Modular Multi-Level Converter Control Architecture
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Solution Overview
Problem
Current modular multi-level converters face challenges in efficiently controlling and determining the switching sequence of multiple sub-modules, which affects the quality and form of output AC power in high voltage direct current (HVDC) transmission systems.
Innovation Solution
A modular multi-level converter architecture that includes a central control unit and sub-control units, where each sub-control unit acquires and transmits state information, including switching history and voltage data, to the central control unit, allowing for efficient determination of switching operations and sequence optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a modular multi-level converter uses a plurality of sub-modules for power conversion, then the converter can achieve high voltage direct current transmission capability, but the control complexity of managing multiple sub-modules increases significantly
Solution Approach 1:
The converter is divided into multiple independent sub-modules, each capable of autonomous operation with its own control unit. This segmentation allows the system to achieve high power capability while managing control complexity through modular independence, where each sub-module can be controlled separately rather than as a monolithic system.
Solution Approach 2:
A communication network is introduced as an intermediary between control units to facilitate coordinated control of multiple sub-modules. This mediator enables information exchange and synchronization without requiring direct complex interconnections between all control units, thus managing system complexity while maintaining HVDC transmission capability.
2Manufacturing precision
If the converter controls multiple sub-modules with detailed state information, then the output AC power quality improves, but the amount of data processing and communication required increases
Solution Approach 1:
Detailed state information is extracted and communicated only when necessary for control decisions, rather than continuously transmitting all possible data. This selective extraction maintains output power quality by providing essential information while reducing the overall data processing burden on the control system.
Solution Approach 2:
The control system processes only the necessary portion of state information required for maintaining AC power quality, rather than analyzing all available data. This partial action approach ensures quality control while avoiding the excessive data processing burden that would result from comprehensive analysis of all sub-module states.
3Device complexity
If the converter uses centralized control for all sub-modules, then coordination is simplified, but the control system becomes a single point of failure and less reliable
Solution Approach 1:
Control functionality is segmented and distributed across multiple independent control units, each managing specific sub-modules. This segmentation eliminates the single point of failure inherent in centralized control, as the failure of one control unit does not compromise the entire system, while maintaining coordination through the communication network.
Solution Approach 2:
A feedback mechanism is implemented where control units exchange state information and control decisions through the communication network. This feedback loop enables coordinated control similar to centralized systems while distributing control functions across multiple units, thereby improving reliability through redundancy and fault isolation.
4Manufacturing precision
If the converter determines switching sequences based on comprehensive state information, then switching precision improves, but the computation time and control complexity increase
Solution Approach 1:
Switching sequences are determined in advance based on predicted state information and control objectives, rather than calculating optimal sequences in real-time based on current states. This preliminary action approach maintains switching precision by considering future states while reducing computation time by avoiding complex real-time optimization calculations.
Solution Approach 2:
The control system determines switching sequences using a subset of critical state information rather than analyzing all available data. This partial information approach maintains sufficient switching precision for effective power conversion while significantly reducing the computation time and control complexity that would result from comprehensive state analysis.
Data Source
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AI summary
Provided is a modular multi-level converter including a plurality of sub-modules including switching elements, a plurality of sub-control units respectively controlling the plurality of switching elements included in the plurality of sub-modules, and a central control unit which determines switching operation conditions of the plurality of sub-modules, and transmits control signals corresponding to the determined switching operation conditions to the plurality of sub-control units. Each of the plurality of sub-control units acquires state information on the sub-module controlled thereby and transmits the acquired state information to the central control unit.