Sequential model prediction control method for reducing switching loss of grid-connected inverter

Abstract

In order to reduce the switching loss of a T-type three-level LCL-type grid-connected inverter and realize multi-objective optimization of the inverter, sequential model prediction control is adopted. According to a sequential model prediction control method, a switching loss model of a T-type three-level inverter is established based on analysis of an output current path of the inverter under different switching state conversion. In order to reduce the number of weight factors when multi-objective optimization is realized by utilizing predictive control, cost functions of all levels are distributed for midpoint potential balance, current (grid side and inverter side), capacitor voltage tracking error and switching loss by adopting sequential model predictive control, and enter a three-layer prediction controller in sequence according to the priorities of the four optimization targets, so as to obtain a comprehensive optimal switching vector as a driving signal of the inverter. According to the sequential model prediction control method, the switching loss of the inverter is greatly reduced, the system efficiency is improved, and meanwhile, the neutral-point potential balance, resonance peak suppression and high-quality grid-side current output performance are ensured.

Description

technical field [0001] The invention belongs to the technical field of reducing the switching loss of a grid-connected inverter, and in particular relates to a sequential model predictive control method for reducing the switching loss of a grid-connected inverter. Background technique [0002] At present, distributed power generation systems based on new energy sources need to use grid-connected inverters to invert DC power into AC power that meets grid-connected requirements. T-type three-level inverter has been more and more used in engineering because of its high-quality current output performance and lower conduction loss in medium and low voltage systems. Compared with the traditional diode NPC topology, the T-type three-level inverter does not need to add diodes to clamp the midpoint voltage, which not only reduces the volume of the inverter, but also improves the system reliability. In addition, since the active damping LCL filter can avoid the use of filter resistor...

AI Technical Summary

Problems solved by technology

When reducing the loss based on the SVPWM algorithm, it is necessary to analyze the amplitude and phase of the corresponding current during modulation, and the design process is complicated

In addition, if multi-objective optimization (such as: current quality, midpoint voltage balance, filter resonance suppression) is performed on the T-type three-level on this basis, the algorithm for changing the modulation will be limited

Using the traditional MPC algorithm to reduce the loss, although the process is simple, but the traditional MPC controller involves the design of multiple weight factors, this process is complex and full of uncertainty

For the T-type three-level grid-connected inverter system under the active damping filter, it is necessary to consider the four objectives of grid-connected current quality, midpoint voltage balance, active damping filter resonance peak suppression, and inverter loss, then At least three weighting factors need to be designed, which is a very challenging process

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