A control method for a grid-connected inverter device

Abstract

The invention provides a grid connected inversion device. The grid connected inversion device comprises a DC power source, wherein the DC power source is connected with a power grid through an energy storage component and then through a DC-AC conversion circuit, the energy storage component comprises an energy storage inductor and an energy storage capacitor, the grid connection inversion device comprises a main control unit used for detecting a power grid voltage and controlling work states of the energy storage inductor and the energy storage capacitor, the DC power source is electrically connected with the DC-AC conversion circuit respectively through an upper electronic switch, the energy storage inductor and the energy storage capacitor, and the main control unit is used for controlling the work states of the energy storage inductor and the energy storage capacitor through controlling work states of the upper electronic switch and a lower electronic switch. Through physical rules of an induction device and the energy storage effect of the inductor, in combination with work state control of the electronic switches, a certain determined current value is directly generated, and thereby setting a corresponding current detection circuit and a corresponding current feedback loop is not required.

Description

technical field [0001] The invention relates to the field of new energy photovoltaics, in particular to a control method for a grid-connected inverter device. Background technique [0002] The grid-connected inverter is a device that converts the direct current output by the photovoltaic cell array (PV) into alternating current and outputs it to the grid. One of the requirements involved is that the phase of the output current is synchronized with the grid voltage, that is, the output current and the grid voltage must maintain a constant ratio within a cycle, so as to reduce the interference of the grid-connected inverter on the grid voltage. [0003] In order to meet the above requirements, the current method commonly used by grid-connected inverters is: the main control chip measures the grid voltage U, and sets a reference current I2 that is proportional to U according to the grid voltage U and the current reference output power P. Measure the output current I1 at the sa...

AI Technical Summary

Problems solved by technology

However, there is an obvious and important problem in the negative feedback network with integral function, which is that the time delay of the current feedback loop is relatively large, which in turn produces a phase difference between the output current I1 and the grid voltage U

When the grid voltage fluctuates greatly, the phase compensation network with integral function cannot respond correctly to the rapidly fluctuating voltage, resulting in obvious asynchronous phenomena between the current and voltage, and even current oscillations that aggravate voltage fluctuations

In order to reduce the fluctuation amplitude of the current when the voltage fluctuates, the inductance of the energy storage inductor must be increased, which in turn increases the operating loss of the inductor

[0004] On the other hand, the current of the switching circuit of this method is not zero at the beginning of PWM, resulting in the switching loss of the electronic switch and the reverse recovery loss of the circuit

[0005] Therefore, the above-mentioned various methods all have the problems of complex control circuit, high cost and low conversion rate, especially in the low-power grid-connected inverter application within 5KW, the economic benefit is not good

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