Clean Power

Ukrainian (UA)English (United Kingdom)

The National Academy of Sciences of Ukraine

The Institute of Electrodynamics

About Institute



V.S. Kozlov
SHEE “Kryvyi Rih National University”,
Vitalij Matusevych st., 11, Kryvyj Rig, 50027, Ukraine

The article describes the synchronization issues of parallel generator in weak supply grids. The proposed synchronization system is based on the Discrete Fourier Transform method (DFT). For three-phase systems it is proposed to implement DFT for first voltage harmonic of positive sequence. The article describes the way of DFT synchronization method modernization. The essence is to add to a system the linear synchronization DFT loop of non-standard frequency. It was proven minor error of proposed modernization method. The proposed addition increases the stability of synchronization system when the phase step of frequency derivations is occurred. The article includes the modeling results of generator working in weak grid. According to these results it was found the non-linear dependence of power losses in supply grid in case of wrong synchronization. References 6, figures 3.
Key words: Smart grid, inverter, Fourier Transform, synchronization, PLL.

1. Malyshkov G.M. Parallel operation of inverters. Prakticheskaya silovaya elektronika. 2009. No 3 (35). P. 3-8. (Rus)
2. Trudnev S.Yu. Investigation of a parallel work of PWM inverter and single-phase network. Vestnik Gosudarstvennogo universiteta morskogo i rechnogo flota. 2014. No 6. P. 60-66. (Rus)
3. Bauer J., Lettl J. Solar power station output inverter control design. Radioengineering. 2011. Vol. 20, No 1. P. 258-262.
4. Martins A.P., Ferreira J.C. Robust converter synchronization to a weak grid through a DFT-based method. Renewable Energy & Power Quality Journal. 2006. Vol. 1, No. 4. P. 57-63. DOI:
5. Uemura H. System-level optimization of three-phase three-level T-type UPS system: dissertation for the degree of Doctor of Sciences.ETH. Zurich, 2015. 168 p.
6. Yang J.-Z., Liu C.-W. A precise calculation of power system frequency and phasor. IEEE Transactions on Power Delivery. April 2000. Vol. 15, No 2. P. 494-499. DOI: