Study On The Protection Of Active Power Filter

Currently the researches for Active Power Filter (APF) have two purposes: One which studies the influence of APF on system, and the other which studies the system influence on APF, that is, the security and reliability of APF. In this thesis, Phase-Locked Loop(PLL) technogies are used to acquire phase of fundamental current in bais current, which enhances the detecting precision of bais current. And we want the phase of bais current and the phase of system current is the same,so this thesis think of locking the phase of bais current which based on this theory to sure the security and the reliability of APF. And, the drive protection circuit is improved in this thesis, hence the working reliability of which is also enhanced. What's more, this thesis analyzes the feasibility of introducing varistors and thermistors into the APF protection, in order to acquire more secure working with active power filter.