The emerging smart grid paradigm enables more efficient use of energy through optimizing the local grid operation. Conservation Voltage Reduction (CVR) is an application which aims at reducing the power consumption by decreasing the voltage level. Another important application is the Volt Ampere Reactive (VAR) control which aims at flattening the voltage profile and improving the power factor, which reduces the losses and eventually reduces the demand. PV solar systems can provide not only active power but also reactive power and hence, they can be exploited by the VAR Control application. Optimized Volt-VAR Control (OVVC) is a combination of these two applications that seeks an optimal coordination of different units to improve the performance of the power grid and save energy. In this paper, we use a co-simulation approach to explore closed-loop CVR and OVVC smart grid applications in a distribution grid. SGsim is a co-simulation framework consisting mainly of the network simulator OMNeT++ and the power grid simulator OpenDSS.