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This paper proposes a modification to existing saliency-based, sensorless control strategy for interior permanent magnet synchronous motors. The proposed approach leverages a two-interval, six-segment high-frequency voltage signal injection technique. It aims to improve rotor position and speed estimation accuracy when utilizing a single current sensor positioned in the inverter's DC-bus circuit. The key innovation lies in modifying both the high-frequency signal injection and demodulation processes to address challenges in accurate phase current reconstruction and rotor position estimation, at low and zero speeds. A significant modification to the traditional high-frequency voltage signal injection method is introduced, which involves splitting the signal injection and the field-oriented control algorithm into two distinct sampling and switching periods. This approach ensures that no portion of the injected voltage space vector falls into the immeasurable region of space vector modulation, which could otherwise compromise current measurements. The dual-period structure, termed the two-interval six-segment high-frequency injection, allows for more precise current measurement during the signal injection period while maintaining optimal motor control during the field-oriented control period. Furthermore, this paper explores a different demodulation technique that improves the estimation of rotor position and speed. By employing a synchronous filter in combination with a phase-locked loop, the proposed method enhances the robustness of the system against noise and inaccuracies typically encountered in phase current reconstruction. The effectiveness of the proposed modifications is demonstrated through comprehensive simulation results. These results confirm that the enhanced method offers more reliable rotor position and speed estimates compared to the existing sensorless technique, making it particularly suitable for applications requiring high precision in motor control. [ABSTRACT FROM AUTHOR]

Copyright of Electric Machines & Control / Dianji Yu Kongzhi Xuebao is the property of Electric Machines & Control and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes a current measurement error compensation method for single current sensor SPMSM drives under low-frequency modulation index operation. When using a single current sensor, two phase currents are sampled and the other phase current is calculated. Since the sampling instants of two-phase currents are separate, the sampled currents cannot represent the motor current at the same instants. Due to this current measurement error, the motor control performance can be degraded. This paper analyzes the impact of the current measurement error and proposes a current measurement error compensation method. Simulation and experimental results are presented to verify the proposed compensation method. [ABSTRACT FROM AUTHOR]

In this paper, we present a deep learning approach for identifying current intensity and frequency. The reconstruction is based on measurements of the magnetic field generated by the current flowing in a conductor. Magnetic field data are collected using a magnetic probe capable of generating a spectrogram, representing the spectrum of frequencies of the magnetic field over time. These spectrograms are saved as images characterized by color density proportional to the induction field value at a given frequency. The proposed deep learning approach utilizes a convolutional neural network (CNN) with the spectrogram image as input and the current or frequency value as output. One advantage of this approach is that current estimation is achieved contactless, using a simple magnetic field probe positioned close to the conductor. [ABSTRACT FROM AUTHOR]

To solve the problem of relay protection caused by CT saturation, a CT saturation identification method is proposed based on flux density characteristics and secondary current reconstruction technology in the distortion area. The CT saturation is identified based on the characteristics of the magnetic flux density trapezoidal region at saturation. Then the saturation region of CT is obtained using the slope of the flux variance to construct the saturation criterion based on the difference between entry saturation and exit saturation and calculate the time corresponding to the start and end point of secondary current saturation. The protection starting criterion is constructed based on the current at the maximum grid load to avoid protection misoperation. Finally, the least square method is used to reconstruct the secondary current in the saturation region to reflect the primary current reliably. The simulation results based on PSCAD/EMTDC software show that the proposed method is accurate and reliable, and can quickly and effectively identify the saturated CT segment with a time error of less than 1 ms.

Copyright of Electric Power is the property of Electric Power Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Electric Power is the property of Electric Power Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To solve the chattering problem caused by discontinuous switching function in traditional sliding mode observer, a piecewise square root switching function with continuously varying characteristics is designed, and its stability is analyzed by using Lyapunov stability criterion. Secondly, according to the relationship among bus current, switching state and phase current, a single bus resistance sampling current reconstruction scheme without current sensors is adopted, which effectively reduces the cost of motor system. Finally, the feasibility and effectiveness of the proposed scheme are verified by simulation.

In order to achieve high-precision stability evaluation and time-domain simulation of AC/DC distribution systems, and improve the analysis efficiency of complex systems, an average dynamic phasor modeling method of AC/DC distribution systems was proposed with considering the current reconstruction of dual-active bridge (DAB) high frequency transformer and the error correction of phase shifting duty cycle. Based on the average dynamic phasor model of voltage source converters (VSCs) and DABs established, the equivalent phase shift duty cycle of DAB was used as a modified algebraic variable to reduce the deviation caused by ignoring high-order dynamic phasors in modeling process and Fourier series are used to reconstruct the winding current of the high frequency transformer, respectively, to realize the accurate characterization of the DC and AC variables in average dynamic phasor models. Then an expandable global model of AC/DC distribution systems has been established by introducing the distribution line equations. Finally, according to the time-domain simulation based on MATLAB/Simulink software, the influence of model stability when the operating frequency and the leakage inductance of high frequency transformer changes was analyzed, and the correctness and accuracy of the proposed average dynamic phasor model was verified under the two scenarios of load mutation and disconnection fault.

The traditional single current sensor control strategy of a permanent magnet synchronous motor (PMSM) often adopts the DC bus method, which makes it difficult to eliminate the blind area of current reconstruction. Therefore, a current reconstruction method based on a sliding mode observer is proposed. Based on the current equation of the motor, the method takes the α-axis and β-axis currents as the observation objects and shares the same synovial surface, so that the α-axis current observation value and the β-axis current observation value converge to the actual current value at the same time and the unknown β-axis current information is obtained. The control system first tests the performance of the motor under different working conditions when the parameters are matched, and then tests the current reconstruction ability of the parameter mismatch. The results show that the current observer with a matched parameter can accurately and quickly reconstruct the β-axis current under various operating conditions, and the maximum current error does not exceed 4 mA. When the parameters are mismatched, high-performance control of the motor can still be achieved. The proposed method has excellent robustness. [ABSTRACT FROM AUTHOR]

The neutral point clamped (NPC) three-level grid-tied converter is the key equipment connecting renewable energy and power grids. The current sensor fault caused by harsh environment may lead to the split of renewable energy. The existing sensor fault-tolerant methods will reduce the modulation ratio index of the converter system. To ensure continuous operation of the converter system and improve the modulation index, a model predictive control method based on reconstructed current is proposed in this paper. According to the relationship between fault phase current and a voltage vector, the original voltage vector is combined and classified. To maintain the stable operation of the converter and improve the utilization rate of DC voltage, two kinds of fault phase current are reconstructed with DC current, normal phase current and predicted current, respectively. Based on reconstructed three-phase current, a current predictive control model is designed, and a model predictive control method is proposed. The proposed method selects the optimal voltage vector with the cost function and reduces time delay with the current reconstruction sector. The simulation and experimental results showthat the proposed strategy can keep the NPC converter running stably with one AC sensor, and the modulation index is increased from 57.7% to 100%.

To improve the performance of position sensorless control with a single current sensor in low-speed range, an improved current reconstruction method is proposed. High-frequency voltage is injected to estimate the rotor position. The time interval between two sampling moments is fixed as the minimum sampling window time. Therefore, the phase current can be compensated by an online adaptive one-step method. And the time-aligned three-phase currents can be reconstructed. The influence of the error between time-aligned reconstructed currents and the full sensors sampling currents on sensorless control is discussed. With the proposed method, the injection frequency can be improved to half the switching frequency. Finally, a permanent magnet synchronous motor is sensorless controlled with the proposed method in the experiments. [ABSTRACT FROM AUTHOR]

Neutral-point clamped (NPC) three-level grid-tied converter is the key power electronic equipment connecting renewable energy and power grid. High temperature and other factors can lead to current sensor failure, control strategy failure, output current distortion, and even lead to the disconnection of renewable energy. To maintain the normal operation of NPC three-level grid-tied converter with current sensor fault, a model predictive fault-tolerant control strategy based on space voltage vector set and fault phase current reconstruction is proposed. Firstly, the relationship between fault phase current and voltage vector is studied. After the current sensor fault, only 12 out of 27 voltage vectors were found to be able to reconstruct faulty phase currents with a DC current sensor and an AC current sensor. Model predictive current control using the set of these 12 voltage vectors, and fault phase current is directly calculated by DC current and normal phase current, which improves the fault tolerance and stability of the converter system. Finally, simulation and experimental results verified the effectiveness of the proposed method.

In single current sensor (SCS) methods, different phase currents should be acquired sequentially under the duration time of specific voltage vectors within each switching period. The sampling asynchronization caused due to sampling delay will inevitably result in the increase of phase current reconstruction error and deteriorate the control performance. According to the fundamental expression formula of three-phase currents in permanent magnet synchronous motor drives, the sampling-delay error (SDE) occurring in the traditional SCS techniques is analyzed in this article. It is demonstrated that the error oscillates at the stator electrical frequency, with the amplitude affected by both the switching frequency and motor speed. Correspondingly, a novel compensation method based on a δ–γ reference frame is presented. There is a simple proportional relationship between δ- and γ-axis error component after filtering the ac component by a notch filter. As a result, the SDE can be easily eliminated without extra complex compensation algorithms introduced. The prominent feature of the proposed method is that it is developed without necessity of motor parameters when compared with previous compensation techniques, making it a more robust solution. Several experimental results are provided to verify the effectiveness of the proposed method. [ABSTRACT FROM AUTHOR]

This paper deals with the three-phase current reconstruction method under the low modulation index operation of three-phase three-level PWM inverters by using the single-shunt current signal measurement. The shunt is placed in a DC-link. The proposed reconstruction method is based on the combination of collinear vector injection and shifting of Space Vector Modulation (SVM) signals. The method offers a good solution for the area where the small modulation index appears. In this case, a lack of measurement time exists due to the narrow triggering pulses. This approach was studied theoretically and verified by laboratory experiments. [ABSTRACT FROM AUTHOR]

This article presents field-oriented control of permanent magnet synchronous motor (PMSM) with single current sensor (DC-link). Field-oriented control requires current values flowing from three phases of the motor. These currents can be determined by current sensors to be connected to the phases as well as DC-link current sensor to be connected to supply side of invertor. Only one current value is determined by DC-link sensor. In this method, current reconstruction method is used to determine the current flowing from three phases. In this study, two different methods were compared. The mean value method and the least squares method were used to determine the current flowing through three phases using the current value measured from the DC-link current sensor. Performance evaluation of these two methods was made by comparing the integral squared error and total harmonic distortion values of the three phase currents obtained. [ABSTRACT FROM AUTHOR]

In this article, a dual-vector located model predictive control (DL-MPC) method based on a single dc-link current sensor is proposed for the permanent-magnet linear motor drive system. In DL-MPC, the phase currents are reconstructed by sampled dc-link current and selected active voltage vector (VV). Meanwhile, the sunk number of phase current is defined to evaluate the accuracy of current reconstruction. The first-optimal and second-optimal VVs are determined by dual-vector location. The second-optimal VV is selected for the voltage source inverter when the sunk number exceeds the threshold. Compared with traditional MPC schemes, DL-MPC has smaller current tracking error and better dynamic performance. Meanwhile, DL-MPC has more accurate current reconstruction and lower computation burden than that of the traditional MPC. The effectiveness of DL-MPC is verified by both theoretical analysis and experimental results. [ABSTRACT FROM AUTHOR]

Because of the time-sharing sampling logic, the three-phase currents reconstructed by single dc-link shunt present significant errors in the permanent magnet synchronous motor drives. A traceback-prediction current correction method for sampled currents is proposed in this article to eliminate the reconstruction errors. According to the analysis of time-sharing sampling errors, the concept of equivalent current change rate during one pulsewidth modulation (PWM) period is introduced, and the phase current characteristic model based on state observer is established. Both the equivalent and instantaneous current change rates can be obtained by the observer-based calculation method. In order to improve the current reconstruction precision, the ultimate values of three-phase currents can be predicted by adopting the proposed traceback-prediction current correction method, which does not require major computation and is easy to implement with no restrictions on the PWM strategy. The effectiveness of the proposed method is verified by experimental results. [ABSTRACT FROM AUTHOR]

This paper proposes a high frequency injection technique applied for low-speed sensorless control of interior permanent magnet synchronous machines (IPMSM) with a single dc-link current sensor. The three-phase currents, which can be reconstructed by the measurement of a dc-link current sensor, always suffer from the immeasurable regions. The most challenging problem exists in the low modulation region, where no phase current can be measured by the dc-link current sensor, and it is rarely solved without PWM modifications. This paper proposes a six-direction square wave high frequency injection method to extend the voltage vector to the measurable region to achieve the three-phase current reconstruction and saliency-based sensorless control without modifying the space vectors of the pulse width modulation (PWM). In addition, the paper comes up with a modified reconstruction scheme to reduce the reconstruction error and improve the accuracy of the position estimation. This low-speed sensorless strategy using a single dc-link current sensor is implemented in dSpace platform and the performance is evaluated by experiments.

In this article, three-phase motor currents pass through a three-core cable are measured using a two-winding Rogowski coil. The two-winding Rogowski coil is externally fitted around the three-core cable without the need for removing its insulation layers. This results in reducing the measurement complexity. Two windings are fitted around a circular non-magnetic core considering 120o between their center points. The EMFs induced in each winding due to magnetic flux linkage between windings and cable cores are used to reconstruct the three-phase motor currents through the cable cores. In order to reconstruct cable currents, a current reconstruction algorithm is developed. Sensor design and the developed current reconstruction algorithm are theoretically and experimentally validated. Theoretical validation is carried out through Power Simulation Program (PSIM). Regarding the theoretical validation, a three-phase motor fed from a three-phase source is simulated. Motor feeding is carried out using a cable having three cores. The proposed Rogowski coil is simulated and the currents through the cable are theoretically reconstructed considering different operating conditions. Also, experimental validation is carried out considering the measurements of three-phase currents through the cable feeding a 15 HP, three-phase induction motor from a three-phase source. A designed two- winding Rogowski coil is used for sensing the measured currents and a Digital Signal Processor (DSP) is used for implementing the adopted current reconstruction algorithm. Finally, efficacy of the proposed two-winding Rogowski sensor as well as the developed current reconstruction algorithm is proved through the obtained results. [ABSTRACT FROM AUTHOR]

In this article, a coupled fault-tolerant control (C-FTC) is proposed for primary permanent-magnet linear motor traction system in subway applications. By coupling the faulty mover with a healthy mover, the proposed C-FTC can achieve continuous operation of the faulty mover, in which one or more current sensors fail. A healthy mover is determined as the reference mover. The switch-states of the reference mover are also applied to its mathematical model. As a result, synchronous currents of the reference mover are also estimated from its mathematical model, and they are treated as the reference currents of the mathematical model of the faulty mover. Hence, the switch-states of the faulty mover can be determined. Therefore, the faulty mover can be controlled without any current sensors. The key of C-FTC is to compensate the parameter variations and the nonlinear effects of the faulty mover drive system with those of a healthy mover drive system, which is the main contribution of this article. Comparing with the conventional current-sensorless control, C-FTC has stronger robustness to the parameter variations and the nonlinear effects. The effectiveness and robustness of the proposed C-FTC are verified by simulation and experimental results. [ABSTRACT FROM AUTHOR]

In this article, a proposed non-invasive design of Rogowski coil to measure 3-phase currents through a 3-core cable is presented. Considering this design, there is no need to remove the insulation layers of a 3-core cable to measure its core currents. The adopted Rogowski coil design uses three separate coils wound at the same circular non-magnetic core with equal spacing between them. When the Rogowski coil is fitted around a 3-core cable, EMF is induced in each coil. The three induced EMFs are used to reconstruct the current passes through each cable core using a proposed current reconstruction technique. In order to validate the presented Rogowski coil design as well as the current reconstruction technique, theoretical verification is carried out using Power Simulation Program (PSIM) software. Hence, a 3-phase source feeds a 3-phase load is simulated. Also, simulation of the designed Rogowski coil as well as the adopted current reconstruction technique is carried out. The obtained theoretical results prove the accurate measurements of the Rogowski coil design and the introduced current reconstruction technique. For more validation, the Rogowski coil design is experimentally implemented. The implemented Rogowski coil is fitted around a 3-core cable that feeds a 3-phase load from a 3-phase source. The current reconstruction technique is implemented using a digital signal processing (DSP) board. The obtained experimental results give another evidence for the validity and efficacy of the proposed Rogowski coil design as well as the current reconstruction technique. [ABSTRACT FROM AUTHOR]

The ability to predict the electric and magnetic fields generated by a component can solve many in-system interference problems before they occur. In this article, methods are presented to predict the high-frequency near electric and magnetic fields from a component using a method of moment approach. The current representation is estimated from a near electric-field scan by solving the electric field integral equation. The reconstruction method was validated with measurements of a test board containing a buffer integrated circuit. The current representation was shown to accurately predict fields at locations both above and to the side of the buffer with less than a 3.5-dB average error. Here, a near-field scan was only performed on a flat plane above the emitter and was used to predict sources to the side of the emitter. To accurately predict fields to the side of the emitter, the current representation must be defined on a surface between the emitter and the prediction location. An error analysis was performed to understand the impact of scan plane parameters, such as the size of the scan plane, the size of the current representation, and the relative distance between the current representation and the estimated fields on prediction accuracy. [ABSTRACT FROM AUTHOR]

The conventional phase current reconstruction strategies utilize a dc bus current sensor to reproduce the three-phase currents during phase current sensor faults. However, no current sensor is guaranteed to be healthy in an actual drive. It means that the only survived current sensor may not be accidentally located at the dc bus side, and it can also be at the phase side. In addition, previous studies focus on a particular inverter topology for current reconstruction, whose fault-tolerant capability is threatened when the inverter topology is changed due to malfunctions. This article proposes a survivable interior permanent magnet synchronous motor (IPMSM) drive that realizes the current reconstruction purpose whichever the only survived current sensor is. Besides, inverter topology reconfiguration can be realized by not changing the wirings of the current sensors. Most important of all, the proposed strategy does not affect the normal operations of the drive when no fault occurs. The effectiveness of the proposed strategy is verified by experimental results on a 5-kW IPMSM motor prototype, which shows that the reconstructed phase currents track the actual ones accurately under different failure conditions. [ABSTRACT FROM AUTHOR]

• Propose an on-chip silicon-based integrated 3D Through-Silicon-Via Rogowski coil. • Integrate the current trace and 3D TSV Rogowski coil for in-situ current measurement. • Use ordinary differential equation method for current waveform reconstruction. • Silicon-based TSV Rogowski coil effectively enable on-chip in-situ current measurement. With the rapid advancement of microelectronics, 3D silicon-based integration microsystem technology has found widespread applications in various interconnected domains such as power generation, electric vehicles, smart grids, automation, and the Internet of Things (IoT). The high integration density within three-dimensional integrated microsystems has resulted in increasingly complex coupling between components, underscoring the critical importance of system health diagnostics. Presently, current waveform analysis, which yields valuable insights into the circuit system's condition, serves as a prevalent technique for system health assessment. However, traditional current sensors, typically packaged as discrete devices for current sensing, are inadequate for internal electrical signal detection within 3D IC microsystems. Therefore, this paper presents the design of a silicon-based integrated 3D Through-Silicon-Via (TSV) Rogowski coil tailored for in-situ electric current measurement. The structure and parasitic parameters of the 3D TSV Rogowski coil are meticulously determined through finite element method (FEM) simulations, facilitating the development of an appropriate signal processing circuit. Moreover, an Ordinary Differential Equation (ODE) current reconstruction method is proposed for measuring current. Leveraging this structural and circuit design, on-chip silicon-based integrated 3D TSV Rogowski coils are fabricated, followed by rigorous experimental validation. The experimental results convincingly attest to the effective in-situ current measurement capability of the on-chip silicon-based integrated 3D TSV Rogowski coil for 3D IC microsystems. [ABSTRACT FROM AUTHOR]

In recent years, electric propulsion systems have become widely, used and these systems have strict limits in volume and weight. Therefore, it is necessary to reduce the weight of the inverter-motor drive system. In a typical n inverter-motor drive system, at least 2n phase current sensors are required. In order to reduce the number of phase current sensors, this paper proposes a method for measuring phase current using n DC link current sensors in a 2n inverter-motor drive system. Two phase currents per inverter-motor system are measured during one period of the switching frequency using the pulse width modulation (PWM) shift method. However, since the measured phase current contains an error component in the average current, the error component was compensated for in order to obtain a current similar to the actual phase current by using the slope and dwell time of the phase current. The effectiveness of the proposed method is verified through experiments.

Because both magnets and windings can be mounted in the mover, the primary permanent-magnet linear motor (PPMLM) has a low-cost advantage for subway applications. In this paper, a novel direct thrust force control (DTFC) with single dc-link current sensor is proposed for PPMLM traction system in subway applications. The first phase current is directly measured by the dc-link current sensor. The second phase current is sensed with a limited delay, which is strictly limited by the limited measurement delay principle. The third phase current is calculated based on the condition that the summation of the three phase currents is zero. During the current reconstruction, no motor parameters are required. Because PPMLM may sink in the same phase for a long time and affect the current reconstruction accuracy, the single optimal target is proposed to re-select the original voltage vector. Compared with the conventional DTFC scheme, the proposed one has nearly the same performances; especially, the maximum speed and response time remain nearly unchanged. The effectiveness of the proposed DTFC scheme is verified by experimental results. [ABSTRACT FROM AUTHOR]

Noncontact monitoring technique of mechanical and electrical states is increasingly attractive for the overhead transmission system. This paper proposes a new technique to detect the tower inclination and transmission line sag, and measure transmission current simultaneously. The key of this technique is to use the ground magnetoresistive (MR) sensor to measure the magnetic flux density along the center line from the three-phase transmission lines. Moreover, the magnetic field (MF) calculation formulas for a tilted tower are given in this paper. Finally, with MF calculation formulas, an algorithm based on artificial immune system (AIS) is applied to estimate the transmission line sag and tower tilt angles, and reconstruct currents. Model simulations of an overhead transmission system are carried out to verify the idea. The simulation results validate the feasibility of this noncontact approach to estimate mechanical parameters and reconstruct electrical parameters for overhead transmission system. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Due to the large-scale renewable energy connected to the power grid by power electronic converters, the inertia and stability of the power grid is declining. In order to improve the inertia and support the grid recovery, the three-phase converter works as a virtual synchronous generator (VSG) to respond to the frequency and voltage changes of the power grid. This paper proposes a model predictive control for the virtual synchronous generator (MPC-VSG) strategy, which can automatically control the converter output power with the grid frequency and voltage changes. Further consideration of fault-tolerant ability and reliability, the method based on improved voltage vector selection, and reconstructed current is used for MPC-VSG to ensure continuous operation for three-phase converters that have current-sensor faults, and improve the reconstruction precision. The proposed method can respond to the frequency and voltage changes of the power grid and has fault-tolerant ability, which is easy to realize without pulse width modulation (PWM) and a proportional-integral (PI) controller. The effectiveness of the proposed control strategy is verified by experiment.

An electromagnetic flaw model and imaging techniques are developed simulating the magnetic nondestructive evaluation of proton exchange membrane fuel cells. A small flaw model is introduced to simulate the perturbation in magnetic field due to pinholes in the membrane. An inversion scheme is demonstrated to reconstruct the ionic current distribution in the membrane. Methods of stray field removal are then discussed. The research objectives of the above techniques are to locate flaws and enable the determination of current density in the fuel cell membrane in the presence of stray fields produced by electrodes, current leads, and background noise sources. [ABSTRACT FROM AUTHOR]

To reduce the cost of the inverter system in home appliances, a method using a shunt resistor at the DC-link can be substituted for a method using two current sensors at the inverter output. However, the minimum time of the active vector is required to sample the accurate current using a 1-shunt resistor. Therefore, many studies have been conducted investigating current reconstruction methods in the unmeasurable region of the current. The conventional methods using voltage injection have some problems such as high THD (Total Harmonic Distortion) and acoustic noise, because the PWM pattern is shifted. In addition, the current reconstruction is inaccurate in a low modulation region. In this paper, the cause of the noise in conventional methods is analyzed and a simple current reconstruction method based on an average current estimation and a current reference is utilized for reducing acoustic noise. In an immeasurable area, especially a low modulation region, an intermittent PWM shift method is proposed to enhance the accuracy of the reconstructed current. Therefore, a control strategy that combines all of the mentioned methods is implemented for the entire operating range. The effectiveness of the proposed methods is verified through the experimental results and the results of sound measurement in an anechoic chamber are included to compare with the acoustic noise.

The current monitoring of bundle conductors is essential for precisely locating operation failures in transmission lines, leading to a more stable and reliable power grid. This paper proposed a novel method for current reconstruction of bundle conductors, utilizing tunneling magnetoresistive (TMR) sensors. Both the normal and abnormal situations are discussed. The optimal and sub-optimal measurement points for sensors were obtained for concise current measurement with only one uniaxial TMR sensor. The current in each bundle conductor was calculated separately based on the comprehensive algorithm. Validation experiment indicated the error of the measurement and calculation system was no more than 10%, proving the robustness and feasibility of the measurement system and the algorithm. The reconstruction process takes full advantages of TMR sensors and provides a promising solution for transmission line monitoring in power grid. [ABSTRACT FROM AUTHOR]

As inverter powered variable speed drives become popular and technically mature, cost control becomes the core competence for inverter manufacturers. Under minimum performance requirement specifications, the inverter is tailored in every aspect, from the main power device to various sensors to enhance its competitiveness. This paper mainly focuses on various issues associated with the downgrade of current sensors from standard Hall sensor to shunt resistors. The limitation of current sensing by shunt resistors is reviewed and method to expand the maximum achievable modulation index on the vector plane is implemented. Experiments are conducted to verify the analysis and to validate the effectiveness of the reconstruction algorithm. [ABSTRACT FROM AUTHOR]

A current reconstruction method, for determining currents in a set of parallel infinitely long conductors located above the ground from measured magnetic field, is developed. The method is designed to work even if three-dimensional external disturbance fields from external sources are present. The external field is written as an expansion in spherical harmonics. Therefore, the field in the different measurement points is regarded as a linear combination of the expansion coefficients and the currents to be determined. A linear equation system is formed with the currents and the expansion coefficients as the unknowns. The currents are reconstructed by solving the equation system using least squares method and Tikhonov regularization. If the characteristics of the ground below the conductors are known with sufficient precision, the ground effect can also be included into the model. Results of various simulations show that the method works well and noise in the measured magnetic field can be handled. [ABSTRACT FROM AUTHOR]

In this paper, a single current sensor technique (SCST) is proposed for single-phase full-bridge inverters. The proposed SCST measures the currents of multiple branches at the same time, and reconstructs the average inductor, capacitor, and load current in a single switching cycle. Since all of the branches' current in the LC filter and the load are obtained using the SCST, both the inductor and the capacitor current feedback schemes can be selectively applied while taking advantages of each other. This paper also analyzes both of the current feedback schemes from the view point of the closed-loop output impedance. The proposed SCST and the analysis in this paper are verified through experiments on a 3kVA single-phase uninterruptible power supply (UPS). [ABSTRACT FROM AUTHOR]

Aiming at the control strategy of AC servo drive for high-speed ammunition feeding equipment, field oriented control(FOC) and direct torque control(DTC), permanent magnet synchronous motor(PMSM) mathematical model, vector control theory and "phase current reconstruction" technology were researched. A new strategy named "Fixed time effective vector insertion" was proposed after analyzing some existent methods that make the current reconstruction realized in whole regions. Simulation experiments were carried out in Matlab/Simulink and hardware platform was built for experiments. The results indicate that " Fixed time eefective vector insertion" can avoid the asymmetry of PWM output, this strategy can realize the current reconstruction in whole regions, the current waveform distortion rate is only 5.35%. The correctnees and the feasibility of the control strategies are verified, And some good foundation is laid for further experiment with AC servo drive for high-speed ammunition feeding equipment. [ABSTRACT FROM AUTHOR]

The magnetic inverse source problem of reconstructing the positions and currents of very long parallel conductors is considered in a two-dimensional situation, with applications to power line measurements. The input data is the magnetic field on a contour surrounding the conductors to be reconstructed. Using a scalar-vector Green identity, an explicit reconstruction algorithm is derived. The numerical implementation of the algorithm is described and simulation results are presented, demonstrating the influences from numerical errors and noise in measurement data. The algorithm can handle an arbitrary number of conductors, but benchmarking against the Cramér-Rao lower bounds indicate that the algorithm is non-optimal and becomes increasingly unstable when increasing the number of conductors. Mathematically, the Green identity approach removes the influence of external disturbances and thus has potential usefulness in current reconstruction for determining optimal sensor positions and how to process measurement data. [ABSTRACT FROM AUTHOR]

This paper presents a six-phase current reconstruction scheme for dual traction inverters in hybrid electric vehicles (HEVs) with a single dc-link current sensor. During the phase current reconstruction, one of the inverters is proposed to operate using active vectors, whereas the other inverter operates using nonactive vectors. An advanced phase-shift scheme for all pulsewidth-modulated (PWM) signals based on the sequence of duty cycles is implemented. PWM signals are considered in three types: large, medium, and small duty cycles. Then, the minimum phase-shift scheme is applied to each type of PWM signal to ensure the minimum duration of the active vector for stable current reconstruction. With this proposed phase-shift scheme, the maximum allowable modulation index and dc-link voltage utilization are improved. In addition, the relationship between the minimum required time for stable phase current reconstruction and the maximum allowable modulation index is derived theoretically. The effectiveness of the proposed method is verified by both simulation and experimental results. With this scheme, cost and volume of dual inverters in HEVs are reduced, considering the lower number of current sensors. [ABSTRACT FROM PUBLISHER]

Insertion of dead time, transfer links between micro control unit (MCU) and voltage source inverter (VSI), VSI's nonideal characteristics all lead to deviation that cannot be ignored between the actual output voltage and the command voltage, which seriously affects the performance of the ac induction motor (ACIM) control system. Among many dead-time effect compensation methods, VSI usually operates under an open-loop condition, thus making complete compensation hard to achieve. This paper studies methods to obtain the two key elements of compensation voltage amplitude and current polarity and a novel phase voltage compensation method is proposed. In this method, a simple hardware circuit is applied to obtain the actual output of the VSI as feedback with which precise compensation amplitude can be calculated. And judgment of current polarity is accurately realized by reconstructing phase current from filtered current components under M-T coordinate with a Kalman filter. The compensation in a zero-crossing region is also closely discussed in this paper. To verify the validity of the method, simulations and experiments are carried out. The experiments emphasize on the efficacy of feedback, steady-state, and transient performance of current reconstruction; and the performance of a conventional method to that of the proposed method are also compared. Results show that the proposed method proves to be effective. [ABSTRACT FROM AUTHOR]

A potential application of inverse source solver for high resolution near field scanning of microelectronic packages is studied in this paper. A fast inverse source solver based on the fast Fourier transform algorithm and conjugate gradient algorithm is developed with a half-space Green’s function. This solver can be used in microelectronic applications to solve radiation related problems, including electromagnetic interference and signal integrity of printed circuit boards or integrated circuit packagings. Simulation results show a significant improvement in image resolution and adjacent sources detectability when the inverse source solver is applied. Because of the improvements, the inverse source solver reduces the sensitivity on scan height in the near field scan process when the same source image resolution is desired. Experiments on measured data also validate the effectiveness of this solver. [ABSTRACT FROM AUTHOR]

Three-phase current reconstruction technique using dc current information in conventional two-level inverters can be used for the purpose of cost reduction and sensor fault tolerance. A novel phase current reconstruction scheme, with reduced immeasurable area and common mode voltage, is proposed in this paper. A tristate pulse-width modulation technique has been employed, in which three adjacent switching states are used to construct the reference voltage. The active switching states are arranged at the edge and the center of a PWM cycle. Fixed sampling and simultaneous three-phase currents can be easily achieved with very little hardware and software requirements. A detailed analysis of the effects of nonidealities leads to regional modifications of the switching sequence resulting in almost the whole hexagon as the feasible area. The usefulness of the proposed reconstruction algorithm has been verified by experimental results obtained from a 4-kW induction motor drive system. Smooth transitions between the redundant and fault-tolerant modes were observed. [ABSTRACT FROM AUTHOR]