Analysis of subharmonic oscillations in multi-phase ferroresonance circuits using a mathematical model

The article about solution of system of nonlinear differential equations that are almost impossible to solve by analytical methods by constructing a mathematical model of nonlinear oscillations occurring in three-phase ferroresonance circuits. A system of nonlinear differential equations was formed by approximating the volt-ampere characteristics of a ferromagnetic element in a ferroresonance circuit. Mathematical models for solving technical problems characterizing subharmonic oscillation processes in three-phase ferroresonance circuits and systems using the finite-difference method are expressed in the form of differential equations without appropriate initial conditions. Amathematical model of a system of equations representing subharmonic oscillations in ferroresonance connections depending on the value of the selected parameters in the field of change of any variable is considered.

Analysis of Subharmonic Oscillation and Slope Compensation for a Differential Boost Inverter

This paper focuses on the steady-behavior of a differential boost inverter used for generating a sinewave AC voltage in rural areas. The analysis of its dynamics will be performed using an accurate approach based on discrete time models and Floquet theory and adopting a quasi-static approximation. In particular, the undesired subharmonic oscillation exhibited by the inverter will be analyzed and its boundary in the parameter space will be predicted and delimited. Combining analytical expressions and computational procedures to determine the quasi-static duty cycle, subharmonic oscillation is accurately predicted. It is found that subharmonic oscillation takes place at critical values of the sinewave voltage reference cycle, which can cause distortion to the input current and degrade the harmonic content of the output voltage. The results provide useful information for the design of the boost inverter to avoid distortion caused by subharmonic oscillation. Namely, the minimum value of the compensation slope and the maximum proportional gain of the AC output voltage controller guaranteeing a pure sinewave voltage and clean inductor current during the entire AC cycle will be determined. Numerical simulations performed on the switched model implemented using PSIM© software confirm the theoretical predictions.

Design of Digital Control System for DC/DC Converter of On-Board Charger

Vehicle charging power supply is widely used because of its small size and portability. Aiming at the problems of slow dynamic response, subharmonic, oscillation and limited soft-switching range of phase-shifted full-bridge DC/DC converter, the paper proposed a modified PSFB converter by introducing clamp diodes at the primary side of the transformer to suppress voltage oscillation of the transformer’s secondary side. Also, digital peak current phase-shifting control and slope compensation are introduced to avoid subharmonic oscillation. Dynamic dead-time control technology introduced adjust the dead-time in different load ranges through the dead-time adjustment subroutine. Finally, an experimental platform of on-board charging phase-shifted full-bridge DC/DC converter is established. The experimental results show that the power supply eliminates subharmonic oscillation, achieves a wide range of soft-switching, improves the dynamic performance and antiinterference ability of the system, and optimizes the power efficiency.