Weak power grid source load impedance model analysis method of grid-connected power generation system

Abstract

The invention relates to a weak power grid source load impedance model analysis method of a grid-connected power generation system, and relates to the technical field of power grids. The technical problem that the existing method is not suitable for a weak power grid is solved. The method comprises the steps that a grid source load impedance model is defined for the grid-connected power generation system, wherein the model is combined with grid-connected inverter common coupling point voltage, alternating current power grid line impedance, alternating current power grid load impedance, alternating current power grid equivalent voltage, alternating current power grid equivalent current source and alternating current power grid access current of the grid-connected power generation system; the assumption that the load of an alternating current power grid is a resistive inductive load and the line impedance of the alternating current power grid is resistive inductive line impedance is carried out, so that an open-loop transfer function and a closed-loop transfer function of the grid-connected power generation system under double-loop control are acquired; and according to the acquired open-loop transfer function and the closed-loop transfer function, the grid-connected power generation system is analyzed. The method provided by the invention is suitable for analyzing the grid-connected power generation system under the weak power grid.

Description

technical field [0001] The invention relates to power grids and technologies, in particular to a technology for analyzing a weak power grid network source load impedance model of a grid-connected power generation system. Background technique [0002] With the gradual popularization of new energy sources, grid-connected inverters are more and more widely used in solar grid-connected power generation systems or wind energy grid-connected power generation systems. When there are many transformers connected to the power grid, and the leakage inductance and line impedance are large, the power grid is increasingly showing the characteristics of a weak power grid. At this time, the research on the interaction between the grid-connected inverter and the power grid is particularly important. [0003] The current focus of research on weak grids is to use the traditional impedance analysis method to analyze the interaction of the system at this time. When the voltage and load of the t...

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Problems solved by technology

However, the disadvantages of this method are: 1) The phase margin obtained by using the ratio of the grid impedance to the inverter output impedance in the impedance analysis method is not the real phase margin of the system, but a characterization; directly reflects the damping of the system, and the degree of damping of the system cannot be accurately defined at this time; 2) The amplitude margin is not involved in the impedance analysis method, and the amplitude margin is also very important for evaluating the quality of the system, so 3) The cut-off frequency of the system cannot be reflected in the impedance analysis method; although the intersection point of the amplitude-frequency characteristics of the grid impedance and the equivalent output impedance of the inverter is defined as the handover frequency, its physical meaning is not clear; 4 ) The grid-connected system can be modified by using the impedance analysis method, so that the system can meet certain stability conditions; but for some physical quantities of the system itself, the impedance analysis method cannot be well studied, so it is necessary to have a detailed analysis of the entire grid-connected system A more detailed mathematical model to process the system

[0008] In view of the above reasons, under the condition of weak power grid, the traditional impedance analysis method cannot conduct a comprehensive and detailed analysis of the grid-connected power generation system. Therefore, when the physical quantities in the grid-connected power generation system change, the impact on it cannot be accurately to evaluate

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