Three-level inverter model predictive power control method based on two-vector synthesis

Abstract

The invention discloses a three-level inverter model predictive power control method based on two-vector synthesis. The instantaneous active and reactive power of a grid-connected inverter is adjustedvia the model predictive power control based on two-vector synthesis, and a neutral-point voltage is balanced; the three-level inverter model predictive power control method based on two-vector synthesis is divided into two steps as follows: establishing two cost functions, firstly figuring out a small sector where an ideal voltage vector is located, then selecting two vectors through a reasonable cost function, and adjusting the duty ratio thereof to control switching elements of a three-level inverter. By adoption of the method, the switching frequency can be fixed, the calculation amount of the algorithm can be reduced, the computational resources can be saved, and the steady state and dynamic performance of the inverter controlled by the method are good.

Description

technical field [0001] The invention relates to the technical field of three-level inverter control, in particular to a three-level inverter model predictive power control method based on two-vector synthesis. Background technique [0002] With the increasingly severe environmental pollution and energy crisis, the distributed power generation technology using renewable energy such as solar energy and wind energy has received more and more attention. The inverter is the interface between the distributed generation system and the grid. Compared with the traditional two-level inverter, the three-level inverter has low harmonic content, small switching loss, and much higher power quality and efficiency. [0003] Model predictive control is a new type of predictive control strategy. This strategy needs to establish a system model that can predict future behavior. Usually, a cost function is constructed, and the optimal switch state that makes the cost function reach the minimum v...

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Problems solved by technology

These predictive control algorithms can balance the midpoint voltage of the three-level inverter, but the switching frequency of these two traditional methods is changing, and only one optimal voltage vector is selected as the voltage output in one switching cycle, and the switching state The change of the frequency is irregular, such an output has high requirements on the sampling frequency and the switching frequency is not fixed, and the harmonic spectrum is wide, which brings difficulties to the design of the output filter

At present, direct power control and modulation model predictive control strategies for inverters have been proposed to predict the optimal switching sequence. These two methods can achieve a fixed switching frequency, but the amount of calculation is large, and the switching state used within a switching frequency There are 3, resulting in an increase in the number of switching states of the inverter

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