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With the large-scale grid connection of wind and photovoltaic power, the contradiction between renewable energy and thermal power is becoming more and more serious. To solve this problem, this paper comprehensively considers the construction and operation costs of power plants, and constructs an optimal generation expansion planning model of a combined thermal–wind–photovoltaic​ power system with the objective of minimizing total cost. The planning is calculated under the boundary conditions of ensuring the safe operation of the power grid and taking into account the share requirement, utilization requirements and construction requirements for renewable energy. The model is applied to the self-use and supporting power plants in Xinjiang. The results show that the proposed generation expansion plan can realize the coordinated development of three types of power sources under multiple boundary conditions, which has good applicability.

Background The scarcity of fossil fuels and their high emissions impact on the environment have forced the rapid development of renewable energy. Wind and photovoltaic power play a more and more important role in today's power system because of their clean and renewable characteristics. However, with the large-scale grid connection of wind and photovoltaic power, the contradiction between renewable energy and thermal power is becoming more and more serious. The unreasonable planning of power generation resources has also caused a lot of waste of electric power.Methods To solve this problem, this paper comprehensively considers the construction and operation costs of power plants, and constructs an optimal generation expansion planning model of a combined thermal-wind-PV power system with the objective of minimizing total cost. The planning is calculated under the boundary conditions of ensuring the safe operation of the power grid and taking into account the share requirement, utilization requirements and construction requirements for renewable energy. The model is applied to the self-use and external power plants in Xinjiang.Results The results show that this generation expansion plan can reduce the total cost of the power plants while ensuring the load demand. The renewable energy has also received more consumption share and its abandonment rate has dropped significantly. Numerical examples show that the optimization model has good applicability.Conclusion The proposed optimization model can realize the coordinated development of three types of power sources under multiple boundary conditions, which can not only guarantee the economy of power construction, but also take into account the optimization of environmental benefits. Reasonable generation expansion planning can improve energy efficiency, achieve clean and low carbon in the process of power generation, and promote the sustainable development of society.

In this work, SEM-EDS and FTIR were first used to analyze the physical and chemical characterization of salix (SL), the raw coal gangue (CG)/calcined coal gangue (CCG) and the biochar. Then the pyrolysis characteristics of SL, CG/CCG and their mixtures were explored by thermogravimetric analysis (TGA). The research results showed that the reactivity of CG was improved after calcination treatment. Compared with CG blended SL, the co-pyrolysis of CCG and SL had a significant synergistic effect. There was a strong synergistic effect when SL blended with 30% CG. When SL blended with 40% CCG and the pyrolysis temperature was higher than 530°C, the adsorption performance of biochar had been significantly improved, and the addition of CCG that obviously promotes the carbon-forming reaction of SL and the biochar yield increased by 5.43%.