Single Current Sensor Research Articles

Advanced induction motor drive control with single current sensor

This paper proposes induction motor drive control method which uses minimal number of sensors, providing only DC-link current as a feedback signal. Improved DC-link current sampling scheme and modified asymmetrical switching pattern cancels characteristic waveform errors which exist in all three reconstructed motor line-currents. Motor linecurrent harmonic content is reduced to an acceptable level, eliminating torque and speed oscillations which were inherent for conventional single sensor drives. Consequently, use of single current sensor and line-current reconstruction technique is no longer acceptable only for low and medium performance drives, but also for drives where priority is obtaining a highly accurate, stable and fast response. Proposed control algorithm is validated using induction motor drive hardware prototype based on TMS320F2812 digital signal processor.

Fault diagnosis scheme for open‐circuit faults in switched reluctance motor drives using fast Fourier transform algorithm with bus current detection

Reliability of power converters is of crucial importance in switched reluctance motor drives used for safety-critical applications. Open-circuit faults in power converters will cause the motor to run in unbalanced states, and if left untreated, they will lead to damage to the motor and power modules, and even cause a catastrophic failure of the whole drive system. This study is focused on using a single current sensor to detect open-circuit faults accurately. An asymmetrical half-bridge converter is considered in this study and the faults of single-phase open and two-phase open are analysed. Three different bus positions are defined. On the basis of a fast Fourier transform algorithm with Blackman window interpolation, the bus current spectrums before and after open-circuit faults are analysed in details. Their fault characteristics are extracted accurately by the normalisations of the phase fundamental frequency component and double phase fundamental frequency component, and the fault characteristics of the three bus detection schemes are also compared. The open-circuit faults can be located by finding the relationship between the bus current and rotor position. The effectiveness of the proposed diagnosis method is validated by the simulation results and experimental tests.

Neural speed estimator for line-connected induction motor embedded in a digital processor

Estimating the electrical and mechanical parameters involved in three-phase induction motors is frequently employed to avoid measuring every variable in the process. Among mechanical parameters, speed is an important variable: it is involved in control, diagnosis, condition monitoring, and can be measured or estimated by sensorless methods. These technologies offer advantages when compared with direct measurement, such as lower cost or more robust systems. This paper proposes the use of artificial neural networks to estimate rotor speed by using current sensors for balanced and unbalanced voltage sources with a wide mechanical load range in a line-connected induction motor. This paper also presents two case analyses: (i) a single current sensor; and (ii) a multiple currents sensors. Simulation and experimental results are presented to validate the proposed approach. A neural speed estimator embedded in a digital processor is also presented.

Saliency-Based Position Estimation of Permanent-Magnet Synchronous Machines Using Square-Wave Voltage Injection With a Single Current Sensor

This paper presents a saliency-based position sensorless drive of permanent-magnet (PM) machines using a single current sensor for cost-effective applications. For the single current sensor system, the dc-link current is measured for the reconstruction of three-phase currents. The phase current reconstruction can only be realized when active voltages are applied. This limitation results in six immeasurable areas for the current reconstruction using the pulsewidth modulation. In order to implement the saliency-based sensorless drive, a square-wave voltage is injected to minimize the harmonics of reconstructed saliency current for the rotor position estimation. By injecting a square-wave voltage on the direction of the rotor $d$ -axis, the injection voltage vector is nearly perpendicular to the fundamental voltage vector at low speed. The saliency reflected current or the fundamental current can be separately reconstructed by the dc-link current, leading to the reduced reconstruction errors and improved sensorless performance. By using the proposed signal injection technique on a single sensor system, the saliency-based sensorless drive can work on an interior PM machine with a salient ratio of $L_{q}/L_{d} = 1.35$ at 1% rated speed (60/6000 r/min) under full torque load based on the experimental evaluation.

A Battery Charging System for Intermittent Generation from a Synchronous Generator with a Novel Maximum Power Point Tracking Control

This paper proposed a battery charging system for intermittent generation from a synchronous generator with a novel Maximum Power Point Tracking (MPPT) control method. Analyzing the generation with boost chopper by the state space averaging method, the internal voltage of the generator, the output voltage and the resistance of the output of the boost chopper can be estimated by with only single current sensor. Even though the intermittent generation, the proposed the battery charging system is able to charge the battery constantly because of a bi-directional DC/DC converter and an Electric Double-Layer Capacitor (EDLC). The basic principle of the proposed MPPT control method and the proposed charging system are discussed, and then confirmed by digital computer simulation using PLECS. The simulation results reveal that the proposed MPPT controller controls the maximum power point and the proposed charging system is able to charge the battery constantly.

A Six-Phase Current Reconstruction Scheme for Dual Traction Inverters in Hybrid Electric Vehicles With a Single DC-Link Current Sensor

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.

A Three-Phase Current Reconstruction Technique Using Single DC Current Sensor Based on TSPWM

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.

Auto‐calibration of Hall effect sensors for home energy consumption monitoring

A technique to improve the accuracy of an electrical energy consumption monitoring system is proposed. This system is based on a network of Hall effect wireless sensors attached to the wire at the output of every circuit breaker in the electrical distribution panel. The readings provided by the Hall effect sensors show significant gain errors due to their sensitivity to the distance between the sensor and the monitored wire. To mitigate these gain errors and increase the system accuracy, the addition of a single high-precision current transformer sensor at the main electrical input is proposed, measuring the total current. This signal is used as the reference signal in a least-mean square algorithm to compensate for the unknown gains of the Hall effect sensors. Experimental results using three prototype Hall effect sensors show that the proposed solution converges within 1.7 min, reducing the average current measurement error from 2.54 to 0.46 Arms.

Direct Torque Control Using Phase Current Reconstruction Algorithm In Induction Motor

In this paper, a low-cost high-performance Induction Motor (IM) drive using Direct Torque Control (DTC) is obtained by simple algorithm using reconstruction of phase current. By using the details acquired from one shunt resistor this algorithm is developed. The proposed algorithm is very simple and robust. Stator currents were used to estimate motor flux and torque in previous works. In this algorithm the stator currents are replaced by dc current. A theoretical concept is developed for DTC based induction motor drive. The performance is simulated using MATLAB/SIMULINK software. Index Terms: Direct Torque Control (DTC), Induction Motor (IM), sensor count reduction, single current sensor.

Phase Current Reconstruction Using a Single Current Sensor of Three-Phase AC Motors Fed by SVM-Controlled Direct Matrix Converters

This paper presents a novel method for phase ac motor current reconstructing with a single current sensor in three-phase direct matrix converter (DMC) drive system using space vector modulation control technique. The main goal is to reduce the cost and to improve the reliability of drive systems that involve closed-loop control strategy. For this purpose, new structure and algorithm are developed which divide the zero-vector application time in two intervals and measure the phase currents using a new placement of the single Hall current sensor in DMC. These proposals constitute a good solution in the low-power-range DMC (below 15 kW), where reducing size and cost is the key objective. The simulation of the three-phase to three-phase DMC feeding an induction motor was done to demonstrate the advantages of the proposed system. Experiments were carried out owing to a DS1104 control board to check the validity of the proposed method.

Novel Single Current Sensor Topology for Venturini Controlled Direct Matrix Converters

This paper presents a new Venturini-based direct matrix converter (DMC) output phase current reconstruction method using a single current sensor. This method is proposed in order to reduce the cost and to improve the reliability of the drive with any control strategy. The proposed technique measures the phase currents using a new single Hall current sensor location in the DMC. To demonstrate the advantages of the proposed system, an experimental bench with a DMC, an induction motor, and a DSP board is carried out to confirm the validity and feasibility of the proposed current reconstruction approach.

Development of High-Reliability EV and HEV IM Propulsion Drive With Ultra-Low Latency HIL Environment

This paper proposes an improved and robust method of minimizing the error in propulsion-drive line-currents that are reconstructed from a single dc-link current measurement. The proposed algorithm extends and then shortens the relevant phase pulse-widths in order to provide optimal sampling of the dc-link currents in two consecutive pulsewidth modulation (PWM) periods. The proposed PWM pattern control enables an improved sampling method which cancels offset jitter-like waveform errors present in all three reconstructed line-currents, which is due to a specific combination of nonsimultaneously sampled dc-link current and line-current PWM ripple. The improvement in induction motor drive accuracy using a single current-sensor and no shaft sensor (as proposed in this paper), over that of conventional methods, is shown. Thanks to an ultra-low latency hardware-in-the loop (HIL) emulator, the proposed algorithm, its implementation on a DSP processor, code optimization and “laboratory” testing were all merged into one development step. In order to perform final tests of the proposed current-reconstruction algorithm and to verify the usefulness of the developed HIL platform by means of comparison, experimental results obtained on a real hardware setup are provided.

A Novel MPPT Control Method of Thermoelectric Power Generation with Single Sensor

This paper proposes a novel Maximum Power Point Tracking (MPPT) control method of thermoelectric power generation for the constant load. This paper reveals the characteristics and the internal resistance of thermoelectric power module (TM). Analyzing the thermoelectric power generation system with boost chopper by state space averaging method, the output voltage and current of TM are estimated by with only single current sensor. The proposed method can seek without calculating the output power of TM in this proposed method. The basic principle of the proposed MPPT control method is discussed, and then confirmed by digital computer simulation using PSIM. Simulation results demonstrate that the output voltage can track the maximum power point voltage by the proposed MPPT control method. The generated power of the TM is 0.36 W when the temperature difference is 35 °C. This is well accorded with the V-P characteristics.

The Unbalance Current Effect Caused by Non-Uniform Inductors in the Multi Phase Converter with a Single Current Sensor

To get less ripple of output voltage and reduce the inductor current capacity, the multi-channel scheme is a popular structure in the high power converter. By sharing the total current to multi channels, the channel current will be inversely proportional to the number of channels. Normally, the inductor of each channel is proposed to be uniform when the design procedure, and the inductor current of each channels also be supposed to be equal. And, the single current sensor structure will be considered, due to the cost reduction and the designed simplification. However, in real implementation, the inductance of each channels are different, and such kind of difference will cause some unexpected effect when using a single current sensor. To make sure the activity of the circuit as expectation, some non-uniform inductor effects in multi channel converter will be discussed in this paper. First, the measure method of the inductance error ratios in each channel will be proposed in the single current sensor scheme. Then, the unbalance current effect of the non-uniform inductance in the single sensor scheme will be discussed. The simulation results will be provided in this paper, which results will show the inductance measurement workable and the unexpected current obviously.

Fault Diagnosis Digital Method for Power Transistors in Power Converters of Switched Reluctance Motors

This paper describes four main fault types of the asymmetric bridge power converter in switched reluctance motor drive on power transistors. Two on-line fault diagnosis methods for power transistors in the power converter are proposed. The principle of the proposed diagnosis methods is to detect the real-time current state from some particular positions, and then obtain the diagnosis result and the fault location by logical judgment. One fault diagnosis method is proposed using single current sensor monitoring the chopped bus current; the other method is using dual current sensors scheme monitoring the upper freewheeling bus current and excitation bus current. The simulation results of current states from certain positions of a three-phase 12/8 motor and its power converter are analyzed. Experiments have verified the effectiveness of the proposed fault diagnosis methods. It is shown that the dual current sensors scheme monitoring the upper freewheeling bus current and excitation bus current has the fastest fault response.

Performance Analysis and the Cost Effective Position Sensorless Control of Axial Flux PM Brushless DC Motor

The aims of this paper are the simple comparison of the axial flux (AF) structures versus the radial flux (RF) structures for brushless permanent-magnet (PM) synchronous motors and proposing a cost effective position sensorless control strategy for AFPM Brushless DC Motor. The comparison is developed for different motor dimensions. Moreover, a cost effective and position sensorless control strategy proposed for AFPM brushless DC (BLDC) motor drive using single current sensor. It is based on the generation of quasi-square current waveforms, using only one current controller for the three phases. Unlike the conventional methods, the proposed method presents advantages such as very simple control scheme, without needing to triangular carrier modulation, and balanced phase currents. The proposed position sensorless technique is based on the detection of zero crossing points of three voltage functions that are derived from the difference between the lines’ voltage measured at the terminals of the motor. This control algorithm is particularly suitable for cost sensitive product such as air purifiers, air blowers, cooling fan, and related home applications. The effectiveness of the proposed control system have been validated by simulation results.

Optimal frequency tracking method for phase‐shift PWM inverter

AbstractThis paper proposes a new resonant frequency tracking control method for full‐bridge‐type high‐frequency inverters. Whereas the ordinary phase‐locked loop (PLL) based frequency control method uses a current sensor and a voltage sensor, the proposed technique can achieve the same purpose with a single current sensor. In high‐frequency power supply systems using a PLL, it is impossible to perform power control with an inverter. Therefore, an active converter must be used for power control, and the system grows larger. On the other hand, high‐frequency inverters using the proposed control system simultaneously enable power control and achieve the same resonant frequency tracking as a PLL, and thus high‐frequency power supply systems become extremely simple. This paper explains in detail the principle underlying the control method, and presents an example of a circuit to realize it. The theory is backed up by using a prototype high‐frequency power supply system which actually employs the proposed control system, thereby demonstrating its practical utility in industry. © 2012 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Simplified analytical inductance model for a single turn eddy current sensor

Analytical solutions for the inductance can be easily obtained for coils with rectangular cross sections having multiple turns realizing a homogeneous current distribution. These models have at least six parameters and do not consider the self-capacitance of the coil. The inner magnetic field is partially included, so that the accuracy of the static impedance is limited especially at higher frequencies. Even at lower frequencies, reference measurements without target are generally needed for self-calibration.By direct evaluation of the magnetic vector potential at the contour of the coil wire, a coil inductance model with a simpler mathematical structure can be obtained, which allows a consideration of the self-capacitance and the inner inductance. This avoids the need for reference measurements and the influence of distance, conductivity and permeability can be easier quantified. Inductance calculation requires 250ms on a standard personal computer for 100 frequencies resulting in a deviation of at most 5% for the static inductance. This is a good result with respect to the low impedances in the μΩ range, which are generally hard to measure. The proposed model represents a good basis for models of multiple turns with a precisely defined geometry including the self-capacitance effects.

Fast Switching Direct Torque Control Using a Single DC-link Current Sensor

This paper presents a fast switching direct torque control (FS-DTC) using only a single DC-link current sensor. In FS-DTC, six new active voltage complex space vectors (CSVs) are synthesized by the conventional active voltage space vectors (SVs). The corresponding sectors are rotated in the anticlockwise direction by 30 degrees. A selection table is defined to select the CSVs. Based on the "Different Phase Mode", the output sequence of the selected CSV is optimized. Accordingly, a reconstruction method is proposed to acquire the phase currents. The core of the FS-DTC is that all of the three phase currents can be reliably reconstructed during every two sampling periods, which is the result of the fast switching between different phases. The errors between the reconstructed and actual currents are strictly limited in one sampling period. The FS-DTC has the advantages of the standard DTC scheme such as simple structure, quick torque response and robustness. As can be seen in the analysis, the FS-DTC can be thought of as an equivalent standard DTC scheme with 86.6% of the maximum speed, 173.2% of the torque ripple, and 115% of the response time of the torque. Based on a dSPACE DS1103 controller, the FS-DTC is implemented in an induction machine drive system. The results verify the effectiveness of the FS-DTC.

Single-Turn Fault Detection in Induction Machine Using Complex-Wavelet-Based Method

Interturn short circuit is often confused with voltage imbalance in induction machines. Therefore, detection and classification of single-turn fault (TF) are becoming important in the presence of voltage imbalances, under various loading conditions. Substantial studies are conducted on the interturn fault detection, but a comprehensive method for classifying the faults at different operating points of the machine, under varying supply conditions, is still a challenge. This is a critical problem in industries since the induction motors form the major workhorses. The artificial-intelligence-based techniques are advanced methods in fault monitoring. This, when combined with optimization techniques, is expected to give improved and accurate results with minimum false alarms. In this paper, a technique is developed, based on recent developments in the wavelet-based analysis, particularly in the complex wavelet domain. The support vector machines are adopted for comparing the classification accuracy obtained using complex-wavelet- and standard discrete-wavelet-based methods. The receiver operating characteristic curves indicate that the fault detection, down to single turn, is feasible using a single current sensor.