Virtual synchronous generator-based microgrid inverter balance control method

Abstract

The invention discloses a virtual synchronous generator-based microgrid inverter balance control method. The method comprises steps: capacitive current is estimated according to a general differential discretization equation, and in comparison with the traditional method, the differential discretization features have better amplitude frequency features through reasonable parameter configuration; a combined feedback control method between the output frequency of the microgrid inverter and the grid frequency is adopted, independent adjustment on a power-angle control droop coefficient and a virtual damping coefficient is realized, and the purpose of decoupling control is achieved; a grid frequency logic judgment link with backlash features is given to switch a power outer loop regulator, and mode switching between the grid frequency adjustment and power-limiting operation is realized; and the microgrid inverter is adopted and a weighted control method based on the inductive current and the capacitive current is adopted, the contradiction problem between the dynamic response of the microgrid inverter output voltage and island parallel current-sharing features is balanced, and the overall performance of the microgrid inverter is improved.

Description

technical field [0001] The invention relates to a microgrid control method, in particular to a microgrid inverter balance control method based on a virtual synchronous generator. Background technique [0002] In recent years, as the penetration rate of new energy power generation units in the power system continues to increase, at the same time, the traditional centralized primary energy is gradually reduced, the moment of inertia of the system is gradually reduced, the frequency fluctuation becomes larger, and the intermittent characteristics of the primary energy are more severe. The frequency fluctuation of the power grid is exacerbated, making the frequency stability of the system more and more serious. And as the penetration rate of distributed power grids increases, its role in the grid will change. Distributed power sources will no longer just provide power to the grid, but should also be able to support a certain grid voltage and frequency to stabilize the grid. run...

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Problems solved by technology

[0006] The Chinese Invention Patent Application Specification (CN105186554A) entitled "A method for surpassing a virtual synchronous generator with self-optimization of the moment of inertia and damping" provides a method for compensating and controlling the frequency difference of the grid according to the self-adjustment of the moment of inertia and damping, however The damping coefficient has an impact on the droop characteristics in the steady state, and there is coupling in the control, which is not conducive to parameter design

[0007] In the technical solution disclosed in the Chinese Invention Patent Application Specification (CN105207261A) entitled "Off-Grid Control Method and System Applied to Virtual Synchronous Generator", a fast terminal sliding mode control strategy is used to switch the off-grid / grid-connected state, which can Make the error value of the grid voltage and the load voltage approach to zero quickly and steadily, but it does not give the frequency and phase difference control problem between the grid voltage and the load voltage

[0008] The Chinese Invention Patent Application Specification (CN105915140A) entitled "A Decoupling Control Method and Device Based on Virtual Synchronous Generator" provides a dq decoupling control method for voltage and current, which can achieve decoupling, but the decoupling characteristics Rely on the estimated characteristics of state variables, and the control method is complex

[0009] In short, the damping characteristics and droop characteristics of the existing VSG technology in the grid-connected mode cannot achieve decoupling control. In the off-grid parallel mode, it is difficult to take into account the relationship between dynamic response and steady-state current sharing at the same time, and there is a transition process in off-grid switching

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