Adaptive Full-Order Observer With High-Frequency Signal Injection for Synchronous Reluctance Motor Drives

A back electromotive force-based position observer for motion-sensorless synchronous reluctance motor (SyRM) drives is augmented with high-frequency signal-injection method for improved low-speed operation. Previously proposed observer structure is further improved to account for the cross saturation in the motor. The combined observer is experimentally evaluated using a 6.7-kW SyRM drive in low-speed operation and under various load conditions. The resulting position error at low speeds and standstill is small.Peer reviewe

Signal-Injection-Assisted Full-Order Observer With Parameter Adaptation for Synchronous Reluctance Motor Drives

A back-EMF-based position observer for motion-sensorless synchronous reluctance motor (SyRM) drives is augmented with parameter-adaptation laws for improved operation at all speeds, including standstill. The augmented observer is theoretically analyzed under various operation conditions. The analysis indicates that the stator-resistance adaptation should be enabled only at low speeds, the d-axis inductance adaptation should be enabled only at medium and high speeds near no load, and the q-axis inductance adaptation should be enabled only at high speeds under high load. The augmented observer is experimentally evaluated using a 6.7-kW SyRM drive.Peer reviewe

Modeling of Saturation Due to Main and Leakage Flux Interaction in Induction Machines

Saturation due to the main flux and rotor leakage flux interaction appears in induction machines, especially if the rotor slots are skewed or closed. Conventional saturation models used in connection with dynamic equivalent-circuit models do not take this phenomenon into account. In this paper, explicit functions for modeling this mutual saturation are proposed. These functions are physically reasonable, they are easy to fit, and the number of their parameters is small. The proposed functions can be used in real-time applications and in computer simulations if high accuracy and physical consistency are preferable. The model fits well to the data obtained from finite element analysis or experimental data of a 2.2-kW motor. The model predicts the stator current with good accuracy both in steady state and in transients.Peer reviewe

Modeling of Mutual Saturation in Induction Machines

Mutual saturation between the main flux and the rotor leakage flux appears in induction machines, especially if the rotor slots are skewed or closed. Conventional saturation models used in connection with dynamic equivalent-circuit models do not take this phenomenon into account. In this paper, explicit functions for modeling the mutual saturation are proposed. The proposed functions are physically reasonable, they are easy to fit, and the number of their parameters is small. The proposed functions can be used in real-time applications and in computer simulations where high accuracy and physical consistency are preferable. The model fits well to the data obtained from finite element analysis or experimental data of a 2.2-kW motor.Peer reviewe

Minimizing losses of a synchronous reluctance motor drive taking into account core losses and magnetic saturation

This paper proposes a loss-minimizing controller for synchronous reluctance motor drives. The proposed method takes core losses and magnetic saturation effects into account. The core-loss model consists of hysteresis losses and eddy-current losses. Magnetic saturation is modeled using two-dimensional power functions considering cross coupling between the d- and q-axes. The efficiency optimal d-axis current is calculated offline using the loss model and motor parameters. Instead of generating a look-up table, an approximate function was fitted to the loss-minimizing results. The loss-minimizing method is applied in a motion-sensorless drive and the results are validated by measurements.Peer reviewe

A comparison of an adaptive full-order observer and a reduced-order observer for synchronous reluctance motor drives

Two back-EMF-based position observers are compared for motion-sensorless synchronous reluctance motor drives. The reduced-order observer is of the second order, and the adaptive full-order observer is of the fourth order. The proposed design rules guarantee the stability of the adaptive full-order observer, if the parameter estimates are accurate. The observers are experimentally evaluated using a 6.7-kW synchronous reluctance motor drive in low-speed operation and under parameter errors. The gain selection of the second-order observer is easier, but the adaptive full-order observer is more robust against parameter variations and spatial harmonics.Peer reviewe

Analysis and design of a position observer with resistance adaptation for synchronous reluctance motor drives

A back-EMF-based reduced-order position observer with stator-resistance adaptation is analyzed for motion-sensorless synchronous reluctance motor drives. Analytical equations for steady-state estimation errors and stability conditions are derived (with and without resistance adaptation), taking into account errors in the parameter estimates. The effect of the observer gain on the noise reduction is studied by means of eigenvector analysis. A robust gain selection is proposed, which maximizes the allowed uncertainties in the parameter estimates. The proposed observer design is experimentally evaluated using a 6.7-kW synchronous reluctance motor drive; stable operation is demonstrated at low speeds under various parameter errors.Peer reviewe

Inclusion of magnetic saturation in dynamic models of synchronous reluctance motors

This paper deals with the modeling of the magnetic saturation in synchronous reluctance motors (SyRMs). The saturation is modeled by means of analytical expressions, which can be easily embedded in dynamic equivalent-circuit models. A modified power function—proposed in this paper—can take into account the cross saturation between the orthogonal windings, it is physically consistent, and the number of its parameters is small. The function can be used in real-time control applications and in computer simulations. The model fits well to the experimentally measured inductances of a 6.7-kW SyRM. As an application example, the proposed saturation model was implemented in a full-order observer of a motion-sensorless drive, and experimental results are shown.Peer reviewe

Analysis and Design of a Position Observer With Resistance Adaptation for Synchronous Reluctance Motor Drives

A back-electromotive-force-based reduced-order position observer with stator-resistance adaptation is analyzed for motion-sensorless synchronous reluctance motor (SyRM) drives. Analytical equations for steady-state estimation errors and stability conditions are derived (with and without resistance adaptation), taking into account errors in the parameter estimates. The effect of the observer gain on the noise reduction is studied by means of eigenvector analysis. A robust gain selection is proposed, which maximizes the allowed uncertainties in the parameter estimates. The proposed observer design is experimentally evaluated using a 6.7-kW SyRM drive; stable operation is demonstrated at low speeds under various parameter errors.Peer reviewe

Analysis and design of a position observer with stator-resistance adaptation for PMSM drives

This paper deals with reduced-order observers with stator-resistance adaptation for motion-sensorless permanent-magnet synchronous motor drives. An analytical solution for the stabilizing observer gain and stability conditions for the stator-resistance adaptation are derived. The proposed observer design is experimentally tested using a 2.2-kW motor drive; stable operation at very low speeds under different loading conditions is demonstrated.Peer reviewe