Model Predictive Control Method and System for Parallel Converter Based on Virtual Capacitor

Abstract

The invention belongs to the field of predictive control of AC micro-grids, and provides a model predictive control method and system for parallel converters based on virtual capacitors. Among them, the control method includes obtaining the output reactive power of the converter, and comparing it with the reference reactive power; according to the comparison result of the output reactive power and the reference reactive power, automatically adjusting the reactance of the virtual capacitor; wherein, the virtual capacitor is connected in series Or connect in parallel to each parallel converter circuit; the current output by the virtual capacitor is controlled by the droop control and the virtual impedance loop to make a difference to obtain the reference voltage of the prediction model; the reference voltage of the prediction model is used as the input of the prediction model control , optimize the corresponding cost function in the predictive model control strategy, and obtain the optimal switch combination corresponding to the minimized cost function, so as to optimally control the converter and enable it 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

Images