Hardware Development And Software Applications Of Low Voltage Intelligent Capacitor

The low voltage intelligent capacitor was deeply studied in this paper, consisting of using magnetic latching relay synchronous switching technology, research on an adaptive zero-crossing switching technology for intelligent power capacitor based on closed loop control of zero voltage, control hardware circuit design of intelligent capacitor, implementation of intelligent capacitor software and its control strategy, realization of intelligent capacitor monitoring system and analysis of the relevant test of intelligent capacitor, introduction of the intelligent capacitor products.By comparing and analyzing the advantages and disadvantages of several common switching capacitor technologies, a synchronous switch based on magnetic latching relay which could switch capacitor without surge was used. By controlling the phase angle of opening and closing of the magnetic latching relay, the capacitor could be input at the time of zero voltage. Compared to the bidirectional thyristor switched capacitor technology, synchronous switching capacitor technology has the advantages of stable performance and "zero" switching loss, and compared to composite switch capacitor technology it has the advantages of simple structure and low cost.According to the problem of electromagnetic switch’s poor accuracy of synchronous control caused by the switching time dispersion, an adaptive zero voltage closed loop control method based on zero crossing switching control was presented in this paper. By calculating and feedback the time difference between opening time of contact switch(magnetic latching relay) and zero voltage time, the influence of external parameters, grid environment fluctuation and the difference of contact switch, can be effectively avoided by this method, and the accuracy of synchronous switch can be increased by this method, further, the inrush current and overvoltage can be reduced.According to the need of reactive power compensation in different occasions, selection and design of intelligent capacitor element were analyzed in this paper. According to the characteristics of synchronous switch and adaptive control method, zero crossing detection circuit, drive circuit of the magnetic latching relay and switching time feedback circuit were designed in this paper. Adaptive zero crossing switching algorithm and cyclic switching algorithm were studied too. Intelligent capacitor monitoring system was designed in this paper.Finally, the reliability of the magnetic latching relay switching capacitor was verified by the aging test of intelligent capacitor. The effect of switching capacitor technology "surge-free" by using the technology of adaptive zero crossing switching based on zero voltage closed loop control was verified through the test of intelligent capacitor "surge-free" switching; the long-term stable operation of intelligent capacitor was tested by intelligent capacitor running test.