Electrical Network Power Flow Analysis And Research On New Measuring Methods Of Electric Energy On The Condition Of Distorted Signals

Along with the rapid increase of non-linear loads in the electrical network, the electric energy quality becomes worse and worse, which not only seriously affects the effectiveness and safe running of the electrical network, but also proposes a new challenge to the classic measurement theory on electric energy, its method and the instrument design. In modern electrical network, besides stable state fundamental component and harmonic signals, there are the signals with quasi-periodic, time-variable and the non-stable state complex characteristics, which has caused complex power flow change in the electrical network, and exposed serious unfairness in the existing measurement method. Under the harmonic condition, according to power flow direction of the harmonics, the harmonic source user sends out the harmonic power,causing the decrease of the electric energy measurement, and the un-harmonic user absorbs harmonic power, which makes the electric energy measurement increase. Therefore, the traditional measurement method has caused the serious unfair problems. After analyzing the power flow characteristics of stable state harmonic source signals, many scholars in the world proposed the technical plan of electric energy meter testing fundamental wave, which has already been experimentally applied to the non-linear loads of using electric energy in the electric energy measurement, and has caused certain result. But the fundamental wave meter is not suitable for the electric energy measurement of the time-variable and non-steady signals which are more universal cases. On the condition of serious distortion of the electrical network signal at present, how to carry on the electric energy measurement has already become a difficulty and the hot topic in the domain of electric energy measurement. In view of this question, this dissertation has conducted the thorough and systematic theoretical research and the correlative experimental study.In this dissertation, firstly, domestic and overseas measuring methods of electric energy and the research status of meter on the condition of steady distorted signals and the development and application of electric energy measuring techniques have been overviewed. On the condition of distorted signals the problems existed in electric energy measurement have been focused on. A mathematical model for typical unsteady distorted signals of the electrical network has been established, and power flows for unsteady distorted signals have been analyzed thoroughly and systematically. A rational measuring method of electric energy for distorted signals has been proposed and the sub-band measuring method based on wavelets has been employed for decomposed measurement of electric energy on the condition of unsteady distorted signals, and thus realized in theory the accurate measurement of power of the distorted signals. Secondly, typical distorted signals in the electrical network has been tested by computer simulation and the simulation results have been given in the dissertation. Thirdly, the thesis designed simulative signal resources of the electrical network and experimental equipment of measuring energy on the condition of distorted signals,and tested the typical distorted signals in the simulated electrical network. The simulation and experimental results show the rightness of the theory presented in the thesis. Finally, according to the problems existing in electric energy meter, the technology scheme of designing a electric energy meter which has wide band and high overloads capability for measuring transient energy of unsteady distorted signals such as impulse signals, is also presented.