Digital-analog simulation test of grid-connected performance for string inverter

Power device switching frequency of string inverter is greater than 10kHz, the traditional real-time simulation platform based on CPU processor can not meet the needs of simulation. In this paper, based on FPGA and CPU processors, hybrid simulation model and test scheme of grid-connected performance for string inverter are proposed. First, using RT-LAB, hybrid simulation test platform for string inverter is set up, which contains digital simulation model, linear transformation unit and tested inverter controller. Then, based on the equivalent decoupling model of transformer, Seamless connection between the large step size simulation model of 20us and the small step size simulation model of 0.1us are realized. A primary power circuit models are established for the string inverter low voltage ride through (LVRT) test, frequency adaptation test and anti-islanding protection test. Finally, according to the national standard GB / T 19964-2012 “the photovoltaic power generation station access to electric power system technical regulations”, digital analog hybrid simulation test of low voltage ride through (LVRT), adaptive frequency and anti-islanding protection is carried out for string inverter controller, simulation test results can fully reflect the dynamic and static performance of the string inverter, which can effectively prove the correctness of the proposed test scheme.