Parallel converter model prediction control method and system based on virtual capacitor

Abstract

The invention belongs to the field of AC micro-grid prediction control, and provides a parallel converter model prediction control method and system based on a virtual capacitor. The control method comprises the following steps of acquiring output reactive power of the converter, and comparing the output reactive power with reference reactive power, automatically adjusting the reactance of the virtual capacitor according to the comparison result of the output reactive power and the reference reactive power, wherein the virtual capacitor is connected in series or in parallel to each parallel converter loop, respectively performing droop control and virtual impedance loop control on the current output by the virtual capacitor, and performing subtraction to obtain a prediction model reference voltage, and taking the prediction model reference voltage as the input of prediction model control, optimizing a corresponding cost function in a prediction model control strategy, and obtaining an optimal switch combination corresponding to the minimum cost function, so as to carry out optimal control on the converter and enable the converter to obtain equal or proportional reactive power sharing.

Description

technical field [0001] The invention belongs to the field of predictive control of AC microgrids, and in particular relates to a model predictive control method and system for parallel converters based on virtual capacitors. Background technique [0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art. [0003] The demand for renewable energy sources in power systems is growing rapidly. These renewable energy sources are also known as distributed generation (DG) because they can be located at multiple locations in a microgrid. DG usually requires voltage source conversion (VSC) to provide stable and safe power to loads connected to the microgrid. Droop control is an important method for power distribution in parallel VSCs. However, the mismatch of feeder impedance and droop coefficient of VSCs will lead to reactive power distribution errors among distributed VSCs connected in ...

AI Technical Summary

Problems solved by technology

For example, feeder current measurements are required for impedance estimation, distribution errors remain during load changes, and can lead to poor voltage regulation performance

[0005] The inventor found that when the VSCs are running in parallel, the existing droop control will lead to an error in the distribution of reactive power among the converters

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