Abstract
The object of the study is a three-phase frequency converter (FC) with an uncontrolled rectifier and pulse-width modulation (PWM) of the output voltage, used for frequency regulation of asynchronous motors (AM). The problem to be solved is the improve the energy efficiency of the electric drive and the accuracy of speed control while reducing harmonic distortions of voltage and current, which is especially important for industrial installations operating in continuous or alternating mode. In the work in the Mathcad environment, a mathematical model of the FC was developed, including a power circuit, an algorithm for generating PWM and dependencies for calculating the power factor, efficiency and total harmonic distortion (THD). The model allows performing parametric studies of the effect of frequency and amplitude of the output voltage on the energy indicators of the drive with a high degree of detail. The simulation results showed that the optimized sinusoidal PWM algorithm with ordered switching distribution reduces THD by 18–22% and increases the power factor to 0.94–0.96 due to a more uniform harmonic spectrum distribution and reduced reactive losses. The advantage of the proposed model is the ability to adapt to various AM operating modes and load conditions without changing the structure of the power section, which expands its practical application. The obtained results can be used in the design and modernization of industrial electric drive systems, pump and fan units, as well as in automated complexes where economical, reliable and high-precision speed control is required. It further enables sensitivity checks and controller tuning to evaluate PWM strategies under realistic limit