Investigation on uncertainty of resonant inverter system using multiple frequency modeling and Monte Carlo simulation

The uncertainties of component tolerance, noise and perturbations place challenge in the circuit and controller design of a resonant inverter. Furthermore, in a high frequency AC distributed power systems where multiple inverter modules are paralleled, tight control of phase angle is mandatory, in addition to magnitude and frequency. This is because individual inverter output voltage phase angle and magnitude are sensitive to certain circuit uncertainty, for instance, component tolerance. Possible discrepancy of the equivalent inverter impedance due to resonant network parameters, and the DC voltage sources lead to circulating current because of phase angle or magnitude difference among modules, which will deteriorate the system efficiency and stability. Based on a general circuit model, the probability of the output voltage amplitude and phase angle of a high frequency resonant DC/AC inverter is studied through Monte Carlo simulation. It is found the phases and magnitudes of the inverters are statistically distributed with Gaussian function. Among all the possible source of randomness, the tolerance of the resonant tank components is the major attributor for output phase angle uncertainty. It is further found that the probability density function of both the amplitude and phase angle of the output voltage changes with load conditions as well as input line voltage.