A new hybrid current control scheme for dead time compensation of inverters with LC filter

This paper presents a new hybrid current control scheme for dead-time compensations and power density optimization of grid-connected dc/ac inverter. A sliding mode controller is designed for compensating the dead-time nonlinear operations, and a PI controller operates in the linear areas. According to the SMC controller output, the unnecessary gate drive signals are removed and the counter side switch can be controlled up to 100% PWM duty ratio with a smooth transition between different dead time effect modes. With this control scheme, firstly, the influence of dead time can be eliminated, and the harmonic distortion can be greatly reduced. Secondly, the dc-link voltage can be minimized that will contribute to a reduced switching loss and a smaller ripple current. Furthermore, by the eliminations of unnecessary gate drive signals; the switching loss caused by the turn-off tail current can be reduced. The proposed control scheme is verified by simulation and experimental results. It is implemented in a DSP controller, and only some program codes are needed without adding any circuit or components. The reductions of conversion loss, harmonic distortion and ripple current are all achieved in the experimental system. The comparison results between the conventional scheme and the proposed scheme are presented in this paper.