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.