Dynamic Characteristics Research And Optimization On Photovoltaic Pump System

This study is carried out under the financial support from National Key Research&Development Program of China?2016YFC0400202?and Agriculture Key Research&Development Program of Jiangsu Province?BE2017356?.With the increasingly obvious problem of energy shortage and the urgent need for ecological civilization construction,solar energy has been more and more widely used.Photovoltaic pump system is a typical application of solar energy,widely used in agricultural irrigation,city waterscape,grassland husbandry and other fields.It has the advantages of energy conservation,environmental protection,low maintenance cost and good adaptability to crops.However,the operation characteristics of photovoltaic pump system are largely affected by external environmental factors,which leads to great instability of the system operation.This paper makes a thorough research on the dynamic operation characteristics of photovoltaic pump system by using a method of combining experimental test,simulation calculation and numerical simulation.The main work and research results are as follows:1.The use environment and characteristics of photovoltaic pump system are introduced,and the present research status of photovoltaic pump system in terms of structure,performance and optimization,both at home and abroad,are systematically summarized.2.A test bench of photovoltaic pump system was built to study the optimal configuration determination method of test system components,such as the capacity of photovoltaic array and the valve opening.Then the system dynamic characteristic was tested under the solar radiation intensity transient when the system configuration was optimal.Also prediction model of water yield was established based on the experimental data and similarity law.The results show that:?1?With the increase of solar radiation intensity,the dynamic response time of transient changes gradually decreases,and the system response time when solar radiation intensity transient increases is lower than that when the transient decreases.?2?With the increase of transient gradient,the dynamic response time of the system increases..?3?When the solar radiation intensity changes from the saturation value quickly,the stability of the system is poor after the initial transient,and the response time is longer than the solar radiation intensity transient increase.The increase is about 2s.?4?No matter the solar radiation intensity changes smoothly or drastically,the established prediction model of water yield have higher prediction accuracy.3.Matlab/Simulink simulation modeling of each component of the photovoltaic pump system was established,and the system characteristic under the condition of transient solar radiation intensity was simulated to obtain the curves of the system speed and flow.The simulation results were used as the boundary conditions in the CFD simulation of the photovoltaic pump internal flow.And the numerical simulation was first used to study the pump operation characteristics under the solar radiation intensity transient.The results show that:?1?The established numerical simulation method of the photovoltaic pump internal flow under dynamic conditions has higher reliability.?2?As the solar radiation intensity increases,the axial force of the impeller gradually increases.The fluctuation of the impeller axial force is larger under lower solar radiation intensity and the maximum is about 2.5N.?3?When the transient condition exists at lower solar radiation intensity,the change range of pressure fluctuation at the the pump outlet is higher,about 10kPa.4.The blade outlet angle?₂,blade outlet width b₂,blade number z and impeller hub diameter D_2minmin were chosen as optimal variables,an orthogonal design was used to establish optimal samples,and numerical simulation method was used to optimize the samples,thus establishing a performance optimal method of photovoltaic pump.The results show that under the same solar radiation intensity,both flow rate and head of the optimized system are improved.Under the conditions of steady and transient solar radiation intensities,the daily water yield of the system increases by0.88m³ or 1.36m³.