Thyristors

All the thyristor unIts when are in conduction produces power loss that dissipate inside cabinet in term of heating.
Due to this fact the internal temperature of cabinet is higher than ambient temperature.
Here you can find some solution by CD Automation team

A microcomputer, the Altair 8800, was used to generate the gating signals for a single-phase-to-single-phase cycloconverter, keeping the same firing angle on all thyristors for a particular output voltage and frequency. The power circuit and the required interface circuits were built. Output waveforms for different firing angles and output frequencies were obtained.

This paper proposes a new configuration to help a GTO to achieve unity turn-off gain and snubberless turn-off capability by utilizing a series connected discrete diode. The maximum turn-off gate voltage, which is crucial for realizing a high commutation di/dt in the GTO gate loop, can be increased from about 20 V of a GTO's gate-cathode breakdown to a voltage

The main aim of this work is to damp out power system oscillations, which has been recognized as one of the major concerns in power system operation. In a Static Synchronous Series Co mpensator (SSSC), a controllable A C voltage is generated by a voltage-source converter. There are two control channels for controlling the magnitude and phase of the voltage. This work describes the damping of power oscillations by static synchronous series compensator (SSSC) based damping controllers. The advantage of this approach is that it can handle the nonlinearit ies, at the same time it is faster than other conventional controllers and it improve the reactive power of the system. Simu lation studies will be carried out in Matlab/Simu link environ ment to evaluate the effectiveness of the proposed Static synchronous series compensator (SSSC) of mu lti-area power system. Results will show that the proposed SSSC based damping controllers improve the dampin g performance of the in the event of a major d isturbance.

Series compensation of transmission lines using fixed series capacitors can cause sub-synchronous resonance (SSR) between electrical and mechanical systems. This phenomenon leads to severe damages to turbine generator shafts. Thyristor controlled series compensator (TCSC) is one of the FACTS devices which can be utilized to damp electromechanical and sub-synchronous oscillations. This device can perform flexible series compensation and SSR damping. The effect of different parameters of the TCSC is studied using complex torque coefficient method. Open loop and closed-loop constant current and constant power control methods are simulated using PSCAD/EMTDC software package. First IEEE benchmark model for sub-synchronous resonance studies and a complete model of TCSC is used to analyze the effect of different parameters and control structure on the SSR damping capability of the TCSC.

A method for determining parameters for a two-transistor SCR model from SCR specification sheet data developed by Hu and Ki (1979) for use with the CAD program SPICE2 was examined. The model was found to need improvement in order to simulate the SCR turn-off transient in an inductive circuit. An improved model was then developed for SPICE2 which was demonstrated to perform satisfactorily through simulation of AC resonant charging circuits having one or two SCR's. The original and the modified Hu-Ki models are presented together with the simulation results.