Toomas Vinnal

Analysis of power consumption and losses in relation to supply voltage levels

This paper is focused on the effects of active and reactive power consumption and losses depending on voltage level variations around the normal (rated) voltage level. Supply voltage variations from rated voltage affect both power consumption and losses in the network. Focus is put on load response to the voltage change, while motor-type and mixed residential load is observed. Relations between voltage variation and load power consumption are suggested. Comparisons based on literature as well as classical theory and on-site measurements are presented.

Harmonic load of residential distribution network — Case study monitoring results

The non-linear loads in domestic applications are becoming more common as the power electronic converters are being implemented more widely. This can lead to more significant load current distortions. This paper is presenting a case study results to describe the expected harmonic distortions and to provide models to estimate their magnitudes during day for different times of year. The results presented are from a residential area low-voltage network, which is also providing the heating power for the households. The discussion is presented about the daily harmonic current profiles, which are presented to vary to great extent, harmonic to harmonic and for the different times of the year. The daily profiles of the harmonics with more stable characteristics are described using daily patters trend models.

Analyses of supply voltage quality, power consumption and losses affected by shunt capacitors for power factor correction

This paper is focused on active power consumption and losses in industrial and commercial facilities, depending upon supply voltage quality parameters. The shunt capacitors for power factor correction affect directly supply voltage level and harmonic distortions of supply voltage and current and hence affect power losses in industrial facilities, particularly in induction motors. In the paper practical measurement methods are described for estimating power losses when power factor correction capacitors are used. The impact of capacitors upon supply voltage level and harmonic distortions is discussed. Measurement results of voltage and current harmonics spectrum in industrial 0,4 kV power systems are shown.

New theoretical approach to input current shaping in ac-dc power converters

A new method for an input current waveform correction in typical power converters is described. It assumes an implementation of the so-called virtual transformer with a fast-changing voltage ratio. Theory and calculations are presented to confirm the method validity. Practical implementation is left out of the scope of the given paper due to size limitations.

Effects of PV microgeneration on rural LV network voltage quality

Increase in photovoltaic (PV) systems integrated into low-voltage (LV) distribution networks has created a pressing need for analysis of the effects of these systems on power quality and supply reliability. The main aim of this study was to analyze the effects of small-scale PV-system power generation on voltage quality in a rural LV distribution network. In the analysis based on real field measurements, the numerical and graphical methods of data analysis were used. Thus, correlations between PV-system power (P(pv)) generation and voltage quality parameters in the LV-grid were examined.

Effects of PV microgeneration on rural LV network voltage quality - harmonics and unbalance

The growing demand for utilization of solar energy and thus increasing number of photovoltaic (PV) systems installed in low voltage (LV) distribution networks has given rise to the studies focusing on the effects of these systems on power quality (PQ) and supply reliability. The aim of this study is to analyze the effects of small-scale PV-system power (P(PV)) generation on voltage quality in a rural LV distribution network in Estonia. In the analysis, which is based on real field measurements, the numerical and graphical methods were used. The correlations between P(PV) generation and the following voltage quality parameters are shown: voltage total harmonic distortion (THDU) and individual odd harmonic components up to order 19 and voltage unbalance.

Supply voltage level optimization in industrial low voltage networks

This paper is focused on measurement and analysis of supply voltage level in low voltage industrial power systems in Estonia. A practical method for analysis of supply voltage quality parameters implementing stochastic theory is discussed. Measurement results of supply voltage quality parameters - voltage magnitude, voltage level and voltage sags in industrial 0.4 kV power systems of Estonia are shown. The impact of shunt capacitors for power factor correction upon supply voltage level is discussed.