Boost type active filter system and boost type active filter control device

摘要

The present invention relates to a technical field for controlling the DC output voltage of a boosting active filter constant. When a load changes from a rated condition to a light load or no-load condition and the output voltage rises, a conventional active filter control device externally forces the active filter to stop and restart to suppress the voltage rise. In this process, an excessive inrush current occurs and the reactor produces abnormal sound. In addition, the conventional technique cannot be adapted to the PAM control. Accordingly, in the present invention, first and second resistors (36), (37) and a control power supply (38) are provided between an output terminal (51) of a main circuit (100) and ground, and the voltage at a node (c) is inputted to one input end of a first differential amplifier (14) and one input end of a hysteresis comparator (20). The output of the comparator (20) is connected to an output end of a second differential amplifier (16) through a signal line (70). The voltage at the node (c) is kept equal to a reference voltage Es even if the output voltage set value (vos) is changed by changing the control voltage (Vctr1) of the power supply (38), thus providing an overvoltage protection function which can follow variation of the output voltage set value (vos). The active filter of the invention can be applied to a load such as a PAM-controlled inverter, AC servomotor, etc. IMAGE