Modeling,Simulation And Control Strategy Of IPOS Converter For Photovoltaic Power Station

Photovoltaic DC/DC converter is the key power electric equipment in large-scale photovoltaic power station integration system,whose function is to step up the lowvoltage dc generated by PV to a high-voltage dc for high voltage directional current.In this paper,based on boost full-bridge isolation converter(BFBIC),input parallel output series(IPOS)converter is used to achieve the performance of large power and high ratio.The detailed work of this paper is as follows:1)The principle and working modes of BFBIC are analyzed.Considering of the leakage inductance of transformer,an active clamp circuit is added to suppress the voltage spike on power switch tubes.Then,the principle of IPOS converter is analyzed and the equivalent relation of input sharing current and output sharing voltage is derived by the energy conservation theory.2)Introduce the specific modeling process of equivalent controlled source method and establish the small signal mode of BFBIC.Based on this model,the small signal mode of IPOS converter is derived.According to the small signal model,the stability and anti-interference of the converter can be analyzed.3)The DC/DC converter exists: maximum power mode and limited power mode.In maximum power mode,incremental conductance algorithm is adopted to realize maximum power point tracking and voltage compensation technology is added to realize sharing output voltage of all modules.In limited power mode,double closed loop is adopted to control the output voltage accurately,and sharing voltage loop is designed properly to realize sharing output voltage.Besides,the operation mode can be switched automatically by monitoring the voltage fluctuation of DC bus.4)Simulation models of a single module with rated capacity of 50 kW and IPOS converter including four modules are built in Matlab,and the simulation results verify the rationality of parameters and the effectiveness of the control strategy.When the module number is greater than 4,the speed of simulation will be very slow.So establish a simplified average value mode of BFBIC.In this paper,DC/DC converter for large-scale PV station is studied.The research results have positive reference value for large-scale photovoltaic power station integration system.