M2LC Subsystem Current Source Power Supply for Fault Tolerance
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Solution Overview
Problem
The Modular Multilevel Converter (M2LC) topology faces challenges in controlling DC link voltages during pre-charge and fault conditions due to its reliance on internal energy storage, which can lead to system damage and loss of cell control power when cells are bypassed, and requires higher bus voltages that complicate switch mode power supply design.
Innovation Solution
A modular multilevel converter system with a plurality of M2LC subsystems connected to a current source power supply external to the subsystems, using current transformers to provide independent control power to each subsystem, allowing for independent operation and fault tolerance by decoupling cell control power from the DC link voltage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If M2LC cells use internal capacitor energy storage to control DC link voltages, then the system can achieve modular operation, but during pre-charge or fault conditions when cells are bypassed, the DC link voltages cannot be controlled and may cause system damage
Solution Approach 1:
The power supply system is segmented into independent units, with each M2LC cell having its own isolated power supply unit. This segmentation allows each cell to be independently controlled and powered, enabling the system to maintain reliability during pre-charge and fault conditions while preserving modular operation capability.
Solution Approach 2:
An external current source power supply acts as an intermediary to provide controlled current during pre-charge operations. This external power supply mediates the charging process, allowing DC link voltages to be controlled independently of the M2LC cell switching states, thereby preventing system damage during pre-charge and fault conditions.
2Device complexity
If M2LC topology uses higher bus voltages (two or four times CCH design) to normalize power switch count, then the number of IGBT switches is reduced, but the design of switch mode power supply for gate control becomes more challenging
Solution Approach 1:
The power supply system is divided into independent modular units, each serving a specific M2LC cell. This segmentation allows the power supply design to be standardized and replicated, simplifying the overall design process despite the high voltage requirements. Each module can be designed and tested independently, reducing the complexity of managing high-voltage power supplies across the entire system.
Solution Approach 2:
The invention changes the fundamental parameter of power supply architecture from voltage-based to current-based control. By using an external current source power supply, the system can operate at high bus voltages while the power supply design focuses on current control characteristics rather than voltage regulation, simplifying the design of switch mode power supplies for gate control in high-voltage M2LC applications.
3Object-affected harmful factors
If M2LC cell control or gate control fails and cells are shut down, then faulty portions are bypassed, but the DC link voltage that supplies cell power supplies is lost, causing loss of cell control power
Solution Approach 1:
The power supply function is extracted from the M2LC cell structure itself and placed in an external current source power supply. This extraction ensures that cell control power is not dependent on the cell's operational state or DC link voltage, allowing faulty cells to be isolated while maintaining control power availability for healthy cells and enabling safe pre-charge operations.
Solution Approach 2:
An external current source power supply serves as an intermediary that provides control power independent of the M2LC cell status. This intermediary power supply ensures that cell control power remains available even when cells are shut down due to faults, as the power supply is not directly coupled to the cell's operational state or DC link voltage.
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
This solution ensures reliable cell control power under all operating conditions, including fault conditions, by providing independent power supply to each M2LC subsystem, enabling safe pre-charge and bypass functionality without voltage limitations, and allowing for the use of high-voltage IGBTs without significant design changes.
Implementation Method 1
using current transformers to provide independent control power to each subsystem
Data Source
AI summary
A system. The system is a modular multilevel converter system and includes a plurality of series connected two-terminal modular multilevel converter subsystems. The subsystems are magnetically coupled to an AC current source power supply.