A Resonance Analysis Method for Multiple Fans Connected to the Grid

Abstract

The invention discloses a multi-fan grid-connected resonance analysis method. The method comprises the following steps: on the basis of an output impedance model of an inverter, establishing a grid-connected equivalent model of a wind power plant; establishing a cable equivalent model according to the cable distribution characteristic under a harmonic state, and establishing the equivalent impedance of fan output power at a PCC (Point of Common Coupling) according to a relationship between the absorption power of the PCC and the fan output power to obtain the total impedance of a distributed wind power grid-connected system. The multi-fan grid-connected resonance analysis method has the advantages that the total impedance is calculated by establishing a distributed wind power grid-connected system model recorded with the cable and fan output power; the system model more accords with practical situations and has an application value and a practical significance for the resonance problem in an accurate analysis system.

Description

technical field [0001] The invention relates to the technical field of resonance analysis, in particular to a resonance analysis method for grid-connected multi-wind turbines. Background technique [0002] With the increasingly serious energy crisis, new energy sources such as wind power and photovoltaics have been widely concerned and applied. Distributed power supplies not only provide clean and efficient energy, but also have a greater impact on the security and stability of the power grid and power quality [1]. Non-linear devices such as power electronics in distributed power generation such as wind turbines generate large harmonic currents that are injected into the grid, reducing the power quality of the grid. In order to reduce the harmonic distortion rate of the grid-connected current, the existing distributed generator (DG) mostly adopts the grid-connected inverter including the LCL filter. LCL is a third-order system, which is prone to resonance problems, and ther...

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Problems solved by technology

In the actual power grid, the wind farm supplies power to the grid through the cable, and the cable has a large capacitance to the ground, which will cause complex resonance in the system; under different wind speeds, the output power of the fan is different, which will affect the system damping, and then affect the resonance point impedance value

However, the existing analysis methods do not consider the influence of transmission cables on resonance changes, such as reference [4], nor consider the resonance changes caused by different output power of fans, such as references [3][4], and do not consider load impedance The relationship with the fan power, such as reference [6], so it is impossible to do an accurate analysis

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