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Volumen 5 (2020): Edición 1 (January 2020)

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Detalles de la revista
Formato
Revista
eISSN
2543-4292
Publicado por primera vez
16 Apr 2016
Periodo de publicación
1 tiempo por año
Idiomas
Inglés

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Volumen 5 (2020): Edición 1 (January 2020)

Detalles de la revista
Formato
Revista
eISSN
2543-4292
Publicado por primera vez
16 Apr 2016
Periodo de publicación
1 tiempo por año
Idiomas
Inglés

Buscar

17 Artículos
Acceso abierto

A Review of Methods and Challenges for Improvement in Efficiency and Distance for Wireless Power Transfer Applications

Publicado en línea: 10 Oct 2020
Páginas: 1 - 25

Resumen

Abstract

Over the past few years, interest and research in wireless power transfer (WPT) have been rapidly incrementing, and as an effect, this is a remarkable technology in many electronic devices, electric vehicles and medical devices. However, most of the applications have been limited to very close distances because of efficiency concerns. Even though the inductive power transfer technique is becoming relatively mature, it has not shown near-field results more than a few metres away transmission. This review is focused on two fundamental aspects: the power efficiency and the transmission distance in WPT systems. Introducing the principles and the boundaries, scientific articles will be reviewed and discussed in terms of their methods and respective challenges. This paper also shows more important results in efficiency and distance obtained, clearly explaining the theory behind and obstacles to overcome. Furthermore, an overlook in other aspects and the latest research studies for this technology will be given. Moreover, new issues have been raised including safety and security.

Palabras clave

  • wireless power transfer
  • inductive power transfer technique
  • efficiency
  • distance
  • safety
  • security
Acceso abierto

Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 1: Large Normalised Voltage Command

Publicado en línea: 10 Oct 2020
Páginas: 27 - 40

Resumen

Abstract

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for large normalised voltage command values [1/3, 1). The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

Palabras clave

  • 4-level DC–DC converter
  • flying capacitor
  • natural balancing
  • transients
Acceso abierto

Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 2: Small Normalised Voltage Command

Publicado en línea: 10 Oct 2020
Páginas: 41 - 57

Resumen

Abstract

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

Palabras clave

  • 4-level DC–DC converter
  • flying capacitor
  • natural balancing
  • transients
Acceso abierto

Drive unit characteristics of a completely electrical passenger aircraft

Publicado en línea: 10 Oct 2020
Páginas: 59 - 71

Resumen

Abstract

Aviation has, over the years, become an inseparable element of human life. Airplanes are very commonly used for various tasks, such as transport of passengers and goods, military attack and defence, rescue, recreation and so on. In spite of the many advantages of aviation, one cannot ignore its disadvantages. The most important disadvantages of aviation are the emissions that cause atmospheric pollution and noise. Additionally, one should remember about the decreasing stocks of non-renewable fuels. These drawbacks affect human health and the natural environment. Therefore, a good alternative to conventional drive units in aircraft may turn out to be electric drive units in the near future. The aim of this article is to check the extent to which today’s knowledge and technology allow the use of electric drive units instead of conventional aircraft drive units. This article presents the concept of electric aircraft, from the electric drive unit to its power supply system. The feasibility of designing an electric jet drive unit for a passenger aircraft was analysed based on the performances of PZL 104 Wilga 35 and Boeing B787 Dreamliner.

Palabras clave

  • aircraft
  • electric drive unit
  • fuel cells
  • all-electric aircraft
  • green aviation
Acceso abierto

Development of energy-efficient IBC with IGBT module for photovoltaic applications

Publicado en línea: 10 Oct 2020
Páginas: 73 - 81

Resumen

Abstract

The proposed study is improvised value-engineered modifications for the basic interleaved boost converter (IBC) by including relevant modifications in circuits, which is expected for a better performance in switching with reduction in losses. The newly modified IBC circuit with insulated gate bipolar transistor (IGBT) along with converter has been experimented by simulations and the results are tabulated to modified IBC with metal oxide silicon field effect transistors. Further experimental analysis and validations of the proposed simulation with hardware developed adopting model SKM195GB066D consisting of IGBTs is presented. This study further enhances and summarises the optimum utilisation and the performance of IBC with the proposed IGBT modules that synchronises power diode. Enhancing the simulation outcomes, the hardware is proposed and developed to be tested for a load up to 1.5 kW with the evaluation of key parameters such as efficiency of the converter.

Palabras clave

  • interleaved boost converter
  • efficiency
  • stability
  • power converters
  • switching frequency
Acceso abierto

Various Rotor Topologies of Line-Start Synchronous Motor for Efficiency Improvement

Publicado en línea: 10 Oct 2020
Páginas: 83 - 95

Resumen

Abstract

Line-start synchronous permanent magnet motor (LSSPMM) is being considered as a replacement or alternative to asynchronous squirrel-cage motor (AM) in constant speed applications. This is due to the better efficiency and power factor than the asynchronous motor. There are various rotor topologies of LSSPMM concerning the magnets placement and their dimensions. The paper analyses six different rotor topologies in terms of achieving the best efficiency and power factor for the same output power of the motor with minimal consumption of permanent magnet material. All other motor design parameters remain unchanged, i.e. all motor topologies are analysed for the same stator laminations and the same motor windings. The numerical finite element method (FEM) models and dynamic models for obtaining transient characteristics of speed, torque and current verify the proposed design of various motor models. The results from all motor models are compared and adequate conclusions are derived regarding the optimal rotor topology in terms of obtaining the best efficiency and power factor with minimal consumption of permanent magnet material, for the same output power of the motor.

Palabras clave

  • line-start synchronous permanent magnet motor
  • rotor topologies
  • transient characteristics
  • FEM
Acceso abierto

Capacitor Energy Variations in MMC Using Harmonics Injection

Publicado en línea: 10 Oct 2020
Páginas: 97 - 107

Resumen

Abstract

Modular multilevel converter (MMC) is considered as a good technology for high-voltage direct current (HVDC) transmission systems. It can generate a good quality staircase output voltage waveform due to the cascaded connection of large number of identical sub-modules (SMs). Energy variations in SM capacitor lead to capacitor voltage fluctuations which affect the size and stability of MMC. Traditionally MMC arm voltages are controlled using direct modulation method. The closed loop and open loop compensated modulation methods are implemented to overcome the drawbacks created in direct modulation method. However, these methods rely on the accurate measurements or estimation of SM capacitor voltages. In this paper, capacitor energy variations in MMC based on direct modulation method under three different categories using proportional-resonant (PR) controllers are discussed as (a) pure sinusoidal arm current (b) sinusoidal arm current with addition of large 2nd harmonic (c) sinusoidal arm current with addition of 2nd +4th harmonics. Analytical and simulation results show reduction in capacitor energy variations in MMC while injecting harmonics in the arm currents using direct modulation method.

Palabras clave

  • MMC
  • HVDC
  • power converter
  • capacitor energy
Acceso abierto

Fractional Order Sliding Mode Speed Control of Feedback Linearized Induction Motor

Publicado en línea: 31 Oct 2020
Páginas: 109 - 122

Resumen

Abstract

Induction machines have of late become the most popular workhorses in the industry replacing DC machines because of their advantages, such as reduced cost, reliability and the absence of commutators, which make them adapt to unfavourable conditions with lower maintenance requirement. However, higher-order models of AC machines, nonlinearities in model equations, uncertainties in parameters and load disturbances make induction motors difficult to control than that of DC motors. In this paper, a robust control strategy considering the recent advances in technology is proposed employing input-output feedback linearization for the exact decoupling of electromagnetic torque and rotor flux using fractional-order sliding mode controller (SMC) for the outer speed loop. The sliding mode observer is also designed to extract the rotor flux from the DC input voltage of the inverter and stator current measurements. Finally, a comparison between the commonly used proportional integral and derivative (PID) controller and the proposed fractional-order SMCs is made and the conclusion is reached.

Palabras clave

  • induction motor
  • input-output feedback
  • linearization
  • fractional-order sliding mode controller
  • SVPWM
  • load torque observer
Acceso abierto

Diagnosis of Short-circuits in Induction Motor Stator Winding Using a Modified Park Transformation

Publicado en línea: 06 Nov 2020
Páginas: 123 - 133

Resumen

Abstract

This paper deals with a novel diagnostic method for finding the stator winding short-circuit damage of induction motor drives. The proposed method is based on a new, simple idea of applying a modified, triple Park transform instead of using a computationally demanding on-line Fast Fourier Transform (FFT) analysis. The diagnostic method is based on the analysis of current and reference voltage vector components, which are the part of the Direct Field Oriented Control structure. The proposed method is verified experimentally using tests results. Further, the influence of speed, load torque and the parameters of PI regulators on the performance of the proposed diagnostic method are also discussed.

Palabras clave

  • induction motor
  • damage diagnostics
  • shorted turns
  • Park’s transformation
Acceso abierto

All-Bootstrap Gate-Driver Supply System for a High-Voltage-Gain Resonant DC-DC Converter with Seven Switches

Publicado en línea: 06 Nov 2020
Páginas: 135 - 142

Resumen

Abstract

This paper presents the concept and implementation of an electronic system for a switched-capacitor DC-DC converter with high voltage gain. The converter consists of seven switches, five of which being controlled like high-side type. This paper presents a non-typical bootstrap-based gate-driver system so that the converter can run using a single voltage source. The converter requires a special switching pattern to drive seven switches in a steady state and also during the start-up of the converter and the regulation of the output voltage. Therefore, an FPGA-based digital control system is used with various switching algorithms and protection functions implemented. The presented converter is an autonomic device that taps the energy from the main input. Therefore, the electronic system of the converter is equipped with a self-supply system with a wide range of the input voltage. The parameters of the converter such as voltage gain, voltages and power ranges can be scalable for prospective applications with the proposed control system.

Palabras clave

  • FPGA
  • DC-DC converter
  • digital control
  • gate-driver circuit
Acceso abierto

Rotor Resistance Estimator based on Virtual Current Sensor Algorithm for Induction Motor Drives

Publicado en línea: 06 Dec 2020
Páginas: 143 - 156

Resumen

Abstract

In this article, model reference adaptive system (MRAS)-based estimator of a rotor resistance of an induction motor (IM) is presented. In contrast to the solutions known from the literature, the reference model of this estimator uses the measured values of the phase current and the adaptive part is a virtual current sensor. The article presents an accurate description of the algorithm taking into account the discrete equations for possible practical implementation in the microprocessor system. In the first step, the impact of motor parameters to stator current estimation quality in the adaptive model was checked. Subsequently, simulation tests of the proposed rotor resistance estimator were carried out for the field-oriented control of the induction motor drive system with a model of an induction motor with fixed parameters and an induction motor with a changing main inductance according to a magnetisation curve. The analysis of the estimator’s work showed its high efficiency and insensitivity to changes in the IM main inductance.

Palabras clave

  • induction motor drive
  • rotor resistance estimator
  • model reference adaptive system
  • virtual current sensor
  • fault tolerant control
Acceso abierto

Power Quality Enhancement Using DSTATCOM in Industry Plants

Publicado en línea: 21 Dec 2020
Páginas: 157 - 175

Resumen

Abstract

This paper is focused on increasing the power quality of Unique Macaroni factory, located in Bahir Dar Town. Necessary data have been collected from the factory and the collected data are analysed. Based on the analysis of data, it is found that the factory working power factor is low and hovering around 0.7125. Voltage variations are up to 9.09%, average voltage unbalance is 2.2% and total harmonic distortion (THD) of load currents and voltage are 24.17% and 10.16%, respectively. Harmonic components have existed in the power distribution system of the factory. Based on the analysis of power quality problem in the factory, distribution static compensator (DSTATCOM) and its control system have been designed to boost power quality of the factory and the results are obtained by generating simulations using Matlab software. It is observed from outputs of the Matlab simulations that DSTATCOM can improve the power quality of the factory. Generally, the shape of the waveform of load voltage and current is improved and THD level of load voltage is minimised to 1.55% and load current THD level is 7.09%. The reactive power needed by the loads (442 kVAr) is almost provided by the DSTATCOM, so reactive power from source supply is very small such as 22 kVAr so that the power factor of the source tends to unity.

Palabras clave

  • power quality
  • power quality problems
  • DSTATCOM
  • Matlab/Simulink
Acceso abierto

Bidirectional DC–AC Converter-Based Communication Solution for Microgrid

Publicado en línea: 21 Dec 2020
Páginas: 177 - 188

Resumen

Abstract

The communication system of a microgrid can transfer the information of electricity price, power consumption and so on between users and the control centre. This capability is of great significance to improve the efficiency and sustainability of power facilities. In this paper, a bidirectional DC–AC converter topology is proposed to achieve the composite transmission of power and signals in microgrids. Since the transmitted signals are modulated by power switches of converters and integrated into the currents, the cost of signal couplers can be saved and the circuit structure can be simplified. In order to verify the feasibility of the proposed method, a simulation model of the proposed converter is implemented in MATLAB/Simulink. With the power supply frequency of 50 Hz, when the converter operates in the inverter mode and rectifier mode, the data transmission rate can reach 120 bit/s and 48 bit/s, respectively.

Palabras clave

  • bidirectional DC–AC converter
  • frequency shift keying
  • MATLAB simulation
  • microgrid
  • two-way communication
Acceso abierto

Simple Technique of Initial Speed Identification for Speed-Sensorless Predictive Controlled Induction Motor Drive

Publicado en línea: 31 Dec 2020
Páginas: 189 - 198

Resumen

Abstract

This article presents a simple technique of identifying the initial speed that allows for restarting a sensorless induction motor (IM) drive controlled by a model predictive flux control (MPFC). Initial speed identification is required because, according to the research, the applied current-model reference adaptive system (C-MRAS) can restart the IM after failure only if the error of the initial speed set in the estimator is <25%. The proposed technique is based on short periods of flux generation for the certain initial speed and observation of the estimated torque respond. The direction of the estimated torque determines whether the real speed is higher or lower than the initial one set in the estimator. In two steps, the algorithm identifies the initial speed with an accuracy of 25%. This allows for a quick restart of the IM from any speed, eliminating the disadvantage of the sensorless drive control system with the C-MRAS speed estimator. The experimental results measured on a 50 kW drive which illustrates the operation and performances of the system are presented.

Palabras clave

  • induction motor
  • sensorless control
  • model predictive control
  • MRAS estimators
  • initial speed identification
  • restarting IM
Acceso abierto

Sensorless Induction Motor Drive Based on Model Reference Adaptive System Scheme Utilising a Fictitious Resistance

Publicado en línea: 31 Dec 2020
Páginas: 199 - 213

Resumen

Abstract

This article presents a new development of an indirect stator flux-oriented controller for sensorless speed induction motor drive utilising instantaneous and steady-state values, respectively, of a fictitious resistance symbolised as R_f. The dimension of the fictitious quantity, in this context, is the ohm, which is the difference between the stator d- and q-axis fictitious resistances. However, from the measurement of the stator voltage and currents of the machine, two independent resistance estimators are built. Therefore, the first is considered as a reference model of the induction machine (IM), and the second is considered as an adjustable model. Subsequently, the error between the states of the two models is used to drive a suitable adaptation mechanism that generates the estimation of the speed, for the adjustable model. Furthermore, the structure of the proposed estimator is free from stator resistance and eliminates the requirement of any flux computation. All the detailed simulation study is carried out in MATLAB/Simulink to validate the proposed method and to highlight the robustness and the stability of the proposed model reference adaptive system estimator.

Palabras clave

  • indirect stator flux-oriented controller (ISFOC) model
  • model reference adaptive system (MRAS)
  • fictitious resistance
  • rotor speed estimation
  • induction motor (IM)
Acceso abierto

Design and Simulation of Direct and Indirect Back EMF Sliding Mode Observer for Sensorless Control of PMSM

Publicado en línea: 28 Dec 2020
Páginas: 215 - 228

Resumen

Abstract

This article compares two sensorless control algorithms for a permanent magnet synchronous machine (PMSM) based on the back-EMF sliding mode observer (SMO). Indirect SMO (I-SMO) treats the back-EMF voltages as a disturbance. Direct SMO (D-SMO) considers back-EMF voltages as state-space variables. The same phase-locked loop (PLL) is used for both observers for extraction of the rotor position and speed values from the observed back-EMF voltages. In a sensorless control, the observed speed is used as feedback for the PI controller, and the observed position is used in the Park transformations. Both observers have been implemented and tested with standard field-oriented control. Simulation results indicate rather comparable speed and position estimation precision for both, but the D-SMO indicates slightly higher precision in steady-state. Even more, a tuning procedure of the D-SMO is more straightforward when compared to the I-SMO. Thus, the D-SMO was further verified experimentally with the OP 5600 rapid prototyping device and with a 350 W PMSM drive. Experimental results of the D-SMO are included at the end of the paper.

Palabras clave

  • back-EMF sliding mode observer
  • sensorless control
  • PMSM
  • phase-locked loop
Acceso abierto

Design and Simulation of Cyclic Battery Tester

Publicado en línea: 28 Dec 2020
Páginas: 229 - 241

Resumen

Abstract

The paper presents an approach to the modelling of a cyclic battery tester and contains observations about lithium-ion (Li-ion) batteries, charging/discharging procedures, conditions and protections which must be observed during the testing process. The main goal was to create and simulate a schematic which will be capable of cyclically testing Li-ion battery cells. Regulation of the final schematic is based on cascade connections of operation amplifiers, which work as a voltage source with current-limiting functions. The power part is created by two MOSFETs connected as a half-bridge. This topology allows current to flow in both directions (from and to the battery). Final simulation is supplemented by protections such as reverse polarity protection, short circuit protection and overvoltage protection during charging. Proper operation of the whole connection is demonstrated by the simulation outputs in the final section.

Palabras clave

  • battery
  • cell
  • charging
  • discharging
  • Simscape
17 Artículos
Acceso abierto

A Review of Methods and Challenges for Improvement in Efficiency and Distance for Wireless Power Transfer Applications

Publicado en línea: 10 Oct 2020
Páginas: 1 - 25

Resumen

Abstract

Over the past few years, interest and research in wireless power transfer (WPT) have been rapidly incrementing, and as an effect, this is a remarkable technology in many electronic devices, electric vehicles and medical devices. However, most of the applications have been limited to very close distances because of efficiency concerns. Even though the inductive power transfer technique is becoming relatively mature, it has not shown near-field results more than a few metres away transmission. This review is focused on two fundamental aspects: the power efficiency and the transmission distance in WPT systems. Introducing the principles and the boundaries, scientific articles will be reviewed and discussed in terms of their methods and respective challenges. This paper also shows more important results in efficiency and distance obtained, clearly explaining the theory behind and obstacles to overcome. Furthermore, an overlook in other aspects and the latest research studies for this technology will be given. Moreover, new issues have been raised including safety and security.

Palabras clave

  • wireless power transfer
  • inductive power transfer technique
  • efficiency
  • distance
  • safety
  • security
Acceso abierto

Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 1: Large Normalised Voltage Command

Publicado en línea: 10 Oct 2020
Páginas: 27 - 40

Resumen

Abstract

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for large normalised voltage command values [1/3, 1). The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

Palabras clave

  • 4-level DC–DC converter
  • flying capacitor
  • natural balancing
  • transients
Acceso abierto

Analysis of Transients in a 4-Level Flying Capacitor Converter: Time Domain Approach. Part 2: Small Normalised Voltage Command

Publicado en línea: 10 Oct 2020
Páginas: 41 - 57

Resumen

Abstract

A 4-level flying capacitor converter (FCC) operation is considered on a base of discrete state-space model. A transition matrix is obtained for a pulse width modulation (PWM) period for small normalised voltage command values [0, 1/3]. The transition matrix elements are expanded into power series by small parameters. The matrix eigenvalues are presented in the form of power series as well. Six separate transients are constructed for six possible initial FCC states on a PWM period. Inductor current and capacitors’ voltage transients are found for the voltage source power-up as the arithmetic average of the six separate transients. Finally, the discrete solutions are replaced by equivalent continuous ones. Simple and accurate formulas for inductor current and capacitors’ voltage transients demonstrate good agreement with simulation results.

Palabras clave

  • 4-level DC–DC converter
  • flying capacitor
  • natural balancing
  • transients
Acceso abierto

Drive unit characteristics of a completely electrical passenger aircraft

Publicado en línea: 10 Oct 2020
Páginas: 59 - 71

Resumen

Abstract

Aviation has, over the years, become an inseparable element of human life. Airplanes are very commonly used for various tasks, such as transport of passengers and goods, military attack and defence, rescue, recreation and so on. In spite of the many advantages of aviation, one cannot ignore its disadvantages. The most important disadvantages of aviation are the emissions that cause atmospheric pollution and noise. Additionally, one should remember about the decreasing stocks of non-renewable fuels. These drawbacks affect human health and the natural environment. Therefore, a good alternative to conventional drive units in aircraft may turn out to be electric drive units in the near future. The aim of this article is to check the extent to which today’s knowledge and technology allow the use of electric drive units instead of conventional aircraft drive units. This article presents the concept of electric aircraft, from the electric drive unit to its power supply system. The feasibility of designing an electric jet drive unit for a passenger aircraft was analysed based on the performances of PZL 104 Wilga 35 and Boeing B787 Dreamliner.

Palabras clave

  • aircraft
  • electric drive unit
  • fuel cells
  • all-electric aircraft
  • green aviation
Acceso abierto

Development of energy-efficient IBC with IGBT module for photovoltaic applications

Publicado en línea: 10 Oct 2020
Páginas: 73 - 81

Resumen

Abstract

The proposed study is improvised value-engineered modifications for the basic interleaved boost converter (IBC) by including relevant modifications in circuits, which is expected for a better performance in switching with reduction in losses. The newly modified IBC circuit with insulated gate bipolar transistor (IGBT) along with converter has been experimented by simulations and the results are tabulated to modified IBC with metal oxide silicon field effect transistors. Further experimental analysis and validations of the proposed simulation with hardware developed adopting model SKM195GB066D consisting of IGBTs is presented. This study further enhances and summarises the optimum utilisation and the performance of IBC with the proposed IGBT modules that synchronises power diode. Enhancing the simulation outcomes, the hardware is proposed and developed to be tested for a load up to 1.5 kW with the evaluation of key parameters such as efficiency of the converter.

Palabras clave

  • interleaved boost converter
  • efficiency
  • stability
  • power converters
  • switching frequency
Acceso abierto

Various Rotor Topologies of Line-Start Synchronous Motor for Efficiency Improvement

Publicado en línea: 10 Oct 2020
Páginas: 83 - 95

Resumen

Abstract

Line-start synchronous permanent magnet motor (LSSPMM) is being considered as a replacement or alternative to asynchronous squirrel-cage motor (AM) in constant speed applications. This is due to the better efficiency and power factor than the asynchronous motor. There are various rotor topologies of LSSPMM concerning the magnets placement and their dimensions. The paper analyses six different rotor topologies in terms of achieving the best efficiency and power factor for the same output power of the motor with minimal consumption of permanent magnet material. All other motor design parameters remain unchanged, i.e. all motor topologies are analysed for the same stator laminations and the same motor windings. The numerical finite element method (FEM) models and dynamic models for obtaining transient characteristics of speed, torque and current verify the proposed design of various motor models. The results from all motor models are compared and adequate conclusions are derived regarding the optimal rotor topology in terms of obtaining the best efficiency and power factor with minimal consumption of permanent magnet material, for the same output power of the motor.

Palabras clave

  • line-start synchronous permanent magnet motor
  • rotor topologies
  • transient characteristics
  • FEM
Acceso abierto

Capacitor Energy Variations in MMC Using Harmonics Injection

Publicado en línea: 10 Oct 2020
Páginas: 97 - 107

Resumen

Abstract

Modular multilevel converter (MMC) is considered as a good technology for high-voltage direct current (HVDC) transmission systems. It can generate a good quality staircase output voltage waveform due to the cascaded connection of large number of identical sub-modules (SMs). Energy variations in SM capacitor lead to capacitor voltage fluctuations which affect the size and stability of MMC. Traditionally MMC arm voltages are controlled using direct modulation method. The closed loop and open loop compensated modulation methods are implemented to overcome the drawbacks created in direct modulation method. However, these methods rely on the accurate measurements or estimation of SM capacitor voltages. In this paper, capacitor energy variations in MMC based on direct modulation method under three different categories using proportional-resonant (PR) controllers are discussed as (a) pure sinusoidal arm current (b) sinusoidal arm current with addition of large 2nd harmonic (c) sinusoidal arm current with addition of 2nd +4th harmonics. Analytical and simulation results show reduction in capacitor energy variations in MMC while injecting harmonics in the arm currents using direct modulation method.

Palabras clave

  • MMC
  • HVDC
  • power converter
  • capacitor energy
Acceso abierto

Fractional Order Sliding Mode Speed Control of Feedback Linearized Induction Motor

Publicado en línea: 31 Oct 2020
Páginas: 109 - 122

Resumen

Abstract

Induction machines have of late become the most popular workhorses in the industry replacing DC machines because of their advantages, such as reduced cost, reliability and the absence of commutators, which make them adapt to unfavourable conditions with lower maintenance requirement. However, higher-order models of AC machines, nonlinearities in model equations, uncertainties in parameters and load disturbances make induction motors difficult to control than that of DC motors. In this paper, a robust control strategy considering the recent advances in technology is proposed employing input-output feedback linearization for the exact decoupling of electromagnetic torque and rotor flux using fractional-order sliding mode controller (SMC) for the outer speed loop. The sliding mode observer is also designed to extract the rotor flux from the DC input voltage of the inverter and stator current measurements. Finally, a comparison between the commonly used proportional integral and derivative (PID) controller and the proposed fractional-order SMCs is made and the conclusion is reached.

Palabras clave

  • induction motor
  • input-output feedback
  • linearization
  • fractional-order sliding mode controller
  • SVPWM
  • load torque observer
Acceso abierto

Diagnosis of Short-circuits in Induction Motor Stator Winding Using a Modified Park Transformation

Publicado en línea: 06 Nov 2020
Páginas: 123 - 133

Resumen

Abstract

This paper deals with a novel diagnostic method for finding the stator winding short-circuit damage of induction motor drives. The proposed method is based on a new, simple idea of applying a modified, triple Park transform instead of using a computationally demanding on-line Fast Fourier Transform (FFT) analysis. The diagnostic method is based on the analysis of current and reference voltage vector components, which are the part of the Direct Field Oriented Control structure. The proposed method is verified experimentally using tests results. Further, the influence of speed, load torque and the parameters of PI regulators on the performance of the proposed diagnostic method are also discussed.

Palabras clave

  • induction motor
  • damage diagnostics
  • shorted turns
  • Park’s transformation
Acceso abierto

All-Bootstrap Gate-Driver Supply System for a High-Voltage-Gain Resonant DC-DC Converter with Seven Switches

Publicado en línea: 06 Nov 2020
Páginas: 135 - 142

Resumen

Abstract

This paper presents the concept and implementation of an electronic system for a switched-capacitor DC-DC converter with high voltage gain. The converter consists of seven switches, five of which being controlled like high-side type. This paper presents a non-typical bootstrap-based gate-driver system so that the converter can run using a single voltage source. The converter requires a special switching pattern to drive seven switches in a steady state and also during the start-up of the converter and the regulation of the output voltage. Therefore, an FPGA-based digital control system is used with various switching algorithms and protection functions implemented. The presented converter is an autonomic device that taps the energy from the main input. Therefore, the electronic system of the converter is equipped with a self-supply system with a wide range of the input voltage. The parameters of the converter such as voltage gain, voltages and power ranges can be scalable for prospective applications with the proposed control system.

Palabras clave

  • FPGA
  • DC-DC converter
  • digital control
  • gate-driver circuit
Acceso abierto

Rotor Resistance Estimator based on Virtual Current Sensor Algorithm for Induction Motor Drives

Publicado en línea: 06 Dec 2020
Páginas: 143 - 156

Resumen

Abstract

In this article, model reference adaptive system (MRAS)-based estimator of a rotor resistance of an induction motor (IM) is presented. In contrast to the solutions known from the literature, the reference model of this estimator uses the measured values of the phase current and the adaptive part is a virtual current sensor. The article presents an accurate description of the algorithm taking into account the discrete equations for possible practical implementation in the microprocessor system. In the first step, the impact of motor parameters to stator current estimation quality in the adaptive model was checked. Subsequently, simulation tests of the proposed rotor resistance estimator were carried out for the field-oriented control of the induction motor drive system with a model of an induction motor with fixed parameters and an induction motor with a changing main inductance according to a magnetisation curve. The analysis of the estimator’s work showed its high efficiency and insensitivity to changes in the IM main inductance.

Palabras clave

  • induction motor drive
  • rotor resistance estimator
  • model reference adaptive system
  • virtual current sensor
  • fault tolerant control
Acceso abierto

Power Quality Enhancement Using DSTATCOM in Industry Plants

Publicado en línea: 21 Dec 2020
Páginas: 157 - 175

Resumen

Abstract

This paper is focused on increasing the power quality of Unique Macaroni factory, located in Bahir Dar Town. Necessary data have been collected from the factory and the collected data are analysed. Based on the analysis of data, it is found that the factory working power factor is low and hovering around 0.7125. Voltage variations are up to 9.09%, average voltage unbalance is 2.2% and total harmonic distortion (THD) of load currents and voltage are 24.17% and 10.16%, respectively. Harmonic components have existed in the power distribution system of the factory. Based on the analysis of power quality problem in the factory, distribution static compensator (DSTATCOM) and its control system have been designed to boost power quality of the factory and the results are obtained by generating simulations using Matlab software. It is observed from outputs of the Matlab simulations that DSTATCOM can improve the power quality of the factory. Generally, the shape of the waveform of load voltage and current is improved and THD level of load voltage is minimised to 1.55% and load current THD level is 7.09%. The reactive power needed by the loads (442 kVAr) is almost provided by the DSTATCOM, so reactive power from source supply is very small such as 22 kVAr so that the power factor of the source tends to unity.

Palabras clave

  • power quality
  • power quality problems
  • DSTATCOM
  • Matlab/Simulink
Acceso abierto

Bidirectional DC–AC Converter-Based Communication Solution for Microgrid

Publicado en línea: 21 Dec 2020
Páginas: 177 - 188

Resumen

Abstract

The communication system of a microgrid can transfer the information of electricity price, power consumption and so on between users and the control centre. This capability is of great significance to improve the efficiency and sustainability of power facilities. In this paper, a bidirectional DC–AC converter topology is proposed to achieve the composite transmission of power and signals in microgrids. Since the transmitted signals are modulated by power switches of converters and integrated into the currents, the cost of signal couplers can be saved and the circuit structure can be simplified. In order to verify the feasibility of the proposed method, a simulation model of the proposed converter is implemented in MATLAB/Simulink. With the power supply frequency of 50 Hz, when the converter operates in the inverter mode and rectifier mode, the data transmission rate can reach 120 bit/s and 48 bit/s, respectively.

Palabras clave

  • bidirectional DC–AC converter
  • frequency shift keying
  • MATLAB simulation
  • microgrid
  • two-way communication
Acceso abierto

Simple Technique of Initial Speed Identification for Speed-Sensorless Predictive Controlled Induction Motor Drive

Publicado en línea: 31 Dec 2020
Páginas: 189 - 198

Resumen

Abstract

This article presents a simple technique of identifying the initial speed that allows for restarting a sensorless induction motor (IM) drive controlled by a model predictive flux control (MPFC). Initial speed identification is required because, according to the research, the applied current-model reference adaptive system (C-MRAS) can restart the IM after failure only if the error of the initial speed set in the estimator is <25%. The proposed technique is based on short periods of flux generation for the certain initial speed and observation of the estimated torque respond. The direction of the estimated torque determines whether the real speed is higher or lower than the initial one set in the estimator. In two steps, the algorithm identifies the initial speed with an accuracy of 25%. This allows for a quick restart of the IM from any speed, eliminating the disadvantage of the sensorless drive control system with the C-MRAS speed estimator. The experimental results measured on a 50 kW drive which illustrates the operation and performances of the system are presented.

Palabras clave

  • induction motor
  • sensorless control
  • model predictive control
  • MRAS estimators
  • initial speed identification
  • restarting IM
Acceso abierto

Sensorless Induction Motor Drive Based on Model Reference Adaptive System Scheme Utilising a Fictitious Resistance

Publicado en línea: 31 Dec 2020
Páginas: 199 - 213

Resumen

Abstract

This article presents a new development of an indirect stator flux-oriented controller for sensorless speed induction motor drive utilising instantaneous and steady-state values, respectively, of a fictitious resistance symbolised as R_f. The dimension of the fictitious quantity, in this context, is the ohm, which is the difference between the stator d- and q-axis fictitious resistances. However, from the measurement of the stator voltage and currents of the machine, two independent resistance estimators are built. Therefore, the first is considered as a reference model of the induction machine (IM), and the second is considered as an adjustable model. Subsequently, the error between the states of the two models is used to drive a suitable adaptation mechanism that generates the estimation of the speed, for the adjustable model. Furthermore, the structure of the proposed estimator is free from stator resistance and eliminates the requirement of any flux computation. All the detailed simulation study is carried out in MATLAB/Simulink to validate the proposed method and to highlight the robustness and the stability of the proposed model reference adaptive system estimator.

Palabras clave

  • indirect stator flux-oriented controller (ISFOC) model
  • model reference adaptive system (MRAS)
  • fictitious resistance
  • rotor speed estimation
  • induction motor (IM)
Acceso abierto

Design and Simulation of Direct and Indirect Back EMF Sliding Mode Observer for Sensorless Control of PMSM

Publicado en línea: 28 Dec 2020
Páginas: 215 - 228

Resumen

Abstract

This article compares two sensorless control algorithms for a permanent magnet synchronous machine (PMSM) based on the back-EMF sliding mode observer (SMO). Indirect SMO (I-SMO) treats the back-EMF voltages as a disturbance. Direct SMO (D-SMO) considers back-EMF voltages as state-space variables. The same phase-locked loop (PLL) is used for both observers for extraction of the rotor position and speed values from the observed back-EMF voltages. In a sensorless control, the observed speed is used as feedback for the PI controller, and the observed position is used in the Park transformations. Both observers have been implemented and tested with standard field-oriented control. Simulation results indicate rather comparable speed and position estimation precision for both, but the D-SMO indicates slightly higher precision in steady-state. Even more, a tuning procedure of the D-SMO is more straightforward when compared to the I-SMO. Thus, the D-SMO was further verified experimentally with the OP 5600 rapid prototyping device and with a 350 W PMSM drive. Experimental results of the D-SMO are included at the end of the paper.

Palabras clave

  • back-EMF sliding mode observer
  • sensorless control
  • PMSM
  • phase-locked loop
Acceso abierto

Design and Simulation of Cyclic Battery Tester

Publicado en línea: 28 Dec 2020
Páginas: 229 - 241

Resumen

Abstract

The paper presents an approach to the modelling of a cyclic battery tester and contains observations about lithium-ion (Li-ion) batteries, charging/discharging procedures, conditions and protections which must be observed during the testing process. The main goal was to create and simulate a schematic which will be capable of cyclically testing Li-ion battery cells. Regulation of the final schematic is based on cascade connections of operation amplifiers, which work as a voltage source with current-limiting functions. The power part is created by two MOSFETs connected as a half-bridge. This topology allows current to flow in both directions (from and to the battery). Final simulation is supplemented by protections such as reverse polarity protection, short circuit protection and overvoltage protection during charging. Proper operation of the whole connection is demonstrated by the simulation outputs in the final section.

Palabras clave

  • battery
  • cell
  • charging
  • discharging
  • Simscape

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