C.M. Lundmark’s research while affiliated with Luleå University of Technology and other places

This paper presents the results from a number of measurements of the harmonic emission from installations that contain a large number of energy-efficient lamps. Two of the measurements concern the replacement of incandescent lamps with CFL and LED; the other measurement concerns an installation with up to 48 fluorescent lamps with high-frequency ballasts. The paper also contains a discussion on why the (total) power factor is not a good measure to quantify the performance of lamps or installations containing large numbers of lamps.

This paper presents different methods to describe voltage and current distortion in the frequency range 2 to 150 kHz. The time-frequency domain was shown to give additional information next to the time- and frequency-domain representations. Measurements of different devices and at different locations showed remnants of the switching frequency of the power electronics as well as lower frequency oscillations around the current zero crossing to be present in voltage and current. The voltage distortion is shown to vary a lot during the day and between locations.

This paper discusses the possibility that high common mode voltages occur in low-voltage distribution due to oscillations between parallel connected EMC-filters. It is shown that such oscillations may occur in the frequency range between 2 kHz to 150 kHz. Simulations and measurements have been carried out with different types of parallel connected power inlet filter, a common EMC Filter, and the circumstances giving oscillations have been highlighted.

This paper presents detailed measurements of currents flowing between modern electronic devices in a domestic environment. The results shown in this paper cover the frequency range 9 to 95 kHz, being the frequency band dedicated to power-line communication by network operators. Large differences exist between different devices, even when they are of the same type. It is also shown that the voltage waveform and the emission by other equipment have a significant impact on the current flowing between a device and the grid. An important conclusion from the measurements is that the high-frequency currents mainly flow between neighbouring devices.

A number of measurements have been performed on a full-scale electric model of a house to examine how end-user equipment affect the impedance in the frequency range 9-95 kHz. It is shown that the impedance level for the grid itself is fairly high and that it decreases when end-user equipment is connected. End-user equipment can be divided in to different categories, loads for which impedance is constant over time (for one cycle) and frequency and loads for which impedance varies over time, frequency or both. The measurements indicate that currents in high frequencies travel between loads at a much higher degree than between the load and the transformer.

This paper shows measurements of the harmonic emission by large groups of state-of-the-art computers measured at five different occasions from 2002 to 2008. The emission was measured during LAN-festivals where the participants use mainly the newest models of computer. This allows insight in the change in emission of computers during the last 6 years. The results from these measurements show that the distortion level generated by computers is decreasing while the power consumption does not show any significant change.

This paper addresses voltage distortion in the frequency range 2 to 9 kHz, above what is normally considered in harmonic studies. By extrapolating the voltage-distortion limits that exist in international standards for distortion up to 2 kHz, it is concluded that 0.5% of nominal voltage per 200-Hz band is a safe limit. This limit is next used to estimate the number of small generator units (1-10 kW) that can be connected to a low-voltage grid. It is concluded that in some cases the connection of one or just a few units already leads to a distortion level above the limit.

This paper discusses some consequences of developments in technologies that may impact the risk of electromagnetic interference and equipment damage despite the equipment complying with the tests according to the product standards. Examples of such technologies are: the change from analogue to digital communication, the fast increase in numbers of power converters having smart switching technology and the use of communication via the power system. The paper discusses upcoming sources of emission, uncertainties in emission level, and changing circumstances. It is shown that it is possible for equipment to remain below the emission limits while at the same time the disturbance level increases beyond what was intended by the standard document. The paper also proposes a framework for addressing the problems due to massive penetration of equipment injecting high-frequency harmonics

This paper discusses some recent developments that make the existing standards on the emission of high-frequency noise in power systems need to be reconsidered. It is shown that it is possible for an equipment to remain below the emission limits while at the same time the disturbance level increases beyond what was intended by the standard document. Further, the change from analog to digital communication and the use of communication via the power system, make that the permitted disturbance levels need to be reconsidered. This paper also contains an example of measured high-frequency noise and proposes a framework for re-coordination of emission and immunity levels.