Grid-connected inverter current control method employing inductance current weighted average value to feed back

Abstract

The invention discloses a current control method of a grid-connected inverter using weighted average value feedback of inductance current. Two current transmitters are used to respectively detect the current flowing through the series inductor on the inverter side and the series inductor on the grid side, and the two The weighted average value of the current is used as the feedback signal of the inverter output current control, which is compared with the control given signal of the grid current, and the error signal output after the comparison is input to the proportional integral regulator, and the output signal adjusted by the proportional integral is used as the inverter switch The running pulse width modulation signal controls the output current waveform and amplitude of the grid-connected inverter, and the weight of the two inductor currents in the feedback signal is the ratio of the respective inductance to the total inductance of the two inductors. The method of the invention can effectively enhance the resistance to grid distortion and harmonic interference, suppress grid current waveform distortion and harmonic content, and enable the grid-connected system to obtain higher power factor and good output current waveform.

Description

technical field [0001] The invention relates to a control method for a grid-connected inverter, in particular to a current control method for a grid-connected inverter that adopts the weighted average value feedback of inductance current. Background technique [0002] The inverter power supply with grid-connected power generation function, its circuit is as follows figure 1 As shown in (a) and (b), it usually includes PWM (pulse width modulation) based on high-frequency switching to control single-phase or three-phase inverters, LCL low-pass filters for inverter grid-connected operation, and for The current transmitter for current detection, the current control loop including current error calculation and error signal proportional integral regulator for inverter grid-connected operation, and the switch drive circuit. The inverter is output current control when it is grid-connected. To ensure that the current is a strict sine wave and has a high power factor of power generat...

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Problems solved by technology

Because the filter of LCL structure makes the control object a third-order system, there is a large gain peak near the corner frequency of the filter. In order to ensure the stability of the system, the gain of the proportional-integral regulator is limited and the value is small, so that the system is in The open-loop gain in the low frequency band is small, which limits the ability of the system to suppress output current steady-state errors and harmonics

This method is also susceptible to grid voltage distortion and harmonic interference

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