I. Introduction
The large-scale integration of renewable energy into the power system reduces the proportion of thermal power units, leading to a sharp cutoff in the reserve capacity provided by the source side. Due to the intermittent and fluctuating features of renewable energy, the reserve pressure of the system is growing up. Virtual power plants (VPPs) can aggregate demand-side resources such as load, energy storage and electric vehicles through collaborative control strategy and data interaction technology to provide reserve ancillary services, which effectively relieves the system pressure [1]. For a long time, committed demand side resources have been allowed to be used as emergency reserve for some capacity accidents with low probability and high risk [2]. With the development of power market, VPPs can provide reserve ancillary services through bidding in China. There are some subsequent problems to be solved. How to design the market clearing mechanism covering the thermal power reserve in source-side and the reserve in lode-side, and how to optimize the allocation of reserve resources by market clearing.