Self-Commissioning Three-Phase Power Converter Using Single-Frequency Perturbation
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Solution Overview
Problem
Existing self-commissioning techniques for grid-connected three-phase power electronic converters are complex and require injection of perturbations at multiple frequencies to identify dynamic characteristics, which is impractical for end-user facilities with unknown grid impedance, leading to instability and delayed commissioning.
Innovation Solution
A power control system that uses a sinusoidal perturbation injected at a single cross-over frequency to calculate gain values for the current controller, simplifying the parameter identification process and reducing the time required for tuning, by employing a perturbation module and parameter calculation module to determine gain values based on phase margin and cross-over frequency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If self-commissioning techniques apply perturbations on several frequencies to identify dynamic characteristics, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent extracts only the essential frequency component (cross-over frequency) needed for grid impedance identification, eliminating the need for multi-frequency perturbation analysis while maintaining sufficient measurement precision for controller commissioning
Solution Approach 2:
The patent introduces a single-frequency sinusoidal perturbation as an intermediary signal that simplifies the identification process by focusing on the critical cross-over frequency where grid impedance effects are most significant, avoiding the complexity of analyzing multiple frequencies
2Adaptability or versatility
If existing self-commissioning techniques are applied to grid-connected converters, then adaptability is improved, but device complexity increases
Solution Approach 1:
The patent changes the control approach by using fixed, pre-determined gain values based on cross-over frequency and phase margin specifications, eliminating the need for complex adaptive control strategies while maintaining adaptability to unknown grid impedance conditions
Solution Approach 2:
The patent performs preliminary determination of controller gains during the design phase based on specified cross-over frequency and phase margin requirements, allowing the controller to be universally applied to grid-connected converters without requiring complex on-site adaptation
3Manufacturing precision
If multiple frequency perturbations are injected for parameter identification, then manufacturing precision is improved, but loss of time increases
Solution Approach 1:
The patent extracts only the critical cross-over frequency component for parameter identification, eliminating the time-consuming multi-frequency sweep while maintaining sufficient precision for controller tuning by focusing on the frequency where stability margins are most critical
Data Source
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AI summary
A system for modulating a current level of a power grid includes a perturbation module 210 that injects a sinusoidal signal, at a cross-over frequency, to modulate a duty cycle to a power converter connected to the power grid; a current controller 212 that monitors a reference current and a current at grid-side terminal of the power converter, the current controller further monitors a current of the power grid; and a parameter calculation module 216 that calculates a plurality of gain values for the current controller based at least in part on a phase margin, a cross-over frequency, a current of an alternating current side of the power converter, and the duty cycle.