| In the cascade hydropower stations of Xiaojin power grid,the large and frequent random fluctuation of photovoltaic output has an impact on the active power balance of the system,thus affecting the primary and secondary frequency regulation and other operating characteristics of the system,greatly affecting the economic dispatching,and increasing the risk of frequency quality exceeding the limit.The fluctuation of power system frequency will have an important impact on the stable operation of all components in the power system.When the frequency deviation is too large,it may lead to the shutdown of some units and even the collapse of the whole system.Therefore,it is urgent to master the frequency characteristics and control measures of cascaded water light complementary combined power generation system,so that power planning and operation personnel can quickly and accurately grasp the level of frequency stability of the system.Firstly,this paper introduces and analyzes the characteristics and output characteristics of water light complementary combined power generation system,builds the model in psd-bpa simulation software,including the simulation principle and simulation model construction of each module of hydropower generator,analyzes the structure frame and operation mode of Xiaojin power grid,and establishes Xiaojin power grid based on the field data of Xiaojin county and the actual parameters of each power plant Simulation model.Secondly,based on the process of frequency change and the relevant factors of each stage,the simulation analysis of the influence of different factors on the system frequency is made without considering the governor,so as to establish the frequency evaluation index system of small-scale power isolated network system and explore the influencing factors of frequency dynamic change.The safety and stability characteristics of the two modes of grid connection and island of Xiaojin power grid are simulated and analyzed.During island operation,the three conditions of sudden load drop fault,off grid fault of small hydropower unit and disturbance under different inertia of system are simulated and analyzed respectively,and the corresponding frequency deviation curve and unit output curve are obtained.Finally,the existing frequency emergency control measures of Xiaojin power grid are analyzed,and the configuration and action of high-frequency cut-off measures are explored,and the differences between the cut-off measures of hydropower unit and the cut-off measures of photovoltaic unit in the high-frequency cut-off measures of Xiaojin power grid under the system power surplus are compared.According to the shortcomings of large frequency fluctuation and over control risk of the system after the action of high frequency cut-off measures,the precise control measures of photovoltaic are put forward: control the voltage of photovoltaic cell to control the active power of photovoltaic,then implement the real-time switching between MPPT(Maximum Power Point Tracking)and precise control measures through the voltage algorithm and inverter control,and take it as the control strategy of controlling the frequency of the system.In order to verify the effectiveness of photovoltaic precise control measures,the simulation is carried out in the small gold grid model built by psd-bpa.Under the mode of large and dry operation,the sudden load drop fault is considered,and the frequency control effect of traditional control strategy and photovoltaic precise control strategy is compared.The corresponding frequency deviation curve,system voltage curve and generator power angle curve are obtained,and the change test of the curve is compared To prove its validity. |
PDF Full Text Request