What does a negative active power means?

Answer 1

Let see an example. The active power absorbed by an AC motor is used to produce mechanical power delivered on the output shaft. If the mechanical power is negative (the motor is pushed to work as a brake) the active power 'absorbed' is also negative. The motor converts the mechanical power in active electrical power delivered in the electrical network. Any AC generator is supplied with negative active power, or it deliver to the network positive active power.