Research On Auto-disturbance-rejection Control And Its Application In Excitation Control

The Auto-disturbance-Rejection control is an innovative technology, proposed by Han Jingqing who works at CAS. To a certain extent, the technology subverts the model theory. Its working principle in the methodology is of great significance. However, because it is not perfect in some ways, the theory has not yet been widely accepted. Discovering and improving its inadequacies will certainly be conducive to the improvement and development of technology.In this paper, a rigorous mathematical analysis and numerical simulation experiments have found that the linear ESO(Extended State Observer) has serious peaking phenomenon when there are initial errors. The peaking phenomenon caused by the initial error's first element is most serious. At the same time, ESO's component of the last output, which is a measurement of the disturbance, is most prominent. Although the duration is very short, the amplitude is very large. Because of that the control effects have serious implications, or even become opposite value. Subsequently, a detailed analysis of its mechanism is given by the paper. Finally, three solutions are proposed. The first one is to set initial value of ESO in the algorithm to eliminate the initial error. The second one is to limit control amplitude, which also works with the actual situation of control. Third, a filter can be added to eliminate the peaking phenomenon caused by noise. Simulation results show the methods are effective.There are parameters uncertainty, structure uncertainty and randomness of fault in a power system, which decides that the control object of excitation system is uncertain. Adopting ADRC, strong robustness of the generator excitation control system can be got, which is conducive to improving the system voltage stability and power angle stability, and ultimately enhances China's power quality. The deficiencies found in practical application, in turn, will accelerate the theoretical further improvement.Uncertainty is divided into two broad categories, namely matching uncertainty and not matching uncertainty. The analysis shows that due to its uncertainty matching g's linear space, the system can still be transformed by diffeomorphism coordinate transformation into integrator Series form. So, all of the uncertainty explicitly appeared on the control channel, which can be observed and compensated by ADRC, and the purpose of feedback linearization and suppressing disturbance can be achieved. Based on the above theory, the generator excitation control systems were analyzed, and, a new excitation control law was proposed. At the same time, according to the actual situation, ESO's input should be as high as possible order variables of the observed system, which can reduce the order of the observer and improve accuracy. Finally, simulation is carried on PSASP(Power System Analysis Software Package) by user-defined program. The results showed that the proposed control law improved the level of system stability.