Direct Voltage Control of an Interior Permanent Magnet Synchronous Motor in Overspeed Conditions

Electric machines contribute to efficiency, convenience, and sustainability in various applications across our modern lives, such as electric public transportation, renewable energy, industrial applications, home appliances, and many more. Specifically, permanent magnet synchronous machines (PMSMs) have high power density, high efficiency, high torque, and a fast-dynamic response. These features make this kind of machine very attractive for electric propulsion like automotive electrical power steering applications, which play a significant role in being a perfect alternative to internal combustion engines (ICEs) because of the environmental implications and the scarcity of fuel resources for these engines. These machines must fulfill specific characteristics to achieve high performance for such applications. Because of their numerous benefits, including robustness, potential operation, reduced control complexity, and high-power density in the high-speed range, most manufacturers prefer to employ permanent magnet synchronous machines (PMSMs) in multi heavy duty and smart applications. On the other hand, these aforementioned synchronous machines experience nonlinearity due to magnetic saturation phenomena because of their mechanical structure and volume optimization needs. Additionally, aging operation temperatures and fabrication tolerances cause deviations and mismatches in some electric parameters when they reach their voltage thresholds. Therefore, precise controllers need to be developed and optimized to achieve the most effective and reliable torque control behavior without affecting these parameters of the electric machine even while operating at its maximum capacity. In this case study, the back electromotive force, which proportionally increases as the machine rotation speed increases, should be considered during the high-speed range, and, due to the voltage limit of the power source and inverter, flux weakening control must be carried out to prevent any excess electromagnetic flux. This thesis presents a comparative study of the main benefits and drawbacks of various electric machines used in industrial applications. In the beginning, PMSMs are discussed because they satisfy particular requirements for various applications, such as electric vehicle (EV) propulsion systems, making them more desirable in such similar fields as one of many critical applications in which these machines could be used. The most popular control strategies and techniques of the interior permanent magnet synchronous machines (IPMSMs) are then thoroughly reviewed and analyzed. The primary objective of this thesis's research is to validate how to employ the developed direct voltage control (DVC) method to maintain maximum torque while keeping high performance, particularly beyond the base speed and towards higher speed ranges in the IPMSM machine, by implementing the formulas found in the literature. An analysis of the proposed control method is performed compared to the widely used field-oriented vector control strategy to demonstrate its simplicity and capability. The flux weakening and the maximum torque per volt (MTPV) working regions of IPMSM should be maintained at high speeds to maximize torque while efficiently minimizing the stator flux, so by applying the literature's MTPA, FW, and MTPV regions formulas to the suggested DVC through implementing a developed MATLAB coding and Simulink model scheme, then evaluating the outputs and comparing them with the results we got from the popular FOC method using the same equations. The final experimental results, with an additional quantitative efficacy comparison for both control methods, reveal the proposed method's ability. Simulations are implemented using experimental data from an IPMSM machine with five-horse nominal power.