Harmonic Disturbance Source Separation in Power Grid Connections
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Solution Overview
Problem
Current methods fail to accurately distinguish between harmonic disturbances caused by power converters and those already present in the power grid, limiting the effectiveness of active filtering and harmonic emission control in electric power generating systems connected to the grid.
Innovation Solution
A method that represents the electric power generating system using an equivalent voltage source and characteristic impedance to separate disturbances into those originating from the system and the grid, allowing for independent analysis and mitigation of each component.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If current methods are used to measure harmonic disturbances at the connection point, then the overall disturbance level can be measured, but the inability to distinguish between system-caused and grid-caused harmonics limits the effectiveness of active filtering and harmonic emission control
Solution Approach 1:
The patent segments the total harmonic disturbance into two distinct components: harmonics caused by the power generating system and harmonics present in the grid. This is achieved by separately determining the open circuit voltage (representing system-caused harmonics) and the grid impedance (representing grid-caused harmonics), allowing independent analysis and control of each source without requiring complex additional measurement equipment
Solution Approach 2:
The patent introduces an intermediary measurement approach by determining the open circuit voltage at the connection point as a mediator variable. This open circuit voltage serves as a bridge that, when combined with grid impedance measurements, enables the separation of disturbance sources without directly requiring complex source identification hardware
2Reliability
If active filtering and harmonic emission control are implemented without accurate disturbance source identification, then some level of harmonic mitigation can be achieved, but the effectiveness is limited due to inability to target specific disturbance sources
Solution Approach 1:
The patent implements a feedback mechanism where the determined open circuit voltage and grid impedance are used to calculate the contribution of each disturbance source. This feedback information is then used to adjust the power generating system's operation to actively control and mitigate its own harmonic emissions, improving control effectiveness through continuous monitoring and adjustment
Solution Approach 2:
The patent replaces complex mechanical or hardware-based disturbance source identification systems with an electrical measurement and calculation approach. By using open circuit voltage measurements and impedance calculations, the system substitutes sophisticated source differentiation hardware with simpler electrical measurements and computational analysis
Data Source
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AI summary
It is described a method for decomposing a disturbance on an electric signal being present at an electric connection (170) between an electric power generating system (110, 600) and a power grid (150) into a first disturbance (II (n) ) with a first strength, wherein the first disturbance is assigned to the electric power generating system (110, 600), and a second disturbance (12 (n) ) with a second strength, wherein the second disturbance is assigned to the power grid (150). The described method comprises (a) determining a voltage value (Um (n) ) of a voltage of the electric signal, (b) determining a current value (Im(n)) of a current of the electric signal (c) calculating a value of an open circuit voltage (Upwm(n)) of an equivalent voltage source (212) characterizing the electric power generating system (110, 600) in a harmonic model of the electric power generating system (110, 600) based on the measured voltage value, on the measured current value and on a characteristic equivalent impedance (Zchm(n))) of the electric power generating system (110, 600), and (d) determining the strength of the first disturbance (II (n) ) based on the calculated value of the open circuit voltage (Upwm(n)) of the equivalent voltage source (212).