Vector Control of Electric Drives
This course introduces modeling, analysis, and control of AC and special electrical machines. Topics span induction machines, vector control, DTC, PWM inverters, and sensorless operation. Advanced drives include DFIGs, PMSMs, and switched-reluctance motor systems.
Objectives
- Understand the applications for accurate torque, speed and position control
- Understand the requirement on electromagnetic torque produced by ac machines
- Understand Induction Machines in Phase Quantities
- Understand Dynamic Analysis and Modeling of Induction Machines using d-q Axes Theory
- Understand Qualitatively the Vector Control and modeling of Induction Motor Drives
- Understand the Mathematical Description Vector Control and modeling of Induction Motor Drives
- Understand the Effects of Errors in Motor Parameter Estimation
- Understand Doubly-Fed Induction Generators and how to control them
- Understand Voltage Vector Pulse-Width Modulation
- Understand Direct-Torque Control and Sensor-less Drives
- Understand Permanent-Magnet and Synchronous Drives
- Understand Switched-Reluctance Drives
Textbooks
Analysis and Control of Electric Drives
Ned Mohan, Sidharth Raju · Wiley
Modules
Description: Introduction to the course on Advanced Electric Drives, comparing the control requirements of AC machines versus DC machines. It outlines the necessity of vector control for achieving precise torque, speed, and position control in high-performance applications like robotics and electric vehicles.
Description: Reviews the physical structure of the induction machine and establishes the basic voltage and flux linkage equations in natural phase quantities (a, b, c). It discusses the mathematical complexity arising from time-varying inductances dependent on rotor position.
Description: Continues the dynamic analysis by deriving the expression for electromagnetic torque using phase variables. It highlights the difficulty of controlling torque directly using these raw phase quantities due to the complex coupling between stator and rotor.
Description: Introduces the stationary and rotating reference frames (Park’s Transformation). It demonstrates how to transform the complex, time-varying phase equations into constant coefficients in the d-q axis to simplify control system design.
Description: Completes the dynamic model by presenting the equivalent circuits for the d and q axes. It explains the cross-coupling between the axes and how flux linkages relate to currents in this new reference frame, creating a DC-motor-like structure.
Description: Provides a conceptual overview of Field Oriented Control (FOC) without heavy mathematics. It uses the analogy of a DC motor to explain how vector control allows for the independent control of flux-producing and torque-producing currents.
Description: Derives the specific control equations needed to implement Field Oriented Control. It focuses on the condition of aligning the rotor flux vector with the d-axis to achieve the necessary decoupling for high-performance control.
Description: Details the block diagram of the vector control system, including coordinate transformations and PI controllers. It explains how to generate the reference voltages for the inverter and close the feedback loops.
Description: Analyzes the impact of parameter mismatch, specifically when the controller's internal model of the rotor time constant differs from the real motor. It discusses how these errors affect torque linearity and efficiency.
Description: Focuses on the application of vector control in wind energy systems using DFIGs. It explains the control of rotor currents to manage active and reactive power independently connected to the grid.
Description: Explains the switching strategy for the voltage source inverter using Space Vector PWM. It shows how to synthesize the reference voltage vector using the available inverter switching states to minimize harmonic distortion and utilize the DC bus effectively.
Description: Introduces Direct Torque Control, an alternative to FOC that avoids coordinate transformations and PWM. It explains the use of hysteresis comparators and look-up tables to directly select inverter states for fast torque response.
Description: Adapts vector control theory for PMSM drives, discussing the differences in d-axis and q-axis inductances. It covers Maximum Torque Per Ampere (MTPA) strategies and the specific requirements for controlling permanent magnet machines.
Description: Covers the operation and control of Switched Reluctance Motors, which rely on reluctance torque without permanent magnets. It outlines the specific current control and firing angle strategies required for these rugged machines.