Current distortions compensation method for frequency converters

This paper present a study of the effects of frequency converters to the power grid and a possible solution for current distortions compensation. Experimental measurements made, at different points of the grid, with the device Fluke 434 to a converter which supplies a 110 kW asynchronous motor, reveal the distortions of current. Harmonics content of current for the three phases and THD distortion factor emphasize the existence of strong distortions of current. Current compensation method, proposed and simulated, consists in collecting a sample of non-sinusoidal current from the inverter input resistance or using a current transformer, which will be decreased from a sinusoidal reference signal. This difference is amplified and synchronized, so that it can be injected back into the grid. Simulations above described method are made in Matlab-Simulink Power Systems.