Performance Analysis of P, PI, and PID Controllers for Speed Regulation in VSI-Fed Induction Motor Drives:




Abstract:

This study presents a comparative analysis of Proportional (P), Proportional Integral (PI), and Proportional Integral Derivative (PID) controllers for speed regulation in Variable Speed Drive (VSI)-fed induction motors. Induction motors play a crucial role in industrial systems, and the demand for efficient speed control has led to the exploration of various control strategies. In particular, VSI-fed induction motor drives are widely used in industrial applications that necessitate superior transient performance.

Introduction:

The widespread use of electrical motors in industrial systems emphasizes the importance of speed control in induction motors (IMs). Variable Speed Drives (VSDs) employing Voltage Source Inverters (VSIs) offer flexibility and efficiency in controlling IM speed. This paper explores the performance of P, PI, and PID controllers in VSI-fed IM drives.


Fig.1 shows the block diagram of a VSI-fed induction motor drive using P, PI, and PID controller.


Fundamentals of Conventional Controllers:

  1. Proportional (P) Controller:

    • P controller systems are characterized by linear feedback control.
    • Suitable for stabilizing 1st order unstable processes.


    • Fig.2. Block diagram of P controller

    • The controller output is proportional to the error signal, optimizing reference following and system dynamics.

  2. Proportional Integral (PI) Controller:

    • PI controllers are widely adopted in industrial applications for their simplicity and cost-effectiveness.
    • Effective in eliminating steady-state error and forced oscillations.

Fig.3. Block diagram of PI controller.
    • However, the introduction of an integral mode may impact response speed.

  1. Proportional Integral Derivative (PID) Controller:

    • PID controllers combine proportional, integral, and derivative control actions.
    • They are most commonly used in industry due to their versatility.
    • PID controllers enhance stability, reduce overshoot, and improve transient response.

    • Fig.4. Block diagram of PID controller.

Performance Comparison:

Tables 1 and 2 outline the effects of changing controller parameters and coefficients on speed of response, stability, and accuracy. The results indicate that PID controllers offer improved performance compared to P and PI controllers, with minor changes or no impact on various parameters.


Conclusion and Future Scope:

In conclusion, the comparative study reveals that PID controllers exhibit superior response characteristics in VSI-fed IM drives. While P controllers are suitable for stabilizing 1st-order processes, PI controllers address disturbances and noise, and PID controllers excel in handling higher-order processes. Future work could involve evaluating the output response of VSI-fed IM drives in diverse industrial applications and guiding the selection of appropriate controllers based on specific motor requirements.