Patent ID: 9331561
Filing Date: 2016-05-03
CPC Classification: H02J,H02M,Y02E

Claim Text:
1. Method for the improvement of the line quality in a system, comprising: feeding via a common feeding with at least one distribution transformer at least two non-linear loads drawing non-sinusoidal currents from the common feeding; wherein between the common feeding and the distribution transformer there is at least one primary side transformer line and between the at least one distribution transformer and the at least two non-linear loads there is at least one lower voltage secondary side transformer line; wherein at least one active filter attached to at least one lower voltage secondary side transformer line is used for the attenuation or elimination of higher order harmonics experienced by the common feeding; wherein synchronization voltages are measured on the lower voltage secondary side transformer line and are used to calculate the voltage rms values on the secondary side transformer line as an adjustment for asymmetries, parasitic character, or a combination thereof of the transformer, wherein the current in the transformer line is used to control the active filter; and wherein said current in all lower voltage secondary side transformer lines is not directly used as an input reference for the active filter but from said current in the lower voltage secondary side transformer lines, using a computational model of the distribution transformer, the current on the primary side transformer line is calculated, and therefrom, using a computational model of the distribution transformer, the current on the secondary side transformer line is back calculated, and this current is used as input reference to the active filter.