a. What are the advantages of using an inner current control loop for a voltage source converter rather than trying to directly control the voltage applied?

b. What is gained through the addition of the voltage feed-forward gain in a closed loop current regulator?

c. What are the advantages of implementing the inner current controllers for a three phase voltage source converter to act on variables in the synchronous d q reference frame as opposed to acting on them in the stationary a b c reference frame or stationary α-ß reference frame. How would the controller design be changed if either of the a b c or α-ß based implementation were used?

d. Why is synchronization circuit, such as a phase locked loop (PLL), needed for a grid connected voltage sourced converter? What does the output look like? Is the PLL needed for every type of controlled application?

e. The three phase grid connected applications often use a synchronous reference frame based PLL where Vsq (t) is regulated to zero. Sketch a system diagram and show Vs (t) is located in the system diagram? How does this simplify outer control loops for real and reactive power?

Answer rating: 100% (QA)

a The advantages that an inner current loop brings to power supply design and performance are well known Current mode control is usually preferred over direct duty cycle control because of the superio... View the full answer