Modular MMC Phase Arm Control with Parallel Cell Group Modulation
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
The complex control of modular multilevel converters (MMCs) with numerous converter cells in each phase arm requires substantial computing power, limiting overall performance due to increased latency and complexity.
Innovation Solution
The method involves dividing the main reference into multiple reference parts and grouping converter cells into smaller groups, each controlled by a separate modulator operating in parallel. This allows for independent control of each group, reducing the computational burden and improving efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a large number of converter cells are used in each phase arm to improve harmonic performance and voltage waveform quality, then the MMC can synthesize a voltage waveform that closely matches a sine-wave, but the control complexity and computing power requirements increase substantially
Solution Approach 1:
The phase arm is divided into multiple independent groups, each controlled by a separate modulator. This segmentation allows the control system to manage fewer cells per modulator, reducing individual control complexity while maintaining overall system performance through parallel operation of multiple modulators
2Reliability
If a large number of converter cells are used in each phase arm to improve harmonic performance, then the MMC achieves reduced harmonics and improved efficiency, but the control latency increases due to substantial computing power requirements
Solution Approach 1:
By segmenting the converter cells into multiple groups with dedicated modulators, the control computations are distributed and executed in parallel. This reduces the computational burden per modulator and decreases overall control latency while maintaining the harmonic performance benefits of having many converter cells
Solution Approach 2:
The modulators are configured to independently control their respective groups of cells, preparing control decisions in advance for each group. This preliminary organization of control tasks reduces processing time and latency when voltage balancing and modulation decisions must be made
3Productivity
If substantial computing power is allocated to control all converter cells, then the MMC can balance converter cell voltages multiple times per second, but the overall performance is limited by the available computing power
Solution Approach 1:
The control system is segmented into multiple independent modulators, each handling a subset of converter cells. This allows voltage balancing to be performed in parallel across multiple groups, effectively increasing control speed without requiring a single powerful computing unit to handle all cells sequentially
Solution Approach 2:
Each modulator independently balances its assigned group of cells, performing partial action on the overall system. This distributed approach achieves system-wide voltage balancing through multiple partial actions executed in parallel, increasing productivity without proportionally increasing individual modulator complexity
Data Source
AI summary
There is provided a method of controlling a plurality of converter cells in a phase arm of a modular multilevel converter (MMC) in accordance with a main reference. The method includes dividing the main reference into a plurality of reference parts, and, by using a grouping of the plurality of converter cells into a plurality of groups, operating a plurality of modulators in parallel, each modulator controlling a respective one of the groups of converter cells in accordance with one of the reference parts. A phase arm controlled in accordance with such a method is also provided, as well as an MMC including at least one such phase arm, and a converter station including at least one such MMC.