Model Predictive Control of Electrical Converter Using Precomputed Pulse Patterns
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Solution Overview
Problem
Existing electrical converter control methods face challenges in producing output currents with low harmonic distortions at low fundamental frequencies, particularly at high pulse numbers, where optimized pulse patterns become difficult to calculate and require significant memory resources.
Innovation Solution
A method for controlling electrical converters that determines a modulating signal vector from a stator flux reference vector, adjusts switching patterns using pulse width modulation, and modifies transition time instants to minimize stator flux error, thereby reducing higher-order harmonics, while being computationally efficient and applicable at high pulse numbers.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If optimized pulse patterns are used to reduce harmonic content, then harmonic distortions are reduced, but calculation complexity and memory requirements increase significantly at high pulse numbers
Solution Approach 1:
The patent segments the control approach by using pre-calculated optimized pulse patterns for low pulse numbers (where harmonic reduction is most beneficial) and switching to alternative control methods for high pulse numbers. This segmentation allows the system to achieve harmonic reduction where needed without incurring the high computational costs at all operating points.
Solution Approach 2:
The patent changes the control parameter strategy by selecting different control methods based on the pulse number parameter. At low pulse numbers, optimized pulse patterns with specific switching sequences are used to minimize harmonics. At high pulse numbers, the system transitions to other modulation schemes, effectively changing the control approach based on operating conditions to avoid excessive computational requirements.
2Object-generated harmful factors
If optimized pulse patterns are calculated for high pulse numbers, then harmonic content is reduced, but the control method becomes computationally demanding and difficult to implement
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing optimized pulse patterns for low pulse numbers before actual operation. These pre-computed patterns are readily available during operation, eliminating the need for real-time calculation of complex optimized patterns. This preliminary preparation makes the system easy to implement while still achieving harmonic reduction where it matters most.
3Object-generated harmful factors
If switching frequency is increased to achieve high pulse numbers, then output current quality improves, but switching losses and computational burden increase
Solution Approach 1:
The patent changes the control strategy based on the pulse number parameter, using optimized patterns only when beneficial (low pulse numbers) and switching to alternative methods at high pulse numbers. This prevents unnecessary switching operations that would increase losses while maintaining current quality through appropriate control method selection.
Data Source
AI summary
A method for controlling a three-phase electrical converter includes selecting a three-phase optimized pulse pattern from a table of pre-computed optimized pulse patterns based on a reference flux. The method includes determining a two-component optimal flux from the optimized pulse pattern and a one-component optimal third variable. The method includes determining a two-component flux error from a difference of the optimal flux and an estimated flux estimated based on measurements in the electrical converter. A one-component third variable error is determined from a difference of the optimal third variable and an estimated third variable. The optimized pulse pattern is modified by time-shifting switching instants of the optimized pulse pattern such that a cost function depending on the time-shifts is minimized. The method includes applying the modified optimized pulse pattern to the electrical converter.