Research On Technology Of High Penetration Distributed Photovoltaic Access To Distribution Network Based On ADPSS

Photovoltaic power,an inexhaustible clean energy source,has attracted more and more attention.With the development of the photovoltaic power industry,the penetration rate of distributed photovoltaics into the grid is getting higher and higher.Photovoltaic power is greatly affected by the environment,and the output power is unstable,which will adversely affect the normal operation of the grid and load.The energy storage system has the effect of peak shaving and valley filling,which can stabilize the power of distributed photovoltaic output.Therefore,the use of distributed photovoltaics in conjunction with energy storage batteries is of great significance to maintaining the stability of the system.For distributed photovoltaic and energy storage systems,the control system of the converter is the key to ensuring the stable operation of the system.In this context,this paper has done a major research on the converter control strategy in the off-grid operation mode of distributed photovoltaic energy storage power generation system.Firstly,the topology of distributed photovoltaic energy storage power generation system is built,the characteristics of photovoltaic cells and lithium batteries are analyzed,and the parameters of lithium battery capacity,boost circuit,bidirectional DC/DC circuit and LCL filter are designed.The MPPT control of boost circuit and the constant voltage control of bidirectional DC/DC converter are described.Secondly,according to the output power of photovoltaic cells and the state of charge(SOC)of lithium batteries,the energy management strategy of grid connected operation is determined.This paper introduces the traditional PQ control of the converter in the grid connected operation,and analyzes the defects of the traditional PQ control strategy and the shortcomings of the PI controller used in the traditional PQ control.According to the shortcomings of traditional PQ control and PI controller,the traditional PQ control is improved.The quasi proportional resonant(PR)controller is used to replace the PI controller in the traditional PQ control current inner loop,which simplifies the control strategy and eliminates the use of PLL.In the two-phase static coordinate system(αβcoordinate system),the direct control of the incoming power is realized.Then,the root locus is used to adjust the parameters of the quasi PR controller,and the optimal parameters of the quasi PR controller are designed.Then,in the off-grid operation,the corresponding energy management strategy is adopted for the distributed solar storage system.The traditional V/f control strategy under off-grid operation is described,and the shortcomings of the traditional V/f control strategy are analyzed.The quasi-PR controller is used to replace the PI controller in the traditional V/f control strategy,and the grid voltage is used as the reference value of the V/f control voltage.The control system no longer needs to use a phase-locked loop,nor does it need to introduce a current inner loop decoupling component,which simplifies the control system structure.When the system operation mode is switched,it can realize the smooth switching from off-grid to on-grid or on-grid to off-grid.Finally,a simulation model of the distributed photovoltaic lithium battery power generation system designed in this paper was built on the platform of Advanced Digital Power System Simulator(ADPSS).This paper verifies the effectiveness of the converter control strategy of the distributed photovoltaic lithium battery power system in on-grid and off-grid modes,and further verifies the smooth switching of the on-grid/off-grid operation mode.