Higher-order harmonics in the autonomous power supply system of a shortwave radio station: causes of occurrence and routes of spread

The range of shortwave radio communications can vary from tens to thousands of kilometers. Therefore, this type of communication is most promising for arctic, isolated, and remote areas. In the Russian Federation, such areas include the Far North. In terms of power supply, radio stations and shortwave radio communication systems have a highly variable load, with power consumption ranging from a few to hundreds of kilowatts. Given the isolation of northern territories from the Unified Energy System, power supply for radio stations and shortwave radio communication systems can only be provided by autonomous power supply systems. To achieve high-quality shortwave radio communications, autonomous power supply systems must ensure first-class reliability, high power quality indicators, and not be a source of electromagnetic interference.

Radio reception and transmission in the frequency range from 3 MHz to 30 MHz are highly dependent on natural noise (atmospheric and galactic). Station interference also impacts communication quality. Natural noise levels cannot be changed. Interference from other radio stations is technically difficult to eliminate. Therefore, even in the absence of interference from the power equipment of a shortwave radio communication system, an acceptable signal-to-noise ratio cannot always be achieved, especially in the Far North. Interference amplitudes from power equipment must be so small that they can be ignored in measurements and calculations. Therefore, a low level of electromagnetic interference is a mandatory requirement for autonomous power supply systems for radio stations and shortwave radio communication systems. Consideration should also be given to the impact of harmonic distortion on the level of the autonomous power supply system for radio equipment in the distribution network. Shortwave radio equipment is connected to the distribution network using pulsed power supplies. Switched-mode power supplies are sources of higher harmonics. Significant distortion of the sinusoidal waveform of the line voltage affects losses and contributes to the occurrence of resonance phenomena.

Thus, the issue of electromagnetic compatibility between the power equipment of an autonomous power supply system and radio equipment exists. Therefore, the aim of this study is to investigate the electromagnetic compatibility of the power equipment of an autonomous power supply system and shortwave radio equipment.

This paper demonstrates the relationship between the rapidly changing nature of the load and ferroresonance. Harmonic distortions of the line voltage under ferroresonance conditions and when connecting pulsed power supplies are assessed. According to the simulation results, at the connection point of the pulsed power supply, the voltage spectrum is represented by odd harmonics of the 3rd (7.3%), 5th (1.6%), 7th (3.2%), 9th (0.4%), 11th (2%), and 13th (0.2%) orders. Under ferroresonance, the voltage spectrum contains odd harmonics of the 3rd (33%), 5th (17%), 7th (10%), and 9th (7%) orders. The paper also describes the mechanism for the emission of higher harmonics from an autonomous power supply system to radio equipment and vice versa.

The research results can be used in the design of autonomous power supply systems with rapidly fluctuating loads, including the design of power supply systems for radio stations and shortwave radio communication systems.