Modular Converter Control for Submodule Adaptability
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Solution Overview
Problem
Existing multilevel converter systems face challenges in easily adapting their regulation to varying numbers of submodules and network voltages, leading to complexity and inefficiency in managing circulating currents and energy storage.
Innovation Solution
The implementation of a closed-loop control system with independent drive units for each phase module branch, allowing for dynamic regulation of submodule control signals based on branch nominal values, decoupling regulator variables, and effectively managing circulating currents through phase module branch current regulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a modular converter with distributed energy storage devices is used, then adaptability to different numbers of submodules and network voltages is improved, but device complexity increases due to multiple submodules and control requirements
Solution Approach 1:
The converter is divided into multiple independent phase modules, each containing several submodules that can be independently controlled. This segmentation allows the system to adapt to different configurations by enabling or disabling specific submodules without affecting the entire system, thus improving adaptability while managing complexity through modular independence.
Solution Approach 2:
The control system dynamically adjusts the number of active submodules based on operating conditions, network voltage levels, and power requirements. This dynamic reconfiguration capability allows the converter to optimize its performance for different scenarios while maintaining a manageable control structure through systematic switching strategies.
2Reliability
If circulating currents are actively damped through control of branch currents, then reliability and stability are improved, but device complexity increases due to additional control mechanisms
Solution Approach 1:
The control system continuously monitors branch currents and uses feedback control to actively damp circulating currents. By measuring actual current values and comparing them with reference values, the system automatically adjusts switching signals to eliminate unwanted circulating currents, thereby improving reliability and stability through systematic feedback mechanisms rather than complex passive damping elements.
3Ease of operation
If closed-loop control means with current regulation unit and drive units are implemented, then ease of operation is improved through simplified adaptation, but device complexity increases due to additional control components
Solution Approach 1:
The current regulation unit and drive units are designed with universal functionality that can handle multiple tasks: regulating active power, reactive power, and damping circulating currents through a unified control architecture. This multi-functionality simplifies operation by providing a single interface for managing various converter functions while avoiding the need for separate specialized control circuits for each function.
Data Source
AI summary
A device for converting an electrical current includes at least one phase module with an AC connection and at least one DC connection. A phase module branch is provided between each DC connection and each AC connection. Each phase module branch has a series connection made of sub-modules, which in turn include an energy accumulator each and at least one power semiconductor. Measuring sensors provide actual values and there are provided control means connected to the measuring sensors. The control can be easily adapted to any arbitrary number of sub-modules in each phase module branch. The control means include a current regulating unit and control units associated with a phase module branch each, wherein the current regulating unit is configured to provide branch target values for the control units. The control units are designed to produce control signals for the sub-modules.