Dead time between the complementary driving signals is needed to avoid short circuit in voltage source inverters (VSIs), however, this raises issues such as voltage distortion and harmonic generation. In wireless power transfer (WPT) systems, the ratio of dead time versus operating period becomes more problematic due to the high frequency, where the dead time can cause serious concerns regarding the phase errors and control performance deterioration. Therefore, this paper presents a comprehensive analysis of the dead-time effect for WPT systems based on a series–series (SS) topology. Firstly, it is found that voltage distortion appears in two regions in comparison with the three in one active bridge WPT system, and seven regions, as compared to the eight in dual active bridge (DAB) WPT system. Afterwards, a novel pulse width modulation (PWM) method is proposed, where the driving signals of the same phase leg are no longer complementary to each other. By employing the proposed method, the dead-time effect can be addressed up to a certain extent, and the desired voltage can be obtained in all the regions. In addition, the proposed method is not influenced by the system parameters, and can be easily applied to other high-frequency resonant converters. Simulated and experimental results are added to verify the feasibility and efficacy of the proposed control scheme.
Delay compensation based controller for rotary electrohydraulic servo system
