Study on the operating modes of a power supply system: 6-10/0.4 kV, with linear and non-linear (rectifier) loads and a capacitor battery on the low-voltage side, was performed in the Multisim software package. We have found the dependences of the current’s higher harmonics, generated by a nonlinear load, on the level of compensation of reactive power and the power ratio of linear and nonlinear loads. The magnitude of the total current flowing through a capacitor battery in near resonance modes is evaluated. It has been established that non-periodic and oscillatory components appear in such modes in the current switching interval by the diodes, and the magnitudes of the current harmonics generated by the rectifier are significantly reduced compared to the absence of resonance modes. It is shown that the quality of the voltage does not correspond to the norms in resonance and near-resonance modes. A comparison of simulation results has been made between three-phase and simplified single-phase models.