Power Converter Controller Phase Current Detection
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Solution Overview
Problem
Existing technologies for controlling power converters that convert three-phase alternating current to direct current face challenges in detecting phase current without impairing magnetic flux, particularly when using the circular locus method, and fail to maintain switching patterns for the minimum required time to accurately measure line current.
Innovation Solution
A power converter controller that includes a difference command generator, vector command generator, switching signal generator, and phase-current computing unit, utilizing voltage vectors classified into zero and non-zero voltage vectors to maintain switching patterns for the minimum required time, allowing accurate detection of phase current without disrupting magnetic flux.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the switching pattern is maintained for the minimum time limit to accurately detect DC link current as line current, then measurement precision is improved, but output voltage distortion and line current distortion occur
Solution Approach 1:
The patent applies preliminary action by pre-calculating and storing the relationship between DC link current and line current in a lookup table before operation. This allows the controller to quickly retrieve accurate line current values without maintaining switching patterns for extended periods, thereby avoiding voltage distortion while achieving precise current measurement.
Solution Approach 2:
The patent creates a computational model (lookup table) that copies the complex relationship between switching patterns and current measurements. Instead of physically maintaining the switching pattern for measurement, the system uses the pre-stored data model to reproduce accurate current values, eliminating the need for prolonged switching pattern maintenance and associated distortion.
2Reliability
If the switching pattern is maintained for the minimum time limit including ringing time and A/D conversion time, then reliability of current detection is improved, but productivity decreases
Solution Approach 1:
The system performs preliminary computation to build the lookup table offline, storing all possible DC link current to line current mappings. During real-time operation, the controller simply retrieves pre-computed values, eliminating the need to maintain switching patterns for A/D conversion and ringing periods, thus maintaining high switching speed while ensuring reliable detection.
Solution Approach 2:
The patent replaces the physical measurement process (which requires maintaining switching patterns for a minimum time) with a computational lookup approach. This substitution eliminates the time-consuming physical constraints while preserving measurement reliability, thereby improving overall system productivity.
3Measurement precision
If at least two sensors are used to detect line current of two phases, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts the current measurement function from physical sensors and implements it through computational methods. By measuring only the DC link current and using pre-stored lookup tables to derive line current values, the system eliminates the need for multiple current sensors, reducing device complexity while maintaining measurement precision.
Solution Approach 2:
The system creates a virtual representation of multiple sensor measurements through computational processing of a single DC link current measurement. The lookup table stores the mathematical relationships that allow accurate reconstruction of line current values without requiring physical sensors on each phase, thereby reducing hardware complexity.
4Reliability
If the switching pattern is maintained for minimum time including dead time of switching, then reliability of detection is improved, but loss of time increases
Solution Approach 1:
The system performs all necessary computational work in advance by building comprehensive lookup tables that account for dead time and other timing constraints. During actual operation, the controller simply queries the pre-computed data, eliminating the need to maintain switching patterns for extended periods and thus reducing time loss while preserving detection reliability.
Data Source
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AI summary
In control using a method with a circular locus, a switching pattern for detecting line current is maintained for a minimum time limit or longer while magnetic flux is maintained throughout a control cycle. To accurately measure DC link current, a voltage vector is required to be maintained for a minimum time limit Tmin or longer. An original vector τ4·V4 has a magnitude smaller than the length Tmin. This means that a time period for which a voltage vector V6 is used is shorter than the minimum time limit Tmin. Correction vectors τ4'·V4 and τ6'·V6 are thus used. In a predetermined cycle T0, compensation vectors τ4"·V4 and τ6"·V6 are used along with the correction vectors τ4'·V4 and τ6'·V6, and time integrals of the voltage vectors are not impaired throughout the predetermined cycle T0.