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Various functional candidates such as flux, backemf, reactive power etc. are used to form a model reference adaptive system (MRAS) to estimate speed of an induction motor (IM) drive. Of these, reactive power (Q) based controllers perform well at low speeds and are inherently independent of stator resistance. However, such configuration fails to provide stability in the regenerative mode. This paper proposes a new formulation of Q-based MRAS that is stable in all the four quadrants of operation. A detailed MATLAB/SIMULINK based simulation study is presented. Superior performance of the proposed controller is confirmed by prototype experimentation using an FPGA based controller in the laboratory.Index Terms-Variable speed drives, induction motors, vector control, sensorless control, model reference adaptive system, reactive power, field programmable gate arrays. NOMENCLATURE α, β stationary reference frame v * sα , v * sβ reference stator voltages in α, β reference frame v s stator voltage vector i sα , i sβ actual stator currents in α, β reference frame i s stator current vector d, q rotor flux reference frame v * sd , v * sq reference stator voltages in d,q reference frame v sd , v sq actual stator voltages in d,q reference frame i * sd , i * sq reference stator currents in d,q reference frame i sd , i sq actual stator currents in d,q reference frame ψ rd , ψ rq rotor flux in d,q reference frame ρ mr position of the rotor flux vector with respect to α-axis R s , R r stator and rotor resistances referred to stator L m magnetizing inductance referred to stator L s , L r stator and rotor inductances referred to stator τ r rotor time constant = L r /R r σ leakage factor = 1 − L 2 m LrLs ω r actual rotor speed (electrical) ω * r reference rotor speed ω r estimated rotor speed ω sl slip speed ω e synchronous speed Manuscript

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This article discusses the speed-sensorless vector-controlled SRM-drive. The use of position/speed sensors have few concerns related to it in terms of cost, reliability, and compactness, a few to mention. Therefore, it is necessary to have some estimation strategy which estimates the speed/position. Since the control of the machine is done in dq0-reference frame, so by utilising these dq0-variables a novel speed/position estimation technique i.e. 'P n-MRAS (Net-input-Power-based Model-Reference-Adaptive-System) speed-estimator' is developed for the vector-controlled SRM-drive. The speed-estimator implemented is simple, no look-up table is required and no external circuitry is required for injection of the diagnostic signal. Also, the estimator is free from differentiator and integrator terms. The proposed speed-estimator is stable in all the four quadrants of operation which is proved by performing the stability analysis. The estimator is dependent on two machine parameters (stator-resistance and amplitude of AC-component of self-inductance). The estimator is made robust to changes in stator-resistance by estimating the resistance online by proposed V 0-MRAS resistance-estimator. The drive has been extensively simulated in MATLAB/SIMULINK and results are also verified experimentally through a dSPACE-1104-based laboratory prototype.