Stabilization of the DC-link for inverters with PDM power control

This paper analyses the behaviour of the DC-link of a high power (50 kW), high frequency (150 kHz) voltage fed inverter with a series resonant load circuit for industrial induction heating applications which is characterized by a full bridge inverter with a power control based on pulse density modulation (PDM). The operation of this power control strategy can cause large oscillations of the voltage at the input of the inverter due to its discontinuous operation and the inductances and the capacitances of the circuit. A design method based on simulation results is presented. The results are verified experimentally using a prototype for induction hardening applications.