Multiplexing all-soft switching AC-DC input solid-state transformer circuit and modulation method thereof

Abstract

The invention discloses a multiplexing all-soft switching AC-DC input solid-state transformer circuit and a modulation method thereof. The circuit comprises an input filter inductor, n front-stage full-bridge circuits, n auxiliary branch circuits and n rear-stage isolated DC-DC converters, wherein each front-stage full-bridge circuit, each auxiliary branch circuit and each rear-stage isolated DC-DC converter are successively connected in series to form a sub-module circuit; the input of the n sub-module circuits are connected in series, and the output of the n sub-module circuits are connectedin parallel; an input end is connected to a medium-voltage alternating-current or direct-current power grid through the input filter inductor, and an output end is connected to a low-voltage direct-current power grid or load; the front-stage full-bridge circuits conduct SPWM modulation or PWM modulation according to alternating current and direct current characteristics of input power grid voltage; the rear-stage isolated DC-DC converter adopts PWM modulation; phase shift exists between carriers of the n sub-module circuits; and according to the polarity of input current, the falling edges ofthe original driving signals of the front-stage full-bridge circuits are aligned with the falling edges of the original driving signals of the rear-stage isolated DC-DC converters, and soft switchingmodulation is performed on the aligned driving signal to generate a driving signal of the sub-module circuit.

Description

technical field [0001] The invention belongs to the technical field of power electronics technology, relates to a solid-state transformer and soft switch technology, and in particular to a solid-state transformer circuit and a modulation method for multiplexed full-soft switch AC and DC input solid state transformers. Background technique [0002] With the development of power electronics technology, solid-state transformers have received extensive attention. In addition to traditional transformer isolation and voltage step-up and step-down functions, solid-state transformers also integrate functions such as grid reactive power regulation, power control, harmonic suppression, and fault protection. ; In addition, the solid-state transformer can greatly reduce the volume and weight of the transformer and increase the power density; not only that, the use of a modular structure can greatly improve the withstand voltage level and power capacity of the solid-state transformer, and...

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Problems solved by technology

[0003] However, at present, there are few studies on solid-state transformers for AC and DC grid input; and compared with traditional transformers, the efficiency of solid-state transformers is still low, mainly because in two-stage solid-state transformers, the pre-stage circuit often works in hard Under the condition of switching, the post-stage isolated DC-DC converter also has the problem that soft switching is difficult to realize under light load, which increases the switching loss of the solid-state transformer and limits the conversion efficiency of the solid-state transformer; therefore, it is necessary to propose A solid-state transformer with universal AC and DC input that can realize soft switching of the front and back stages of the circuit at the same time

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