Direct current micro-network line impedance detecting method and device for sagging control

Abstract

The invention relates to a direct current micro-network line impedance detecting method and device for sagging control. The method comprises the steps that S1 a plurality of groups of disturbance voltage signals are set and used as the reference voltage of a sagging controller; S2 output voltage and output current output by a DC-DC converter are measured; and S3 the line impedance between each distributed energy storage unit and a direct current bus is acquired according to a current-voltage relationship equation and multiple groups of output voltage and output current measured in the step S2; and the line impedance acquired in the step S3 is negatively compensated to the sagging resistor of the corresponding sagging controller. Compared with the prior art, the method and device have the advantages that the accurate measurement of the line impedance is realized without adding any additional measuring device on the basis of traditional sagging control; sagging coefficients are corrected to reduce the influence of the line impedance on sagging control; the load distribution rationality is ensured; the bus voltage quality is improved; and the system stability is improved.

Description

technical field [0001] The invention relates to the technical field of distributed power generation, in particular to a method and device for detecting the impedance of a DC micro-grid line for droop control. Background technique [0002] With the development of new energy, it has become an inevitable trend for large-scale photovoltaic wind turbines to be connected to the power grid, but the impact on the traditional power system cannot be ignored. As a form of efficient coordinated control of distributed power sources, microgrid can effectively reduce the distribution The impact of power sources on power systems. Microgrids can be divided into AC microgrids and DC microgrids according to different bus voltages. Compared with AC microgrid, DC microgrid has the characteristics of high efficiency, economy and simplicity, so it has received extensive attention. [0003] The microgrid consists of four parts: network, source, load, and storage. The main control goal is to coord...

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Problems solved by technology

[0004] However, in droop control, load distribution and voltage control are often not compatible, and most of the existing control methods ignore the influence of line impedance, but in actual systems, line impedance is not completely negligible. It will affect load distribution and the quality of bus voltage. Existing solutions mostly use low-speed communication lines or sparse communication lines to exchange information between units, thereby achieving accurate load distribution.

[0005] 1. In a DC microgrid, load distribution and voltage quality are greatly affected by line impedance when droop control is used

[0006] 2. Centralized control is adopted, which has high requirements for the central controller. If there is a problem with the central controller, all units in the system cannot work normally, so the reliability of the system is poor

[0007] 3. Whether it is the use of high-speed communication lines in centralized control or the low-speed communication lines used in improving droop control, the addition of communication lines will increase system costs and is not conducive to system expansion

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