Abstract: The high proportion of renewable energy generation connected with the grid has brought great pressure to the peakshaving of electric power systems.Using energy storage for auxiliary peak-shaving is an effective way to solve this problem.However,the high cost of energy storage limits its large-scale application.To make full use of the peak-shaving function of the limited energy storage and reduce the load demand for energy storage capacity,this paper proposes a practical method to develop the combination of energy storage and normal,deep,given oil and start-stop regulation ways for peak-shaving.The calculation models of the technical index based on the probability of lack of peak load and the economic index based on the annual cost of peak-shaving are developed.The curved surfaces of technical and economic indices of the combined peak-shaving scheme are built.The combined peak-shaving scheme at the junction of technical and economic curved surfaces is the optimal one under different renewable energy penetration levels.Finally,with the regional grid and the national planning power system with wind and solar power as examples,optimal combined peak-shaving schemes under different renewable energy penetration levels are made.