Alternating-voltage-sensor-free control method for inverter with frequency adaptive characteristic

Abstract

The invention provides an alternating-voltage-sensor-free control method for an inverter with the frequency adaptive characteristic. The method includes the steps that firstly, a quadrature filter with variable frequency is established for the zero-difference following characteristic of specific frequency alternating current signals through a second order generalized integrator, the quadrature filter is utilized to establish a voltage observer of the three-phase grid-connected inverter with the frequency adaptive characteristic, under a two-phase static coordinate system, measured power grid side current signals and inverter controller output bridge terminal voltage reference signals serve as input of the voltage observer, and then power grid voltages are observed; in combination with PR control of the three-phase grid-connected inverter under the two-phase static coordinate system, operational control over the inverter under the alternating-voltage-sensor-free condition is achieved. By the adoption of the method, under the condition that control stability of the inverter is kept, the problems of integral saturation, initial value sensitivity, static errors and the like probably existing in conventional alternating-voltage-sensor-free control are solved, and good adaptability is achieved when power grid voltage frequency changes.

Description

technical field [0001] The invention relates to a control method of a three-phase grid-connected inverter. Background technique [0002] The renewable energy grid-connected power generation system has developed rapidly in recent years. When it is connected to the end of the grid or the distribution network with a weak grid structure, there may be a small short-circuit capacity of the grid-connected point, poor stability of the grid, and serious problems in the grid. Problems such as voltage fluctuations, flicker, symmetrical or asymmetrical voltage drop faults, etc. The intermittence and randomness of renewable energy itself may further deteriorate the voltage stability of the connected power system, and in turn affect its own stable operation. In order to realize the grid-connected power and current control of renewable energy generation systems, the existing grid-connected converters or inverters generally use phase-locked loops to obtain grid voltage information, but thi...

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Problems solved by technology

[0008] The purpose of the present invention is to overcome the possible problems of zero point drift, integral saturation, steady-state error and initial value sensitivity in the existing inverter without AC voltage sensor control, and to make the inverter without AC voltage sensor control able to adapt to the grid frequency A three-phase grid-connected inverter control method without AC voltage sensor with frequency adaptive characteristics

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