Research And Development For Test Platform Of The Dual Photovoltaic Grid Connected Inverter And Controller Under High Permeability Situation

With the increasing "penetration rate" of photovoltaic power generation in the power grid,the stability test of photovoltaic grid-connected inverter and its controller also has higher requirements.However,the common field-testing methods have the problems of high cost and poor flexibility.Aiming at the above problems,this paper researches and develops the test platform of the dual-photovoltaic grid-connected inverter and its controller.Firstly,the matching impedance of pv array Boost circuit,dual PV inverter,LC filter and anti-island detection of grid-connected PV system is designed in detail.Then,for pv arrays and Boost circuits,the maximum power tracking(MPPT)control algorithm based on conductance increment method is selected.For the grid-connected control strategy of dualphotovoltaic grid-connected inverter,Droop grid-connected control algorithm is selected.Finally,the simulation model of photovoltaic gridconnected power generation system was established,and it was simulated on Matlab/Simulink platform.Then,in view of the external voltage source characteristics of the traditional droop control and the problem that the output power will fluctuate greatly when the power grid impedance mutates,the anti-island detection algorithm for droop control and the improved droop control algorithm based on the power grid impedance detection are proposed respectively.The former first adds a small disturbance to the grid-connected photovoltaic power generation system.When isolated islands occur,the small disturbance value in the grid-connected inverter output active power is significantly smaller than that in the grid-connected inverter.Therefore,the occurrence of isolated islands can be judged by comparing the small disturbance values before and after isolated islands.The latter updates the PI control parameters in the droop control algorithm in real time according to the obtained power grid impedance value,so as to achieve the purpose that the photovoltaic grid-connected inverter can maintain the sensitivity of its equivalent impedance and adapt to the sudden change of power grid impedance.Finally,the high permeability dual-photovoltaic grid-connected inverter and its controller test platform are implemented.Firstly,the controller of photovoltaic grid-connected inverter is realized in digital signal processor(DSP).Secondly,the model of photovoltaic grid-connected power generation system is realized on RT-LAB real-time platform.Finally,the above DSP is connected with RT-LAB via I/O board card to form a closedloop hardware test platform in the loop.The above algorithms are tested on the test platform respectively.The results show that the established test platform can be carried out indoors and is feasible and safe.