Flicker compensating apparatus for DC arc furnace

A flicker compensating apparatus for a DC arc furnace connected via an AC/DC converting means to an AC power system, comprising flicker compensating means for applying reactive power to the power system and having, for each phase of the AC power system, a reactance for controlling through a thyristor switching element a current supplied to a reactive load and a capacitor for serving as a high frequency filter and improving a power factor, a control circuit for the thyristor switching element comprising calculating means for calculating an effective value of a reactive power of the DC arc furnace, wherein said calculating means comprises:

• a calculating circuit comprises:
• current detecting means for detecting an instantaneous value of an effective DC current flowing through the AC/DC converting means;
• phase angle control means for controlling a phase control angle of the AC/DC converting means;
• converting means for obtaining a no-load DC voltage of the AC/DC converting means;
• and
• predicting means for calculating the effective value of reactive power of the DC arc furnace based on the detected instantaneous value of the effective DC current, the phase control angle of the AC/DC converting means, and the no-load DC voltage of the AC/DC converting means;
• power detecting means for detecting the reactive power of the power system;
• and
• means for controlling the thyristor switching element based on a difference between the reactive power calculated by said calculating circuit and the reactive power detected by said power detecting means.