Economic Dispatch Strategy Of Power System Considering Wind And Photovoltaic Power Uncertainties

With the depletion of fossil energy and the deterioration of human ecological environment,renewable energy has received great attention and development,and energy reform is imminent.Under the new situation,the way of power generation and utilization is diversified.Based on the uncertainty of the load,the proportion of new energy represented by wind and photovoltaic power has increased significantly.However,because of the volatility,intermittency and randomness of new energy output,their integration introduces a lot of uncertainties to the power supply side,which not only brings great difficulties for the consumption of new energy,but also presents great challenge to the safe and economical operation of power system.Thus,under the new situation,full consideration of the influence of wind and photovoltaic power uncertainty in the economic dispatch has great significance to the safe and economic operation of the power system.Based on this,aiming at the new situation that current economic dispatch of the power system is deeply affected by the new energy output uncertainties,this paper conducts a study on the economic dispatching strategy that can effectively mitigate the influence of new energy uncertainties.From different perspectives,a variety of ways is adopted to deal with the uncertainties,the main innovative results are as follows:(1)Based on historical data,the time and spatial characteristics of wind and photovoltaic power are further analyzed.The meaning of new energy output uncertainties is explained in detail,and its output characteristics of the second-level and the hour-level is also analyzed.The complementarity of wind and photovoltaic power output in various time scales and spatial ranges is studied,and the spearman correlation coefficient is introduced to characterize the their complementarity.The normal distribution function is used to fit the forecast error rate distribution of wind and photovoltaic power in different output levels.The expectation and standard deviation of the probability density distribution function of forecast error rate for each output interval are obtained,and their distribution rule is further analyzed.Finally,the relevance of the wind and photovoltaic power forecasting error is explored,and the spearman correlation coefficient of the wind and photovoltaic power forecasting error is obtained by seasons.(2)Utilizing the complementarity of multiple heterogeneous energy sources and multi-time-scale scheduling modes,a dynamic dispatching strategy based on multi-time-scale complementarities of various heterogeneous energy is proposed.First,wind,solar and hydro power is bundled as a virtual power(VP)according to their complementarities,and the load tracking index is defined to represent the ability of the VP to track the load so that it can well follow the load.Meanwhile,a multi-time-scale complementary dispatch model is established,which includes a day-ahead 24 h scheduling,an intra-day 4h rolling scheduling and a real-time 15 min scheduling.Furthermore,rolling amended wind-solar curtailment constraints are set,so that the periods that have abandoned more wind and solar power in the longer timescale scheduling can have more wind-solar curtailment up-regulation margin in the shorter one.According to the latest forecasting,considering the complementarities of different timescales,the hydropower and thermal power output plan and the wind-solar curtailment constraints are amended continually,which ensures the VP's tracking ability,optimizes the actual complementary and stabilizing effect of the complementary system as well as reduces the regulation pressure of the thermal power.Thus,the adjustment benefit,environmental benefit and economic benefit of the whole system is maximized.(3)Aiming at the uncertainties of the forecast value in multi-time scale scheduling plan,a multi-time scale robust economic dispatch strategy of multi-source hybrid power system based on variable confidence level is proposed in this paper.First,the robust model of the wind,photovoltaic and load forecasting value of each time scale is established.The deterministic constraints of each time scale are transformed into robust constraints which take uncertainties into account.Thus,a multi-time scale robust economic dispatch model is established.Meanwhile,robust level whose confidence level increases with the shortening of time scale is set to improve the scheduling conservative degree step by step.This reflects that with the approach of the real scheduling time,the tolerance to the worst uncertainties case for the system reduces.The selection principle of the robust level of each time scale dispatch is also put forward.An example is calculated to verify that this strategy can effectively reduce the impact of wind,solar and load forecast value uncertainty,relieve adjustment pressure as well as decrease the wind and load curtailment capacity,which achieves a great balance of security,economic and environmental benefit.(4)Aiming at the correlation between wind and photovoltaic power forecast error,an economic dispatch model considering joint wind and photovoltaic power forecast error is put forward.Based on historical data,the distribution function of wind and photovoltaic power forecasting error at different output levels is fitted.The spearman correlation coefficient is introduced to describe the complementarity of the wind and photovoltaic power forecasting error by season,so as to obtain the joint wind and photovoltaic power forecasting error distribution model.Then,the joint forecasting error cost of wind and photovoltaic power is introduced into the objective function of the dispatching model in power market,and the impact of joint wind and photovoltaic power forecasting error on the economic dispatch result of the power system under the power market environment is considered systematically.The rationality and effectiveness of the model is illustrated in an example.