Method for designing LCL (Logical Connection Layer) filter by uniformly controlling photovoltaic grid connection and active power filtering

Abstract

The invention discloses a method for designing an LCL (Logical Connection Layer) filter by uniformly controlling photovoltaic grid connection and active power filtering. The method comprises the following steps of: (1) determining the total inductance value LT of the LCL filter; (2) determining the filtering capacitance value Cf of the LCL filter; and (3) determining the resonance frequency fres of the LCL filter. According to the method, the LCL filter is designed on the basis of uniform control over a photovoltaic grid-connected system and active power filtering by using power grid accessing current which is provided with fundamental waves and resonant waves under the comprehensive consideration of the restraint conditions of the control applications of the fundamental waves and the resonant waves; and as proved by verification, the LCL filter can be used for effectively restraining switching frequency and higher-order harmonics, a satisfied photovoltaic grid connection effect can be achieved in combination with modeling control, and idle work required by a power grid is compensated properly.

Description

technical field [0001] The invention relates to an LCL filter of a photovoltaic grid-connected system, and more specifically, relates to a design method of an LCL filter under unified control of photovoltaic grid-connected and active filtering. Background technique [0002] With its inexhaustible and inexhaustible advantages, solar energy has become one of the new energy sources with the most development potential. Distributed power sources represented by new energy sources such as photovoltaic power generation are gradually developing from independent systems to large-scale grid connection. However, the output of photovoltaic power generation is affected by weather changes and has the characteristics of intermittency and uncertainty, which makes the utilization rate of photovoltaic grid-connected inverters only about 20%. On the other hand, the use of a large number of nonlinear loads in contemporary power systems has led to a decline in the power quality of the grid, espec...

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Problems solved by technology

The LCL filter can effectively suppress high-order harmonic components from entering the grid, but in the case of fundamental wave applications (such as photovoltaic grid-connected) or harmonic applications (such as active filtering), the parameter design method of the LCL filter is Different, the current design of LCL filter is mostly a separate grid-connected system or a separate active filter application. Although the literature mentions that LCL filters can be used in photovoltaic grid-connected systems with APF functions, there is no study further

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