Research On 400Hz Dynamic Voltage Corrector

The centralized power system is a developping aircraft external power supply, which has advantages of simple structure, convenient installation, high reliability and high efficiency. However, the voltage sag caused by the cable impedance can not be ignored in the centralized power supply system, which even makes the output voltage unable to meet the power standard. Moreover, short-circuit fault isolation among loads must be considered to improve the reliability of power supply.Based on the traditional dynamic sag corrector(DySC) and its derivative topologies, a new-type dynamic voltage corrector(DVC) with the short-circuit fault isolation is proposed. The DVC is composed of a grid-side converter and a load-side converter. The grid-side converter adopts the bidirectional AC-DC half-bridge topology to realize the bidirectional transmission of the energy, and the load-side converter is the neutral point clamped(NPC) three-level half-bridge topology, which is connected to the grid in series to compensate the transient voltage fluctuations.The detailed analysis of the DVC principle is presented to understand the working modes of two converters when input voltage is normal, sag, swelling and short-circuit fault occurs. Furthermore, the corresponding equivalent models are also established. The independent control strategy of two converters and the control parameter design method are studied with the same phase compensation strategy. And the feasibility of short-circuit fault isolation with filter inductor current limiting control is researched. Moreover, short-circuit current limiting operations under different grid voltages are compared. Finally, a protection mechanism based on software and hardware is designed to improve the reliability of DVC under short-circuit fault.Based on the analysis above, a 3kVA experimental prototype is designed. The simulation and experiment results show that the DVC has the ability to compensate the grid voltage mutation with desirable stable and dynamic performance as well as to limit the short-circuit current promptly, which is consistent with the theoretical analysis.