Power Electronics
S. Ebrahimzadeh; F. Sedaghati; H. Dolati
Abstract
Background and Objectives: To achieve zero carbon emissions, renewable energy sources have gained noteworthy regard due to their dependable performance, cost efficiency, and adaptability within systems. Increasing adoption of renewable energy sources and electric vehicle (EV) has led to a growing need ...
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Background and Objectives: To achieve zero carbon emissions, renewable energy sources have gained noteworthy regard due to their dependable performance, cost efficiency, and adaptability within systems. Increasing adoption of renewable energy sources and electric vehicle (EV) has led to a growing need for enhanced voltage boost capability. Nevertheless, most of DC sources such as solar cells have a restricted capacity for boosting power. Multilevel inverters can operate as interfaces. In this study, two topologies of switched-capacitor multilevel inverters (SC-MLI) is suggested to overcome the mentioned constraints.Methods: Each stage of the introduced SC-MLI comprises a capacitor, a DC voltage supply, a diode, and two power electronic switches. A comprehensive analysis of the operational principles, and the characteristics of the presented converter, including its charging and discharging behaviors, are provided. Furthermore, the phase-disposition pulse width modulation (PD-PWM) technique is employed to generate the output voltage waveform of the introduced multilevel SC inverter.Results: In the recommended topologies, the quantity of semiconductor power switches, isolated DC voltage supply, diodes, and so, volume and cost of the overall system are decreased in compare to similar SC-MLI topologies. The voltage across the capacitors is self-balanced accurately without using any auxiliary circuits or closed-loop systems. To validate the proposed SC-MLI's effective operation, the implemented topology's simulation and measurement results are presented. The total harmonic distortion for the 17-level inverter using the PD-PWM technique at a modulation index 1 obtained 6.97%. Conclusion: Comprehensive comparative analysis reveals that the introduced topologies have merits and superior performance compared to existing solutions regarding component number, voltage boost factor (BF), and voltage stress. Also, simulation and experimental test results verify theoretical analysis.
Power Electronics
M. Nabizadeh; P. Hamedani; B. Mirzaeian Dehkordi
Abstract
Background and Objectives: Due to the disadvantages of the traditional AC-DC-AC converters, especially in electric drive applications, Matrix Converters (MCs) have been widely researched. MCs are well-known structures that remove the DC-Link capacitor and provide bidirectional power flow, while also ...
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Background and Objectives: Due to the disadvantages of the traditional AC-DC-AC converters, especially in electric drive applications, Matrix Converters (MCs) have been widely researched. MCs are well-known structures that remove the DC-Link capacitor and provide bidirectional power flow, while also giving the ability to control reactive power flow, which the AC-DC-AC converter lacks. Methods: In this work, Model Predictive Current Control (MPCC) is utilized in conjunction with the MC to provide more versatility and controllability than traditional control methods. The work endeavors to investigate the current control of the MC utilizing the finite control set Model Predictive Control (MPC) approach. Results: Current tracking performance, reactive power control, and switching frequency minimization have been included in the objective function of the controller. Moreover, the results have been compared to the traditional AC-DC-AC converters under similar circumstances. The MC can reduce the switching frequency by 40% compared to the AC-DC-AC converter while maintaining the same current THD value. Additionally, it achieves a 58% reduction in current THD compared to the AC-DC-AC converter at the same average switching frequency. However, in the MC, the mitigation of reactive power and the reduction in switching frequency have opposing effects on the current tracking performance.Conclusion: This work proposes an MPCC method for the MC with an RL load, effectively controlling load current and reactive power. The reduction of switching commutations was also evaluated using different weighting factors in the prediction strategy for both the MC and AC-DC-AC converters. Simulation results demonstrate that the MC outperforms the AC-DC-AC converter in dynamic response and reactive power control.
Power Electronics
P. Hamedani
Abstract
Background and Objectives: To overcome the disadvantages of the traditional two-level inverters, especially in electric drive applications, multi-level inverters (MLIs) are the widely accepted solution. Diode-Clamped Inverters (DCIs) are a well-known structure of multi-level inverters. In DCIs, the voltage ...
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Background and Objectives: To overcome the disadvantages of the traditional two-level inverters, especially in electric drive applications, multi-level inverters (MLIs) are the widely accepted solution. Diode-Clamped Inverters (DCIs) are a well-known structure of multi-level inverters. In DCIs, the voltage balance of the DC-link capacitors and the Common Mode (CM) voltage reduction are two important criteria that should be considered. Methods: This paper concentrates on the current control of 3-phase 4-level DCI with finite control set model predictive control (MPC) strategy. Current tracking performance, DC-link capacitor voltage balance, switching frequency minimization, and CM voltage control have been considered in the objective function of the MPC. Moreover, the multistep prediction method has been applied to improve the performance of the DCI. Results: The effectiveness of the proposed multistep prediction control for the 4-level DCI has been evaluated with different horizon lengths. Moreover, the effect of several values of weighting factors has been studied on the system behavior. Conclusion: Results validate the accuracy of current tracking and voltage balancing in the suggested multistep MPC for the 4-level DCI. In addition, CM voltage control and switching frequency reduction can be included in the predictive control. Decreasing the CM voltage and switching frequency will oppositely affect the dynamic behavior and voltage balancing of the DCI. Therefore, selection of weighting factors depends on the system needs and requirements.
Power Electronics
F. Sedaghati; S. A. Azimi
Abstract
Background and Objectives: {R1-1} Increasing environmental problems have led to the spread of Electric Vehicles (EVs). One of the attractive research fields of electric vehicles is the charging battery of this strategic product. Electric vehicle battery chargers often lack bidirectional power flow and ...
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Background and Objectives: {R1-1} Increasing environmental problems have led to the spread of Electric Vehicles (EVs). One of the attractive research fields of electric vehicles is the charging battery of this strategic product. Electric vehicle battery chargers often lack bidirectional power flow and the flexibility to handle a wide range of battery voltages. This study proposes a non-isolated bidirectional DC-DC converter connected to a T-type converter with a reduced number of switches to solve this limitation.Methods: The proposed converter uses a DC-DC converter that has an interleaved structure along with a three-level T-type converter with a reduced number of switches and a common ground for the input and output terminals. Space vector pulse width modulation (SVPWM) and carrier based sinusoidal pulse width modulation (CBPWM) control the converter for Vehicle to grid (V2G) and grid to Vehicle (G2V) operation, respectively.Results: Theoretical analysis shows 96.9% efficiency for 15.8kW output power and 3.06% THD during charging with low battery voltage ripple. In V2G mode, it achieves an efficiency of 96.5% while injecting 0.5 kW of power into the 380 V 50 Hz grid. The DC link voltage is stabilized. The proposed converter also provides good performance for a wide range of battery development.Conclusion: The proposed converter offers high efficiency and cost reduction. It provides the possibility of charging a wide range of batteries and provides V2G and G2V power flow performance. The proposed converter is capable of being placed in the fast battery charging category. The ability to charge two batteries makes it a suitable option for charging stations.
Power Electronics
F. Sedaghati; S. Ebrahimzadeh; H. Dolati
Abstract
Background and Objectives: Increasing environmental problems and challenges have led to increased use of renewable energy sources such as photovoltaic or PV system. One of the attractive research fields is power electronic converters as interfaces for renewable energy sources. Multilevel inverters can ...
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Background and Objectives: Increasing environmental problems and challenges have led to increased use of renewable energy sources such as photovoltaic or PV system. One of the attractive research fields is power electronic converters as interfaces for renewable energy sources. Multilevel inverters can operate as such interfaces. This paper introduces modified topologies of switched-capacitor multilevel inverters, designed to overcome constraints of low voltage renewable energy sources such as PV. Methods: Configuration of topologies utilize a single DC source with series or parallel connection of capacitors to produce 7-level, 9-level, and 11-level voltage in the converter load side. The paper presents the converter operation principle, elements voltage stress analysis, and capacitor sizing calculations. Also, operation analysis of suggested inverter topologies is validated using implemented set up. Results: Comprehensive comparative analysis reveals that the proposed topologies have merits and superior performance compared to existing solutions regarding component number, voltage boost factor, and voltage stress. The experimental measurement results confirm the accuracy of multilevel output voltage waveforms and the self-balancing of capacitor voltages, as predicted by theoretical analysis.Conclusion: The suggested switched-capacitor multilevel inverters, moreover the superiority over previously presented topologies, show great potential for application in photovoltaic systems and electric vehicle battery banks.
Power Electronics
P. Hamedani; M. Changizian
Abstract
Background and Objectives: Model predictive control (MPC) is a practical and attractive control methodology for the control of power electronic converters and electrical motor drives. MPC has a simple structure and enables the simultaneous consideration of different objectives and constraints. However, ...
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Background and Objectives: Model predictive control (MPC) is a practical and attractive control methodology for the control of power electronic converters and electrical motor drives. MPC has a simple structure and enables the simultaneous consideration of different objectives and constraints. However, when applying MPC for multilevel inverters (MLIs), especially at higher voltage levels, the number of switching states dramatically increases. This issue becomes more severe when MLIs are used to supply electrical motor drives.Methods: This paper proposes three different MPC strategies that reduce the number of iterations and computation burden in a 3-phase 4-level flying capacitor inverter (FCI). Traditional MPC with a reduced number of switching conditions, split MPC, and hybrid MPC-PWM control are investigated in this work.Results: In all methods, the capacitor voltages of the FCI are balanced during different operational conditions. The number of iterations is reduced from 512 in traditional MPC to at least 192 in the split MPC. Moreover, the split MPC strategy eliminates the usage and optimization of weighting factors for capacitors voltage balance. However, in the hybrid MPC-PWM control method in comparison to other methods, the voltage balancing time is much lower, the phase current tracks the reference more accurately, the transient time is lower, and the efficiency is higher. In addition, the capacitors voltage ripple is negligible in the hybrid MPC-PWM control method.Conclusion: Simulation results manifest the effectiveness of the suggested hybrid MPC-PWM methodology. Results manifest that the hybrid MPC-PWM control offers perfect dynamic characteristics and succeeds in maintaining the voltage balance during different operational conditions.
Power Electronics
P. Hamedani; S. S. Fazel; M. Shahbazi
Abstract
Background and Objectives: Modeling and simulation of electric railway networks is an important issue due to their non-linear and variant nature. This problem becomes more serious with the enormous growth in public transportation tracks and the number of moving trains. Therefore, the main aim of this ...
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Background and Objectives: Modeling and simulation of electric railway networks is an important issue due to their non-linear and variant nature. This problem becomes more serious with the enormous growth in public transportation tracks and the number of moving trains. Therefore, the main aim of this paper is to present a simple and applicable simulation method for DC electric railway systems.Methods: A train movement simulator in a DC electric railway line is developed using Matlab software. A case study based on the practical parameters of Isfahan Metro Line 1 is performed. The simulator includes the train mechanical movement model and power supply system model. Regenerative braking and driving control modes with coasting control are applied in the simulation.Results: The simulation results of the power network are presented for a single train traveling in both up and down directions. Results manifest the correctness and simplicity of the suggested method which facilitates the investigation of the DC electric railway networks.Conclusion: According to the results, the train current is consistent with the electric power demand of the train. But the pantograph voltage has an opposite relationship with its electric power demand. In braking times, the excess power of the train is injected into the electrical network, and thus, overvoltage and undervoltage occur in the overhead contact line and the substation busbar. Therefore, at the maximum braking power of the train, the pantograph voltage reaches its maximum. The highest amount of fluctuation is related to the substation that is closest to the train. As the train moves away from the traction substations, the voltage fluctuations decrease and vice versa.
Power Electronics
S.H. Zahiri; S. M. Naji Esfahani; M. Delshad
Abstract
Background and Objectives: The interleaved approach has a long history of use in power electronics, particularly for high-power systems. The voltage and current stress in these applications exceed the tolerance limit of a power element. The present paper introduces an improved version of an interleaved ...
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Background and Objectives: The interleaved approach has a long history of use in power electronics, particularly for high-power systems. The voltage and current stress in these applications exceed the tolerance limit of a power element. The present paper introduces an improved version of an interleaved boost converter, which uses voltage mode control. The objectives of this research are improvement in the interleaved boost converter’s performance in terms of the temporal parameters associated with settling duration, rising time, and overshoot.Methods: An improved PI controller (proportional integral controller) is used for adjusting the proposed converter’s output voltage. In the present work, the Grey Wolf Optimization algorithm with aggregation function definition (GWO_AF) is utilized to adjust the free coefficients of the PI controller. In reality, the closed-loop dynamic performance and stability can be improved by designing and implementing an optimized PI controller.Results: The improvement of the freedom degree in the interleaved boost converter resulted from the existence of a few power switches in a parallel channel in the proposed circuit. An additional advantage of the interleaved boost converter, compared to the conventional one, is that it produces a lower output voltage ripple. Conclusion: The usage of multi-objective optimization algorithms in designing a PI controller can significantly improve the performance parameters of an interleaved boost converter. Also, our findings indicated the excellent stability of the proposed converter when connected to the network.
Power Electronics
M. Moradi; R. Havangi
Abstract
Background and Objectives: Traction system and adhesion between wheel and rail are fundamental aspects in rail transportation. Depending on the vehicle's running conditions, different levels of adhesion are needed. Low adhesion between wheel and rail can be caused by leaves on the line or other ...
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Background and Objectives: Traction system and adhesion between wheel and rail are fundamental aspects in rail transportation. Depending on the vehicle's running conditions, different levels of adhesion are needed. Low adhesion between wheel and rail can be caused by leaves on the line or other contaminants, such as rust or grease. Low adhesion can occur at any time of year especially in autumn, resulting in disruptions to passenger journeys. Increased wheel-rail adhesion for transit rail services results in better operating performance and system cost savings. Deceleration caused by low adhesion, will extend the braking distance, which is a safety issue. Because of many uncertain or even unknown factors, adhesion modelling is a time taking task. Furthermore, as direct measurement of adhesion force poses inherent challenges, state observers emerge as the most viable choice for employing indirect estimation techniques. Certain level of adhesion between wheel and rail leads to reliable, efficient, and economical operation.Methods: This study introduces an advantageous approach that leverages the behavior of traction motors to provide support in achieving control over wheel slip and adhesion in railway applications. The proposed method aims to enhance the utilization of existing adhesion, minimize wheel deterioration, and mitigate high creep levels. In this regard, estimation of wheel-rail adhesion force is done indirectly by concentrating on induction motor parameters as railway traction system and dynamic relationships. Meanwhile, in this study, we focus on developing and applying the sixth-order Extended Kalman Filter (EKF) to create a highly efficient sensorless re-adhesion control system for railway vehicles.Results: EKF based design is compared with Unscented Kalman Filter (UKF) based and actual conditions and implemented in Matlab to check the accuracy and performance ability for state and parameter estimation. Experimental results showed fast convergence, high precision and low error value for EKF.Conclusion: The proposed technique has the capability to identify and assess the current state of local adhesion, while also providing real-time predictions of wear. Besides, in combination with control methods, this approach can be very useful in achieving high wheel-rail adhesion performance under variable complex road conditions
Power Electronics
S. Mukherjee
Abstract
Background and Objectives: The increasing requirement of different voltage and power levels in various power electronics applications, especially based on renewable energy, is escalating the growth of the different DC-DC converter topologies. Besides single-input single-output (SISO), multi-input multi-output ...
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Background and Objectives: The increasing requirement of different voltage and power levels in various power electronics applications, especially based on renewable energy, is escalating the growth of the different DC-DC converter topologies. Besides single-input single-output (SISO), multi-input multi-output (MIMO) type topologies become famous. So, in this paper, a Single-Ended Primary Inductance Converter (SEPIC), Cuk and Canonical Switch Cell (CSC) based single-input multi-output (SIMO) boost converter is proposed with a maximum power point tracking (MPPT) controller.Methods: The Design of the three different DC-DC converter-based SIMO topology has been developed and thereafter the operation of the proposed converter is verified with Solar Photovoltaic (SPV), connected as an input to the converter. To extract maximum power from the SPV and MPPT controller is also developed. Finally, the converter's transfer function is developed using small-signal analysis and the system's stability is analyzed with and without compensation.Results: A MATLAB simulation has been done to verify the theoretical analysis. Successful extraction of the maximum power from the SPV panel (65W, Vmpp 18.2V, Impp = 3.55A) with Particle Swarm Optimization (PSO) is verified. SEPIC and Cuk-based DC-DC converter can successfully operate in boost mode with a gain of 2.66. A significant reduction in the Cuk converter capacitor voltage ripple is also established.Conclusion: So, this paper represents an SPV-fed SIMO boost converter based on SEPIC Cuk CSC topology. In addition to that, a PSO-based MPPT controller is also introduced for maximum power extraction. Verification of the theoretical analysis with simulation results is also described.
Power Electronics
H. Salimi; A. Zakipour; M. Asadi
Abstract
Background and Objectives: Permanent magnet synchronous motors (PMSM) have received much attention due to their high torque as well as low noise values. However, several PI blocks are needed for field, torque, and speed control of the PMSM which complicates controller design in the vector control approach. ...
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Background and Objectives: Permanent magnet synchronous motors (PMSM) have received much attention due to their high torque as well as low noise values. However, several PI blocks are needed for field, torque, and speed control of the PMSM which complicates controller design in the vector control approach. To cope with these issues, a novel analytical approach for time-response shaping of the Pi controller in the filed oriented control (FOC) of the PMSM is presented in this manuscript. In the proposed method, it is possible to design the controlling loops based on the pre-defined dynamic responses of the motor speed and currents in dq axis. It should be noted that as decoupled model of the motor is employed in the controller development, a closed loop system has a linear model and hence, designed PI controllers are able to stabilize the PMSM in a wide range of operation.Methods: To design the controllers and choose PI gains, characteristic of the closed loop response is formulated analytically. According to pre-defined dynamic responses of the motor speed and currents in dq-axis e.g., desired maximum overshoot and rise-time values, gains of the controllers are calculated analytically. As extracted equation set of the controller tuning includes a nonlinear term, the Newton-Raphson numerical approach is employed for calculation of the nonlinear equation set. In addition, designed system is evaluated under different tests, such as step changes of the references. Finally, it should be noted that as the decoupled models are employed for the PMSM system, hence exact closed loop behavior of the closed loop system can be expressed via a linear model. As a result, stability of the proposed approach can be guaranteed in the whole operational range of the system.Results: Controlling loops of the closed loop system are designed for speed control of the PMSM. To evaluate accuracy and effectiveness of the controllers, it has been simulated using MATLAB/Simulink software. Moreover, the TMS320F28335 digital signal processor (DSP) from Texas Instruments is used for experimental investigation of the controllers.Conclusion: Considering the simulation and practical results, it is shown that the proposed analytical approach is able to select the controlling gains with negligible error. It has shown that the proposed approach for rise time and overshoot calculations has at most 0.01% for step response of the motor speed at 500 rpm.
Power Electronics
R. Nasrollahi; H. Feshki Farahani; M. Asadi; M. Farhadi-Kangarlu; P. Amiri
Abstract
Background and Objectives: Due to the increased sensitive loads, improving power quality in distribution grids by custom power tools is one of the important fields of electrical engineering. This paper proposes a new kind of three-phase three-wire dynamic voltage restorer (without including storage sources ...
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Background and Objectives: Due to the increased sensitive loads, improving power quality in distribution grids by custom power tools is one of the important fields of electrical engineering. This paper proposes a new kind of three-phase three-wire dynamic voltage restorer (without including storage sources or DC link) and also its control method.Methods: The proposed structure includes an AC/AC converter, low-pass filters at the input and output sides, and three-phase injection transformers. The control system is based on the combination of feedback and feedforward control that its advantages are high speed, good response quality, and very simple implementation. To overcome the harmonics raised from AC/AC converter switching on the main line, a SOGI-PLL has been used. Also, SOGI-PLL operates independently on each phase so that the asymmetric voltage variations can be identified.Results: The proposed control method is capable to compensate the power quality problems such as voltage sag, swell, and harmonics in balanced and unbalanced conditions. The detailed modelling and design of the proposed controller are verified through computer simulations and experimental results under different operating conditions. Simulation and experimental results show that the proposed control strategy can compensate the power quality events as close as possible to the desired values under different operation modes.Conclusion: In this paper, a three-phase three-wire dynamic voltage restorer (DVR) was assessed using direct AC/AC converters without a supply source and DC link. A control system based on combined feedback and feedforward control (CFBFFC) and SOGI-PLL has been proposed for the DVR. The simulation results on a three-phase 20kV system as well as the experimental results obtained from a single-phase 220V system verified the performance of the DVR and the control system. It was shown that this structure can compensate for 0.5pu voltage sag, above 1pu voltage swell, and all kinds of harmonic faults.
Power Electronics
P. Hamedani; S. Sadr; A. Shoulaei
Abstract
Background and Objectives: The principal aim of this paper is to show an independent vector control of two five-phase Linear Induction Motors (LIMs) that are supplied from a single VSI. Methods: The LIMs are running at the same speed but with different load conditions. This concept can be especially ...
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Background and Objectives: The principal aim of this paper is to show an independent vector control of two five-phase Linear Induction Motors (LIMs) that are supplied from a single VSI. Methods: The LIMs are running at the same speed but with different load conditions. This concept can be especially beneficial in long trains with distributed power. To achieve excellent control characteristics and to reduce the undesirable tension forces between the train mechanical couplers, Fuzzy Logic Controllers (FLCs) have been utilized.Results: As a result, the fault occurrence of the train control systems decreases, and the system reliability increases. The results prove the electrical independence in control of a five-phase two-LIM drive supplied with a single VSI. Furthermore, in the presence of the train mechanical couplers and connections, the application of FLC offers excellent control characteristics and reduces the undesirable tension forces. Furthermore, to obtain a more worthwhile validation of the theoretical results, an experimental set up has been constructed and results have also been presented.Conclusion: According to the results, the undesirable tension forces imposed on train couplers are reduced. Consequently, it leads to higher system efficiency, lower deterioration of the train couplers and connections, greater system reliability, and higher passenger safety and comfort.
Power Electronics
P. Hamedani; A. Shoulaei
Abstract
Background and Objectives: Despite superior privileges that multiphase motors offer in comparison with their three-phase counterparts, in the field of multiphase linear induction motors (LIMs) few studies have been reported until now. To combine the advantages of both multiphase motors and linear induction ...
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Background and Objectives: Despite superior privileges that multiphase motors offer in comparison with their three-phase counterparts, in the field of multiphase linear induction motors (LIMs) few studies have been reported until now. To combine the advantages of both multiphase motors and linear induction motors, this paper concentrates on multiphase LIM drives considering the end effects.Methods: The main contributions of this paper can be divided into two major categories. First, a comparative study has been conducted about the dynamic performance of Fuzzy Logic Controller (FLC) and Genetic-PI controller for a seven-phase LIM drive; and second, because of the superior performance of the FLC method revealed from the results, the harmonic pollution of the FLC based LIM drive has been studied in the case of supplying through a five-level Cascaded H-bridge (CHB) VSI and then compared with the traditional two-level VSI fed one.Results: The five-level CHB-VSI has utilized a multiband hysteresis modulation scheme and the two-level VSI has used the traditional three-level hysteresis modulation strategy. Note that for harmonic distortion assessment both harmonic and interharmonic components are considered in THD calculations.Conclusion: The results validate the effectiveness of the proposed FLC for seven-phase LIM drive supplied with five-level CHB-VSI and guarantee for perfect control characteristics, lower maximum starting current, and significant harmonic and interharmonic reduction.
