Modular Multilevel Converter Circulating Current Suppression
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Solution Overview
Problem
Modular multilevel converters connected in parallel experience circulating currents, leading to higher losses and complex control issues, which hinder efficient electrical power conversion with low losses and easy control.
Innovation Solution
The implementation of a converter arrangement with inductances between a common phase connection point and branch connection points to damp and control circulating currents, along with a protection system that includes fault detection and switching mechanisms to manage converter cells and phases during faults.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If modular multilevel converters are connected in parallel to handle higher power, then the power conversion capability is improved, but circulating currents occur causing higher losses and control complexity
Solution Approach 1:
The patent introduces a circulating current suppression controller as an intermediary component that mediates between parallel converters. This controller detects circulating currents and generates compensating control signals to cancel them out, thereby reducing energy losses while maintaining the parallel connection configuration for high power capability
2Power
If modular multilevel converters are connected in parallel to handle higher power, then the power conversion capability is improved, but control complexity increases
Solution Approach 1:
The circulating current suppression controller serves as an intermediary that simplifies the overall control structure. By centralizing the circulating current suppression function in this dedicated controller, the patent reduces the control burden on individual converter controllers and provides a systematic approach to managing parallel operation
Solution Approach 2:
The control system is segmented into multiple independent modules: individual converter controllers for basic conversion functions and a separate circulating current suppression controller for coordinating parallel operation. This segmentation allows each module to perform its specific function independently, reducing overall control complexity
3Adaptability or versatility
If semiconductor switches switch circulating currents, then the converter can operate in parallel configuration, but switching losses increase
Solution Approach 1:
The circulating current suppression controller acts as an intermediary that prevents semiconductor switches from having to handle circulating currents. By generating compensating signals that cancel circulating currents before they reach the switches, the patent enables parallel operation while minimizing switching losses
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 effectively reduces losses and simplifies control of the converter arrangement by damping circulating currents and providing reliable fault protection, ensuring efficient and stable power conversion.
Implementation Method 1
the at least two converter branches of the first modular multilevel converter are connected via a first branch connection point and the at least two converter branches of the second modular multilevel converter are connected via a second branch connection point; wherein the at least first and second multilevel converters are connected in parallel via a phase connection point for connecting the converter arrangement to a load or a power source, wherein the phase connection point is connected via a first inductance with the first branch connection point and via a second inductance with the second branch connection point
Data Source
AI summary
A converter arrangement comprises first and second modular multilevel converters, Each of the modular multilevel converters comprises two converter branches. Each converter branch comprises a plurality of series-connected converter cells. Each converter cell comprises a cell capacitor and semiconductor switches for connecting and disconnecting the cell capacitor to the converter branch. At least two converter branches of the first modular multilevel converter are connected via first branch connection point and at least two converter branches of the second modular multilevel converter are connected via second branch connection point. The multilevel converters are connected in parallel via a phase connection point for connecting the converter arrangement to a load or a power source, wherein the phase connection point is connected via a first inductance with the first branch connection point and/or via a second inductance with the second branch connection point. At least one of the modular multilevel converters comprises a protection system.