| China has announced carbon reduction targets towards peak level by 2030 and carbon neutrality by 2060,which means that while steadily promoting the clean and efficient use of coal power units,the proportion of installed variable renewable energy,the penetration rate of its power generation and the share of its accommodation must be significantly increased in the next decade.In May 2019,the new provincial renewable portfolio standard based on renewable energy power accommodation guarantee mechanism was released.The new quota system will directly assess whether the annual renewable energy and non-hydro renewable energy power accommodation in each province reaches the responsible accommodation calculated according to the assigned accommodation responsibility weights,and will serve as an important constraint both for power dispatching agencies to optimize unit start-up and shutdown plans and power generation plans according to the optimal economic or carbon emission reduction effects,and for power trading agencies to achieve market clearing according to the same low-carbon and economic principles.Although the level of renewable energy accommodation is basically guaranteed under the mandatory quota policy,the accommodation of high proportion of renewable energy still requires high power system flexibility as support.China's power supply side of inflexible coal-fired thermal power units accounted for a high proportion,renewables-rich areas of the grid side interconnection level is limited,demand-side response,pumped storage and other storage side flexibility resources have no scale effect,thus,source-grid-load-storage flexibility resources are not enough to support the flexibility needs from energy power system with high proportion of variable renewable.Improving power system flexibility through various flexible accommodation measures has become an important basis for improving renewable energy accommodation at present.(1)Research on the construction and application of the optimization model for high-penetration renewable energy accommodationIn order to make the model analysis results closer to the actual power system operation,this paper firstly introduces a case scenario of model application,which is based on the real operation data of HRP-38 node system and the power system in Northwest China,with the characteristics of high proportion of renewable energy containing,large scale of unit combination and complex grid node structure.Subsequently,the large-scale unit combination and economic dispatch model for flexible accommodation of high proportion of renewable energy in the Northwest China under the new quota system is introduced,and constraints such as transmission capacity among five provinces in the Northwest China,out-of-area transmission volume,renewable energy ratio in transmission channels,allocation of provincial accommodation responsibility weights,and initial operating state of units during the optimization period are considered and designed,and the nonlinear objectives and constraints in them are linearized.The linearization of the nonlinear objectives and constraints is also performed to improve the speed of solving large-scale problems.The impact of the provincial accommodation responsibility weights allocation on the economic accommodation indexes of each province is analyzed,and the impact of the grid-side flexibility enhancement measures to improve the inter-provincial transmission capacity and out-of-area transmission capacity,the demand-side flexibility enhancement measures to improve the flexibility level of adjustable load,and the power-side flexibility enhancement measures by the deep peaking transformation of thermal power units to promote the economic accommodation of more renewable energy in the Northwest China are analyzed.The impact of economic accommodation of renewable energy in Northwest China is compared,and the differences of the flexibility measures in promoting the accommodation effect and the overall economy and carbon emission reduction index of the region are compared.(2)Research on the construction of the optimization models for high-penetration renewable energy accommodation under the new RPS.A single-objective low-carbon dispatch model for promoting high proportion of renewable energy accommodation in Northwest China under the new quota system,a single-objective low-carbon dispatch model that further considers grid interconnection and provincial interconnection,and a dual-objective low-carbon dispatch model that considers optimal regional power purchase cost and optimal regional carbon emission are established in comparison with the economic dispatch model,and the optimization results in the low-carbon accommodation cases in Northwest China under the three models are compared.The analysis focuses on the impact of the weight allocation of provincial accommodation responsibility on the low-carbon accommodation index of each province,and complements the analysis of the impact of grid constraints and feed-in tariffs for non-hydro renewable energy on each accommodation index of the region as a whole.(3)Research on the application of optimization model for high-penetration renewable energy accommodation under the new RPS-Taking Northwest China as an ExampleThe incentive model for the responsible body for the guaranteed accommodation of high proportion of renewable energy is established.First,based on the small-scale unit combination and economic dispatch model and examples,the impact of the tariff rules of the deep peaking compensation mechanism on the incentive for thermal power units to actively consume renewable energy through flexibility modification and participation in deep peaking auxiliary services is analyzed.The second one is based on the dual objective low-carbon and economic dispatching model with over-accommodation trading and voluntary green certificate trading and the actual case in Northwest China,focusing on the impact of provincial accommodation responsibility weight allocation and market price of dual certificate trading on incentivizing provincial grid enterprises to guarantee the accommodation of high proportion of renewable energy.(4)Research on construction and application of optimization model for high-penetration renewable energy accommodation based on market trading under the new RPS.A provincial interconnection energy and auxiliary services day-ahead market joint clearing model based on deterministic cost offer and uncertain cost offer of auxiliary services for market-based accommodation of high proportion of renewable energy is established respectively,and based on the actual case in Northwest China,the winning results of multiple sets of dual market bids,dual market clearing tariffs,auxiliary services costs and generation operation costs under different levels of auxiliary services demand,and the impact of the offer model,offer level and offer uncertainty on the dual market clearing,regional renewable energy accommodation and overall regional low carbon economic indicators is analyzed,and the joint dual market clearing result based on uncertain cost offer is used as an example to highlight the rich results that can be output from this paper's model. |
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