Analysis of Dynamic Characteristics of the Inverter Operating on a Complex Load

Abstract

A simulation model of a converter with soft switching of transistors has been created. New calculation methods and means of measuring the equivalent frequency characteristics of converting devices with negative feedback to the problems of stability analysis have been applied. A comparative analysis of the calculated frequency characteristics of the converter in the normal operation mode with the characteristics of its linear model is presented. The features of calculating the equivalent frequency characteristics of the loop amplification of key devices are considered. It is noted that it is the equivalent frequency characteristics of the loop amplification that describe the relationship of frequency properties with the dynamics of voltage converters with pulse-width modulation and make it possible to reliably determine the real stability margins, predict the generation modes and open up the possibility of obtaining maximum negative feedback in a given frequency band of key devices. The non-minimal phase properties of the converter significantly complicate the achievement of high-quality stabilization of the output current (stabilization coefficient) of pulse stabilizers using only the deflection control principle. A successful solution to the problem is provided by the use of the principle of combined control. Compensation of the disturbance effect (changes in the supply voltage) gives a much better result than countering it through the feedback loop. It is quite realistic to exclude the influence of the input voltage u ( t ) on the output current i 2 in a static mode ( u =const) and in the absence of a negative feedback loop, which provides  for u =const in a steady state, and to provide better dynamic properties of the converter. The influence of the nonlinear properties of pulse width modulation on stability is manifested in the considered characteristics in the form of an additional phase shift and resonant bursts in the vicinity of the clock frequency subharmonics. Additional feedbacks introduced into the control loop make it possible to solve synthesis problems using the most simple technical means