New alghorithms for estimation of phasors parameters in power systems with emphasis on fault current and dc components

U savremenom elektroenergetskom sistemu (EES-u), rad sistema za zaštitu, upravljanje, monitoring i kontrolu bazira se na preciznoj i brzoj estimaciji fazora osnovnog i viših harmonika, kao i estimaciji frekvencije signala napona i struje. Estimacija parametara fazora se vrši tehnikama za digitalnu obradu signala, pri čemu je Diskretna Furijeova Transformacija (DFT) najčešće korišćen algoritam za ovu namenu. DFT algoritam postiže odlične performanse kada procesirani signal sadrži samo osnovni i više harmonike i kada je usklađena frekvencija odabiranja sa frekvencijom sistema. Dva osnovna uzroka pogrešne estimacije fazora DFT metodom su: opadajuća jednosmerna komponenta u procesiranom signalu i neusklađenost frekvencije odabiranja sa frekvencijom procesiranog signala. Savremeni EES-i su veoma složeni zbog sve veće integracije obnovljivih izvora energije (OIE). Proizvodnja iz obnovljivih izvora je nekontrolabilna i nezavisna od potrošnje u EES-u. Ovo dovodi do debalansa između proizvodnje i potrošnje, što se direktno odražava na noseću frekvenciju sistema, odnosno dovodi do fluktuacije frekvencije signala napona i struje. Pored toga, integracija OIE dovodi do smanjenja ukupne inercije obrtnih masa u sistemu i time sistem postaje osetljiviji na debalanse u proizvodnji i potrošnji - promene frekvencije postaju brže. Rad savremenih zaštitnih uređaja i uređaja za sinhrono merenje fazora, baziran na digitalnoj obradi signala, zahteva praćenje harmonijskog sadržaja procesiranog signala i noseće frekvencije odnosno kontinualnu estimaciju ovih veličina. U disertaciji su predložena tri algoritma za estimaciju harmonijskih komponenti procesiranog signala i noseće frekvencije, pri čemu je osnovna ideja bazirana na prilagođavanju dužine prozora podataka stvarnoj frekvenciji sistema, čime se rešava problem devijacije frekvencije u numeričkim zaštitnim relejima. U slučaju kratkog spoja u EES-u opadajuća jednosmerna komponenta se superponira na već postojeću složenoperiodičnu komponentu strujnog signala, a merni strujni transformator prilagođava struju kratkog spoja sistemu za akviziciju. Tokom trajanja kratkog spoja, sekundarna struja strujnog transformatora sadrži dve opadajuće jednosmerne komponente, koje su po svojoj prirodi aperiodični signali širokog frekvencijskog spektra. Iz ovog razloga, opadajuće jednosmerne komponente zajedno sa višim harmonicima i šumom imaju veliki uticaj na tačnost i brzinu konvergencije algoritama za estimaciju fazora, odnosno na brzinu i pouzdanost rada zaštitnog sistema. U savremenim digitalnim i numeričkim relejima DFT se najčešće koristi za estimaciju fazora osnovnog i viših harmonika signala napona i struje, međutim, kao aperiodični signali, opadajuće jednosmerne komponente prouzrokuju veliku grešku pri estimaciji fazora DFT metodom. U disertaciji su predložena četiri nova algoritma za korekciju greške u DFT rezultatima koja nastaje kao posledica opadajućih jednosmernih komponenti.In the modern power system, the operation of the system for protection, management, monitoring and control is based on the precise and fast phasor estimation of the fundamental and higher harmonics, along with the estimation of the frequency of voltage and current signals. Estimation of phasor parameters is performed using digital signal processing techniques, with the Discrete Fourier Transform (DFT) being the most commonly used algorithm for this purpose. The DFT algorithm achieves excellent performance when the processed signal contains only the fundamental and higher harmonics and when the sampling frequency is matched to the system frequency. The two main causes of wrong phasor estimation by the DFT method are: the decaying DC component in the processed signal and mismatch between the sampling frequency and the frequency of the processed signal. Modern power systems are very complex due to the increasing integration of renewable energy sources (RES). Production from renewable sources is uncontrollable and independent of consumption in the power system. This leads to an imbalance between production and consumption, which directly influences the carrier frequency of the system, that is, it leads to fluctuations in the frequency of voltage and current signals. In addition, the integration of RES leads to a reduction of the total inertia of the rotating masses in the system and thus the system becomes more sensitive to imbalances in production and consumption, i.e., the frequency changes become faster. The operation of modern protective devices and devices for synchronous phasor metering, based on digital signal processing, requires monitoring of harmonics content and carrier frequency, i.e. continuous processing of signals harmonics and frequency estimation. Three algorithms for carrier frequency estimation are proposed in the dissertation, where the basic idea is based on adjusting the length of the data window to the actual frequency of the system, which solves the problem of frequency deviation in numerical protective relays. In the case of a fault in the power system, the decaying DC component is superimposed on the existing complex periodic component of the current signal, while the current measuring transformer adjusts the fault current to the acquisition system. During the fault, the secondary current of the current transformer contains two decaying DC components, which are, by their nature, aperiodic signals of a wide frequency spectrum. For this reason, decaying DC components, together with higher harmonics and noise, have a strong influence on the accuracy and convergence speed of algorithms for phasor estimation, that is, on the speed and reliability of the protection system. In modern digital and numerical relays, DFT is most often used to estimate the phasor of the fundamental and higher harmonics of voltage and current signals. However, as aperiodic signals, the decaying DC components cause a large error in phasor estimation when using the DFT method. This dissertation proposes four new algorithms for error correction in DFT results that arise as a consequence of decaying DC components

Semi-supervised Multi-modal Emotion Recognition with Cross-Modal Distribution Matching

Automatic emotion recognition is an active research topic with wide range of applications. Due to the high manual annotation cost and inevitable label ambiguity, the development of emotion recognition dataset is limited in both scale and quality. Therefore, one of the key challenges is how to build effective models with limited data resource. Previous works have explored different approaches to tackle this challenge including data enhancement, transfer learning, and semi-supervised learning etc. However, the weakness of these existing approaches includes such as training instability, large performance loss during transfer, or marginal improvement. In this work, we propose a novel semi-supervised multi-modal emotion recognition model based on cross-modality distribution matching, which leverages abundant unlabeled data to enhance the model training under the assumption that the inner emotional status is consistent at the utterance level across modalities. We conduct extensive experiments to evaluate the proposed model on two benchmark datasets, IEMOCAP and MELD. The experiment results prove that the proposed semi-supervised learning model can effectively utilize unlabeled data and combine multi-modalities to boost the emotion recognition performance, which outperforms other state-of-the-art approaches under the same condition. The proposed model also achieves competitive capacity compared with existing approaches which take advantage of additional auxiliary information such as speaker and interaction context.Comment: 10 pages, 5 figures, to be published on ACM Multimedia 202

New alghorithms for estimation of phasors parameters in power systems with emphasis on fault current and dc components

U savremenom elektroenergetskom sistemu (EES-u), rad sistema za zaštitu, upravljanje, monitoring i kontrolu bazira se na preciznoj i brzoj estimaciji fazora osnovnog i viših harmonika, kao i estimaciji frekvencije signala napona i struje. Estimacija parametara fazora se vrši tehnikama za digitalnu obradu signala, pri čemu je Diskretna Furijeova Transformacija (DFT) najčešće korišćen algoritam za ovu namenu. DFT algoritam postiže odlične performanse kada procesirani signal sadrži samo osnovni i više harmonike i kada je usklađena frekvencija odabiranja sa frekvencijom sistema. Dva osnovna uzroka pogrešne estimacije fazora DFT metodom su: opadajuća jednosmerna komponenta u procesiranom signalu i neusklađenost frekvencije odabiranja sa frekvencijom procesiranog signala. Savremeni EES-i su veoma složeni zbog sve veće integracije obnovljivih izvora energije (OIE). Proizvodnja iz obnovljivih izvora je nekontrolabilna i nezavisna od potrošnje u EES-u. Ovo dovodi do debalansa između proizvodnje i potrošnje, što se direktno odražava na noseću frekvenciju sistema, odnosno dovodi do fluktuacije frekvencije signala napona i struje. Pored toga, integracija OIE dovodi do smanjenja ukupne inercije obrtnih masa u sistemu i time sistem postaje osetljiviji na debalanse u proizvodnji i potrošnji - promene frekvencije postaju brže. Rad savremenih zaštitnih uređaja i uređaja za sinhrono merenje fazora, baziran na digitalnoj obradi signala, zahteva praćenje harmonijskog sadržaja procesiranog signala i noseće frekvencije odnosno kontinualnu estimaciju ovih veličina. U disertaciji su predložena tri algoritma za estimaciju harmonijskih komponenti procesiranog signala i noseće frekvencije, pri čemu je osnovna ideja bazirana na prilagođavanju dužine prozora podataka stvarnoj frekvenciji sistema, čime se rešava problem devijacije frekvencije u numeričkim zaštitnim relejima. U slučaju kratkog spoja u EES-u opadajuća jednosmerna komponenta se superponira na već postojeću složenoperiodičnu komponentu strujnog signala, a merni strujni transformator prilagođava struju kratkog spoja sistemu za akviziciju. Tokom trajanja kratkog spoja, sekundarna struja strujnog transformatora sadrži dve opadajuće jednosmerne komponente, koje su po svojoj prirodi aperiodični signali širokog frekvencijskog spektra. Iz ovog razloga, opadajuće jednosmerne komponente zajedno sa višim harmonicima i šumom imaju veliki uticaj na tačnost i brzinu konvergencije algoritama za estimaciju fazora, odnosno na brzinu i pouzdanost rada zaštitnog sistema. U savremenim digitalnim i numeričkim relejima DFT se najčešće koristi za estimaciju fazora osnovnog i viših harmonika signala napona i struje, međutim, kao aperiodični signali, opadajuće jednosmerne komponente prouzrokuju veliku grešku pri estimaciji fazora DFT metodom. U disertaciji su predložena četiri nova algoritma za korekciju greške u DFT rezultatima koja nastaje kao posledica opadajućih jednosmernih komponenti.In the modern power system, the operation of the system for protection, management, monitoring and control is based on the precise and fast phasor estimation of the fundamental and higher harmonics, along with the estimation of the frequency of voltage and current signals. Estimation of phasor parameters is performed using digital signal processing techniques, with the Discrete Fourier Transform (DFT) being the most commonly used algorithm for this purpose. The DFT algorithm achieves excellent performance when the processed signal contains only the fundamental and higher harmonics and when the sampling frequency is matched to the system frequency. The two main causes of wrong phasor estimation by the DFT method are: the decaying DC component in the processed signal and mismatch between the sampling frequency and the frequency of the processed signal. Modern power systems are very complex due to the increasing integration of renewable energy sources (RES). Production from renewable sources is uncontrollable and independent of consumption in the power system. This leads to an imbalance between production and consumption, which directly influences the carrier frequency of the system, that is, it leads to fluctuations in the frequency of voltage and current signals. In addition, the integration of RES leads to a reduction of the total inertia of the rotating masses in the system and thus the system becomes more sensitive to imbalances in production and consumption, i.e., the frequency changes become faster. The operation of modern protective devices and devices for synchronous phasor metering, based on digital signal processing, requires monitoring of harmonics content and carrier frequency, i.e. continuous processing of signals harmonics and frequency estimation. Three algorithms for carrier frequency estimation are proposed in the dissertation, where the basic idea is based on adjusting the length of the data window to the actual frequency of the system, which solves the problem of frequency deviation in numerical protective relays. In the case of a fault in the power system, the decaying DC component is superimposed on the existing complex periodic component of the current signal, while the current measuring transformer adjusts the fault current to the acquisition system. During the fault, the secondary current of the current transformer contains two decaying DC components, which are, by their nature, aperiodic signals of a wide frequency spectrum. For this reason, decaying DC components, together with higher harmonics and noise, have a strong influence on the accuracy and convergence speed of algorithms for phasor estimation, that is, on the speed and reliability of the protection system. In modern digital and numerical relays, DFT is most often used to estimate the phasor of the fundamental and higher harmonics of voltage and current signals. However, as aperiodic signals, the decaying DC components cause a large error in phasor estimation when using the DFT method. This dissertation proposes four new algorithms for error correction in DFT results that arise as a consequence of decaying DC components