Study On A Feedback Reactive Power Compensator And Its Application

At present, low power factor, abundant harmonics and negative sequence are the three main characters of electrical railway traction load. Setting compensator is the vital technical measure to solve the problems. In this paper, a feedback reactive power compensator is studied, its characters are pointed out, and improved measures and simplified scheme are put forward.This paper is based on New-style Practical Patents of China (2488215Y, 2002-4-10). It analyses the working principle of the novel reactive power compensator, the relationship of currents in stable states, algorithm of filtering capacity and transient process. Based on the analysis of the paper, we can draw the conclusion that this device has several issues to be solved to put into use, such as low filtering capacity, large bulk and area the device occupies, complexity of connection, and the hazard of ferro-resonance existing when switching without disconnecting the circuit of the step-up transformer. Several settlements are analyzed to eliminate ferro-resonance. Since these settlements have disadvantages, the feedback reactive power compensator is infeasible.On account of the disadvantages of the feedback reactive power compensator, a device of its simplified scheme is studied in this paper, in which the reactive power is adjusted by regulating the voltage of the low-voltage side of the transformer. The working principle, the method to calculate the ratio of transformation and algorithm of filtering capacity are also studied in this paper. As the step-down transformer has no load when the SCR is turned off, the system is stable during switching. Less transformers, small area the device occupies, the relative simplicity of connection are the other advantages.Technical and economic benefit of the feedback reactive power compensator and its simplified form is calculated at the last of thispaper. On the calculation, we can hold the conclusion that the two kinds of compensators have no distinct difference at the technical aspect under circumstances of two-phased compensation. The effect of decreasing negative sequence current and harmonics ratio is indistinct, however, both are effective in increase power factor. Thus the selection of the three schemes consists in the economic benefit. Based on the analysis above, the its simplified form of the feedback reactive power compensator is recommended.