Analiza obstoječih metod za merjenje frekvence električne napetosti v elektroenergetskih sistemih

Vardić, Anja (author), Rudež, Urban (mentor)

Upravljanje kompleksnega sistema, kot je elektroenergetski sistem, je sestavljeno iz številnih ključnih elementov, med katerimi ima ključno vlogo tudi merjenje frekvence. Obstoječe metode merjenja frekvence temeljijo na različnih matematičnih pristopih. V diplomskem delu je poudarek na treh, in sicer sinusnem prileganju, detekciji prehoda skozi nič in kratkotrajni Fourierjevi transformaciji (STFT). Za namen preizkušanja teh metod sem sprva definirala vhodni signal električne napetosti z vnaprej določenim potekom frekvence. V naslednjem koraku sem se osredotočila na vpliv harmonskega popačenja vhodnega signala in dolžine časovnega okna meritve frekvence. Za ugotavljanje, ali so te metode sprejemljive za uporabo v praksi, so potrebni dodatni testi. Ti so navedeni v standardu IEEE-C37.118.1-2011, in sicer ločeno za ustaljeno stanje in za dinamične pojave. Po treh izvedenih testih smo ugotovili, da so vse metode uspešno prestale vsaj en test za dinamične razmere, vendar nobenega za ustaljeno stane. Pri zahtevah, vezanih na hitrost merjenja (aplikacije za merjenje v realnem času), so se vse metode izkazale kot neuspešne zaradi občutljivosti na zgoraj omenjena parametra in težav s konvergenco. Iz tega sledi, da bi bila za sprejemljive rezultate merjenja frekvence v realnem času priporočljiva uporaba dodatnih metod.

• Language: Slovenian
• Keywords: merjenje frekvence, IEEE C37.118.1-2011, sinusno prileganje, detekcija prehoda skozi nič, kratkotrajna Fourierjeva transformacija
• Work type: Bachelor thesis/paper
• Organization: FE - Faculty of Electrical Engineering
• Year: 2023
• PID: 20.500.12556/RUL-149214
• COBISS.SI-ID: 163344899
• Publication date in RUL: 05.09.2023

Secondary language

• Language: English
• Title: Analysis of existing methods for electrical voltage frequency measurement in electric power systems

Abstract

Operating a complex system such as the power grid consists of many crucial components, one of which is frequency measurement. The existing methods of frequency measurement can be described with the help of various mathematical methods. In this work I have focused on three: sine-fitting, zero-root crossing, and Short-Time Fourier transform (STFT). To test them, I first created an input, an electrical voltage signal, with a predefined frequency. In the next step I focused on different parameters, such as harmonic distortion and window length, and their impact on measurement accuracy. Whether they would pass as acceptable if put into practice, additional tests are needed. These are defined in a standard IEEE-C37.118.1-2011, in which there are various tests for stationary and dynamic conditions. I have conducted three of them and the results are as followed. All of them have successfully passes at least one test for dynamic conditions, but none for stationary conditions. In demands, regarding the speed of measurements in real-time, they all failed due to sensitivity to convergence and both parameters, mentioned above. Following this revelation, to get acceptable results of frequency measurement in real-time, additional methods would be needed.

• Keywords: Frequency measurement, IEEE-C37.118.1-2011, sine-fitting, zero-root crossing, STFT