Passive backstepping control method for suppressing circulation of modular multilevel converter

Abstract

The invention relates to a passive backstepping control method for suppressing circulation of a modular multilevel converter. The passive backstepping control method comprises the steps of S1, obtaining an MMC circulation PCHD model by a single-phase equivalent circuit of an MMC according to a positive definite quadratic form energy function; S2, building a PCHD model-based MMC circulation suppression passive backstepping controller; S3, inputting a circulation double-frequency actual value and a reference value into the MMC circulation suppression passive backstepping controller so as to output circulation voltage compensation quantity; and S4, performing carrier phase-shift modulation on the circulation voltage compensation quantity, and controlling a switch tube in an MMC sub-module tobe switched on and switched off by a modulation wave so as to achieve the purpose of circulation suppression. Compared with the prior art, PCHD model-based passive control and a backstepping method are organically combined, global stability can be ensured, rapid and dynamic response also can be achieved, and moreover, the method has the obvious effects of simple control law algorithm, no singularpoint, high robustness and circulation suppression.

Description

technical field [0001] The invention relates to the control field of modular multilevel converters, in particular to a passive backstepping control method for suppressing the circulation of modular multilevel converters. Background technique [0002] At present, the modular multilevel converter (MMC) is widely used in the grid-connected system of the distributed power supply. The mathematical model of the MMC is simple. The switching of the output voltage can be realized, but since the MMC contains multiple sub-modules, with the switching in and out of each sub-module, it is difficult to achieve a complete balance of the capacitor voltage in the sub-module, causing the voltage imbalance between the bridge arms, and then forming a circulating current. [0003] In order to suppress the circulation generated during the operation of the MMC, the traditional vector control method does not start from the energy point of view, and cannot effectively control the nonlinear nature of ...

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Problems solved by technology

[0002] At present, the modular multilevel converter (MMC) is widely used in the grid-connected system of the distributed power supply. The mathematical model of the MMC is simple. The switch of the output voltage can be realized, but because the MMC contains multiple sub-modules, with the switching in and out of each sub-module, it is difficult to achieve a complete balance of the capacitor voltage in the sub-module, causing the voltage imbalance between the bridge arms, and then forming a circulating current

[0003] In order to suppress the circulation generated during the operation of the MMC, the traditional vector control method does not start from the energy point of view, and cannot effectively control the nonlinear nature of the MMC. Once there is an uncertain disturbance, the traditional vector control will face disturbance immunity and robustness. Although the existing nonlinear control method solves the problem of nonlinear control to a certain extent, it has deficiencies in energy optimization. The energy loss of the system is too large, and its transient performance is poor, and the adjustment time is too long. Long, slow dynamic response

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