SIMPLIFIED MODELS OF ELECTRIC DRIVES WITH FREQENCY CONTROL IN STUDIES OF POWER QUALITY
. The article presents two simplified models of AC drive with adjustable speed with voltage
inverter and voltage generation using pulse width modulation-physical and mathematical, designed to assess the degree of total harmonic distortion of the line current. The physical one is an input rectifier inverter turned on to the network in series with a mains choke. A resistor is connected to the DC bus-simulating the load of an asynchronous motor. A similar scheme implemented in the SIMULINK software in the form of a mathematical simplified model was investigated. The aim of the study was to determine the possibility of using simplified models to assess the relationship between the total levels of harmonic distortion and the relative harmonics of the current consumed from the network, from the magnitude of the inverter load. The obtained simulation results are compared with the models and results of a physical model with a frequency Converter and an asynchronous motor. The visualization of functional dependencies between the fifth, seventh and eleventh harmonics, respectively, total harmonic distortions and network current consumption is shown. As a criterion for assessing the similarity of the simulation results, the hypothesis of equality of the average statistical samples was proposed and nonparametric comparison methods were used. The presented graphs illustrate the obvious similarity of the results obtained on the physical and simulation models with the data of the field experiment, which was confirmed by statistical studies. This is most clearly shown in the diagrams of type "boxplot", from which it follows that the median physical model with asynchronous
motor is guaranteed to be in the range of ±0.5 standard deviations from the mean of the sampling model in MATLAB. A preliminary conclusion is made about the adequacy of models based on comparison of experimental data.