Doubly Fed Induction Generator Converter Frequency Control
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Solution Overview
Problem
High transistor switching speeds in power converters lead to increased junction temperatures and mechanical stress, particularly during start-up or low-frequency conditions, resulting in reduced converter lifespan due to excessive thermal and mechanical stress on bond wires.
Innovation Solution
Implementing a mechanism to reduce operating frequency and estimate junction temperature variations, adjusting the frequency when aging parameters exceed thresholds to prevent excessive aging, which may involve operating below maximum power point tracking mode to maintain converter lifespan and optimize performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If high transistor switching speeds are used to create smoother sinusoidal waveform, then output waveform quality is improved, but junction temperature and mechanical stress increase leading to reduced converter lifespan
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable rather than fixed. The control system dynamically adapts the switching frequency based on operating conditions, allowing high switching speeds for waveform quality when needed, but reducing switching frequency under start-up or low-speed conditions to limit thermal and mechanical stress on bond wires, thus resolving the contradiction between waveform quality and converter lifespan
Solution Approach 2:
The patent changes the switching frequency parameter dynamically based on operating conditions. By monitoring parameters such as output frequency and load conditions, the system adjusts the switching frequency to optimize both waveform quality and stress management, preventing excessive junction temperature variations and bond wire fatigue that would otherwise reduce converter lifespan
2Productivity
If maximum power point tracking mode is used to maximize power output, then productivity is improved, but junction temperature variation and mechanical stress increase reducing converter lifespan
Solution Approach 1:
The patent dynamically adjusts switching frequency based on operating conditions during MPPT operation. When operating at low output frequency with high current (conditions that cause excessive stress), the system reduces switching frequency to limit thermal cycling and mechanical stress, while maintaining power output optimization, thus resolving the contradiction between productivity and reliability
Solution Approach 2:
The control system incorporates feedback by monitoring operating parameters such as output frequency, current, and temperature conditions. Based on this feedback, the system adjusts the switching frequency to prevent excessive stress during MPPT operation, ensuring both high power output and extended converter lifespan by avoiding operating conditions that cause premature failure
Data Source
AI summary
The present techniques include methods and systems for operating converter to maintain a lifespan of the converter. In some embodiments, the operating frequency of the converter may be increased such that stress may be reduced on the bond wires of the converter. More specifically, embodiments involve calculating the aging parameters for certain operating conditions of the converter operating in a maximum power point tracking (MPPT) mode and determining whether the MPPT operation results in aging the converter to a point which reduces the converter lifespan below a desired lifespan. If the MPPT operation reduces the converter lifespan below the desired lifespan, the frequency of the converter may be increased such that the converter may be controlled to operate at a percentage of MPPT. Thus, in some embodiments, power output may be optimized with respect to maintaining a desired lifespan of the converter.