Adaptive Sampling for Motor Bus Transfer Accuracy
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Solution Overview
Problem
Existing digital systems for transferring motor bus power from a main source to an auxiliary source during interruptions suffer from inaccuracies in calculating voltage magnitude and phase angle, especially when frequency deviates from nominal values, leading to potential motor damage and service disruptions in industrial facilities.
Innovation Solution
The system employs adaptive techniques, including the use of positive sequence voltage phasors for three-phase measurements and an adaptive time window discrete Fourier transform algorithm for single-phase measurements, to accurately determine the breaker closing point, ensuring smooth and synchronous transfer of power without interruption.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If constant sampling rate and fixed number of samples per fundamental frequency cycle are used, then the system structure is simple, but measurement precision deteriorates when frequency deviates from nominal value
Solution Approach 1:
The patent applies dynamics by making the sampling system adaptive rather than fixed. The sampling rate and number of samples per cycle dynamically adjust based on the actual frequency detected. When frequency deviates from nominal (50 or 60 Hz), the system automatically modifies sampling parameters to maintain measurement accuracy, resolving the contradiction between simple structure and precise measurement under varying conditions.
Solution Approach 2:
The patent changes sampling parameters (sampling rate and samples per cycle) based on frequency conditions. Instead of using a fixed sampling scheme, the system detects frequency deviations and adjusts sampling parameters accordingly. This parameter adaptation allows accurate voltage magnitude and phase angle calculations even when frequency varies from nominal values, while maintaining relative system simplicity through algorithmic adjustment rather than hardware complexity.
2Productivity
If fast transfer is implemented to minimize power interruption time, then productivity is improved, but measurement precision may deteriorate due to reduced sampling time window
Solution Approach 1:
The patent resolves this contradiction by dynamically adjusting the sampling strategy based on the transfer phase. During normal operation, standard sampling is used. During transfer operations, the system detects frequency and adapts the sampling rate and window size to achieve sufficient measurement precision within the reduced time available. This dynamic adaptation enables fast transfers while maintaining calculation accuracy through optimized sampling parameters matched to the available time window.
Solution Approach 2:
The system performs preliminary frequency detection and sampling parameter adjustment before the actual transfer execution. By预先 determining the appropriate sampling rate and window size based on detected frequency conditions, the system prepares the measurement parameters in advance, ensuring that even with reduced sampling time during fast transfer, sufficient data points are captured for accurate voltage magnitude and phase angle calculations.
Data Source
AI summary
In industrial complexes and power stations a main source of power is connected to a motor bus to which motors and other loads are connected. In such systems an auxiliary source of power is provided to alternatively provide electric energy to the motor bus should the main source of power be interrupted. In the prior art digital system, samples are taken of the motor bus and auxiliary system voltage waveform with a fixed time window to predict the proper time for closing the breaker. The present invention improves on the prior art by applying the concept of an adaptive time window wherein the number of samples taken during each cycle to obtain the operating parameters is increased as the frequency decreases. This provides more accurate parameters for calculating the point for closing.