Over the past years, the number of electrical systems in airplanes, and thus their power ratings have been rising. Therefore, the optimization of devices and actuators regarding efficiency and power density has become increasingly important. Besides the large topic of weight reduction at component level, aircraft manufacturers and several research projects have focused on the topology of the entire electrical grid. One possible topology may divide the whole network into subnets and an active power filter maintains the power quality at the connection to the main bus. This solution allows the use of simple diode bridge rectifiers in all power electronic devices within the subnet, which results in increased reliability, power density and reduced costs. Since most of the actuators e.g. in a wing are not driven permanently and not simultaneously, the power rating of this active power filter is significantly smaller than the power rating of the entire subnet. This paper presents the control algorithm for an active power filter for aerospace application, which requires robust behaviour towards frequency transients and high compensation accuracy in steady state operation.