The recent growth in penetration of photovoltaic generation units (PVs) has brought new operation ideas to Power Producer-Suppliers (PPSs) and/or Megawatt-Solar Power Plant (MSPP) owners which achieve more profitable electric power management for them. Their expectable profit will improve if the PPSs operate their controllable generators (CGs) appropriately, and sell the generated electricity properly to contracted customers and/or Power Exchanges together with the output of MSPPs. Furthermore, the profitable cooperation between the PPSs and the MSPP owners decrease the difficulty in supply and demand balancing operation of main power grids. Hence we can expect that the profitable cooperation will become one of the most efficient PV-compatible operations with few adverse effects for the main power grid's operation. However, when the PPSs cannot procure sufficient electricity by only their CGs and the output of MSPPs, there is a risk to purchase the very expensive electricity from the main power grids to compensate the shortage. This paper presents a problem framework and its solution to make the optimal power management plan for the PPS considering the electricity procurement from the MSPPs. The aim of this research is to design a profitable and stable power management plan for the PPS with the intension of providing both better selling profit to the PPS and the MSPP owners, and reducing difficulty in supply-demand balancing operation, which is caused by the prediction uncertainty of PV output, to the main power grids. In addition, in order to verify the usefulness of the authors' proposal, numerical simulations are carried out and their results are discussed.