Upravljanje istosmjernim ulaznim pretvaračem napajanim fotonaponskim modulom s ciljem maksimizacije proizvedene snage

doctoral thesis

• Title (english): Control of a dc-dc boost converter supplied by photovoltaic module for maximum power production
• Author: Tomislav Pavlović
• Mentor: Željko Ban (mentor)
• Committee member: Željko Ban (član povjerenstva)
• Granter: University of Zagreb; Faculty of Electrical Engineering and Computing; (Department of Control and Computer Engineering); Zagreb
• Defense date and country: 2014, Croatia
• Scientific / art field, discipline and subdiscipline: TECHNICAL SCIENCES; Electrical Engineering; Automation and Robotics
• Universal decimal classification (UDC): 621.3 - Electrical engineering

Abstract

U ovom radu obrađen je problem traženja maksimuma snage fotonaponskog modula u sustavu s istosmjernim uzlaznim pretvaračem s modulacijom po vršnoj vrijednosti struje zavojnice i baterijom na izlazu u uvjetima jednolikog osvjetljenja i djelomičnog zasjenjenja. U tu svrhu iskorišten je Nelder-Mead optimizacijski postupak, koji načelno radi u dva načina rada, u lokalnom i globalnom. Predloženi su koraci ograničavanja područja pretraživanja u globalnom načinu rada, te podešavanja parametara algoritma, s ciljem smanjenja broja iteracija, te time i gubitka snage. Da bi Nelder-Mead algoritam mogao raditi s malim vremenima uzorkovanja projektiran je podređeni regulator ulaznog napona pretvarača utemeljen na teoriji kliznih režima. U sintezi regulatora predloženo je modeliranje procesa linearnim modelom drugog reda s promjenjivim parametrima. Regulator ulaznog napona osigurava jednaku dinamiku prijelaznih pojava pri velikim promjenama referentnog iznosa ulaznog napona u različitim radnim uvjetima, za oblačnog i vedrog vremena, u području malih snaga i nominalne snage, te osigurava gotovo idealnu kompenzaciju utjecaja promjene dozračenosti, što je potvrđeno simulacijama i eksperimentom na realnom sustavu. Za slučajeve kad fotonaponski sustav mora sudjelovati u regulaciji napona trošila projektiran je regulator izlaznog napona pretvarača s kliznim režimom, čija je sinteza napravljena pod pretpostavkom pojednostavljenja modela procesa linearnim modelom prvog reda s promjenjivim parametrima. Regulator izlaznog napona osigurava jednaku dinamiku prijelaznih pojava pri promjeni referentne veličine u svim radnim točkama, te osigurava zadovoljavajuću kompenzaciju promjena izlaznog opterećenja. U svrhu ubrzanja računalnih simulacija kompleksnih sustava s pretvaračima, kao što su mikromreže, razvijen je pojednostavljeni usrednjeni nelinearni model realnog uzlaznog istosmjernog pretvarača s modulatorom po vršnoj vrijednosti struje zavojnice uz zanemarenje dinamike struje zavojnice. Razvijeni pojednostavljeni model omogućuje ubrzanje trajanja simulacija u programskom paketu Matlab/Simulink do jednog reda veličine u usporedbi s modelima punog reda. Predloženi usrednjeni model i rad svih sustava upravljanja eksperimentalno su provjereni na realnom sustavu.

Abstract (english)

The problem of maximum power point tracking (MPPT) in photovoltaic systems (PV) under uniform insolation conditions and during partial shading has been researched in this thesis. To this end, the new MPPT algorithm based on the Nelder-Mead optimization method is proposed. The system consists of PV module, DC-DC boost converter with peak current-mode modulation and battery. The proposed MPPT algorithm works in two search modes, local and global mode. The procedures for reduction of the search area and for tuning algorithm’s parameters in global search mode are proposed in order to reduce the number of iterations and consequently power losses. To allow the Nelder-Mead MPPT algorithm to work with fast sample times, the low-level input voltage controller based on the sliding mode theory is proposed. It is proposed to model the process with the second order linear model with uncertain parameters. The proposed input voltage controller provides equal dynamic behavior with respect to large input voltage set-point changes in the whole operating range of the converter, for clear and cloudy weather conditions, i.e. in nominal and low-power operating points. For situations where PV system is used outside the MPPT mode, i.e. in microgrid DC bus voltage control, the output voltage controller is proposed based on sliding mode theory. The controller is developed on the basis of the first order linear model with uncertain parameters. The proposed output voltage controller allows equal critically damped voltage transients with respect to reference changes in the whole operating range of the converter, and shows great robustness when output load changes. In order to reduce the simulation execution times of complex systems with power converters, like microgrids, the simplified nonlinear averaged model of the real boost DC-DC converter with peak current- mode modulation is proposed. The model reduction is based on the inductor current dynamics negligence. The simulation execution times with the proposed simplified model compared with the full-order model in Matlab/Simulink simulation environment are reduced up to one order of magnitude. The proposed averaged model and all proposed controllers are experimentally verified.

• Keywords: uzlazni istosmjerni pretvarač; usrednjeni model; modulacija po vršnoj vrijednosti struje zavojnice; klizni režim; algoritam traženja maksimuma snage fotonaponskog sustava; djelomično zasjenjenje fotonaponskih modula; Nelder-Mead algoritam
• Keywords (english): DC-DC boost converter; averaged model; peak current-mode control; sliding mode; maximum power point tracking in photovoltaic systems; partial shading of photovoltaic modules; Nelder-Mead algorithm
• Language: croatian
• URN:NBN: urn:nbn:hr:168:431199
• Study programme: Title: Electrical Engineering and Computing; Study programme type: university; Study level: postgraduate; Academic / professional title: Doktor znanosti elektrotehnike i računarstva (Doktor znanosti elektrotehnike i računarstva)
• Type of resource: Text
• Extent: 207 str. ; 30 cm.
• File origin: Born digital
• Access conditions: Closed access
• Created on: 2019-04-18 13:53:43