Hi Chris Chang,
without wasting any time let me come to tht point. your question is how to implement a power factor controller using 8052 mcu. the fact is that will be able to implement this using 8052 mcu.
how to do this is as folows.

1)you will need a CT(current transformer) and PT(potential transformer)

2)now you have to measure the phase difference between the voltage and current through these transformer.
this is how how you go about it,

a)use a zero crossing detector for the two transformers(CT and PT)using adequate circuit.

b)now take the instant when the voltage crosses the zero refference as refference point and then measure the time required buy the current waveform to cross the zero refference. this is your phase difference between the voltage and current.

3)now according to the the power factor you have to add capacitors or inductors (depending on lagging or leading power factor) in your power system to improve the power factor to unity.

to implement this on a 8052 follow the steps

1)use the two external interupts for the zero crossing detectors.

2)let the priority for interupt used for voltage zero crossing be highest.

3)when the voltage zero crossing triggers a interupt
start the timer (the timer overflow can be programmed such that it overflows after a time interval equivalent to one electrical degree)

4)when you get the interupt due to current zero crossing stop the timer and compute how many times the timer has over flowed. this will give you the actual time in electrical degree.

5)now to determine leading or lagging power factor is the job of your code.

6)depending on the power factor you can switch on the required number of capacitor banks to do the power factor improvement.

i hope this will solve your problem.
if you still have a problem let us know.

mayur...