Multilevel Converter Mid-Point Voltage Balancing
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Solution Overview
Problem
Multi-level power converting apparatuses face challenges in balancing voltages at the capacitive mid-point due to imbalances caused by excess current, which existing solutions either require additional elements like resistors or rely on complex control modulation.
Innovation Solution
A power converting apparatus with capacitors in series and an electronic converter that uses a controller to modify the current at the mid-point by displacing voltage wave edges based on the direction and value of the output current, effectively balancing the voltage by adjusting the modulation to compensate for imbalances between capacitors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If additional elements like resistors are used to balance voltage at the mid-point, then voltage balancing is achieved, but device complexity and energy loss increase
Solution Approach 1:
The system uses its own output current information to automatically balance the mid-point voltage through controller adjustment of voltage wave edges, eliminating the need for external balancing elements like resistors. The converter balances itself by utilizing existing components and control capabilities.
Solution Approach 2:
The controller dynamically adjusts the edges of voltage waves by varying modulation parameters based on detected output current characteristics and mid-point voltage imbalance, achieving voltage balancing through parameter optimization rather than additional hardware.
2Reliability
If additional elements like resistors are used to balance voltage at the mid-point, then voltage balancing is achieved, but energy loss increases
Solution Approach 1:
The system uses its own output current information to automatically balance the mid-point voltage through controller adjustment of voltage wave edges, eliminating the need for external balancing elements like resistors. The converter balances itself by utilizing existing components and control capabilities.
Solution Approach 2:
The controller dynamically adjusts the edges of voltage waves by varying modulation parameters based on detected output current characteristics and mid-point voltage imbalance, achieving voltage balancing through parameter optimization rather than additional hardware.
3Device complexity
If complex control modulation is used to balance voltage without additional elements, then device complexity is reduced, but control complexity increases
Solution Approach 1:
The system uses its own output current information to automatically balance the mid-point voltage through controller adjustment of voltage wave edges, eliminating the need for external balancing elements like resistors. The converter balances itself by utilizing existing components and control capabilities.
Solution Approach 2:
The controller continuously monitors the mid-point voltage imbalance and output current characteristics, then adjusts the voltage wave edges accordingly to maintain voltage balancing. This closed-loop feedback control achieves automatic adaptation without requiring complex external balancing circuits.
Data Source
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AI summary
Power converting apparatus that comprises a plurality of capacitors (C1, C2) disposed in series on the direct-voltage side, and an electronic power converter (1) for converting the direct voltage supplied by the capacitors (C1, C2) into at least one alternating-voltage signal by means of a determined modulation, the alternating-voltage signal comprising at least one phase represented by a voltage wave that comprises a plurality of voltage levels dependent on the number of capacitors (C1, C2) on the direct-voltage side, switching from one level to another by means of a sidewall (2) dependent on the modulation. The apparatus comprises a controller for modifying the current (im) at a connection mid-point (O) between every two capacitors (C1, C2) in accordance with the direction of the slope and the value of at least one output current of the apparatus.