MMC Distributed Current Control with Synchronized Local Controllers
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Solution Overview
Problem
Existing modular multi-level converters (MMCs) face limitations in dynamic response due to centralized current control, which involves significant data exchange and computation demands, leading to control delays and reduced efficiency.
Innovation Solution
Implementing distributed current control through synchronized local controllers that operate independently with time-based synchronization, reducing the need for extensive communication and computation by deriving a desired converter current waveform from individual converter unit outputs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If centralized current control is used in MMCs, then comprehensive control of all submodules can be achieved, but control delays increase and dynamic response deteriorates due to large data exchange and computation demands
Solution Approach 1:
The patent divides the centralized control system into multiple distributed local controllers, each responsible for controlling a specific subset of submodules. This segmentation reduces the data exchange volume and computation burden for each controller, thereby decreasing control delays while maintaining comprehensive control coverage through coordinated operation of all local controllers.
Solution Approach 2:
The patent introduces a hierarchical control structure with both horizontal (distributed local controllers operating in parallel) and vertical (coordination between levels) dimensions. This dimensional transformation allows the system to maintain comprehensive control while reducing time delays through parallel processing at the local level.
2Speed
If distributed current control is implemented, then control dynamics improve and response time decreases, but system complexity increases due to multiple local controllers requiring synchronization
Solution Approach 1:
The patent implements feedback mechanisms where each local controller monitors its own operation and exchanges synchronization information with other local controllers. This feedback system enables automatic coordination and timing alignment, reducing the manual configuration complexity despite having multiple distributed controllers.
Solution Approach 2:
The patent uses parameter-based synchronization where local controllers adjust their operating parameters (such as switching timing and control cycles) based on synchronization signals from a reference controller. This parameter coordination simplifies the management of multiple controllers compared to hardwired synchronization schemes.
Data Source
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AI summary
A power converter is described. The power converter comprises a plurality of series-connected converter units (521, 522, ..., 52n) and a plurality of synchronised local controllers (721, ..., 72q). Each local controller (721, ..., 72q) is associated with at least one converter unit (521, 522, ..., 52n) and are adapted to operate as a single controller for distributed current control of the series-connected converter units (521, 522, ..., 52n). A current sensor (70) provides a current feedback signal indicative of a converter current directly to at least one of the plurality of local controllers (721, ..., 72q). A main controller (74) provides a current reference signal, or current reference information for calculating a current reference signal, to the at least one local controller (721, ..., 72q) each main control cycle. The current reference signal is indicative of a desired converter current. The at least one local controller (721, ..., 72q) is adapted to optionally use the current reference information to calculate the current reference signal, and carry out current control for the associated at least one converter unit (521, 522, ..., 52n) on the basis of the current feedback signal and the current reference signal each local control cycle.