Zigzag connection soft switching hybrid-type multi-level DC interconnection current transformer

Abstract

The invention discloses a zigzag connection soft switching hybrid-type multi-level DC interconnection current transformer and belongs to the technical field of intermediate and high voltage DC power transmission and distribution. The current transformer includes a bridge-type chopper, a power electronics capacitance bridge arm and two identical power electronics reactance bridge arms. Two bridge arms of the bridge-type chopper are each composed of two power electronics serial switch blocks connected in series. The positive electrode of the bridge-type chopper is connected to a high voltage positive electrode terminal of the current transformer while the negative electrode is connected to a high voltage negative terminal of the current transformer. The positive electrode of the capacitancebridge arm is connected to the high voltage positive electrode terminal of the current transformer while the negative electrode is connected to the high voltage negative electrode terminal of the current transformer. The positive electrodes of the two reactance bridge arms are connected to middle points of the two bridges arms of the bridge-type chopper respectively. The negative electrodes of thetwo reactance bridge arms are both connected to a low voltage positive terminal of the current transformer. According to the invention, a voltage-transformer-free non-isolation method is adopted forrealizing power conversion of different DC voltage levels, so that all switch devices in the power electronics serial switch blocks realize zero-current current transform soft switching, advantages ofhigh conversion efficiency, low loss, easy implementation of dynamic voltage sharing and high economic cost are achieved.

Description

technical field [0001] The invention belongs to the technical field of medium and high voltage direct current transmission and distribution, and in particular relates to an interleaved soft switch hybrid multi-level direct current interconnection converter, which has the capability of boosting and stepping down direct current conversion. Background technique [0002] At present, the power and voltage levels of high-voltage flexible direct transmission (VSC-HVDC) have reached hundreds of megawatts (MW) and hundreds of kilovolts (kV). From MW-level photovoltaic farms or DC integration of offshore wind power to the emergence of large-capacity DC energy storage systems and medium-voltage DC motor drives, there are interconnection requirements for DC transmission and distribution systems of different voltage levels. With the introduction of the concept of DC power grid, because it can meet the decentralized access of distributed energy sources and the demand for a large number of...

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Problems solved by technology

Among them, type 1) the current and voltage stress on the switching device is relatively large, and usually there is only one phase, resulting in large current ripple on the input and output sides, so it is not suitable for high-voltage and high-power applications; type 2) is the same as the isolated terminal pair Compared with the transformer capacity, the demand for the transformer capacity is reduced, and the utilization rate of the available capacity is also higher, but the loss is increased; type 3) the loss is lower, and the voltage and current stress are also smaller, but the IGBT used The number of devices and capacitors is large, and the cost is high

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