MMC apparatus sub-module capacitor voltage balance method by adopting model predictive control

Abstract

The invention discloses an MMC apparatus sub-module capacitor voltage balance method by adopting model predictive control. The balance method specifically comprises the following steps: step 1, a system-level main control CPU obtains each phase of control signals of an MMC main circuit; step 2, a phase-control circuit divides sub modules into a discharging group, a charging group and an undifferentiated treatment group according to voltage levels; and step 3, the finally input sub modules are determined in a pulse allocation link, and corresponding trigger pulse is generated; and after the trigger pulse passes through a driving circuit, a PWM signal is generated for controlling on-off of a corresponding switching device IGBT, so as to complete sub-module capacitor voltage grouping type model predictive control of the MMC apparatus. By adoption of the balance method, the nonlinear characteristic of the MMC system is maintained while the sub-module capacitor voltage control of the MMC system is effectively ensured as well, the control precious of the system is remarkably improved, burden of a processor is reduced, and the calculated amount of the existing model predictive technology can be reduced to the maximum extent.

Description

technical field [0001] The invention belongs to the technical field of power transmission and distribution control, and in particular relates to a method for balancing the capacitor voltage of a submodule of an MMC device using model predictive control. Background technique [0002] Since the new energy represented by photovoltaic power generation has the characteristics of dispersion and intermittency, if it is connected with conventional high-voltage direct current transmission technology, it will affect the grid-connected stability of the power system and cause power fluctuations. Therefore, in order to connect new energy to the grid in an economical, environmentally friendly, and reliable manner, and improve the regional optimal allocation capability of new energy, it is necessary to develop safe, reliable, and high-efficiency flexible DC transmission technology. [0003] The light direct current transmission (VSC-HVDC) system based on the voltage source converter (VSC-H...

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Problems solved by technology

[0016] (2) In order to reduce the huge amount of calculation brought by MPC, only one control objective is introduced. Compared with traditional PR or PI control, although the transient performance of the system is effectively improved, other performances are difficult to guarantee

[0017] (3) Predict the optimal control mode of the system according to different switch state combinations. Although the amount of calculation is reduced to a certain extent, the design is too complicated as the number of sub-modules increases.

[0018] In summary, using the model prediction method to realize the effective control of the MMC system and balancing the DC side capacitor voltage of the sub-modules can effectively improve the transient performance and steady-state control accuracy, but with the increasing number of sub-modules, the processor Put forward more stringent requirements, it is difficult to realize in the actual system

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