Chongming's current energy system is highly import-dependent and the distributed energy system with high renewable energy penetration should be taken into consideration. In this paper, a simulation model based on EnergyPLAN software with 2014 as the reference year is developed to represent Chongming's present energy structure. Four future scenarios which propose different further energy constructions have been observed. Results show that reductions in primary energy consumption, electricity import, annual operating costs as well as CO2 emissions are realizable when switching to an energy system with a high share of renewable sources combining natural gas CHP (Combined Heating and Power). After preliminary discussions, the feasibility of different renewable sources penetration are analyzed through calculating the excess electricity production (CEEP). The estimated optimal combination is generated when the PV fraction is 20% while wind energy fraction is 80%. Moreover, the analyses have taken into account that several flexible techniques are needed in order to balance supply and demand and to ensure the grid voltage and frequency stabilities. As a result, through the recommended three techniques, the excess production can be avoided as far as a renewable energy input of up to nearly 60%. (C) 2016 Elsevier Ltd. All rights reserved.