Active impedance compensation device of series LC type filter

Abstract

The invention provides an active impedance compensation device of a series LC type filter. The active impedance compensation device comprises a power main circuit and a control module. The power maincircuit comprises a two-level three-phase inverter bridge H. A DC side is connected with a supporting capacitor CD in parallel, and an AC side is connected with three groups of LC series filter circuits formed by the series connection of a filter inductor L and a filter capacitor C, wherein the filter capacitor C connected in series can bear most of voltages at common connection points, so that aterminal voltage withstood by the active impedance compensation device is relatively low, a multi-level structure is prevented from being adopted in a system with relatively high voltage, thereby simplifying the control. The control module MC is connected with the two-level three-phase inverter bridge H and is used for providing a driving signal. The control module MC comprises an A / D sampling module, a phase-locked loop, a harmonic detection loop (HDU) and an impedance compensation loop (ZCL), and is used for providing compensation impedance, reducing the equivalent impedance of a power gridat the PCC and improving the stability of the power grid.

Description

technical field [0001] The present application relates to the technical field of inverter grid-connected systems, in particular to an active impedance compensation device for a series LC filter. Background technique [0002] In recent years, with the development of power electronic technology, a large number of new power electronic devices have been connected to the power grid, such as new energy grid-connected inverters, high-speed electric locomotives, because the controllers of these power electronic devices are complex and the switching frequency is high, so With extremely strong nonlinear characteristics and negative resistance characteristics, it brings new problems that do not exist in traditional power grids, such as high-order harmonic resonance, harmonic amplification, etc., which seriously affects the power quality and stability of the power grid system. It has become a research hotspot of scholars at home and abroad. [0003] The root cause of the series of harm...

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Problems solved by technology

[0002] In recent years, with the development of power electronic technology, a large number of new power electronic devices have been connected to the power grid, such as new energy grid-connected inverters, high-speed electric locomotives, because the controllers of these power electronic devices are complex and the switching frequency is high, so With extremely strong nonlinear characteristics and negative resistance characteristics, it brings new problems that do not exist in traditional power grids, such as high-order harmonic resonance, harmonic amplification, etc., which seriously affects the power quality and stability of the power grid system. Has become a research hotspot of scholars at home and abroad

[0003] The root cause of the series of harmonic resonance and harmonic instability caused by the connection of new power electronic equipment to the power system is caused by the mismatch between the grid impedance and the grid-connected converter system impedance. These problems often occur in Weak grid, that is, when the grid impedance is large, the current solutions to this type of problem mainly include 1) improving the control parameters of the grid-connected converter, and then changing the impedance characteristics of the grid-connected converter system, which will affect The original control performance of the grid-connected converter has great limitations; 2) To reduce the impedance of the existing line, this method requires a large investment; 3) Impedance adapters are used to improve the system impedance of the grid-connected converter. However, the impedance adapter The AC side of the circuit usually uses a single inductor in series. This topology indicates that the adapter device needs to withstand the full voltage at the PCC. For systems with higher voltages, a multi-level topology is required, and this topology will increase cost and control complexity.

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