Problems of voltage stabilization in MV and LV distribution grids due to the operation of renewable energy sources

The supply territory of the company E.ON Distribution in the Czech Republic (run by the company E.ON Czech Republic) accounts for approximately 1.5 million customers. More than 900MW of photovoltaic (PV) plants were connected to this distribution grid. It was detected the problem with overvoltage in approximately 20% low voltage distribution grids with connected PV plants and this problem has to be solved. The problem with high voltage variance is caused partially due to the operation of PV plants connected into the MV distribution grid and partially due to the operation of PV plants connected into the LV distribution grid. It is supposable, that the problem with overvoltage will occur when PV plants are connected both into the MV and into the LV distribution grid in the same part of the grid. In order to cope with the increased level of distributed generation new solutions for grid operation and new technologies are needed. In the paper are described three solutions for voltage stabilization. These proposed solutions prevent nonconforming voltage quality (overvoltage) according to the EN 50160 standard and following investments.