Abstract: An active filter (2) is connected to a dc circuit (L1, L2) in a converter (SR1) in an installation for transmission of high-voltage direct current. Control equipment (5) generates, in dependence on a control signal, a control order (SCF) for the active filter which, in dependence thereon, generates and supplies to the dc connection one of a filter voltage (UF) and a filter current (IF) for reducing at least one tone of a chosen tone frequency in a current (Id) in the dc connection. The control equipment comprises a controlling unit which forms a controller signal in dependence on a supplied current measurement value (IM) of the current in the dc connection, and an identification unit. The identification unit forms a first compensating parameter in dependence on the current measurement value and on an excitation signal generated by the control equipment and added to the control order.

Abstract: A method of packaging articles of a compressible material, such as cleaning sponges, according to which a blank of arbitrary length is cut such that its thickness corresponds to the thickness of the article and its width corresponds to the longest dimension of the article. The blank is folded lengthwise along its center line once and is then again folded along the center line of the once folded blank a second time. The blank, thus folded twice, is advanced through a piece of piping the outer jacket face of which serves as a shaping template for shaping a web of foil into a tubular cover enclosing the blank and the piece of piping coaxially. The tubular cover is brought along by the advancing twice-folded blank at the discharge end of the piece of the piping and the twice-folded blank is cut while enclosed in the tubular cover, into pieces in such a manner that the length of the blank corresponds to the width of the article.