LCL filter capable of adjusting resonant frequency automatically and working method of filter

Abstract

The invention discloses an LCL filter capable of adjusting resonant frequency automatically and a working method of the filter. The LCL filter capable of adjusting resonant frequency automatically comprises an inverter side inductor, a power grid side inductor, N groups of capacitors in parallel connection between the inverter side inductor and the power grid side inductor, and a controller connected to the N groups of capacitors in parallel connection and for controlling the switching number of the capacitors. Influence of electric reactance to the resonant frequency existing on a line can beeliminated by only adjusting the filtering capacitor values; the resonant frequency of the filtering circuit can be dynamically adjusted according to actual needs, and the resonant frequency can be kept within an APF normal operation safety range, so that the APF filtering effect is improved, thereby improving electric energy quality and ensuring power generation grid-connection stability; and byadopting controller to control switching of the capacitors, the filter is simple in structure, capable of lowering operational workload and cost, low in electrical collection amount in the realization process, good in filtering effect, and capable of improving grid-connection electric energy quality.

Description

technical field [0001] The invention relates to the field of power equipment, in particular to an LCL filter with an automatic adjustment of resonance frequency and a working method thereof. Background technique [0002] With the gradual depletion of fossil energy, photovoltaic power generation technology has been paid more and more attention by researchers because of its clean and renewable advantages; and photovoltaics emit direct current, which needs to be converted into alternating current acceptable to the grid through an inverter, while photovoltaic The main form of utilization is distributed power generation, which leads to high-order harmonic components generated by the switching elements of the inverter during the inverter process. Therefore, it is necessary to add a filter between the inverter and the grid to improve the power quality. The LCL filter is widely used because of its better filtering effect in the case of small inductance. There are three existing LCL ...

AI Technical Summary

Problems solved by technology

The new device (automatically adjust the resonant frequency LCL filter) can dynamically adjust the resonant frequency according to the actual filtering requirements, so as to ensure that the resonant frequency is always kept within the safe range of APF normal operation; it eliminates the influence of the reactance existing on the line on the resonant frequency; Eliminates the defect that a large amount of electricity needs to be collected in the existing "Grid-connected Inverter LCL Filter Parameter Design Method for Improving Weak Power Grid Adaptability"; improves the power quality requirements of distributed power generation, and reduces the workload of calculations , which simplifies the filter structure and reduces the cost

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