Control method of quasi-Z source cascade multi-level single-phase photovoltaic grid generation system

Abstract

The invention discloses a control method of a quasi-Z source cascade multi-level single-phase photovoltaic grid generation system, wherein a quasi-Z source inverter is provided for each photovoltaic battery as a generation module; a plurality of modules are connected in series to form a quasi-Z source cascade multi-level single-phase photovoltaic grid generation system which integrates the advantages of the quasi-Z source inverter and the cascade multi-level inverter; with the adoption of the control method, for the system, a carrier phase shift SPWM (sinusoidal pulse width modulation) modulation method, distributed MPPT (maximum power point tracking) control, direct-current bus voltage control and grid power control are improved, the quasi-Z source cascade multi-level single-phase photovoltaic power generation system can be effectively operated, solar energy is collected in a maximum manner, and multi-level output voltage and boosting control are realized. Even if the voltage wide range of the photovoltaic battery is changed, the peak voltage of the direct-current bus of each module is constant, so that the condition that the capacity of the inverter is minimum is ensured, thereby the photovoltaic generation with low expenses, high efficiency and high reliability is achieved.

Description

technical field [0001] The invention relates to the technical field of photovoltaic power generation, in particular to a quasi-Z source cascaded multi-level single-phase photovoltaic grid-connected power generation system and a control method. Background technique [0002] Photovoltaic power generation is clean and environmentally friendly, has abundant reserves, is safe and reliable, and is one of the most promising new energy sources. The topology of power converters used in photovoltaic power generation systems is mainly characterized by single-stage or two-stage, two-level or multi-level. Among them, the cascaded multilevel inverter has many advantages, which are mainly reflected in the following goals: 1) no transformer; 2) small output voltage harmonics; 3) reduce or omit the filter at the output end; 4) distribute type maximum power tracking (MPPT); 5) easy to modularize. Therefore, the application of cascaded multilevel inverters to photovoltaic power generation sy...

AI Technical Summary

Problems solved by technology

However, due to the wide range variation of photovoltaic cell voltage, the traditional cascaded multi-level inverter system has the following problems in photovoltaic applications: first, there is a problem of DC bus voltage imbalance between different modules of the system; second, the system is designed Need to double the capacity of the inverter

However, the invention does not disclose specific control details, such as how to perform pulse width modulation to independently control all quasi-Z-source inverter modules, how to realize distributed maximum power tracking of each module, and how to maintain DC power of each module. Bus voltage balance control, etc.

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