Synchronization Phenomena in Microgrids With Capacitive Coupling

Multiple converters connected to a microgrid must have the same clock frequency, else interaction among the frequencies may cause beating noise. But the frequency equalization is difficult to achieve in practice. We show that the nonlinearity present in all power electronic systems offers an interesting possibility: the clocks may synchronize spontaneously if appropriate coupling exists among the converters. We further show that if the control circuits of the converters receive their power supply from the intermediate bus of the microgrid, the small ripple voltage across the intermediate bus capacitor can cause minute changes in the frequencies of the clocks-which may result in synchronization of the converters. The desirable periodic synchronization is achieved over specific ranges of the intermediate bus capacitance that depend on the frequency ratios of the converters in the uncoupled state.