Two-stage frequency conversion control method of photovoltaic charger

Abstract

The invention relates to a two-stage frequency conversion control method of a photovoltaic charger. The photovoltaic charger comprises a BUCK circuit, a sampling unit, a control unit, a PWM drive unit and a man-machine interaction interface. The method is characterized in that the control unit realizes two-stage frequency conversion control while realizing MPPT maximum power control, and the two-stage frequency conversion control is realized specifically as follow: through the man-machine interaction interface, inputting a maximum open-circuit voltage value of a photovoltaic assembly; the control unit, according to the grade of the input voltage, setting the reference switch frequency of the PWM drive unit; and according to the grade of the input voltage of the photovoltaic charger, the control unit adjusting the set reference switch frequency of the PWM drive unit through the MPPT control and according to the change of the voltage of an actual input maximum power point at the same time. The method provided by the invention can be self-adaptive to the photovoltaic assembly with multiple input configuration modes, reduce the switch loss of the BUCK circuit, and improve the efficiency of the whole photovoltaic charger.

Description

technical field [0001] The invention relates to a two-stage frequency conversion control method for a photovoltaic charger. Background technique [0002] In a photovoltaic power generation system, a photovoltaic MPPT charger usually uses a BUCK step-down circuit to convert a higher voltage DC into a lower voltage DC to charge the battery. Due to the different configurations of photovoltaic modules in different photovoltaic power generation systems, the open-circuit voltage levels of photovoltaic modules connected to photovoltaic chargers are different; and under the same sunshine conditions, the open-circuit voltage of photovoltaic modules and the maximum power point voltage of photovoltaic modules will increase as the ambient temperature drops. , the output current is slightly reduced, so the input voltage range of the BUCK step-down circuit used by the photovoltaic MPPT charger is wider than that of the general BUCK circuit, ensuring that the charger using MPPT control is ...

AI Technical Summary

Problems solved by technology

[0012] The BUCK step-down circuit used in general photovoltaic MPPT chargers works in a fixed switching frequency mode. Under the same sunshine conditions, when the minimum temperature of the photovoltaic module is reached, V S Maximum, at this time the output ripple voltage △V O maximum, as the temperature increases, V S becomes smaller, at this time the switching frequency f S remains unchanged, the output ripple voltage △V O becomes smaller, but because the BUCK step-down circuit is a hard switching mode, there is a loss during the switching process of the switching tube, especially in the high frequency mode, the loss of frequent switching is greater

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