A Rational Frequency Tracking Method for Phase-Shift Migration Inverter in Ultrasonic Power Control
摘要
The aim of this paper is to find a method for tracking the resonance point of an ultrasonic transducer driven by a phase-shift PWM inverter operating in a “phase-shift + operating frequency control” scheme, as well as to overcome the drawback of IZL (Integration Zero Loop) where optimal frequency tracking is impossible when the phase-shift PWM inverter outputs the maximum power. The minimum admittance tracking system (MATS) proposed in this paper consists of a matching circuit with parameters determined by MATLAB simulation and performs experiments with the desired power to determine the LF so that the phase-shift PWM inverter operates in a stable operating state where shock currents are not generated by a small increase in the parameter LF of the L–C matching circuit. The MATS, which is the optimal frequency tracking method we proposed, overcame the drawback of IZL, where the optimal frequency tracking was not possible when the phase-shift PWM inverter outputs the maximum power. Moreover, it prevents the generation of shock currents that occurred on the right-branch of the inverter even when power control is performed at the resonant frequency of the load and allows the inverter to operate in a steady state.