Vector Control of Drives
This lab provides hands-on experience in the modeling, control, and real-time implementation of AC motor drive systems. Students will identify machine parameters, build abc→dq models, design and tune V/f, vector (FOC), and DTC controllers, implement SVPWM on a three-phase inverter, and validate performance on hardware using safe measurement practices.
Objectives
- Model induction machines in both abc and dq reference frames and explain the benefits of dq alignment for control design and real-time implementation.
- Identify key electrical and mechanical parameters of an induction motor from laboratory tests and validate the model against measured steady-state and transient behavior.
- Design, implement, and tune a closed-loop V/f speed controller that maintains rated air-gap flux while meeting basic regulation and transient response targets.
- Develop field-oriented (vector) control for an induction motor with decoupled torque and flux channels; design current and speed PI loops with proper bandwidth hierarchy.
- Implement direct torque control (DTC) for an induction motor using an estimator and switching table, and compare its dynamic response and torque ripple to vector control.
- Derive and implement space-vector PWM (SVPWM) for a three-phase inverter; verify linear modulation range, switching sequence, and DC-bus utilization in simulation and hardware.
- Extend vector control concepts to a surface-mounted PMSM: build the dq model, design current and speed PI controllers, and verify performance in real time.
Photos
Equipment
Three‑inverter and motor drive (CUSP Electric Drives Kit)
Sciamble Corp.
Isolated DC power supply
B&K Precision Corporation
Digital multimeter
B&K Precision Corporation
Digital storage oscilloscope (optional)
Tektronix
Experiments
Description: In this experiment, a pre-built induction motor speed control model will be simulated and run in real-time, as an introduction to the electric drives laboratory kit.
Description: A 3Φ AC Induction motor can be mathematically modeled as an electrical and a mechanical system related by back-emf to speed and current-torque relationships. In this experiment, the electrical and mechanical parameters of the Induction motor are determined. These values are necessary to design proper control system to control motor speed, torque, or position.
Description: In an induction motor, for fast dynamic electromagnetic torque response, it is preferable to maintain the air-gap flux at rated value. This is achieved in V/f control, where the ratio of applied terminal voltage to that of its frequency is held a constant equal to the value at rated condition. The speed of the motor is controlled by adjusting the applied frequency while maintaining V/f constant. This experiment deals with how to design a closed loop V/f speed controller for an induction motor.
Description: In this experiment, a mathematical model of an induction motor will be simulated based on the parameters estimated in the previous experiment. For this, unlike the previous experiment where the model was in abc domain, the motor will be modeled in dq frame. With proper alignment of the dq frame, the motor model becomes simpler compared to motor modelled in abc frame. The major advantage of this approach, other than the reduction in simulation run-time, is the ease of PI controller design to control motor speed, current or position. In addition to simulation, the controller designed will also be evaluated on an actual induction motor in real-time.
Description: In this experiment, a sensorless speed control of an induction motor using direct torque control (DTC) will be simulated. The dq motor model developed in the previous experiment will be used for this as well. The estimator model and the switching algorithm will be modified to implement DTC. In addition to simulation, the controller will be evaluated on an actual induction motor in real-time.
Description: In previous experiments, the induction motor dq model and its controller was developed and tested in simulation and real-time. The power processing unit was considered a black-box that generated desired voltage at the inverter output given a reference voltage. In this experiment, the functioning of the power processing unit and the modulation algorithm used is explored in detail. Next section deals with the theoretical background for this experiment followed by simulation of switched-mode DC-AC converter. Finally, the simulation model is verified in real-time.
Description: In this experiment, a dq model of a surface permanent magnet AC (PMAC) motor will be simulated. The speed of the PMAC motor will be controlled using a closed loop PI controller which will be designed in this experiment. In addition to simulation, the controller designed will also be evaluated on an actual PMAC motor in real-time.
Resources
Safety considerations when working in power electronics
Open resource →Textbook
Analysis and Control of Electric Drives: Simulations and Laboratory Implementation
Ned Mohan, Siddharth Raju · Wiley