FEATURES OF WORKING AND POSTFAULT OPERATION MODES OF ELECTRICAL GRIDS WITH DIRRECT CURRENT TRANSMISSION BASED ON CURRENT AND VOLTAGE SOURCE CONVERTERS

Abstract

The power industry has a number of relevant tasks concerning managing the modes of electric power systems: increasing the transmission capacity of lines, providing sustainability, redistribution of power between non-uniform grids. This issue can be resolved by implementing high voltage direct current (HVDC) transmission and Back to Back (BB), which might be based either on a current source converter (CSC) or on a voltage source converter (VSC). To date, the information on the differences between CSC and VSC based HVDCs as the power system modes control elements.

The study concerns the electric grid region of the mining zone of the South Urals energy system. RASTR.WIN program package is used to calculate the modes of the electrical network - the HVDC based on CSC and VSC models are constructed. Perspective loads of the electric grid area are characterized with unacceptable overload on the current of some lines, as well as a non-optimal distribution of electricity in the network. One of two-circuit lines was found to be overloaded. A decision has been made to convert it to direct current while subsequently studying the difference in regulating the regimes when it is performed in accordance with both CSC and VSC schemes.

The transfer of power transmission to direct current allows for the increase in its capacity, control of
the electric power flows for optimal loading of electric grid lines. The use of VSC does not require any ad­ditional sources of reactive power and allows controlling the flows of both active and reactive power in the network, i.e. it has broader functional capacities of the electric grid region modes control compared to the use of CSC.