Magnitude In Series Research Articles

Phase Angle Control Based Three-phase DVR with Power Factor Correction at Point of Common Coupling

This paper investigates the ability of correcting the power factor at the point of common coupling (PCC) of the source side using dynamic voltage restorer (DVR). By applying the phase angle control (PAC) method, the DVR compensating voltage will be injected with a specific phase angle and magnitude in series with the transmission line, which leads to a power factor angle shift of the resultant load voltage. As a result, the source voltage is always in phase with the source current under different load conditions, which means that the power factor correction is achieved at the PCC of the source side. A laboratorial prototype of the DVR is utilized to verify the proposed control algorithm. The experimental results validate that an approximate unity power factor can be maintained at the source side.

A Transistor Trigger Circuit

Analysis of the characteristic curves of transistors shows that the negative resistance necessary to the functioning of a trigger circuit exists in the base circuit of a transistor. A trigger circuit may therefore be formed by inserting a resistance of proper magnitude in series with the base. Such a circuit has the advantages over vacuum-tube circuits of much shorter triggering time, simplicity, small size, absence of filament power supply, and low operating voltage. The rise and fall times of the output voltage are less than 0.1 microsecond and the circuit is stable from zero triggering frequency up to the maximum frequency used. Although the circuit has been tested only up to 1 Mc, an upper limit of at least 10 Mc is probable. An output voltage of 5 or 6 volts may be readily obtained. Like other types of trigger circuit, the transistor circuit may be converted into a relaxation oscillator or a pulse generator.