Photovoltaic inverter harmonic suppression method based on improved PI+ repetition control

Abstract

The invention relates to the technical field of power systems, in particular to a photovoltaic inverter harmonic suppression method based on improved PI+ repetition control. The method comprises the following steps of S1, constructing a PI+ repetition controller model of an LCL type grid-connected photovoltaic inverter; S2, using a zero phase error feedforward compensation method, and adding the harmonic component feedforward control to a PI+ repetition controller. The method can enable the photovoltaic inverter to output high-accuracy harmonic current compensation through the repetition controller while using a PI controller to output a fundamental active power, consider that the repetition controller has the cycle delay and bad dynamic response, and add harmonic component feedforward control to speed up the dynamic response speed of harmonic suppression, thereby achieving the harmonic suppression function.

Description

technical field [0001] The present invention relates to the technical field of power systems, and more specifically, to a method for suppressing harmonics of photovoltaic inverters based on improved PI+ repetitive control. Background technique [0002] As the country vigorously promotes the development of new energy, the scale of photovoltaic grid-connected inverters has gradually expanded, and the extensive use of power electronic equipment has introduced harmonics to the power grid. The problem of harmonics is becoming more and more serious. If resonance is caused, it will endanger the safety of electricity consumption of the majority of users. [0003] At present, it is usually more economical to control harmonics to configure passive filters for lines, but passive filters can only control harmonic currents of corresponding frequencies, and a more efficient method is to use active filters for dynamic tracking compensation. However, this approach is more expensive. In vi...

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Problems solved by technology

For example, when extracting harmonic signals in the dq coordinate system, only the PI controller is used to compensate the tracking of the harmonic signals. Due to the limitation of the bandwidth of the traditional PI control, it is impossible to track the harmonic components at the harmonic frequency without static error. Wave suppression is limited

Aiming at the problem that PI control harmonics cannot keep up with only single-rotation coordinate transformation, some scholars have proposed a specified sub-harmonic current control strategy for multi-synchronous rotating coordinate systems, and some scholars have proposed to use fast Fourier transform to extract harmonic component amplitudes. Values ​​are used for PI control at each coordinate, and then the obtained control components are inversely transformed and superimposed to generate a total output current reference command. However, this method requires a large amount of calculation, and the number of specified harmonics controlled at the same time should not be too much

Aiming at the problem of multi-frequency characteristics of harmonic compensation, some scholars introduced repetitive control technology to eliminate periodic load harmonics, forming a composite control system of repetitive control and PI control, which can effectively control harmonics while reducing the amount of calculation. However, there is a cycle delay in the control component of its repetitive control part

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