Graduation Year

2023

Document Type

Dissertation

Degree

Ph.D.

Degree Name

Doctor of Philosophy (Ph.D.)

Degree Granting Department

Electrical Engineering

Major Professor

Wilfrido A. Moreno, Ph.D.

Committee Member

Ismail Uysal, Ph.D.

Committee Member

Chung Seop Jeong, Ph.D.

Committee Member

Andres Tejada, Ph.D.

Committee Member

Roshani O'Bryan, Ph.D.

Keywords

Surface Permanent Motor, Field Programmable Gate Array, Hardware in the Loop

Abstract

This dissertation examines a novel sensor-less Direct Torque Control (DTC) strategy for Electrical Submersible Pump (ESP) systems using Surface Mounted Permanent Magnet Synchronous Motors (SPMSM) that are used for oil and gas production. As oil and gas are the two largest fuels in use today to generate energy, the technologies to improve efficiency, increase reliability and reduce carbon footprint are essential. SPMSM is one of the main motor topologies in use to improve the reliability and efficiency of ESP systems. Due to the absence of damper winding, SPMSM cannot be started using Direct On-Line (DOL) control. Instead, Variable Speed Drives (VSD) are typically used, which require power electronics convention from the power supply. Measuring or estimating the rotor position and speed for feedback to the control system is highly important. This requires a mechanical position or speed sensor. For ESP applications where the motor is located in the well thousands of feet below the surface, the physical sensor approach presents many more concerns such as reduced reliability, susceptibility to noise, and temperature sensitivity just, to name a few. It also increases the complexity, and cost of the ESP system. To avoid the disadvantage of mechanical sensors, great efforts have been made on the development of sensor-less control schemes such as Volt per Hertz(V/Hz), Field Oriented Control (FOC), and Direct Torque Control (DTC). DTC of a Permanent Magnet Synchronous Machine (PMSM) is known to give fast and good dynamic torque response. One major problem associated with DTC drive is that the switching frequency varies with the operating condition. In ESP applications with step-up transformers variable frequency is a big challenge. To solve this challenge, DTC schemes based on Space Vector Modulation (SVM) with fixed switching frequency have been proposed. The objective of this dissertation is to investigate novel control strategies for the design, modeling, analysis, and implementation of sensor-less DTC- SVM SPMSM control for ESP systems. The DTC- SVM proposed strategy is focused on the design of the optimal stator voltage vector based on the error signal between the estimated electromagnetic torque and the estimated stator flux linkage values. The controller compares the estimated electromagnetic torque and stator flux linkage with their respective reference values. The comparators are used to determine demand torque, flux magnitude, and flux vector. DTC uses no current controller or motor parameters other than the stator resistance and inductance, which yields a faster torque response and lower parameter dependence. A mathematical model of DTC- SVM SPMSM control demonstrated quick and robust torque reaction and high-efficiency performance will be developed, analyzed, and verified using a Field Programmable Gate Array (FPGA) based Hardware in the Loop (HIL) concept. The machine model considers operating conditions below and above synchronous speed. The DTC- SVM technique uses electromagnetic torque and flux as the controlled variable, where the feedback signals are obtained through flux and torque estimators. The simulation results of the DTC- SVM SPMSM-drive system will be presented. SPMSM control model will be connected to the ESP system with a sine-wave filter, step-up transformer, and long cables. It will then be modeled and examined under different load conditions during steady-state and transient operations. Furthermore, motor performance and characteristics will be evaluated at different loads and speed conditions. A Design of Experiments (DOE) will be conducted to confirm the designed control approaches, the robustness and effectiveness of the method, and the performance of the drive system. Finally, a trade-off analysis for System Power Quality will be performed, and the results presented.

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