Modular Multi-Level Converter Switching Frequency Control
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Solution Overview
Problem
High-voltage direct current (HVDC) transmission systems, particularly modular multi-level converters, suffer from significant energy losses due to switching operations, which account for up to one-third of total energy losses, and current methods do not dynamically adapt switching frequencies to operating conditions, leading to inefficient energy use.
Innovation Solution
The method dynamically adjusts the switching frequency of semiconductor switches in modular multi-level converters based on operating parameters such as load conditions, junction temperature, and energy prices, allowing for independent frequency setting for each module to minimize energy losses and optimize operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching frequency of semiconductor switches is increased to improve voltage control precision, then the output voltage accuracy is improved, but energy losses due to switching operations increase
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control device dynamically adapts the switching frequency based on operating conditions such as load demands and temperature, allowing the system to optimize between voltage accuracy and energy efficiency in real-time different operating conditions
Solution Approach 2:
The patent changes the parameter of switching frequency from a constant value to a variable parameter that can be adjusted according to operating conditions. By modifying this key parameter based on temperature and load, the system achieves optimal performance across different scenarios without being constrained by a fixed frequency
2Stability of the object's composition
If the switching frequency is kept high to maintain stable voltage output, then the voltage stability is improved, but energy efficiency deteriorates
Solution Approach 1:
The system dynamically adjusts switching frequency based on actual operating conditions rather than maintaining a fixed high frequency. This allows voltage stability to be maintained when necessary while reducing energy consumption during partial load operations or when extreme precision is not required
3Device complexity
If a fixed switching frequency is used to simplify control, then the control system complexity is reduced, but adaptability to different operating conditions deteriorates
Solution Approach 1:
The control device incorporates feedback mechanisms that monitor operating conditions such as temperature and load demands. Based on this feedback, the system automatically adjusts the switching frequency, providing adaptability to different operating conditions while maintaining relatively simple control architecture
Solution Approach 2:
The control system performs self-adjustment of switching frequency based on monitored operating conditions. The converter autonomously optimizes its own operation by adapting the switching frequency to current temperature and load conditions without requiring complex external control
4Loss of energy
If the switching frequency is reduced to minimize energy losses, then energy efficiency is improved, but the precision of voltage control deteriorates
Solution Approach 1:
The switching frequency is made dynamic rather than static, allowing the system to use lower frequencies when energy efficiency is prioritized and higher frequencies when voltage control precision is critical. This dynamic adaptation resolves the contradiction by allowing both extremes to be utilized appropriately based on operating conditions
Data Source
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AI summary
The invention relates to a method for controlling a modular multi-level converter (4) having sub-modules (9), wherein each sub-module (9) has semiconductor switches (T1,T2), wherein the semiconductor switches (T1,T2) are controlled using a switching frequency (f) in order to provide an alternating voltage (16) as the output voltage of the converter (4), characterised in that an operating state of the converter (4) is determined and the switching frequency (f) of the semiconductor switches (T1,T2) is set according to the operating state, such that an operating aspect of the converter (4) is optimised. The invention also relates to a control device for a modular multi-level converter and to a modular multi-level converter having said control device.