Abstract: An automatic compensation method was presented based on adaptive capacitance regulation

technology and the principle of controlling capacitor charging and discharging voltage. Based on the turn off ability of the self-turn off device，a switch circuit composed of two self-turning off devices connected in reverse parallel with diodes was connected in reverse parallel. Through the logic drive circuit，pulse width modulation circuit，zero point detection circuit and power factor detection circuit，the on-off of the self-turning off device in the switch circuit was controlled to control the charging and discharging voltage of the compensation capacitor，and then the capacitor compensation current was controlled. It was equivalent to realize the function of the adjustable capacitor，and the power factor compensation of the load was automatically controlled. The principle of the circuit，the working process，and the selection of the main device parameters were analyzed and elaborated though experimental data. The power factor automatic compensation control device of the self-turning off device manufactured by this method has the characteristics of simple structure，small volume and high efficiency，and can automatically carry out random power factor compensation for the electric load on site.

      Key words: capacitor；automatic compensation；self-turn off device；zero switch