Modular multilevel converter circulating current suppression method

Abstract

The invention discloses a modular multilevel converter circulating current suppression method, and relates to a flexible direct current transmission field of a power system. A hybrid particle swarm optimization algorithm is adopted to optimize PI parameters of a PI controller, a closed loop control circuit is composed of the PI controller and a controlled object, the PI controller outputs the input of the controlled object, the controlled object outputs the output of the system, the output of the system is sent to the input end of the system to form negative feedback, and is subtracted from the input of the system to generate a system error, and the error is sent to the PI controller. An objective function is constructed by the system error and the output of the PI controller, the hybridparticle swarm optimization algorithm is used for finding optimal PI parameters, the system dynamically adjusts the output and input to optimize the objective function, and when the objective functionis optimal, the parameters obtained through optimizing of the hybrid particle swarm optimization algorithm are the optimal PI parameters; the circulating current suppression method has high circulating current suppression precision, fast response and strong adaptability, can adjust the controller parameters according to the system dynamically, reduces the loss, and improves the overall steady state operation efficiency.

Description

technical field [0001] The invention relates to the field of flexible direct current transmission of power systems, in particular to a method for suppressing circulation of a modular multilevel converter. Background technique [0002] As a new type of voltage source converter, modular multilevel converter (MMC) has strong integrity and flexibility. MMC can be extended to any number of levels, and the output voltage waveform has less harmonic content, which is conducive to reducing the switching frequency of power devices and output filter capacity, reducing loss and improving efficiency. MMC not only effectively improves the application of converters Voltage and power levels, and has a common DC bus, which can realize independent control of active power and reactive power decoupling. These characteristics make MMC widely used in high-voltage direct current transmission, static var compensation and other fields. [0003] Such as figure 1 As shown, the three-phase MMC is com...

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Problems solved by technology

[0005] However, the above-mentioned patents use the trial and error method to debug the PI parameters. Since the mathematical model of MMC is nonlinear, discrete and high-order, and contains a large number of nonlinear components such as power electronic switches and capacitors, the trial and error method It is difficult to apply, so it is necessary to select appropriate PI control parameters to suppress the circulation and increase the design efficiency of the system controller

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