I do alot of Liturature review on Shunt Active Power Filter, But I am confuse on some points:

1. When we used a Pure APF circuit design: we inject Vdc into the Id ?

2. When we used a Hybrid APF circuit design: we inject Vdc into the Iq?

Why?

3. By injection from inverter to PCC mean what ? I mean its about actual current or only harmonics and if its harmonics then why it effect the actual current value ?

4. According to the theory, the APF operates when the Vdc is higher than the Peak value of the source voltage rms. But what about the Id value, its should be always same or higher also ?

Thanks