Loss optimization control method for modular multilevel converter under voltage imbalance
A modular multi-level, voltage unbalanced technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve the problem of increasing the output voltage distortion of modular multi-level converters rate, increasing the control difficulty and difficulties of modular multilevel converters, etc.
Active Publication Date: 2021-09-14
SOUTHEAST UNIV
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[0004] Aiming at the loss optimization control problem of modular multilevel converters, the conventional method optimizes the modular multilevel converter by optimizing the topology of the sub-modules, optimizing the capacitor voltage balance strategy of the sub-modules, or optimizing the modulation strategy of the modular multilevel converter. level converter loss, but the above method has the disadvantages of increasing the control difficulty of the modular multilevel converter and increasing the output voltage distortion rate of the modular multilevel converter, and there are certain difficulties in practical application
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[0043] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without creative efforts fall within the protection scope of the present invention.
[0044] Aiming at the loss optimization control problem of modular multilevel converters, the present invention proposes a loss optimization control method for modular multilevel converters under unbalanced voltage, in which the topological structure of three-phase MMC and sub-modules is as follows figure 1 , figure 2 As shown, the three-phase MMC is composed of six bridge arms, and each bridge arm contains n (n=1, 2, ..., N) submodules (Submodule, SM) with the sam...
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The invention discloses a loss optimization control method for a modular multilevel converter under voltage imbalance. The method comprises the following steps of: monitoring the current of each phase of upper bridge arm, the capacitor voltage of each sub-module of each phase of upper bridge arm and the switching device state of each sub-module of each phase of upper bridge arm in real time; calculating the loss of each sub-module of each phase of upper bridge arm by using the bridge arm current, the capacitor voltage and the switching states; calculating to obtain the total loss of the each phase of upper bridge arm; calculating to obtain a total loss average value of three-phase upper bridge arms; calculating to obtain the average value of the total loss of the three-phase upper bridge arms and the difference value of the total loss of each phase of upper bridge arm, and changing the carrier frequency of each phase of bridge arm to realize the same total loss of each phase of upper bridge arm so as to achieve the purpose of loss optimization control of the modular multilevel converter. By changing the carrier frequency of each bridge arm, the loss optimization control of the modular multilevel converter is realized. Compared with a conventional method, the control method of the invention does not need to increase construction cost of the modular multilevel converter, just slightly influences the quality of output electric energy and is relatively simple in the design of a control algorithm.
Description
technical field [0001] The invention belongs to the field of multilevel power electronic converters, and in particular relates to a loss optimization control method of a modular multilevel converter under unbalanced voltage. Background technique [0002] Modular Multilevel Converter (MMC) is a converter topology in which the bridge arm is cascaded by sub-modules. The sine wave method has the advantages of high waveform quality, strong fault handling ability, and low manufacturing difficulty. It has a wide application space in medium-voltage applications such as new energy grid connection and motor drive. [0003] Due to the fact that the AC side voltage of the modular multilevel converter is often unbalanced in actual operation, when the modular multilevel converter is unbalanced, the power switches and The loss generated by the diode will deviate, which will lead to a large difference in the service life and failure rate of the switching elements of the three-phase bridge ...
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IPC IPC(8): H02M7/5387H02M1/088H02M1/32
CPCH02M7/53871H02M1/088H02M1/32
Inventor 邓富金王梦悦赵纪峰
Owner SOUTHEAST UNIV