Research On Influence Characteristics And Test Technology Of Voltage Sag On Typical Sensitive Equipment

With the advance of power technology and the development of smart grid construction,power system has undergone tremendous change:on the one hand,the number of distributed power,electronics devices and impact load access to power grid has a great increase,which have directly or indirectly harm to the grid quality power;On the other hand,the extensive application of programmable devices,computer equipment,frequency conversion equipment also put forward higher and higher requirements to the power quality of the grid.Among all power quality problems,the voltage sag caused the greatest economic losses and caused most user complaints,so that relevant research is imminent with the widely use of sensitive equipment.Based on the previous research,this paper studies the influence characteristics and test technology of voltage sag on typical sensitive equipment.The main contents of this paper are as follows:(1)Study on propagation of voltage sags.In this paper,the propagation of voltage sags in the power grid,especially in the transformer were studied.The different types of voltage transformers are modeled,and the propagation of different types of voltage is simulated,in the end,this paper summarized the propagation law of voltage sag.(2)A method to calculate the area of vulnerability is proposed.Based on the traditional fault point method used to calculate the area of vulnerability,an improved proposal is proposed:the least squares method is used to fit the function relationship of the PCC point voltage and the position of the fault point,and then obtaining the area of vulnerability according to the function relationship.(3)The voltage sag tolerance of sensitive equipment is simulated.The working characteristics of common sensitive devices under voltage sag are analyzed and the sensitive users are classified.The working characteristics of typical sensitive devices are simulated,including AC contactors,frequency converters and photovoltaic inverters,and the difference of voltage sag tolerance of typical equipment and its influencing factors are obtained.(4)A tolerant test platform was designed and typical sensitive devices are tested under voltage sags.The voltage sag test platform was used to test the tolerances of three kinds of typical sensitive devices,including AC contactors,frequency converters and PV inverters.According to the relevant experimental data,the voltage sag tolerance curve is drawn,and the tolerance curves of the three typical devices are analyzed.