Market-Based Power Dispatch Method With Sequential Coordination For Improvement Of Frequency Performance

The development of new power systems dominated by renewables is an important way to achieve the goal of “carbon peak and carbon neutrality” in China.The largescale integration of renewables with large uncertainties and fluctuations,such as wind and solar,could aggravate the burden of the real-time balance and threaten the frequency performance.Given this,it is urgent to stimulate the flexibility of power system operation and promote the consumption of renewables by the regulation function of the electricity spot market.The regulation function is reflected by the following two aspects: 1)the market should set the proper frequency regulation requirement in power dispatch to coordinate regulating resources,such as thermal power units(TPUs)and energy storage systems(ESSs),to provide frequency regulation services.Thus,regulation capabilities can be ensured;2)regulating resources should obtain economic compensation to incentivize them to provide services continuously.Meanwhile,the frequency regulation costs should be reasonably allocated to market participants that cause the need for frequency regulation,such as load consumers and renewables.In this way,they have the motivation to reduce their uncertainties and fluctuations.However,the market-based power dispatch method used in industrial practices cannot effectively realize the aforementioned regulation function,which is illustrated as follows: 1)in power dispatch,the existing spot market utilizes the sequential dispatch method of “day-ahead”,“intra-day”,and “real-time”.The latter dispatch modifies the dispatch results of the previous dispatch according to the latest system status.However,each level of dispatch only focuses on the forecasting information of the net load under the corresponding dispatch granularity.The fluctuations in the future are not elaborately considered.As a result,the sequential coordination between dispatch at different levels is not effectively excavated,which makes it difficult to effectively consider the actual regulation requirement in dispatch;2)in cost allocation,the existing methods mainly consider the impact of uncertainties of market participants on frequency regulation ancillary services.However,the important impact of time-varying fluctuations is ignored,which is not in accordance with the principle of “who cause,who share”.With this in mind,a market-based power dispatch method with sequential coordination for improvement of frequency performance is proposed based on the current dispatch framework.The major works are summarized as follows:(1)Propose a framework of the market-based power dispatch method with sequential coordination for improvement of frequency performance.First,the problem of the current market-based dispatch framework is analyzed: 1)the current dispatch method lacks the sequential coordination between adjacent levels of dispatch,resulting in that the actual regulation requirement cannot be comprehensively considered;2)the current cost allocation method cannot consider the impact of time-varying fluctuations of market participants.To solve the aforementioned problems,the corresponding improvement strategies are proposed: 1)in power dispatch,the elaborate forecasting information of the net load reflecting the actual regulation requirement is embedded into each level of dispatch of “day-ahead”,“intra-day”,and “real-time” in a matching manner.In this way,the intra-interval fluctuations can be considered in advance.Thus,the sequential coordination between adjacent levels of dispatch can be established;2)in cost allocation,the contribution of an individual market participant to the regulation requirement is quantified by sensitivity analysis to achieve reasonable cost allocation.(2)Propose a market-based day-ahead dispatch method with the high-resolution quantification of the frequency regulation capacity requirement.First,to address the problem that the existing capacity requirement quantification method cannot consider the fluctuations of the net load,a data-driven method considering the intra-day power fluctuations is proposed.The coupling between the day-ahead dispatch and intra-day dispatch is established.Then,to avoid the violation of the system operating constraints caused by frequency regulation during real-time operation,a capacity allocation method based on the probabilistic correction of operating constraints violations is proposed.Finally,to consider the comprehensive impact of uncertainties and fluctuations of market participants,a hierarchical cost allocation method of frequency regulation capacity is proposed.With the proposed method,the sufficiency of the capacity can be ensured.Moreover,the reasonable cost allocation of capacity can be achieved.(3)Propose a market-based intra-day dispatch method with elaborate modeling of frequency regulation behaviors.To consider the influence of intra-interval fluctuations,the elaborate frequency regulation behaviors model is established according to the highresolution net load forecasting curve and the modeling of the automatic generation control(AGC)strategy.Then,it is embedded into the intra-day dispatch.In this way,the frequency regulation mileage requirement and costs caused by the intra-interval fluctuations can be considered.The coupling between the intra-day dispatch and the frequency regulation process is analytically established.To reduce the computational burden,an efficient calculation method based on two-stage model simplification is proposed.The proposed method does not change the interval of the intra-day dispatch command.By considering the actual regulation requirement and costs in intra-day dispatch,both the frequency and economic performance can be improved effectively.(4)Propose a hierarchical AGC dispatch considering the lifespan protection of ESSs and its cost allocation method.First,regarding the frequency regulation challenges brought by renewables,a hierarchical AGC dispatch method is proposed,which includes proactive AGC dispatch and real-time AGC dispatch.In proactive dispatch,a proactive AGC dispatch model embedding state of charge(So C)recovery is established based on the mileage requirement forecasting.A uniform So C model considering comprehensive ramping circumstances of ESSs is proposed with low model complexity.Real-time dispatch based on the current system status is considered to compensate for the forecast error and unforeseen fluctuations in proactive dispatch.The dead band and forced So C recovery of ESSs are embedded to alleviate their degradation.Then,a cost allocation method of frequency regulation mileage considering the contribution of market participants to the system power unbalance is proposed.The system power unbalance is quantified to reflect the mileage requirement.The contribution of market participants to the mileage requirement is quantified based on sensitivity analysis.With the proposed method,the system frequency performance can be ensured.The degradation of ESSs can be alleviated.Moreover,the reasonable cost allocation of frequency regulation mileage can be achieved.In summary,the elaborate modeling of the frequency regulation requirement is achieved by embedding the elaborate forecasting information of the net load.In this way,the sequential coordination between dispatch at different levels is excavated,which can ensure the regulation capability for power balance during the real-time operation;also,the impact of different market participants on the costs of frequency regulation ancillary service is revealed by the sensitivity analysis,based on which the reasonable cost allocation is achieved.The proposed method can provide technical support for realizing the regulation function of the electricity spot market to ensure the system frequency performance under large penetrations of renewables.