Li Qunzhan

Wavelets Selection for Commutation Failure Detection in HVDC System

This paper presents a wavelet based commutation failure (CF) detection technique in HVDC system, and selects the suitable mother wavelet. The different properties of wavelets are analyzed in detail. It is shown that the orthogonality, regularity, moments, and symmetry of a wavelet function may affect the CF detection to some extent, and the critical factor is the moments of the mother wavelet. Discrete wavelet transform (DWT) has executed respectively on normal sinusoidal voltage signal and alternative voltage record with CF in Tianguang HVDC project. The transform result shows that DWT by Daubechies wavelet function with high vanishing moments is a cogent tool for CF detection in HVDC system

Energy Saving Train Control for Urban Railway Train with Multi-population Genetic Algorithm

The problem of urban rail train energy saving control with specified running time is a typical multi-constrains, non-linear optimization problem. By applying minimum principle to differential motion model of trains, the energy saving control strategies are obtained. An approach for optimizing problem based on variable-length real matrix coding multi-population genetic algorithm (MPGA) is presented. The train running is simulated by a multi-particle simulator considering complicated line conditions and influence of train length. The GA chromosome consisting of a variable-length two dimensional real matrix represents the train control sequence. A variable length operator based on annealing selection is introduced to enhance global search performance. Fitness sharing keeps populations multiplicity. Multi-population parallel search improves convergence rate and evolution stability. The correctness and advancement of the optimization control method have been validated through the simulation platform of train operation.

Study on Algorithm and Communication Protocol of Differential GPS Positioning Based on Pseudorange

This paper presents a method of GPS differential positioning based on pseudorange. Both the generation and encoding of differential data based on pseudorange and differential data transmission protocol based on Interne are mainly discussed in the paper. An improved communication protocol is proposed which can decrease the transmission quantity without changing the differential positioning accuracy. The comparison between original data and coding data and the improved coding data are tested by instantiations. Experimental results show the modified coding method decrease the transmitted data amounts compared with the point positioning. When there are more than 9 satellites, the transmission quality acquired by this advanced communication protocol is only 70 percent of the RTCM protocol and the accuracy of the differential position is greatly improved.

Application of expert system based on mixing reasoning in traction substation fault diagnosis

When there is a fault in traction substation the fault components and their reasons are required to be identified by operators quickly and accurately. A fault diagnosis expert system based on mixing reasoning is built in this paper. It can reason according to logical relations of relay protection and breakers and fault waveform of voltage and current provided by Fault Record System (FRS). Mistrip and failure to trip of relay protection and breakers can both be distinguished The reasoning result has a good credibility. Traction substation fault diagnosis expert system may be used as a module of integrated automation.

Wind Speed Forecasting Based on Combination Forecasting Model

The accuracy of wind speed forecasting is related to the wind power scheduling. When large-scale wind power connected grid, it also affects the stability of the grid. This paper applies time series model and Back Propagation (BP) neural network model to predict wind speed. Finally, a combination model of time series and BP neural network is proposed. In the combination model, the inputs of BP neural network are made up of historical data and residual errors calculated by time series model. The model can be more accurately in the short-time wind speed forecasting. And then shows an actual example.

The research on main protection for DC feeder line of subway

This paper evaluates all kinds of main protections for DC feeder line of subway and points out their drawbacks. On the base of analyzing characteristics of current under tow load and short-circuit in DC traction power supply of subway, it presents a main protection-rate-of-current-rise protection (di/dt- /spl Delta/ I). Then, the characteristics of ROR (rate-of-current-rise) protection and the principle of setting are given. By simulation, it is proved that the design of ROR protection is rational.

Control strategy of symmetry compensation system of traction power supply system in phase

The paper presents an analysis for the control strategy of symmetry compensation system (SCS) of traction power supply system in phase (TPSSIP). The theory of traction power supply system in phase and three study conditions are classified. The method that conforms the capacity of symmetry compensation system is outlined. The control strategy of SCS is validated by simulation program.

Some Key Problems on Cophase Traction Power Supply Device

This paper analyzed a scheme of cophase traction power supply system for electrified railways based on cophase traction power supply device (CTPSD). The advantages of this new CTPSD over other controllers are presented by describing the main circle, functions and control strategy in detail. Furthermore, the two typical behaviors which are normal running and regenerative barking of the electrical locomotive are simulated to present the balanced conversion and compensation effectiveness. Results shows that the cophase traction power supply system based on CTPSD is a good solution for the seriously-unbalanced three phases, reactive power, low power factor and harmonic current existing in traction power systems for electrified railway. Combined with the energy storage system, CTPSD can further solve the problem of electrical locomotives’ regenerative braking power-feedback.

Application of Improved Analytic Hierarchy Process to Some Scheme Optimization for High-Speed Railway's Exterior Power Supply

In the design of high-speed railways traction power supply system, the choice for exterior power supply concerns many factors, and is a multi-criterion decision problem. In this paper, the principle of analytic hierarchy process (AHP) based on rough set theory and group decision-making is presented. An index system of exterior power supply evaluation is then constructed. Through independent decision making of each expert and the definition of the attribute significance based on the weighted sum, the weight values of alternatives is obtained and ranked, the quantitative description of decision process is realized and the optimum scheme for exterior power supply is determined. Taking an under construction high-speed railway for example, the availability and reasonableness of the proposed method is demonstrated.

Development of test and simulation software kit of integrated automation for traction substation

This paper discusses a new practical real-time software testing and simulating of integrated automation for traction substation. This software is used both to operate human-machine interface and also to test and simulate for protection devices. Then the software kits system configuration, functions, dispose flow, technique characteristics and test results are all be described.