A Low Frequency Circulating Current Suppression Method for Modular Multilevel Converter with Carrier Laminated Pulse Width Modulation
A modular multi-level, pulse width modulation technology, applied in the direction of converting AC power input to DC power output, electrical components, output power conversion devices, etc., can solve problems such as inability to reflect, and achieve simplified hardware design and good output Voltage waveform, to ensure the effect of uniformity
Active Publication Date: 2020-04-03
扬州永茂电力建设有限公司 +1
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[0004] However, when this optimal modulation method is applied to a modular multilevel converter, because its influence on the low-frequency circulating current cannot be reflected in the modulated signal, the traditional low-frequency circulating current suppression strategy based on sub-module modulation signal correction will no longer be effective. Applicable, but the final pulse distribution must be redesigned to have low-frequency circulating current suppression
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[0023] The specific implementation manner of the present invention will be further described below in conjunction with the accompanying drawings and specific examples.
[0024] figure 1 It is a system structure diagram and a module unit structure diagram of the single-phase topology of the five-level modular multilevel converter used in the present invention. The single-phase topology is composed of upper and lower bridge arms, each bridge arm contains N sub-modules, and the switching function of each sub-module is σ jn (wherein, j is the code of the upper and lower bridge arms, j=u represents the upper bridge arm, j=l represents the lower bridge arm, n is the module unit sequence number in the bridge arm, and the value range is a positive integer from 1 to N), the module The voltage at both ends of the unit capacitor is U, and the upper and lower bridge arms each contain a current-limiting inductor with a value of L. The middle points of the upper and lower bridge arm induc...
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The invention relates to a low frequency ring current suppression method of a modularized multilevel converter under carrier stacked pulse width modulation. According to the low frequency ring currentsuppression method, on the premise that the output voltage level of a phase bridge arm is strictly equal to the level of a target waveform, a pulse distribution mode of a fixed route of an original state machine is improved reasonably, an appropriate redundant state is used adequately at a level moment affecting a ring current, changes of the ring current are always limited within the reasonablerange, the magnitude of low frequency ring current caused by capacitor voltage fluctuation of unit modules is suppressed effectively, and switch current stress of the unit modules is lowered. Meanwhile, according to the low frequency ring current suppression method, on the premise of not generating narrow pulses, uniformity and minimality of switching motions of the unit modules are maintained tothe maximum extent, and balance of capacitor voltage of the unit modules is not affected. In addition, according to the low frequency ring current suppression method, limiting frequency bands are appropriate to make sure that loss increasing of the unit modules is not caused by the frequent switching motions of the unit modules.
Description
technical field [0001] The invention belongs to the technical field of high-voltage and high-power power electronics, and mainly relates to a method for suppressing low-frequency circulating current of a modular multilevel inverter under carrier stack pulse width modulation. Background technique [0002] In recent years, due to its modularity, scalability, and redundancy, modular multilevel converters can be directly connected to high-voltage DC, and can use the public DC side to flexibly exchange power without affecting the AC system. received extensive attention from industry and academia. Therefore, the modular multilevel converter is not only applicable to HVDC transmission systems, but also suitable for medium and high voltage motor drives and medium voltage active filtering and other occasions. [0003] In these applications, the number of unit modules in each bridge arm of a modular multilevel converter usually does not exceed 20. Therefore, in order to obtain a more...
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IPC IPC(8): H02M7/483
Inventor 孙毅超吕丹丁楠木王琦
Owner 扬州永茂电力建设有限公司