A novel method for accurate modeling and stability analysis of digital controlled grid-connected inverters

The exact-discrete model of digital-controlled non-isolated grid-connected inverter with H6-type (DNGI-H6) is firstly established by taking grid voltage ugrid as a time variable in a switching cycle. Due to one switching cycle delay between the duty cycle and the state variables of the DNGI-H6 system, the state variables of the discrete iterative equation are not independent of each other, which makes it hard to get the Jacobian matrix directly. By introducing a new state variable, the new method can avoid the complex calculation of high-order matrix, which simplifies the calculation process of Jacobian matrix. And the stability boundary and oscillation frequency are described. Finally, the accuracy of the discrete model and the feasibility of the new stability analysis method are demonstrated by the simulation and experimental results. © 2020, Solar Energy Periodical Office Co., Ltd. All right reserved.