SUMMARYVoltage stability analysis always involves a large number of devices with various dynamic characteristics in power system. For properly capturing static and dynamic behaviors providing insights into characteristics of the voltage stability of the system, different system models are established for different time-scale studies. In this paper, relevant system models are discussed taking into account load characteristics. Based on these models, different approaches such as static analysis, time-domain simulation and quasi-steady state (QSS) approximation are implemented into a simulation program, which is used as a comprehensive tool for analyzing voltage stability. By complementary use of these approaches with the simulation program, voltage collapse stresses of the system under a critical operating condition can be analysed in steady state, and impacts of special events on the voltage stability can also be simulated with time-domain simulations. For time-domain simulations, a full system model and a QSS approximation can be adopted for capturing different forms of instability mechanisms. A test system is used to demonstrate the feasibility and effectiveness of the approaches implemented.

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The driving stability and comfort-ability are directly influenced by steering system, and it is a critical component in an automobile. Torsion bar torque sensor signal and the vehicle speed signal are used to calculate the assisting torque that on the motor shaft. The rules about how to calculate desired torque signal is very important for driving portability and stability. Influence of motor control strategy on assisting response characteristic. In this paper adaptive fuzzy control rules is proposed for the assisting characteristic and power motor. Base on assistance characteristic and assistance motor fuzzy control is designed. Fuzzy information processing torque signal, vehicle speed signal, with MATLAB simulation contrast experiment, and the result validation the fuzzy controller.

Electronic power steering (EPS) system is a critical component for vehicle safety driving. The damping force of automobile steering is decreased at high speeds, so the driving feel is floating. When vehicle suspension shock and a front wheel sensitive to road counterforce it is relation with the driver safety. For the subject of vehicle stability at high speed, an EPS system control strategy of stability has been presented. In order to keep driving feel, when the steering resistance decrease an elastic damping will be increased. Current follow control technique is introduced, and the torque sensor can estimate the vehicle state. This method can be verified by the experiment.