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Parameter design method for LLCL filter of three-phase grid-connected system

A technology of filter parameters and design methods, applied in AC networks to reduce harmonics/ripples, AC network circuits, harmonic reduction devices, etc., can solve problems such as reducing system efficiency and increasing system losses

Inactive Publication Date: 2019-04-23
SHANGHAI MARITIME UNIVERSITY
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

The traditional passive damping is to add resistance to the branch of the filter, but this will add extra loss to the system and reduce the efficiency of the system; the active damping is to change the control of the inverter, but this requires additional sensors and requires many Complex Control Algorithm with Loop Feedback
[0004] In order to solve the resonance problem existing in the LLCL filter, the present invention proposes a parameter design method for the LLCL filter of a three-phase grid-connected system from the perspective of improving the stability and robustness of the system when the grid current control is used

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  • Parameter design method for LLCL filter of three-phase grid-connected system
  • Parameter design method for LLCL filter of three-phase grid-connected system
  • Parameter design method for LLCL filter of three-phase grid-connected system

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Embodiment Construction

[0030] With reference to accompanying drawing, further illustrate the present invention:

[0031] This embodiment takes a 5KW grid-connected inverter system as an example to further illustrate a parameter design scheme of a grid-connected inverter LLCL filter, in which the effective value of the line voltage on the grid side is 400V, and the grid-connected inverter The DC side voltage is 730V, the grid frequency f o 50Hz. L 1 is the inverter side filter inductance, L 2 is the grid side filter inductance. figure 1 is the schematic diagram of the LLCL filter circuit. The system filter impedance base value, capacitance base value and inductance base value can be obtained: where U g = 400V is the effective value of the line voltage on the grid side, ω o =2π×50rad / s is the grid angular frequency, P o =5kW is the rated active power. The flow chart of filter parameter design is as follows: figure 2 As shown, the specific design steps are as follows:

[0032] (1) Calculat...

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Abstract

The invention provides a parameter design method for an LLCL filter of a three-phase grid-connected system. The method comprises the following steps: establishing a Noton equivalent model of a grid-connected inverter with the LLCL filter; obtaining an open-loop transfer function and a closed-loop output admittance according to the established Noton equivalent model; obtaining a boundary conditionfrc and a value range of system stability and robustness according to a passivity concept and a closed-loop output admittance baud map; determining the switching frequency fsw and the control samplingfrequency fs of the inverter; determining the parameters of the LLCL filter according to the frc ratio relationship and the value range. According to the parameter design method for the LLCL filter,the parameter design complexity of the LLCL filter is reduced. Meanwhile, the system stability condition is considered.

Description

technical field [0001] The invention belongs to the technical field of grid-connected inverters, in particular to a method for designing parameters of an LLCL filter in a three-phase grid-connected system. technical background [0002] With the increasing shortage of traditional energy and serious environmental pollution, the utilization of renewable energy has attracted much attention. Commonly used grid-connected converters based on PWM modulation technology will generate a large number of high-order harmonics, which will easily pollute the public power grid. In response to the above problems, relevant scholars proposed a method with L f -C f A new type of high-order LLCL filter in the series resonance branch, the resonance frequency of the LC series resonance circuit is set at the switching frequency, and the purpose of filtering specific sub-harmonics is achieved through the low impedance characteristics generated by resonance. Compared with the LCL filter, the LLCL f...

Claims

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Application Information

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IPC IPC(8): H02J3/01
CPCH02J3/01H02J2203/20Y02E40/40
Inventor 黄敏
Owner SHANGHAI MARITIME UNIVERSITY