應用小波理論與迴歸法修正比流器飽和電流之電驛晶片設計

Correcting Saturated CT Current Using FPGA Chip Based on Wavelet and Regression

魏大韋(Da-Wei Wei)

指導教授 ： 洪穎怡

中原大學/工學院/電機工程研究所/碩士(2008年)

https://doi.org/10.6840/cycu200800440

摘要

在電力保護系統中，過電流電驛是經由前端比流器取其二次側信號，傳入電驛進行有效值計算，然而當故障發生時，往往產生極大電流並帶有直流成份，造成比流器飽和，使得傳入電驛之電流發生畸變，而比實際值來得小，因此會使過電流電驛誤動作，甚至沒有動作，而引起系統不穩定或設備之損壞，進而造成重大的經濟損失。因此本文發展一可自動偵測與修正電流信號畸變之過電流晶片，此晶片可做為未來發展智慧型電子元件之雛型。
本文以小波轉換先偵測每一週波之瞬間二次側電流值，以判斷每一週波畸變開始與結束時間，以便進行修正。另外再以迴歸法進行畸變波形之修正。本文在電腦擬軟體Matlab環境下以模糊C分割法合併統計檢定的方法將資料分成四十二類，建立完成之四十二個迴歸方程式，而於測試或線上使用時，則透過Takagi-Sugeno-Kang模糊規則合成最後結果。本文以晶片設計之Verilog硬體描述語言實現上述小波轉換、迴歸法及Takagi-Sugeno-Kang模糊規則，並設計成矽智產模組(SIP)。
最後本文使用Matlab/Simulink模擬一161 kV傳輸線保護系統，並取其模擬之結果，來驗證場規劃邏輯閘陣列(FPGA)晶片之精確度及其功能符合設計之要求。

關鍵字

小波轉換 ； 統計檢定 ； 模糊理論 ； 場規劃邏輯閘陣列(FPGA)晶片設計 ； 迴歸法

並列摘要

In the power protection system, the overcurrent relay employs the secondary current from the current transformer (CT) for evaluating RMS values and then determines the operation action. However, a large current incorporating with DC offset will cause the CT to be saturated when the fault occurs. When the CT saturates, the secondary current becomes distorted and smaller than the actual value. This condition will result in relay malfunction and cause the system unstable or the facility damaged. It will also cause great pecuniary loss. Therefore this thesis develops an overcurrent chip of automatic detecting and correcting saturation of the current transformer.
The wavelet transform is adopted to detect the distortion portion of the CT instantaneous secondary current in each cycle. The starting and ending instants of a distortion period are identified for compensating. The regression method is used to correct distorted waveform. The fuzzy-c-means is combined with statistical hypothesis to classify the fault data into forty-two clusters using Matlab. Forty-two regression formulas are used for testing and on-line application, and the Takagi-Sugeno-Kang fuzzy rules are considered to attain the final inference from the regression outputs. The above wavelet transform, regression method and Takagi-Sugeno-Kang fuzzy rules are designed by using Verilog Hardware Description Language (VHDL) in a Silicon Intellectual Property (SIP) module.
This thesis uses a 161 kV transmission line protection system for simulation by Matlab/Simulink. The overcurrent values are attained from simulation results to validate the precision of the FPGA chip design and verify the function of the designed chip.

並列關鍵字

Wavelet Transform ； Fuzzy Set Theory ； FPGA Chip Design. ； Regression Method ； Statistical Hypothesis

參考文獻

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