Maximum Power Factor Tracking Technique for LCC-Capacitor Charging Power Supply Through Variable DC Link Voltage

This article proposes a maximum power factor tracking (MPFT) technique for the LCC resonant converter which functions as a capacitor charging power supply. The proposed MPFT technique is achieved through variable dc-link voltage whose reference value can be adjusted in real time for the maximum power factor. By means of the proposed method, the dc-link voltage follows the output capacitor voltage to minimize the turn-off current of mosfets, thereby reducing the turn-off switching loss. Additionally, this technique reduces the circulating current, which in turn decreases the instantaneous reactive power in the resonant tank. In comparison with the conventional constant-current (CC) charging and constant-power (CP) charging strategies without MPFT, the proposed CC charging with MPFT (CC-MPFT) and CP charging with MPFT (CP-MPFT) both exhibit great efficiency improvement. In CC-MPFT, the efficiency can be improved by up to 26.84% under light load condition. In CP-MPFT, the efficiency can be increased by up to 11.63% under light load condition and 2.66% under heavy load condition.