Improved VSG parallel control method based on voltage secondary regulation

Abstract

The invention belongs to a multi-virtual synchronous generator parallel on-load operation technology, and particularly relates to an improved VSG parallel control method based on voltage secondary regulation, and the method comprises the steps: a PI regulator is employed in a reactive power-voltage droop control link of a parallel VSG system to enable VSG to output reactive power and transmit impedance to be decoupled; a voltage compensation signal is added in the reactive power-voltage droop control link, so that the input of the PI regulator in a steady state is 0; voltage secondary regulation based on a PI regulator is added on an output voltage amplitude reference value, so that the load works under a rated voltage condition when the system is stable; self-adaptive virtual impedance based on parallel circulating current is introduced, and an absolute value is obtained and fed back to a virtual impedance link after the amplitude of current output by the virtual synchronous generator is subtracted; and multi-VSG power sharing can be realized, and the abrupt change of the parallel instant output current can be inhibited when the load works under the rated voltage. Circulating current suppression is realized, the dynamic response of the system is improved, and the steady state of the system is not influenced.

Description

technical field [0001] The invention belongs to the technical field of parallel operation of multiple virtual synchronous generators, in particular to an improved VSG parallel control method based on voltage secondary regulation. Background technique [0002] The basic idea of ​​the virtual synchronous generator (VSG) is to make the grid-connected inverter simulate the characteristics of the synchronous generator through control, that is, inertia, damping characteristics, primary frequency regulation characteristics and primary voltage regulation characteristics, and use its moment of inertia and damping characteristics to suppress Rapid fluctuations in grid frequency, voltage or load fluctuations. Multi-VSG load operation can improve energy utilization and system reliability. [0003] The traditional virtual synchronous generator technology realizes power decoupling under the condition that the output impedance is approximately pure inductance and ignores the line impedanc...

AI Technical Summary

Problems solved by technology

This type of control achieves power sharing and has the ability to suppress circulating currents, but it cannot make the load work under rated voltage conditions, and the virtual impedance introduced by reactive power feedback will have a large value in steady state, increasing the transmission impedance. voltage drop

[0004] The application number is CN201310517616.1 and the name is "A method of inverter droop control with secondary frequency and voltage regulation characteristics" and the application number is CN201510628811.0 and the name is "Synchronous inverter with secondary voltage and frequency regulation function". Invention patents for "inverter control system" are all connected in series to the PI regulator in the reactive power-voltage loop. Since the reactive power-voltage loop itself already has an integrator, this will cause two integrators to be connected in series, thus affecting the load voltage. adjust speed

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