Switching of power harmonic filters

Power harmonic filters are installed at the AC input terminals of rectifiers, motor drives, UPS, and other nonlinear loads to reduce the distortion of the terminal voltage at the point of connection. The design guide for these filters, such as IEEE Std. 519, assumes a fixed load condition, and does not focus on switching of the filters. In actual operation, this is not usually the case, and the filters are switched as a function of the operating system conditions. Power harmonic filters can be switched by contactors or thyristors to control overvoltages, reduce losses, and limit harmonic currents from other sources. Examples are shown of switched filters on elevator drives, adjustable speed pump drives, and reactive power compensators. PSpice generated waveforms for the 5th harmonic section for the elevator drive are included. Parametric calculation of the capacitor kVAr on no load and full load is investigated