Asynchronous Startup of the Paralleled DC-DC Converters in DC Microgrid Based on the Injected Frequency

The droop control of DC-DC converters based on injected AC voltage small-signal realizes current sharing control without communication, but DC-DC converter startup fails when AC voltage amplitude, frequency and phase do not meet sufficient conditions. In order to improve the success rate of the DC-DC converter connected to the DC bus, an asynchronous startup strategy based on phase difference is proposed. The AC and DC voltage conditions of the DC-DC converter connected to the microgrid under the injected frequency droop control are analyzed, and the control function of the circuit breaker is designed by using the voltage signals on both sides of the circuit breaker. The small-signal model is used to analyze the frequency convergence characteristics of AC voltage under the asynchronous startup strategy. The hardware in the loop experiment based on Starsim shows that the asynchronous startup method based on phase difference can realize the smooth connection between the DC-DC converter and DC bus, and improve the dynamic performance of the connection process.