# Optimal Scheduling of Hydro-PV-Wind Hybrid System Considering CHP and BESS Coordination
## 1 Introduction  
In recent years, with the increasing attention on global climate change and sustainable development, the penetration of renewable energy resources (RES) has steadily grown in the global electricity market. As renewable energy sources are starting to play a prominent role in revolutionizing modern power systems, the impact on their operation and reliability no longer goes unnoticed and neglected. However, because of their variability and difficult-to-predict nature, renewable resources are always considered an unreliable resource, and their scheduled generation cannot be ensured [1; 2]. Therefore, it seems that after overcoming the impediments related to the cost, the next problem which should be solved is the reliable and economically justifiable integration of RES into the power system. This is especially important in the case of RES such as wind and solar, which tend to exhibit a significant temporal and spatial variability [3]. The problems of RES integration into the power system have been studied in several studies [4; 5; 6]. In order to provide stable generation, coordination of several kinds of energy sources may be an effective way to overcome these disadvantages above. Because of the large scale and good regulation performance, hydroelectric power can effectively restrain the fluctuations in wind and photovoltaic generation to improve their stabilities. Based on integrated technology, establishing a hydro-photovoltaic-wind hybrid system is seen as a promising method to realize the conception [7; 8]. [PERSON] et al. [9] performed the coordinating strategy of a wind-hydro hybrid system connected grid under frequency-based pricing. Reference [10] studied the portfolios of multiple energy sources considering the complementarity between wind power and photovoltaics. The portfolios may play an important role in reducing the fluctuations and intermittency to improve the reliability of individual generation [11]. A method to solve the optimal power flow problem with different probability density functions for wind and solar power was suggested by [PERSON] [12]. A stochastic day-ahead optimal strategy for a wind-hydro system was presented by [PERSON] [13] considering the risk of the system. References [14; 15; 16; 17] studied the models of the wind-hydro hybrid system to reduce the cost of imbalances. Compared with renewable resources, combined heat and power (CHP) systems are highly controllable and have quite quick rates. Therefore, these systems with CHP are flexible and can be used to ensure balance and improve the stability of RES integration into the power system [15]. The models for determining the strategy for optimal operation and trading of CHP systems have many relevant studies. CHP systems can be optimized based on different optimization criteria, such as energy savings, cost reduction, minimum environmental impact, or a combination of all of these [16]. Several methods and criteria have been proposed in the literature for optimization of the size and operation of CHP systems [17; 18; 19; 20; 21]. References [22; 23] proposed deterministic optimization models, while References [24; 25; 26; 27] presented stochastic programming models of CHP systems due to their ability to approach various uncertainties in CHP system operation. References [28; 29] proposed an economic dispatch model that included CHP units, with a comprehensive survey reported [30; 31; 32]. [PERSON] [33] designed a CHP system by integrating the thermal storage techniques considering the uncertainty of demand. Taking the variation of demands and prices into account, [PERSON] et al. [34] solved the best CHP plan based on the decision theory concepts. [PERSON] et al. [35] promoted an aggregation model of a CHP-photovoltaic (PV) hybrid system under uncertainty in the Belgian market. In addition, due to the ability of energy storage, the battery energy storage system (BESS) is generally regarded as an effective tool to deal with the intermittent characteristics of RES.