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With the high proportion of renewable energy connected to the grid, the problem of insufficient flexibility in the power system has emerged. Renewable energy and controllable distributed resources can be aggregated and managed through virtual power plants, reducing the need for flexibility to a certain extent. Although building new energy storage systems can compensate for the lack of flexibility, it requires high initial investment costs. To address this, this paper proposes a lease mechanism for coal-fired units based on the combination of carbon credits and prices, providing the right to use coal-fired units for virtual power plants. Subsequently, different demand response strategies are utilized to control the controllable loads of various users, thereby providing certain controllable resources for the virtual power plant. Additionally, to ensure the optimal decision-making of the virtual power plant operator, a cost model accurately describing the capacity degradation state of the energy storage system is adopted. Moreover, a multi-time scale scheduling strategy of virtual power plant is implemented to fully utilize controllable resources of different time scales, effectively dealing with the power imbalance caused by multiple uncertainties. The results show that utilizing the leasing mechanism of coal-fired units and employing demand response strategies from different users can provide flexibility to the virtual power plant. The accuracy of the capacity degradation model used by the operator significantly impacts the optimality of the scheduling plan. • The scheduling model of VPP consider capacity degradation of ESSs, carbon trading, and DR strategies. • A lease mechanism for coal-fired units based on the combination of carbon credits and prices is proposed. • This paper proposes ISBDR strategies for reduceable loads. • The ESSs capacity degradation model adopted takes into account DOD and SOC. • A multi-time scale scheduling strategy of VPP is adopted to deal with multiple uncertainties. [ABSTRACT FROM AUTHOR]

To construct a new energy system during the low-carbon transition, renewable energy sources (RESs) are increasingly being installed on a large scale worldwide which require thermal power units to operate at low loads and respond quickly to compensate for frequency fluctuations of the power grid during deep peak shaving and frequent load changes. While coal-fired thermal power plants operate under the deep-peak shaving process, low-frequency oscillation (LFO) accidents from the generation side have occurred constantly. According to our investigation, the reasons are the overlook of the nonlinearity of control valves is obviously highlighted under low load, and the preset parameters of the original control device can not match the flow characteristics, which may seriously cause a recurrence of LFOs. This paper focuses on generation-side LFO caused by the prime mover and its governor under all operating conditions constructing a novel nonlinear model and designing an oscillation feature observation matrix to identify the LFO modes, and a hierarchy feature-state observation classification method preventing LFO on the generation side is proposed. The results show that the proposed method can suppress the LFOs ahead, and this approach can weaken the oscillation amplitude by 85% and reduce the oscillation duration by 30 s. • Retrofit the small frequency offset compensation and the valve flow module, simulate dynamic characteristics accuracy. • Propose an oscillation ranking method to evaluate the security level of power oscillation and verify its reliability. • Design the hierarchical prevention control strategy for LFO in stages and validate the effectiveness of thecontrol strategy. [ABSTRACT FROM AUTHOR]