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power converter operates in voltage source mode to provide grid construction capability, then the power grid stability is improved, but when the required power exceeds the direct current source capability, the direct current bus voltage becomes unstable and device damage may occur
Solution Approach 1:
The power converter dynamically switches between voltage source mode and current source mode based on the real-time relationship between required power and direct current source output capability. This dynamic mode transition allows the system to adapt to changing power demands while preventing direct current bus voltage instability, thereby resolving the contradiction between providing grid construction capability and ensuring system safety.
2Stability of the object's composition
If the power converter limits output power to match the direct current source capability, then the direct current bus voltage stability is improved, but the grid construction capability is abandoned
Solution Approach 1:
The system dynamically adjusts its operating mode based on power demand conditions. When required power exceeds direct current source capability, it operates in current source mode to maintain voltage stability. When conditions permit, it switches to voltage source mode to provide grid construction capability. This dynamic adaptation resolves the contradiction between voltage stability and grid construction capability.
3Device complexity
If the power converter continuously operates without mode switching, then the system simplicity is maintained, but the system cannot cope with power mismatch and stability is reduced
Solution Approach 1:
The power converter incorporates dynamic mode switching control that transitions between voltage source mode and current source mode based on real-time power balance conditions. This dynamic control mechanism enables the system to cope with power mismatches between stages while maintaining reasonable control complexity, thereby improving system operation stability without excessive complexity.
Data Source
Figure 1(a)~1(c)
Figure 1(d)~1(e)
Figure 2
AI summary
This application provides a power converter, an energy storage power supply system, and a power output method of the power converter. The power converter includes 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. The power converter has a capability of coping with power fluctuation of the power grid, and can effectively support stability of the power grid.