Control Of Synchronous Reluctance Machines Research Articles

Fixed Switching Frequency Direct Model Predictive Control of Synchronous Reluctance Machines Based on Stator Flux Gradients

Fixed Switching Frequency Direct Model Predictive Control of Synchronous Reluctance Machines Based on Stator Flux Gradients

Active Q Flux Concept for Sensorless Control of Synchronous Reluctance Machines

This paper proposes a new scheme to use active flux on q-axis for sensorless control of synchronous reluctance machines (SynRM). Conventionally, “Active Flux” on d-axis is adopted to convert a salient pole machine into a fictitious non-salient pole machine. However, the injected d-axis flux can deteriorate high frequency injection (HFI) sensorless control performance or even run the system into unstable region at low speed. This paper demonstrates active flux on q-axis can support back-EMF sensorless control at high speed and improve low speed HFI performance substantially. A seamless transition from HFI sensorless method to back-EMF voltage method is attained after adopting the proposed active q flux. Experiment results are used to validate the proposed method.

Generalized High-Frequency Injection Framework for Sensorless Control of Synchronous Reluctance Machines

Generalized High-Frequency Injection Framework for Sensorless Control of Synchronous Reluctance Machines

Second Harmonic Seamless Splicing Technique Based on Maximum Active-Voltage Vector for Online MTPA Tracking Control of SynRM

Maximum-torque-per-ampere (MTPA) control strategy is widely employed to achieve the optimal efficiency control of synchronous reluctance machines (SynRMs). However, the control efficiency of the conventional method that the optimal current distribution angle is directly calculated based on the knowledge of the machine parameters is seriously affected by the highly nonlinear and time-varying characteristics of SynRMs. Therefore, in order to effectively resolve this problem, a novel MTPA control scheme based on the second harmonic splicing technique is proposed in this article. Differing from the conventional method, the proposed solution utilizes the transient response current slopes of fundamental maximum active-voltage vector to splice a specific second harmonic signal that contains the optimal current distribution angle. After selecting two available and different splicing coefficients in each sector to guarantee the continuity of the spliced second harmonic signal, the optimal current distribution angle can be obtained accurately without any machine parameters through a simple signal demodulation, which significantly enhances the robustness to machine parameter variations. Furthermore, the influence of rotor position acquisition errors caused by the position sensor's limited accuracy and installation misalignment is analyzed in detail. Finally, the experimental results demonstrate the effectiveness and feasibility of the proposed MTPA control scheme.

Signal-Injection Sensorless Control of Synchronous Reluctance Machines for Overload Operation

Signal-injection sensorless control for low speeds region are usually assisted with compensation techniques to support the heavy load operations beyond rated conditions. For the standard <inline-formula><tex-math notation="LaTeX">$d$</tex-math></inline-formula>-axis pulsating voltage injection, this article analyzes the prospect of using <inline-formula><tex-math notation="LaTeX">$q$</tex-math></inline-formula>-axis current-model flux instead of the <inline-formula><tex-math notation="LaTeX">$q$</tex-math></inline-formula>-axis current for decoupled position estimation. Through convergence analysis, the feasibility of operation at overload is evaluated for the decoupled scheme against the state-of-art compensation technique and is shown to be a promising candidate for its simplicity and the lack of <i>preprocessing</i> of flux-map. All claims are experimentally validated on a 1.1&#x00A0;kW synchronous reluctance machine test-bench.

Self-Adaptive Synergistic Optimization for Parameters Extraction of Synchronous Reluctance Machine Nonlinear Magnetic Model

For mechanism analysis and high-performance control of synchronous reluctance machine (SynRM), accurate and reliable parameter identification of nonlinear magnetic model is always required. However, the accuracy and robustness of traditional heuristic algorithms are restricted by incomplete individual performance evaluation and single population evolution mechanism. In this paper, we propose a self-adaptive synergistic optimization (SSO) algorithm for extracting the parameters of the model. A novel synergistic-performance evaluation is first established to classify candidates automatically. Then, a self-organized mechanism is proposed to select optimal evolution strategies designed for classified candidate solutions. Around the current best candidate, the exploration is guaranteed in priority. Meanwhile, a self-adaptive mechanism is introduced to select other candidates to construct more promising evolutionary direction. Thus, achieving a good balance between exploration and exploitation. The parameter estimation performance of SSO algorithm is evaluated through standard datasets of SynRM magnetic model obtained by the finite element analysis. Comprehensive experiment results demonstrate the competitiveness and effectiveness of the proposed SSO algorithm compared with other algorithms, especially in terms of the accuracy and robustness. According to these superiorities, it can be concluded that the proposed algorithms are promising parameter identification methods for SynRM nonlinear magnetic model.

High-Bandwidth Sensorless Control of Synchronous Reluctance Machines in the Low- and Zero-Speed Range

Two aspects of sensorless control of synchronous reluctance machines (SynRMs) in the low-speed and zero-speed range are gaining more and more importance: how to achieve a high control bandwidth and how to lower the test current amplitude to minimize audible noise and high-frequency (HF) losses. A high control bandwidth can be realized by a square-wave-shaped voltage injection (SWSVI). This article presents a new approach, controlling the current ripple generated by the SWSVI constant and simultaneously maintaining a minimum required HF test current amplitude. The proposed solution is optimized for the highly nonlinear machine behavior of SynRMs combined with a standard industrial inverter using regular current sampling. A new low-noise current demodulation by a Kalman filter and its empiric tuning is presented. The prediction step of the filter compensates for the dead time of the control algorithm. Experimental results confirm the excellent performance. Compared to the conventional binomial filter, only half of the test signal amplitude is required. The mean square error of the current demodulation was reduced by 90%.

Position Sensorless Control of Synchronous Reluctance Machines Based on Magnetic Saturation Depending on Current Phase Angles

Position sensorless control of synchronous reluctance machines is not easy due to nonlinear correlations caused by extensive magnetic saturation. This article investigates stability of a conventional saliency-based method and, for the first time, shows that the method becomes unstable at high torque with high magnetic saturation not due to cross-coupling effect itself but due to expansion of the cross-coupling effect through feedback of the estimated position. This instability occurs even when neither disappearance of the saliency nor reversal of the estimated d- and q- axes arises. A novel method to overcome this instability is proposed, which utilizes magnetic saturation depending on current phase angles. The proposed method was verified by simulations and experiment using a prototype machine. The results demonstrated that the proposed method achieved stable sensorless operation at the maximum torque, and thus, surpassed the conventional saliency-based method, the feasible torque of which was limited to 60% of the maximum for the prototype machine.

Sensorless Synchronous Reluctance Motor Drives: A General Adaptive Projection Vector Approach for Position Estimation

This article presents a mathematical framework for the design and analysis of position observers for sensorless control of synchronous reluctance machines. The approach expresses the observer error via a generalized projection vector. Moreover, the proposed framework includes an improved inductance model to account for the position error-induced inductance variations. First, the instability regions of active flux-based position observer are analytically identified and validated. Then, a novel technique, adaptive projection vector for position error estimation, is introduced, immune to instability of active flux scheme. Furthermore, the proposed technique can be augmented with a second projection vector for independent estimation of speed error, referred to as adaptive projection vector matrix for position and speed error estimation. Sensitivity analysis to parameter errors is developed. Stability and performance of proposed technique is validated on a 1 kW synchronous reluctance motor test bench.

Sensorless Synchronous Reluctance Motor Drives: A Full-Speed Scheme using Finite-Control-Set MPC in a Projection Vector Framework

The article presents a general framework valid for the high-frequency excitation-based position observer for low-speed sensorless control of synchronous reluctance machines. A finite-control-set model-predictive-control technique is proposed accordingly, exploiting the switching current ripple for the position estimation. The position error due to cross saturation is inherently accounted for. The proposed scheme is integrated with an adaptive projection vector for position error estimation for high speeds region through a simple fusion structure for a smooth transition. The performance of the proposed technique is validated on a 1.1-kW synchronous reluctance motor test bench.

Combined Active Flux and High-Frequency Injection Methods for Sensorless Direct-Flux Vector Control of Synchronous Reluctance Machines

This paper proposes a sensorless control scheme for synchronous reluctance (SyR) motor drives based on the direct-flux vector control (DFVC) method. The control operates in stator-flux-oriented coordinates, using constant switching frequency. A hybrid position and speed observer is proposed, based on the combination of the active flux concept and high-frequency signal injection and demodulation. The two methods are fused together to form a unique position and speed estimate signals, with seamless transition between the two models based on reference speed. The proposed observer covers a wide speed range, from standstill operation at full load to flux weakening (FW). Furthermore, it is inherently immune from position estimation error caused by cross saturation, as proven mathematically and experimentally. The motor is operated according to the maximum torque per ampere (MTPA) law. Specific issues related to MTPA around zero torque are addressed in this paper. The proposed control technique extends the range of application of the DFVC to encoderless drives, and can be usefully adopted in those applications where both zero-speed and FW speed range operations are necessary, such as home appliances, or automotive and aerospace actuators and generators. A 2.2-kW SyR motor prototype was tested to verify the feasibility of the proposed method. Key tuning aspects are addressed in this paper.

Stator-Flux-Oriented Vector Control of Synchronous Reluctance Machines With Maximized Efficiency

This paper presents a position-sensorless vector torque controller designed to achieve maximum efficiency over a range of power and rotational speed for a synchronous reluctance machine. A model of the synchronous reluctance machine is presented which incorporates both winding and core losses. It is then shown that a stator-flux-oriented control scheme can achieve synchronous operation of the machine without a position sensor at medium and high electrical frequencies. For a given speed and torque, power losses in the machine are shown to be a function of only the stator flux magnitude. As the power losses are a convex function of the stator flux level, the optimal flux value can be found using a one-dimensional optimization algorithm, such as the Method of Sequential Quadratic Interpolations. Optimal flux values for a synchronous reluctance machine are determined using an experimental setup that accurately determines losses in the motor/drive system. Experimental results obtained from the test setup confirm the validity of the controller and the optimization algorithm.

Magnetic saturation effects on the control of a synchronous reluctance machine

Experimental results on the magnetic saturation effects on the control of a small synchronous reluctance machine (600 W) are presented in this paper. A new model of the machine, including saturation effects and cross magnetization is first developed. An approach based on total and mutual inductances is followed instead of the traditional approach through magnetizing and leakage inductances. All of the electrical and mechanical parameters measurements required for the simulations are given. A rotor-oriented vector control of the synchronous reluctance machine is achieved with a digital-signal-processor (DSP) board (TMS320C31) and experimental results are presented. When the magnetic circuit is saturated, the simulation with the developed model shows good, accurate results when compared to the experimental ones.

Magnetic Saturation Effects on the Control of a Synchronous Reluctance Machine

Experimental results on the magnetic saturation effects on the control of a small synchronous reluctance machine (600 W) are presented in this paper. A new model of the machine, including saturation effects and cross magnetization, is first developed. An approach based on total and mutual inductances is followed instead of the traditional approach via magnetizing and leakage inductances. All the electrical and mechanical parameters measurement required for the simulations are given. A rotor-oriented vector control of the synchronous reluctance machine is achieved with a DSP board (TMS320C31) and experimental results are presented. When the magnetic circuit is saturated, the simulation with the developed model shows a good accuracy of the results when they are compared to the experimental ones.

Control of synchronous reluctance machines

This work develops a comprehensive approach to the control of inverter-fed synchronous reluctance machines (SYNCREL), based on the machine's ideal model. From the theory a control simulation is designed. Simulation and experimental results are presented. The effects of saturation and iron losses are briefly considered. >

Theoretical aspects of control of synchronous reluctance machines

The author presents a theoretical performance analysis of several control strategies for synchronous reluctance machines which are being fed from a current controlled inverter. The three main control strategies considered have as their objectives to allow maximum rated torque, maximum rate of change of torque and maximum power factor, respectively, from the machine. These control strategies are investigated to determine their limitations and inter-relationships. A technique for 'field weakened' control of the machine is developed. It is shown that the rate of change of torque performance of the control strategies based on constant current angle is poor at lower angular velocities. A control strategy based on having constant current in the most inductive axis of the machine is shown to give better performance under these conditions, and a technique for moving between control strategies is developed. >