Supraharmonics emission from LED lamps: A reduction proposal based on random pulse-width modulation

There is an outstanding concern from the international standard-setting community about harmonics distortion in the frequency range 2-150 kHz, referred to as supraharmonics. Power electronics has established as a ubiquitous technology, which plays a linchpin role in almost any electrical systems. The classical deterministic pulse-width modulation strategy, entailing at reducing low-frequency harmonics emission (<2 kHz) in power converters, in a sense, bring them to move at the switching frequency and its multiple, in the kilohertz range. The amplitude of spectral components is the main concern when studying electromagnetic interference from active power factor correction stages, included in state-of-the-art LED drivers. Supraharmonics are nowadays the origin of numerous problems in electrical networks. The standardization bodies are presently updating the compatibility limits in the frequency range from 2 to 150 kHz. Supraharmonics behave differently from (lower frequency) harmonics, as reported in the literature. Fortunately, as will be demonstrated in this paper, it is possible to undertake this issue, from the very beginning, by leveraging technologies like random pulse-width modulation. An experimental system based on digitally controlled LED driver has been set up to evaluate the different methods. The algorithms have been implemented on a compactRIO controller incorporating an FPGA and a real-time processor.