Composite virtual harmonic impedance control method for grid-connected inverter

Abstract

The invention provides a composite virtual harmonic impedance control method for a grid-connected inverter. The method mainly comprises the steps of: sampling the voltage of a grid-connected point of the inverter and calculating an active component V<PCCd> and a reactive component V<PCCq>; using a high-pass filter to extract V<PCCd_h> and V<PCCq_h>, and calculating order current harmonic parts i*<d_h> and i*<q_h>; calculating a direct current voltage error [delta]U<dc> and calculating an order current fundamental wave part active component i*<d_f>; and setting an order current fundamental wave part reactive component i*<q_f> as zero; and calculating inverter output voltages u, u and u<c>, and controlling the breakthrough and cutoff of a switch tube in a three-phase full-bridge inverter circuit via PWM. The composite virtual harmonic impedance control method of the invention is to simulate parallel branches of a resistance branch and a resistance-inductance branch at a harmonic wave frequency band by controlling the grid-connected inverter so as to suppress the distortion of grid-connected voltage VPPC caused by a harmonic source I<h> or power grid background harmonic wavea V<g>. Compared with a traditional resistor type virtual harmonic impedance control method for the grid-connected inverter, the composite virtual harmonic impedance control method has stronger system stability and better grid-connected voltage harmonic suppression capacity.

Description

technical field [0001] The invention relates to a compound virtual harmonic impedance control method of a grid-connected inverter, which belongs to the technical field of distributed grid-connected power generation. Background technique [0002] With the development of the country's industry and the improvement of people's living standards, various electrical loads with different characteristics are connected to the power grid, causing the voltage of the power grid to be distorted. The distortion of the grid voltage not only brings serious harm to the safe and reliable power supply of the power system, but also may damage the electrical equipment, which has a negative impact on human safety and economic benefits. [0003] Aiming at this problem, a common practice at present is to use an LC tuned filter or an active power filter (Active Power filter, APF) to compensate the grid harmonics. The compensation effect of the LC tuned filter is easily affected by the parameters of ...

AI Technical Summary

Problems solved by technology

Simulation and experiments prove that the resistance-type virtual harmonic impedance control method needs to virtualize a smaller harmonic resistance in order to achieve better distortion suppression effect, but the smaller harmonic resistance will cause the grid-connected inverter control system to be unsatisfactory. Stability, that is, there is a contradiction between the stability and the harmonic suppression effect of the resistive virtual harmonic impedance control

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