Risk-Theory-Based Short Term Adequacy Evaluation And Decision Making For Power Systems With Wind Power

Power system adequacy is a foundmental question throughout system planning and operation. With consideration of uncertainties, power system adequacy evaluation and decision are basic work for system safety and reliability. The integration of large scale wind power generation in recent years has brought great uncertainty to troditional power system. At the same time, the charging and discharging behavior of electric vehicles at demand side are also uncertain. All the above bring lots of difficulties and risks to power system operation and control. Troditional adequacy evaluating indexes and methods can hardly meet the new request from system resource and load. Therefore, short term adequacy evaluation and decision making for power systems with wind power is studied in this dissertation. Main research work and innovative achievements obtained are as follows.To solve the reserve requirement caused by wind power uncertainty, the fluctuations of wind power output under different time scale and distribution characteristics of wind power short term froecast error are analyzed. With reference to the risk theory, wind power uncertainty evaluation indexes in time-dimension and power-dimension are proposed. Buhlmann credibility model is used to bring together the above indexes and establish the credibility indexes which are introduced into reserve requirement evaluation due to wind power uncertainty. Case study and validity test show that credibility indexes inherit the advantages of time-dimension indexes and power-dimension indexes and can obtain the risk information from both historical data and forecast data. The method reduces unreasonable operating reserve without loss of system security, which may be a kind of promotion to system economical operation.Aiming at generation system short term adequacy evaluation with uncertainties from resource and load, traditional reliability indexes operational loss of load probability (OLOLP) and operational expected load not served (OELNS) are redefined and a new index buffered loss of load probability (BLOLP) is proposed. In those definitions, shortage of available capacity (SOAC) is used as the representative function of system adequacy. The relationships between adequacy indexes and load requirement, load forecast error, capacity and forced outrage rate of traditional units, outrage rate of wind turbines and wind power forecast error are studied. Theoretical analysis shows that the system operation mode is divided into3parts:adequate, at risk and inadequate by the proposed index in a probabilistic manner. Simulation tests show that the proposed probability index is comprehensive than the other two because it contains adequacy function tail part information.To solve the unit commitment (UC) problem with adequacy constraint, constraints based on unit commitment risk (UCR), LOLP and ELNS are introduced and their solution methods are discussed. UC models with OLOLP and BLOLP adequacy constrains are established. Their solution methods are studied. By compare with the other UC models in case study, the model based on BLOLP adequacy constraint shows the advantages of fast speed and high reliability. It can solve the operation scheme under different adequacy request, optimize the active power and reserve capacity as well and show the adequacy estimation under certain operation scheme which may be a visualized reference to system operators.Taking plug-in hybrid electric vehicle (PHEV) as an example of demand side uncertainty, the operational adequacy decision making of distribution systems with PHEV is studied. Working mode, charging and discharging characteristics and dispatching manner of PHEV are introduced. Considering uncertainties from resource and load,2operational adequacy measuring indexes are proposed with system operating reserve as adequacy representative function. A multi-stage decision making model with the objective of maximum system adequacy is established. Results of simulation test show that the proposed indexes can coordinate the dispatchable load of different time sections with guarantee of adequacy of the whole study period. The multi-stage decision making model can optimize the purchase scheme of different energy and the dispatch scheme as well. Relationships between decision variables of different time sections are considered and that is the essence of dynamic optimization problem. The study shows a reference to the operation department of a distribution system to properly guide the PHEV charging and discharging behavior in order to reduce their negative effect and play a positive role in power system operation.