Click to edit Master title style

• Click to edit Master text styles

– Second level

• Third level – Fourth level

» Fifth level

-

High Frequency Harmonics in Power System

Ramiar Alaei

University of Alberta

High frequency harmonic sources

Modeling Abstract

Power electronic devices have been increasingly used in low voltage networks during the last couple of decades. The increasing usage of this technology in the residential feeders has a large influence on the harmonic pollution level in the network. The focus of power quality studies has been on low-frequency harmonics up to about 2kHz. As a result, low frequency harmonics distortion is well understood and several related standards have been developed. However, there is lack of general understanding for higher frequency harmonics. Modern energy efficient equipment such as electronic ballast CFLs, LEDs, VFDs and PV systems often uses switching frequencies which is in the range of several kHz up to hundreds of kHz. This project is to conduct literature review on this issue in preparation for the research.

High frequency power electronic devices could be categorized based on their high-frequency side converter: front-end converter (mostly rectifier) and load-end converter.

Conclusion Requirements for harmonic control up to 2kHz in electrical power systems have been mentioned in IEEE 519-1992 standard. All the harmonic loads must meet these requirements by adding filters in their interface with the grid. However, There is lack of related standards for higher frequency harmonics which has allowed the rest products from the active switching to grow uncontrolled. Several measurements have been done in this frequency range, which shows high frequency harmonics tend to flow mainly between Neighbouring devices, not between the devices and the grid. The individual devices form a low-impedance path in this frequency range. As a result of this, the emission in this frequency range will show much less spread over other Customers than emission at lower frequencies. The impact of high-frequency distortion is likely to be limited to neighbouring equipment.

High Frequency Harmonics distortion of different LEDs with different manufacturers

Fig. 1 Block diagram of a switch-mode DC power supply

Fig. 2 Inside PC power supply

Fig. 3 IH cooker and electronic ballast CFL

Fig. 4 IGBT PWM rectifier/inverter system

Fig. 5 Grid connected PV system and Net Zero Energy Building

Several sets of measurements performed on the experimental setup of 48 high-frequency ballast CFLs.

a) Double Fourier Series (DFS)

Fig. 6 Comparison of 2-D and 3-D representation of modulation process of a PWM converter

b) Frequency coupling matrix (FCM).

Fig. 7 Schematic diagram of a VSC with its ac and dc stimuli

Experimental results

Fig. 8 Picture of the installation at Luleå Univ. of Technology

Fig. 10 Spectrogram of the current feeding one lamp

Fig. 11 Current spectrogram for 48 lamps

Fig. 11 High-frequency Emission from a 7W LED lamp

Fig. 12 High-frequency Emission from a 8W LED lamp

Fig. 12 Spectrum of the current taken by a CFL close to an induction cooker

- Neighboring effect

Fig. 9 Measurement of the background voltage