Direct-current distribution network virtual inertia control method based on variable droop coefficient

A technology of virtual inertia and control method, which is applied in the field of virtual inertia control of DC distribution network based on variable droop coefficient, can solve problems such as inability to give full play to the inertia support capacity of the system, and achieve the effect of improving power supply quality, stability, and inertia

Inactive Publication Date: 2020-07-31
SHANXI UNIV
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

[0006] Aiming at the problem that traditional control methods cannot give full play to the inertial support capability of the system, the present invention provides a virtual inertial control method for DC distribution networks based on variable droop coefficients

Method used

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  • Direct-current distribution network virtual inertia control method based on variable droop coefficient
  • Direct-current distribution network virtual inertia control method based on variable droop coefficient
  • Direct-current distribution network virtual inertia control method based on variable droop coefficient

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Experimental program
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Effect test

Embodiment 1

[0083] A method for virtual inertia control of DC distribution network based on variable droop coefficient, comprising the following steps:

[0084] Step 1: In the steady state of the flywheel energy storage system, the DC voltage change rate is zero, and the droop coefficient K of the flywheel energy storage system in the steady state is obtained 0 ;

[0085] In the selection of the coefficient function of the droop curve, the function satisfies the monotonic function in the sub-interval under the condition that the droop coefficient does not exceed the limit, and the convergence speed to the maximum value should be as fast as possible, so that the control can be fully utilized. The margin provides inertial support for the system. In addition, when the DC bus voltage change rate is 0, the droop coefficient should be equal to the initial value. Compare the convergence of the hyperbolic tangent function and the arctangent function, such as Figure 4 shown. Under the same co...

Embodiment 2

[0134] simulation analysis

[0135] In order to verify the effectiveness of the inertia strategy proposed by the present invention, a simulation model has been built in the Matlab / Simulink simulation software, and the flywheel system control strategy is as follows Image 6 As shown, but in actual control, the voltage change rate is difficult to obtain, so this embodiment makes the DC voltage pass through the filter and uses the voltage change δU instead of the voltage change rate for simulation.

[0136] In the simulation model, the DC bus voltage is 760V, which is taken as the reference value. In the simulation results, the power of the converter is positive when it flows to the DC side, and the voltage is the value per unit.

[0137] Simulation:

[0138] 1. Power surge simulation

[0139] In the initial state, the load power is about 15kw, U dc It is controlled at 748V or 0.984pu by the converter. The output power of the photovoltaic system is about 9kw, and the output p...

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Abstract

The invention belongs to the field of direct-current distribution system energy storage system control, and particularly relates to a direct-current distribution network virtual inertia control methodbased on a variable droop coefficient. The method comprises the following steps: acquiring a droop coefficient K0 of the flywheel energy storage system in a steady state; obtaining an instantaneous voltage variation delta U through a filter when the voltage fluctuation of the direct-current bus is caused by sudden power change; correcting the variable droop coefficient; restraining a droop coefficient according to upper and lower limits of power output of the flywheel energy storage system; wherein the changed droop coefficient controls the reference power of the flywheel energy storage system in an outer loop controller of the converter, controls a system rotating speed reference value at the same time, and provides a current reference value for an inner loop controller through a PI control link; controlling the output power of the system by the inner loop controller; controlling a droop characteristic curve of the system to swing by utilizing the continuously-changed droop coefficient, and carrying out self-adaptive control so as to continuously reduce the voltage fluctuation of the system; and returning to a stable operation state of the control system.

Description

technical field [0001] The invention belongs to the control field of an energy storage system of a direct current power distribution system, and in particular relates to a virtual inertia control method of a direct current distribution network based on a variable droop coefficient. Background technique [0002] In the modern power system, DC loads such as electric vehicles and big data centers are increasing day by day, and distributed power sources are connected on a large scale. The traditional AC distribution network has problems such as many conversion links and low system efficiency due to its excessive inverter links. It has been unable to meet the development needs of modern power systems. There is no loss of reactive power in the DC distribution network. Fewer conversion links make it easier for the DC distribution network to accommodate distributed power sources, reduce the difficulty of system control, and increase the power supply reliability of the system. [0...

Claims

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Application Information

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Patent Type & Authority Applications(China)
IPC IPC(8): H02J1/16
CPCH02J1/16
Inventor 赵兴勇张宇鑫郭垚
Owner SHANXI UNIV
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