Control method of single-phase two-stage photovoltaic grid-connected system

Abstract

The invention provides a control method for a single-phase two-stage photovoltaic grid-connected system. The control method comprises the following steps: when the system operates normally, a pre-monitor monitors the output voltage and the output power of a photovoltaic array to select a proper sampling frequency for sampling to obtain a voltage value and a power value of each sampling moment and transmits the values to an MPPT (maximum power point tracking) controller for calculation; under the control of an inversion circuit, a post-monitor transmits acquired data of the output power and the power grid voltage of the photovoltaic array to an inversion controller, and a phase signal, generated by the power grid voltage data, of reference current through a phase-locked loop is also input into the inversion controller, and the data are multiplied with the phase signal to obtain a reference current signal, and actual grid-connected current and the reference current generate corresponding PWM (pulse width modulation) through a comparator, a hysteresis process and a PID (proportion-integral-differential) process to control on and off of a switch tube of the inversion circuit. According to the control method, a good control effect on the single-phase two-stage photovoltaic grid-connected system is achieved, so that the maximum output power of the photovoltaic array is guaranteed, and the unit factor control of the inversion circuit can be also guaranteed.

Description

technical field [0001] The present invention relates to a control method, in particular to a control method for a single-phase two-stage photovoltaic grid-connected system. Background technique [0002] The electricity generated by the photovoltaic array is direct current, and it must be connected to the grid through an inverter. The DC output from the photovoltaic array can be directly connected to the inverter, which is the so-called single-stage control. Single-stage control can usually be used when there are power frequency transformers or when there are many photovoltaic arrays connected in series and parallel, and the control method is more complicated. For general photovoltaic arrays, two-stage control can be adopted, that is, through the DC / DC circuit first, and then connected to the inverter, the control can be greatly simplified. The normal operation of the two-stage photovoltaic grid-connected system should at least meet the following two conditions: (1) maintai...

AI Technical Summary

Problems solved by technology

[0003] The general two-stage photovoltaic grid-connected system control often has the problem of inaccurate maximum power point tracking, or poor inverter control unit power factor.

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