Small interference stability discrimination method for grid-connected voltage source type converter with phase-locked loop

Abstract

The invention discloses a small interference stability discrimination method for a grid-connected voltage source type converter with a phase-locked loop. The method comprises the following steps: firstly, establishing a mathematical model that a VSC (Voltage Source Converter) containing a PLL (Phase Locked Loop) is connected to an infinite bus system through a power transmission line; then obtaining a steady-state equation of the system and solving a balance point of the system; performing linearization processing on the system mathematical model, and obtaining a frequency domain equation through Laplace transformation; performing simplification processing to obtain a single input single output (SISO) model; and finally, deducing the necessary and sufficient conditions for the stability of the grid-connected voltage source type converter with the phase-locked loop according to the classical Routh criterion, and further obtaining the simplified sufficient conditions. According to the method, the analytic relationship among the small disturbance stability of the grid-connected VSC, the VSC controller parameters, the line parameters and the system operation mode is clearly represented; the method can be used for qualitatively analyzing key factors influencing system stability and revealing a system instability mechanism, and can also be used for guiding VSC controller parameter design and system operation mode formulation.

Description

technical field [0001] The invention belongs to the field of electric power technology, and in particular relates to a method for judging the stability of small disturbances of a grid-connected voltage source converter (VSC) with a phase-locked loop (PLL). Background technique [0002] Grid-connected voltage source converters (VSCs) are widely used in renewable energy generation and high voltage direct current (HVDC) transmission, and most of them use phase lock loops (PLLs) to obtain common connection points Accurate phase angle information of Point of Common Coupling (PCC) is used to ensure that the converter voltage is synchronized with the grid voltage. Much of the existing literature states that the dynamic characteristics of PLLs have a negative impact on system stability. [0003] The traditional method to study the stability of the system with small disturbance is mainly the modal analysis method, which depicts the rough stability boundary of the system by calculati...

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Problems solved by technology

[0004] Existing stability judgments rely on eigenvalue calculations or Nyquist plots, which involve many complex and repetitive numerical calculations. Even if the system power transmission limit or the controller parameter range that can ensure system stability can be obtained using these methods, it is still An analytical relationship between control parameters, system operating point, and system stability cannot be established

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