Liu Yingyi

The Operating Transient Process Analysis and Synchronous Switching Strategies Research of Vacuum Breaker

Circuit breaker switching operation will generate transient voltage and inrush current. The synchronous switching control strategies research can effectively reduce the transient effect and improve power quality. The transient operation process of vacuum circuit breaker is analyzed by deriving the system voltage and current expressions when vacuum circuit breaker switching reactive compensation capacitor bank. The theory switching phases without transient transition process are obtained by referring to the voltage and current expression. The optimum switching capacitor banks phase and new synchronous switching control strategies of different connections capacitor bank are given by synthetically considering closing action time dispersion, pre-strike characteristic and opening arcing time of vacuum circuit breaker. The voltage and current waveforms when vacuum circuit breaker randomly, according to traditional and new synchronous switching strategies switching ungrounded Y capacitor banks connection are simulated in the article. Simulation results show that the inrush current under the new synchronous switching control strategies can be reduced 1.2p.u.and closing voltage has no oscillation transition process, that is, directly accesses to steady-state. So the theoretical analysis and synchronous switching control strategies in the article are verified correctly.

The Modified Shuffled Frog Leapping Algorithm and Dynamic Behavior Analysis of Local Search Process

Shuffled frog leaping algorithm (SFLA) is one of promising optimistic methods which are based on swarm intelligence. SFLA combines the advantages of memetic algorithm and particle swarm optimization. It has been widely used to solve complex optimization problems in engineering fields. To enhance the convergence and effectiveness of local search process in SFLA, a novel individual update method is presented and the dynamic behaviors of local search are analyzed in detail. On the basis of the proposed approach, the modified SFLA is presented. Simulation experimental results show that the modified SFLA achieves more efficiency than the classical shuffled frog leaping algorithm.

Corona Current Data Acquisition Card Based on USB Bus in Extra High Voltage Environment

This paper introduces a corona current data acquisition card based on USB. According to the characteristics of the corona current, the hardware circuit of USB acquisition card includes signal conditioning circuit, data acquisition circuit and peripheral circuit, and the program needed for the device including PC driver and application program were designed. In order to verify the function of the corona current measurement system, the performance test and the field test of the USB acquisition card are carried out. The test prove the data integrity of the data acquisition card and the accuracy of the data acquisition. It shows that the acquisition card is steadily, accurate, and can meet the requirements of the index.

Design of Space Charge Density Measuring Device Based on Air Filtration Methods

To measure space charge density around UHVDC transmission lines, a measuring device is developed based on air filtration methods. The device, which uses STM32 microcontroller as the core controller, collects charged particles in the air by adsorption material. Through the charge to voltage converting circuit, charges absorbed are transferred into a voltage signal and are collected by microcontroller. Space charge density in the region is calculated combining the air flow measured by hot-wire anemometer. To reduce the measurement error, the equivalent circuit model of air filtration methods is analyzed. The source of error is analyzed and methods to reduce error are obtained. The device is used in ultra high voltage DC test base to measure the space charge density under UHVDC transmission lines. The results show that there are similar tendency compared with the theoretical value of bipolar transmission lines. The feasibility and availability of the device is verified.

Research on Data Consistency in Electric Field Measurement

Experimental studies are reported that measuring results of electric field mill are inconsistency, which affects their measuring accuracy. This paper introduces the principle of electric field measurement. Statistical analysis of calibration experimental results shows that measurement data obey normal distribution rule. Correlation analysis result indicates that the distance between two electrodes of field mill has a strong linear correlation with measure results. Linear model is established with the method of regression analysis. Finally, residual test verify the rationality of regression model.

The Research of Fast Vector Transform and Its Implementation

Digital image coding includes vector coding and scalar coding. Vector transform is an important content to realize image vector coding. According to the unequal dimension between the input matrix and output matrix in the classic transform, a fast vector transform with equal dimension is deduced. The computational efficiency and the transform performance are analyzed, and the basic block of the fast vector transform implementation, the circuit diagram of a skew-rotation unit, is presented. The research can provide the theoretical and technical foundation for the vector transform.