METHODS OF REGULATING SINGLE-PHASE RECTIFIERS BASED ON FULLY CONTROLLED SEMICONDUCTOR VALVES

Abstract

Three methods are considered for regulating the output rectified voltage of single-phase controlled full-wave rectifiers (bridge and mid-point) with a transformer input based on fully controlled semiconductor valves (blocking thyristor, series-connected transistor and diode) with one-way conductivity, operating on purely active and active-inductive loads, which cannot be implemented in rectifiers using incompletely controlled semiconductor valves (thyristors).

Since the curves of the output voltages and input currents of the controlled rectifiers are non-sinusoidal periodic functions, taking into account the generally accepted assumptions (current commutation in the valves is instantaneous, active losses in all circuit elements are zero, the current at the rectifier output with an active-inductive load is ideally smoothed, the magnetizing current of the transformer is zero, the transformation ratio is 1, the single-phase voltage at the rectifier input is sinusoidal) based on the methods of harmonic analysis and switching (commutation) functions, mathematical descriptions of the output rectified voltages are given depending on the control (regulation) angle in the form of trigonometric Fourier series, pulsation coefficients, energy indicators (coefficients of the shift of the first harmonic of the input current relative to the input voltage, power and distortion of the input current) when operating on active and active-inductive loads by applying on fully controlled semiconductor valves. Since the rectifier schemes under consideration have different control characteristics and different limit angles of control, the relative values of the average rectified voltage are not taken as independent variables in the dependences of the coefficients, which is equally suitable for all schemes and their comparative quantitative assessment.

To complete the comparative evaluation, mathematical descriptions of the output rectified voltages and the aforementioned coefficients of rectifiers based on non-turn-off thyristors are also provided.

Based on a comparative assessment, it is shown that the use of fully controlled semiconductor valves in rectifiers instead of conventional thyristors makes it possible to improve energy performance and reduce pulsation factors.