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The objective of this paper is to propose a new control strategy for synchronous reluctance machines (SyRM) to mitigate the parameter saturation problems. The paper also highlights the reasons for the difference in the saturation behavior between the permanent magnet motors (PM) and the SyRM using the FEA flux distribution results. The synchronous reluctance machine is devoid of rotor magnets (in contrast with the PM machines) and it solely relies on reluctance portion to produce torque. This gives the SyRM machines the advantage of lower cost and more reliability compared to PM machines. But the lack of magnets in SyRM causes the motor parameters to saturate more quickly compared to the PM machines. The optimal control of the SyRM machine is thus strongly dependent on the controller’s ability to adapt to the fast changing saturation in the SyRM machine. The control strategy proposed in the paper uses a reference current generation block that optimizes the reference current for the saturation that would occur in the machine at any point in operation. A d-q voltage and current sign estimator reduces the controller iterations considerably to reach to a solution. The simulation and experimental results are presented for a 30 slot 4-pole SyRM machine.

The calculation of torque ripple in electric machines has been widely studied in the literature utilizing equivalent circuit approach and finite element approach. The objective of this paper is to have a deterministic set of mathematical equations consisting of basic properties such as space harmonics in the conductor distribution, space harmonics in the magnet flux distribution and time harmonics in the current to understand the creation of dc torque and torque ripple in permanent magnet machines. The physical quantities used in this study are the rotor magnetic flux density and the conductor distribution. These physical quantities are responsible for creating space harmonics. The time varying component is the inverter current harmonics. The torque is generated due to the interaction of the current density and the magnetic flux density in the air gap. The torque calculation method discussed in the paper highlights the contribution of each physical quantity in the final output torque of the machine. The set of equations presented in this paper shows the set of space and time based harmonic order components responsible for the creation of dc torque and torque ripple. This would enable in making broad system level design decisions for electric drive applications.

This article proposes an enhanced single-phase self-tuning pre-filter for estimating the fundamental grid voltage frequency. The known extended self-tuning filter (STF) adheres to an increased structural complexity, which may consume memory in the digital hardware to estimate the fundamental grid voltage signal. The proposed STF, which relies on a simple non-adaptive comb filter, may address this issue. Consequently, the introduction of imaginary zeros ensures better rejection of the DC-offset and the harmonic components while keeping the proposed filter structure simpler to implement. Furthermore, a simple open-loop frequency estimator is proposed, which does not involve any inverse trigonometric function to estimate the fundamental frequency. This entire proposal is cost-effective and has good frequency tracking abilities with a reduced computational load. The experimental results imply the suitability of the proposed scheme for weak inertia power grid networks where synthetic inertia controllers require a rapid frequency information to control the injected power under adverse grid voltage conditions.

Recently the world is suffering from a pandemic. Nations were extensively affected by the Covid-19. Individuals are fighting the battle to survive; people lost their lives or the ones that matter to them while some lost their livelihood. In an hour of need everyone is trying their best to win this battle, (WHO) World Health Organization advised, to maintain at least one-meter distance, to get a vaccination, and to wear face masks. Face masks can be efficacious as a barrier between humans and the virus. The Face Mask Detection performs a critical task in suppressing the transmission of covid-19. Here, the Face masks detector was constructed with a hybrid technique. The real-time face masks detector was distributed into two segments: Training Phase and Testing Phase. The paper represents the union of the transfer learning concept, MobileNetV2 model by google, and the Caffe model, with the help of some open-source libraries used for computer vision and machine learning. The datasets were provided by the Kaggle, and they were parted into two categories: training and testing sets. The model's accuracy was compared for the two datasets. The dataset with a greater number of images has better accuracy, and to avoid overfitting data augmentation was used.

Phase-locked loops (PLLs) are often deployed in a specialized control unit of grid-connected converters (GCCs) for their control and protection purposes. Moreover, presence of DC-offset, fundamental negative sequence (FNS) component, and harmonics in the grid signal may hinder the dynamic performance of the PLLs. In this paper, a robust three-phase synchronous reference frame (SRF)–PLL algorithm has been presented. The proposed algorithm will be helpful for rapid tracking of fundamental grid voltage attributes with those including amplitude, phase, and frequency. This is achieved by employing a delayed signal cancellation (DSC) operator cascaded to a modified moving average filter based orthogonal signal generator (MAF–OSG) in the pre-filtering stage. This combination of filters improves the transient response time and demonstrate the potential performance of the scheme if fundamental positive sequence (FPS) component alone is present in the input signal. Also, an instantaneous symmetrical component method is applied to obtain FPS component which facilitates ease tuning of loop parameters. The proposed scheme is tested for nominal and off-nominal frequency conditions in MATLAB/Simulink environment.

Most of the industries today employ the PI based control algorithms for their drive systems. These methods although successful in majority cases tend to suffer with limitations under certain operational conditions of the machine. The parameter uncertainties of the machine due to part to part variation can also limit the performance of the PI controller. The PI control is capable of correcting various uncertainties to maintain the reference current until its output is saturated. After saturation, the PI is not able to maintain current and the effect of this on the torque production needs to be clearly understood for the optimal control of the drive system. The effect of integral windup limit in such cases also needs to be understood. This paper discusses the effect of each parameter variation with respect to the PI output and the torque production. The discussion includes the PI behavior for the entire operating conditions that can expose the limitation of the PI control. The effective PI controllable region of the torque speed curve of the machine can be much lower than the nominal torque speed curve for which the machine was designed.

This paper proposes a bidirectional three phase single stage ac-dc converter for applications like Electric Vehicle (EV) chargers. AC side of the proposed converter consists of current fed half bridge converter for each of the three phases and the DC side has three phase full bridge converter. The primary and secondary side of the converter are connected through star connection of high frequency transformer. The proposed converter achieves zero current switching (ZCS) of primary side switches and zero voltage switching (ZVS) for secondary side devices, while feeding power from grid to the dc side. The converter has soft switching on the primary side switches when transferring power from the dc side to the grid. The paper also presents a novel modulation and control scheme for the bidirectional power flow. The converter is evaluated using PSIM simulation tool for its operation in all the four quadrants of the PQ plot. The design of the converter, control strategy and the results are presented for a 10KVA converter for EV charger. Qatar National Research Fund (a member of Qatar Foundation) - NPRP grant #NPRP 8-627-2-260.

This paper introduces an information construction methodology to handle eventualities of customer review. The prime attention is on the behavior patterns of the reviewers, building the core for the representation of these eventualities as sequences of emotional and mental actions. Developed foundation facilitates a domain-liberated comparison of the eventualities to manage/analyze behavior patterns of the reviewer. The established model for a special case of interaction (customer reviews) is built and the developed methodology is able to substantiate the sentiment, emotion and reason behind the mental action of the reviewer. The result of this study is that one can assess reviews irrespective of the domain, reasoning about rating of a review and reasoning about the likes/dislikes/emotion associated with the review is also possible. Analysis of emotions of reviewers is done, where the mental conduct is defined in terms of their beliefs and intentions.

Synchronous reference frame phase-locked loop (SRF-PLL) is widely adopted for estimating the grid voltage parameters. A good dynamic performance of SRF-PLL can be achieved under ideal grid conditions. However, its performance devolves in the presence of harmonics and fundamental negative-sequence (FNS) component. To address this issue, two module (TM) fixed frequency multiple complex coefficient filter (FF-MCCF) which acts as a prefilter. The frequency adaptive MCCF structure increases the overall dynamic response of the PLL. Further, under off-nominal frequency condition, TM-FFMCCF output introduces error in the estimated phase and amplitude. However, estimated frequency will not suffer any error in estimation. The error compensation in the estimated phase and amplitude is done by developing an error correction criteria. The implementation of proposed scheme is through with MAT-LAB/Simulink environment. Various test cases are considered and results are presented.

This paper discusses the effect of the position measurement delay on the performance a Permanent Magnet Synchronous Motor (PMSM) drive. The delays occurring in the measurement of the signals required for the control are usually neglected. This paper, explicitly focuses on the effect of position error due to delays in the measurement. The accurate prediction and compensation of position measurement delay is required to achieve the optimum performance of electrical machines. The performance is evaluated in terms of the average torque output under a given current command condition. A mathematical model of the average torque output with the various position delay usually present in practical system, is presented. Experimental results are provided showing the effect of such position delay and the improvement obtained after compensating for such delays. The knowledge of the measurement delay could be used to optimize the control implementation methods. The ignorance of such small delays could cause significant negative impact in high speed electric drives.

Detailed analysis of dual wound interior permanent magnet machine under winding fault scenarios has been presented in this research. Instead of using two separate machines, the dual wound machines offer better packaging within one mechanical construction. Under normal operating conditions, each 3-phase machine could carry either half or full load depending on the drive configuration. The research mainly focuses on the performance of the overall motor during various winding faults in one half of the machine. It compares the torque capability and ripple performance for double wound single and double repetition winding. The research shows the overall torque performance could vary significantly depending on the spatial coil locations for each 3-phase machine. Two different topologies for double wound single repetition machine have been presented. The research compares the available torque under winding fault condition to attain safe mode. A finite element based electromagnetic simulation is used for the analysis. The dual wound motors were built and tested that show well correlation with the simulation and verifies the research findings.

The small signal analysis of bidirectional single-phase single-stage AC-DC converter and its application for EV charging are presented in this paper. A unique control strategy for establishing soft switching without any additional circuit is developed utilizing the traditional state-space averaging technique. The small signal model in each mode of operation is presented. Using this model, current at the input of the ac side can be regulated to realize power factor correction (PFC) and also to regulate active and reactive power flow in either direction. Four quadrant operation of the converter can be utilized for improving the stability of the power grid. Controller designed using the derived small signal model is used to validate the operation as well as transition of the converter between V2G and G2V modes. Simulation results are presented to demonstrate four quadrant operation of the designed converter. Design of the converter, closed loop controller, and the results are presented for 1.5kVA converter.