TRANSIENT PROCESS IN REACTIVE POWER COMPENSATION UNIT WITH SERIES CONNECTION OF CAPACITORS WHEN ONE OF THEM IS DISCONNECTED

When designing switchable installations of transverse capacitive reactive power compensation in AC traction networks with intelligent control systems, it is necessary to calculate both steady-state and transient processes in them to increase the operational reliability of compensating installations. It is shown that in some cases, the calculation using the well-known classical method gives results that differ from the actual values. As an example, the transient process in RC circuit connected to alternating voltage (when the circuit parameters change) is considered. This is due to the fact that when changing the traction load, it is necessary to change the capacity of the compensating installation by shunting and disconnecting one of the two series-connected sections of capacitors. It is shown that when calculating transients in electrical circuits with series capacitors switching on, it is necessary to use the classical calculation method with caution when one of the capacitors is disconnected. In this case, in steady-state mode, a constant component may be present on the capacitors, which increases the voltage on the capacitors. According to the remaining portion of the circuit, the two series-connected capacitors behave as one equivalent capacitor without a constant component. The constant components on the equivalent capacitor add up to zero. However, they increase the voltage on each of the capacitors. To obtain true voltage values on capacitors, you should use the operator method or the numerical method for solving differential equations. The conducted research is of practical importance, because in modern electrical installations thyristor switches are used as switching equipment, in which the capacitor is disconnected at the maximum voltage on the operating capacitor. In this case, long-term overvoltages exceeding the expected values are possible, in the limit up to double amplitude value of the supply voltage.

Authors: A. S. Serebryakov, V. L. Osokin, D. E. Dulepov

Direction: Electrical Engineering

Keywords: Reactive power compensation unit, AC traction network, numerical method for solving differential equations, classical method for calculating transients, Runge–Kutta method, overvoltage

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