Grid Impedance Estimation Using Relative Phase Angle
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Solution Overview
Problem
Conventional methods for estimating grid properties of a power grid face imprecision due to measurement noise, particularly in absolute phase changes, especially when frequency variations occur, which can be minimized by using multiple operating points but still pose challenges.
Innovation Solution
A method that estimates grid properties using measured voltage and current at the point of common coupling, along with the determined phase angle, eliminating the need for absolute phase measurements, and formulating the problem as a set of quadratic polynomial equations to determine grid impedance and voltage, which can be solved analytically or numerically.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional methods measure absolute phase changes between different operating points, then grid properties can be estimated, but measurement precision deteriorates due to frequency variations and measurement noise
Solution Approach 1:
The invention extracts and eliminates the absolute phase measurements from the estimation process. By formulating the grid model identification using only voltage amplitude, current amplitude, and relative phase angle between voltage and current, the method removes the source of measurement errors (absolute phase changes) while retaining the essential information needed to determine grid impedance and voltage.
Solution Approach 2:
The invention changes the measurement parameters from absolute phase angles to relative phase angle between voltage and current. This parameter transformation converts a noisy measurement (absolute phase) into a more reliable measurement (relative phase) that is less sensitive to frequency variations and measurement noise, while still providing sufficient information for grid model identification.
2Measurement precision
If multiple operating points are used to minimize measurement noise errors, then estimation accuracy improves, but the complexity of the measurement system increases
Solution Approach 1:
The invention extracts the essential information needed for grid model identification (voltage amplitude, current amplitude, relative phase angle) and formulates a solution that works effectively with minimal operating points. By removing the dependency on absolute phase measurements, the method achieves accurate estimation with fewer measurement requirements, thereby reducing system complexity.
3Reliability
If absolute phase measurements are used to identify grid model, then grid properties can be determined, but errors due to measurement noise increase
Solution Approach 1:
The invention converts the harmful effect of measurement noise on absolute phase measurements into a beneficial approach by completely eliminating absolute phase measurements from the process. The method uses only relative phase angle between voltage and current, which is inherently more robust to noise, thereby turning the limitation into an advantage.
Solution Approach 2:
The invention changes the measurement parameter from absolute phase (which is noise-sensitive) to relative phase angle between voltage and current (which is noise-robust). This parameter substitution maintains the ability to identify grid model parameters while significantly reducing sensitivity to measurement noise.
Data Source
AI summary
A method for estimating grid properties of a power grid coupled to a generator at a point of common coupling is provided. First, a voltage VPCC at the point of common coupling is measured. Second, a current IPCC at the point of common coupling is measured. Third, the grid properties are estimated by a grid model using as input parameters the measured voltage VPCC at the point of common coupling, the measured current IPCC at the point of common coupling and the determined phase angle. Advantageously, the absolute phases of the voltage and the current at the point of common coupling are not necessary, which makes the present method less prone to errors due to measurement noise. Further, a device and a computer program product are provided.