Critical evaluation and application of position sensorless control techniques for reluctance synchronous machines

[摘要] ENGLISH ABSTRACT: The position sensorless controllability of the reluctance synchronous machine (RSM) is investigated inthis thesis with the focus on industry applications where variable and dynamic torque is required fromstartup up to rated speed. Two low speed as well as one medium to high speed position sensorless control(PSC) method for RSMs are investigated. These methods are extended to operate in the entire ratedspeed region with a hybrid PSC structure that makes use of phase locked-loop synchronisation and ahysteresis changeover method.It is shown in this thesis that PSC of the lateral rib rotor RSM is not possible from zero up to ± 0.2 p.ucurrent. It is shown through finite element (FE) simulations that PSC of the ideal rotor RSM however,is possible at zero reference current. A novel construction method is used to build two ideal rotor RSMs.Measured flux linkage curve results of the ideal rotor RSMs correlate well with simulation results and itis shown that the electrical angle of the machine can be tracked successfully at zero reference current.The FE simulation package is used to compare the saliency of the RSM on a per-unit scale to threetypes of field intensified permanent magnet (FI-PM) synchronous machines and a field weakening interiorpermanent magnet synchronous machine. It is shown that the saliency of the RSM is larger than that ofthe investigated PM machines from zero up to rated load. It is thus concluded that the RSM is well suitedto saliency-based PSC (SB-PSC) methods, which are used to control synchronous machines at startupand low speeds.The hybrid PSC methods developed in this thesis, are tested and evaluated on three proposed industryapplications. The first is a reluctance synchronous wind generator with an inverter output LC filter. TheLC filter allows long cables to be used and reduces the voltage stress on the stator windings of the machine.The combination of the LC filter and hybrid PSC method allows the power electronics and controller tobe stationed in the base of the turbine tower. A new stator quantity estimation method is derived to omitthe need of current and voltage sensors on the machine side of the LC filter. Good maximum power pointtracking laboratory results are shown with the high frequency injection-assisted hybrid PSC method.The second application investigated is a position sensorless controlled variable gear electric vehicle(EV) RSM drive. Simulation and measured results show good torque capabilities of the position sensorlesscontrolled EV RSM. It is shown through simulation results that the fundamental current harmonic isdominant in the demodulation scheme of the high frequency injection position sensorless control (HFIPSC)method due to the high current rating of the proposed RSM. The HFI-PSC method is extended toreduce the effect of the fundamental current harmonic in the demodulation scheme without adding anyadditional filters.The final investigated application is a novel mine scraper winch, which uses two position sensorlesscontrolled RSMs to retrieve ore from the blast site underground. The new design improves on the safety,efficiency and durability of the current scraper winch design. Measured results show that the positionsensorless controlled winch RSM is able to deliver rated startup torque with both investigated SB-PSCmethods. Finally an automation method is implemented and tested to limited the applied force on thescraper and automatically free itself when stuck.

[发布机构] Stellenbosch University