Self-adaption output impedance control method based on virtual synchronous machine

Abstract

The invention discloses a self-adaption output impedance control method based on a virtual synchronous machine. The self-adaption output impedance control method firstly discloses a steady-state output impedance controller to improve the steady-state output impedance to guarantee paralleled current sharing in parallel steady operation, then provides a capacitance and voltage compound differential controller to improve damping of a system and enhance the stability of the system and finally adopts a dynamic output impedance controller to reduce output impedance in a dynamic process and voltage jump to improve dynamic response of output voltage. The self-adaption output impedance control method can be widely applied to control on micro grid inverters in different load conditions and meets the requirement of the dynamic-steady-state performance in off-grid operation of the micro grid inverters. Furthermore, parallel-connection operation of a plurality of inverters is achieved.

Description

technical field [0001] The invention relates to an adaptive output impedance control method, in particular to an adaptive output impedance control method based on a virtual synchronous machine. Background technique [0002] In recent years, virtual synchronous machine technology, as a new type of power generation mode for microgrid inverters, has received a lot of attention from scholars. The microgrid inverter using virtual synchronous machine technology is called virtual synchronous machine. The virtual synchronous generator (Virtual Synchronous Generator, VSG) needs to run in two modes, grid-connected and island-connected. VSG needs to carry different loads when running off-grid, such as resistance-inductance-capacitance loads, motor loads, rectifier bridge loads, and various active loads. Under different load conditions, its dynamic response and steady-state performance are different. In order to achieve good dynamic steady-state performance, especially faster dynamic...

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Problems solved by technology

First of all, there are two components when the abc coordinate system variable of the three-phase system is converted to the dq coordinate system, one is a static component and the other is a dynamic component, and its output impedance is different from the equivalent circuit of a single-phase system; in addition, high-power The switching frequency of VSG is low, and the control delay is large, which adds an unstable pole to the system, especially when multiple machines are running in parallel, its stability is further reduced, which makes the system must reduce the bandwidth to maintain system stability. The reduction makes the dynamic performance of the system further decline, which greatly limits the design criteria of the controller and VSG passive parameters, and makes the overall control performance of high-power VSG decrease

At present, for these two problems, there are few discussions and solutions in the prior art

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