Abstract

In this paper, a model-based tuning method for a PID controller of excitation systems based on a simplified model that considers measurement delay is proposed. The conventional model-based tuning method, which has been studied previously, uses a simplified excitation system model that ignores all the delay components. However, since the rms voltage measurement can take hundreds of milliseconds to calculate depending on the system settings, this delay cannot be ignored when the required response needs to be as fast as the measurement delay. Furthermore, the linearity of the measurement method is not taken into account because the measurement delay has already been ignored. Therefore, in this paper, a simplified model that considers measurement delay and its linearity is proposed, and a model-based tuning method of PID controllers for two kinds of excitation systems is proposed and compared with the conventional method by analysis. To verify the analysis and proposed tuning method, experiments are conducted for both excitation systems.

Highlights

  • The excitation system of a synchronous generator is set to adjust the output voltage of the generator by controlling the field flux

  • After pole-zero cancellation was performed, the stability of the corresponding excitation system was analyzed by the root locus, and the expected step response was presented assuming the corresponding model was correct in order to be compared with experimental results and verify the reliability of the proposed model

  • In order to verify the proposed simplified model, the linearity of the measurement method, and the modified PID controller tuning methods for both kinds of excitation system, experiments were conducted based on the configuration shown in Figures 21 and 22

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Summary

Introduction

The excitation system of a synchronous generator is set to adjust the output voltage of the generator by controlling the field flux. The auto-tuning method for the PID controller and self-commissioning excitation system have been studied with a view toward reducing processing time and effort Since modeling these excitation systems and tuning the PID controller based on the results is a key technique for enhancing auto-tuning methods, a precise analysis is needed to obtain the required voltage response. The differences between experiment and analysis were somewhat improved in this study; the stable region was still incorrect, and the non-minimum phase zero from the approximation was included in the delay model. This is not a factor in the real measurement delay. The implementation of the self-commissioning and model-based tuning of a PID controller based on the modified model is presented

Simplified Models of the Excitation Systems
Conventional Simplified Model
Simplified Model with Approximated Measurement Delay
Proposed Simplified Model with Linear Measurement Delay
Stability Analysis of the Proposed Model-Based PID Controller Tuning Method
Static Excitation System
Excitation System with an AC Exciter
Proposed Model-Based PID Controller Tuning Method and Stability Analysis
Negative Effects from Measurement Delay with Conventional Tuning Methods
Loop Gain Limitation for Excitation Systems with an AC Exciter
Experimental Results
Conclusions
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