Renewable energy sources (RES) connection to medium voltage distribution networks has become widespread trend during the last years, bringing significant challenges for grid operators and requiring now methods of voltage control and congestion management. Voltage control in passive distribution networks is usually performed through automatic or manual adjustment of transformer tap ratio or through optimal operation and placement of capacitors. However, in networks with high shares of RES such measures aren’t adequate to cope with fast power fluctuations induced by RES such as wind and photovoltaic power plants. In this paper new algorithm for optimal coordinated control of RES is proposed. Voltage control and congestion management in medium voltage networks is performed through optimal RES active/reactive power management. The proposed algorithm is tasted on modified IEEE 69-bus system using realistic data for wind power plants and photovoltaic power (PV) plants considered in the analysis. By applying proposed algorithm it is possible to achieve high shares of RES in the existing network without the significant network reinforcements. Annual simulation was performed for the different simulation cases, showing the benefits of the proposed algorithm.