A new second order nonlinear tracking differentiator and application

A Second-order nonlinear tracking differentiator (SONTD) constructed by a symbol function sign and a linear saturation function sat has good tracking and differential performances for smooth continuous input functions, but it isn´t appropriate for step type of input functions, In order to overcome the defects of the SONTD constructed by sign and sat, a new nonlinear saturation function composed of a sine function and a sign function is introduced, and a new type of second-order nonlinear TD is constructed based on the nonlinear saturation function. The new SONTD is used in Passivity based control of voltage source PWM rectifiers to improve the transient performances of rectifiers. Simulation results show that the new type of SONTD has good tracking and differential performances for step type of input functions, but it isn´t appropriate for smooth continuous input functions.