POWER ELECTRONICS – IEEE PROJECTS 2019
POWER ELECTRONICS – IEEE PROJECTS 2019
1.A Compact Coupled Inductor for Interleaved Multiphase DC-DC Converters
ABSTRACT
A compact coupled inductor structure is proposed for interleaved multiphase synchronous buck converters used to power computer processors and memories that require high current and fast current flew rate. The new coupled inductor structure reduces the winding resistor power loss and makes it possible to utilize Ferrite magnetic material with low core loss. In the letter, several proposed converter implementations to achieve inverse inductor coupling are illustrated, and inductance and coupling coefficient variations are studied through a simplified reluctance model and Maxwell magnetic simulation. The inductor structure not only can be extended to multiple phases but also can be simplified to single phase. The operation of the inductor is experimentally verified in a two-phase synchronous buck converter at switching frequency of one Mega-Hertz.
2.A Multi-Level Converter with a Floating Bridge for Open-Ended Winding Motor Drive Applications
ABSTRACT
This paper presents a dual three phase open end winding induction motor drive. The drive consists of a three phase induction machine with open stator phase windings and dual bridge inverter supplied from a single DC voltage source. To achieve multi-level output voltage waveforms a floating capacitor bank is used for the second of the dual bridges. The capacitor voltage is regulated using redundant switching states at half of the main dc link voltage. This particular voltage ratio (2:1) is used to create a multi-level output voltage waveform with three levels. A modified modulation scheme is used to improve the waveform quality of this dual inverter. This paper also compares the losses in dual inverter system in contrast with single sided three-level NPC converter. Finally, detailed simulation and experimental results are presented for the motor drive operating as an open loop v/f controlled motor drive and as a closed loop field oriented motor controller.
3.Adapted NSPWM for Single DC-Link Dual-Inverter Fed Open-End Motor with Negligible Low-Order Harmonics and Efficiency Enhancement
ABSTRACT
In this paper, the Near-State PWM (NSPWM), adapted to be implemented in dual-VSI fed open-end motor, is proposed with the aim of mitigating low-order harmonics (which lead to current THD minimization). Two proposed methods are studied in detail such as: (a) fixing Phase Angle Displacement (PAD) between two Voltage Source Inverters (VSIs) to 120° while adjusting Modulation Index (MI); and (b) fixing MI to the pre-determined value (wherein low-order harmonics are highly mitigated) while adjusting PAD. Furthermore, the proposed approaches enhance efficiency by limiting the number of commutations within switching interval. The paper also presents the mathematical approaches to accurately determine low-order harmonic components and switching losses for dual-VSI structure. The experimental setup, including dual-VSI and open-end induction motor, is assembled in the laboratory to evaluate performance of the proposed method. Finally, the simulation results, carried out in the MATLAB/Simulink environment, are found to be in a close agreement with experimental data
4.Advanced Design and Operation Consideration for Close-connected Winding Permanent Magnet Brushless DC Machine
ABSTRACT
Advanced design and operation consideration for the close-connected winding permanent-magnet (PM) brushless DC machine [1] is proposed in this paper, including circulating current elimination, fault tolerant control for the breakdown of power electronic switch, and sensorless control method. With the finite-element analysis (FEA), the influence of machine design parameters on circulating current are investigated. By properly controlling the status of power electronic switches, the coils being connected into the equivalent circuit can be changed to avoid the failure switch. The sensorless control is explored by detecting the zero-crossing point of electromotive force (EMF).
5.An Active Cross-Connected Modular Multilevel Converter (AC-MMC) for Medium-Voltage Motor Drive
ABSTRACT
This paper presents an active cross-connected modular multilevel converter (AC-MMC) based on series-connected half-bridge modules. It is intended for completely enhancing the performance of a medium-voltage motor drive system in the full speed range from standstill to rated speed under all load conditions. The proposed AC-MMC circuit is characterized by the cross connection of upper and lower arm middle taps through a branch of series-connected half-bridge converters, which have an identical voltage and current rating with the sub-modules in upper and lower arms. This cross-connected branch provides a physical power transfer channel for upper and lower arms. By properly controlling the amount of high-frequency current flowing through the cross-connected branch, the power balance between the upper and lower arms is achieved even at a zero/low motor speed under constant torque condition. Meanwhile, no common-mode voltage is introduced in the whole speed range. A control strategy with focus on submodule capacitor voltage control is also proposed in this paper to guarantee the normal converter operation. Simulation results obtained from a 4160-V 1-MW model verify the feasibility of the proposal. Experiments on a downscaled prototype also confirm the validity of the novel circuit and the associated control strategy
6.Adaptive Maximum Power Point Tracking Control Algorithm for Wind Energy Conversion Systems
ABSTRACT
This paper presents an adaptive maximum power point tracking (MPPT) algorithm for small-scale wind energy conversion systems (WECSs) to harvest more energy from turbulent wind. The proposed algorithm combines the computational behavior of hill climb search, tip speed ratio, and power signal feedback control algorithms for its adaptability over wide range of WECSs and fast tracking of maximum power point. In this paper, the proposed MPPT algorithm is implemented by using buck– boost featured single-ended primary inductor converter to extract maximum power from full range of wind velocity profile. Evaluation of the proposed algorithm is done on a laboratory-scaled dc motor drive-based WECS emulator. TMS320F28335, 32-bit floating point digital signal controller, is used to execute the control schemes of the in-lab experimental setup. Experimental results show that tracking capability of the proposed algorithm under sudden and gradual fluctuating wind conditions is efficient and effective.
7.A Quasi-Z-source Integrated Multi-port Power Converter with Reduced Capacitance for Switched Reluctance Motor Drives
ABSTRACT
This paper presents a quasi Z-source integrated multiport converter (ZIMPC) for switched reluctance motor (SRM) drives to reduce the dc link capacitance. In conventional SRM drives, employing multi-phase asymmetrical H-bridge (ASHB) topology, large capacitors are necessary to absorb the transient energy during phase current commutation. However, electrolytic capacitors would affect the lifetime, cost and power density of the drive system. With switch multiplexing technique, a Z-source integrated multiport power converter is derived to achieve power ripple reduction using relatively small capacitance. Corresponding control method is designed and developed for the proposed SRM drive. Also, the ZIMPC can boost the equivalent phase exciting voltage and widen the constant power speed range (CPSR). At last, simulation and experimental results verify the feasibility of the proposed ZIMPC and its superior performance with smaller capacitance as compared with ASHB.
8.A Novel Technique for Two-Phase BLDC Motor to Avoid the Demagnetization
ABSTRACT
Conventional permanent magnet motors operate in both magnetizing (pull) process and reversible demagnetizing (push) process on the recoil line of magnets. Therefore, thin surface permanent magnets may easily undergo a risk of demagnetization at the push process under certain fault conditions, which leads to deterioration of motor performance. Thus, thick magnets, whereas contributing the significantly high cost, are usually used to minimize this risk in the permanent magnet motors. In this paper, a novel operation technique, that involves only the pull process, has been proposed for a unique design of two-phase brushless DC (BLDC) motor to avoid the irreversible demagnetization of the magnets. The motor, operated only in the pull process, is kept away from the push process of the operation. Therefore, the motor sustains its initial magnetic operating point above the knee point during the normal operation as well as under the short circuit fault conditions. Finite element analysis is performed to validate the concept of the proposed technique
9.An Improved Model Predictive Control Scheme for the PWM Rectifier-Inverter System Based on Power-Balancing Mechanism
ABSTRACT
The DC-link voltage fluctuation caused by the change of working state of the load motor has been one of the key issues in the PWM rectifier-inverter system. In this study, an improved model predictive control (MPC) scheme is proposed to address this problem. The MPC is applied to both the rectifier stage and the inverter stage in the system. Direct power control is used in the rectifier stage and the direct torque control is employed in the inverter stage, with the key novelty of the active power reference values being defined by both real-time and periodic compensation power based on the system-level power balance model. Meanwhile, a MPC algorithm based on a two-step prediction is introduced to compensate for the delay of a digital controller. Comparison has been conducted between the proposed scheme and three other methods. Simulation and experimental results show that the proposed control scheme exhibits good performance in both the rectifier stage and the inverter stage with improved dynamic response and suppressed voltage fluctuation of the DC-link voltage
10.Dual Inverter Fed Pole-Phase Modulated Nine-Phase Induction Motor Drive with Improved Performance
ABSTRACT
Typical value of rated phase voltage of pole phase modulated multiphase induction motor (PPMMIM) drives with wider speed range is in the order of few hundreds of kilo volts. This high value of phase voltage for high power density applications results in higher dc link voltage requirement and switch voltage rating of twolevel multiphase inverter. Further, using multiphase space vector pulse width modulation (SVPWM) yields less dc link utilization. Methods to increase dc link utilization using SVPWM with offset value of third harmonic order introduces dominant lower order harmonic currents into phase windings. One more major problem in high pole mode of PPMMIMs is higher torque pulsation due to decrease in phase number. To address these problems this paper proposes a dual inverter based multilevel voltage excitation scheme for nine-phase PPMMIM with 1:3 speed ratio. In four-pole mode a simple phase grouping technique to eliminate lower order harmonic currents in the phase windings is proposed. In addition each inverter feeding these phase groups is modulated using carrier based three-phase SVPWM to achieve higher dc link utilization. This paper also proposes a multilevel voltage generation scheme for twelve-pole mode of operation using carrier phase shifted PWM for inherently available equal voltage profile coils (EVPCs) with the same dual inverter structure. The torque ripple using phase shifted carriers PWM and single carrier PWM are compared. Finite element method (FEM) model of ninephase PPMMIM is developed in Ansys Maxwell twodimension (2-D) and is co-simulated with three threephase dual inverters in Simplorer environment. Experimental validation is done for linear and over modulation case on 9ФIM fed from three three-phase dual inverters controlled using Spartan 6 field programmable gate array (FPGA) board programed in VHDL.
11.Extremely Sparse Parallel AC-Link Universal Power Converters
ABSTRACT
Parallel ac-link universal power converters are a relatively new class of power converters that can be configured as dc-dc, dc-ac, ac-dc, and ac-ac. These converters are extensions of a buck-boost converter in which the current of the inductor is alternating and the input and output can have any number of phases with any forms, voltage amplitude, or frequency. By placing a small capacitor in parallel with the link inductor all the switches can benefit from soft switching. The main limitation of the parallel ac-link universal power converter is its large number of switches. A three-phase ac-ac configuration requires 24 unidirectional switches. This paper proposes two topologies based on the parallel ac-link universal power converters that significantly reduce the number of switches. One of the proposed topologies reduces the number of switches in a three-phase ac-ac configuration to 16. The other topology reduces the number of switches to 10. The latter can offer galvanic isolation with only a single-phase high frequency transformer. This paper presents the principles of the operation of the proposed topologies and evaluates them through simulation and experiments.
12.Energy Consumption of Geared DC Motors in Dynamic Applications: Comparing Modeling Approaches
ABSTRACT
In recent years, many works have appeared which present novel mechanical designs, control strategies or trajectory planning algorithms for improved energy efficiency. The actuator model is an essential part of these works, since the optimization of energy consumption strongly depends of the accuracy of this model. Nevertheless, various authors follow very different approaches, often neglecting speed- and load-dependent losses and inertias of components such as the motor and the gearbox. Furthermore, there is no consensus on how negative power affects power consumption. Some authors calculate energy consumption by integrating the electrical power entirely, by integrating its absolute value, or by integrating only positive power. This paper assesses how well commonly used models succeed in predicting the energy consumption of an 80 W geared DC motor performing a dynamic task, by comparing the results they produce to experimental baseline measurements.
13.Derivation of Dual-Switch Step-Down DC/DC Converters with Fault-Tolerant Capability
ABSTRACT
This paper presents a graph theoretic approach to deriving a family of dual-switch step-down dc/dc converters with fault-tolerant capability. The constraints set in the derivation process ensure minimum additional component is used to achieve fault-tolerant operation. The operation of converters derived is flexible. Under normal operating conditions, one of the two switches can serve as a main switch to control the power flow (i.e. single-switch converter operation) and the other switch is in stand-by mode. When a fault occurs on the main switch, the other switch will be activated to provide an alternate current path to continue converter operation and maintain output regulation. The fault-tolerant converters are derived by integrating a buck converter with a buck-boost converter. They share all the components except for the power switches. Due to different duty cycles required between the two operating conditions, a feedback controller is necessary to adjust the duty cycle for tight output regulation. The derivation procedure and experimental results on fault occurence are reported. The converter derivation approach is able to identify reported topologies and can be extended to synthesize other topologies with fault-tolerent capability.
14.Analysis of the Integrated SEPIC-Flyback Converter as a Single-Stage Single-Switch Power-Factor-Correction LED Driver
ABSTRACT
This paper proposes a new isolated single-stage single-switch power-factor-correction (S4 PFC) driver for supplying light emitting diodes (LEDs) without electrolytic capacitor. In the proposed LED driver, the switch turns on under zero current switching (ZCS) condition. Also, it turns on at a voltage less than its nominal voltage stress and, therefore, the switch capacitive turn-on loss decreases too much extent. The leakage energy is absorbed, so there are no voltage spikes across the switch when the switch turns off. In this paper, operating principles of the proposed driver are discussed and design considerations are presented. Also, a laboratory prototype for supplying a 21W/30V LED module from 220Vrms/50Hz AC mains is implemented and experimental results are presented to verify the theoretical analysis.
15.Design and Implementation of a Novel Multilevel DC-AC Inverter
ABSTRACT
In this paper, a novel multilevel DC-AC inverter is proposed. The proposed multilevel inverter generates seven levels AC output voltage with the appropriate gate signals design. Also, the low pass filter is used to reduce the total harmonic distortion of the sinusoidal output voltage. The switching losses and the voltage stress of power devices can be reduced in the proposed multi-level inverter. The operating principles of the proposed inverter and the voltage balancing method of input capacitors are discussed. Finally, a laboratory prototype multilevel inverter with 400 V input voltage and output 220 Vrms /2 kW is implemented. The multilevel inverter is controlled with sinusoidal pulse-width modulation (SPWM) by TMS320LF2407 digital signal processor (DSP). Experimental results show that the maximum efficiency is 96.9% and the full load efficiency is 94.6%.
16. BLDC Motor Driven Solar PV Array Fed Water Pumping System Employing Zeta Converter
ABSTRACT
This paper proposes a simple, cost effective and efficient brushless DC (BLDC) motor drive for solar photovoltaic (SPV) array fed water pumping system. A zeta converter is utilized in order to extract the maximum available power from the SPV array. The proposed control algorithm eliminates phase current sensors and adapts a fundamental frequency switching of the voltage source inverter (VSI), thus avoiding the power losses due to high frequency switching. No additional control or circuitry is used for speed control of the BLDC motor. The speed is controlled through a variable DC link voltage of VSI. An appropriate control of zeta converter through the incremental conductance maximum power point tracking (INC-MPPT) algorithm offers soft starting of the BLDC motor. The proposed water pumping system is designed and modeled such that the performance is not affected under dynamic conditions. The suitability of proposed system at practical operating conditions is demonstrated through simulation results using MATLAB/ Simulink followed by an experimental validation.
17. Fault-tolerant Inverter for High-speed 3-Phase BLDC Drives in Aerospace Applications
ABSTRACT
The fault tolerant control of BLDC motor is of great importance for its continuous operating capacity even under the faulty situation. Our proposed work consists of a fault tolerant topology composed of an additional phase leg which contains 6 Triacs act as fault Switching Circuit and a fault protective circuit for the high-speed low-inductance BLDC motor. This fault protective circuit consists of Mosfet gate that is driven by using PWM technique. Input DC voltage is given to Buck Boost converter and it working is if the voltage level less than the required voltage level converter act as boost converter and produce required output. If the Input voltage level is more converters reduces the voltage obtained from the converter. Buck Boost converter having switches (Mosfet) which used to isolate fault switches. The output obtained from fault protector circuit is inverted into 3-Phase DC Output. This 3-Phase Bridge consists of 6 Mosfet which is driven by Digital Pulses. Based on this pulses 3-Phase motor rotation happens either clockwise or anticlockwise direction. Speed of 3-Phase motor is controlled by Pulse Width Modulation and motor rotation varies based on percentage of duty cycle that we are giving to it. The method can achieve safe isolation and reconfiguration to avoid the secondary fault caused by direct switch of the redundant switch and the faulty switch after the fault diagnosis process.
18. Integrated DC-DC Converter Design for Electric Vehicle Power trains
ABSTRACT
In this paper, an integrated, reconfigurable DC-DC converter for plugin and hybrid Electric Vehicles (EV) is proposed. The converter integrates functionality for both EV powertrain and charging operation into a single unit. During charging, the proposed converter functions as a DAB converter, providing galvanic isolation. For powertrain operation, the converter functions as an interleaved boost converter. During light load powertrain operation, the efficiency of the converter can be further improved by employing the integrated DAB. The proposed integrated converter does not require any extra relays or contactors for charging and powertrain operation. By using such integration, the overall volume and weight of the power electronics circuits, passives and associated cooling system can be improved. In addition, the power flow efficiency from EV battery to the high voltage DC bus for the motor inverter can be improved. The experimental results of the prototype are presented to verify the functionality of the proposed converter.
19. High Step-Up/Step-Down Soft-Switching Bidirectional DC-DC Converter with Coupled-Inductor and Voltage Matching Control for Energy Storage Systems
ABSTRACT
A soft-switching bidirectional DC-DC converter (BDC) with a coupled-inductor and a voltage doubler cell is proposed for high step-up/step-down voltage conversion applications. A dual-active half-bridge (DAHB) converter is integrated into a conventional buck-boost BDC to extend the voltage gain dramatically and decrease switch voltage stresses effectively. The coupled inductor operates not only as a filter inductor of the buck-boost BDC, but also as a transformer of the DAHB converter. The input voltage of the DAHB converter is shared with the output of the buck-boost BDC. So PWM control can be adopted to the buck-boost BDC to ensure that the voltage on the two sides of the DAHB converter is always matched. As a result, the circulating current and conduction losses can be lowered to improve efficiency. Phase-shift control is adopted to the DAHB converter to regulate the power flows of the proposed BDC. Moreover, zero-voltage-switching is achieved for all of the active switches to reduce the switching losses. The operational principles and characteristics of the proposed BDC are presented in detail. The analysis and performance have been fully validated experimentally on a 40-60V/400V 1kW hardware prototype.
20. On The Robust Control of Parallel-Cascade DC/DC Buck Converter
ABSTRACT
This paper presents the design and simulation of robust control for DC/DC multi-converter based on terms like differential flatness and active disturbance rejection. The main goal of the control law is to obtain a regulated output voltage for each converter in cascade, and a balance of currents for parallel converters. The controller must actively reject the endogenous and exogenous disturbances, i.e. maintaining a robust output. The effectiveness of the proposed controller was verified by computer simulations using MATLAB/Simulink.
21. Single-Phase Grid Connected Motor Drive System with DC-link Shunt Compensator and Small DC-link Capacitor
ABSTRACT
The single-phase diode rectifier system with small DC-link capacitor shows wide diode conduction time and it improves the grid current harmonics. By shaping the output power, the system meets the grid current harmonics regulation without any power factor corrector or grid filter inductor. However, the system has torque ripple and suffers efficiency degradation due to the insufficient DC-link voltage. To solve this problem, this paper proposes the DC-link shunt compensator (DSC) for small DC-link capacitor systems. DSC is located on DC-node parallel and operates as the voltage source, improving the system performances. This circuit helps the grid current-shaping control during grid-connection time, and reduces the flux-weakening current by supplying the energy to the motor during grid-disconnection time. This paper presents a power control method and the design guideline of DSC. The feasibility of DSC is verified by simulation and experimental results.
22. High Performance Solar MPPT Using Switching Ripple Identification Based on a Lock-In Amplifier
ABSTRACT
Photovoltaic (PV) power converters and Maximum Power Point Tracking (MPPT) algorithms are required to ensure maximum energy transfer between the PV panel and the load. The requirements for the MPPT algorithms have increased over the years – the algorithms are required to be increasingly accurate, fast, and versatile, while reducing the intrusiveness on the overall performance of the PV panel and converter. The family of Hill-climbing algorithms such as Incremental Conductance (InCond) and Perturb and Observe (P&O) have gained popularity given their simplicity and accuracy, but they require the injection of a perturbation that changes the operating point even in steady-state and are prone to errors during changing environmental conditions. In recent literature, the use of the switching ripple has been proposed to replace the perturbation in the hill-climbing algorithms given its inherent presence in the system and speed. The constant work towards smaller and faster ripples presents challenges to the signal detection involved in this kind of algorithm. This paper develops and implements a new InCond MPPT technique based on switching ripple detection using a digital Lock-In Amplifier (LIA) to extract the amplitude of the oscillation ripple even in the presence of noise. The use of this advanced technique allows to push forward the reduction of the ripple in order to virtually eliminate the oscillation in steady-state maximizing the efficiency. The accurate detection allows for adaptive-step features for fast tracking of changing environmental conditions while keeping the efficiency at maximum during the steady-state. Detailed mathematical analysis of the proposed technique is provided. Overall, the use of the proposed LIA allows to push the reduction of the ripple even more while keeping accuracy and delivering superior performance. Simulations and experimental results are provided for the proposed technique and the InCond technique in order to validate the proposed approach.
23. Zero-sequence Current Suppression for Open-end Winding Induction Motor Drive with Resonant Controller
ABSTRACT
Open-end winding topology with a common DC source has path for zero-sequence current. Zero-sequence current needs to be suppressed because it does not contribute to the drive torque but has harmful effects such as loss and torque ripple. Both inverter and motor have sources of the zero-sequence component. The zero-sequence source on the inverter side is the voltage error due to dead time in switching. The zero-sequence source on the motor side is the zero-sequence component of the back EMF which consists of the third harmonic. In this paper, the two zero-sequence sources are investigated both theoretically and experimentally for an open-end winding induction motor drive system, and a method to suppress the zero-sequence current suppression is proposed. The voltage error is compensated by feedforward to the reference voltage. The zero-sequence component of the back EMF is compensated by a proportional and resonant controller because its frequency is known while its amplitude and phase offset are unknown
24. High Performance Model Predictive Technique for MPPT of Gird-tied Photovoltaic System Using Impedance-Source Inverter
ABSTRACT
This paper presents a maximum power point tracking (MPPT) method using model predictive technique for a grid-tied photovoltaic harvesting energy system. A single-stage grid-tied Z-source inverter is used for extracting the maximum available power and feeding the power to the grid. The proposed technique predicts the future behavior of the photovoltaic side voltage and current by using a digital observer which estimates the parameters of the photovoltaic module. The proposed method features simultaneously reduction in oscillation around maximum power point (MPP) and fast convergence by adaptively changing the perturbation size using the predicted model of the system. The experimental results demonstrate fast tracking response under dynamic weather condition, small steady state error, small oscillation around MPP at steady state, and high MPPT efficacy for wide range of solar irradiance levels. Additionally, the grid side current total harmonics distortion (THD) meets the IEEE-519 standards.
25. New Equivalent Circuit of the IPM-type BLDC Motor for Calculation of Shaft Voltage by Considering Electric and Magnetic Fields
ABSTRACT
Fast switching and common-mode voltage of the space vector pulse width modulation inverter output create several parasitic capacitances according to the geometry of the motor. The windings emit the electric and magnetic flux inside of the motor. They create capacitance links and electromotive force (EMF) in the shaft, respectively. Those capacitance links and EMF generate a current through two bearings of the shaft and directly reduces the bearing lifetime. In this study, we propose a new design of equivalent circuit taking into account all parasitic capacitor components.
26. Grid Current Shaping Method with DC-link Shunt Compensator for Three-Phase Diode Rectifier-Fed Motor Drive System
ABSTRACT
This paper proposes grid current shaping method using DC-link shunt compensator for three-phase diode rectifier system without electrolytic DC-link capacitor. In the proposed method, the diode rectifier system can satisfy the grid regulation IEC61000-3-12 without any power factor correction circuit or heavy grid filter inductor. The proposed grid current shaping method can be realized by applying DSC with reduced-rating components and without electrolytic capacitor, which is connected parallel to the DC-link. Since DSC has no electrolytic capacitor, the system with DSC has high circuit reliability. Furthermore, DSC can enhance the system efficiency, especially in flux-weakening area, since the motor drive inverter recovers the reduced modulation index which has been spent in the additional control for small passive components. This paper presents the control method for DSC and analyzes the effect of proposed method. The feasibility of proposed method is verified by simulation and experimental results.
27. High Performance Predictive Control of Quasi Impedance Source Inverter
ABSTRACT
The quasi-Z-source inverter (qZSI) has attracted much attention for motor drives and renewable energy applications due to its capability to boost or buck in a single converter stage. However, this capability is associated with different challenges related to the closed loop control of currents, control the DC capacitor voltage, produce three-phase AC output current with high dynamic performance and obtain continuous and low ripple input current. This paper presents a predictive control strategy for a three-phase qZSI that fulfills these requirements without adding any additional layers of control loops. The approach is to improve the overall performance of the converter with a switching strategy that reduces inverter switching losses. The proposed controller implements a discrete-time model of the qZSI to predict the future behavior of the circuit variables for each switching state, along with a set of multi-objective control variables all in one cost function. The quasi impedance network and the AC load are considered together when designing the controller in order to obtain stability of the impedance network with a step change in the output reference. A detailed comparative investigation between the proposed controller and the conventional PI controller is presented to prove the superiority of the proposed method over the conventional control method. Simulation and experimental results are presented.
28. Improved Fault-Tolerant Control for Brushless Permanent Magnet Motor Drives With Defective Hall Sensors
ABSTRACT
Brushless permanent magnet motor drives based on Hall sensors have received significant attention in recent years. In this area, the faults of Hall sensors become a new concern and several fault-tolerant control (FTC) methods have been proposed. However, most of the state-of-the-art FTC methods require some time to reconstruct the correct Hall sensor signals, which results in significant transient currents and speed dip during fault diagnostic process (FDP). In this paper, a new and improved FTC scheme based on FDP and vector-tracking observer is proposed. A method to identify the duration of FDP is proposed based on the analysis of acceleration estimation and the fault diagnosis results. During FDP, the method defaults to an open-loop observer control, which removes the undesirable current/torque transient. After that, the close-loop observer is re-enabled and the motor operation is restored. The proposed FTC is demonstrated in detailed simulations and experimentally on 120° brushless dc motor drives and sinusoidal PM motor drives. For both types of drives, a significant improvement is achieved in steady state and transient operation with faults of up to two Hall sensors, which has not been possible with available alternative FTC approaches (unless a sensorless control is used).
29. Quasi-Resonant (QR) Controller with Adaptive Switching Frequency Reduction Scheme for Flyback Converter
ABSTRACT
A quasi-resonant (QR) controller with an adaptive frequency reduction scheme has been developed for a flyback converter. While maintaining the valley switching, the QR controller reduces the switching frequency for lighter load by skipping some valleys to reduce the power loss and thereby achieve better light load efficiency. If the QR controller cannot detect any valley due to the damped oscillation of switch voltage, the valley switching is given up and the non-valley switching is employed to keep reducing the switching frequency for lighter load. The proposed QR controller has been implemented in a 0.35-μm 700-V BCDMOS process and applied to a 40-W flyback converter. The power efficiency of the flyback converter is improved by upto 3.0-% when the proposed QR controller is employed compared to the one employing the conventional QR controller.
30. Self-correction of Commutation Point for High-speed Sensorless BLDC Motor With Low Inductance and Nonideal Back EMF
ABSTRACT
This paper presents a novel self-correction method of commutation point for high-speed sensorless brushless dc (BLDC) motors with low inductance and nonideal back electromotive force (EMF) in order to achieve low steady-state loss of magnetically suspended control moment gyro (MSCMG). The commutation point before correction is obtained by detecting the phase of EMF zero-crossing point and then delaying 30 electrical degrees. Since the speed variation is small between adjacent commutation points, the difference of the nonenergized phase’s terminal voltage between the beginning and the end of commutation is mainly related to the commutation error. A novel control method based on model-free adaptive control is proposed, and the delay degree is corrected by the controller in real time. Both the simulation and experimental results show that the proposed correction method can achieve ideal commutation effect within the entire operating speed range.
31. Performance Analysis of the Computational Implementation of a Simplified PV Model and MPPT Algorithm
ABSTRACT
In many research centers around the world, had been researched models that accurately represent the PV modules operation. In this context, this paper presents a modeling of photovoltaic modules, which aims to simplify the simulation of photovoltaic systems in MATLAB®/Simulink. The model in question has not been very explored in the literature and, therefore, this paper has the purpose of evaluating its results connecting the model to a boost converter, being its main function the Maximum Power Point Tracking applying one of the most known methods, the P&O (Perturb & Observe). Furthermore, this converter elevates the voltage generated by the photovoltaic modules, in order to connect the PV array to the grid through an inverter. This paper also presents a good correlation between the theoretical and practical results from the proposed modeling and high efficiency of the implemented MPPT algorithm as well.
32. Model Predictive Control Scheme of Five-Leg AC-DC-AC Converter-Fed Induction Motor Drive
ABSTRACT
AC-DC-AC converter-fed induction motor drive is mainly realized by back-to-back three-phase converters. However, fault in a single semiconductor switch will make it inoperative. To enable continued controllable operation in case of the faults occurring in the converter, the five-leg converter with a shared leg between the grid and load sides is a possible solution. However, this topology poses an inherent two-objective control problem because its grid and load sides should be controlled simultaneously. More importantly, the potential increase of the shared-leg current may destroy the converters. In this paper, a new control scheme based on the FCS-MPC combined with intrinsic characteristic of the five-leg converter is proposed for independent control of the rectifier and inverter subsystem with the shared-leg overcurrent constraint. The condition for independent control is analyzed. In order to give a complete evaluation of the proposed control scheme, the conventional PWM control scheme is conducted for comparison. Experimental results are provided to validate the effectiveness of the proposed scheme.