A ‘scalar’ discrete-time model for a digitally controlled h-bridge grid-connected inverter

This paper describes the modeling of a digitally controlled H-bridge grid-connected inverter system, which is widely used in distributed generation system. By using analytical expression of the elements in matrix exponential, the stability and dynamic behavior in this system is studied via a ‘scalar’ discrete-time model witch concerns the time-delay in digitally controlled system. By using this model, interrelation of state variables and system parameters can be analytically described by scalar coefficients. Then, the instability phenomenon of the system is accurately predicted, and the analytical expression of stability boundary can be obtained. Finally, the theoretical results are confirmed by both simulation and experiment results.