Research on multi-voltage self-adaptive Low Voltage Disconnect based on fuzzy PWM

Presently low voltage disconnect (LVD) only fits single power system and drives a given rated voltage contactor, which limits the use of LVD. Furthermore, the LVD would misoperate because the contactor coil voltage is changed when the LVD input bus voltage is floating. Based on the researches on the voltages self-adaptation of LVD, a progressive scheme for driving contactor through pulse width modulation (PWM) fuzzy controlled is proposed. The LVD identifies the outside condition, i.e., the input bus voltage and the contactorpsilas rated voltage. Then the microcontroller of the LVD outputs relevant PWM to drive the contactor. As the input bus voltage would be influenced by the environmental factors, fuzzy arithmetic is applied. The new LVD can work in both 24 V and 48 V systems, and can drive different rated contactors. The application of fuzzy arithmetic stabilizes the coil voltage and protects the contactor from coming to harm. A multi-voltage self-adaptive LVD based on PIC is developed, and related experiment is accomplished. The results of the experiment show that the scheme solves the interchanging of the LVDs through their testing and applying, and improves the self-adaptation and the stability of the system greatly.