As it is both significant and practical to study how the bidirectional wireless power transmission system can be applied to the monitor control of electric vehicle under V2G environment, this paper analyzes how the bidirectional wireless power transmission system works, based on which, probes into the phase difference θ, which will influence the energy transmission direction, and ratio-voltage σ, which will influence transmission efficiency. It also promotes that coaxial installation of detection coil on secondary side and main power coil can monitor the 2 parameters in real time, and it also provides how to access the parameter. By simulation and experiments, it proved the feasibility of this method, providing a reference research approach on related studies.
Abstract. In order to study the intelligent verification system of microprocessor-based relay protection tester, a novel software platform of integrated automatic verification system is designed in this paper. First of all, the composition and principle of the verification system are introduced, and then the communication between the relay protection tester and high precision AC-DC meter whose entire closed-loop system is completed theoretically. The software platform adopts the design concept of layering and modularization. Through the program generation platform layer, the verification schemes of relay protection tester under tested with different voltage and current output channels are completed to edit and design. Through the hardware interface layer, the communication modules of driver module and verification system of relay protection tester under tested are complete to design. Through drive modules of tester, analog voltage and current output are completed. Through communicating with high-precision meter, the reading of measurement is completed. And also, the calculation and result judgment of measurement error and test report generation are intelligently completed. The designed platform implements to automatically verify microprocessor-based relay protection tester, which greatly improves the efficiency of the verification system.
Abstract. By taking ring main unit(RMU) as a research object, this work calculates the grades of evaluating the healthy running state of RMUs, constructs the evaluation indexes system, measures the weights of state variables and finally determine comprehensive evaluated results. The modeling the characteristics of healthy running status of RMU is of significance to power distribution management.
With the enlargement of power grid scale, connections between different power subsystems in interconnected network have been more-closely related and the analysis of power system dynamic behaviors becomes more complex. This paper selects 3 area indexes which comprehensively reflect frequency change through transient process based on transient frequency stability curve and frequency change ratio curve, and there out builds the quantitative assessment method of frequency fluctuation characteristics. Then a generator set speed governor magnification-targeted optimization model, which determines the optimum of frequency fluctuation characteristics as optimal objective with proposed indexes, is built and solved by multivariate optimization algorithm. At last, an optimal example of practical power grid verifies the feasibility and validity of the proposed assessment method and the optimization model.
Based on the existing time-of-use electricity price pricing scheme of Beijing, a real-time pricing scheme for electric vehicle charging is proposed in this paper to perform load shifting by adjusting the hourly-changed charging price. A twostage model of determining electric vehicle charging price is proposed. In the first stage, the charging load of the next day is predicted according to statistical probabilities. Together with the prediction of the base load pattern, the charging price of each hour is then optimized accordingly as a reference for the next day. In the second stage, the exact charging price is set ahead of each hour based on the power demand in previous hours and the desired load curve. The model is first built and then solved using the CPLEX software and MATLAB programming. The simulation result shows that the peak load as well as the peakvalley load difference is reduced. The charging cost of customers is also expected to be diminished.
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