| With the development of the power automation technology and the improvement of the security level in the power grid, the role of intelligent circuit breaker(ICB) has drawn more and more attention. When ICB based on microprocessor switches off loads, the EFT/B(Electrical Fast Transient/Burst) will be generated. EFT/B not only interferes the electronic devices of ICB, such as the power supply system and the microprocessor, but also brings negative impacts to the electromagnetic environment around. In the inhibition of EFT/B conduction interference, because of no EFT/B conduction interference model of precision during design phase, power supply filter chosed in the debugging stage based on the experience in the design, finally the intelligent circuit breaker system is often not optimal design. In this paper, EFT/B conduction interference suppression measures of ICB are studied, the generating mechanism of EFT/B is analyzed, the EFT/B conduction interference source system model is established, and to the problem of EFT/B conduction interference disturbance mainly affects the ICB power supply system and microprocessor, forward prediction technology are proposed, and according the results of prediction technology to guide suppression measures.Through the generating mechanism of EFT/B conduction interference of ICB, the conduction path of EFT/B conduction interference are analyzed. Aiming at the typical situation that ICB switching off load(no-load transformer) generates EFT/B conduction interference, the EFT/B conduction interference system is established, including breaker contacts, long cables and no-load transformers. The impedance characteristic of contact are measured and matched with five topological structures, selecting the most appropriate topological structure with which the equivalent circuit of contact is established. The relationship between EFT/B conduction interference overvoltage and the length and the output impedance of long cables is analyzed, and the equivalent circuit of long cable is established based on transmission line theory. Combined with the no-load transformer equivalent circuit, EFT/B conduction interference system model of the ICB switching no-load transformer is established. The established EFT/B conduction interference system is simulated and analyzed, results shows that compared with IEC standard EFT/B conduction interference model is more practical.EFT/B can interfere with the microprocessor of ICB. Because cannot directly inserting the hardware filter for eliminating interference of microprocessor, the only way is to separating the EFT/B conduction interference noise with the useful signals that come from active electronic current transformer, then eliminating it through software filtering algorithm. According to the different states of the Schottky diode in the rectifier bridge, the calculation expressions of the common mode and differential mode interference voltage are given and evaluated as the basis of EFT/B conduction interference quantitative analysis. Based on the selfadaptive subtractive principle and combined with the blind source separation algorithm, an improved self-adaptive optimized separation algorithm is proposed. The algorithm measures the deviation between the estimated parameters and the optimal value by setting measure variables and can adjust the separation algorithm steps automatically. The simulation results of this algorithm show that the algorithm can efficiently solve the contradiction of the dynamic response speed and steady accuracy during the separation process and realize the separation of EFT/B conduction interference. In order to eliminate the influence of EFT/B on the microprocessor of ICB, an improved extended Kalman filtering algorithm based on self-adaptive control is proposed to filter the separated EFT/B conduction interference noise. The improved algorithm weighs the predicted square deviation of evaluated errors to avoid the filtering divergency. The simulation results show that, compared with extended Kalman filtering algorithm, the filtering effect of the improved algorithm is better.EFT/B conduction interference can interfere with the power supply system of ICB. Three power supply modes of ICB are analyzed. Aiming at the negative issues of the common-used hybrid light-electric power technology, a selfexcitation power supply system scheme based on double saturation current transformers is proposed, using saturation of current transformer, reduces the EFT/B conduction interference effectively. According to the different on-off state of rectifier bridge. Schottky diode, the common mode/differential mode interference voltage calculation expression of EFT/B conduction interference through the rectifier bridge side is given, on the basis of which as the EFT/B conduction interference in quantitative analysis. Combined with the small signal modeling method, the mathematical model of the self-excitation power supply system is established. The EFT/B conduction interference of the self-excitation power supply system is analyzed through simulations and experiments. The results show that its inhibition ability of EFT/B conduction interference is better. The deficiency is not directly through the standard of electromagnetic compatibility test, an inhibition of EFT/B conduction interference filter is needed.The suppression technology of EFT/B conduction interference in the ICB is researched, based on the close relationship between the inhibition filter for EFT/B conduction interference with the EFT/B conduction interference source impedance, self excitation power supply system load impedance, a filter for EFT/B conduction interference is proposed. The filter includes a differential mode filter and a set of common mode choke, the common mode choke can effectively eliminate the common mode current of EFT/B conduction interference. The results of immunity experiment of EFT/B conduction interference shows that the designed filter can effectively eliminate the EFT/B conduction interference, so the system of EFT/B conduction interference is not exceeding. |
PDF Full Text Request