Rotor Position Estimation Scheme Research Articles

Continuous Rotor Position Estimation for Flux Modulated Doubly Salient Reluctance Motor Drives Based on Back EMF Harmonics

DC-biased sinusoidal current excited flux modulated doubly-salient reluctance motor (FMDRM) drives are developed to reduce the torque ripple and vibration of doubly-salient reluctance motors (DRMs). Conventionally, because of the discontinuous quasi-square current excitation, the rotor position of DRMs is estimated by the combination of piecewise estimation of phase angle information for each phase, where the continuous position estimation for the novel FMDRM drives cannot be realized. To solve this issue, this paper proposes a continuous rotor position estimation strategy for FMDRM drives based on back electromotive force (back-EMF) harmonic characteristics. Firstly, the back-EMF harmonics caused by the rotor saliency and their relationship with the rotor position are analyzed in detail. Then, the corresponding harmonic current regulator and quadrature signal generator are investigated to achieve harmonic current suppression and obtain the quadrature harmonic back-EMF components in the rotating reference frame for rotor position estimation simultaneously. Furthermore, a virtual-inductance-based method is developed to calibrate the phase angle offset between the estimated and actual rotor positions. With the proposed scheme, accurate continuous rotor position estimation can be achieved without any additional hardware. Experimental validations are presented on a three-phase 12/8 FMDRM prototype to verify the accuracy of the proposed rotor position estimation scheme.

Two-Step Rotor Position Estimation Method for Doubly Salient Electromagnetic Starter-Generator Over Zero and Low Speeds Range

Doubly salient electromagnetic machine (DSEM) can constitute a novel aero starter-generator (SG) system, and position sensorless control of DSEM is a key technology to improve system reliability and power density. This article proposes a novel two-step rotor position estimation scheme for doubly salient electromagnetic starter-generator (DSESG) over zero and low speeds range. Based on the corresponding relation between the minimal phase self-inductance and rotor sector, the rotor position estimation is made by searching the minimal phase self-inductance, which is carried out through two comparing steps of two proper phase self-inductances, and each comparing step is implemented according to the magnitude relation of two parallel-connected phase currents. Then, the selection method of the diagnostic pulsewidth is studied by overall considering the rotor position estimation precision and the low speeds sensorless startup performance. Furthermore, the possible estimation error introduced by the limited resolution of the practical current sensor is analyzed, and a quasi-three-phase six-state conduction mode is put forward as the compensation strategy to guarantee the low speeds sensorless startup performance, in which three boundary sectors with different conduction states are added. Finally, the experiments on a 12/8-pole DSESG validate the correctness and feasibility of the proposed strategies.

A Novel Strategy for Sensorless Control of IPMSM with Error Compensation Based on Rotating High Frequency Carrier Signal Injection

In the applications of rail transit and electric vehicles, sensorless control of interior permanent magnet synchronous motor (IPMSM) usually uses high frequency (HF) signal injection in low speed or zero speed. Rotating HF signal injection based on the stationary reference frame can identify the rotor position, but its accuracy is easily affected by various nonlinearities of the control system and stator resistance. In this paper, the causes of rotor position estimation deviation are analyzed and deduced in detail. It is proposed that the rotor position estimation deviation can be divided into high frequency phase deviation (HFPD) and stator resistance phase deviation. On the basis of these analyses, a novel sensorless rotor position estimation strategy for IPMSM is proposed. This strategy can theoretically eliminate the HF phase deviation caused by the nonlinearity of the control system and reduce the phase deviation caused by the stator resistance. Although the factors that cause the estimation deviation of rotor position may change with the time and the operation status of the motor, the proposed strategy has the characteristics of online calculation and real-time compensation, which can improve the accuracy of the estimated rotor position. In addition, this paper provides a detailed theoretical derivation of resolving rotor position considering stator resistance and HF phase deviation. Finally, the result analysis on an IPMSM demonstrate the correctness of the theoretical analysis and the effectiveness of the strategy.

Sensorless Control of Permanent Magnet Bearingless Synchronous Motors Using Online Parameter Identification

A novel rotor position estimation scheme using online parameter identification based on grey model is suggested in this paper, which will meet the need of sensorless control for permanent magnetism bearingless synchronous motor (PMBSM). The scheme is computationally simple and does not rely on the motor parameters. And then, the sensorless vector control system of PMBSM is set up based on this position estimation approach. The results of simulation and experiments show that the proposed method is capable of precisely estimating the rotor space position and is able to achieve stable suspension under the bigger disturbance.

Rotor position estimation scheme with harmonic ripple attenuation for sensorless controlled permanent magnet synchronous motors

To achieve high-performance sensorless control of permanent magnet motors with non-sinusoidal back electromotive force (EMF), an improved sliding mode observer (SMO) adopting synchronous rotating low-pass filter (SRLPF) is proposed. The SRLPF is utilised to reduce the back-EMF harmonics and extract the fundamental component. Different from the traditional rotor position observer, the proposed observer can calculate the rotor position with the back-EMF fundamental component. Owing to the decrease in the influence of non-sinusoidal back-EMF, the estimated rotor position harmonic ripple error can be greatly reduced. Then, the high estimated accuracy and excellent sensorless control performance can be obtained. In addition, the proposed strategy is easy for implementation. With the comparison between the traditional SMO and the proposed observer, the experiments of the system steady-state error, the speed tracking performance, and the disturbance rejection ability in the speed range from 60 r/min to the rated speed 750 r/min are presented. The validity of the proposed method is conformed.

Unbalanced Phase Inductance Adaptable Rotor Position Sensorless Scheme for Switched Reluctance Motor

Factors such as machining precision and electrical failures may lead to phase inductance unbalance in a switched reluctance motor (SRM). Under unbalanced inductance conditions, most of the traditional sensorless schemes would be invalid if no modification is applied. To prove the existence of this problem, an inductance partition based rotor position estimation scheme under balanced and unbalanced inductance conditions are investigated and compared for identifying the position estimation error characteristics. The theoretical analysis shows that the position estimation error is highly dependent on the degree of the inductance unbalance. To maintain stable sensorless operation under unbalanced condition, a modified full-cycle inductance partition based rotor position estimation scheme with unbalanced inductance adaptive capability is proposed in this paper. In this method, the linear region of each phase full-cycle inductance is relocated with the predetermined inductance thresholds. By locating the linear inductance regions, the rotor position can be estimated from a simple partition linear model between the rotor position and the phase inductance. This method is easy for implementation without additional hardware and complex calculation. Experiments are performed on a 12/8 structure SRM and the results verify the effectiveness of the proposed method.

Back‐EMF‐based sensorless control system of hybrid SRM for high‐speed operation

Based on the back electromotive force (back-EMF) detection, a novel rotor position estimation strategy with adjustable turn on/off angle is proposed for the high-speed hybrid switched reluctance motor (SRM). The minimum back-EMF position is captured in every electrical cycle for rotor position estimation. The current comparator is employed to send out a turn-off signal for phase winding when the maximum inductance position is detected in the first electrical cycle. By providing sufficient current rise time to the phase winding, the proposed sensorless control system enables the motor to run in high-speed application. Besides the straightforward estimation principle, the proposed strategy has the implemental feasibility by eliminating extensive calculations and complicated look-up tables. The experimental results of a prototype are demonstrated to verify the proposed sensorless control system.

Rotor position estimation for single- and dual-three-phase permanent magnet synchronous machines based on third harmonic back-EMF under imbalanced situation

In this paper, an improved rotor position estimation strategy based on third harmonic back-EMF for single- and dual-three-phase permanent magnet synchronous machines (PMSMs) under imbalanced situation is proposed. Due to the imbalanced machine impedance, back-EMF or sensing resistor network, the measured triplen harmonic back-EMF will contain certain fundamental component distortion which may severely deteriorate the performance of rotor position estimation. With the aid of the fundamental component compensator, this distortion can be significantly compensated, and the rotor position estimation error can be minimized considerably. The proposed strategy has been implemented on a dSPACE platform with a prototype of dual-three-phase PMSM with serious imbalanced parameters, and operate at single- and dual-three-phase conditions. The experimental results prove that the proposed strategy can significantly improve the steady-state and dynamic performance of rotor position estimation under imbalanced situation.

Sensorless Speed Control with Initial Rotor Position Estimation for Surface Mounted Permanent Magnet Synchronous Motor Drive in Electric Vehicles

The accurate information of the initial rotor position is very critical for successful starting of the Surface-mounted Permanent Magnet Synchronous Motor (SPMSM). In order to solve the problems of low accuracy and unreliability in the conventional estimation strategy, in this paper, an improved initial rotor position estimation strategy without any position sensor for SPMSM at standstill is proposed based on rectangular pulse voltage injection. In the work, when the second series of pulse voltages were applied. By the ways of strengthening the effect of weakening or strengthening magnetic fields and increasing the difference between each current of the vector. The improved strategy enhanced reliability and raised the initial position estimation accuracy from 7.5° to 1.875°. The improved strategy does not need any additional hardware. Experimental results demonstrate the validity and usefulness of the improved strategy.

Robust Initial Rotor Position Estimation of Permanent-Magnet Brushless AC Machines With Carrier-Signal-Injection-Based Sensorless Control

In sensorless control of permanent-magnet brushless ac machines, it is necessary to identify the initial rotor position prior to start-up of the machine. Although saliency-tracking-based sensorless techniques are proven to be a good candidate to estimate the initial rotor position in sensorless control, magnetic polarity identification is another important issue. Since the machine saliency undergoes two cycles in a single electrical period, the estimated position information based on machine saliency has an angle ambiguity of π. With the aid of magnetic saturation effect, this paper proposes a robust initial rotor position estimation scheme, which utilizes both d- and q-axis carrier currents, instead of only the q-axis carrier current, in conventional pulsating-carrier-signal-injection-based sensorless control algorithm. Integrated with conventional carrier-signal-injection-based sensorless algorithm, the proposed technique could obtain the initial rotor position for both standstill and free-running rotors. Finally, the experimental results confirm the effectiveness and robustness of the proposed method.

Rotor position estimator for stator flux-oriented sensorless control of slip ring induction machine

A rotor position estimation scheme for stator flux-oriented speed sensorless control of slip ring induction machine (SRIM) is presented in this paper. Position of the rotor is estimated by integrating the rotor back-electromotive force. The problem of DC drift during integration is eliminated using an error-decaying mechanism in the estimator. This estimation scheme reduces the propagation of noise in the sensed current to the estimated rotor side unit vectors. This scheme also eliminates the need for differentiating the unit vectors for estimating slip frequency. The proposed scheme is simulated and experimentally verified.

Initial rotor position estimation and sensorless direct torque control of surface-mounted permanent magnet synchronous motors considering saturation saliency

For a practical direct torque-controlled (DTC) permanent magnet synchronous motor (PMSM) drive system, the information of the initial rotor position, which is usually obtained by a mechanical position sensor, is essential for starting under the full load. To avoid the disadvantages of using mechanical position sensors, great efforts have been made on the development of sensorless control schemes. An initial rotor position estimation strategy is presented for a DTC PMSM drive based on a nonlinear model of PMSM incorporating both structural and saturation saliencies. In the new scheme, specially designed high-voltage pulses are applied to amplify the saturation saliencies. The peak currents corresponding to the voltage pulses are used, in combination with the inductance patterns, to determine the d-axis position and the polarity of the rotor. The presented initial rotor position identification strategy has been implemented in a sensorless DTC drive for a surface-mounted PMSM. Experiments are conducted to confirm the effectiveness of the method and the performance of the drive system.

Indirect angle estimation in switched reluctance motor drive using fuzzy logic based motor model

In this paper, a novel rotor position estimation scheme is described that was developed to overcome the drawbacks of the previous sensorless techniques, which were proposed for switched reluctance (SR) motor drives. It is based on fuzzy-logic, and does not require complex mathematical models or large look up tables. The scheme was implemented by using a digital signal processor. The real-time experimental results given in this paper show that the position estimation method proposed can provide accurate and continual position data over a wide range of speeds (zero/low/high), and can also function accurately at different operating conditions (chopping/single pulse mode and steady state/transient operation).

Transducerless position and velocity estimation in induction and salient AC machines

This paper presents a viable transducerless rotor position and velocity estimation scheme for PWM inverter driven induction, synchronous, and reluctance machines with the capability of providing robust and accurate dynamic estimation independent of operating point, including zero and very high speeds, light and heavy loading. The injection of a balanced three-phase high frequency signal (500 to 2 kHz) generated by the inverter, followed by appropriate signal demodulation and processing combined with a closed-loop observer, enable the tracking of rotor magnetic saliencies from the machine terminals. Although rotor magnetic saliency is inherent within reluctance machines, and most synchronous machines, saliency in the induction machine is introduced via a modulation of the rotor slot leakage with minimal detrimental effects on the machine performance. Experimental verification for the induction machine is included.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>