Research On Active Power Control Strategy For Clusters Of Photovoltaic Power Stations

With more and more large scale photovoltaic power connecting to the grid,the output power fluctuations caused by intermittency and randomness of solar light resources have a more serious impact on the stability of the grid.In order to improve the control ability of PV system,the concept of PV clusters is proposed in this thesis.This method makes use of the complementary ability of the solar energy,so as to increase power grid's capacity to accept photovoltaic power station,and realize that the photovoltaic can be controlled like conventional energy.This thesis has certain theoretical significance and application value.The main contents of this thesis are as follows.(1)The basic principle and characteristics of photovoltaic cells are studied.This thesis establishes a model of photovoltaic cell model and photovoltaic array model,and then study the maximum power point tracking method of the output of the photovoltaic cells.The feasibility of the method is verified by MATLAB simulation.Finally,the PV model is simulated by the actual operation data in Qinghai.(2)In this thesis,the influence of the large scale photovoltaic power connected to the grid is studied.The influence of output fluctuation on the system frequency is analyzed.And then,the principle and a hierarchical control structure of active power control of photovoltaic power plants are studied.On basis of the above,this thesis puts forward the method of active power control for mutil time scale photovoltaic clusters.The control functions and control objectives of each layer are also analyzed.(3)In this thesis,the photovoltaic clusters are classified according to the operation state and controllable ability,and the PV power stations are divided into three categories.According to the aim of the active power regulation,two different scheduling schemes are established according to the different scheduling arrangements.Then,two kinds of power allocation methods are proposed,so the active power can be distributed reasonably.One is the proportional distribution method under the condition of limited output,this method is simple and easy,and the other is the economic optimal allocation method under the condition of limited output.Finally,the feasibility of the control strategy is verified by comparing the two schemes by numerical simulation.Finally,a numerical example is given to campare the two schemes,and verify the feasibility of the control strategy.