MMC modulation method for AC/DC voltage quality optimization
A technology of AC and DC voltage and modulation method, 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 no longer exist, reduce excessive voltage fluctuation, etc. High effective switching frequency, optimized AC or DC voltage quality
Active Publication Date: 2021-06-08
BEIJING SIFANG JIBAO AUTOMATION +2
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Problems solved by technology
Since the voltage equalization is still performed by sorting during the entire modulation process, the problem of sub-module bypass exit caused by carrier phase shift no longer exists
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[0062] Next, a MMC AC voltage modulation method of the present invention will be described in detail with reference to the accompanying drawings and examples. The present invention combines the advantages of the two modulation methods in the prior art, and overcomes the disadvantages of these two control modes, and the optimized sorting modulation method is proposed, that is, on the basis of the conventional level approximation, the level is approximated. The remaining part abandon the traditional four-way approach, but to select the corresponding sub-module for PWM control, so that the precision output of modulation can be achieved in one cycle to achieve the purpose of reducing the harmonic distortion rate. Since the entire modulation is still equalized in the ordering mode, the problem when the sub-module bypass by the carrier transfer phase is not complexed.
[0063] Further, in order to prevent the power electronics from being treated, the upper and lower tubes in the same ha...
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The invention discloses an MMC modulation method for AC / DC voltage quality optimization. According to the MMC modulation method, the problem of large output voltage fluctuation caused by a dead zone when a large number of modules are switched at the same time during voltage sharing is solved through adopting a double-threshold voltage sharing algorithm; and switching between alternating-current voltage quality optimization and direct-current voltage quality optimization is realized by adjusting the relative phase of PWM carriers of an upper bridge arm and a lower bridge arm. The MMC modulation method introduces a double-threshold voltage-sharing method, two threshold values are utilized to control the sequencing output of the modules when the modulation output is not changed, when the maximum value of the voltage deviation of the modules is greater than a preset single-module switching secondary threshold value, switching of only one module is carried out, so that overlarge voltage fluctuation caused by a dead zone when a plurality of modules are switched at the same time is reduced, when the voltage deviation is greater than a preset full-sorting switching first-level threshold value, full-sorting switching is carried out, and the effect that the maximum value of the voltage deviation of the module is controllable is achieved.
Description
Technical field [0001] The present invention belongs to the field of DC distribution networks, and specifically, the present invention relates to an MMC modulation method for the optimization of DC voltage quality. Background technique [0002] Modular Multilevel Converter (MMC) is a basic device constituting a DC distribution network, an accurate and efficient modulation method is the basic condition of MMC stable and efficient operation. There are two modulation methods of MMC: Nearest Level Modulation (NLM) and Carrier PhaseShip SPWM, CPS-SPWM. [0003] The nearest level approximation modulation is mainly used in a large-scale sub-module in flexible DC transmission. Since there is a sufficient number of sub-modules, the adjustment of the amount of subunies can achieve good approximation effect, the power quality of DC voltage and current. It can meet the requirements, ie, has the advantages of simple calculation, equal pressure control, and convenience of module bypass. Howeve...
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Login to View More IPC IPC(8): H02M7/483H02M7/5387H02M7/5395
CPCH02M7/483H02M7/53871H02M7/5395
Inventor 王继慷王一马彦宾张浩李思刘树操丰梅梅红明王皆庆游涛王立超
Owner BEIJING SIFANG JIBAO AUTOMATION