Five-Level Bidirectional Converter Using Low-Voltage Semiconductors
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Solution Overview
Problem
High voltage energy storage systems require high voltage semiconductor devices, increasing costs due to the limitations of two-level and three-level energy storage converting circuit structures, which cannot generate very high voltages when using low voltage semiconductor devices.
Innovation Solution
A bidirectional energy storage converter with a five-level circuit structure, utilizing low voltage semiconductor devices in its switching circuits, allowing for stable high voltage current transmission without the need for high voltage semiconductor devices, and replacing clamping diodes with parallel-connected switching tubes and diodes to manage junction temperature.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If two-level or three-level energy storage converting circuit structures are used, then the circuit structure is simple, but the generated voltage is limited and cannot achieve very high voltage
Solution Approach 1:
The patent divides the energy storage converting circuit into multiple bridge arms (first bridge arm, second bridge arm, third bridge arm) with separate switching circuits. Each bridge arm operates independently to contribute to the overall voltage output, enabling the system to achieve very high voltage by combining the outputs of multiple segmented circuits rather than relying on a single complex high-voltage structure.
2Power
If high voltage semiconductor devices are used to achieve high voltage output, then the voltage requirement is satisfied, but the cost of the system increases
Solution Approach 1:
The patent employs low voltage semiconductor devices (such as IGBT modules rated at 1700V or 3300V) instead of expensive high voltage semiconductor devices. By using multiple low voltage devices in a multi-bridge arm configuration, the system achieves the required high voltage output while significantly reducing the cost of semiconductor components, which are typically the most expensive parts of the system.
Solution Approach 2:
The patent changes the voltage rating parameter of the semiconductor devices from high voltage to low voltage, and compensates for the voltage deficiency by increasing the number of bridge arms and changing the circuit topology. This parameter substitution allows the use of cheaper low voltage devices while maintaining the high voltage output capability through circuit architecture rather than component specifications.
3Ease of operation
If clamping diodes are used in the switching circuit, then the circuit function is complete, but the junction temperature becomes excessively high at low modulation ratios
Solution Approach 1:
The patent extracts and removes the clamping diodes from the switching circuit. By eliminating these components, the source of excessive junction temperature at low modulation ratios is removed. The circuit functionality previously provided by clamping diodes is achieved through alternative switching arrangements in the multi-bridge arm topology, allowing the system to operate without the thermal problems associated with clamping diodes.
Data Source
AI summary
A bidirectional energy storage converter and an energy storage system are provided. The bidirectional energy storage converter includes at least one bridge arm. Each bridge arm includes a first switching circuit, a second switching circuit and a third switching circuit. A first end of the first switching circuit is connected to a positive electrode of a direct-current busbar and a second end is connected to a neutral point of the direct-current busbar. A first end of the second switching circuit is connected to the neutral point of the direct-current busbar, and a second end is connected to a negative electrode of the direct-current busbar. A first end of the third switching circuit is connected to a third end of the second switching circuit, a second end is connected to a third end of the first switching circuit, and a third end is connected to an alternating-current busbar.