| With the rapid economic development,society’s demand for electricity is increasing.In recent years,the rapid development of renewable energy power generation technology has resulted in an increasing proportion of renewable energy sources in a power system,such as wind power.However,wind power is highly uncertain,which undoubtedly brings a huge burden to the safe and economic operation of a power system.For the problem of wind power uncertainty,there are many effective methods,such as random scene simulation,chance constraint and robustness optimization.However,these methods only ensure power balance at both ends of an economic dispatch interval,and ignore the severe power mismatch problem caused by the short-term sharp fluctuation of wind power in the economic dispatch interval of a power system.In view of this problem,this paper conducts a risk assessment of the power mismatch inside a dispatch interval(intra-interval),and then proposes a strategy to solve the intra-interval power mismatch(IIPM)based on the assessment results.At first,we build an intra-interval variation curve of wind power based on the ramping parameters of the short-term variations of wind power,and then we combine the intra-interval variation curve of wind power and economic dispatch constraints to establish a linear programming model for the risk ass essment of intra-interval power mismatch in a power system,which can evaluate the power mismatch during the economic dispatch interval of a power system in the worst case of nonlinear power variation,which is called the largest intra-interval power mismatch.And then we can judge whether the largest intra-interval power mismatch exceeds the security threshold and obtain the ratio of the IIPM exceeding the security threshold.Based on risk assessment results of intra-interval power mismatch in a power system,this paper proposes effective strategies from two aspects: preventive dispatch and corrective dispatch.Among them,the preventive scheduling strategy adopts a heuristic method of wind curtailment,and finally reduces the largest intra-interval power mismatch below a security threshold through a limited number of iterations so as to ensure that the system reserve capacity or AGC can completely compensate the intra-interval power mismatch of the power system,which can ensure the system security during the whole economic dispatch interval of a power system without sacrificing too much economy.The corrective dispatch strategy is to adjust the ramp rate of the thermal generators when the system just detects the power mismatch inside the dispatch interval to ensure that the power mismatch is within the security threshold in the following time.Corrective dispatch aims to compensate for the intra-interval power mismatch when increasing the generation power of the thermal generators as little as possible.In addition,a wind curtailment strategy is added as an auxiliary strategy to make up for the limitation of the ramp rate of thermal power.In this paper,6 buses in the original IEEE 118-bus system are connected to the 6wind farms,respectively,and the proposed model is simulated and tested on the modified IEEE 118-bus system.The simulation results show that the risk assessment strategy of intra-interval power mismatch can well judge whether there is too much power mismatch in the economic dispatch interval.For the case where the intra-interval power mismatch exceeds the security threshold,the preventive dispatch strategy and corrective dispatch strategy are simulated,respectively,and results show that the two strategies can reduce the exce ssive power mismatch below the security threshold during the whole dispatch interval and can pursue economy as much as possible when ensuring the intra-interval security of the power system,which proves the effectiveness of the proposed model in this paper. |
