Multi-step model forecast control-based circulation control method of modular multilevel converter (MMC)

A technology of model predictive control and circulation control, which is applied in the direction of output power conversion device, AC power input conversion to DC power output, electrical components, etc., to achieve the effects of suppressing harmonic current, reducing the number of cycle predictions, and reducing the amount of calculation

Active Publication Date: 2017-09-08
HUNAN UNIV
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Problems solved by technology

[0004] The technical problem to be solved by the present invention is to propose a MMC (modular multilevel converter, MMC) circulation control method based on multi-step model predictive control for the harmonic circulation problem existing in the topology structure of the modular multilevel converter, On the basis of realizing optimal control, the additional computational complexity brought by multi-step prediction to the processor is reduced, and the effective control of harmonic circulation is finally completed

Method used

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  • Multi-step model forecast control-based circulation control method of modular multilevel converter (MMC)
  • Multi-step model forecast control-based circulation control method of modular multilevel converter (MMC)
  • Multi-step model forecast control-based circulation control method of modular multilevel converter (MMC)

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Embodiment Construction

[0039] figure 1 It is a block diagram of the modular multilevel converter used in the present invention. Use Kirchhoff's voltage law (KVL) and Kirchhoff's current law (KCL) to establish the circuit equation:

[0040]

[0041]

[0042]

[0043] where u pj and u nj are the output voltages of the upper and lower bridge arms of phase j (j=a,b,c) respectively, i pj , i nj , i diffj and i j are the upper and lower arm currents of phase j and the circulating current and output AC current of phase j respectively, L arm , L s , R s respectively represent the bridge arm inductance, AC side inductance and AC side resistance, U dc Indicates the DC side voltage, u c Indicates the sub-module capacitor voltage, C sm Indicates the sub-module capacitance, and the number of modules in each bridge arm is N. Combining formulas (1) and (2), we can get:

[0044]

[0045]

[0046] For formulas (3), (4) and (5), using Euler's forward formula, after discretization in turn, ...

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Abstract

The invention discloses a multi-step model forecast control-based circulation control method of a modular multilevel converter (MMC). The circulation control method comprises the following steps of firstly, performing dead beat control by an AC output current of the MMC to obtain reference input module numbers of an upper bridge arm and a lower bridge; secondly, performing single-step circulation forecast by combining a circulation current discrete state equation; thirdly, selecting the input module number conforming to a single-step forecast effect, and performing multi-state circulation forecast; and finally, solving an optimal solution of the bridge arm input module number, and achieving multi-step optimal control of a circulation current so that a harmonic current in the circulation current is effectively suppressed. The circulation control method comprises AC dead beat control, circulation single-step forecast and circulation multi-step forecast. Aiming at the circulation harmonic current of the MMC, a multi-step forecast finite control set is built by a multi-step model forecast control method according to the optimal solution obtained by single-step forecast, the cycle forecast frequency required by multi-step forecast can be substantially reduced, and the calculation quantity of a controller is effectively reduced.

Description

technical field [0001] The patent of the present invention relates to a MMC circulation control method based on multi-step model predictive control. Background technique [0002] Modular multilevel converters have the advantages of modular design, high efficiency, and low harmonic output. Extensive research. The particularity of the structure of the modular multilevel converter makes the suppression of interphase circulation and the stability of the capacitor voltage of the sub-module become the difficulties of various control methods. [0003] As an advanced nonlinear control optimization method, model predictive control does not need to adjust the control parameters. It has fast dynamic response and can eliminate the nonlinear influence brought by the system itself. It has great advantages in dealing with nonlinear constrained multi-objective optimization problems. Advantage. The finite control set model predictive control (finite control set MPC, FCS-MPC) method is to ...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/483
CPCH02M7/483H02M1/007H02M7/4835
Inventor 罗安郭鹏何志兴徐千鸣岳雨霏王霞
Owner HUNAN UNIV
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