Control Of Permanent Magnet Synchronous Machines Research Articles

New Electrical Inversed-Series Connection for Even-Phase Symmetrical PMSMs

This paper presents an extension of previous methods in order to find electrical series connections between multiphase machines, allowing the independent control of each one of them. These new electrical series connections explore the symmetrical disposition of the phases of even-multiphase machines, allowing the inversed connection of some of the phases, different from the direct connections as it was previously done. Therefore, electrical series connections of two symmetrical six-phase or of four symmetrical ten-phase machines are now possible. Besides that, this new solution ensures a natural independent control of permanent-magnet synchronous machines even if the back electromotive forces (back EMFs) generated by the rotor are not sinusoidal, without need of special machine conception or supplementary control strategy. This control independency is mathematically proved using the decomposition of multiphase machines in fictitious diphase and homopolar machines. Experimental results are presented to show the functioning and the advantages of this new coupling for two symmetrical six-phase permanent-magnet synchronous machines (PMSMs).

Permanent Magnet Synchronous Machine Drive Control Using Analog Hall-Effect Sensors

Control of permanent magnet synchronous machines (PMSMs) requires rotor position measurement/estimation, as well as the magnet polarity detection for startup of the machine. The rotor position of PMSMs is typically measured using a speed/position sensor (e.g., an encoder), while the magnet polarity is commonly measured using digital hall-effect sensors. Since simplifying the system can help improve reliability and reduce the cost associated with the measurements, the use of low cost analog hall-effect sensors for the estimation of the PM position, and polarity for control of PMSMs drives is evaluated in this paper. Experimental results performed on a 7.5-kW motor confirm that analog hall-effect sensors can replace both speed/position sensors and digital hall-effect sensors while maintaining adequate performance of the drive at a lower cost.

Magnet Synchronous Machine of Mine Belt Conveyor Gearless Drum-Motor

In the recent decades there has been a tendency for simplifying gears construction, furthermore a lot of manufacturers design gearless electric drives for traction and power mechanisms. Rejection of mechanical transmission and replacing obsolete induction motor with energy-efficient permanent magnet synchronous machine (PMSM) allow to increase electric drive reliability, reduce repair and maintenance costs, also improve the technological process and industrial safety.This article is devoted to questions of permanent magnet synchronous motor control for underground belt conveyor gearless drum-motor. The model of PMSM with special construction was created by finite elements method in Infolytica MagNet and MotorSolve environments, simulation was provided with to regard due special nature of high-torque slow-moving power machines. The last section of article contains comparison of methods for high-torque slow-moving PMSM control and simulation results of vector control system.

Comparison of Two-Individual Current Control and Vector Space Decomposition Control for Dual Three-Phase PMSM

The relationship between the two-individual current control and the vector space decomposition (VSD) control for a dual three-phase permanent magnet synchronous machine (PMSM) is investigated in this paper. It is found that the VSD control is more flexible in controlling the fundamental current in αβ subplane and the fifth, seventh current harmonics in z 1 z 2 subplane with different proportional and integral (PI) gains, while the two-individual current control is comparable with the VSD control in having the same PI gains in the αβ and z 1 z 2 subplanes. It is also found that the two-individual current control may have potential instability issues due to the mutual coupling between the two sets of three-phase windings. If the mutual coupling between the two sets is weak to some extent, then the two-individual current control could have the same dynamic performance as the VSD control without the stability issues. Experiments are conducted on a prototype dual three-phase PMSM to validate the theoretical analysis.

Improved Pulsating Signal Injection Using Zero-Sequence Carrier Voltage for Sensorless Control of Dual Three-Phase PMSM

The sensorless control performance of pulsating carrier signal injection employing zero-sequence voltage for dual three-phase (DTP) permanent magnet synchronous machine (PMSM) drives is investigated in this paper. This method has the synergy of high bandwidth of zero-sequence voltage method and high position estimation accuracy of pulsating injection strategy. However, such a method for single three-phase PMSM exhibits large oscillation in position estimation error due to undesirable harmonic components in the zero-sequence carrier voltage, and the existing compensation methods usually require complex structures or intensive offline measurements. As for DTP-PMSM, the undesirable harmonic components for the pulsating injection can be suppressed with an optimum phase shift between the two injected high-frequency signals. Besides, a new simple measurement method of zero-sequence carrier voltage is proposed with only one voltage sensor placed between the two isolated neutral points. As a result, the rotor position estimation accuracy can be significantly improved. The experimental results verify the effectiveness of the proposed method for DTP-PMSM.

Fault-Tolerant Control of Dual Three-Phase Permanent-Magnet Synchronous Machine Drives Under Open-Phase Faults

In this paper, a fault-tolerant control is proposed for dual three-phase permanent-magnet synchronous machine (PMSM) drives under open-phase faults. The object of the proposed fault-tolerant control is to maximize the torque capacity while the overcurrent protection is taken into account. Hence, the proposed fault-tolerant control is named as torque mode in this paper. Another existed fault-tolerant control for dual three-phase PMSM drives under open-phase faults is loss mode, in which the system copper loss is minimized. Torque mode is compared with loss mode, and two important conclusions are given: 1) loss mode can reduce more copper loss; and 2) torque mode can output more torque. The performances of torque mode and loss mode are verified by experimental results.

Current sensor fault diagnosis and adaptive fault-tolerant control of PMSM drive system based on differential algebraic method

As the key sensor of Electric Vehicle Permanent Magnet Synchronous Machine (PMSM) drive system, the current sensor usually occurs gain and offset fault, and the fault will directly affect the performance and stability of PMSM drive system. Therefore, the inverter nonlinearity dead-time compensation method is first investigated allowing for parasitic capacitor effect, and the proposed method are compared with the traditional dead-time compensation method, moreover, the technical advantages are all validated via experimental results, the fault diagnosis accuracy problem of current sensor caused by the inverter nonlinearity induced offset voltage between inverter reference and output voltage are cleverly solved. Then, the differential algebraic based fault diagnosis method and adaptive fault-tolerant control strategy are presented. An integrated solution of PMSM drive system is innovatively proposed integrated the proposed dead-time compensation method with proposed differential algebraic based fault diagnosis method and adaptive fault-tolerant control strategy together. At last, system simulation and dSPACE based experimental test are implemented to validate the feasibility and effectiveness of proposed integrated solution of PMSM drive system and the conclusions are shown.

Initial Rotor Position Estimation Using Zero-Sequence Carrier Voltage for Permanent-Magnet Synchronous Machines

Both rotating and anticlockwise pulsating signal injection methods based on zero-sequence voltage sensing have been reported to have large signal-to-noise ratio and bandwidths, and great stability for the sensorless control of permanent-magnet synchronous machines. However, the initial rotor position estimation and magnetic polarity identification using zero-sequence voltage have not been investigated. Therefore, this paper presents two types of magnetic polarity identification methods, based on the amplitude variation of zero-sequence voltage due to saturation changing, and based on the secondary harmonics of zero-sequence voltage, for the two carrier injection methods, respectively. It is found that the amplitude variation based method using zero-sequence voltage has higher detection sensitivity for the real magnetic polarity compared to the conventional method using the carrier current. In contrast, the secondary harmonic based identification method using zero-sequence voltage for rotating signal injection has the advantage of fast response, and moreover has large signal amplitude and less distortion compared to the conventional secondary carrier current harmonics. However, the secondary harmonic method loses the capability for polarity detection for the anticlockwise pulsating injection method. Experiments are carried out on a laboratory permanent-magnet machine to verify the theoretical analyses.

Research of position sensorless control for PMSM based on sliding mode observer and phase-locked loop

In this paper, a sliding mode observer is presented for achieving the speed and position sensorless control based on estimating the rotor position of permanent magnet synchronous machines (PMSM). According to the PMSM mathematical model and the sliding mode observer (SMO) control theory, the SMO model is given. The stability condition of SMO is studied to make sure that the observer is stable in converging to the sliding mode plane. Compared to conventional sliding mode observer, the proposed observer based on sliding mode observer and phase-locked loop can effectively reduce the influence of the sliding mode chattering and improve the precision of the rotor position estimation. This paper analyses the structure and performance of the proposed SMO strategy with Simulink-based simulation. The simulation results show that the novel sliding mode observer is more effective than the conventional method.

Novel Square-Wave Signal Injection Method Using Zero-Sequence Voltage for Sensorless Control of PMSM Drives

In this paper, a novel pulsating carrier signal injection strategy utilizing zero-sequence voltage is proposed for sensorless control of permanent-magnet synchronous machine (PMSM) drives. Different from the conventional zero-sequence carrier voltage sensing method using rotating signal injection in the stationary reference frame, the proposed pulsating injection is based on the estimated reference frame, which rotates anticlockwise at twice estimated rotor electrical angular speed. Then, the rotor position estimation is fulfilled via enabling the zero-sequence carrier voltage to zero. Compared with conventional rotating injection using zero-sequence voltage, the proposed strategy is simpler for signal demodulation and more robust to signal processing delays due to the fact that it is amplitude modulated by machine saliency and phase shifts of saliency position due to signal processing delays are intrinsically cancelled, which is the same as the classical pulsating injection in the estimated synchronous reference frame with carrier current sensing. Therefore, the proposed method can combine the synergies of zero-sequence method (i.e., high bandwidth and stability) and pulsating injection (i.e., increased accuracy and fast dynamic response). Furthermore, the cross-coupling magnetic saturation effects on zero-sequence voltage sensing-based sensorless control are discussed in detail. All the theoretical analyses are validated by experiments on a laboratory surface-mounted PM (SPM) machine.

Torque Ripple Minimization for Direct Torque Control of PMSM With Modified FCSMPC

In this paper, a Lyaupnov-based finite control set model predictive direct torque control for the permanent magnet synchronous machine (PMSM) is proposed. In the proposed control scheme, the finite control set prediction and the Lyapunov theory are combined to minimize the torque ripple. The eight voltage vectors of the two-level converter are utilized as a finite control set for the torque prediction of the PMSM. A cost function considering the torque error, the maximum torque per ampere operation and the current limitation is introduced. Comparing to the conventional finite control set predictive control, the dominant part of the cost function is utilized as a Lyapunov function to estimate the duty cycle of each voltage vector. An optimum voltage can be obtained by the optimum voltage vector from the eight vectors and their duty cycles. A small sampling frequency and a fixed switching frequency can be realized when compared to the conventional finite set model predictive control. In the end, the simulation and experimental results validate the performance of the proposed control scheme.

PMSM Model Predictive Control With Field-Weakening Implementation

Permanent-magnet synchronous machine (PMSM) drives have become popular for motion control applications due to their performance and high torque-to-weight ratio. The complex task of PMSM control in high-performance applications is currently usually resolved with classical vector control. Modern control techniques such as model predictive control (MPC) can provide significant benefits over field-oriented control, especially with straightforward controller tuning and constraints handling. Unfortunately, these new algorithms usually suffer from problems with their computational complexity. In this paper, we present a PMSM control method based on an explicit MPC with a novel linearization and constraints handling method, allowing natural field weakening. The algorithm was designed with respect to computationally feasible implementation in the control hardware. The proposed control algorithm has been proved and successfully verified in both simulation and implementation on a real motor.

Flatness-Based Torque Control of Saturated Surface-Mounted Permanent Magnet Synchronous Machines

Modern permanent magnet synchronous machines (PMSMs) may also be operated in regimes where significant magnetic saturation occurs. Classical fundamental wave models do not incorporate magnetic saturation in a systematic way. Mostly, only heuristic extensions can be found in the literature. Control schemes based on such $dq0$ -models are thus often unable to achieve the given control demands. This paper proposes a flatness-based torque control strategy for a saturated surface-mounted PMSM. Different to existing works, magnetic saturation is considered in a thorough and physically consistent way. Based on a calibrated magnetic equivalent circuit model of the PMSM, a simplified model suitable for the flatness-based controller design is derived. The proposed 2-DOF control scheme inherently accounts for the mutual coupling of the phase windings. Furthermore, the time-varying controller gains are obtained by pole placement technique. In contrast to the majority of controllers used for PMSM control, the proposed control scheme is formulated in the stator-fixed reference frame, and hence, no coordinate transformation is necessary. The flatness-based torque controller is implemented on an experimental test bench. An accelerated run-up of the PMSM with about four times the rated torque is performed to highlight the feasibility of the proposed approach. Finally, the flatness-based torque controller is compared with a common vector control implementation based on a $dq0$ -model of the motor.

A Novel Algorithm Based on Polynomial Approximations for an Efficient Error Compensation of Magnetic Analog Encoders in PMSMs for EVs

This paper presents a novel algorithm based on polynomial approximations (PAs) for an efficient error compensation of magnetic analog encoders (MAEs) in permanent-magnet synchronous machines (PMSMs) intended for electric vehicle (EV) propulsion. The proposed PA algorithm requires a negligible memory space compared to a very high-resolution look-up table (LUT). The use of polynomials allows compensating every possible input rotor position without carrying out an interpolation or a rounding to the nearest quantized value. The PA algorithm has been implemented to work in real time on a TM4 EV drive controlling an 80 kW PMSM. The performance of the algorithm has been validated at 6000 and 9000 r/min under $+$ 85 and ${\pm}$ 55 Nm of torque, respectively. The electromagnetic interference (EMI) effects have been minimized using a type-2 phase-locked loop (PLL). The proposed PA algorithm assisted with the PLL is capable of reducing the total position error to a range as small as ${\pm}\text{0.2}^\circ$ . The combination of these two algorithms is a promising solution for compensating the position error in quadrature analog encoders. The experimental results obtained with the 80 kW PMSM demonstrate the feasibility of low-cost MAEs for achieving high-performance field-oriented control (FOC) of PMSMs in EV drives.

Carrier Signal Injection-Based Sensorless Control for Permanent-Magnet Synchronous Machine Drives Considering Machine Parameter Asymmetry

This paper investigates the influence of asymmetric machine parameters on carrier signal injection-based sensorless control of permanent-magnet synchronous machines (PMSMs). With either rotating or pulsating signal injection, the second harmonic position errors arise due to the parameter asymmetry. Furthermore, it is found that for the two carriers, the second harmonic errors are different for resistance asymmetry but the same for inductance asymmetry. In order to suppress the position errors, the carrier signal selection guidelines are discussed for resistance asymmetry, while for inductance asymmetry, novel online compensation strategies with dual-frequency injection are also proposed. Finally, the theoretical analyses and proposed compensation methods are validated by experiments on an interior PM (IPM) machine with added phase resistance/inductance to simulate asymmetric conditions.

Influence of back-EMF and current harmonics on sensorless control performance of single and dual three-phase permanent magnet synchronous machines

Purpose – The purpose of this paper is to investigate the influence of back-EMF and current harmonics on position and speed estimation accuracy for single and dual three-phase (DTP) permanent magnet synchronous machines (PMSMs) with two fundamental-model-based sensorless control strategies which are widely utilized for AC machines, i.e. flux-linkage observer (FO) and simplified extended Kalman filter (EKF). Design/methodology/approach – The effect of distorted back-EMF is studied for sensorless vector control of single three-phase PMSM. For the influence of current harmonics, unlike the existing literature where the current harmonics are deliberately injected, in this paper, sensorless switching-table-based direct torque control (ST-DTC) strategies for DTP-PMSM which inherently suffer from non-sinusoidal stator currents in addition to the distorted back-EMF, are investigated experimentally. Findings – By employing the FO and simplified EKF-based sensorless vector control of single three-phase PMSM, it can be concluded that the rotor position estimation accuracy is less affected by the back-EMF harmonics when the simplified EKF method is utilized since it is less sensitive to such noises. When the influence of non-sinusoidal stator currents together with back-EMF harmonics is investigated for the conventional and modified ST-DTC of DTP-PMSM, it is indicated that the simplified EKF exhibits better position and speed estimation accuracy in both the conventional and modified ST-DTC strategies. In addition, its steady-state performance shows a slight superiority over that based on FO, in terms of flux and torque ripples, and THD of phase currents. For the dynamic performance, the estimated speed of simplified EKF shows less phase lag and fluctuations compared to that of FO. Originality/value – This paper introduces the influence of back-EMF and current harmonics on sensorless control performance for single and DTP PMSMs. Detailed experimental results show that the simplified EKF exhibits better rotor position and speed estimation accuracy compared to that of FO due to its higher noise-rejection ability.

Minimum-Voltage Vector Injection Method for Sensorless Control of PMSM for Low-Speed Operations

In this paper, a simple signal injection method is proposed for sensorless control of permanent-magnet synchronous machine (PMSM) at a low speed, which ideally requires one voltage vector only for position estimation. The proposed method is easy to implement, resulting in low computation burden. No filters are needed for extracting the high-frequency current signals for position estimation. The use of low-pass filters (LPFs) in the current control loop to obtain the fundamental current component is not necessary. Therefore, the control bandwidth of the inner current control loop may not need to be sacrificed. The proposed method may also be further developed to inject two opposite voltage vectors to reduce the effects of inverter voltage error on the position estimation accuracy. The effectiveness of the proposed method is demonstrated by comparing with other sensorless control method. Theoretical analysis and experimental results are given for validating the proposed new sensorless control method.

Experimental Parameterization of a Design Model for Flatness-based Torque Control of a Saturated Surface-Mounted PMSM

Abstract: Tailored mathematical models of permanent magnet synchronous machines (PMSMs), which systematically account for magnetic saturation and harmonics, are important for advanced nonlinear control strategies. The systematic consideration of the nonlinearities in the controller design allows to exploit the overall machine performance in the entire operating range. Physics-based models using, e.g., magnetic equivalent circuits (MECs) typically rely on details of the geometry and knowledge of the material behavior, which might not be available in many industrial applications. Hence, this paper proposes a concept to experimentally determine the parameters of a controller design model, which is derived from an MEC approach. This design model is used for flatness-based optimal torque control for surface-mounted PMSMs with significant magnetic saturation. Torque, current, and voltage measurements from different static and dynamic experiments are used to experimentally determine the optimal parameters of the model. The influence of the effective phase resistance on the accuracy is discussed and a method for a compensation is proposed. The influence of the identified parameters on the controlled PMSM is finally investigated by means of simulations of a calibrated model.

Optimal torque control of permanent magnet synchronous machines using magnetic equivalent circuits

In recent years, permanent magnet synchronous machines (PSMs) are often designed in a mechatronic way to obtain e.g. special torque characteristics at zero currents or maximum efficiency. These designs are often characterized by a pronounced magnetic saturation and non-sinusoidal properties. This paper describes the optimal torque control of such PSMs utilizing a magnetic equivalent circuit (MEC) model. In contrast to approaches based on fundamental wave models (dq0-models), which utilize the Blondel–Park transformation and typically consider saturation and non-sinusoidal characteristics only in a heuristic way, MEC models allow to systematically account for these effects. Given the MEC model, optimal values for the coil currents are obtained from a constrained, nonlinear optimization problem, which can be efficiently solved by exploiting the special mathematical structure of the model. The results of the optimization are used in a flatness-based torque control strategy. The performance and practical feasibility of the proposed torque control concept are demonstrated by experiments on a test stand. Finally, it is shown that using this torque control in an outer angular speed control loop also proves to be beneficial.

An Extended Flux Model-Based Rotor Position Estimator for Sensorless Control of Salient-Pole Permanent-Magnet Synchronous Machines

Starting from the classical dynamic model of salient-pole permanent-magnet synchronous machines (PMSMs) expressed in the stationary reference frame, this paper presents a mathematical model reconstruction process for salient-pole PMSMs, from which an extended flux-based machine model is derived. Compared with the commonly used extended electromotive force-based model, the extended flux-based model has notable advantages of simpler model structure and less sensitive to the variations of machine parameters and operating conditions. A new extended flux model-based rotor position estimator is then proposed for sensorless control of salient-pole PMSMs by utilizing a sliding-mode observer with a dynamic position compensator. The latter improves the dynamic performance and low-speed operating capability of the sensorless control system. Both simulation and experimental results are provided to validate the proposed rotor position estimator and the sensorless control system for salient-pole PMSMs.