This paper presents the calculation of non-stationary non-sinusoidal mode of the power supply system (PSS) under the condition of current resonance (parallel resonance). Evaluation of the need for higher harmonics (HH) filtering was carried out. To achieve this, measurements of the actual level of HH and other unified power quality indexes were conducted, and oscillograms of the network mode parameters and HH spectrum were constructed. The measurement of unified power quality indexes was carried out with certified and calibrated power quality analyzers Metrel 2792A. These instruments satisfy the effective world standards on power quality and other reference documentation. Resonance frequencies where resonance modes emergence is possible were determined by calculation. Maximum overvoltage ratios for different points of the examined PSS were also determined.

The paper presents the use of wavelet packet transform for a non-sinusoidal mode analysis of power supply systems taking into account the actual heating of conducting parts. Higher harmonics cause additional heating of conducting parts, and consequently, there is an increase in power and energy losses. The range of resistance variation in the operating temperature range can substantially affect the estimated value of losses. The accounting of actual heating will allow one to specify the feasibility study in selecting and implementing measures on higher harmonics filtering in power supply systems. The wavelet packet transform has a number of advantages compared to the Fourier transform in analyzing non-sinusoidal modes. The use of the wavelet packet transform is proposed in this paper for analyzing non-stationary modes of power supply systems.

This paper presents the calculation of a nonstationary non-sinusoidal mode of the power supply system (PSS)under the condition of current resonance (parallel resonance). The evaluation of the need for higher harmonics (HH)filtering was carried out. To achieve this, measurements of the actual level of HH and other unified power quality indexes were conducted, and oscillograms of the network mode parameters and HH spectrum were constructed. The measurement of unified power quality indexes was carried out with certified and calibrated power quality analyzers Fluke 435 and Metrel 2792A. These instruments satisfy the effective world standards on power quality and other reference documentation. Resonance frequencies where the current resonance mode execution is possible were determined by means of calculation. Maximum overvoltage ratios for different points of the examined PSS were also determined.

The article describes the simulation of the current resonance that occurs in the power supply system when the degree of reactive power compensation is varied in non-stationary operation modes and the presence of electric receivers having a nonlinear voltagecurrent characteristic. In addition to simulating the mode of parallel resonance arising at frequencies close to the frequencies of higher harmonics, the proposed algorithm determines all possible resonance frequencies at which the parallel resonance condition under different assumptions can be satisfied, as well as the relative error of calculation for different cases: when all the components of complex impedances are taken into account; without taking into account the active components of the resistance; taking into account the active component of the resistance of the transformer, but not taking into account the resistance of the loads; without taking into account the active component of the resistance of the transformer and without taking into account the resistance of the loads. The purpose of the proposed work is to show how the accounting (non-accounting) of the components of complex resistances affects the results of determining the resonant frequencies.