Design Of A Microcontroller-Based Converter For 3-Phase Brushless DC Motor Drives

Dalam aplikasi industri dan peralatan perubatan, dapat dilihat kepentingan pengawalan peralatan atau mesin dengan memantau proses keluaran dan kawalan masukan daripada komputer. In industrial application and medical devices, it can be seen that there is a need of controlling the devices or machines with observation of the output process and input control from a computer

Zigbee based wireless adjustable speed drive system

Indiana University-Purdue University Indianapolis (IUPUI)This thesis proposes a remotely controlled motor drive system which is able to supply a regulated voltage for both DC and AC motors. The proposed system integrates two different technologies, each of which belongs to the field of wireless communications and semiconductor power electronics. The introduction highlights the literature review and technical contributions in these two electrical engineering fields. The pulse width modulated control algorithm for speed control is discussed in detail. Incorporating the zigbee wireless technology into the motor drive system, for the speed control of an AC and a DC motor, by implementing digital pulse width modulation technique is the aim of this thesis. The main characteristics of the proposed system are: 1) its universal feature since it can feed either DC or AC motor without changing the hardware, 2) remotely controlled, which allows the end-user to control the motor speed safely from a remote distance, 3) flexibility in installation of the motor drives in areas that are not easily accessible by end-users, and 4) uninterrupted speed control for distance of up to few 100 feet

Minimisation of output DC current component in grid-connected inverters for solar power applications

PhD ThesisIn grid-connected photovoltaic applications, a supply-frequency output transformer is normally used to isolate the inverter from the supply. This transformer is heavy, costly and adds to the overall power loss. However removal of the output transformer can result in unwanted DC components appearing in the inverter output current. Excessive DC current injection into the distribution network can affect distribution components as well as other loads connected to the network. There are various circuits which can be used to for grid connection without the use of an output transformer. These include the 2-level half-bridge and the H-bridge inverters. These circuits have the disadvantage of the requirement for higher rated power devices or increased EMI problems due to high frequency switching of the DC-link relative to earth. To overcome these problems, a three-level half-bridge inverter circuit is used, where the DC-link voltage can be twice the device voltage rating allowing the use low rated switching devices. The neutral conductor is connected to the mid-point of a split rail supply from PV array, and therefore the DC-link voltage is not switching relative to earth. The aim of this research is to minimise the DC current component in the output of a grid-connected inverter when a supply-frequency output transformer is not used. A three-level diode-clamped half-bridge inverter is proposed to interface the PV panel directly to the utility grid. The main contribution of this research lies in the development of an auto-calibration technique for the DC-link current sensors in the multi-level inverter. Combined with a current feedback control scheme this technique allows the minimisation of DC current offset drift in the Hall-Effect current sensors. Auto-calibrated DC-link current sensors in turn allow the inverter output current controller to minimise the output DC current component in spite of sensor drift and other disturbances. A comprehensive review on the different types of grid-connected PV systems, the problems caused by DC current injection into the grid, and up-to-date techniques to overcome this problem is included. The performance of the auto-calibration technique is investigated using both computer simulation and an experimental test rig

Contributions on spectral control for the asymmetrical full bridge multilevel inverter

Las topologías de circuitos inversores multinivel pueden trabajar a tensiones y potencias mayores que las alcanzadas por convertidores convencionales de dos niveles. Además, la conversión multinivel reduce la distorsión armónica de las variables de salida y en algunos casos, a pesar del aumento de elementos de conmutación, también reduce las pérdidas de conversión al incrementarse el número de niveles. La reducción de distorsión alcanzada por el número de niveles puede aprovecharse para reducir las pérdidas de conmutación disminuyendo la frecuencia de las señales portadoras. Para reducir aún más esta frecuencia sin degradar el espectro, nosotros controlamos las pendientes de las portadoras triangulares. Primero se han desarrollado dos modelos analíticos para predecir el espectro del voltage de salida, dependiendo de: el índice de modulación MA, la razón de distribución de voltaje K de las fuentes de alimentación , y las cuatro pendientes de las portadoras{r1, r2, r3, r4}. El primer modelo considera el Muestreo Natural y se basa en Series Dobles de Fourier (SDF) mientras que el segundo modelo, utiliza la Serie Sencilla de Fourier (SSF) introduciendo el concepto de Muestreo Pseudo-Natural, una aproximación digital de la modulación natural. Ambos modelos son programados en Matlab, verificados con Pspice y validados con un prototipo experimental que contiene un modulador digital implementado con DSP.La concordancia entre las modulaciones natural y pseudo-natural, asi como entre sus respectivos modelos, es aprovechada por un algorítmo genético (AG) donde la THD es la función costo a reducir. Después de varios ensayos y de sintonizar el AG, se genera una matriz que contiene conjuntos de portadoras optimizadas dentro un rango específico de las variables {MA,K} y es probada con un segundo prototipo en lazo cerrado. Un lazo lento digital modifica las portadoras creadas por un dsPIC en modulaciones PWM; estas son demoduladas y sus amplitudes corregidas por un lazo de acción anticipada. Estas portadoras se comparan con una referencia sinusoidal que a su vez es modificada por variables de estado, generando finalmente la modulación multinivel en lazo cerrado. Los resultados finales demuestran la fiabilidad de la reducción de armónicos usando la programación de las pendientes de las portadoras. Palabras claves: inversor multinivel, PWM, distorsión armónica, modelo espectral, pendiente de portadora, conjunto de portadoras, distribución de niveles, Serie Doble de Fourier, Serie Simple de Fourier, muestreo natural, muestreo regular, muestreo pseudo-natural , Algoritmos Genéticos.Multilevel inverter (MI) topologies can work at higher voltage and higher power than conventional two-level converters. In addition, multilevel conversion reduces the output variables harmonic distortion and, sometimes, in spite of the devices-count increment, the conversion losses can also decrease by increasing the number of levels. The harmonic distortion reduction achieved by increasing the number of levels, can be used to further reducing the switching losses by decreasing the inverter carrier frequencies. To reduce even more the switching frequency without degrading output spectrum, we control the triangular carrier waveforms slopes. First, to achieve this target, two analytical models have been created in order to predict the inverter output voltage spectrum, depending on diverse parameters: the amplitude modulation index MA, the voltage distribution K of the inverter input sources, and the four carrier slopes {r1, r2, r3, r4}. The first model considers Natural Sampling and is based on Double Fourier Series (DFS) whereas the second model based on Simple Fourier Series (SFS), introduces the concept of Pseudo-Natural Sampling, as a digital approximation of the natural modulation. Both models are programmed in Matlab, verified with Pspice simulations and validated with a first experimental prototype with a DSP digital modulator.The good agreement between natural and pseudo-natural modulations, as well as their respective DFS and SFS models, is exploited by a Genetic Algorithm (GA) application where THD is the cost function to minimize. After testing and properly tuning the GA, a framework matrix containing the optimized carriers set for a specific range of variables {MA,K} is generated and then, tested with a second, closed-loop prototype. A slow digital loop modifies the carrier slopes created by dsPIC microcontroller as PWM modulations, whose amplitude, once demodulated, are affected by a feed-forward loop. These carriers, compared with a sinusoidal reference, state-feedback modified, generate finally the closed-loop multilevel modulation. The final results demonstrates the feasibility of harmonic reduction by means of carrier slopes programming. Keywords: multilevel inverter, PWM, harmonic distortion, spectral modeling, carrier slope, carriers set, level distribution, Double Fourier Series, Simple Fourier Series, natural sampling, regular sampling, pseudo-natural sampling, Genetic Algorithms

An efficient hybrid photovoltaic battery power system based grid-connected applications

Power management systems for grid-tied photovoltaic-battery power systems are the focus of this research. Solar photovoltaic (PV) panels, lithium-ion batteries, and a voltage source inverter (VSC) are all part of the system. By employing the fuzzy logic (FL) technique, a PV system's power output can be maximized in a variety of weather circumstances. In addition, the state-of-charge-based power management system (PMS) was investigated to manage power sharing between sources and the grid and then manages the battery module's charge/discharge process. Active-reactive (PQ) control was used on the VSC converter while it was synced with the grid and regulated. In order to model and simulate the suggested system under various solar irradiances, Matlab/Simulink was employed. In contrast to the standard grid-connected inverter, which operates without batteries, the simulation results showed that adding the battery energy storage system BESS increased the system's performance. A grid-connected inverter that makes use of BESS can prevent the absence of PV energy or shading of the arrays. To explain why PMS is so effective, the simulations show that the injected grid current is more stable and has less total harmonic distortion (THD)

Advanced Control Techniques for Efficiency and Power Density Improvement of a Three-Phase Microinverter

Inverters are widely used in photovoltaic (PV) based power generation systems. Most of these systems have been based on medium to high power string inverters. Microinverters are gaining popularity over their string inverter counterparts in PV based power generation systems due to maximized energy harvesting, high system reliability, modularity, and simple installation. They can be deployed on commercial buildings, residential rooftops, electric poles, etc and have a huge potential market. Emerging trend in power electronics is to increase power density and efficiency while reducing cost. A powerful tool to achieve these objectives is the development of an advanced control system for power electronics. In low power applications such as solar microinverters, increasing the switching frequency can reduce the size of passive components resulting in higher power density. However, switching losses and electromagnetic interference (EMI) may increase as a consequence of higher switching frequency. Soft switching techniques have been proposed to overcome these issues. This dissertation presents several innovative control techniques which are used to increase efficiency and power density while reducing cost. Dynamic dead time optimization and dual zone modulation techniques have been proposed in this dissertation to significantly improve the microinverter efficiency. In dynamic dead time optimization technique, pulse width modulation (PWM) dead times are dynamically adjusted as a function of load current to minimize MOSFET body diode conduction time which reduces power dissipation. This control method also improves total harmonic distortion (THD) of the inverter output current. To further improve the microinverter efficiency, a dual-zone modulation has been proposed which introduces one more soft-switching transition and lower inductor peak current compared to the other boundary conduction mode (BCM) modulation methods. In addition, an advanced DC link voltage control has been proposed to increase the microinverter power density. This concept minimizes the storage capacitance by allowing greater voltage ripple on the DC link. Therefore, the microinverter reliability can be significantly increased by replacing electrolytic capacitors with film capacitors. These control techniques can be readily implemented on any inverter, motor controller, or switching power amplifier. Since there is no circuit modification involved in implementation of these control techniques and can be easily added to existing controller firmware, it will be very attractive to any potential licensees

High power density AC to DC conversion with reduced input current harmonics

PhD ThesisThis thesis investigates the bene ts and challenges arising from the use of minimal capacitance in AC to DC converters. The purpose of the research is to ultimately improve the power density and power factor of electrical systems connected to the grid. This is carried out in the con- text of a low cost brushless DC drive system operating from an o ine power supply. The work begins with a review of existing applications where it is prac- tical to use a limited amount of DC link capacitance. The vast majority of these have a load which is insensitive to supply power variations at twice the line frequency. Low performance motor drives are found to be the most prevalent, with the inertia of the rotor mitigating the e ect of torque ripple. Further research is carried out on active power factor cor- rection techniques suitable for this application, leading to the conclusion that no appropriate systems exist. A power supply is developed to enable a 24V, 200W brushless motor drive to operate from the mains. The system runs successfully using only 1µF of DC link capacitance, which causes the motor supply volt- age to have 100% ripple. It is noted that whilst this drastically reduces the low frequency input current harmonics, those occurring at the load switching frequency are greatly increased. To combat this, a novel active power factor correction system is proposed using a notch lter to detect the input current error. The common problem of voltage feedback ripple is avoided by eliminating the voltage control loop altogether. The main limitations are identi ed as a high sensitivity to load step changes and variations in line frequency. Despite this, a high power factor is maintained in all operating conditions, as well as compliance with the relevant harmonic standards.Dyson Technology Ltd and Newcastle Univer- sit

Improving fault tolerant drives for aerospace applications

D EngThe aerospace industry is moving towards the more electric aeroplane where traditional hydraulic systems are being replaced with electrical systems. Electrical technology offers some strong advantages compared to hydraulic technology including; cost, efficiency, power on demand and relative ease of maintenance. As with most new technologies, a major disadvantage is its limited reliability history. A lot of research in the aerospace field therefore focuses on improving fault tolerant electrical systems. Work done in this thesis builds on an existing fault tolerant drive, developed by Newcastle University and Goodrich Actuation Systems as part of the ELGEAR (Electrical Landing Gear) project. The purpose of this work is to continue improving the drive’s fault tolerant features; especially in areas where the drive is most vulnerable. The first part of this thesis focuses on improving the overall system reliability by monitoring the health of the dc-link capacitors in the fault tolerant drive. The implemented estimation technique makes use of voltage and current sensors which are already in place for protection and control purposes. The novel aspect of the proposed technique relates to monitoring capacitors in real time whilst the motor is operational. No external interferences, such as injected signals or special operation of the drive, are required. The condition monitoring system is independent of torque and speed, and hence independent of a variation in load. The work was validated using analytical methods, simulation, low voltage experimentation and high voltage implementation on the ELGEAR drive. The second part of this thesis focuses on single shorted turn faults, in fault tolerant permanent magnet (PM) motors. Despite the motor being able to withstand a wide range of faults, the single shorted turn fault remains a difficult fault to detect and handle. The problem arises from the magnets on the spinning rotor that cannot be ‘turned off’ at will. This thesis investigates the severity of the faulted current in a shorted turn and how it varies depending on the turn’s location in the stator slot. The severity of the fault is studied using 2D finite element analysis and practical implementation on the ELGEAR rig. Finally, recommendations are proposed for improving the ELGEAR motor for future fault tolerant designs.EPRSC and Goodrich Aerospace (now United Technologies