AC Voltage Fundamental Component Estimation via Cost Function Minimization
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Solution Overview
Problem
Existing methods for estimating fundamental components of AC voltage signals are complex, slow, and lack precision, particularly in noisy environments, which affects the control of electrical converters in medium voltage drives.
Innovation Solution
A method that receives time-varying measurement signals of AC voltage, parametrizes the fundamental component with a rated frequency, variable amplitude, and phase shift, and determines parameters by minimizing a cost function integrated over a time horizon, using least squares and trigonometric functions to stabilize calculations and facilitate online optimization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If complex filtering methods are used to estimate fundamental components of AC voltages, then measurement precision may be improved, but device complexity and calculation time increase significantly
Solution Approach 1:
The patent transforms the fundamental component estimation problem into a parameter optimization problem. Instead of using complex filtering methods, it defines a cost function based on the difference between measured voltage signals and a modeled fundamental component, then minimizes this cost function by adjusting parameters (amplitude, phase, frequency) to find the best fit. This parameter-based approach simplifies the estimation process while maintaining precision.
Solution Approach 2:
The patent replaces traditional mechanical/electrical filtering systems with a mathematical optimization approach. Instead of using physical filters or complex signal processing circuits, it uses a cost function minimization method that can be implemented through software or simple computational algorithms, thereby reducing device complexity while achieving accurate fundamental component extraction.
2Measurement precision
If traditional filtering methods are used for fundamental component estimation, then measurement precision may be improved, but processing speed decreases
Solution Approach 1:
The patent formulates the estimation as a parameter optimization problem where the cost function depends on parameters representing the fundamental component characteristics. By minimizing this cost function through parameter adjustment, the method achieves both precision and speed, as the optimization can be performed efficiently using numerical methods without requiring complex iterative filtering processes.
Solution Approach 2:
The patent prepares the estimation process by defining the cost function structure and parameter relationships in advance. The cost function is designed to directly relate measurement errors to parameter deviations, allowing the optimization algorithm to converge quickly to the solution. This preliminary formulation of the optimization problem enables fast processing while maintaining precision.
3Measurement precision
If complex filtering algorithms are applied to noisy voltage signals, then measurement precision may be improved, but loss of time increases due to extended processing
Solution Approach 1:
The patent addresses noisy signals by incorporating a parameter-based cost function that can handle measurement uncertainties. The cost function minimization process efficiently separates the fundamental component from noise by optimizing parameters that represent the signal's essential characteristics, achieving accurate extraction even in noisy conditions without requiring extensive processing time for noise filtering.
Solution Approach 2:
The patent extracts only the essential parameters of the fundamental component (amplitude, phase, frequency) from the noisy voltage signal through cost function minimization. By focusing on extracting these key parameters directly rather than attempting to filter out all noise components, the method achieves precise fundamental component estimation quickly, even in the presence of significant noise.
Data Source
AI summary
A method for estimating a fundamental component of an AC voltage includes receiving a timely varying measurement signal of the AC voltage; parametrizing a fundamental component of the AC voltage; and determining parameters of the fundamental component based on minimizing a cost function. The fundamental component has a rated frequency, a variable amplitude and a variable phase shift. The cost function is based on an integral of a norm of a difference between the measurement signal and the parametrized fundamental component via a time horizon. The time horizon starts at an actual time point and goes back via a predefined length. The cost function includes a term based on a norm of the difference between a value of the fundamental component at the actual time point and a value of a previously estimated fundamental component at the actual time point, where the previously estimated fundamental component has been determined for a previous time point.