The proposed stable feedforward filter makes the control switching with sign functions to produce a continuous and measurable signal so that the actual control law is smooth.

The results show that a longer feedback filter tap-length is not necessarily better when the feedforward filter tap-length converges to a certain range and the decision delay maintains a fixed value.

For the control of shunt APF (Active Power Filter), feedforward is an effective way to track the load variation, but accurate models and parameters are demanded.