In a typical wireless power transfer (WPT) system, the load, the mutual inductance and the required tuning frequency can vary in a particular range. Variation of each parameter can substantially impact the dynamic characteristics of the system. Thus, they can be considered as the sources of uncertainty in the system. To address this issue, robust control methods such as -synthesis are developed to deal with possible system uncertainties. In this paper, first, the generic dynamic analysis of the series-series WPT compensation network for two modes of operation, i.e. Constant Output Voltage (COV) mode and Constant Output Current (COC) mode, in the presence of three aforementioned uncertainty sources is carried out. Subsequently, the frequency detuning as a function of the compensation capacitor variation is explored and broadened as a technique to obtain the optimized compensation capacitor value that can lead to a plant with minimized dynamic deviations from its nominal system in the operating range between COC and COV modes. As such, this approach offers a design procedure for a least conservative robust controller which can significantly improve the system performance. The optimized structure and the corresponding designed -synthesis controller are comprehensively elaborated.