The Method of Controlling Background Harmonic by Parallel Impedance Device

Abstract

The invention discloses a method for governing a background harmonic wave by connecting an impedance type device in parallel. The method comprises the steps of: according to a reactive demand of a system where a bus is positioned, determining fundamental harmonic reactive compensation capacity of the impedance type device; according to a voltage class of the bus, determining a voltage borne by the impedance type device, and then according to required times for filtering out the harmonic wave and the fundamental harmonic reactive compensation capacity of the impedance type device, calculating a total capacitive reactance of a capacitor bank and an inductive reactance of an electric reactor in the impedance type device; determining a capacitive reactance of a single capacitor, then according to a bus voltage, the capacitive reactance of the capacitor bank and the reactive compensation capacity, determining a serial and parallel connection mode and a branch number of each capacitor in the capacitor bank so as to obtain a structure of the impedance type device; and connecting the obtained impedance type device onto the bus in parallel so as to implement government on the background harmonic wave. According to the method, content of the voltage of the background harmonic wave on the load bus can be greatly reduced, so that the adverse effect of the background harmonic wave on safe and stable operation of electric equipment under the load is reduced or improved.

Description

Technical field [0001] The present invention relates to the technical field of background harmonic control, and in particular to a method for managing background harmonics with a parallel impedance type device. Background technique [0002] With the large-scale application of new energy technologies, the installed capacity of new energy power generation such as photovoltaics has increased year by year, and the proportion of non-linear power loads has gradually increased, causing the harmonic pollution of the distribution network to gradually deteriorate. Especially in the distribution network system with distributed photovoltaic access, series-parallel resonance occurs between the inlet LCL filter of the photovoltaic inverter and the equivalent impedance of the distribution system in certain frequency ranges. The presence of background harmonics will amplify the background harmonics, causing the resonant overvoltage of the LCL filter at the entrance of the photovoltaic inverter, ...

AI Technical Summary

Problems solved by technology

These two methods have different degrees of defects. APF is a single device with limited capacity and high cost. It is not suitable for direct series connection at the low-voltage outlet of distribution transformers.

The isolation transformer is usually installed on the important load feeder, and its application range is limited. It cannot be directly used at the low-voltage outlet of the distribution transformer to suppress the background harmonic voltage of the entire load bus.

Images