Voltage Pulse Injection Research Articles

Low-Frequency Pulse Voltage Injection Scheme-Based Sensorless Control of IPMSM Drives for Audible Noise Reduction

High-frequency (HF) signal injection has been widely used in the sensorless control of interior permanent magnet synchronous motor (IPMSM) drives for zero- and low-speed operation. However, the audible noise pollution caused by induced HF current has restricted its application. To solve this problem, a low-frequency (LF) pulse voltage injection scheme is proposed in this paper. Different from the traditional LF injection methods, by separating the injection and the control periods, it is easy to extract the fundamental and the induced currents without digital filters, which makes the position estimation more realizable. Since the accuracy of position estimation decreases, an enhanced vector-tracking observer based on the harmonic analysis of the discrete position signal is proposed. Then, the stability of the proposed observer is analyzed. The negative effects of estimation errors on position estimation are investigated, and notch filters are adopted to achieve further harmonic reduction. Finally, this sensorless control method is verified by experiments on a 2.2-kW IPMSM drive platform.

Initial Rotor Position Detection for Sensorless Interior PMSM With Square-Wave Voltage Injection

In order to resolve the starting problem for position sensorless interior permanent magnet synchronous motor, an improved initial rotor position estimation method based on square-wave signal injection is presented in this paper. Instead of the conventional sinusoidal voltage injection, square-wave voltage signals are injected into stator windings to obtain magnet pole position. On the basis of saturation and saliency principle, the voltage pulse injection method was adopted to identify the magnet polarity. Detecting the magnet pole position by using the square-wave voltage injection, the error signal can be calculated without low-pass filters and time delays. The proposed method is verified via a 1.5 kW interior permanent magnet synchronous motor drive platform.

Sensorless Direct Flux Vector Control of Synchronous Reluctance Motors Including Standstill, MTPA, and Flux Weakening

This paper proposes a sensorless direct flux vector control scheme for synchronous reluctance motor drives. Torque is controlled at constant switching frequency, via the closed loop regulation of the stator flux linkage vector and of the current component in quadrature with it, using the stator flux oriented reference frame. A hybrid flux and position observer combines back-electromotive force (EMF) integration with pulsating voltage injection around zero speed. Around zero speed, the position observer takes advantage of injected pulsating voltage. Instead of the commonly used current demodulation, the position error feedback is extracted here at the output of the observer's flux maps, thus resulting in immunity toward the cross-saturation position error. The maximum torque per ampere (MTPA) strategy is used. A detailed analysis puts in evidence the key advantages and disadvantages related to the use of the MTPA in the sensorless control of the synchronous reluctance machine, for both the saliency-based and the back-EMF based sensorless methods. Extensive experimental results are reported for a 2.2 kW synchronous reluctance motor prototype, showing the feasibility of the proposed method. These include speed response to step and sinusoidal load disturbances at standstill, up to 121% of rated torque, and speed response tests covering the flux weakening speed region.

Full Speed Region Sensorless Drive of Permanent-Magnet Machine Combining Saliency-Based and Back-EMF-Based Drive

This paper aims to improve the full speed sensorless drive for permanent-magnet (PM) synchronous machines on the region of initial zero speed and the region of medium speed. At zero and low speed, the saliency-based drive using the square-wave voltage injection has demonstrated the comparable performance to the sensor-based drive using the encoder with hundreds of pulses per revolution. For PM machines at initial state, the magnet polarity is typically identified based on the injection of voltage pulses before the saliency-based drive. Instead of pulses injection, this paper directly adds the polarity detection capability in the saliency-based drive by superimposing the same square-wave voltage. A fast detection period and negligible current spikes are benefits for the drive using the same square-wave injection voltage for both the polarity detection and position estimation. At medium speed, electromotive force voltage can be estimated to replace the saliency for the sensorless drive. To achieve a smooth operation between two estimation methods, a transition algorithm is also proposed based on a single-phase-lock loop by blending two feedback position signals. According to the experimental evaluation, the reduced power consumption as well as the smooth switch between two different drives is achieved. All the sensorless methods are verified by an interior PM machine with a saliency ratio of 1.37 ( $L_{q}/ L_{d}\,= \,1.37$ ).

Sensorless Scheme for Interior Permanent Magnet Synchronous Motors with a Wide Speed Control Range

Permanent magnet synchronous motors (PMSMs) have higher torque and superior output power per volume than other types of AC motors. They are commonly used for applications that require a large output power and a wide range of speed. For precise control of PMSMs, knowing the accurate position of the rotor is essential, and normally position sensors such as a resolver or an encoder are employed. On the other hand, the position sensors make the driving system expensive and unstable if the attached sensor malfunctions. Therefore, sensorless algorithms are widely researched nowadays, to reduce the cost and cope with sensor failure. This paper proposes a sensorless algorithm that can be applied to a wide range of speed. The proposed method features a robust operation at low–speed as well as high–speed ranges by employing a gain adjustment scheme and intermittent voltage pulse injection method. In the proposed scheme the position estimation gain is tuned by a closed loop manner to have stable operation in tough driving environment. The proposed algorithm is fully verified by various experiments done with a 1 ㎾ outer rotor–type PMSM.

Design and Sensorless Control of a Novel Axial-Flux Permanent Magnet Machine for In-Wheel Applications

This paper proposes an axial-flux-modulation permanent magnet (PM) machine and its sensorless control strategy for in-wheel application in electrical vehicles. A Vernier structure is integrated with the axial-flux PM machine to include the magnetic gear effect and improve output torque. The sensorless control strategy of the proposed machine, including initial rotor position estimation and rotating position estimation, is proposed for flux-modulation motors in this paper. The initial rotor position estimation is based on the technique of rectangular pulse voltage injection and the rotating rotor position estimation is based on the sliding mode observer (SMO). The saturation effect on inductances, which is the theoretical basis of the rectangular pulse voltage injection, makes the stator parameter variation in different loads and affects the SMO estimation. To overcome this problem, a novel online parameter self-adjustment procedure for the SMO is introduced. The machine design and its sensorless control performance are verified by simulation and prototype experiments.

Position estimation of linear switched reluctance machine with iron losses based on eddy‐current effect

The voltage pulse injection method (VPIM) is widely employed in the sensorless control of switched reluctance machines (SRMs) and linear SRMs (LSRMs) at the starting and low-speed operations. However, the existing iron losses in SRMs/LSRMs will lead to the distortion of the phase currents, especially in the VPIM, and will in turn affect the accuracy of estimated results. This study presents a novel mover position estimation method for the LSRM based on the eddy-current effect. The effects of the eddy-currents on the phase currents and winding terminal voltages are discussed, and the equivalent eddy-current resistance model is presented through the finite element analysis. Furthermore, the eddy-current resistance and LSRM magnetic circuit are analysed, obtaining that the positions vary monotonically along with the differences between the rising time and falling time of the response pulse currents. On the basis, the starting and low-velocity operation methods are proposed. A designed double-sided LSRM test platform is established, and the proposed methods are verified by the experimental results.

Unbalanced normal force reduction in the eccentric double‐sided linear switched reluctance machine

This paper presents a novel control method for unbalanced normal force (UNF) reduction in the eccentric double-sided linear switched reluctance machine (DLSRM). Online detection of the DLSRM eccentricity is investigated via magnetic circuit analysis as well as finite element method. It is shown that the DLSRM eccentricity is directly proportional to the difference between reciprocal values of winding unsaturated inductances on both sides of the DLSRM mover. In order to improve the accuracy of the eccentricity detection, a new scheme to estimate the winding inductances is proposed on the basis of the voltage pulse injection considering iron losses in the test DLSRM in the laboratory. Afterward, a control algorithm for the UNF reduction, according to the estimated real-time eccentricity, is designed, and the corresponding power converter and flow chart are illustrated in detail. To verify the proposed methods, a prototype experimental platform is developed, and the experimental results confirm that the proposed methods in this study are feasible and effective.

Inductance estimation method for linear switched reluctance machines considering iron losses

The voltage pulse injection method is widely used at the starting and low-speed sensorless operation of the rotary switched reluctance machine (SRM) and the linear SRM (LSRM). The conventional methods for the inductance estimation in voltage pulse injection, the current peak value method, and the current slope difference method have a limitation that the iron losses in the controlled SRMs/LSRMs should be negligible. In this study, a new inductance estimation method in the voltage pulse injection is proposed considering the iron losses. Assuming that the iron-loss currents in the energising and de-energising intervals are almost equal, the inductance estimations in the two intervals are conducted, respectively, and the actual inductance values without the influence of the iron losses can be obtained by a special operation of the two calculated inductance values. Take a designed LSRM as a test object, the results of the proposed method coincide well with the actual values as compared with the conventional methods. The novel inductance estimation can be utilised in the SRMs/LSRMs without the limitation of the iron losses, and then it can further improve the accuracy of the sensorless control in the voltage pulse injection method.

Sensorless Speed Control with Initial Rotor Position Estimation for Surface Mounted Permanent Magnet Synchronous Motor Drive in Electric Vehicles

The accurate information of the initial rotor position is very critical for successful starting of the Surface-mounted Permanent Magnet Synchronous Motor (SPMSM). In order to solve the problems of low accuracy and unreliability in the conventional estimation strategy, in this paper, an improved initial rotor position estimation strategy without any position sensor for SPMSM at standstill is proposed based on rectangular pulse voltage injection. In the work, when the second series of pulse voltages were applied. By the ways of strengthening the effect of weakening or strengthening magnetic fields and increasing the difference between each current of the vector. The improved strategy enhanced reliability and raised the initial position estimation accuracy from 7.5° to 1.875°. The improved strategy does not need any additional hardware. Experimental results demonstrate the validity and usefulness of the improved strategy.

A Pulse-Injection-Based Sensorless Position Estimation Method for a Switched Reluctance Machine Over a Wide Speed Range

In this paper, a pulse-injection-based method for determining the rotor position of a switched reluctance motor (SRM) over its entire speed range is presented. In this method, a single high-frequency pulse is injected in an idle phase to determine the rotor position at high speeds. The proposed method estimates the rotor position through analysis of the resultant current after voltage pulse injection. A low-speed sensorless method previously developed based on pulse injection has also been extended to improve robustness against varying operating conditions. The developed pulse injection with varying duty ratios provided uniform sensing thresholds over varying dc bus voltages. The low- and high-speed methods are integrated together to provide a robust wide-speed-range rotor position estimator for SRM.

Initial Position Estimation for IPMSMs Using Comb Filters and Effects on Various Injected Signal Frequencies

This paper proposes fast initial position estimation of IPMSMs (Interior Permanent Magnet Synchronous Motors), which is based on intentional pulse voltage injection and comb filters. Most initial position estimation methods utilize the amplitude or differential values of high-frequency currents and the performance of sensorless control depends on the algorithm to reconstruct these values. Although Fourier series expansion which requires some Low-Pass Filters(LPFs) is utilized in general, the filters degrade the response of position estimation. This paper focuses on the algorithm for initial position estimation of IPMSM at standstill, and proposes a new algorithm using comb filters which can rapidly calculate amplitude values of high-frequency currents and can improve the initial position estimation performance. In addition, this paper experimentally shows the performances of the initial position estimation, starting characteristics of sensorless control and characteristics of sensorless control including standstill under the load.

Sensorless initial rotor position identification for non‐salient permanent magnet synchronous motors based on dynamic reluctance difference

Due to the equivalence between the d-axis and q-axis static reluctance in non-salient permanent magnet synchronous motors (PMSMs), the traditional saliency-tracking self-sensing strategies appear powerless for rotor position identification. However, the nonlinear magnet saturation characteristic results in much larger d-axis dynamic reluctance than that in q-axis, then two novel methods based on the dynamic reluctance difference are proposed for sensorless initial rotor position detection. In the high frequency rotating voltage injection method, the positive-sequence and negative-sequence second-harmonic carrier current components are used to estimate two pre-angles simultaneity and separately, where the final estimated rotor position is calculated with the offset angle caused by q-axis dynamic reluctance eliminated. In the high frequency pulsating voltage injection method, the cosine second-harmonic carrier current component contains rotor position and magnet polarity information. The position signal is employed to estimate the possible pre-angles from three symmetrical and equidistant initial estimated angles respectively, where the pre-angle with the largest and negative polarity signal is the final estimated rotor position. Both methods can accomplish the rotor position estimation without an additional polarity detecting process. The simulation and confirmatory experimental results on a surface-mounted PMSM demonstrated the proposed methods can estimate initial position reliably and fast at standstill.

Low voltage pulse injection test of a single-stage 1 MV prototype induction voltage adder cell.

Low voltage pulse injection tests have been done on a 1 MV prototype induction cell. The tests mainly aim at measuring azimuthal uniformity of feed currents and evaluating cell electrical parameters. Tests are conducted under two cases that the cell is fed by a single pulse and two pulses, respectively. The results indicate that, in the case of the single-point feed, the best current uniformity with an azimuthal variation of 19.3% is acquired when azimuthal lines connect to cathode plates with lower half circumferences. In the case of two-pulse synchronous feed, the current uniformity becomes better, and a current with an azimuthal variation of 11.8% is achieved. Moreover, the effects of asynchronous feed on current uniformity are also experimentally investigated. The results imply that, for given injecting pulses with the duration of 70-80 ns, a time deviation less than 30 ns could be acceptable, without obvious degradation on the feed uniformity and current addition. In addition, the influences of the current uniformity and amounts of feed pulses on cell equivalent inductances are evaluated. The experiment results show that, the equivalent inductance would nearly keep a value of 130 nH as the current variation is less than 50%. However, the extreme asymmetry of feed currents or the increase of amounts of feed pulses would produce additional inductance.

Impact of PLL Parameters Variation on the Pulsating Voltage Injection Technique Based PMSM Position Estimation at Low Speeds

This study highlights the impact of an universal Phase Locked Loop (PLL) parameters variation on PMSM position estimation at low speeds. Indeed, the PLL parameters variation impact on the PMSM rotor position estimation performance and robustness cannot be neglected anymore. For this purpose, the study presents the theory and simulation results of a demodulation scheme applied to Sensorless PMSM control based on the Pulsating Voltage Injection (PVI) technique. Comprehensive simulations, carried out under MATLAB/SIMULINK®, are discussed according to the variation of the PLL proportional and integral parameters.

ANALYSIS AND SIMULATION STUDIES FOR THE ESTIMATION OF ROTOR POSITION IN SENSORLESS BLDC

Initial rotor position information is essential for brushless dc motor in order to ensure its stable operation. A simple method for determining the initial rotor position of a sensor less brushless dc motor at standstill is discussed in the paper. The principle behind the rotor position estimation is based on simple detection and comparison of phase voltages and dc link current responses thus relating it with stator inductances. The advantage of this method of estimation of rotor position is that it requires only three voltage pulse injection, and a resolution of 30o is achieved. Moreover no other parameters of the machine are required. The effectiveness of the method is validated by simulation results in Matlab Simulink platform.

New Sensorless Vector Control of PMSM by Pulsating Voltage Injection of PWM Carrier Frequency

New Sensorless Vector Control of PMSM by Pulsating Voltage Injection of PWM Carrier Frequency

Sensorless Control of PMSM Fractional Horsepower Drives by Signal Injection and Neural Adaptive-Band Filtering

This paper presents a sensorless technique for permanent-magnet synchronous motors (PMSMs) based on high-frequency pulsating voltage injection. Starting from a speed estimation scheme well known in the literature, this paper proposes the adoption of a neural network (NN) based adaptive variable-band filter instead of a fixed-bandwidth filter, needed for catching the speed information from the sidebands of the stator current. The proposed NN filter is based on a linear NN adaptive linear neuron (ADALINE), trained with a classic least mean squares (LMS) algorithm, and is twice adaptive. From one side, it is adaptive in the sense that its weights are adapted online recursively. From another side, its bandwidth is made adaptive during the running of the drive, acting directly on the learning rate of the NN filter itself. The immediate consequence of adopting a variable-band structure is the possibility to enlarge significantly the working speed range of the sensorless drive, which can be increased by a factor of five. The proposed observer has been tested experimentally on a fractional horsepower PMSM drive and has been compared also with a fixed-bandwidth structure.

Analysis of Stator Resistance Effects in Carrier Signal Injection Based Sensorless Control of Permanent Magnet Synchronous Machine

This paper analyzes the effects of stator resistance on rotor position estimation accuracy in carrier signal injection based sensorless control of PMSM. Carrier current expressions are derived for both rotating and pulsating voltage injection method when the stator resistance is taken into account. Position estimation errors resulted from stator resistance are analyzed theoretically and investigated by simulation. It is shown that the influences of stator resistance on above two injection methods are quite different. The stator resistance will result in a position estimation error in the rotating voltage injection method. But it does not affect the position estimation accuracy in the pulsating voltage injection method as long as a suitable signal extracting method is used.

End Effects in Linear Tubular Motors and Compensated Position Sensorless Control Based on Pulsating Voltage Injection

The sensorless position control of permanent-magnet (PM) synchronous motors can be successfully implemented by superimposing a high-frequency voltage signal on the control voltage. In this paper, the position estimation is obtained by means of a high-frequency sinusoidal voltage signal injected along the estimated -axis. Several methods proposed in the literature obtain the position estimation by tracking the zero condition of the high-frequency current component. We propose a new approach that also exploits the -axis high-frequency current component and allows working with injected voltage signal of reduced amplitude, thus reducing noise and additional losses. The main contribution of this paper relies in the compensation of the motor end effects due to the finite length of the tubular motor armature. These effects must be taken into account in the motor modeling because they cause an error in the position estimation that varies with the motor position. The modeling of the phenomenon and a proper compensation technique are proposed in this paper. Last, a simplified integral-type controller is used to estimate motor position instead of the commonly adopted proportional-integral controller plus integrator, and this requires a low-effort design. Experiments on a linear tubular PM synchronous-motor prototype are presented to validate the theoretical analysis and evidence the feasibility of the proposed sensorless technique.