Dynamics of scanning converters with sampling of instantaneous values of the control signal and various modulation patterns

Abstract

Design principles and timing waveform diagrams of scanning converters (SCs) with sampling of instantaneous values of control signals and various patterns of pulse-width modulation used in analog and digital systems for control of valve converters (VCs) are considered. SCs with pulse-width modulation of the first, second and third kinds are considered. Their block diagrams and timing waveforms are provided. The method of analysis of the dynamic characteristics of SCs is given. On the basis of obtained transcendental equations and their solutions, the dynamic characteristics analysis of different classes of SCs by a method of the space of the dynamic state of the object under the impact of the harmonic signal of interference in a wide frequency range is given., The concept of an average statistical deviation of the duty factor of pulses and frequency of carrier waves in the space of the dynamic state of the object is introduced as a criterion of comparative estimation of dynamic characteristics of SCs. It is shown that, for an SC with sampling of instantaneous control signal values, only pulse-width modulation of the second kind provides the lowest level of errors in the frequency field of slow discretization; therefore, it is advisable to use this modulation pattern in systems for control of VC. When operating a dynamic signal “in the small,” pulse-width modulation of the second and third kinds appears to be a variety of frequency-pulse-width modulation, since it is characterized by deviation of the frequency of carrier waves from a set value.