Sensorless Control Scheme Research Articles

Position Sensorless Control for PMSM Drives With Single Current Sensor

The aim of this article is an attempt to provide a more credible control mode or a fault-tolerant control strategy for permanent magnet synchronous motor (PMSM) drives when an unexpected failure occurs to the current or position sensor. Considering that, a position sensorless control method that uses only one current sensor is proposed. Different from a traditional position sensorless control scheme that utilizes additional current sensors to obtain information of multiple phase currents, only a single current sensor (SCS) arranged on one of the current branches is included among the whole control circuit. Three-phase currents are reconstructed by sequentially sampling the SCS under specific voltage vectors, and directly employed for motor position estimation. A nonlinear position observer established according to the gradient descent is adopted. Focusing on the special current-acquisition pattern in this article, a step-size optimization method based on golden section search is proposed to minimize position estimation error. The experimental results reveal that the method in this article is comparable to the traditional full-current-sensor method in terms of position estimation, which confirms the fault-tolerant capability as one certain sensor of the control structure malfunctions.

A Comparison Research on Sliding Mode Observation Methods for SPMSM in Sensorless Environment of Medium-to-High Speed

Aiming at sensorless control system of surface attached permanent magnet synchronous motor (SPMSP), three observation algorithms proposed in recent years to estimate rotor position and speed under medium-high speed operation were introduced in this paper. The working principles, advantages and disadvantages of these algorithms such as the Extended Kalman filter algorithm (EKF), Model Reference Adaptive System (MRAS) and Sliding Mode Observer (SMO) were compared, and the applicability of these three algorithms on SPMSP at present was compared and summarized. Furthermore, a sensorless control strategy based on improved SMO was designed to ensure sensorless control effect under medium-high speed operation of SPMSM.

A ℌ<SUB align="right">∞-based approach for sensorless control of BLDC motors fed with four-switch inverters

This paper presents the design and the implementation of a cost-effective sensorless control strategy for brushless DC motors fed with a four-switch inverter. In this method, a ℌ∞-controller was designed to control phase currents. A disturbance observer is used to estimate the back-EMFs of the rotor. These variables were used as the inputs of a phase locked loop to estimate the rotor position. The performances of this system were validated through simulation results. It was shown that the rotor speed remains close to the desired reference and the estimated angle is synchronised with the actual back-EMF. Compared with existing solutions, the proposed method allows the limitation of switching losses by the removal of the hysteresis controllers and the possibility to use standard driver circuits with internally set deadtime. Finally, an experimental prototype was built to verify the correctness of the presented control method.

Sensorless Control of PMSM Drives Using Reduced Order Quasi Resonant-Based ESO and Newton–Raphson Method-Based PLL

This article proposes a novel sensorless control strategy for permanent magnet synchronous motor drives using reduced order quasi resonant-based extended state observer (ROQR-ESO) and Newton–Raphson method-based phase-locked loop (NRM-PLL). Due to the low-pass filtering characteristics, the conventional linear extended state observer (LESO) is not adequately able to track the fast-varying back electromotive forces (BEMFs). On this basis, the ROQR-ESO, which plants a ROQR controller into the internal model of conventional LESO, is presented to obtain BEMFs without phase lag. Moreover, the NRM-PLL, regarded as an improved finite position set-PLL, is proposed. After the rotor position is divided into four parts by utilizing a position quartering method, the extremely accurate rotor position can be obtained only by three iterations. In this method, no parameters need to be adjusted and great dynamic response can be achieved. The capacity of the proposed scheme is verified on a 750 W permanent magnet synchronous motor drive platform.

High-Tracking-Precision Sensorless Control of PMSM System Based on Fractional Order Model Reference Adaptation

In order to solve parameter fluctuations and disturbances, a novel fractional order model reference adaptive speed observer that estimates the rotor position and the angular velocity from the stator currents is proposed for sensorless control of permanent-magnet synchronous motors (PMSM). Firstly, a novel fractional order model reference adaptive controller (FOMRAC) for adaptive identification is designed to achieve fast response and high precise identification of load torque in the full speed range when the motor is running at variable-speed or variable-load. Additionally, an appropriate adjustable matrix P is chosen to make the convergence of the adaptive law meet the requirements. Next, an improved model reference adaptive observer (MRAO) is proposed to suppress the serious chattering and compensate rotor position error, which can stabilize the system. The validity of the proposed fractional order model reference adaptive sensorless control strategy for PMSM is demonstrated with simulations.

Sensorless Control Strategy of Permanent Magnet Synchronous Motor Based on Fuzzy Sliding Mode Controller and Fuzzy Sliding Mode Observer

Sensorless Control Strategy of Permanent Magnet Synchronous Motor Based on Fuzzy Sliding Mode Controller and Fuzzy Sliding Mode Observer

Displacement sensorless control of a bearingless induction motor based on hybrid flux estimation

ABSTRACT To address the problems of bulk-size, high cost for traditional mechanical displacement sensors in a bearingless induction motor (BL-IM), a displacement sensorless control strategy based on hybrid flux estimation for the BL-IM is proposed. By analyzing the merits and shortcomings of the voltage-type and the current-type flux estimator, a hybrid flux estimation model composed of two kinds of flux estimators is designed using the complementary characteristics of the two estimation models in high- and low-speed applications, and the velocity correlation function is used to achieve dynamic smooth switching between two models in the medium-speed zone. Secondly, the radial displacement of the rotor is calculated according to the mathematical model of the BL-IM, so as to realize the self-detection of the rotor displacement. Then, the vector control displacement sensorless system of the BL-IM is established. Finally, the simulation and experimental study are carried out on an experimental prototype designed by our research group. The simulation and experimental results show that the flux estimator has good estimation accuracy, and the sensorless control system of the BL-IM based on flux estimation not only has good self-detection ability of rotor radial displacement, but also has good speed characteristic and suspension properties.

An MRAS Speed Observer Based on dq-axis Power Winding Flux for Sensorless Control of Standalone BDFIGs

This paper addresses a new mechanical rotor speed observer for sensorless control of standalone Brushless Doubly-Fed Induction Generators (BDFIGs) based on the dq axis power winding flux Model Reference Adaptive System (MRAS) observer. The observer is integrated in the control method for control the terminal frequency and voltage magnitude under various work conditions. The efficiency of the proposed observer and control strategy is proved by overall simulation results and confirmed by experiments. As illustrated without using physical rotor speed sensors, the sensorless control strategy integrating the proposed speed observer can keep effectively the frequency and amplitude of power winding voltage fixed at various rotor speeds and under various conditions of machine parameter and load changes.

Synthetic Sensorless Control Scheme for Full-Speed Range of Switched Reluctance Machine Drives With Fault-Tolerant Capability

In this article, a synthetic sensorless control scheme for full-speed range of switched reluctance machine (SRM) drives with phase absence fault-tolerant capability is proposed, which integrates the phase inductance gradient detection and the idle phase inductance threshold comparison. First, in each excitation period, only the demagnetization inductance slope negative-going zero-crossing detection (D-ISNZ) is performed to avoid the erroneous aligned position estimation in the main excitation region. Then, considering the sensitivity of the D-ISNZ method to demagnetization regions, the remedial sensorless control strategy based on single inductance threshold (SIT) is adopted. Also, the synthetic algorithm is developed for the seamless combination between the two sensorless methods. To enhance the reliability of sensorless operation, a fault-tolerant rotor position estimation method considering speed transient and phase deviation compensation is also presented. Furthermore, to ensure stable sensorless starting, a commutation instant direct estimation method based on online determined double inductance thresholds is developed. The proposed sensorless control scheme can achieve robustness operation under various working conditions without any prior knowledge of magnetic characteristics, large storage memory occupations, and intensive computations. Experiments are conducted on a three-phase 12/8 SRM experimental setup to verify the feasibility of the proposed sensorless control scheme.

High-Frequency Square-Wave Signal Injection Based Sensorless Fault Tolerant Control for Aerospace FTPMSM System in Fault Condition

To enhance position detection reliability, this article proposes a new high-frequency square-wave signal injection (HFSWSI) based sensorless control for aerospace fault tolerant permanent magnet synchronous motor (FTPMSM) drives, which can be configured as the nonsimilar redundancy for a physical sensor. The novel sensorless control scheme with HFSWSI in two nonfault windings is first proposed for the FTPMSM system under each phase current independent control frame, which is free of the coordinate transformation. The HFSWSI-based position detection is then proposed for rotor position estimation via HF response currents even in phase open-circuit fault (OCF) and short-circuit fault (SCF) conditions. To enhance the dynamic performance, a novel dual-output filter is proposed for the fundamental and HF response current component extractions with almost no phase lag. To guarantee the fault tolerant performance, the optimal torque control (OTC) is utilized to ensure that the FTPMSM system generates the ripple-free torque even in fault condition. The resulting sensorless FTPMSM system has outstanding low-speed sensorless control performance both in normal and fault conditions, which is also experimentally validated on a six-phase FTPMSM platform.

An Enhanced Sensorless Control Scheme for PMSM Drives Considering Self-inductance Asymmetry

Inductance asymmetry, which is brought by inherent asymmetric parameters, manufacture tolerance, winding fault, cables with unequal lengths, etc., of permanent-magnet synchronous machines (PMSMs) can cause current harmonics and inaccurate position estimation. This paper proposes an enhanced fundamental model based sensorless control strategy for PMSMs with asymmetric inductances. The proportional-integral-resonant current regulator is introduced to reduce the second-order harmonics of currents, but there are still negative sequence components in the estimated back-electromotive forces (EMFs), which can cause the position estimated error. Differing from conventional methods in which negative sequences are filtered out before the phase-locked loop (PLL) module, the proposed method directly applies the estimated back-EMF with negative sequences as the reference input of PLL. An improved PLL with a bi-quad filter is proposed to attenuate the arising second harmonic position error and heighten the steady-state accuracy. Then, this position error is used for asymmetric inductance identification and its result is utilized to update the observer model. Furthermore, the dynamic performance is improved by the output limitation on the bi-quad filter as well as the implementation of a fast-locking technique in the PLL. The effectiveness of the proposed scheme is verified by experimental results.

PMSM Speed Sensorless System of Intercity Railway Track Inspection Trolley Based on FOSMO-MRAS Observer

For realizing the speed sensorless control system of the intercity railway track inspection trolley, reducing the manufacturing cost and volume weight of the track inspection trolley, and improving the performance of the three-phase permanent magnet synchronous motor (PMSM) control system inside the track inspection trolley, a new fractional sliding mode variable structure model reference adaptive (FOSMO-MRAS) method is proposed to construct the motor speed observer, and a new sliding mode approach law is constructed by using a hyperbolic tangent function instead of a traditional discontinuous switching function. The simulation results show that the speed sensorless control strategy of PMSM based on the FOSMO-MRAS observer has good dynamic and static performance. And the robustness and reliability of the system are improved.

A coordinated control method for static PV model fed pump motor system under rapid irradiation drop

AbstractPhotovoltaic (PV)‐fed motor pump system employs an advanced system that eliminates the need for batteries to reduce maintenance and equipment costs during the day in desert areas. Real‐time adjustment of the motor output speed stops the motor from drawing power from a storage capacitor in the DC link so that sensors and microcontrollers (MCU) do not lose power and restart. This paper proposes an extremum seeking control (ESC) to achieve high accuracy of the maximum power point tracking (MPPT) algorithm by improving the accuracy of current and voltage measurements. MPPT‐based motor speed vector control rule is proposed. A field‐oriented control (FOC) scheme and sensorless direct torque control (DTC) scheme are introduced for comparison. The control method and interior permanent magnet synchronous motor (IPMSM) are tested on the PV simulator and dynamometer experimental test‐rig. The test results show that the sensorless DTC can regulate the motor speed and torque to the desired value without system power failure. In contrast, the speed fluctuation of FOC control is lower than sensorless DTC. However, the system tuning time of DTC is faster and easy to support the whole system operation. The main technical contribution of this study is to provide a coordinated control method to maintain the continuous operation of the entire system during the daytime.

A novel nonsingular fast terminal sliding mode observer combining I‐F method for wide‐speed sensorless control of PMSM drives

AbstractBased on the consideration of optimizing speed piecewise and transitioning smoothly, a hybrid position sensorless control strategy integrating with a novel nonsingular fast terminal sliding mode observer (NFTSMO) and the current‐frequency (I‐F) control method for surface‐mounted permanent magnet synchronous motor (PMSM) is proposed in this paper. In zero‐low speed regions, the I‐F control method is employed for starting steadily and possessing the ability of anti‐interference. In middle‐high speed regions, an improved sliding mode observer (SMO) based on a novel nonsingular fast terminal sliding surface is designed for the closed‐loop sensorless operation. Making use of the novel sliding surface, not only the estimated errors of rotor position caused by the conventional sliding surface can be eliminated effectively with a faster rate of convergence to improve the stability of system, but also the chattering of the estimated back EMF can be restrained by the sigmoid function. Meanwhile, the phase‐locked loop is utilized to lessen the burden of calculation and phase delay. Furthermore, a transition function is designed so as to fulfill the smooth transition between two different control ideologies. The effectiveness of the proposed hybrid sensorless control strategy for both dynamic and steady state operations during wide‐speed region is verified by simulation and experimental analyses.

Novel Random Square-Wave Voltage Injection Method Based on Markov Chain for IPMSM Sensorless Control

The square-wave voltage signal injection into the estimated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis is an effective and novel sensorless control scheme for interior permanent magnet synchronous motor at zero speed and low speed. However, the notable acoustic and electromagnetic noises induced by the conventional fixed-frequency signal injection are very harsh and shrill to hear, which limits the practical application. Aiming at reducing unnecessary acoustic noise, a novel random voltage injection method based on the Markov chain (MC) is proposed in this article. Two high-frequency square-wave voltages with different types of frequencies and amplitudes are randomly injected into the estimated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis by MC rules, and this way has spread spectrum characteristics, which can effectively reduce the unnecessary noise. In addition, a new signal demodulation compensation method considering the digital delay effect in high-frequency signals is proposed, which effectively reduces the position and velocity estimation errors. Then, the power spectra density of the induced high-frequency currents under the fixed frequency injection method and the proposed MC method are compared and analyzed. The high performance of the proposed MC method has been validated by the experiment drive platform and compared with the traditional fixed frequency under different control conditions.

A Two-Degree-of-Freedom Structure-Based Backstepping Observer for DC Error Suppression in Sensorless PMSM Drives

The back-electromotive force (BEMF) model-based observer is an attractive sensorless control strategy for permanent magnet synchronous motor (PMSM) drives. However, the accuracy of BEMF observer is deteriorated due to the dc offsets caused by current measurement and inverter nonlinearity. To address this problem, the article proposed a two-degree-of-freedom structure-based backstepping observer (TSBO) for sensorless PMSM drives. First, a two-degree-of-freedom structure is presented to improve the frequency-domain response of the BEMF observer. Second, a second-order complex vector transfer function is inversely introduced into the studied structure to achieve bandpass characteristics. Compared with the conventional BEMF observer, the studied TSBO can achieve dc error suppression without introducing the extra bandpass filter. The studied algorithm is verified by the experimental results on a 4.4 kW PMSM platform.

A Sensorless Control Strategy of Injecting HF Voltage Into d-Axis for IPMSM in Full Speed Range

This article presents a sensorless control strategy by injecting high-frequency (HF) voltage into the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">d</i> -axis for the interior permanent magnet synchronous motor (IPMSM) in the full speed range. The defined quadratic virtual back electromotive force model can be adopted in the full speed range, and thus, there is no need to design a transition algorithm from the zero–low speed to the medium–high speed. Besides, the accurate model of IPMSM is applied to eliminate the error caused by ignoring the stator resistance. Furthermore, the estimation error caused by the filter and system delay during demodulating the HF current in the conventional HF voltage injection method is avoided. Compared with the method of injecting HF voltage into the <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">q</i> -axis, the proposed method has smaller torque ripple and smaller injected voltage. The effectiveness of the proposed method is verified by experimental results.

A current sensorless control method for multi‐level active front‐end rectifiers with LCL filter

AbstractThis paper presents a current sensorless control strategy for a three‐phase multi‐level active front‐end rectifier with an LCL filter. The proposed control strategy is based on the mathematical model of the system. Opposed to the existing control methods that measure three‐phase currents as well as three‐phase voltages, the proposed control eliminates the current measurement requirement which leads to cost reduction. Moreover, unlike the existing current control methods that use two proportional‐integral (PI) controllers, the proposed current control does not use any PI controller in the current loop. The elimination of two PI controllers simplifies the controller design. The resonance damping requirement arising due to the LCL filter is tackled by active damping that is realized by using filter capacitor voltage feedback. The steady‐state and dynamic performances of the proposed control strategy are investigated experimentally under balanced, unbalanced and distorted grid conditions.

Sensorless Control of High-Speed Motors Subject to Iron Loss

It is widely recognized that the iron loss produced by motors at high speeds will directly affect the angle and size of the back electromotive force, and, therefore, it cannot be ignored. In this paper, a high-performance sensorless control algorithm is proposed for high-speed permanent magnet synchronous motors (HSPMSM), taking the iron loss into account. First, the resistance representing the core loss is precalculated by finite element analysis, and then a sliding mode observer with disturbance observation is designed to estimate the rotor position. The observer possesses the advantages of suppressing the chattering phenomenon and enhancing the robustness against uncertainty. Meanwhile, the idea of the characteristic model is used to design an adaptive robust control law to improve the speed control accuracy. Subsequently, a sensorless control scheme is proposed by using the proposed observer in combination with the designed control scheme. The stability of the observer and controller is verified by the Lyapunov theory method. Finally, a simulation example is given to demonstrate the correctness and the effectiveness of the proposed algorithm.

Sensorless Optimal Control Strategy of PMSG in Wind Energy Conversion System

This paper presents a sensorless optimal control strategy of Permanent Magnet Synchronous Generator (PMSG) used in Wind Energy Conversion System (WECS). An approach to develop a simple reduced speed observer for PMSG is developed. The speed and rotor position estimation of the PMSG are obtained by only measuring phase voltage and current. Maximum wind energy extraction is achieved by running the wind turbine generator in variable-speed mode. The rotor speed is allowed to vary in sympathy with the wind speed by maintaining the tip speed ratio to the value that maximizes aerodynamic efficiency. Advantages of this mechanical sensorless control strategy for maximum power estimation are demonstrated by digital simulation of the WECS.