Improved switch coupling inductance quasi-Z-source inverter

Abstract

The invention belongs to the technical field of DC-AC conversion equipment, and relates to an improved switch coupling inductance quasi-Z-source inverter. The main structure comprises a DC power supply, a first inductor, a first capacitor, a first diode, a second diode, a third diode, a second capacitor, a third capacitor, a first winding, a second winding, a third winding, a fourth winding and six power switch tubes. Wherein the second diode, the third diode, the third capacitor, the first winding, the second winding, the third winding and the fourth winding form a boosting unit; the first winding, the second winding, the third winding and the fourth winding are coupled in pairs and are coupled in the same direction, the unique connection mode among the dotted terminals of the four coupling inductors can effectively reduce the current stress of the windings, reduce the loss and reduce the resonance problem of a converter circuit, and the output efficiency is high.

Description

Technical field: [0001] The invention belongs to the technical field of DC-AC conversion equipment, and relates to an improved switch-coupled inductance quasi-Z source inverter (MSCL qZSI). Background technique: [0002] Since the 21st century, with the increasingly severe energy crisis and environmental pollution, the rapid development of renewable and clean energy has become the focus of energy development in all countries in the world. Renewable and clean energy such as solar energy, wind energy, water energy, and nuclear energy have been widely used. The photovoltaic system based on solar energy has attracted widespread attention from all over the world due to its advantages such as no pollution, no noise, and rich development resources, and has been designated as the most promising in the future. The promising new energy technology has been widely used in various fields of industrial production and national economy. Among them, the voltage source inverter, as the most ...

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Problems solved by technology

Although this method can achieve higher conversion efficiency, it also has great disadvantages: first, it requires a higher input voltage, and multiple photovoltaic modules must be connected in series, which will greatly increase the system cost and failure rate and lead to Second, in actual work, in order to track the maximum power point voltage of the photovoltaic cell, the DC bus voltage of the inverter needs to fluctuate within a wide range, which leads to an additional increase in the power capacity of the inverter during design

A DC / DC circuit with maximum power point tracking function is added between the photovoltaic module and the inverter, and the DC circuit can be used to boost the voltage to reduce the number of photovoltaic modules in series and obtain a constant DC link voltage to realize the parallel operation of the inverter. Independent control and tracking of the maximum power point of photovoltaic cells when the network is working, but there are also some disadvantages: first, the addition of a DC-DC converter leads to a decrease in the efficiency of the entire system; second, the increase in the number of hardware circuits in the system reduces the reliability of the system. , increasing its maintenance cost

The development of single-chip photovoltaic module capacity has promoted the rapid development of micro-inverter grid-connected systems. High-voltage gain ZSI is very suitable for such application scenarios. However, experimental research has found that traditional ZSI also has some shortcomings: First, it is limited by its own topology. structure, its voltage gain is low; second, its input side current is discontinuous; third, the voltage at both ends of the energy storage capacitor is relatively large; fourth, there are problems of starting inrush current, common mode noise, etc.

Hafiz Furqan Ahmed, HonnyongCha and others proposed SCL qZSI, in which the bootstrap capacitor and symmetrical parallel structure are used to improve the boosting capability at a small direct duty cycle D, and the symmetrical parallel structure can reduce the current stress of the components. In addition, , the third winding N23 added in the coupled inductor improves the boost capability of the inverter, however, the copper loss in the winding reduces the efficiency in the non-shoot-through state

The mSSCL qZSI proposed by SaeedSharifi and Mohammad Monfared achieves a high voltage gain at small D by using a bootstrap capacitor and a switch-coupled inductor unit, however, the third winding N23 of the switch-coupled inductor has a high High current stress leads to high copper loss of coupled inductors, which in turn reduces inverter efficiency

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