Measurement of Electric Power Quantities and Efficiency in Nonsinusoidal Conditions

The presence of harmonics introduces disturbances and losses in electrical systems that cause malfunctions and inefficiencies. The harmonic emission levels are progressively increasing because of the presence of non linear loads and distributed generation from renewable energy resources. The assessment of the effects on electrical systems is an important goal for modern industries, where the disturbances cause both damages and inefficiencies. According to the Leonardo Power Quality Initiative (LPQI) and to the research by the Electric Power Research Institute (EPRI), poor power quality is estimated to cost the European economy up to €150 billion annually and the U.S. sees losses ranging from $119 billion to $188 billion, when the 80 percent of power-quality disturbances are generated within a facility. These malfunctions and inefficiencies can be reduced with the use of filtering systems, such as series passive filter. To evaluate the impact of filters on disturbances and inefficiencies, several methods were presented, based on the definitions and indications contained in the standards such as the IEEE std 1459. To carry out the necessary measures to understand the effectiveness of the filters, it is possible to use measurements in the time domain which, carried out for limited periods, but with many repetitions, can offer a valid response to the achieved efficiency. Therefore, to correctly evaluate all the values of the harmonic components, as required by the IEEE 1459, it is necessary to carry out very detailed and complex measures, which in the industrial field are difficult to achieve. In these cases, the IEEE 1459 proposes to measure the values associated with the various power components through some approximations that can lead to errors of the order of a few percentage points. Since the effects of a filter can lead to measurements comparable with the approximations introduced by the IEEE 1459, it was necessary to find a new operating mode in order to obtain the requested quantities.In this paper, a method for evaluating the efficiency obtained with the use of a passive filter is presented.