Impedance measurement for improved power quality-Part 2: a new technique for stand-alone active shunt filter control

This work describes the development of a new "stand-alone" active shunt filter. The control employs online power system impedance measurement to optimize the current control algorithm and to provide the filter\´s reference currents. The current control employs additional rotating frames of reference at fifth and seventh harmonic frequencies and is specifically for high kilovolt-ampere applications where the switching frequency is constrained to 4 kHz. This results in an improved immunity to disturbances such as supply distortion, pulse-width modulation (PWM) imperfections and processing delays, and provides excellent steady-state current control. Experimental results confirm the operation of the new controller.