Dual active bridge type micro inverter and peak current control method and system

Abstract

The invention provides a dual-active bridge type micro inverter and a peak current control method and system. A peak current control mode comprises a single-degree-of-freedom control mode and a dual-degree-of-freedom control mode. In the single-degree-of-freedom control mode, the control degree of freedom is the moment when the secondary side square wave generating circuit starts to output the positive level, and the primary side square wave generating circuit does not have the control degree of freedom; under the control of two degrees of freedom, the degrees of freedom are controlled to be the moment when the primary square wave generating circuit starts to output zero level and the moment when the secondary square wave generating circuit starts to output positive level. In a peak current control mode, the primary side square wave generating circuit determines output through a clock signal, and the secondary side square wave generating circuit determines output through the relation between the secondary side current of the high-frequency transformer and the threshold current. According to the invention, the magnetic bias problem of the transformer caused by the dead zone of the switching tube is avoided; the design of the controller is more simplified; the switching loss can be reduced under the control of the two-degree-of-freedom peak current.

Description

technical field [0001] The invention relates to the technical field of photovoltaic micro-inverters, and in particular, to a dual-active bridge-type micro-inverter and a method and system for controlling peak current. Background technique [0002] Micro-inverter generally refers to an inverter with a power of less than or equal to 1000W in a photovoltaic power generation system and with the ability to track the maximum power point at the component level. Unlike centralized and string PV inverter systems, micro-inverters are directly connected to individual PV modules. The advantage is that each component can be independently controlled by MPPT, which can greatly improve the overall efficiency and avoid the DC high voltage, poor low light effect, and barrel effect of centralized inverters. [0003] According to the location and structural characteristics of the DC bus, micro-inverters can be divided into three categories: DC bus structure, pseudo-DC bus structure and no DC b...

AI Technical Summary

Problems solved by technology

[0007] First of all, this control method is only suitable for circuits based on SPWM modulation such as full-bridge non-isolated inverters, while dual-active bridge micro-inverters are based on phase-shift modulation, and need to switch the primary side and secondary side according to the transformer current. The tubes are all controlled, and its working principle is essentially different from the circuit to which the control method is applied;

[0008] Secondly, this control method can only reduce the grid-connected current waveform THD

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