Phase Shaping Method for Negative Input Admittance of Buck Converter Based on Sliding Mode Disturbance Observer

Abstract

The power electronic converter that supplies power to the unmanned ship's servers can cause self-excited oscillation of the LC input filter under heavy load. To suppress voltage oscillation, an input impedance shaping method based on a sliding mode disturbance observer is presented. The self-excited oscillation mechanism of the LC filter caused by the buck converter's positive feedback is analyzed by using the small-signal model. The sliding mode disturbance observer calculates the input voltage according to the output voltage, inductance current and duty cycle of the buck converter. The feedforward compensation of the observed voltage reshapes the input admittance of the buck converter, making the system not meet the conditions of self-excited oscillation and suppressing the voltage oscillation of the LC filter. The phase shaping of input admittance is compared with the traditional amplitude shaping by the Bode diagram and Nyquist diagram. The experimental results show that the phase shaping method could better suppress the LC filter's self-excited oscillation and the sliding mode disturbance observer reduced the hardware cost.

Keywords

• Sliding mode disturbance observer
• impedance shaping
• constant power load
• self-excited oscillation
• positive feedback