Modular Multilevel Converter Carrier Shaping for Charge Balancing
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Solution Overview
Problem
Modular multi-level converters face challenges in charge balancing between modules due to different internal resistances and varying load conditions, leading to uneven discharge and voltage inconsistencies.
Innovation Solution
A method for controlling modular multi-level converters using phase-shifted pulse width modulation, allowing for active charge balancing by modifying carrier signals through vertical shifts, curvatures, and superposition, while accounting for parasitic impedances and load variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If conventional phase-shifted carrier modulation is used, then uniform distribution of discharging or charging over all modules is achieved, but charge balancing between modules with different internal resistances cannot be corrected
Solution Approach 1:
The patent applies local quality by introducing module-specific vertical shifts to carrier signals based on individual module characteristics (internal resistance, state of charge). Each module receives a customized carrier signal adjustment rather than a uniform modulation approach, allowing targeted charge balancing for modules with different internal resistances while maintaining overall system stability.
2Manufacturing precision
If modular multi-level converters are used to enable voltage output in very fine steps, then conversion precision is improved, but complexity of control increases
Solution Approach 1:
The patent changes carrier signal parameters (vertical position, curvature, phase) to achieve precise voltage control. By modifying the carrier signal characteristics rather than increasing the number of modules or switches, the system maintains fine voltage step resolution while avoiding proportional increases in control complexity.
3Reliability
If carrier signals are modified with vertical shifts and curvatures for active charge balancing, then charge balancing capability is improved, but signal processing complexity increases
Solution Approach 1:
The patent implements preliminary action by pre-calculating the required vertical shifts and curvature adjustments for each module's carrier signal based on their internal resistance and state of charge. These adjustments are prepared in advance and applied systematically, reducing the real-time computational burden while maintaining effective charge balancing capability.
Data Source
AI summary
A method for controlling a modular multi-level converter including a multiplicity of modules having at least one energy storage unit and a plurality of controllable switches. The modular multi-level converter is controlled by pulse-width-modulated control signals. A respective control signal is generated on the basis of a respective carrier signal having a phase shift relative to the respective module, and on the basis of at least one reference signal. As a result of a comparison, based on a size comparison, of a signal profile of the respective carrier signal with the at least one reference signal, a connection time of the at least one energy storage unit of the respective module to a load current is triggered. The signal profile of the respective carrier signal is modified by at least one change within three degrees of freedom.