Modular multi-level half-bridge converter

Abstract

The invention discloses a modular multi-level half-bridge converter. Each bridge arm of the converter comprises N standard half-bridge sub-modules. Each standard half-bridge sub-module comprises a first switch and a second switch. In each upper bridge arm and from the direct current side to the alternating current side, the front N-1 standard half-bridge sub-modules all include a third switch; in each lower bridge arm and from the alternating current side to the direct current side, the front N-1 standard half-bridge sub-modules all include a third switch. In the upper bridge arm, the third switches of the standard half-bridge sub-modules are complementary and switching to the first switches of their adjacent lower-potential standard half-bridge sub-modules. In the lower bridge arm, the third switches of the standard half-bridge sub-modules are complementary and switching to the first switches of the module. According to the invention, while not reducing the rated voltage modulation ratio, the rated voltage modulation ratio increases greatly; under the same rated AC and DC, the number of sub-modules of each bridge arm is reduced, therefore, greatly reducing the production cost, minimizing the switch losses and reducing the real-time computational requirement for a control system.

Description

Technical field [0001] The present invention relates to the technical field of converters, in particular to a modular multilevel half-bridge converter. Background technique [0002] Modular multilevel half-bridge converters are mostly used in the field of medium and high voltage. In order to ensure the normal operation of the modular multilevel half-bridge converter, the voltage of the sub-modules in the modular multilevel needs to be balanced at the rated voltage nearby. Please refer to figure 1 with figure 2 ,among them, figure 1 Is a schematic structural diagram of a modular multi-level half-bridge converter in the prior art, figure 2 for figure 1 A structural schematic diagram of a standard half-bridge sub-module in a modular multi-level half-bridge converter is provided. The standard half-bridge sub-module consists of two switches in series and a stabilized capacitor connected in parallel at both ends of the switches in series. One switch includes an IGBT (Insulated Gate ...

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Problems solved by technology

[0004] However, this causes the switching frequency of the existing voltage equalization scheme to exceed the power frequency (Note: the power frequency switching frequency means that the switch is turned on and off once within 0.02 seconds), which is generally about twice the power frequency, resulting in replacement The switching loss of the inverter increases

At the same time, the control system is required to monitor the voltage of the sub-modules and the rotation of the standard half-bridge sub-modules in a short cycle, which has high requirements for the reliability and computing power of the real-time measurement and control system. Under the application of the control system, the computing power of the control system tends to become a bottleneck

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