Phasor Frequency Measurement Using Dynamic Windowing
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing methods for measuring the frequency of phasor in grid-connected photovoltaic generation systems face interference from reference level fluctuations and inaccuracies in phase calculation, leading to asynchronous outputs and oscillations due to dynamic nonlinear characteristics.
Innovation Solution
A method involving a control module, data buffer, inverter, sampling module, and analog-to-digital conversion, using Fourier transform and Taylor series representation to calculate phasor values with least square methods, ensuring precision and synchrony, and outputting accurate phasor and frequency values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If hardware zero-crossing detection method is used, then the measurement can be implemented simply, but the precision is interfered by reference level fluctuation and noise
Solution Approach 1:
The patent replaces the hardware-based zero-crossing detection mechanism with a software-based digital signal processing approach. The analog-to-digital conversion module converts the analog signal to digital signal, and the control module uses discrete Fourier transform to calculate frequency, eliminating the need for hardware zero-crossing detection and its susceptibility to reference level fluctuations and noise interference.
Solution Approach 2:
The patent introduces an intermediary digital signal processing stage between the analog signal and frequency measurement. The analog-to-digital conversion module and the discrete Fourier transform algorithm act as intermediaries that filter out noise and reference level fluctuations, providing a more accurate frequency measurement compared to direct hardware zero-crossing detection.
2Ease of operation
If conventional discrete Fourier transform method is used, then the calculation process is straightforward, but the accuracy declines due to dynamic nonlinear characteristics causing frequency and amplitude changes
Solution Approach 1:
The patent applies dynamic window functions (Hanning, Hamming, or Blackman) that adapt to the changing signal characteristics in real-time. These window functions dynamically adjust the weighting of different time segments within the data window, allowing the system to handle frequency and amplitude changes effectively while maintaining measurement accuracy in dynamic nonlinear conditions.
Solution Approach 2:
The patent changes the parameter of the window function from a fixed conventional approach to a dynamic selectable approach. By providing options for different window functions (Hanning, Hamming, Blackman) and allowing dynamic adjustment based on signal characteristics, the system optimizes the balance between frequency resolution and amplitude accuracy for varying operating conditions.
3Device complexity
If phase calculation is performed inaccurately, then the calculation process remains simple, but the frequency calculation accuracy is influenced
Solution Approach 1:
The patent implements an iterative refinement process where the initial phase calculation from discrete Fourier transform is followed by a second-stage phase correction. The control module calculates the phase difference between the measured phasor and the reference phasor, then uses this feedback to correct the frequency calculation, ensuring high accuracy without excessive complexity.
Solution Approach 2:
The patent performs preliminary phase calculation using discrete Fourier transform to obtain an initial frequency estimate, then uses this preliminary result to guide the second-stage phase correction. This preliminary action allows the system to establish a baseline before applying more sophisticated correction algorithms, maintaining computational efficiency while improving accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This method eliminates reference level interference, prevents frequency spectrum leakage, and reduces oscillations by providing precise and synchronous phasor and frequency measurements, enhancing the accuracy and stability of grid-connected photovoltaic generation systems.
Implementation Method 1
an analog-to-digital conversion module, the analog-to-digital conversion module converting an analog signal sent by the voltage transformer into a digital signal
Implementation Method 2
the control module performs Fourier transform to signals of the data windows in the data buffer module
Data Source
AI summary
The present invention relates to a method for measuring the frequency of phasor of a power system, belonging to the technical field of power systems and automation thereof. A grid-connected photovoltaic generation system is provided with a control module, a data buffer module, an inverter, a sampling module and an analog-to-digital conversion module; a voltage transformer is connected to the grid side of the grid-connected photovoltaic generation system; the voltage transformer is electrically connected to the analog-to-digital conversion module; the analog-to-digital conversion module converts an analog signal sent by the voltage transformer into a digital signal; the sampling module samples the digital signal and transmits the digital signal into the data buffer module; the data buffer module is provided with a plurality of data windows; and the control module receives signals from the data windows.