Chain-Link Converter Switching Layout for Common-Mode Current Suppression
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Solution Overview
Problem
The chain-link energy storage system faces challenges due to large common-mode currents caused by distributed capacitance between batteries and ground, leading to EMI, increased system loss, and potential damage to core insulation.
Innovation Solution
A chain-link converter is designed with a series connection of switch submodules, where the switching time of at least one submodule is extended or the frequencies are lowered, and high-frequency and low-frequency submodules are strategically placed to reduce common-mode currents.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If batteries of large volume are used in the chain-link energy storage system, then energy storage capacity is improved, but distributed capacitance to ground increases causing large common-mode current
Solution Approach 1:
The patent changes the switching time parameter of submodules to reduce common-mode current. Specifically, at least one submodule is designed with a switching time greater than twice the switching time of other submodules, which modifies the voltage change rate and reduces the common-mode current generated by the distributed capacitance of large-volume batteries.
2Object-generated harmful factors
If common-mode current is reduced by extending switching time, then EMI and system loss are reduced, but switching frequency is lowered
Solution Approach 1:
The patent applies local quality by making different submodules have different switching times. At least one submodule has a switching time greater than twice that of other submodules, creating local variation in switching characteristics that reduces common-mode current while maintaining overall system functionality.
Solution Approach 2:
The patent introduces asymmetry in the switching times of submodules. Instead of all submodules switching at the same frequency, at least one submodule operates at a lower switching frequency (greater than twice the switching time), creating an asymmetric switching pattern that cancels out common-mode current components.
3Quantity of substance
If common-mode current flows through distributed capacitance, then energy storage capacity is maintained, but core insulation is damaged
Solution Approach 1:
The patent changes the switching time parameter to reduce common-mode current, thereby protecting core insulation while maintaining energy storage capacity. By extending the switching time of at least one submodule to be greater than twice that of other submodules, the voltage change rate is reduced, which limits the common-mode current flowing through the distributed capacitance and prevents insulation damage.
Data Source
AI summary
The disclosure provides a chain-link converter, comprising: a first node; a second node; and a plurality of switch submodules, wherein the plurality of switch submodules are connected in series, and the plurality of switch submodules are electrically connected between the first node and the second node, and a switching time of at least one switch submodule is greater than the switching time of other switch submodules. The chain-link converter of the disclosure effectively suppresses the common-mode current by extending the switching time of at least one switch submodule.