In a rural power grid 220kV transformer substation in Liaoning Province, because of the appearance of a lot of new impact loads in the power supply area, the original reactive power repertory can not meet the existing load need. As a result, the output 66kV voltage fluctuation affects the power supply security of the users. After a comprehensive evaluation, it is planned to set up a set of ±100M SVG to increase the reactive power repertory to stabilize the system voltage. The electrical system of 220kV transformer substation is huge and often meets with sudden failure; and the capacity of this set of SVG is large, so it may worsen the situation in case of improper control. This paper discusses several operational modes that SVG should have and designs a scheme that can be flexibly switched in several operational modes, which is specifically executed by an overall coordination module. This method has passed the preliminary field operation verification.
Electrified railway traction transformer is a pivot that connects the electric locomotive and the public grid. Therefore, power quality problems caused by electric locomotive such as three-phase voltage imbalance, great voltage fluctuation and high harmonic content can be transmitted to the public grid via the traction transformer. To solve this problem, the solution of two sets of single-phase SVG (Static Var Generator) in back-to-back operation to solve power quality problems of the electrified railway is raised. This solution has been proved by practice effective in improving power quality of the traction transformer.
The dry hollow reactor has the features of good inductance linearity and heat dissipation and is not easy to produce ferromagnetic resonance with capacitive load in the system. Therefore, the phase controlled reactor in TCR-type SVC is usually a dry hollow reactor. According to years’ actual operating condition, the phase controlled reactor in 35kV SVC or SVC at a lower level operates stably while tree discharge or breakdown failure frequently happens to the phase controlled reactor in the 66kV vertical SVC, which seriously affects the stable operation of the equipment. This paper puts forward a method of installing arrester on the phase controlled reactors to relieve the SVC switching overvoltage impulse and protect the phase controlled reactors. Besides, it uses PSCAD to conduct a simulation and verifies the feasibility of this method.
In order to online estimate the state of charge (SOC) of lithium-ion battery pack in this paper. This article establishes a dual Kalman filter (DEKF) algorithms for it. We establish a battery model of state space expression based on Thevenin battery model and Kalman filter algorithms. We use least square method and DEKF algorithms to identify the parameters of battery model in order to improve the accuracy of battery model. It can make battery model reflect true state of internal battery well. It introduces the principle which is dual Kalman filter algorithm online estimate the state of charge. Finally, it verifies DEKF algorithm has better convergence and robustness which can effectively resolve the problems of initial estimates error and cumulative error issue.
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