Modular Multilevel Converter Circuit for Low-Loss Ancillary Supply
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Solution Overview
Problem
Existing DC converters in AC batteries face inefficiencies and losses due to the need for semiconductor switches to handle ancillary supply currents, particularly when providing low-voltage outputs like 48 V or 12 V, and require complex connections that increase impedance and reduce efficiency.
Innovation Solution
A method and circuit design for a modular multi-level converter that forms single or dual star points within the converter modules, allowing direct connection of ancillary terminals to common potential terminals, bypassing semiconductor switches and reducing impedance, and using converters like synchronous, dual active bridge, or LLC converters to provide ancillary supplies efficiently.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If semiconductor switches are used to handle ancillary supply currents in existing DC converters, then voltage conversion from high-voltage to low-voltage is achieved, but switch losses and energy loss increase
Solution Approach 1:
The patent extracts the ancillary supply current path from the main DC converter circuit by introducing a separate winding on the transformer. This allows the ancillary supply to be provided without passing through the semiconductor switches, thereby eliminating switch losses for this specific function while maintaining the voltage conversion capability for main power.
Solution Approach 2:
The patent segments the power conversion function into two independent paths: one for main power conversion through the DC converter with semiconductor switches, and another for ancillary supply through a separate transformer winding. This segmentation allows each path to be optimized independently, reducing overall energy loss.
2Ease of operation
If complex connections are made to provide ancillary supply in existing DC converters, then low-voltage output is achieved, but impedance increases and efficiency decreases
Solution Approach 1:
The patent extracts the ancillary supply function from the complex DC converter circuitry and provides it through a dedicated transformer winding. This creates a direct, low-impedance connection from the high-voltage side to the low-voltage ancillary output, bypassing the complex switching networks and reducing impedance losses.
3Device complexity
If DC converters are connected to the same terminals as the inverter in AC batteries, then modular design is achieved, but ancillary supply efficiency decreases due to shared circuit paths
Solution Approach 1:
The patent segments the electrical connections within the modular AC battery system by providing a dedicated transformer winding for ancillary supply that is electrically independent from the inverter connections. This allows the modular design to be maintained while eliminating shared circuit path losses, as the ancillary supply has its own dedicated path from the battery terminals.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The proposed method and circuit reduce semiconductor switch losses and impedance, enabling efficient ancillary supply outputs independent of high-voltage systems, with lower impedance and reduced energy loss, particularly for low-voltage consumers.
Implementation Method 1
A first ancillary supply is provided in the respective strand by connecting a selected converter to an associated selection from among the respective ancillary terminal, the common positive potential terminal, and the common negative potential terminal
Data Source
AI summary
A method for ancillary supply in a modular multi-level converter with a plurality of modules arranged in strands, a respective module including at least two half bridges with semiconductor switches and at least one energy accumulator, which are interconnected in parallel. In the respective module, an at least single-core input terminal is formed through respective center tapping in at least one half bridge on an input side, and an at least single-core output terminal is formed through respective center tapping in at least one half bridge on an output side. The strands are interconnected into at least one star point on the at least single-core input terminal of a first module in the respective strand. A respective phase of a supply voltage in a high-voltage system is formed on the at least single-core output terminal of a last module in the respective strand.