An analysis of the benefits of signal injection for low-speed sensorless control of induction motors

We analyze why low-speed sensorless control of the IM is intrinsically difficult, and what is gained by signal injection. The explanation relies on the control-theoretic concept of observability applied to a general model of the saturated IM. We show that the IM is not observable when the stator speed is zero in the absence of signal injection, but that observability is restored thanks to signal injection and magnetic saturation. The analysis also reveals that existing sensorless algorithms based on signal injection may perform poorly for some IMs under particular operating conditions. The approach is illustrated by simulations and experimental data

Sensorless variable speed single-phase induction motor drive system based on direct rotor flux orientation

The single-phase induction motor (SPIM) is one of the electrical machines more used in the World, and can be found in several fractional and sub-fractional horsepower applications in houses, offices, shoppings, farms, and industries. The introduction of more sophisticated applications has required the use of variable speed drives for SPIM, where the adoption of sensorless techniques is the more reasonable option for speed control due to the low cost of this electrical machine. A proposal for sensorless variable speed SPIM drive based on direct rotor field orientation techniques is presented in this paper. None transformation is used in order to eliminate the asymmetry of the stator windings of the SPIM. The rotor speed is estimated from an flux observer, which is based on two independent linear feedback control systems. The speed and flux estimatives are used in two control loop based on PID regulators, which determine the voltages to be applied to the SPIM windings by a three-legs VSI inverter. Using computer simulations, two situations are considered in order to demonstrate the satisfactory performance of the proposed sensorless speed control for SPIM drives: variations on rotor speed reference and the application of mechanical load

Observability analysis of sensorless synchronous machine drives

This paper studies the local observability of synchronous machines using a unified approach. Recently, motion sensorless control of electrical drives has gained high interest. The main challenge for such a technology is the poor performance in some operation conditions. One interesting theory that helps understanding the origin of this problem is the observability analysis of nonlinear systems. In this paper, the observability of the wound-rotor synchronous machine is studied. The results are extended to other synchronous machines, adopting a unified analysis. Furthermore, a high-frequency injection-based technique is proposed to enhance the sensorless operation of the wound-rotor synchronous machine at standstill

Model Reference Adaptive System (MRAS) Based Speed Sensorless Vector Control of Induction Motor Drive

No Abstrac

High performance of sensorless sliding mode control of doubly fed induction motor associated with two multilevel inverters fed by VFDPC_SVM rectifier

A robust sensorless control based on the sliding-mode observer applied to a doubly fed induction motor associated with two three-level NPC-type voltage inverters fed by PWM rectifier with constant switching frequency and without line voltage sensors, is presented in this paper.  Also, we present an improved direct power control with virtual flux (VFDPC_SVM) for the control of three phase rectifier. Simulation results of this proposed system were analyzed using MATLAB environment

A review of saliency-based sensorless control methods for alternating current machines

Operation of model-based sensorless control of Alternating Current machines at low and zero speeds is unreliable and can fail. To overcome the limitations of sensorless control at low speeds, several alternative techniques have been developed to estimate speed and position. These are mainly based on detecting machine saliencies by measuring the response of the current to some form of voltage injection. This paper discusses injection methods, machine saliencies, and techniques used to extract speed and position that are applicable to both induction machines and permanent magnet synchronous motors.peer-reviewe

Current Controller for Low Frequency Signal Injection and Rotor Flux Position Tracking at Low Speeds

International audienceRotor flux spatial position can be tracked in an ac machine even at low or zero stator frequency if a low-frequency harmonic current signal is injected into its stator. The harmonic current injection is source of the rotor speed perturbations which induce voltage oscillations in the stator winding at the injected frequency. By analyzing the stator winding voltage response, it is possible to detect the rotor flux position regardless of the stator frequency. This paper presents a stator current controller that is suitable for imposing rotating or pulsating harmonic current injection and a method for tracking the rotor flux position in either induction machines (IMs) or permanent-magnet synchronous machines (PMSMs). The controller contains, in addition to the standard fundamental-frequency-based synchronous reference frame (SRF) current controller, two sets of harmonic current integral controllers placed in respective harmonic SRFs. Such an extended current controller simultaneously performs two important tasks: controlled harmonic current injection with zero steady-state error and separation of particular spectral components in the stator voltage (spectral/sequence decomposition) which contain the rotor flux position information. The theoretical analysis presented, based on perturbation theory and averaging techniques, gives general expressions which link the rotor flux position error in IM and PMSM to the harmonic current controller outputs. Two special cases with the rotational and pulsating harmonic current injections are considered in more detail. The validity of the theoretical analysis and the feasibility of the sensorless rotor flux position detection are experimentally verified

Traction control in electric vehicles

Tese de Mestrado Integrado. Engenharia Electrotécnica e de Computadores. Área de Especialização de Automação. Faculdade de Engenharia. Universidade do Porto. 201

Sensorless Direct Field-Oriented Control of Three-Phase Induction Motor Drives for Low-Cost Applications

A sensorless direct rotor field-oriented control (SDRFOC) scheme of three-phase induction motors for low-cost applications is presented in this paper. The SDRFOC algorithm is based on a sensorless closed-loop rotor flux observer whose main advantages are simplicity and robustness to motor parameter detuning. The whole algorithm has been developed and implemented on a low-cost fixed-point digital signal processor controller. Experimental results are presented for a 0.5-kW induction motor drive for a primary vacuum pump used in industry applications