Beads of water cling to its screen, necklaces unstrung, locked by the screen's grid into something like a checkerboard, if checkerboards wore jewelry.

Three-phase PLL is researched about connetting grid and phase locked of PWM rectifier in the thesis.

The online variable step can also regulate the voltage convergence rate, and the phase-locked control circuit is designed to synchronously trace frequency and phase of power grid automatically.