Synchronised Linear Ramp-Pulse Based Triggering Pulse Generation ON/OFF Control for Solid-State Switches: Capacitor Switching Applications K.SUBRAMANIAN 1 AND K.K.RAY Power Electronics and Drives Division Vellore Institute of Technology University Vellore, Tamil Nadu, 632 014 INDIA 1 Email id: ksubramanian@vit.ac.in Abstract: -This paper describes a newly developed triggering circuit, has been use to turn on and off the solid- state switches, such as TRIAC switched capacitors applications. A linear ramp signal based synchronization technique has been propose and implemented successfully, for the capacitor switching operation of a simple power system. This scheme enables the firing circuit to adjust itself against any phase and/or sequence alterations. This feature leads to elimination of the phase locked-loop (PLL) control, are commonly used to synchronize the pulse generations with respect to the system the supply frequency. Those pulses are, to control the converter / inverter operation of an industrial drives and the FACTS controllers also. The proposed circuit has been constructing and tested experimentally in the laboratory. The simulation work completed using Or CARD software. The result shows a good agreement with the theoretical waveforms. Key Words: - linear ramp signal, synchronization, capacitor switching 1 Introduction In electrical drives applications either in industries or in elsewhere, induction motors are widely used. Therefore, the system has a low power factor. The shunt-connected capacitors are widely used to improve the power factor. In addition to that, shunt capacitors have been to regulate the voltage of the transmission line at the receiving end. In earlier days, mechanical switches used to connect the capacitor in aforementioned applications. After the development of power semiconductor devices with higher power handling capabilities and current ratings, solid-state switches (like thyristors, IGBT, GTO, MOSFET, TRIAC etc..) are used instead of mechanical switches, because of its compactness and easy to control. Static power conversion manufacturers have developed a variety of thyristor firing circuits based on commercially available discrete and integrated circuits. Ainsworth [1] has presented a phase locked oscillator control system for thyristor-controlled reactor. Frank J. Bourbeau [2] developed, LSI based three-phase thyristor firing circuit insensitivity to frequency and direction of phase rotation with PLL circuit. A microprocessor based firing circuit for thyristors working under a three-phase variable frequency supply has been suggest and implemented by H. M. EL Bolok [3]. In his work, zero crossing has been detected and to fix the frequency reference. L.S.Torseng [4] discussed the reactive power compensation of a power system by thyristor switched capacitors (TSC) and thyristor controlled reactor (TCR) schemes. In view of capacitor switching operation, T.J.E Miller [5] and N. H. Hingorani et al [6] have discussed the constraints and control strategy. In case of stand-alone power generators, such as self-excited induction generator, excitation control says, either adding or removing the capacitor to the stator windings of the generators. T.A. Ahemed et al [7] discussed the terminal voltage regulation of a three-phase capacitor excited induction generator using switched capacitor and fixed capacitor- thyristor controlled reactor with zero crossing technique. In single-phase generator, also the same technique has been implemented [8]. Ebenezer Prates Da Silveira et al. [9] describe the low cost optical TRIAC with a built in zero-crossing function based voltage regulation of three phase induction motor with direct on line staring. However, aforementioned applications need a separate control, to synchronize the frequency and pulse generations. The aim of this work, propose a new technique, can be automatically synchronised with supply frequency variations. Analog and digital integrated circuit based triggering pulse generation circuit (with less number of component) has been WSEAS TRANSACTIONS on POWER SYSTEMS K. Subramanian, K. K. Ray E-ISSN: 2224-350X 45 Issue 2, Volume 7, April 2012