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Grid connection control method and system

A technology of control method and control strategy, which is applied in the direction of AC network circuit, single-network parallel feeding arrangement, electrical components, etc., can solve the problems of limited overload capacity and limited resistance of synchronous inverters, etc., to improve the frequency fluctuation of the grid side The ability to increase the effect of transient stability

Inactive Publication Date: 2020-04-07
NORTH CHINA ELECTRIC POWER UNIV (BAODING)
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Problems solved by technology

However, on the one hand, the moment of inertia of the synchronous inverter is much smaller than that of the traditional synchronous generator; on the other hand, compared with the traditional synchronous generator, traditional power electronic devices have limited overload capacity.
Therefore, the synchronous inverter has limited ability to resist the grid frequency fluctuation of the grid-connected point. When the frequency of the grid-connected point changes greatly, the synchronous inverter is easy to stop working due to the large change of the virtual angular frequency.

Method used

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  • Grid connection control method and system

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Experimental program
Comparison scheme
Effect test

Embodiment 1

[0071] figure 1 It is a flow chart of the grid connection control method provided by Embodiment 1 of the present invention.

[0072] The distributed power grid-connected control method based on the variable inertia and variable damping coefficient of the synchronous inverter, referred to as the grid-connected control method, refers to figure 1 , the grid-connected control method includes the following steps:

[0073] Step S110, according to the electromechanical transient equation of the synchronous motor, establish a virtual rotor model of the synchronous inverter, wherein the virtual rotor model includes the grid frequency of the grid connection point;

[0074] Specifically, the core of the synchronous inverter is to simulate the mechanical motion characteristics of the rotor by introducing the electromechanical transient equation of the synchronous motor, and establish a mathematical model of the virtual rotor of the synchronous inverter. The virtual rotor model is shown i...

Embodiment 2

[0102] figure 2 It is a flowchart of a method for performing fluctuation control on a virtual angular frequency provided by Embodiment 2 of the present invention.

[0103] The control strategy includes virtual inertial time constant J and damping coefficient D, refer to figure 2 , in step S150 of the grid-connected control method, the method for fluctuating the virtual angular frequency specifically includes the following steps:

[0104] Step S210, determining the speed phase of the virtual angular frequency according to the virtual rotor model, wherein the speed phase includes an acceleration phase and a deceleration phase;

[0105] Specifically, first judge the offset value Δω and the rate of change according to formula (1) The sign of , when Δω and When the same sign, the virtual rotor is in the acceleration stage; when Δω and When the sign is different, the virtual rotor is in the deceleration phase.

[0106] Step S220, during the acceleration phase, suppress the r...

Embodiment 3

[0124] The solution of the present application will be further described in detail below in conjunction with the circuit diagram.

[0125] The main circuit adopted by the present invention is as Figure 4 As shown, it includes three parts: power grid, synchronous inverter and distributed power supply. The synchronous inverter rectifies the voltage of the three-phase grid into DC voltage and connects with the distributed power supply through capacitors. The grid-connected control system includes a calculation module, an active power control module, a reactive power control module and an inertial damping integrated control module; among them, the inertial damping integrated control module is as follows: Figure 5 shown.

[0126] The calculation module can calculate the electromagnetic torque T e , reactive power Q and virtual electromotive force e. The specific calculation is shown in the formulas (13)-(15):

[0127] T e = M f i f g ,sinθ〉 (13)

[0128] Q=-M f i f ωg ,...

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Abstract

The invention provides a grid-connected control method and system, and relates to the technical field of distributed power supply grid connection. The grid-connected control method comprises the steps of building a virtual rotor model of a synchronous inverter according to an electromechanical transient equation of a synchronous motor, wherein the virtual rotor model comprises a grid-connected point power grid frequency; obtaining an adjustment function of a virtual angular frequency according to the virtual rotor model when the grid-connected point power grid frequency changes; obtaining a natural oscillation angular frequency and an impedance ratio according to the adjustment function; analyzing the natural oscillation angular frequency and the impedance ratio to obtain a control strategy of the synchronous motor; and performing fluctuation control on the virtual angular frequency according to the virtual rotor model and the control strategy. By the grid-connected control method, the capability of resisting frequency fluctuation of a power grid side of the synchronous inverter during the grid-connected running process can be improved, and the transient stability is improved.

Description

technical field [0001] The invention relates to the technical field of distributed power grid-connected research, in particular to a grid-connected control method and system. Background technique [0002] With the increasing energy problems, traditional fossil energy can no longer meet the requirements of human sustainable development, and the global energy crisis and environmental problems have become increasingly prominent. With the rapid development of renewable energy such as wind and wind, distributed power generation technology has received more and more attention. As a link between distributed power and the grid, the function of grid-connected inverters has been deeply explored and its beneficial role has been affirmed. [0003] Synchronous inverter has become a current research hotspot because of its characteristics of helping clean energy to integrate with the grid, improving existing grid-connected technologies, and avoiding potential safety hazards in the grid. T...

Claims

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Application Information

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Patent Type & Authority Patents(China)
IPC IPC(8): H02J3/38
CPCH02J3/381H02J2203/20
Inventor 刘其辉张怡冰
Owner NORTH CHINA ELECTRIC POWER UNIV (BAODING)