Initial Rotor Position Research Articles

Influence of DC-Field Current on Short-Circuit Current in Variable Flux Reluctance Machine

DC-field windings of variable flux reluctance machine are wound on the same teeth with armature winding, which increases the short-circuit probability among the armature and field windings. Therefore, in this article, the various short-circuit faults of single phase, phase-to-phase, single field and phase-to-field are illustrated, and the influence of dc-field current on short-circuit current (SCC) and braking torque (BT) with consideration of initial rotor position are investigated. The SCC with dc-field current is analytically established, where the SCC and BT in transient and steady states are analyzed. The maximum SCC and BT are comprehensively compared by finite element method. It is found that the influence of dc-field current on the SCC and BT under transient conditions can be neglected. However, when the machine under un-saturated conditions, the SCC in steady states is associated with the saturation of iron core, i.e., the more saturated of the core excited by dc-field current in prefault, the smaller of the SSC in post fault. Both the SCC and BT are accompanied by the 12/14-pole VFRM prototype experimental verification.

A Novel Phase Current Difference Construction Based Initial Rotor Position Detection Method for Surface Mounted PMSM Without Injections of High-Frequency Voltage or Pulse Sequence

A Novel Phase Current Difference Construction Based Initial Rotor Position Detection Method for Surface Mounted PMSM Without Injections of High-Frequency Voltage or Pulse Sequence

Zero-Sequence Voltage Error Elimination-Based Offline VSI Nonlinearity Identification for PMSM Drives

The offline inverter nonlinearity identification is a useful method to deal with the inverter nonlinearity effect in machine drive. However, the conventional methods can only be achieved at particular initial rotor position, which reduces the application universality. Meanwhile, it is revealed in this paper that the zero-sequence voltage error exists in the zero-axis voltage, which reduces the identification accuracy and has rarely been investigated. To solve the above problems, an offline inverter nonlinearity identification scheme applicable at arbitrary initial rotor positions is proposed, where the zero-sequence voltage error is fully considered. In this paper, the characteristics of zero-sequence voltage error at different rotor position cases is fully investigated by the theoretical analysis for the first time. The offline identification approach at different rotor position cases is then introduced, with the zero-sequence voltage error eliminated. Finally, the second order Newton interpolation polynomial (NIP) based fitting strategy is proposed to reduce the calculation complexity. The proposed method is validated on a 2.2kW permanent magnet synchronous motor (PMSM) platform.

Research Review on Sensorless Measurement Technology of Permanent Magnet Synchronous Motor

Permanent magnet synchronous motor (PMSM) has the advantages of high torque/inertia ratio, high power factor, fast dynamic response speed and high reliability, and has been widely used in various high-precision AC drive systems. Incremental encoders are usually used to achieve high precision position feedback information for permanent magnet synchronous motors. The use of sensors leads to cost increase, volume increase and reliability reduction. Therefore, the sensorless measurement technology of permanent magnet synchronous motor is more and more concerned and applied by industry and research fields. In this paper, the related literature of sensorless measurement technology of permanent magnet synchronous motor is investigated, and the sensorless measurement technology is comprehensively reviewed. This paper introduces in detail the basic principle of various sensorless measuring techniques, the accuracy of position measurement and the application in the type of permanent magnet synchronous motor. In this paper, the concept of speed pole logarithm ratio is proposed to divide the speed region, and the initial rotor position, low speed and medium speed non-inductive measurement methods are described and compared. Finally, the non-inductive measurement accuracy of permanent magnet synchronous motor is summarized.

Enhanced Volts-per-Hertz Sensorless Starting of Permanent Magnet Motor with Heavy Loads in Long-Cable Subsea Applications

Permanent magnet (PM) motors are gaining prominence in subsea applications such as drilling, pumping, and boosting for oil and natural gas extraction. These motors are gradually replacing traditional induction motors. However, starting and operating PM motors at low speeds under heavy loads poses significant challenges. This is because of unknown initial rotor positions and resistive voltage drops due to the presence of a sinewave filter, transformer, and long cable. An unknown rotor position may result in temporary reverse speed, which may cause a loss of synchronism; therefore, initial rotor position estimation is preferable. Additionally, addressing the voltage drop issue requires careful voltage compensation to avoid transformer core saturation. In this paper, an enhanced V/Hz starting of a PM motor is proposed with initial position detection (IPD) and voltage compensation to start the motor reliably with a heavy load. The proposed control method is verified with controller hardware in the loop (C-HIL) real-time simulation using a Typhoon HIL-604 emulator and a Texas Instruments TMS320F28335 digital signal processor (DSP) control card.

Adaptive-Based Accurate Rotor Initial Position Estimation in Synchronous Reluctance Motors

Adaptive-Based Accurate Rotor Initial Position Estimation in Synchronous Reluctance Motors

Online position error correction technique for sensorless control of multipole permanent magnet machines

In order to improve the reliability of electric machine drive systems, the position encoder is often replaced with an estimator, such as the extended Kalman filter. However, estimation errors can still occur, especially in machines with high pole number, commonly used in renewable energy systems. The high number of pole pairs amplifies the effect of estimation errors, leading to a substantial divergence between actual and controlled currents, potentially causing harm to the machine through the excessive heat generation or demagnetization of permanent magnets. To address this issue, an error compensation method has been proposed and tested in a control scheme for a tidal stream system based on a multipole dual-star permanent magnet synchronous generator. The method estimates the position error by determining the q-axis permanent magnet flux and correcting it through a PI regulator. Simulation results demonstrate the effectiveness of the proposed method, even with a non-null initial rotor position.

A High Precision Initial Position Estimation Method for Low Saliency Ratio Machine Based on Image Tracking

In sensorless control of permanent magnet synchronous motor (PMSM) drives, initial rotor position detection is critical to ensure smooth start-up operation. However, extracting initial position information for machines with ultra-low saliency ratios is challenging. To address this issue, this paper proposes an estimation method for rotor position using image tracking based on high-frequency (HF) rotating voltage vector injection. Specifically, this paper extracts positive- and negative-sequence currents in the stationary reference frame and reconstructs the induced current vector. By utilizing the support vector machine (SVM) algorithm, the resulting current vector images, which contain amplitude and phase information of the position, are trained to establish the correlation between the current image and rotor position information. Ultimately, the electric position can be obtained from image recognition. Since this method employs image tracking for position estimation, it accounts for cross saturation and multiple saliencies, leading to the relatively high precision of position estimation. Experimental evaluation shows that the proposed method achieves higher precision compared to conventional observers.

High-Reliability Rotor Position Detection Method for Sensorless Control of Synchronous Condenser

Static frequency converters (SFCs) are very important for starting the connection of synchronous capacitors to the power grid, which is beneficial for ensuring the impact of electric vehicle connection on the inertia of the power grid. In the traditional sensorless initial rotor position detection method, the signal-to-noise ratio of the induced voltage at the machine terminal is small, making it difficult to accurately extract the rotor position. In this study, a reliable initial position detection method for a sensorless-controlled synchronous machine drive is proposed. A step excitation voltage was applied to the excitation circuit before the motor was started, and the three-phase induction voltage at the terminals was sampled in real time. The sampling signal was processed in two ways: digital filter processing and stator flux calculation. The accuracy of the initial rotor position is determined by comparing the differences between the two results. This algorithm does not depend on additional hardware circuits and has fewer setting parameters; therefore, it is easy to apply in engineering applications. Finally, a comparative experiment was conducted using a real-time digital system (RTDS) to verify the feasibility and effectiveness of the proposed method. The proposed rotor position detection method can effectively improve the detection reliability and ensure the start-up reliability of SFCS.

Rotor Position Estimation Based on Low-Frequency Signal Injection and Estimated Main Field Current for Wound-Field Synchronous Starter/Generator in the Low-Speed Region

Due to reliability problems of mechanical position sensor, rotor position estimation technology is an alternative for the starting control of aircraft wound-field synchronous starter/generator. Reversible saliency and high frequency attenuation characteristics of main machine (MM) may lead to the failure of existing high-frequency signal-based estimation methods. In this paper, low-frequency signal (LFS) injection and novel signal extraction method are combined to estimate rotor position. Firstly, LFS is injected in MM's stator winding, and response signal containing rotor position information is induced in its rotor field winding. Then, the response signal can be extracted from the estimated main field current (EMFC) by band-pass filter. Further, the phase of extracted signal and injected LFS are obtained by two single-phase phase-locked loops (PLL) respectively. Then, the increment of rotor position can be obtained by the two PLLs. Meanwhile, by injecting a specific low frequency square wave, initial rotor position can also be extracted from EMFC, requiring no extra pole identification and phase compensation. Finally, combining initial rotor position and position increment, continuous rotor position of MM can be obtained. Effectiveness of the proposed method are verified by experiments.

An improved initial rotor position estimation method using high-frequency pulsating voltage injection for PMSM

High frequency pulsating voltage injection method is a good candidate for detecting the initial rotor position of permanent magnet synchronous motor. However, traditional methods require a large number of filters, which leads to the deterioration of system stability and dynamic performance. In order to solve these problems, a new signal demodulation method is proposed in this paper. The proposed new method can directly obtain the amplitude of high-frequency current, thus eliminating the use of filters, improving system stability and dynamic performance and saving the work of adjusting filter parameters. In addition, a new magnetic polarity detection method is proposed, which is robust to current measurement noise. Finally, experiments verify the effectiveness of the method.

Initial Rotor Position Estimation of SynRM Based on Pulsating Voltage Injection Combined With Finite Position Set Algorithm

Initial rotor position estimation is the basis of stable starting without reverse rotation; also initial position estimation directly affects the maximum starting torque. DC pulse voltage injection is one of the common methods for estimating the initial rotor position, which has low implementation complexity. However, the conventional DC voltage pulse injection methods, which works through injecting three DC voltage pulses, has low accuracy and slow response in estimating initial position. A rotor initial position estimation method based on pulsating voltage injection combined with an iteration algorithm is proposed in this paper. This method works by injecting only one DC voltage pulse to the motor and measuring the peak values of currents and fluxes of the motor; afterwards these values should be applied to an iterative algorithm. The iteration algorithm in the proposed method leads to increment of the accuracy of initial position estimation, and reduction of the number of injected dc pulses in comparison with the conventional methods. The performance of the proposed method is verified experimentally on a synchronous reluctance motor (SynRM). Also, a comparison between the two conventional methods and the proposed method is provided by this SynRM drive experimental setup.

Initial Rotor Position Detection of SPMSM with High-frequency Signal Injection

The accuracy of initial rotor position detection is important for senseless control, meanwhile, high frequency signal injection takes its advantages for its simple principle, small calculation amount and good real-time performance. In this paper, the principle of high frequency signal injection is analysed and systematically studied from position information error reading and the direction of d-axis. Besides, factors which may lead to the error of position information error reading is also studied, the second-order notch filter is added to get higher accuracy. Finally, the model of high frequency signal injection is set up to verify the effectiveness of the method, the result shows that method can run well at 0 speed and effectively estimate the actual rotor position.

First-Order Model Based Inductance Identification With Least Square Method for High-Speed Sensorless Control of Permanent Magnet Synchronous Machines

In sensorless control of high-speed permanent magnet synchronous machines (PMSMs), online inductance identification techniques can be employed to improve the position estimation precision. The high-order inductance identification model which is affected by the flux error, the dead-time effect equivalent voltage and initial rotor position error adopted in conventional methods often face challenges including robustness and accuracy. To address this issue, this paper uses a first-order discrete-time model in the estimated <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">γδ</i> -frame to identify the winding inductance with disturbance injection. The first-order model allows the identification to be independent of flux error, initial rotor position error and inverter nonlinearity, thus the robustness is improved. The proposed method takes the computational delay and discrete-time nature of pulse-width-modulation into account to avoid the model error brought by low ratio of carrier-to-fundamental-frequency. Additionally, the results are estimated by least square method to solve fluctuation problem caused by measurement noise and the possible surge phenomenon. Experiments are carried out on a high-speed surface-mounted PMSM for vacuum cleaner to verify the proposed method.

Rotor Position Estimation Method Based on Harmonic Signal for a Wound-Field Synchronous Starter/Generator in the Low-Speed Region

During on-load starting process of an aviation wound-field synchronous starter/generator system, accurate rotor position information is required. Mechanical position sensor is susceptible to interference, increasing volume and weight, so online rotor position estimation is more desirable. Harmonics of main exciter (ME) caused by rotating rectifier are analyzed, and the 5th harmonic is used creatively to estimate rotor position in this paper. In this method, by performing coordinate transformation on stator current of ME, rotor position increment is extracted and obtained through a low-pass filter. Meanwhile, taking advantage of the unidirectional conduction characteristics of rotating rectifier, a new idea to estimate initial rotor position is also proposed. In this approach, pulse signal is injected into the stator winding of main generator (MM) every fixed electrical angle, then the maximum and minimum current response correspond to that of MM's S and N pole respectively. Finally, combine initial rotor position and position increment, continuous rotor position of MM can be gained. The proposed methods avoid dependence on the saliency of MM, require no high-frequency signal injection and do not need secondary magnetic pole identification. Effectiveness and advantages of the proposed method are verified on the test.

Initial Rotor Position Estimation Method for Aircraft Three-Stage Starter/Generator Based on Self-Injected Harmonic Signal

In this article, an initial rotor position estimation method for an aircraft three-stage starter/generator (TSSG) based on self-injected harmonic signal (SIHS) is proposed. Different from the traditional method in which an external high-frequency signal is injected into the stator winding of the main generator (MG), the second harmonic voltage caused by the rotating rectifier in the ac excitation is regarded as the self-injected high-frequency signal into the rotor field winding of MG at standstill. The high-frequency response signals in the stator winding of MG are extracted by a designed bandpass filter (BPF), and the signals orthogonal to the response signals are generated by a cascaded all-pass filter (APF). Then, based on the obtained response signals and orthogonal signals containing rotor position information, a practical approach to estimate the initial rotor position is implemented, where the induced currents in the excitation establishment of MG are detected to identify the polarity of the initial rotor position angle. Finally, the feasibility and effectiveness of the proposed method are verified by simulation and experimental results.

Hybrid sensorless control of PMSM in full speed range using HFI and back-EMF

The permanent magnet synchronous motors (PMSM) are more and more used because of their high performance compared with other AC motors. The present paper proposes a hybrid controller which consists of a high frequency injection estimator and a back-electromotive-force observer in full speed range for the sensorless control of PMSM. The aim objective of the study to prevent speed overshot in startup time of the motor and provides a better dynamic response in transient and permanent states using this structure. A hybrid algorithm is applied to realize a smooth transition from low to high speed. At standstill and very low speed region, HF injection technique is used to detect the rotor initial position. In this first step study, the position estimation is derived from a HF current injection by using only one filter. When the rotor speed goes up to a certain value where back-EMF can provide adequate information, a back-EMF observer will dominate. Thanks to this structure, the mechanical sensor can be engaged using the best estimates and the developed control method is fast, simple, and flexible. The effectiveness, superiority, and performance of the proposed control method and extensive simulation results are provided on a 1 kW permanent magnet synchronous motor drive, demonstrating the expected performances.

Novel Method of Deriving Torque and Speed Curve of the Permanent Magnet Synchronous Motor Using Initial State Finite Element Analysis

This article proposes the novel method of deriving torque and speed curve (TS curve) of the permanent magnet synchronous motor (PMSM) using the initial state finite element analysis (ISF) for the purpose of reducing the high calculation cost of the repetitive finite element analysis (FEA). The ISF is a method that conducts the FEA only for the initial rotor position. As the ISF neglects other periodic parts, the calculation time for analyzing the PMSMs can be drastically reduced. To verify the performance of the proposed method, the ISF and conventional method of full period FEA (FPF) with many steps were applied to three types of the PMSMs, interior PMSM (IPMSM), surface-mounted PMSM (SPMSM), and flux switching machine (FSM). The proposed method reduces the calculation time for deriving the TS curves of the SPMSM, IPMSM, and FSM as 86.35%, 89.39%, and 89.41%, respectively, compared with conventional methods of considering the periodic parts. The analysis accuracies at the operating points of each test models are 94.24%, 99.24%, and 99.86%, and the ISF ensures acceptable accuracy considering the reduced calculation time. Therefore, the ISF can be effectively used when deriving the TS curves of the PMSMs at the early design stage of the motors.

IF 기동방식 센서리스 압축기의 소음 및 진동 저감 제어

This paper presents a simple mechanical vibration and acoustic noise reduction of IF(current-frequency) starting sensorless controlled compressor. The adopted compressor is controlled by the sensorless estimation using back EMF observer in the normal speed range. In order to increase the speed up to normal sensorless speed range, the IF open-loop starting method is used. At the IF starting, the speed variation from the fluid load makes a mechanical vibration and acoustic noise. In order to reduce the mechanical vibration and acoustic noise, a simple variable torque slope with initial rotor position estimation method is proposed in this paper. The proposed method uses an initial rotor position estimation than a conventional rotor alignment method. And, the torque reference slope according to the increased open-loop speed is changed by the hysteresis error between the open-loop reference speed and the estimated speed. Because of the initial rotor position and the variable current according to the speed can reduce the collision of the compressor at standstill and low-speed region. Consequently the mechanical vibration and acoustic noise can be reduced.BRThe proposed simple variable IF starting method is verified 2.2kW IPMSM driven HVAC(Heating, Ventilation & Air conditioning) compressor. Experimental results shows the reduced vibration and acoustic noise at the starting to normal speed range.

A Flying Restart Strategy for Position Sensorless PMSM Driven by Quasi-Z-Source Inverter

The accurate estimation of rotor position and speed before flying restart is of great significance to improve the operation reliability of permanent magnet synchronous motor systems. The traditional multizero vector short-circuit method can improve the estimation accuracy of speed and rotor position, but the increased number of short-circuits reduces the electromagnetic torque response speed after the power supply recovers. In order to accurately estimate the initial speed and rotor position before the flying restart and effectively improve the electromagnetic torque response speed, a shoot-through zero vector short-circuit method based on quasi-Z-source inverter (qZSI) is proposed. This method breaks the limitation of regulating DC link voltage under the normal operation of the motor in the conventional methods, and puts forward a new idea of advancing the regulation of the DC link voltage to the stage of abnormal operation before the motor restarts. By designing the insertion mode of the mixed vectors and analyzing the action time of each vector before the flying restart, the accurate estimation of position and speed is realized and, meanwhile, the boost of the qZSI’s DC link voltage is achieved, thus giving the sensorless flying restart method a faster torque response speed for the PMSM system driven by qZSIs.