Control of the output voltage of a controlled rectifier based on a transformer with rotating magnetic field

Abstract

A new control method for a rectifier based on a transformer with a rotating magnetic field (TRMF) containing an even number of sections of circular winding (CW), which makes it possible to double the number of ripples of rectified voltage in the supply-voltage period, is considered. It leads to a reduction in the ripple amplitude and improves the quality of rectified voltage. The geometrical similarity of the CW of a TRMF making it possible to implement the new control method is analyzed. Switching algorithms of power switches for the classical and new control methods for any quantity of an even number of CW sections are presented. As an example, a switching queue of power switches for a CW with ten sections is considered. The output-voltage shapes for different depths of control are shown. The calculating procedure of the control characteristic for the classical and new control methods, as well as corresponding diagrams, are presented. For the presented example with ten sections of CW, the efficiency of the new control method was evaluated and the dependences of the voltage-ripple ratio on the RMS of rectified voltage are presented. A comparative analysis of the number of ripples for different quantity of CW sections was conducted, and the harmonic composition of output voltage spectrum for the example under consideration is determined. It has been concluded that, in the case of using the new control method for achieving the desired quality of rectified voltage, the number of CW sections may be halved compared with the classical control method, which will simplify the manufacture of a transformer magnetic conductor, halve the number of pairs of power switches switching the CW taps, and decrease the mass, dimension, and cost factors of a semiconductor switch and the TRFM itself as a whole. Using the new control method makes it possible to make a controlled rectifier with an even number of sections of a CW transformer almost as efficient as using a transformer with an uneven number of CW sections and the classical control method. The new control method ensures the fulfillment of the requirements for the available value of the ripple ratio of the output voltage of a controlled rectifier based on a transformer with a rotating magnetic field set out by State Standard YuST 13109-97 at a lower RMS of rectified voltage.