Motor Phase Currents Research Articles

Random Switching Period SVPWM Technique with Variable Sampling Frequency for Three‐Phase Power Converters

To improve the pulse width modulation (PWM) harmonic suppression effect of the three‐phase VSI‐fed PMSM system, this paper proposed a novel random switching period (RSP)‐Space Vector Pulse Width Modulation (SVPWM) technique for the three‐phase power converter. First, the proposed technique replaces the 10‐bit linear feedback shift register pseudorandom number generator (LFSR‐PRNG) with a Tiny Mersenne Twister (MT)‐PRNG to quickly generate high‐quality pseudorandom number sequences. Then, to reduce the sampling error caused by the current ripple, this paper analyzes the sampling timing under different modulation techniques. Based on the interrupted update mechanism of the Infineon AURIX‐TC264, the variable frequency sampling of the RSP‐SVPWM technique is implemented to ensure the best sampling of the motor phase current. Finally, the simulation and experimental results show that the proposed technique can effectively disperse PWM harmonic energy. Meanwhile, the RSP‐SVPWM technique based on variable sampling frequency effectively improves the phase current quality of the PMSM system. The proposed technique shows great potential for suppressing PWM harmonics in integrated PMSM systems. © 2023 Institute of Electrical Engineers of Japan. Published by Wiley Periodicals LLC.

Detailed Modeling and In-Situ Calorimetric Verification of Three-Phase Sparse NPC Converter Power Semiconductor Losses

The three-phase three-level (3-L) Sparse Neutral Point Clamped Converter (SNPCC) combines a 3-L matrix stage and a three-phase two-level inverter stage to generate 3-L switched output voltages with a reduced transistor count (10 instead of 12 or 18) compared to the classical 3-L NPCC or 3-L active NPCC structure, targeting variable-speed drive systems with low ripple of the motor phase currents or bidirectional three-phase PFC rectifier systems with reduced boost inductor volume. This paper analyzes and experimentally characterizes the performance of an IGBT-based three-phase 3-L SNPCC converter, and describes for the first time a hybrid current commutation effect between inverter-stage diodes and matrix-stage IGBTs that occurs when operating with lower modulation indices and leads to increased switching losses (up to 20%). The proposed new semiconductor loss modeling approach accounts for this effect successfully, which is verified (< 10% error) on an 800V <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">dc</sub> , 7.5kW SNPCC hardware demonstrator using a new in-situ calorimetric method that facilitates accurate stage-level semiconductor loss measurements. Heat spreading effects caused by the asymmetrical losses injection and thermal decoupling between two in-situ loss measurement blocks are carefully checked with FEM simulations. Further, an experimental evaluation of common-mode and differential-mode high-frequency voltage-time area ripples (as a generic measure for the required filtering effort) for three typical symmetrical and asymmetrical modulation switching state sequences is provided together with the semiconductor loss characterization. Utilizing a low-switching-loss asymmetric modulation scheme that operates the 3-L matrix stage and the 2-L inverter stage with effective switching frequencies of 16kHz and 5.3kHz, respectively, the 3-L SNPCC demonstrator finally achieves a high rated-power (7.5kW, load current phase shift ϕ = 0) semiconductor efficiency of 98.8%.

Flux and Loss Map Based Evaluation of the Efficiency Map of Synchronous Machines

This article presents a methodology for the efficiency maps evaluation of synchronous electric machines. The procedure is based on the manipulation of flux linkage, iron and PM loss maps obtained via 2D magneto-static Finite-Element Analysis. The paper thoroughly describes the procedure and its key computational steps, all referring to open-source Matlab code available to the public. A method for iron loss evaluation from magneto-static FEA is proposed, valid for both sinusoidal and PWM supply. Experimental results are provided for the validation of single loss terms calculation and for the whole efficiency map, with reference to an interior permanent magnet machine designed for traction. FEA evaluation of PWM supply conditions relies on the off-line computation of the motor phase currents using a custom PLECS model of the drive, still flux-map based. This step of the procedure is also validated experimentally. The proposed methodology covers permanent magnet synchronous and synchronous reluctance machines, and finds prominent application in the automotive field, for traction and on-board generation.

Investigation on Torque Sharing Function for Torque Ripple Minimization of Switched Reluctance Motor: A Flower Pollination Algorithm Based Approach

ABSTRACT Switched reluctance motor (SRM) drive has outstanding features like robust construction, double saliency, fault tolerance capability, and heat withstanding capability. Despite these, torque ripple is an intrinsic characteristic of SRM because of double salient geometry, air gap length, and switching sequence of motor phase currents, making it unsuitable for slick torque and high dynamic performances applications. This paper discusses the novel Torque Sharing Function (TSF) implementation and the flower pollination algorithm-based intelligent controller to minimize the torque ripples in Switched Reluctance Motor (SRM). TSF values depend on commutation angles during turn on, turn off, and overlapping angles. The proposed TSF and flower pollination algorithm evaluates the performance parameters using the machine model and controls the torque ripples for a wide range of speeds. Additionally, optimal results are obtained using three TSFs functions with valuable guidance provided for TSF selection. The proposed TSF with flower pollination algorithm-based intelligent controller finds its suitability for online evaluation of optimal turn on, turn off, and overlapping angles. The performance of the proposed method has effectively reduced the torque ripple in SRM than the Differential Evolution (DE) algorithm.

Transfer learning of fuzzy classifiers for optimized joint representation of simulated and measured data in anomaly detection of motor phase currents

The generation of simulation data from physical models trying to mimic parts of the real-world process as accurately as possible has received much attention in industry during the last years. A proper augmentation of simulation data with (available or recordable) real-measured data is an intrinsic challenge to increase the performance of machine learning models. In this paper, we propose a joint representation learning approach based on an optimized transfer of fuzzy classifiers from original simulated data (as source task) to real-measured data (as target task). This is particularly done for binary classification tasks under the scope of anomaly detection of phase currents in electrical machines, where only anomaly-free real-measured data can be collected in advance (so, only in the simulated data anomaly samples are present). Our approach combines distribution matching between simulated and real-measured data on the basis of fuzzy rule activation levels with a weighted error term representing the classification loss between anomaly-free and anomaly data. Both are realized on a local basis per rule, which yields good flexibility during optimization with respect to the actual local distributions and their positions in the target task and is particularly possible for fuzzy classifiers due to the local geometric interpretation of the rules. We demonstrate how to find a feasible initial solution for the numerical optimization process. Results on data sets from the application showed significantly improved classification accuracies of up to 25% compared to several conventional fuzzy classifiers training variants and also compared to various renowned machine learning classifiers, while a respectful (slightly worse) performance compared to the two top performers (SVMs and deep MLPs) were achieved. However, a large performance gap between conventional fuzzy classifiers and these ML-based top performers could nearly be closed and due to the local geometric interpretation of the internal fuzzy partitions, explainable insights into the model transfer could be yielded to experts.

A Nine-Level Inverter With Single DC-Link and Low-Voltage Capacitors as Stacked Voltage Sources With Capacitor Voltage Control Irrespective of Load Power Factor

This paper proposes a multilevel inverter topology with a single DC-link and series-connected capacitors as stacked voltage sources for multilevel voltage generation. The voltage deviation of a DC-link capacitor will occur whenever a phase terminal connects to the balanced neutral points (NPs: terminal joints of DC-link capacitors). On the contrary, if the voltage of a DC-link capacitor deviates from the nominal voltage, the same phase currents can be utilised to balance these neutral points. This new technique is being proposed for the first time in literature. Any voltage disturbance of the DC-link capacitors is balanced using the motor phase currents, irrespective of load power factor and modulation indices. For the balanced neutral points, whenever a phase connects to a neutral point, the other phase terminal tapping positions are varied on the DC-link to establish <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$i_{A}+i_{B}+i_{C}=0$</tex-math></inline-formula> for that neutral point. The pole voltage level variation at motor phase terminals is undisturbed by adding extra cascaded H-bridges (CHBs) at each phase leg. The voltages of CHB capacitors are controlled conventionally by inverter pole voltage redundancies. The detailed experimental results for open-loop V/ <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">f</i> and closed-loop field-oriented control on an induction motor are presented using a nine-level laboratory prototype.

A novel direct torque and flux control of permanent magnet synchronous motor with analytically-tuned PI controllers

&lt;span lang="EN-US"&gt;This work presents a novel direct torque and flux control (DTFC) of permanent magnet synchronous motor (PMSM) with analytically-tuned proportional integral (PI) controllers. The proportional (K_p) and integral (K_i) gains of the PI controllers were accurately determined, from first principle, using the model of the control system. The PI flux and torque controllers were then developed in rotor reference frame. The designed PI controllers, together with the torque and flux controllers, were tested on a permanent magnet synchronous motor (PMSM). The results obtained were compared with results from conventional DTFC system using manually-tuned PI controllers. The total harmonic distortion (THD) of motor phase currents is 18.80% and 4.81% for the conventional and proposed models respectively. This confirms a significant reduction in torque ripples. The control system was tested for step torque loading and found to offer excellent performance both during load changes, speed reversal, and constant load conditions.&lt;/span&gt;

Criteria for Detecting Turn-To-Turn Short Circuit in Stator Windings Using Vector Analysis of Electric Motor Phase Currents

At industrial enterprises, seaports, ships, more than 80 % of all electrical engineering equipment is asynchronous motors. In a number of cases, asynchronous motors operate with a sharply variable load, in an aggressive environment; herewith they receive power from the network with deviations of the power quality indicators from the normative ones, which causes their high damageability. Turn circuits in the stator windings account for about 40 % of cases of damage to the insulation of the asynchronous motors windings. Untimely detection of the initial moment of the appearance of defects in the asynchronous motors or disruption of the operating modes of the supply network and current circuits result in emergency situations of the electrical complex, equipment downtime and damage. The article discusses the issues of diagnostics of non-full-phase modes of current circuits, mains voltages and turn circuits in the stator windings of the asynchronous motors that receiving power from the networks in conditions of voltage asymmetry. The analysis of the vector diagrams of currents, voltages and additional phase angles of the phase currents displacement arising from the asymmetry of the mains voltages and turn circuits in the stator windings has been fulfilled. The results obtained made it possible to formulate criteria for identifying the initial moment of the turn circuit and two-phase modes, both in the network and in current circuits, in stationary modes. A method for non-destructive testing of the asynchronous motors state as well as a device for its implementation has been developed. The method is based on comparing the vectors of the measured phase currents of the asynchronous motors with their calculated values. The article presents the results of modeling the change in the vectors of phase currents from the number of closed turns in the winding of the asynchronous motors. The power series of asynchronous motors was established, for which the sensitivity of detecting the initial moment of the turn-to-turn short circuit is maximum. Analytical results of the dependence of the sensitivity coefficient for turn-to-turn short circuit on the absolute increment of the modules of phase currents and the corresponding phase angles have been obtained.

Drive circuitry of an electric vehicle enabling rapid heating of the battery pack at low temperatures.

SummaryHeating battery at low temperatures is fundamental to avoiding the range anxiety and the time-consuming charging associated with electric vehicles (EVs). One method for achieving fast and uniform battery heating is to polarize the cell under pulse currents. However, the on-board implementation of this method leads to an increase in the cost and size. Therefore, in this study, an adapted EV circuitry compatible with the existing one and an optimized operating condition are proposed to enable rapid battery heating. With this circuit, electricity transfer between the cells can be realized through a motor, leading to remarkably higher battery currents than those of the conventional circuit. The increase in the maximum heating currents (from 1.41C to 4C) resulted in a battery temperature rise of 8.6°C/min at low temperatures. This heating method exhibits low cost, high efficiency, and negligible effects on battery degradation, practical and promising on battery heating of EVs.

Phase Current Sensing Method Using Three Shunt Resistors to Eliminate Immeasurable Area in Voltage Vector Plane

This paper proposes a current sensing method to eliminate the immeasurable areas in three-phase inverters using the shunt resistors. Conventional shunt resistor-based current sensing methods have immeasurable areas in the voltage vector plane. Since motor control performance is degraded by the immeasurable area, various current reconstruction techniques have been proposed to expand the measurement range. Nevertheless, the software algorithm is quite complex, and the reconstruction ability is still unsatisfactory. In the proposed method, shunt resistors are located in series with the inverter output lines to obtain the motor phase currents. Both ends of the shunt resistors are at the high-potential as the dc-link voltage. High-potential voltages are lowered to the common-mode voltage level of the analog amplifier using voltage divider, and voltage drops across shunt resistors are detected by instrumentation amplifiers. Immeasurable areas are completely eliminated because phase currents can be detected directly through line shunt resistors. Simulations and experiments are carried out to verify the effectiveness of the proposed current sensing method.

Improved Dynamic Performance of Permanent Magnet Synchronous Motor using Maximum Torque Per Ampere with reduced number of switches

To attain the excellent dynamic performance of any drive the torque ripples must be as minimum as possible. Otherwise which leads to oscillations in a speed profile and hence results in poor performance of a drive. The proposal of this work is to reduce as minimum as possible in torque ripples of a Permanent Magnet Synchronous Motor (PMSM) by means of a Five Level Space Vector Modulation (SVM). The SVM is used to generate gate pulses for an Inverter. Maximum Torque per Ampere (MTPA) is considered which ensures minimum ohmic losses. To reduce the reduces number of switching states and hence switching losses and to generate gate pulses to a five level inverter, three level inverter using SVM is taken as a reference. To verify the designed system, a simulator is implemented in MATLAB software environment and a comparison of results with and without MTPA control is being shown. Results clearly show that torque ripple, THD of motor phase voltage and current are greatly reduced under MTPA control.

Single-Stage PV-Grid Interactive Induction Motor Drive With Improved Flux Estimation Technique for Water Pumping With Reduced Sensors

This article deals with a photovoltaic-grid integrated system operating an induction motor (IM) coupled to a water pump. A simple dc-link voltage regulation approach is adopted for the power transfer. This system is utilized to primarily feed the induction motor-driven water pump and when water pumping is not desired, the power is delivered to the utility. This system requires two current sensors and two voltage sensors in total for sensing and estimation purpose. Induction motor phase currents are estimated from dc-link current by modified space vector modulation (SVM) technique. The speed estimation in this system is achieved by artificial neural network-based model reference adaptive system with a third-order integrator for flux estimation and is capable of controlling the power flow as per demand. The field-oriented control is used for speed control of an IM-pump. A third-order integrator based unit voltage generation algorithm is used to control the power transfer in both the direction between utility and the IM drive with water pump by regulating dc-link voltage. The appropriateness of the system is justified by simulated results on MATLAB/Simulink platform and test results procured with the help of a developed prototype during varying solar irradiances.

Open circuit fault detection and FTC for sensorless PMS motor control based on the back-EMF SMO

ABSTRACT The detection of the electrical fault in speed controller under a Motor Control Unit System (MCUS) has been amply viewed in the research paper. Nevertheless, the research work in this domain have been constantly followed on sensor-based vector control of synchronous motor. This paper combines the Power Inverter Voltage (PIV) faults detection (signal-based approach) with sliding mode technique (model-based) to provide Fault Tolerant Control (FTC) for sensorless speed Permanent Magnet Synchronous (PMS) motor drive. Back-EMF sliding mode observer (Back-EMF-SMO) is used for rotor position and stator currents estimation and simultaneously MCUS fault diagnosis. The fault diagnosis for MCUS faults of PMS motor drives using a Hilbert Transform. The motor phase currents signals shapes for various modes of MCUS faults are examined. A PIV Faults Detection and Isolation (FDI) algorithm is used to allow the switchover to a redundant leg. The obtained findings exhibit the effectiveness of the suggested FDI process particularly to detect and to isolate a PIV faults for sensorless PMS motor drives.

An Improved DC-Link Series IGBT Chopping Strategy for Brushless DC Motor Drive With Small DC-Link Capacitance

This article proposes an improved DC-link series IGBT chopping strategy for the brushless DC motor (BLDCM) drive equipped with a small DC-link capacitor fed by single-phase AC source. In this strategy, different vector sets are established according to the switching state of the DC-link IGBT and the operation mode of BLDCM. By analyzing the effect of each vector on phase current change rate, a vector selection-based current control scheme is presented. In particular, when the rectifier output voltage is less than the average line voltage of BLDCM, the combined action of vectors with only DC-link IGBT chopping is designed, in order to decrease the converter switching times and reduce the DC-link capacitance at the same time. In addition, the constraint of the DC-link capacitor voltage is analyzed to satisfy the reliable regulation of the motor phase currents, and the calculation method of the DC-link capacitance is given furthermore. The proposed strategy can achieve the smooth operation of the motor with small DC-link capacitance. Meanwhile, the total switching times of the converter are reduced, thereby improving the converter efficiency. The contrastive experimental results verify the correctness of the theories and the effectiveness of the proposed strategy.

Virtual Current Sensor in the Fault-Tolerant Field-Oriented Control Structure of an Induction Motor Drive.

Designing electrical drives resistant to the failures of chosen sensors has recently become increasingly popular due to the possibility of their use in fault-tolerant control (FTC) systems including drives for electric vehicles. In this article, a virtual current sensor (VCS) based on an algorithmic method for the reconstruction of the induction motor (IM) phase currents after current sensor faults was proposed. This stator current estimator is based only on the measurements of the DC-bus voltage in the intermediate circuit of the voltage-source inverter (VSI) and a rotor speed. This proposal is dedicated to fault-tolerant vector controlled IM drives, where it is necessary to switch to scalar control as a result of damage to the current sensors. The proposed VCS allows further uninterrupted operation of the direct rotor-field oriented control (DRFOC) of the induction motor drive. The stator current estimator has been presented in the form of equations, enabling its practical implementation in a microprocessor system. Simulation studies of the proposed algorithm in an open and closed-loop DRFOC structure are presented under different operation conditions of the drive system. The experimental verification of the proposed method is also presented and the accuracy of the stator current estimation algorithm is analyzed under various operating conditions of the drive system.

Fast and accurate open-circuit fault diagnosis method for PWM voltage source inverters in the three-phase PMSM control systems

Traditional fault diagnosis methods for converter open-circuit faults may present poor anti-interference performance, low detection speed and high misdiagnose rate especially during the motor acceleration. In order to solve the above problem, a new converter single open-circuit faults diagnosis method is proposed in this paper. Firstly, though conducting differential operation for the current variables, the common mode interference can be removed. Based on the differential information, differential currents states observer is designed, which improves the anti-jamming performance of the diagnosis method. Secondly, to avoid misdetection, a variable fault detection threshold is designed. This kind of faults diagnosis method does not need additional sensors or hardware change, and does not require the motor phase currents to be sinusoidal. Besides, the detection index rises rapidly once the fault occurs. Therefore, the application range, detection accuracy, and fault detection speed can be improved simultaneously. Finally, experimental results are presented to demonstrate the correctness of the analysis and the validity of the proposed methods.

Reduced Current Sensor Based Solar PV Fed Motion Sensorless Induction Motor Drive for Water Pumping

This paper proposes a solar photovoltaic (PV) array fed induction motor (IM) drive operated water pumping system with a speed adaptive estimator. It focuses on the implementation of a space vector modulation (SVM) of voltage source inverter (VSI) without current sensors. The motor phase currents are estimated from the dc-link current. The VSI is used for maximum power tracking and to drive an IM. A generalized integrator based flux adaptation approach is used to improve the drive performance. Moreover, a modified model reference adaptive system based speed estimation with rotor fluxes and stationary frame currents enhances its stability throughout the operating range. A modified algorithm based on incremental-conductance is proposed for maximum power point, which is used for peak power tracking at each insolation with a technique to control flow rate. The overall system incorporating a single-stage PV powered SVM based VSI fed IM driven water pump is modeled and its performance is simulated in MATLAB/Simulink environment. The appropriateness of proposed system is verified experimentally on a prototype developed in the laboratory under various operating conditions.

Reduced-Sensor-Based PV Array-Fed Direct Torque Control Induction Motor Drive for Water Pumping

This paper aims at the design, control, and implementation of a solar photovoltaic (PV) array-fed speed sensorless direct torque control of an induction motor drive (IMD) for water pumping in a standalone as well as battery-connected hybrid mode. This stator flux estimated by the proposed flux observer is used for speed estimation. A dc-link current sensor is used to reconstruct the motor phase currents by modified active voltage vector. One voltage sensor for dc-link voltage sensing and only one current sensor for dc-link current sensing are used in this system for standalone operation of the system. All other required quantities are estimated through these two sensed signals. The IMD is energized by a PV array, which is operated at maximum power point (MPP). A perturb and observe control algorithm with additional flow rate controller is proposed for MPP, which tracks MPP throughout the operating range and provides the facility to control the flow rate. The suitability of the system is judged through simulated results in MATLAB/Simulink as well as test results obtained on a prototype developed in the laboratory.

Derivation of Motor Mean Phase Currents in PMSM Drives Operating with Low Switching-to-Fundamental Frequency Ratio

Abstract Pulse width modulation (PWM) of inverter output voltage causes the waveforms of motor phase currents to consist of distinctive ripples. In order to provide suitable feedback for the motor current controllers, the mean value must be extracted from the currents’ waveforms in every PWM cycle. A common solution to derive the mean phase currents is to sample their value at the midpoint of a symmetrical PWM cycle. Using an assumption of linear current changes in steady PWM subintervals, this midpoint sample corresponds to the mean current in the PWM cycle. This way no hardware filtering or high-rate current sampling is required. Nevertheless, the assumption of linear current changes has been recently reported as over simplistic in permanent magnet synchronous motor (PMSM) drives operating with low switching-to-fundamental frequency ratio (SFFR). This, in turn, causes substantial errors in the representation of the mean phase currents by the midpoint sample. This paper proposes a solution for deriving mean phase currents in low SFFR PMSM drives, which does not rely on the linear current change assumption. The method is based on sampling the currents at the start point of a PWM cycle and correcting the sampled value using a model-based formula that reproduces the current waveforms. Effectiveness of the method is verified by simulation for an exemplary setup of high-speed PMSM drive. The results show that the proposed method decreases the error of determining the mean phase currents approximately 10 times when compared to the classical midpoint sampling technique.

A Sensorless Commutation Error Correction Method for High-Speed BLDC Motors Based on Phase Current Integration

Inaccurate commutation in brushless dc motor (BLDCM) will induce current harmonic and increase motor loss, which reduce motor efficiency. Meanwhile, for the sensorless BLDCM, the motor commutation is seriously affected by detection errors and calculation errors, which are caused by the nonideal conditions and the parameters variation. In this paper, a novel commutation error correction method is proposed to determine optimal commutation instant for the sensorless high-speed BLDCM. First, the relationship between commutation error and motor phase current is analyzed. According to this relationship, an initial commutation error can be calculated and compensated in one conduction interval. Then, online commutation corrections are performed to compensate for the residual error in following conduction intervals. The correction accuracy of commutation instant is determined by the phase current integral difference. This method is insensitive to motor parameters and back electromotive force waveform. Therefore, the commutation error is effectively eliminated in the whole speed range. Finally, the feasibility and effectiveness of the proposed method are evaluated by experimental results.