Cascade Tracking Filters for Grid Synchronization
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Solution Overview
Problem
Voltage imbalances and harmonic distortions disrupt the synchronization of electrical grids, leading to current imbalances that stress grid devices and affect the efficient transmission and distribution of power.
Innovation Solution
A method and system utilizing sequential tracking filters and a phase-locked loop (PLL) to determine and remove disturbance frequencies from the phase voltage, producing a clean frequency for synchronized operation, thereby mitigating the effects of voltage imbalances and harmonic distortions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If voltage imbalances and harmonic distortions are present in the grid, then the grid can operate with simple synchronization methods, but the synchronization accuracy and grid performance deteriorate due to current imbalances and device stress
Solution Approach 1:
The synchronization system is segmented into multiple independent tracking filters, each dedicated to detecting specific harmonic frequencies. This segmentation allows the system to process different frequency components separately, improving the accuracy of fundamental frequency detection while effectively handling voltage imbalances and harmonic distortions without compromising grid performance.
Solution Approach 2:
Tracking filters serve as intermediary components between the distorted grid voltage and the synchronization system. These filters selectively pass the fundamental frequency while attenuating harmonic disturbances, acting as mediators that protect the synchronization process from the harmful effects of voltage imbalances and harmonic distortions.
2Measurement precision
If sequential tracking filters are used to remove disturbance frequencies, then the clean frequency for PLL operation is improved, but the system complexity increases
Solution Approach 1:
Each tracking filter in the sequential arrangement is designed to perform multiple functions: detecting specific harmonic frequencies, attenuating those harmonics, and providing clean output to subsequent stages. This multi-functionality reduces the need for additional dedicated components, thereby limiting the increase in system complexity while achieving high frequency detection accuracy.
Solution Approach 2:
The sequential tracking filters perform preliminary action by removing harmonic disturbances before the signal reaches the PLL. This pre-cleaning of the signal reduces the burden on the PLL and subsequent processing stages, achieving high frequency detection accuracy without requiring overly complex real-time processing in later stages.
3Reliability
If disturbance frequencies are removed sequentially through multiple tracking filters, then the current imbalance is reduced, but the processing time and computational load increase
Solution Approach 1:
The tracking filters are designed to operate at the fundamental frequency and its harmonics, using periodic filtering actions that align with the grid frequency. This periodic operation allows the system to efficiently remove disturbances at known frequency intervals without requiring continuous complex processing, thereby reducing processing time while maintaining high reliability through effective disturbance rejection.
Data Source
AI summary
Present embodiments relate to a method for synchronizing an electric grid. The method includes receiving a phase voltage of the electric grid. The method further includes determining one or more disturbance frequencies in the phase voltage via a plurality of sequential tracking filters, wherein each of the plurality of tracking filters corresponds to a harmonic of the received phase voltage. The method further includes removing the disturbance frequencies components sequentially to produce a minimally distorted frequency, and performing a PLL operation on the clean frequency to determine a phase angle of the frequency.