Multilevel Converter Voltage Balancing for Switch Thermal Stress
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Solution Overview
Problem
Multilevel converters face uneven thermal stress distribution among switches due to non-ideal component characteristics, leading to varying health states and reduced lifetime, particularly in high-power applications like solar PV inverters and electric vehicle charging stations.
Innovation Solution
A method to redistribute thermal stress by controlling capacitor units to charge above or below a specific voltage level, compensating for unequal power losses among switches, thereby extending the converter's lifespan.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter operates with equal voltage distribution to switches, then the control is simple and reliable, but thermal stress becomes uneven due to non-ideal component characteristics, reducing lifetime
Solution Approach 1:
The control unit continuously monitors the voltage levels across capacitor units and dynamically adjusts switching signals to maintain equal voltage distribution. This feedback mechanism compensates for non-ideal component characteristics and uneven thermal stress, ensuring reliable operation without requiring complex manual calibration or redesign of the converter structure.
Solution Approach 2:
The control unit dynamically changes switching parameters (duty cycles, switching timing) based on real-time voltage measurements to achieve equal voltage distribution across switches. This parameter adjustment compensates for component tolerances and thermal effects, extending converter lifetime without increasing structural complexity.
2Loss of energy
If capacitor units are charged to equal voltage levels, then voltage distribution is simplified, but power losses among switches remain uneven, reducing efficiency
Solution Approach 1:
The control unit dynamically adjusts switching parameters including duty cycles and timing based on real-time voltage measurements across capacitor units. This enables unequal voltage distribution that compensates for different power losses in individual switches, optimizing overall converter efficiency by reducing total switching losses.
Solution Approach 2:
The control strategy applies different voltage distribution levels to different capacitor units based on their specific characteristics and the associated switch power losses. This localized optimization ensures that each switch operates under conditions that minimize its specific losses, improving overall converter efficiency.
Data Source
AI summary
The present disclosure relates to a method for operating a converter. The converter includes a first and second input terminal for receiving a DC voltage, an output terminal for providing an output voltage variable between a first voltage level and a second voltage level, a first and second series connection of two or more switches that are semiconductor switches, and one or more capacitor units. The method includes the following operation: compensating different power losses of the switches by controlling the switches such that one or more of the one or more capacitor units are charged above a respective third voltage level, and/or that one or more of the one or more capacitor units are charged below a respective third voltage level, so that the DC voltage is not equally distributed to the switches.