Research On The Influence Of Transformer Characteristics On Power Quality Monitoring And Measurement

The importance of power quality as a hot topic for users and power companies is of great importance.However,with the rapid development of China's economy,a large number of special users(smelting,electrified railways and high-power rectifier equipment)have been integrated into the power grid,which has caused power quality problems such as harmonic pollution,voltage fluctuations,and flicker.The consequences of large influx of high-order harmonics not only affect the power transmission capability of the power grid,but also jeopardize the safe and stable operation of power equipment,causing potential safety hazards in power production.Therefore,it is necessary to effectively suppress and deal with the harmonic components in the power grid.When the data of the harmonic voltage in the power system is collected,it needs to be completed by means of a voltage transformer.However,since the electromagnetic voltage transformer is limited by its research mechanism and the applicable frequency band is narrow,there is a large error in measuring the higher harmonic wave.At the same time,the voltage transformer and the current transformer are used as the input devices of the power metering front-end.The accuracy of the electrical signal conversion will directly affect the accuracy of the metering system's metering energy.It is of far-reaching significance to study the frequency transfer characteristics of transformers.In order to solve the problems of high-order harmonic monitoring and energy metering accuracy,the main research contents of this paper are as follows:(1)After setting up a single-phase equivalent model of electromagnetic voltage transformer under no-load condition,conduct no-load test of voltage transformer and obtain the nonlinear resistance and nonlinear inductance curve in the equivalent model through the split-line method to obtain the nonlinearity of voltage transformer.(2)The harmonic source method and scattering parameter method are used to verify the broadband transmission characteristics of the voltage transformer and the voltage transmission ratio correction coefficient at each frequency point in the time and frequency domain.And through the current error method,the broadband transmission characteristics of the current transformer and the current transmission ratio correction coefficient are obtained(3)Using voltage transformer correction coefficient to propose a power quality monitoring method that takes into account the broadband transmission characteristics of voltage transformers to achieve accurate monitoring of power quality.At the same time,the correction coefficients of voltage transformers and current transformers are used to correct the electric signal before entering the energy meters.The previous electrical signal enables the meter to accurately measure the electrical energy and achieve the purpose of enhancing the accuracy of electrical energy metering.