Dissertations / Theses on the topic 'Multiple three-phase motor drives'

This dissertation is devoted to a unified and comprehensive study of zero-current-transition (ZCT) soft-switching techniques for high-power three-phase PWM inverter applications. Major efforts in this study are as follows: 1) Conception of one new ZCT scheme and one new ZCT topology; 2) Systematic comparison of a family of ZCT inverters; 3) Design, implementation and experimental evaluation of two 55-kW prototype inverters for electric vehicle (EV) motor drives that are developed based on the proposed ZCT concepts; and 4) Investigation of the ZCT concepts in megawatts high-frequency power conversions. The proposed ZCT techniques are also applicable to three-phase power-factor-correction (PFC) rectifiers. In order to minimize switching losses, this work first proposes a new control scheme for an existing three-phase ZCT inverter circuit that uses six auxiliary switches. The proposed scheme, called the six-switch ZV/ZCT, enables all main switches, diodes and auxiliary switches to be turned off under zero-current conditions, and in the meantime provides an opportunity to achieve zero-voltage turn-on for the main switches. Meanwhile, it requires no modification to normal PWM algorithms. Compared with existing ZCT schemes, the diode reverse-recovery current is reduced significantly, the switching turn-on loss is reduced by 50%, the resonant capacitor voltage stress is reduced by 30%, and the current and thermal stresses in the auxiliary switches are evenly distributed. However, a big drawback of the six-switch ZV/ZCT topology, as well as of other types of soft-switching topologies using six auxiliary switches, is the high cost and large space associated with the auxiliary switches. To overcome this drawback, this work further proposes a new three-phase ZCT inverter topology that uses only three auxiliary switches-- the three-switch ZCT. The significance of the proposed three-switch ZCT topology is that, among three-phase soft-switching inverters developed so far, this is the only one that uses fewer than six auxiliary switches and still has the following three features: 1) soft commutation for all main switches, diodes and auxiliary switches in all operation modes; 2) no modification to normal PWM algorithms; and 3) in practical implementations, no need for extra resonant current sensing, saturable cores, or snubbers to protect the auxiliary switches. The proposed six-switch ZV/ZCT and three-switch ZCT inverters, together with existing ZCT inverters, constitute a family of three-phase ZCT inverters. To explore the fundamental properties of these inverters, a systematic comparative study is conducted. A simplified equivalent circuit is developed to unify common traits of ZCT commutations. With the visual aid of state planes, the evolution of the family of ZCT inverters is examined, and their differences and connections are identified. Behaviors of individual inverters, including switching conditions, circulating energy, and device/component stresses, are compared. Based on the proposed six-switch ZV/ZCT and three-switch ZCT techniques, two 55-kW prototype inverters for EV traction motor drives have been built and tested to the full-power level with a closed-loop controlled induction motor dynamometer. The desired ZCT soft-switching features are realized together with motor drive functions. A research effort is carried out to develop a systematic and practical design methodology for the ZCT inverters, and an experimental evaluation of the ZCT techniques in the EV motor drive application is conducted. The design approach integrates system optimization with characterizations of the main IGBT device under the ZCT conditions, selection, testing and characterization of the auxiliary devices, design and selection of the resonant inductors and capacitors, inverter loss modeling and numerical analysis, system-level operation aspects, and layout and parasitic considerations. Different design aspects between these two ZCT inverters are compared and elaborated. The complexity of the 55-kW prototype implementations is compared as well. Efficiencies are measured and compared under a group of torque/speed points for typical EV drive cycles. Megawatts high-frequency power conversion is another potential application of the ZCT techniques. The integrated gate commutated thyristor (IGCT) device is tested and characterized under the proposed six-switch ZV/ZCT condition, and the test shows promising results in reducing switching losses and stresses. Improvements in the IGCT switching frequency and simplification of the cooling requirements under ZCT operations are discussed. In addition, a generalized ZCT cell concept is developed based on the proposed three-switch ZCT topology. This concept leads to the discovery of a family of simplified multilevel soft-switching inverters that reduce the number of auxiliary switches by half, and still maintain desirable features.
Ph. D.

Switched reluctance motor (SRM) has become a competitive selection for many applications of electric machine drive systems recently due to its relative simple construction and its robustness. The advantages of those motors are high reliability, easy maintenance and good performance. The absence of permanent magnets and windings in rotor gives possibility to achieve very high speeds (over 10000 rpm) and turned SRM into perfect solution for operation in hard conditions like presence of vibrations or impacts. Such simple mechanical structure greatly reduces its price. Due to these features, SRM drives are used more and more into aerospace, automotive and home applications. The major drawbacks of the SRM are the complicated algorithm to control it due to the high degree of nonlinearity, also the SRM has always to be electronically commutated and the need of a shaft position sensor to detect the shaft position, the other limitations are strong torque ripple and acoustic noise effects.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq)
Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)
Este trabalho apresenta uma nova proposta para sistema de refrigeração com controle dinâmico de temperatura, operando com estrutura de compressor aberto, acionado por motor de indução trifásico com velocidade variável, e estágio de entrada retificador com correção ativa do fator de potência. O estágio de entrada é composto por um retificador Boost monofásico com elevado fator de potência, com duas células entrelaçadas, operando no modo de condução crítica, empregando técnica de comutação não dissipativa e controlado por dispositivo FPGA, associado a um estágio de saída inversor de dois níveis convencional trifásico à IGBT, o qual é controlado por um Processador Digital de Sinais (DSP - Digital Signal Processor). A técnica de comutação não dissipativa para o estágio de entrada é baseada em células ZCS (Zero-current-switching). As principais características do retificador incluem a redução da ondulação da corrente de entrada, redução da ondulação da tensão de saída retificada, utilização de componentes com reduzidos esforços, reduzido volume do filtro de entrada para Interferências Eletromagnéticas (EMI - Electromagnetic Interference), elevado Fator de Potência (FP) e reduzida Distorção Harmônica Total (DHT) da corrente de entrada, atendendo os limites da norma IEC61000-3-2. O controle digital para o estágio de saída inversor foi desenvolvido usando duas diferentes técnicas, incluindo a técnica convencional controle escalar Volts/Hertz (V/Hz) e o controle Vetorial com Orientação pelo Fluxo do estator, com o propósito de verificar a aplicabilidade e a performance dos controles digitais propostos, para o controle contínuo da temperatura, aplicados a um protótipo de sistema de refrigeração.
This work presents a new proposal for refrigeration systems with dynamic control of temperature, working with structure of open compressor, driving a three-phase induction motor with variable speed, and input rectifier with active power factor correction. The proposed system is composed of a single-phase high-power-factor boost rectifier, with two cells in interleaved connection, operating in critical conduction mode, and employing a softswitching technique, controlled by a Field Programmable Gate Array (FPGA), associated with a conventional three-phase IGBT bridge inverter (VSI - Voltage Source Inverter), controlled by a Digital Signal Processor (DSP). The soft-switching technique for the input stage is based on zero-current-switching (ZCS) cells. The rectifier s features include reduction in input current ripple, reduction in output voltage ripple, use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller for the output stage inverter has been developed using two different techniques, the conventional Voltage-Frequency control (scalar V/Hz control), and a simplified stator oriented vector control, in order to verify the feasibility and performance of the proposed digital controls, for continuous temperature control, applied at a refrigerator prototype.

Resumo: Este trabalho apresenta uma nova proposta para sistema de refrigeração com controle dinâmico de temperatura, operando com estrutura de compressor aberto, acionado por motor de indução trifásico com velocidade variável, e estágio de entrada retificador com correção ativa do fator de potência. O estágio de entrada é composto por um retificador Boost monofásico com elevado fator de potência, com duas células entrelaçadas, operando no modo de condução crítica, empregando técnica de comutação não dissipativa e controlado por dispositivo FPGA, associado a um estágio de saída inversor de dois níveis convencional trifásico à IGBT, o qual é controlado por um Processador Digital de Sinais (DSP - Digital Signal Processor). A técnica de comutação não dissipativa para o estágio de entrada é baseada em células ZCS (Zero-current-switching). As principais características do retificador incluem a redução da ondulação da corrente de entrada, redução da ondulação da tensão de saída retificada, utilização de componentes com reduzidos esforços, reduzido volume do filtro de entrada para Interferências Eletromagnéticas (EMI - Electromagnetic Interference), elevado Fator de Potência (FP) e reduzida Distorção Harmônica Total (DHT) da corrente de entrada, atendendo os limites da norma IEC61000-3-2. O controle digital para o estágio de saída inversor foi desenvolvido usando duas diferentes técnicas, incluindo a técnica convencional controle escalar Volts/Hertz (V/Hz) e o controle Vetorial com Orientação pelo Fluxo do estator, com o propósito de verificar a aplicabilidade e a performance dos controles digitais propostos, para o controle contínuo da temperatura, aplicados a um protótipo de sistema de refrigeração.
Abstract: This work presents a new proposal for refrigeration systems with dynamic control of temperature, working with structure of open compressor, driving a three-phase induction motor with variable speed, and input rectifier with active power factor correction. The proposed system is composed of a single-phase high-power-factor boost rectifier, with two cells in interleaved connection, operating in critical conduction mode, and employing a softswitching technique, controlled by a Field Programmable Gate Array (FPGA), associated with a conventional three-phase IGBT bridge inverter (VSI - Voltage Source Inverter), controlled by a Digital Signal Processor (DSP). The soft-switching technique for the input stage is based on zero-current-switching (ZCS) cells. The rectifier’s features include reduction in input current ripple, reduction in output voltage ripple, use of low stress devices, low volume for the EMI input filter, high input power factor (PF), and low total harmonic distortion (THD) in the input current, in compliance with the IEC61000-3-2 standards. The digital controller for the output stage inverter has been developed using two different techniques, the conventional Voltage-Frequency control (scalar V/Hz control), and a simplified stator oriented vector control, in order to verify the feasibility and performance of the proposed digital controls, for continuous temperature control, applied at a refrigerator prototype.
Orientador: Carlos Alberto Canesin
Coorientador: Flávio Alessandro Serrão Gonçalves
Banca: Fabio Toshiaki Wakabayashi
Banca: João Onofre Pereira Pinto
Mestre

Je jasné, že nejúspěšnější konstrukce zahrnuje postup vícefázového řízení, ve kterém každá fáze může být považována za samostatný modul. Provoz kterékoliv z jednotek musí mít minimální vliv na ostatní, a to tak, že v případě selhání jedné jednotky ostatní mohou být v provozu neovlivněny. Modulární řešení vyžaduje minimální elektrické, magnetické a tepelné ovlivnění mezi fázemi řízení (měniče). Synchronní stroje s pulzním tokem a permanentními magnety se jeví jako atraktivní typ stroje, jejíž přednostmi jsou vysoký kroutící moment, jednoduchá a robustní konstrukce rotoru a skutečnost, že permanentní magnety i cívky jsou umístěny společně na statoru. FS-PMSM jsou poměrně nové typy střídavého stroje stator-permanentní magnet, které představují významné přednosti na rozdíl od konvenčních rotorů - velký kroutící moment, vysoký točivý moment, v podstatě sinusové zpětné EMF křivky, zároveň kompaktní a robustní konstrukce díky umístění magnetů a vinutí kotvy na statoru. Srovnání výsledků mezi FS-PMSM a klasickými motory na povrchu upevněnými PM (SPM) se stejnými parametry ukazuje, že FS-PMSM vykazuje větší vzduchové mezery hustoty toku, vyšší točivý moment na ztráty v mědi, ale také vyšší pulzaci díky reluktančnímu momentu. Pro stroje buzené permanentními magnety se jedná o tradiční rozpor mezi požadavkem na vysoký kroutící moment pod základní rychlostí (oblast konstantního momentu) a provozem nad základní rychlostí (oblast konstantního výkonu), zejména pro aplikace v hybridních vozidlech. Je předložena nová topologie synchronního stroje s permanentními magnety a spínaným tokem odolného proti poruchám, která je schopná provozu během vinutí naprázdno a zkratovaného vinutí i poruchách měniče. Schéma je založeno na dvojitě vinutém motoru napájeném ze dvou oddělených vektorově řízených napěťových zdrojů. Vinutí jsou uspořádána takovým způsobem, aby tvořila dvě nezávislé a oddělené sady. Simulace a experimentální výzkum zpřesní výkon během obou scénářů jak za normálního provozu, tak za poruch včetně zkratových závad a ukáží robustnost pohonu za těchto podmínek. Tato práce byla publikována v deseti konferenčních příspěvcích, dvou časopisech a knižní kapitole, kde byly představeny jak topologie pohonu a aplikovaná řídící schémata, tak analýzy jeho schopnosti odolávat poruchám.

碩士
國立中山大學
電機工程研究所
82
At present, the induction motor is the most popular electric machinery. There are considerably control technologies have been developed.This thesis deals with most popular drivers in the present market and the induction motor for establishing their mathematical models. Meanwhile , the characteristics of the drivers also have been simulated in the thesis. From the studies , we can have a better understanding of the effect of the driver equipment and choose adequate power electronics. To avoid disadvantageous effects with respect to the inverter to damage power electronics as a result of the induction motor fault, use data provided from the simulation to reduce the power failure probability or design appropriate protection devices. To make use of the digital simulation of the voltage source inverter, including the six-step、 the square wave PWM、 sinusoid wave PWM and optimal PWM , this thesis presents the analysis of the induction motor under abnormal operation conditions. In addition, built the vector control mathematical models and simulate the good dynamics characteristic, including under- rating speed constant torque operation and over-rating speed constant power operation of the induction motor. The main purpose of using software simulation is to reduce the time of the development of the hardware、save the capital and avoid waste of money and human resource.

碩士
國立臺灣科技大學
電機工程系
104
The thesis focuses on the development of low total harmonic distortion (THD) of current for a six-leg inverter for three-phase permanent-magnet synchronous motor (PMSM) drives. The power circuit of six-leg three-phase inverter will provide independent operation for each phase of PMSM to raise the utilization factor of dc-link voltage. In addition, two types of current harmonics mitigation control are proposed: one for normal operation and the other for the case when single phase winding fault occurs. The former uses current prediction to suppress the zero-axis current, while for the latter, adjusting the phase angle difference of the other two windings to 60 degrees and introducing zero-axis back electro-motive-force compensation will reduce THD of current as well as torque ripple under unbalanced condition. Finally, an auxiliary generator is used to measure the position and speed of the rotor to facilitate the coordinate transformation of feedback current for current and speed closed-loop control. In this thesis, Matlab/Simulink is used to simulate the proposed PMSM drive including current and speed closed-loop control, fault tolerance control as well as harmonic mitigation. The digital signal processor, TMS320F28069, is adopted as the control core and the program is compiled by C language, thereby reducing the circuit components and enhancing the reliability. Experimental evaluation for current harmonics mitigation control is conducted at 180 rpm with a load of 2 N-m. Under normal operation, the THD of current is reduced from 10.43% to 1.81%. Whereas, when single phase winding fault occurs, the THD of current is reduced from 4.46 % to 2.96 %. Besides, peak to peak value of torque is dropped from 0.68 N-m to 0.66 N-m. The experimental results show the feasibility of the proposed current harmonic control strategy.

碩士
國立臺灣科技大學
電機工程系
94
This thesis focuses on the design and implementation of a speed control system for three-phase induction motors. The full-bridge diode rectifier is used to convert the utility to dc source. The control of pulse-width modulation with compensation is completed by the feedback of dc-link voltage. It thus can not only improve the current harmonics of inverter but also reduce dc-link capacitance and volume. Besides, the speed control range of three-phase induction motor driver is investigated by detecting the minimum value of dc-link voltage to avoid torque and speed fluctuation when utility voltage varies. According to the feedback of dc-link voltage, the compensation of pulse-width modulation and field-weakening control are conducted to make the motor operate steadily in constant torque and constant horse-power regions. In this thesis, closed-loop speed control of a three-phase induction motor with dc-link voltage compensation are given using constant flux and indirect rotor flux oriented controls. A high-performance, low-cost digital signal processor, TMS320LF2407A, is used as the control core. The control of motor and inverter is accomplished by software for cost reduction. A prototype of 400W three-phase induction motor with speed control system is developed. The input is three-phase, 60Hz and 110V.The dc-link capacitor is 22uF. The experimental data show that the motor runs smoothly as expected.

碩士
國立臺灣科技大學
電機工程系
105
The thesis presents circuit design for high performance permanent-magnet synchrous motor drives. It includes drive circuit, circuit protection, elements selection and circuit layout. The flyback converter with ten dc outputs is designed for the power supply of internal circuit. A voltage-source inverter is proposed as the power stage. The power integrated module from Infineon company can not only convert dc input to three-phase ac output, but also provide braking protection with its built-in IGBT when motor speed is reducing. The 32-bit digital signal processor, TMS320F28069, is adopted as the control core. A resolver is used to estimate the real-time rotor position and speed for current vector as well as speed closed-loop controls. Experimental results show that the load test with the input voltage of 310V and rated speed of 2000rpm yields the input current of 16.2A, the total output power from the inverter of 4772W and the efficiency of the three-phase power inverter of 95%. Meanwhile, the selected elements are measured to assure their temperature tolerances meet the standard requirements under full load power.

碩士
國立臺灣科技大學
電機工程系
106
This thesis presents the design of dual three-phase permanent-magnet assisted synchronus reluctance motor (PMASRM) drives. Two three-phase inverters are both controlled by one digital signal processor, TMS320F28069. Linear hall-effect and current sensors are used to feed back rotor position, speed and motor currents. The maximum torque per ampere as well as speed and current closed-loop controls are proposed to set the quadrature- and direct-axis currents to promote system performance. In addition, the post-fault control is conducted by determining and disconnecting the faulty three-phase winding via the feedback currents. The reduced-load operation of the normal three-phase winding thus enhances the system reliability accordingly. Matlab/Simulink is used to analyze the control system for dual three-phase PMASRM. The control strategy programmed by C language can reduce circuit components. The experimental results show that when the speed and the load are at 600 rpm and 6.60 N-m, respectively, the corresponding peak phase-currents of the dual three-phase windings are 9.40 A and 9.53 A, the magnetic torque is 2.76 N-m, reluctance torque is 3.89 N-m and system efficiency is 72.50%. Moreover, when the speed and the load are at 600 rpm and 3.4 N-m, respectively, the peak phase-current of the motor is 10.35 A as the faulted three-phase winding is disconnected, yielding the system efficiency of 72.66%. In short, the simulation and experimental results have verified the feasibility of the proposed system.

碩士
國立臺灣科技大學
電機工程系
106
This thesis presents the post-fault control strategy of three-phase permanent-magnet synchronous motor (PMSM) drives. A three-phase six-arm inverter, which is composed of three single-phase full-bridge inverters, is proposed to drive PMSM. The unipolar sinusoidal pulse-width modulation is used to enhance the utilization ratio of dc-link voltage. Three-phase feedback current and motor speed obtained through current and rotor position sensors are transformed to rotor frame to facilitate the quadrature-, direct-, and zero-axis current closed-loop controls for performance improvement. In addition, due to the lack of neutral point in three-phase six-arm inverters, the voltage compensation content of third-harmonic in electromotive force is added to zero-axis current control for the reduction of current harmonics and torque ripple. Moreover, when a phase winding of PMSM breaks down, the other two phase winding currents are set to have a phase angle difference of 60 electrical degrees for reduced load operation. The proposed post-fault control strategy can thus enhance the fault tolerance of the system. The digital signal processor, TMS320F28069, is adopted as system core. The control strategies are programmed by C language to reduce the circuit complexity. The Matlab/Simuink software is used to implement the performance analysis of the proposed system. Under normal operation, at 1007rpm with load torque of 1.91N-m, experimental results show that the peak phase current is 11.55A, yielding current total harmonic distortion (THD) of 6.84% with third-harmonic content of 4.92%. The electromagnetic torque ripple of 0.196N-m gives ripple torque rate of 10.3%. Furthermore, when a-phase winding breaks down, and under 1007rpm and load torque of 0.955N-m, the measured peak b- and c-phase winding currents are 15.08A and 13.56A, respectively. The corresponding THD of phase currents are 8.35% and 9.83% with third harmonic content of 7.28% and torque ripple of 0.495N-m, implying torque ripple rate of 51.8%. In short, the feasibility of the proposed control strategy is verified experimentally.

A motor drive consisting of two parallel voltage-sourced converters was developed and implemented. A parallel converter arrangement allows the system to be constructed in a modular fashion to gain economies of scale and redundancy. The converters are connected to common ac- and dc-buses without isolation and are controlled without inter-converter communication or a master/slave arrangement. The system was simulated and the results validated against an experimental setup. Both steady-state and dynamic load sharing were achieved through the use of drooped PI speed regulators. PI controllers were used to regulate the quadrature currents provided by each converter. Circulating 0-sequence current was regulated using P controllers. A linearized state-space model of the system was developed and an eigenvalue analysis was performed, showing system stability. Speed steps in simulation and in the laboratory demonstrated good response. The loss of one converter’s gating was emulated. The system continued to operate, showing an advantage of system redundancy.

碩士
國立臺灣科技大學
電機工程系
95
The objective of this thesis is to develop a DSP-based sliding-mode controller for induction motor speed control system. The mathematical model of induction motor in synchronously rotating reference frame is derived from the three-phase circuit via the coordinate transformation. According to indirect field-oriented vector control method, the thesis achieves decoupling of the motor torque and rotor flux amplitude. The variable voltage and frequency of three-phase power source based on voltage space vector pulse-width modulation drives induction motor. Due to the fact that the variations of mechanical parameter and load disturbances affect the control responses, sliding mode controller instead of conventional PI-controller enhancing the response of speed control system and adaptation of load disturbance is proposed. Finially, an experimental system is actually implemented in three-phase induction motor of 600 W using digital signal processor as the core of the speed control system. Experimental results confirm that the sliding mode control rule yield not only better response in speed but also superior robustness in external load disturbances.

碩士
國立臺灣科技大學
電機工程系
101
This thesis presents the development of three-phase permanent-magnet synchronous motor drives with linear Hall-effect sensors. Having the higher resolution, linear Hall-effect sensors can reduce the cost of the drive. After comparing digital Hall-effect sensors with linear Hall-effect sensors, the linear Hall-effect sensors are chosen to detect the required rotor position for permanent-magnet synchronous motor vector control. By adopting voltage space vector pulsed-width modulation, the utility rate of the dc-link voltage can be improved and the motor harmonics can be reduced. Meanwhile, introducing direct-axis voltage compensation in the speed closed-loop control, operating efficiency can be improved and current harmonics can be reduced without current feedback. This system uses a 16-bits digital signal processor, dsPIC30F4011, as the control core. The system is able to operate at 1000rpm with 100-watt dc generator as a load. By using digital Hall-effect sensors and six-step trapezoidal speed closed-loop control, the a-phase current harmonic is 31.83%. Whereas, in speed closed-loop control with linear Hall-effect sensors and voltage space vector pulsed-width modulation, the a-phase current harmonic distortion decreases 12.45%, and is decreased further to 9.72% through direct-axis voltage compensation mentioned above. Reduction in current harmonics of the motor has been verified experimentally.

碩士
國立臺灣科技大學
電機工程系
106
This thesis aims to design grid-connected three-phase permanent-magnet synchronous motor (PMSM) drives with bidirectional power conversion. Energy recovery feature is provided for loss reduction in generator mode without additional breaking resistor. The system includes bidirectional three-phase grid- and motor-side power converters. The former uses grid voltage vector for input current control and dc output voltage supply. Meanwhile, a dual second-order generalized integrator under synchronous frame is adopted to estimate the phase angle of grid voltage for power-factor enhancement. Whereas, the latter drives PMSM with field-oriented control using resolver and current sensors to feed back rotor position, speed as well as phase current for speed and current closed-loop controls in order to improve the performance of the proposed drive. System simulation is given by using Matlab/Simulink. A 32-bit digital signal processor, TMS320F28069, is adopted as the control core. Since control strategies are mostly implemented by software program, circuit components are reduced largely. Experimental results show that when the three-phase PMSM is operated under motor mode at 1500 rpm, the mechanical power output from the PMSM is 2.22 kW with the peak grid phase current and total harmonic distortion (THD) of 10.1 A and 3.37%, respectively, the corresponding values on the motor input are 20.3 A and 3.93%. The efficiencies of grid-side rectifier, motor-side inverter and PMSM are 98%, 98% and 85%, respectively, resulting in the overall efficiency of 82%. While in generator mode at 1500 rpm, the mechanical power input to the permanent-magnet synchronous generator (PMSG) is 2.44 kW, the peak generator phase current and its THD are 16.0 A and 3.75%, respectively. The corresponding values on the grid side are 7.2 A and 4.57%. The efficiencies of PMSG, motor-side rectifier and grid-side inverter are 82%, 98% and 97%, respectively, yielding the overall efficiency of 80%. The feasibility of the proposed system is verified experimentally.

碩士
國立臺灣科技大學
電機工程系
97
The thesis is concerned with the analysis and development of six-leg three-phase inverter for permanent-magnet synchronous motor(PMSM) drives. The power circuit uses six-leg three-phase inverter. Connecting each winding to two separately controlling legs yields three phase dc-ac converter. The inverter control strategy uses unipolar voltage switching method to raise the utilization factor of dc-link voltage. When a winding of three-phase PMSM breaks down, the associated load may have to be reduced to retain continuous running and increase the reliability of the system. In the fault tolerance control strategy, the current of PMSM is used to determine which winding is broken, so that the other two winding currents can be corrected to result in a 60-degree angle difference, thereby reducing torque pulsation. In the proposed system, six Hall-effect sensors are used to measure the position and speed of the rotor to facilitate the coordinate transformation of feedback current to achieve d-q currents and speed closed-loop control. In this thesis, Matlab/Simulink is used to simulated the proposed PMSM system including six-leg three-phase inverter with unipolar voltage switching method control strategy, d-q current closed-loop control, speed closed-loop control and fault tolerance control strategy. The digital signal processor TMS320F2808 is adopted as the control core. A prototype of 100W six-leg three-phase inverter for PMSM drives is built. The speed is 170 rpm and the load is 4 N-m. When under the normal operation of the system, the total harmonic distortion of each phase-current is 14.67 %. While for two-winding operations of three different cases, the total harmonic distortions of three phase-currents for each case measured are 17.90%, 16.48% and 17.37%, respectively. The proposed system performance is thus verified experimentally.

碩士
國立高雄應用科技大學
機械工程系
106
The purpose of this dissertation is to improve the design of non-synchronous three-phase AC induction motors to reduce the cogging torque, to avoid damage to coils and cracks in the rotor's short-circuit ring due to the damage caused by non-uniform torque acceleration bearings, resulting in the operation of the electric motor train. Loss. The asynchronous three-phase AC induction motor used in this study is a traction motor used by the Taiwan Railway Administration’s EMU500 electric car, as the electric car is an important means of transport for short-distance commutes in China. The motor has a light weight and a large output torque. The advantages of simple structure, easy maintenance, but the current motor failure is more than half of the bearing damage, has affected the effective use of vehicle scheduling and grouping. In this thesis, JMAG's electromagnetic simulation finite element analysis software is used to design and analyze the three-dimensional theoretical model of the motor. The parameters include: air gap width, silicon steel sheet material, rotor chute design, bifurcation slot winding design, etc., and the magnetic flux density of the motor can be known. , Output torque, and torque ripple, the study found that the air gap width and rotor design parameters of the two parameters can effectively the cogging torque. This study proposes that the design of non-synchronous three-phase AC induction motors used in electric vehicles should be improved in the future. If the air gap width can be changed from the existing 1.0 mm to 1.5 mm, and the rotor chute is adjusted to an angle of 3.33 and the material of the silicon steel sheet is changed to 35CS250 It can reduce the torque ripple from the current 24.48% to 17.70%, which is expected to reduce the risk of coil burnout and rotor short-circuit ring cracking caused by the bearing loss of the motor, and reduce the failure rate and maintenance of the electric vehicle. maintenance.

博士
國立臺灣科技大學
電機工程系
103
This dissertation focuses on development of low-torque ripple and high stability with a six-arm inverter for three-phase permanent-magnet synchronous motor (PMSM) drives. In this structure, the power circuit uses six-arm three-phase inverter. Each phase of the PMSM is operating independently to raise the utilization factor of dc-link voltage. By using zero-sequence current estimator, it calculates the content of third-harmonic in current. These calculated results can be used to eliminate the third-harmonic of current. When a winding of three-phase PMSM breaks down, the other two winding currents will be corrected to result in a 60-degree angle difference. The component which can suppress the third-harmonic of current was injected into healthy phases to eliminate currents harmonics, thereby reducing torque ripple. In this dissertation, Matlab/Simulink is used to simulate the proposed PMSM system. Performances with different current control and current harmonics mitigation control strategies for PMSM operated under normal and post-fault conditions are compared. This control method could be used to implementation of system. A prototype PMSM system was built with TMS302F28335 digital signal processor. And the program was completed by C language. Under the normal operation of the system, the third-harmonic of current decreases from 28.71% to 3.05%. The peak current required for system falls from 1.212 pu to approximately 1.017 pu. The current of zero-axis decreases from 0.256 pu to 0.021 pu. When the phase a open-circuit is in fault condition, the third-harmonic of current in phase b decreases from 7.00% to 1.36%. The third-harmonic of current in phase c decreases from 9.91% to 3.06%. The third-harmonic of current in zero-axis falls from 25.19 pu to 2.19 pu. The electromagnetic torque ripple decreases from 85.57% to 2.85%.The proposed system performance is thus verified experimentally.

碩士
國立臺灣科技大學
電機工程系
88
This thesis investigates the motor terminal overvoltage, ringing and common-mode voltage in pulse-width modulation (PWM) inverter-fed ac motor drive system where long leads are required. These phenomena may stress the motor winding insulation, and cause shaft voltage, bearing current, and conducted electromagnetic interference (EMI). Premature motor bearing failures and electronic equipment malfunctions have been reported to be directly related to bearing current and EMI. In this paper, parallel resistor, first-order and second-order shunt filter are designed to reduce the overvoltage and ringing at motor terminals, and methods to eliminate common-mode voltage using a three-level sinusoidal PWM inverter are presented. Simulation and experimental results are presented to verify the proposed filter design for 220-V PWM inverter-fed induction motor drive system with 10 meter lead lengths.

The use of insulated-gate bipolar transistor (IGBT)-based power converters is increasing exponentially. This is due to high performance of these devices in terms of efficiency and switching speed. However, due to the switching action, high frequency electromagnetic interference (EMI) noises are generated. Design of a power converter with reduced EMI noise level is one of the primary objectives of this research. The first part of the work focuses on designing common-mode (CM) filters, which can be integrated with differential-mode (DM) filters for three-phase pulse-width modulation (PWM) rectifier-based motor drives. This work explores the filter design based on the CM equivalent circuit of the drive system. Guidelines are provided for selection of the filter components. Different variants of the filter topology are evaluated to establish the effectiveness of the proposed topology. Analytical results based on Bode plot of the transfer functions are presented, which suggest effective EMI reduction. Experimental results based on EMI measurement on the grid side and CM current measurement on the motor side are presented. These results validate the effectiveness of the filter. In the second part of the work, it is shown that inclusion of CM filters into DM filters results in resonance oscillations in the CM circuit. An active damping strategy is proposed to damp the oscillations in both line-to-line and line-to-ground ac voltages and currents. An approach based on pole placement by state feedback is used to actively damp both the DM and CM filter oscillations. Analytical expressions for state-feedback controller gains are derived for both continuous-and discrete-time models of the filter. Trade-off in selection of the active damping gain on the lower-order grid current harmonics is analysed using a weighted admittance function method. In the third part of the work, single-phase grid-connected power converters are considered. An integrated CM filter with DM LCL filter is proposed. The work explores the suitability of PWM methods for single-phase and parallel single-phase grid-connected power converters. It is found that bipolar PWM and unipolar PWM with 180◦interleaving angle are suitable for single-phase and parallel single-phase power converters, respectively. The proposed configuration along with the PWM methods reduces the CM voltage, CM current, and EMI noise level effectively. It is also shown that the suggested circuit is insensitive to nonidealities of the power converter such as dead-time mismatch, mismatch in converter-side inductors, unequal turn on and turn off of the switches, and propagation delays. In the fourth part of the work, the inter-phase inductor in parallel interleaved power converters is integrated with LCL filter boost inductor. Different variant designs are presented and compared with the proposed structure. It is shown that the proposed structure makes use of standard core geometries and consumes lesser core material as well as copper wire. Hence, it reduces the overall size and cost of the power converter. In the present work, a 10kVA three-phase back-to-back connected with input LCL filter and output dv/dt filter, a 5kVA single-phase grid-connected power converter with LCL filter, and a 7.5kVA parallel single-phase grid-connected power converter with LCL filter are fabricated in the laboratory to evaluate and validate the proposed methods. The experimental results validate the proposed methods that result in significant EMI performance improvement of grid-connected power converters.

Dissertação de Mestrado Integrado em Engenharia Electrotécnica e de Computadores apresentada à Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Os temas nucleares desta dissertação são, de uma forma geral, a avaliação e caraterização dos espetros sonoros emitidos pelos motores de indução trifásicos, com diferentes tipos de avarias mecânicas e diferentes estratégias de controlo de acionamentos elétricos. Este documento está estruturado da seguinte forma: O capítulo 1 exibe o enquadramento do tema sobre o qual se desenvolveu esta dissertação. No capítulo 2 são apresentados os conceitos gerais relacionados com o som. Inicialmente é explorada a anatomia do ouvido humano, desde a captação até à descodificação do som em impulsos elétricos. São também definidas as principais grandezas acústicas fundamentais para a medição do ruído e por último, são fornecidos alguns conceitos gerais relacionados com as ondas de pressão sonora, desde modos de propagação até fatores que contribuem para a atenuação. O capítulo 3 explora as principais fontes de ruído sonoro do motor de indução trifásico com origem mecânica, aerodinâmica e eletromagnética. Também são explorados os diferentes tipos de acionamentos elétricos usados no decorrer desta dissertação, o controlo escalar, o controlo direto de binário e o controlo de campo orientado no rotor. No capítulo 4 é feita uma descrição das montagens experimentais, equipamentos e procedimentos utilizados na realização das medições. De seguida é efetuada a análise de alguns espetros de ruído acústico obtidos para diferentes condições de funcionamento e de regimes de carga. Semelhante análise foi possível graças à aplicação de rolamentos com avarias nos anéis interno ou externo com diferentes graus de severidade e à inserção de rotores com um número distinto de barras fraturadas. A influência de diferentes estratégias de controlo de acionamentos elétricos também é alvo de análise. Finalmente, o capítulo 5 expõe as principais conclusões retiradas do trabalho desenvolvido e propõe algumas sugestões para trabalho futuro.
The nuclear themes of the thesis are, in general, the evaluation and characterization of the sound spectrum issued by three-phase induction motors under different types of mechanical malfunctions and different control strategies used in electric drives. This document as the following structure: Chapter 1 explains the framing of the theme of this thesis. In chapter 2 are presented some general concepts related to sound. Initially it is explored the anatomy of the human ear, from the capturing of sound to its decoding into electrical impulses. The main acoustical magnitudes, essential to measure the noise, are also defined. In the end of the chapter are presented some aspects related to sound pressure waves, from forms of propagation to attenuation factors. Chapter 3 explores the main sources of noise in a three-phase induction motor with mechanical, aerodynamic or electromagnetic origin. A explanation of the control strategies used in this dissertation, scale control, direct torque control and rotor field oriented control is presented. In chapter 4 are described the experimental setups, equipment characteristics and procedures used when carrying out the measurements. Then, it is carried out an analysis of some acoustic noise spectra obtained from different working and loading conditions. To evaluate the impact of faults in the motor, were applied bearings with different fault degrees in the external and internal rings as well as rotors with one or two broken bars. The influence of different control strategies used in electric drives is also addressed. Chapter 5 presents the main conclusions of the work developed and some suggestions for future work.