Delta MMC STATCOM Using Anti-Series Half-Bridge Submodules
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Solution Overview
Problem
The transition from centralized to decentralized energy generation systems, such as wind turbines and photovoltaic systems, has created a need for reactive power delivery in electrical power grids, which existing technologies struggle to address efficiently due to high development and manufacturing costs associated with dual-polarity submodules in multilevel power converters.
Innovation Solution
A multilevel power converter design featuring three module branches in a delta connection, utilizing only unipolar submodules with half-bridge configurations, eliminating the need for costly full-bridge submodules and allowing controlled generation and delivery of reactive power by alternating polarities within the converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If dual-polarity submodules (full-bridge submodules) are used in multilevel power converters, then reactive power delivery capability is improved, but development and manufacturing costs increase significantly
Solution Approach 1:
The patent divides the module branch into two separate groups of submodules: first group submodules with unipolar energy storage devices connected with first polarity, and second group submodules with unipolar energy storage devices connected with second polarity. This segmentation allows each submodule type to be simpler and cheaper while collectively achieving dual-polarity functionality through anti-series connection of the two groups.
Solution Approach 2:
The patent makes both first group and second group submodules identical in structure (both using unipolar energy storage devices and half-bridge circuits), allowing a single submodule design to serve multiple functions when connected in anti-series configuration. This universal design reduces manufacturing complexity and costs compared to using different full-bridge submodule designs.
2Ease of manufacture
If unipolar submodules with half-bridge configurations are used, then manufacturing costs are reduced, but the ability to generate both positive and negative voltages becomes more complex
Solution Approach 1:
The patent segments the voltage generation function into two separate submodule groups: first group submodules generate positive voltages (first polarity) and second group submodules generate negative voltages (second polarity). By dividing the functionality and connecting the groups in anti-series, the system achieves bidirectional voltage capability without requiring complex full-bridge submodules.
Solution Approach 2:
Instead of using full-bridge submodules that can natively handle both polarities, the patent inverts the approach by using two sets of unipolar submodules connected in anti-series. The inversion of connection topology (anti-series rather than parallel) enables the simpler unipolar submodules to collectively provide the bidirectional voltage capability traditionally requiring complex dual-polarity submodules.
Data Source
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AI summary
The invention relates to an arrangement (1) with a multilevel converter (3) for supplying reactive power to a power supply network (10). The multilevel converter (3) has three module branches (301, 302, 302) arranged in a delta connection. Each module branch (301, 302, 302) has a plurality of submodules (510) connected in series. Each module branch (301, 302, 302) has a first group (311) of submodules (510) and a second group (312) of submodules (510). The submodules (510) of the first group (311) each have a first electrical energy storage device (618), a first electronic switching element (701) and a second electronic switching element (702), wherein the first electronic switching element (701) and the second electronic switching element (702) are arranged such that the first electrical energy storage device (618) can be connected in series with a first polarity (U1).