A model predictive control method and system for three-level grid-connected converters

Abstract

This disclosure proposes a model predictive control method and system for three-level grid-connected converters, and proposes a new definition of switching cycle. By controlling the switching cycle and indirectly controlling the switching frequency, the fast transient state of the model predictive control method is maintained. At the same time, improving the objective function of predictive control and adding the switching frequency constraint item can make the spectrum of the output current similar to that of the pulse width modulation, realize spectrum shaping, and still track the reference current and balance the bus capacitor voltage well. , can greatly simplify the design of filters and heat sinks, and improve the life and reliability of the system.

Description

technical field [0001] The present disclosure relates to the related technical field of converter control technology, and in particular, relates to a model predictive control method and system for a three-level grid-connected converter. Background technique [0002] The statements in this section merely provide background information related to the present disclosure and may not necessarily constitute prior art. [0003] A grid-connected converter is a power conversion device that converts electrical energy from DC to AC and realizes feeding into the grid. The neutral point clamped three-level converter generates three levels through the neutral clamp and series DC capacitors. Compared with the two-level converter, at the same single-transistor switching frequency, it has a smaller The advantages of harmonic current, reverse voltage borne by switching devices on the bridge arm, and half switching loss are widely used in low-voltage 380V-690V photovoltaic, wind power and ene...

AI Technical Summary

Problems solved by technology

The first type of model predictive control method is based on the modulator-like pulse width modulation method, and the switching frequency is basically stable. Although the spectrum distribution is similar to the traditional pulse width modulation technology, it loses the advantages of model predictive control, especially in the bridge When the number of arms increases, the complexity of the control algorithm increases significantly, making it difficult to generalize

The second type of model predictive control method simply punishes the switching action, which reduces the average operating frequency of the switch to a certain extent. The notch filter can remove a large part of the harmonic components, but it does not solve the frequency spectrum of the current. The fundamental problem is that the distribution on the domain is not concentrated enough, which limits the average switching frequency and also reduces the current quality, and it is difficult to exert the physical limit of the switching device

The design is very complicated, and when the working conditions change, the relevant parameters need to be redesigned, which is inflexible

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