This is an enhanced single phase PLL . The PLL block takes a sinusoidal signal as input; frequency, phase angle and amplitude of the input signal are calculated at the outputs of the block. The E-PLL is an improvement over the basic PLL by elimination of the double frequency ripple.
It was developed following chapter 2, Enhanced Phase-Locked Loop Structures for Power and Energy Applications By Masoud Karimi-Ghartema.