A method for active voltage regulation control of a voltage equalizing converter

Abstract

The invention proposes an active voltage regulation control method for a voltage equalizing converter, which is suitable for flexible direct current transmission and distribution networks, new energy grid connection, energy Internet and other fields where bidirectional isolated DC power electronic transformers with voltage equalizing converters are used . The active voltage regulation control method of the voltage equalizing converter proposed by the present invention endows the voltage equalizing converter with the ability to adjust the voltage and improves the control flexibility; the present invention optimizes the switching frequency of the proposed active voltage regulating control method of the voltage equalizing converter Select, further improve the transformation efficiency under the dc power electronic transformer fault redundancy working condition; the active voltage regulation control method of the voltage equalizing converter proposed by the present invention can maintain the LLC input voltage constant when the dc power electronic transformer fault redundancy, thereby improving The output voltage adjustment capability of the DC power electronic transformer under the fault redundancy working condition can reduce the parameter design difficulty of the LLC resonant converter at the same time.

Description

technical field [0001] The invention relates to an active voltage regulation control method of a voltage equalizing converter, which is suitable for flexible direct current transmission and distribution networks, new energy grid connection, energy Internet and other fields where medium and high voltage bidirectional isolated direct current power electronic transformers may be used. Background technique [0002] Power Electronic Transformer (PET), also known as Solid State Transformer (SST), is an electronic power device that replaces traditional transformers through high-frequency energy conversion technology. The power electronic transformer used for energy transmission and electrical isolation between two DC buses is also called DC Power Electronic Transformer (DCPET). DCPET is widely used in flexible DC transmission and distribution networks, new energy grid connection, energy Internet and other fields where medium and high voltage bidirectional isolated DC conversion may...

AI Technical Summary

Problems solved by technology

[0004] However, when the DCPET works in the failover mode, the input voltage of the DC / DC sub-module increases due to the reduction of the number of modules

If the voltage equalizing converter is still working in the voltage equalizing mode at this time, the input voltage of the LLC resonant converter will also rise and cause it to work in the buck mode, which will cause the following problems: First, the LLC resonant converter works in the buck mode The interval requires a wider voltage regulation and operating frequency range, which increases the difficulty of parameter design

According to the LLC gain characteristic curve, the switching frequency in the step-down range is higher than the resonant frequency, which brings difficulties to the design of magnetic components such as resonant inductors and transformers

Secondly, the switching frequency of the LLC resonant converter has an upper limit, and the output voltage cannot be effectively adjusted when the input voltage drops too severely.

Furthermore, when the LLC resonant converter works in the step-down mode, the turn-off loss of the primary switching tube increases, and the secondary rectifier diode loses the ZCS turn-off characteristic, resulting in an increase in the reverse recovery loss, and the increase in the switching frequency leads to an increase in the loss of the LLC resonant converter. Large, LLC resonant converters and DCPET efficiency drops severely

On the one hand, under the existing heat dissipation conditions, if the heat cannot be dissipated in time, it will reduce the service life of the switch or even cause system damage due to overheating; on the other hand, in order to ensure the heat dissipation conditions of the power switch, the radiator needs to have a stronger heat dissipation capacity , which means an increase in the size and cost of the radiator, which contradicts the improvement in power density and economy

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