LCL type grid-connected inverter improved weighted average current control method

Abstract

The invention provides a LCL type grid-connected inverter improved weighted average current control method . The control method comprises the following steps: connecting an LCL type filter to the output end of a main circuit of the inverter; multiplying the current given value by the output phase information of the phase-locked loop to obtain a current reference signal, wherein the current reference signal obtains a control signal of the outer loop proportional resonance controller under the action of a feedback signal of the weighted average current of the LCL type filter; adopting a signal of a current signal output by the outer-loop proportional resonance controller under the action of a feedback signal of the filter capacitor current as a control signal of the inner-loop proportional controller, and adopting an output signal of the inner-loop proportional controller as a reference signal of the sine pulse width modulation controller; and adopting the sine pulse width modulation controller for controlling the conduction state of the switching tube of the main circuit. According to the invention, the damping coefficient of the control system is increased, the resonance of the LCL type filter is suppressed, the stability is ensured, and the power factor and the waveform quality of the grid-connected current are hardly influenced.

Description

technical field [0001] The invention relates to the technical field of photovoltaic grid-connected power generation, in particular to an improved weighted average current control method of an LCL grid-connected inverter. Background technique [0002] In photovoltaic grid-connected inverters, compared with L-type and LC-type filters, LCL filters are widely used in photovoltaic grid-connected inverters because of their good filtering effects. However, the LCL filter needs to adopt different damping methods to suppress it because of its resonance phenomenon. Common methods for suppressing resonance peaks by increasing damping include passive damping and active damping. Passive damping suppresses resonance phenomena by connecting resistors in series or in parallel at the C terminal of the filter capacitor. However, the series resistance at the C-terminal of the filter capacitor will weaken the high-frequency attenuation capability of the LCL filter. The larger the series resist...

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Problems solved by technology

[0006] Aiming at the technical problem that the traditional control system based on the weighted average current control method is an undamped system, which makes the control system in critical stability and poor stability, the present invention proposes an improved weighted average current of the LCL type grid-connected inverter. The control method, under the premise of ensuring low grid-connected current harmonics and high power factor, increases system stability and suppresses the resonance peak of the LCL filter

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