Grid connected inverter control method with network voltage feedforward lag compensation under weak power grid

Abstract

The present invention discloses a grid connected inverter control method with the network voltage feedforward lag compensation under a weak power grid. Aiming at a grid connected inverter stability problem caused by the network voltage direct feedforward on the weak power grid condition, the present invention provides the control method of the network voltage feedforward lag compensation. The method guarantees the situation that the fundamental wave gains of a grid connected inverter and the network voltage direct feedforward control are same in a manner of adding a low-pass filtering link in a network voltage feedforward channel, realizes the astable error tracking of a fundamental wave, not only can inhibit a power grid background harmonic wave, but also enables the phase margin of the grid connected inverter to be increased greatly on the weak power grid, and enables the power grid adaptability of the grid connected inverter to be improved.

Description

technical field [0001] The invention relates to a control method for a grid-connected inverter system, in particular to a control method for a grid-connected inverter with grid voltage feed-forward lag compensation under a weak grid. Background technique [0002] With the rapid development of distributed power generation systems, grid-connected inverters are widely used. In remote distributed power generation systems, the presence of long-distance transmission lines and a large number of transformer devices will bring a non-negligible equivalent impedance to the grid, making the grid show weak grid characteristics. In the case of a weak grid with high impedance, a dynamic interconnection system will be formed between the inverter and the grid. decline, affecting its control stability. The grid-connected inverter adopts the grid voltage direct feed-forward control, which can effectively compensate the current harmonics caused by the grid background harmonics, and thus has b...

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Problems solved by technology

[0006] (1) For the situation of weak grid, the method of direct feed-forward control of grid voltage in the existing literature will cause the stability of grid-connected inverter to be greatly reduced, and the system stability can be improved by reducing the feed-forward gain of grid voltage, but this method It will reduce the fundamental wave gain and increase the steady-state error between the grid-connected current feedback value and the command value, which is not conducive to fundamental wave tracking;

[0007] (2) None of the existing control schemes based on grid voltage feedforward involves adding a low-pass filter to the grid voltage feedforward channel to form grid voltage feedforward lag compensation to achieve grid-connected stability of the inverter

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