Method for controlling virtual synchronous generator of two-stage photovoltaic inverter

Abstract

The invention discloses a method for controlling a virtual synchronous generator of a two-stage photovoltaic inverter. The method is characterized in that the procedure of logic judgment on the working area of a photovoltaic power curve is given, so as to solve the problems of power fluctuation and voltage stabilizing at the direct current side under two running modes of the virtual synchronous generator, such as grid connecting and grid disconnecting; the stability of the working area of a photovoltaic battery is represented by judging the positive and negative of the change rate dPdc_boost / dUdc_boost of input power along with the direct current voltage, and a pre-boost controller and a post-inverter power outer loop controller are switched, so as to effectively solve the problem of direct current voltage collapse during overload running; a combined feedback control method of post-inverter output frequency and power grid frequency is adopted, so that the sag coefficient is controlledby the power angle, and the virtual damping is independently adjusted; an inductance current and capacitance current weighting control method is used for balancing the output voltage dynamic responseof the photovoltaic inverter and the island parallel current equalizing characteristics, so as to realize the uniform control under two running modes of the two-stage photovoltaic inverter, such as grid connecting and grid disconnecting, thereby improving the whole property.

Description

technical field [0001] The invention relates to a photovoltaic inverter control method, in particular to a two-stage photovoltaic inverter virtual synchronous generator control method. Background technique [0002] In virtual synchronous generator control, virtual synchronous generator (Virtual Synchronous Generator-VSG) technology shows excellent control performance with its common voltage source control mode combined with off-grid. Several key control objectives of VSG-based virtual synchronous generators are: (1) During grid-connected operation, virtual inertia, virtual damping, virtual impedance and droop characteristics can be provided to the grid to support grid frequency and voltage changes and maintain large grid stability , and maintain the current sharing characteristics between virtual synchronous generators; (2) When running off-grid, it needs to provide higher power quality to the load. In addition, the VSG needs to operate in both grid-connected and island mod...

AI Technical Summary

Problems solved by technology

Through the analysis of the stable operation area of ​​the photovoltaic power supply and the characteristics of the two-stage photovoltaic inverter control, according to the different operation areas of the photovoltaic power supply, the control target of the front-stage boost converter and the control strategy of the rear-stage inverter are switched to solve the problem. It solves the stability problem caused by the unbalanced input power and load of the DC side, effectively prevents the DC voltage collapse when the island is overloaded, and realizes the unified control of the two-stage photovoltaic inverter in the off-grid mode.

Combined with virtual synchronous generator control technology, it solves the realization problem of two-stage photovoltaic virtual synchronous generator

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