Sensorless Field-oriented Control Research Articles

Solar photovoltaic fed synchronous reluctance motor with optimized rotor flux barriers: Design and performance optimization

This paper focuses on enhancing the design of a synchronous reluctance motor (SyRM) specifically tailored for solar photovoltaic (PV) water pumping applications. With growing adoption of green technologies and renewable energy sources, particularly solar power, there is a need to boost the motor's efficiency to meet the demands of such applications. Utilizing renewable energy for water pumping offers significant advantages in terms of sustainability, scalability, and environmentally friendly energy generation. Achieving optimal efficiency and reliability is paramount, as it reduces overall system cost and enhances reliability. SyRM design methodology in this study integrates both analytical and finite element (FE) procedures. Unlike other motor types, the rotor structure of the SyRM does not include any cages, magnets, or windings, resulting in a robust, reliable, and cost-effective manufacturing process. In SyRM, the rotor is constructed solely with barriers, which significantly impact torque shaping, torque ripple content, and power factor. This paper primarily examines the influence of various air-barrier shapes on different motor performance parameters, such as average torque, torque ripple, saturation, cross-section, and saliency ratio. The selected motor configuration for this investigation is a 4-pole, 100 Hz synchronous reluctance motor with 24 stator slots. The accuracy of the FE analysis findings is validated through a prototype of designed SyRM, followed by comprehensive performance evaluations conducted in a controlled laboratory environment. Additionally, this paper addresses an improved control strategy for a SyRM-based photovoltaic (PV) water pumping system. It eliminates the need for a speed controller in the position sensor-less field-oriented control (FOC) of SyRM. The solar water pump drive involves two stages of power conversion.

A Reliable and Efficient I-f Startup Method of Sensorless Ultra-High-Speed SPMSM for Fuel Cell Air Compressors

Extended back electromotive force (EEMF)-based position sensorless field-oriented control (FOC) is widely utilized for ultra-high-speed surface-mounted permanent magnet synchronous motors (UHS-SPMSMs) driven fuel cell air compressors in medium-high speed applications. Unfortunately, the estimated position is imprecise due to too small EEMF under low speed operation. Hence, current-to-frequency (I-f) control is more suitable for startup. Conventional I-f methods rarely achieve the tradeoff between startup acceleration and load capacity, and the transition to sensorless FOC is mostly realized in the constant-speed stage, which is unacceptable for UHS-SPMSM considering the critical requirement of startup time. In this article, a new closed-loop I-f control approach is proposed to achieve fast and efficient startup. The frequency of reference current vector is corrected automatically based on the active power and the real-time motor torque, which contributes to damping effect for startup reliability. Moreover, an amplitude compensator of reference current vector is designed based on the reactive power, ensuring the maximum torque per ampere operation and higher efficiency. Furthermore, the speed PI controller is enhanced by variable bandwidth design for smoother sensorless transition. These theoretical advantages are validated through experiments with a 550 V, 35 kW UHS-SPMSM. The experimental results demonstrated the enhanced startup performance compared with conventional I-f control.

Backstepping Control Design in Conjunction with an EKF-based Sensorless Field-Oriented Control of an IPMSM

The collector and brushless electronic commutation machines have gained widespread utilization in industrial applications. Among these machines, internal permanent magnet synchronous motors (IPMSMs) have become increasingly popular due to their numerous advantages, including high torque/current and torque/inertia ratios, robust construction, high efficiency, and reliability. However, the incorporation of position sensors in IPMSMs has introduced challenges concerning their application, performance, mass production, and cost. Consequently, the implementation of sensorless control techniques has become essential in drive systems and various applications. This paper proposes a backstepping control approach for achieving speed sensorless control of IPMSMs, employing an extended Kalman filter (EKF). The first step involves developing a comprehensive nonlinear dynamical model of the IPMSM in the direct and quadrature (d-q) rotor frame and obtaining its corresponding state-space representation. Subsequently, backstepping controllers for rotor speed and current tracking are designed to ensure precise tracking and anti-disturbance performance. These controllers are integrated into the field-oriented control (FOC) scheme. The Lyapunov stability theorem is employed to guarantee the asymptotic stability condition of the backstepping controller. To address the challenge of estimating immeasurable mechanical parameters of the IPMSM and accurately tracking the system states, an EKF is designed. This filter enables the estimation of mechanical parameters and achieves high steady-state precision within a finite time. The effectiveness of the proposed methodology is demonstrated through simulations conducted under various dynamic operating conditions, including sudden torque load changes, command speed changes, and parameter variations.

MRAS disturbance observer-based sensorless field-oriented backstepping control of BLDC motor drive

MRAS disturbance observer-based sensorless field-oriented backstepping control of BLDC motor drive

Modified Super-Twisting Algorithm-Based Model Reference Adaptive Observer for Sensorless Control of the Interior Permanent-Magnet Synchronous Motor in Electric Vehicles

In this paper, the model reference adaptive system (MRAS) method has been employed to observe speed in sensorless field-oriented control (FOC) with flux weakening (FW) and maximum torque per ampere (MTPA) operations for the interior permanent-magnet synchronous motor (IPMSM). This paper focuses on the modified MRAS observer, which is based on the sigmoid function as a switching function and also the adaptive sliding mode coefficient. The sliding mode strategies are employed for the adaptation mechanism instead of the PI controller. The conventional PI-MRAS causes oscillations in rotor speed. To solve this problem, the modified adaptive super-twisting algorithm (STA)-based MRAS method is proposed by utilizing the sigmoid function. The proposed modified MRAS is compared to conventional methods. Additionally, it is examined for performance against the fast terminal sliding mode (FTSM), which is applied to the MRAS as an adaptation mechanism in terms of sliding mode strategies. The modified STA-MRAS is explored under the ECE and EUDC (Extra Urban Driving Cycle) drive cycles for electric vehicle applications. Finally, the obtained results show the validity and capability of the proposed adaptive STA-MRAS in terms of speed tracking.

Sensorless field-oriented control inverter of BLDC motor for copter

Sensorless field-oriented control inverter of BLDC motor for copter

Sensorless Field Oriented Control of Synchronous Machines for Low and High Speeds with Space Vector Modulation-Based Direct Flux Control Measurement Sequence

During the last decade, field oriented control has often been implemented with space vector modulation due to its inherent advantages over other modulation techniques. On the other hand, direct flux control is a method that estimates the rotor electrical position of synchronous machines (e.g., permanent magnet synchronous motors) using only voltage measurements. In simple terms, direct flux control replaces position sensors by measuring the voltage difference between the star point of the synchronous machine and an artificial star point at particular instants during the switching pattern. Indeed, previous work dealt with direct flux control resorting exclusively to sinusoidal pulse width modulation and mostly in open-loop speed control schemes. This paper aims to present a space vector modulation-based direct flux control measurement sequence that can be used directly with field oriented control to perform sensorless speed control of synchronous machines. In contrast with previous publications, the direct flux control measurement sequence proposed in this paper not only extracts the direct flux control flux linkage signals with the same offset level but also obtains the phase currents needed for field oriented control without current ripple. In simple terms, the proposed direct flux control measurement sequence based on space vector modulation can be used with field oriented control to perform sensorless closed-loop speed control of synchronous machines. The sensorless speed control with the space vector modulation-based direct flux control sequence is validated for high speeds (80% of the nominal speed) and low speeds (6% of the nominal speed) using a high-fidelity four-pole synchronous machine’s simulation model implemented in ANSYS Simplorer and Maxwell.

Sensorless Field Oriented Control Applied for an Induction Machine by Using the Discontinuous PWM Strategy

Sensorless Field Oriented Control Applied for an Induction Machine by Using the Discontinuous PWM Strategy

Sensorless Field Oriented Control Applied for an Induction Machine by Using the Discontinuous PWM Strategy

Sensorless Field Oriented Control Applied for an Induction Machine by Using the Discontinuous PWM Strategy

Position sensorless field-oriented control of BLDC motor for EV applications

A brushless DC motor (known as BLDC) is a permanent magnet synchronous electric motor which is driven by direct current (DC) electricity, and it accomplishes an electronically controlled commutation system instead of a mechanical commutation system. Major of the BLDC applications are based on speed control like motors used in electric vehicles, washing machines, air conditioners, etc. For the speed regulation of BLDC, TMS320F2837xD and TMS320F28069M microcontrollers are used, which belong to the C2000 family. These microcontrollers are used to increase efficiency by reducing the system components and enabling a cost-effective design of intelligent controllers for three-phase motors. With these devices, digital vector control algorithms like field-oriented control (FOC) may be implemented with much more precision. By computing a dynamic model of the motor, the FOC algorithm maintains efficiency across a wide speed range and considers torque variations with transient phases. The ideas include strategies to get rid of the phase current sensors and switch to sensorless speed control with an observer. The proposed model simulations can be achieved using MATLAB simulation tools, Graphical User Interface (GUI) application and Code Composer Studio (CCS).

OBSERVER OF SPEED AND FLUX LINKAGE IN THE SYSTEM OF VECTOR CONTROL OF ASYNCHRONOUS ELECTRIC DRIVE

The use of physical sensors in electric drive control systems requires taking into account their additional dynamics in the model of the control object, which can cause problems with the synthesis of regulators due to an excessive increase in the order of the control object model. The use of observers makes it possible to recover state variables that are not available for direct measurement and to exclude additional sensors, which contributes to the improvement of operational and cost indicators of control systems. The structure of the observer in asynchronous electric drives must contain such an adaptation function that ensures the asymptotic convergence of the observer to the reference model, which is a real object of control.
 The article presents a synthesis of the speed observer and flux linkage of the rotor of an asynchronous machine in a sensorless field-oriented control system. Equations of electromagnetic processes in an asynchronous machine, formulas of coordinate converters and equations of a PI controller are used as the initial mathematical model. By transforming the differential equations of the asynchronous machine, the structure of the adaptation function is determined, which adjusts the observer model in such a way that the deviations of the stator currents from their calculated values ​​go to zero. In this way, the adaptation function, which uses the vector product of the rotor flux linkage vectors and the stator current, ensures the stability of the movement of the speed identifier.
 In the proposed observer of the speed of an asynchronous machine, which uses stator currents to ensure the asymptotic stability of the observer, in the process of research on mathematical models, self-oscillations of the speed estimate were not found, in contrast to the well-known observer, which uses deviations of the flux links. It is possible to avoid self-oscillations not only by selecting the gain factors of the PI controller, but also due to the fact that there are no integrators not covered by negative feedback in the structure of the observer's electromagnetic circuits.

An Efficient and Robust I-f Control of Sensorless IPMSM With Large Startup Torque Based on Current Vector Angle Controller

Interior permanent magnet synchronous motor (IPMSM) with back electromotive-force (EMF) based sensorless field-oriented control (FOC) is widely used in medium-high speed applications. Unfortunately, the back EMF is too small to be estimated accurately during low speed operation. Hence, the current-frequency ( <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–f</i> ) control with controllable current vector is used for startup. However, the conventional <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–f</i> control is hard to realize the tradeoff between startup speed and load capacity, suffering high-acceleration and high-load startup failure. In this article, a current vector angle controller for sensorless IPMSM startup is proposed to adjust speed-up-stage current acceleration and constant-speed-stage current amplitude with load automatically. The proposed angle controller guarantees the current vector angle close to the maximum torque per ampere angle, which contributes to large startup torque, high operating efficiency and smooth transition from <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–f</i> startup to sensorless FOC. Furthermore, the robustness against parameters variation of angle controller is evaluated quantitatively. These theoretical advantages are verified in experiments with a 380 V, 1.5 kW IPMSM. In particular, the experimental results demonstrate that the proposed <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">I–f</i> control realizes full-load startup even with <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{ \pm }}$</tex-math></inline-formula> 50% flux linkage and <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${\rm{ \pm }}$</tex-math></inline-formula> 30% inductance variation. Furthermore, the startup acceleration auto-adjusts with load to reconcile startup speed and load capacity.

Adaptive PLL-Based Sensorless Control for Improved Dynamics of High-Speed PMSM

This article presents an adaptive quadrature phase-locked loop (AQPLL) for improving the dynamic performance of sensorless high-speed permanent magnet synchronous motors (PMSMs). A conventional quadrature phase-locked loop (QPLL) operating with a fixed bandwidth tends to have a tradeoff between antidisturbance performance and phase delay. The AQPLL can start to operate with a low bandwidth, while the bandwidth is adapted during motor acceleration in real time. Thus, the position estimation error is quickly minimized, leading to correctly decoupled rotor currents and higher available torque. Key parameters of the adaptation mechanism are examined. Sensorless field-oriented control (FOC) with a full-order observer and an AQPLL has been implemented on a field-programmable gate array and verified using a 100 kr/min PMSM. When motor dynamics is unknown or the QPLL cannot be tuned properly, the AQPLL can auto-tune the bandwidth, facilitating up to 25% faster acceleration from 5 to 100 kr/min. The steady-state position estimation error is less than 3 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">${}^{\circ }$</tex-math></inline-formula> at 100 kr/min. Experimental results confirm the effectiveness of the method for achieving a high-performance sensorless FOC of high-speed PMSMs. Furthermore, the AQPLL algorithm has the potential to replace the ordinary QPLL, helping to avoid time-consuming online phase-locked loop tuning in standard drives. This article is accompanied by a MATLAB script demonstrating proposed AQPLL fundamentals.

A Comparative Study and Optimization of Switching Functions for Sliding-Mode Observer in Sensorless Control of PMSM

The sensorless control of the permanent magnet synchronous motor (PMSM) has attracted wide attention due to its high reliability, economic and safety benefits. A fast and high-precision rotor-position estimation is inevitable for the implementation of sensorless control. Sliding-mode observer (SMO) is a preferred solution for sensorless control by many industrial companies. This article addresses the comparison of different switching functions employed in the control structure of sensorless field-oriented control with SMO. The switching functions are classified and their influence on the performance of the PMSM is verified for different shaping coefficients (SC). In addition, a statistical evaluation of the switching functions is provided to find the optimal values of SC. An experimental and statistical evaluation validated the substitutability of signum and hyperbolic switching functions and optimal values of SC have been found.

Sensor-less field orientation control for brushless direct current motor controller for electric vehicles

The electric vehicle traction of Brushless Direct Current Motor (BLDCM) is better from other electric machines due to its magnetic flux linkage, power to weight ratio and so on. The conventional Field Orientation Control (FOC) scheme with sensor for BLDCM has few shortcomings like deviation of current and thrust characteristics. In this paper, we have proposed a sensor less FOC for BLDCM. The back emf and speed of machine are estimated using slide mode controller which is given as a feedback to the motor controller part. The results are observed by varying reference speed which results in controlling the speed of machine accordingly. The results are verified by simulation and experimental evaluation. Simulation is done through MATLAB 2020a software and the experimental evaluation is done through Altair Embed Emulator which controls the BLDCM.

Thermally degraded speed estimation of traction machine drive in electric vehicle

The speed of an induction machine drive (IMD) in the electrified powertrain of an electric vehicle (EV) suffers from thermal degradation caused by EV loading, driving cycle schedules, EV operating conditions, traffic state and temperature. It is necessary to estimate this thermal degradation in order to design appropriate control methodologies to address this significant issue that directly affects the EV performance. This study proposes a robust linear parameter varying (LPV) observer to estimate this degradation in IMD as well as EV speed under various thermal and loading conditions in steady state and during large transients. The stability and robustness of LPV methodology is ensured by optimal gains of H ∞ control and linear matrix inequalities using convex optimisation techniques. The weighting functions in LPV design are optimised by genetic algorithms. The proposed observer performance is compared with that of conventional sensorless field-oriented control and sliding mode observer. An improved speed performance during EV operation is also presented to validate the robustness of the proposed LPV observer against New European Driving Cycle. The performance analysis is conducted through NI myRIO 1900 controller-based electrical drive set-up.

Sensorless FOC Strategy for Current Sensor Faults in Three-Phase Induction Motor Drives

Current sensors are required in Field-Oriented Control (FOC) strategies of Three-Phase Induction Motor (TPIM) drives. Nevertheless, the current sensors are subject to different electrical/mechanical faults which reduce the safety and dependability of the drive system. Single phase current sensor Fault-Tolerant Control (FTC) for sensorless TPIM drives using flux observer and Extended Kalman Filter (EKF) is proposed in this research. In the suggested FTC scheme, current sensor fault detection is based on axes transformation, a logic circuit is served as the fault isolation and reconstruction of faulted currents are achieved through flux observer and EKF. The presented FTC system is capable of detecting and localizing the current sensor fault and switching the drive system to tolerant FOC mode without the rotor speed measurement. The effectiveness of the suggested FTC system is confirmed by experiments on a 0.75kW TPIM drive platform.

Induction Motor PI Observer with Reduced-Order Integrating Unit

This article presents an innovative induction motor state observer designed to reconstruct magnetic fluxes and the angular speed of an induction motor for speed sensorless control system applications such as field-oriented control (FOC). This observer is an intermediate solution between the proportional observer and the classical proportional-integral (PI) observer with respect to which the order of the integrating unit is reduced. Additional modifications of the observer’s structure have been implemented to ensure stability and to improve its functional properties. As a result, two versions of the observer structure were produced and experimentally tested using a sensorless FOC control system. Both structures resulted in correct control system operation for a wide range of angular speeds, including low speed ranges.

MRAS-Based Switching Linear Feedback Strategy for Sensorless Speed Control of Induction Motor Drives

This paper presents a newly designed switching linear feedback structure of sliding mode control (SLF-SMC) plugged with an model reference adaptive system (MRAS) based sensorless field-oriented control (SFOC) for induction motor (IM). Indeed, the performance of the MRAS depends mainly on the operating point and the parametric variation of the IM. Hence, the sliding mode control (SMC) could be considered a good control alternative due to its easy implementation and robustness. Simulation and experimentation results are presented to show the superiority of the proposed SLF-SMC technique in comparison with the classical PI controller under different speed ranges and inertia conditions.

Sensorless LC Filter Implementation for Permanent Magnet Machine Drive Using Observer-Based Voltage and Current Estimation.

For pulse width modulation (PWM) inverter drives, an LC filter can cascade to a permanent magnet (PM) machine at inverter output to reduce PWM-reflected current harmonics. Because the LC filter causes resonance, the filter output current and voltage are required for the sensorless field-oriented control (FOC) drive. However, existing sensors and inverters are typically integrated inside commercial closed-form drives; it is not possible for these drives to obtain additional filter output signals. To resolve this integration issue, this paper proposes a sensorless LC filter state estimation using only the drive inside current sensors. The design principle of the LC filter is first introduced to remove PWM current harmonics. A dual-observer is then proposed to estimate the filter output current and voltage for the sensorless FOC drive. Compared to conventional model-based estimation, the proposed dual-observer demonstrates robust estimation performance under parameter error. The capacitor parameter error shows a negligible influence on the proposed observer estimation. The filter inductance error only affects the capacitor current estimation at high speed. The performance of the sensorless FOC drive using the proposed dual-observer is comparable to the same drive using external sensors for filter voltage and current measurement. All experiments are verified by a PM machine with only 130 μH phase inductance.