Implementation of a Digital Signal Processor (DSP) Based Space Vector Control of AC Induction Motor Drives

The inverters transfer energy from a DC source to a controlled process in the form of pulse trains, using semiconductor switches which are turned on and off at fast repetition rates. This thesis explains in depth how these pulse trains synthesize sine waves. AC waveform generation techniques such as the square wave and Pulse Width Modulation (PWM) are compared in terms of their harmonic elimination capability and fundamental gain control. Various PWM techniques such as bipolar switching, unipolar switching, selective harmonic elimination switching and Space Vector PWM (SVPWM) switching are analyzed and compared in terms of their ability to control harmonic distortion (THD), minimize switching losses, control fundamental gain and maximize DC bus utilization capacity. The selective harmonic elimination technique is covered in depth including a technique that utilizes a neural network controller to remove a selected set of harmonics. This thesis focuses on Space Vector PWM (SVPWM) technique since it has many advantages over other conventional methods such as sine wave PWM. Thus, the SVPWM theory and experimental analysis is presented in depth. The SVPWM technique was realized using the state-of-the- art power electronics hardware and Digital Signal Processing (DSP) software. The experimental procedure and harmonics analysis of the DSP based SVPWM output waveforms and inverter output voltages and currents are presented. The experiments were carried out using power electronics development modules such as the Texas Instrument’s TMS320LF2407 DSK (eZdsp), Digital Motor Controller (DMC1500), and the VisSim™/TI C2000 Rapid Prototyper software package and a three-phase AC induction motor. The VisSim™/TI C2000 Rapid Prototyper was extensively used to model an AC induction motor control sub system that generates real time SVPWM waveforms to control a three-phase induction motor. The AC induction motor control sub-system was implemented using the principle of constant Volts/Hertz (V/Hz) profile. S\u27 averal measurements and observations of the phase-voltages, line-voltages and phase currents were made to observe the quality of the power produced using the SVPWM technique. The SVPWM waveforms were simulated using MATi_AB™ software and the VisSim™/TI C2000 Rapid Protctyper software. These simulated SVPWM waveforms were compared with the DSP generated SVPWM waveforms and the inverter output. The completed project will give the user the ability to use the VisSim™/TI C2000 Rapid Prototyper software to generate SVPWM waveform and power the DSP controller (eZdsp), interface the DMC1500 (inverter) with the eZdsp and control a three-phase induction motor. An extension of the conventional three-phase SVPWM to higher order phase systems is reviewed. An overview of the principle of sensorless variable speed three-phase AC motor drives with closed-loop speed control is included

Comparative Study of Power Semiconductor Devices in a Multilevel Cascaded H-Bridge Inverter

This thesis compares the performance of a nine-level transformerless cascaded H-bridge (CHB) inverter with integrated battery energy storage system (BESS) using SiC power MOSFETs and Si IGBTs. Two crucial performance drivers for inverter applications are power loss and efficiency. Both of these are investigated in this thesis. Power devices with similar voltage and current ratings are used in the same inverter topology, and the performance of each device is analyzed with respect to switching frequency and operating temperature. The loss measurements and characteristics within the inverter are discussed. The Saber® simulation software was used for the comparisons. The power MOSFET and IGBT modeling tools in Saber® were extensively utilized to create the models of the power devices used in the simulations. The inverter system is also analyzed using Saber-Simulink cosimulation method to feed control signals from Simulink into Saber. The results in this investigation show better performances using a SiC MOSFET-based grid-connected BESS inverter with a better return of investment

Electric Drives with Wide Bandgap Devices for Two-Phase Very Low Inductance Machines

Slotless and coreless machines with low inductance and low core losses are attractive for high speed and high power density applications. With the increase in fundamental frequency, typical drive implementations using conventional silicon-based devices are performance limited and also produce large current and torque ripples. This paper presents a systematic study of proposed drive configurations implemented with wide bandgap (WBG) devices in order to mitigate such issues for 2-phase very low inductance machines. Two inverter topologies, i.e., a dual H-bridge inverter with maximum redundancy and survivability and a 3-leg inverter for reduced cost, are considered. Feasible modulation schemes are derived based on theoretical analysis and the associated maximum output voltages are identified. Simulation and experimental results are provided to validate the feasibility of drive systems and the effectiveness of analysis

Investigation of a GaN-Based Power Supply Topology Utilizing Solid State Transformer for Low Power Applications

Gallium nitride (GaN) power devices exhibit a much lower gate capacitance for a similar on-resistance than its silicon counterparts, making it highly desirable for high-frequency operation in switching converters, which leads to their significant benefits on power density, cost, and system volume. High-density switching converters are being realized with GaN power devices due to their high switching speeds that reduce the size of energy-storage circuit components. The purpose of this dissertation research is to investigate a new isolated GaN AC/DC switching converter based on solid-state transformer configuration with a totem-pole power factor corrector (PFC) front-end, a half-bridge series-resonant converter (SRC) for power conversion, and a current-doubler rectifier (CDR) at its output. A new equivalent circuit model for the converter is constructed consisting of a loss-free resistor model for the PFC rectifier with first harmonic approximation model for the SRC and the CDR. Then, state-space analysis is performed to derive the converter transfer function in order to design the controllers to yield sufficient phase margins. The converter offers the advantages of voltage regulation feature of the solid-state transformer, low harmonics and close-to-unity power factor of the PFC rectifier, soft-switching of the half-bridge SRC, reduced size of the high-frequency transformer, and smaller leakage inductance of the CDR which is used for low-voltage high-current applications as the CDR draws half of the load current in the transformer secondary side yielding less copper losses. A high-frequency nanocrystalline toroid transformer, based on a modified equation to determine its leakage inductance, is designed and fabricated to satisfy the performance specifications of the converter. A meticulously planned gate driving strategy together with a Kelvin-source return circuitry is used to mitigate Miller effects, minimize gate ringing, and minimize the parasitics of the pull-down and pull-up loops of the converter. A new programming method that combines MATLAB Simulink embedded coder with code composer studio for the TMS320F28335 digital signal processor (DSP) controller is developed and demonstrated. Finally, the GaN-based AC/DC converter is experimentally verified for a 120Vac to 48Vdc/60Vdc conversion operating at 100 kHz for various loadings