## 1 Introduction
Based on the idea of \"multi-level coordination, step-by-step refinement\", a multi-time-scale rolling scheduling model was established in [22; 23] considering the uncertainties of wind-photovoltaic power generation and system demand response. This paper proposes a multi-time-scale active power-coordinated scheduling method for combined operation of wind-photovoltaic-thermal-hydro power and battery units (WPTHB). Based on different power regulation speeds and capacity of batteries, thermal units, and hydro-pumped storage, a multi-time-scale scheduling model is designed to explore the complementary operation potential of batteries, thermal units, and hydro-pumped storage units. Comparing with a traditional scheduling model, the distinguished features of the proposed multi-time scheduling model are summarized as follows. (1) Based on the differences in power regulation speed and regulating capacity of thermal power generators, hydro-pumped storage units, and batteries, a multi-time-scale scheduling framework composed of day-ahead scheduling, hour-level rolling correction scheduling, and real-time corrective scheduling is proposed for the coordinated operation of wind-photovoltaic-thermal-hydro power and battery units. The proposed scheduling method has fully explored the complementary operation features of multiple energy sources in different time scales and thus can effectively reduce the regulating pressure of thermal power generators. (2) A predictive control algorithm incorporated with the rolling optimization and feedback correction is designed for the real-time corrective scheduling, which can effectively adjust the power outputs of thermal power generators, hydro-pumped storage units, and battery units in 15 min to ensure system operation security. (3) Simulation results of a real park system in Guizhou demonstrate that the proposed model predictive control (MPC)-based multi-time-scale coordinated scheduling model can accurately track the wind-photovoltaic power load demands and improve the overall operation economic revenue and static security of the system. The paper is organized as follows: Section 2 presents the complementary characteristic of wind-photovoltaic-thermal power generators, hydro-pumped storage units, and battery units, and the multi-time-scale general framework of the combined system is proposed in Section 3, with the corresponding multi-time-scale models detailed in Section 4. In Section 5, simulations on the multi-energy complementary demonstration park system in Guizhou validate the effectiveness of the proposed method, and a conclusion is drawn in the last section. Analysis on the Complementarity Operation of Wind-Photovoltaic-Thermal-Hydro Power and Battery Units  
Wind turbines convert wind dynamic energy into electricity, and its power generation is large at night and small at daytime due to changing wind speeds, thus it usually has an anti-peaking operation characteristic. Solar panels could only generate electricity during daytime and the greater the intensity of solar radiation, the greater the photovoltaic power output. In other words, the wind power change between day and night time is strongly affected by stochastic fluctuations, while for solar intensity it is straightforward, and wind can be often strong at night time while the sun is not out at night time; therefore, though both wind and photovoltaic power generation have high levels of volatility separately, they are strongly complementary when combined in operation in the hourly time scale, and could be combined to smooth the fluctuations of their total power generation. Since uncertain wind power and photovoltaic power outputs result in operation security issues of power systems, it is important to timely maintain power balance by some easily controllable power regulation devices. Hydro-pumped storage units, thermal power generators, and battery units are such kinds of controllable devices, but with different control features. Thermal power units convert heat energy from fuel combustions into electric power.