Variable speed and torque control of a wind turbine system with assisted reluctance synchronous generator technology

Botha, Christoffel Daniel (2018-03)

Thesis (MEng)--Stellenbosch University, 2018.

Thesis

ENGLISH ABSTRACT: Small-scale wind turbines provide a viable alternative energy source for small farms, business and rural areas. The goal of such small-scale turbines is to provide electricity at the lowest cost possible. It is thus imperative that turbines capture the maximum volume of energy at the lowest cost and highest possible efficiency, while having a high reliability. Assuming a suitable turbine location and good blade design, two of the biggest factors in ensuring this goal include the choice of generators as well as the control of the turbine system. While the permanent magnet synchronous generator (PMSG) is a popular choice for small-scale wind turbines, its use of permanent magnet material increases the cost of the system. One of the alternatives to the PMSG that has received renewed interest during the last few years is the reluctance synchronous generator. This thesis focuses on the development and control of an assisted reluctance synchronous generator (ARSG) wind turbine system. The ARSG is an effort to help solve, at least partially, some of the disadvantages of the standard reluctance synchronous generator (RSG), e.g. the low power factor. A simple rotor design is proposed, with a cursory comparison given between different rotor slot shapes. The mathematical model of the ARSG is derived, which serves as the basis of the development and implementation of a non-linear current controller. A maximum torque per ampere (MTPA) strategy based on the finite element (FE) analysis of the machine is developed and implemented practically. To ensure that the turbine is operated at optimal efficiency, a standard tip speed ratio (TSR) controller is designed and implemented. This controller can operate at under and above rated wind speeds. The results of the practical tests show the feasibility of the use of the DC-bus link connection as well as the performance of the control systems.

AFRIKAANSE OPSOMMING: Kleinskaalse windturbines bied ’n lewensvatbare alternatiewe energiebron vir plase, besighede en landelike gebiede. Die doel van sulke turbines is om elektrisiteit teen so goedkoop as moontlik te voorsien. Dit is dus noodsaaklik dat die turbine ’n maksimum hoeveelheid energie omskakel teen die laagste koste en die hoogste doeltreffendheid moontlik, en met ’n hoë betroubaarheid. Veronderstel ’n geskikte plek is gekies en die turbine het ’n goeie lem ontwerp, is twee van die grootste faktore die keuse van generator sowel as die beheer van die turbine sisteem. Terwyl die permanente magneet sinchroon generator (PMSG) ’n gewilde keuse vir kleinskaalse windturbines is, verhoog hul gebruik van permanente magneet materiaal die koste van die stelsel. Een van die alternatiewe vir die PMSG wat die afgelope paar jaar hernieude belangstelling ontvang het, is die reluktansie sinchroonmasjien. Hierdie tesis fokus op die ontwikkeling en beheer van ’n windturbine sisteem wat gebruik maak van ondersteunde reluktansie sinchroonmasjien tegnologie (ARSG). Die ARSG is ’n poging om, ten minste gedeeltelik, sommige van die nadele van die standaard reluktansie masjien op te los, bv. die lae arbeidsfaktor. ’n Eenvoudige rotorontwerp word voorgestel, met ’n vlugtige vergelyking wat tussen verskillende rotor-gleufvorme gegee word. Die wiskundige model van die ARSG is afgelei, wat as die basis van die ontwikkeling en implementering van ’n nie-lineêre stroombeheerder dien. ’n Maksimum draaimoment per ampere (MTPA) strategie gebaseer op die eindige element (FE) analise van die masjien word prakties ontwikkel en geïmplementeer. Om te verseker dat die turbine teen optimale doeltreffendheid bedryf word, word ’n standaard spoedverhouding (TSR) beheerder ontwerp en geïmplementeer. Hierdie beheerders kan werk gedurende onder en bo nominale windsnelhede.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/103465
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