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Grid-connected inverter circuit based on improved LLCL filter and filtering method thereof

A technology of inverter circuit and filter, which is applied in the field of active damping method, can solve the problems of active power consumption and energy loss, and achieve the effects of suppressing resonance peak, good filtering effect, avoiding energy loss and heat dissipation

Active Publication Date: 2014-11-19
BEIJING XINGHANG MECHANICAL ELECTRICAL EQUIP
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  • Abstract
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Problems solved by technology

However, the existence of the damping resistor Rd in the Rd-Cd damping branch not only consumes a certain amount of active power, causing unnecessary energy loss, but also brings certain problems to the heat dissipation of the system, especially in high-power applications. , it is often necessary to design a special cooling device for the damping resistor

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  • Grid-connected inverter circuit based on improved LLCL filter and filtering method thereof
  • Grid-connected inverter circuit based on improved LLCL filter and filtering method thereof
  • Grid-connected inverter circuit based on improved LLCL filter and filtering method thereof

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Embodiment Construction

[0022] The present invention will be further elaborated below in conjunction with the accompanying drawings and specific implementation.

[0023] In order to further understand the performance advantages of the LLCL filter, first compare it with the traditional LCL filter. The simplified circuits of the two are as follows figure 1 (a), (b) shown. where the L of the LLCL filter f -C f The resonant branch can pass through the L f 、C f The series resonance of the series resonance reaches zero impedance at a specific frequency, and this specific frequency is usually set at the switching frequency to eliminate the switching frequency subharmonic. In order to further explore the characteristics of the two filters, by figure 1 (a), (b) can derive the transfer function of the filter, formula (1) is the transfer function of the LLCL filter, where when L f =0, the transfer function of the LCL filter can be obtained.

[0024] ...

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Abstract

The invention provides an active damping method of a grid-connected inverter circuit based on an improved LLCL filter. A grid-connected inverter is connected with a power grid through the improved LLCL filter. The improved LLCL filter comprises a first filter inductor, a second filter inductor and a resonance suppression branch, and the resonance suppression branch is formed by connecting an Lf-Cf series resonance branch and a Cd damping branch in series. The inverter side current is fetched to serve as outer ring current for feedback, the current of the Cd damping branch is fetched to serve as inner ring current to restrain a resonance peak, normal system operation is guaranteed, the problems of power losses and heat dissipation of a damping resistor are solved effectively, and overall efficiency of a grid-connected inverter system is improved.

Description

technical field [0001] The invention belongs to the technical field of power grid converter control, and in particular relates to an active damping method of a grid-connected inverter circuit based on an improved LLCL filter. Background technique [0002] In recent years, the grid connection of new energy sources has attracted extensive attention from the academic community. The grid-connected inverter is a very important part of the grid-connected circuit. The grid-connected inverter using the PWM modulation method has the advantages of unit power factor and energy bidirectional flow, but at the same time it will also generate harmonics of the switching frequency. The power grid brings harmonic pollution, and even seriously affects the normal operation and work of electrical equipment. [0003] In order to suppress the high-frequency harmonics brought by the grid-connected inverter, a low-pass filter can be added at the connection between the inverter and the grid, and the...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02M7/42H02M1/12
CPCY02E10/76
Inventor 古金茂王新庆张军兆张强朱妙玲陈宁李晓亮段美珠
Owner BEIJING XINGHANG MECHANICAL ELECTRICAL EQUIP
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