Research On Modeling And Control Strategy Optimization Of Photovoltaic Power Generation

Since twenty-first Century,the capacity of photovoltaic power generation is increasing rapidly year by year.The integration of large capacity of photovoltaic power system into the power grid will affect the stability of the system and cause the voltage drop of the power grid.In this paper,the PSCAD/EMTDC software is used to study the single stage and two-stage type of PV grid connected system.The key technologies of symmetric short circuit and asymmetric short circuit control strategy are studied in view of the low voltage drop in the grid connected system of photovoltaic power generation.(1)based on the mathematical model of PV module,the influence of light,temperature,load and other factors on PV module is analyzed.With the change of light intensity,the output current,voltage and power of the photovoltaic cell increase with the light intensity,and the S=1000w/m2 is the maximum power point.When the light intensity is constant,when the temperature changes,the output of the maximum power point when the T= 25 oC is changed;When the load is changed and the load is changed,the output current,voltage and power of the photovoltaic cell are also changed with the load,and the simulation results conform to the maximum power control theory.(2)study the voltage space vector modulation technology,and establish the SVPWM simulation module to trigger thyristor space on-off control method.The PV converter is converted into DC by Clark transformation.Based on the two phase synchronous rotating DQ and static alpha beta coordinate system,the photovoltaic grid connected system MPPT is studied.On the basis of the maximum power of the conductance increment method,the dual loop control strategy of the voltage and current in the two phase synchronous rotating dq coordinate system of the photovoltaic generation single stage grid system is proposed,and the current prediction control strategy in the two phase static alpha beta coordinate system based on the double stage of the photovoltaic power generation system is proposed.The two parameters of the control strategy are calculated,and the number of PI is saved.The control strategy is optimized and the effectiveness of the control strategy is verified by simulation.(3)in view of the low voltage drop in the grid connected system of photovoltaic powergeneration,the mathematical model of the converter of symmetrical short circuit and asymmetrical short-circuit photovoltaic power generation system is studied,and the symmetrical short circuit limited current limited power control strategy in the grid connected system of photovoltaic power generation is analyzed.The low voltage crossing of symmetrical short circuit has been realized.The asymmetric vector is converted into a symmetric vector,and the current of the positive sequence equivalent circuit and the negative sequence equivalent circuit are adjusted by the double loop control strategy.The harmonic power components are removed,and the synthetic voltage vector is input into the SVPWM control module.A case of deep fault and shallow fault simulation model is set up.It is proved by case that the short circuit current is limited to 1.1 times less than the rated current when the voltage drop occurs in the grid connected system of photovoltaic power generation,while the reactive power is increased,the voltage of the power grid increases and the system achieves a new power balance while the active power is reduced.The grid voltage is guaranteed to operate at unit rated power factor.