Jihoon Jang

Sensorless drive of surface-mounted permanent-magnet motor by high-frequency signal injection based on magnetic saliency

This paper presents a new sensorless control scheme of a surface-mounted permanent-magnet (SMPM) motor using high-frequency voltage signal injection method based on the high-frequency impedance difference. In the SMPM motor, due to the flux of the permanent magnet, the stator core around the q-axis winding is saturated. This makes the magnetic saliency in the motor. This magnetic saliency has the information about the rotor position. The high-frequency voltage signal is injected into the motor in order to detect the magnetic saliency and estimate the rotor position. In this paper, the relationship between the high-frequency voltages and high-frequency currents is developed using the voltage equations at the high frequency, and the high-frequency impedance characteristics are analyzed experimentally under various conditions. The proposed sensorless control scheme makes it possible to drive the SMPM motor in the low-speed region including zero speed, even under heavy load conditions. The experimental results verify the performance of the proposed sensorless algorithm.

Analysis of permanent-magnet machine for sensorless control based on high-frequency signal injection

This paper presents the analysis of a surface-mounted permanent-magnet (SMPM) machine for the sensorless control scheme based on the high-frequency fluctuating voltage signal injection method. A simplified high-frequency model of an SMPM machine in the estimated rotor reference frame is developed and a sensorless rotor position and speed estimation algorithm is described. To support this, the high-frequency impedances of an SMPM machine are analyzed by finite-element analysis (FEA) and compared with measurement results using a pulsewidth-modulation (PWM) inverter system under various injection conditions. The results of the FEA and measurements are coincident with each other with some errors due to the nonlinear behavior of the PWM inverter and the SMPM machine. The analysis results give physical insights into selecting the injection conditions for sensorless operation of the SMPM machine even though adjustments considering nonlinear behaviors of PWM inverters are required in the actual operation for the desired performance. The experimental results of speed and position control using a commercial SMPM machine are presented based on the analysis of the SMPM machine for the sensorless control algorithm.

Comparison of PM Motor Structures and Sensorless Control Techniques for Zero-Speed Rotor Position Detection

The rotor position of a synchronous permanent magnet (PM) motor can be detected by means of the injection of a high-frequency stator voltage superimposed to the fundamental component. Thanks to the rotor anisotropy, the corresponding high-frequency current is modulated and used to determine the rotor position. Two techniques are considered: the first one adopts a pulsating voltage vector in the estimated synchronous reference frame, while the second one adopts a rotating voltage vector. These techniques are effective at zero and at low motor speed. The accuracy of the rotor position detection depends strictly on the rotor saliency, that is, on the geometry of the PM rotor. In fact both saturation and d-and q-axis cross-coupling have a heavy influence on the correct rotor position detection. The aim of this paper is to compare the two sensorless control techniques, together with two rotor geometries, that is, IPM and inset rotor. In order to highlight the effectiveness of the sensorless technique, the tests are carried out at various operating conditions. It is found that the effectiveness of the sensorless rotor position detection strongly depends on the PM rotor geometry. Conversely, the choice of the sensorless control technique affects slightly the rotor position detection.

Advantages of inset PM machines for zero-speed sensorless position detection

The aim of this paper is to analyze the behavior of a sensorless control system based on a high-frequency signal injection combined with an inset permanent-magnet (PM) motor. The rotor position of a synchronous PM motor with anisotropic rotor can be detected by the control system which superimposes a high-frequency signal to the fundamental stator voltage. The corresponding high-frequency current is modulated by the rotor anisotropy and used to determine the rotor position. These techniques are effective at zero and at low motor speed. Both saturation and cross-coupling have a heavy influence on the correct rotor position detection. In order to highlight the effectiveness of the sensorless technique, the tests are carried out at various operating conditions.

Analysis of permanent magnet machine for sensorless control based on high frequency signal injection

This paper presents the analysis of the surface mounted permanent magnet (SMPM) machine for the sensorless control algorithm using the high frequency fluctuating voltage signal injection method. A simplified high frequency model of a SMPM machine in the estimated rotor reference frame is developed. Then, the impedances of a SMPM machine at high frequency are analyzed by finite element analysis (FEA) and is compared with impedance measurements using a pulse width modulation (PWM) inverter system under various injection conditions. The results of the FEA and high frequency impedance measurements are coincident with each other, and give physical insights in sensorless operation of the SMPM machine. The experimental results of speed control and position control using a commercial SMPM machine are presented based on the analysis of the SMPM machine for the sensorless control algorithm.

Comparison of PM motor structures and sensorless control techniques for zero-speed rotor position detection

The rotor position of a synchronous Permanent Magnet (PM) motor can be detected by means of the superimposition of a high-frequency component to the steady-state stator voltage. Thanks to the anisotropy of the rotor, the corresponding high-frequency current is modulated and used to determine the rotor position. Two techniques can be considered: the first one adopts a pulsating voltage vector in the estimated synchronous reference frame, while the second one adopts a rotating voltage vector. These techniques are effective at zero and at low motor speed. The accuracy of the rotor position detection depends strictly on the rotor saliency, that is, on the geometry of the PM rotor. In fact both saturation and cross-coupling have a heavy influence on the correct rotor position detection. The aim of this paper is to compare the two sensorless control techniques, in conjunction with some rotor geometries. In order to highlight the effectiveness of the sensorless technique, the tests are carried out at various operating conditions. It is found that the effectiveness of the sensorless rotor position detection strongly depends on the choice of the sensorless control technique together with a proper PM rotor geometry.

Sensorless drive of SMPM motor by high frequency signal injection

This paper represents a new sensorless control scheme of surface mounted permanent magnet (SMPM) motors. To estimate the rotor position of the SMPM motor, a high frequency voltage signal is injected and the resultant injected frequency current signal is used. In the SMPM motor, due to the flux of the permanent magnet, the stator core around the q-axis winding is saturated. This saturation effect makes some magnetic saliency of the SMPM motor. In this paper, to estimate the rotor position using this magnetic saliency, the high frequency model of the SMPM motor is developed and the high frequency impedance characteristics are analyzed experimentally under various conditions. The proposed sensorless control scheme makes it possible to drive the SMPM motor at low and zero speed operation even under heavy load conditions. The experimental results verify the performance of the proposed sensorless algorithm.

Implementation and Sensorless Vector-Control Design and Tuning Strategy for SMPM Machines in Fan-Type Applications

This paper presents a complete design methodology for the sensorless vector control of permanent magnet synchronous machine (PMSM) motor drives in fan-type applications. The proposed strategy is built over a linear asymptotic state observer used to estimate the PMSM back-EMF, and a novel tracking controller based on a phase-locked loop (PLL) system, which by synchronizing the estimated and actual d-q frames estimates the rotor speed and position. The paper presents the complete derivation of all associated control-loops, namely state observer, tracking controller, d-q axes current regulator, speed controller, an anti-saturation control loop - which provides inherent operation in the flux-weakening region, and all corresponding anti-windup loops. Detailed design rules are provided for each of these loops, respectively verified through time-domain simulations, frequency-response analysis, and experimental results using a 300 Vdc 3.5 kW PMSM PWM motor-drive, validating both the design methodology and the excellent performance attained by the proposed control strategy

Current measurement issues in sensorless control algorithm using high frequency signal injection method

This paper presents the current measurement issues in sensorless control of a permanent magnet (PM) machine based on the fluctuating high frequency voltage signal injection (HFI) method. In such a sensorless control of the PM machine, the accuracy of the rotor position estimation mainly depends on the accuracy of the current measurement of the drive system. The accuracy of current measurement mainly depends on the current scaling errors, offset currents, and the quantization errors of the analog-to-digital (A/D) converter. In this paper, the effects of the current measurement errors on the accuracy of the rotor position estimation in sensorless control of the PM machine based on the HFI method is analyzed using an example of current measurement system and sensorless control scheme. The simulation and experimental results are shown in order to verify the validity of the analysis results.

Design and selection of AC machines for saliency-based sensorless control

This paper presents a design method for introducing a measurable saliency in the spatial impedances of structurally symmetrical AC machines without any periodic modulation and considerations in selection of AC machines for saliency-based sensorless control. In the structurally symmetrical AC machines such as surface mounted permanent magnet synchronous machine (SMPMM) and induction machine (IM), the saliency in the spatial impedances is built by the spatial saturation on the leakage flux paths. It is explained by the machine model considering the spatial saturation, analyzed by finite element method, and verified experimentally on the test machines. In the design or the selection of AC machines, the consideration of this phenomenon can make any saliency-based sensorless control for zero or low speed operation viable. The selection of AC machines and the control accuracy assessment for saliency-based sensorless control are discussed.