Statistical summation of the harmonic currents produced by a large number of single phase variable speed air conditioners: a study of three specific designs

Abstract

The Variable Speed Air Conditioner (VSAC) is a large domestic distorting load. We investigate the impact of a large number of VSACs on domestic harmonic levels. We present a general method to build a harmonic numerical model of a passive filtered rectifier supplied by a distorted voltage, a statistical method to assess the total harmonic currents produced by a large number of units running at various power levels and supplied by various distorted voltages. These two methods are applied to a rectifier used by many VSACs. We also present results for two other rectifiers.

Time-varying harmonics. II. Harmonic summation and propagation

“…This is known as the central limit theorem which states that the pdf of the sum approaches a normal distribution regardless of the distributions of the individual variables, as long as the number of variables is sufficiently large and none is dominant. If the above conditions are satisfied, the pdf of the sum of the -projections in (12) is approximated by (16) where the mean value and variance of this sum are respectively given by and .…”

“…Reference [15] examined the diversity of a set computer loads due to difference in phase angles. Finally, [16] studied a set of variable-speed air conditioners with variable duty cycle. The main conclusion of the above studies is that there is often significant harmonic cancellation and that the worst case (i.e., arithmetic sum) is often too conservative, sometimes higher than the expected value by an order of magnitude.…”

Statistical summation of the harmonic currents produced by a large number of single phase variable speed air conditioners: a study of three specific designs

“…This Section is a generalization of the method presented in [4]. The method can be applied to passive filter rectifiers whose dimension is lower or equal to four, such as the one presented in Fig.…”

“…We chose a plausible Probability Distribution Function (PDF) of The voltage wave-shape is derived from the following expression: (4) with and , and where is a 60% distorted capacitorm filtered diode bridge rectifier current. Variable is adjusted so that has the desired THDV.…”

Harmonics monitoring survey on office LV appliances

“…The power suppliers, equipping such appliances, are non-linear (NL) loads, with relevant impact on power quality (PQ). For these reasons, since '90s many studies have been addressed to this problem, generally assessed through simulations for estimating the mutual influence between NL loads and the system [1]- [12]. For every approach to the problem, a monitoring activity of NL equipment harmonic absorption has always been a preliminary step for correctly characterizing NL load impact on the distribution grid [13]- [17].…”