CN101436778A - Networking method for minitype electric network - Google Patents

Abstract

The invention discloses a micro-grid networking method, which is characterized in that the AC power generation source is connected to the DC bus through the AC/DC converter, the DC power generation source is connected to the DC bus through the DC/DC converter, and the DC bus is connected to the grid through the The inverter is connected to the large power grid, the DC bus is connected to an energy storage device, and the AC/DC converter, DC/DC converter and grid-connected inverter are all controlled by the system controller. The micro-grid of the present invention can add many power sources with different power generation properties, which promotes the development of the micro-grid. The network structure of the DC bus can reduce the control difficulty of the micro-grid and improve the power supply quality of the micro-grid. The network structure of the DC bus bar of the present invention has great advantages in the connection of the micro-grid to the large-scale grid. The power grid is very beneficial.

Description

A kind of micro-grid networking method

technical field

The invention relates to a networking method of a micro-grid, in particular to a networking of a micro-grid containing power sources with different power generation properties.

Background technique

Micro-grid technology refers to a system that connects scattered power generation resources (such as self-powered power generation equipment or backup generator sets, solar power generation devices, wind power generation equipment, diesel power generation devices, etc.) in a certain area. It can also run in parallel with the main large-scale power grid through the power distribution link.

Chinese patent ZL02136471.0 discloses a distributed power networking and power supply method. It uses distributed small-scale generators to interconnect generators in a region, connect users to the grid, and connect users to each other. However, this patent does not disclose a specific networking method.

Dong Xueping introduced an experimental device for wind-solar-diesel-storage hybrid power generation and intelligent control system in the article "Computer Control System of Wind-solar-diesel-storage Composite Intelligent Power Supply System" (Computer Measurement and Control, Issue 6, 2002). The transmission network of the composed micro-grid adopts the method of simultaneous direct current and alternating current transmission.

With the continuous development of micro-grids and the addition of various output voltage and current power sources, the composition of micro-grids is becoming more and more complex, and the existing networking technology has the following shortcomings:

First of all, if the AC power generation source is connected to the grid through AC, strict requirements must be imposed on the frequency, voltage and phase of the AC power generation source, which increases the difficulty of micro-grid control and cannot guarantee the grid voltage well, such as wind power generation. unit.

Secondly, the AC-DC hybrid transmission network is adopted, and its cost is relatively high.

Contents of the invention

The purpose of the present invention is to provide a micro-grid networking method with simple system structure, convenient control and easy expansion, aiming at the deficiencies of the prior art.

The purpose of the present invention is achieved by the following methods:

A micro-grid networking method, characterized in that the AC power generation source is connected to the DC bus through the AC/DC converter, the DC power generation source is connected to the DC bus through the DC/DC converter, and the DC bus is connected to the DC bus through the grid-connected inverter The large power grid is connected, the DC bus is connected with an energy storage device, and the AC/DC converter, DC/DC converter and grid-connected inverter are all controlled by the system controller.

Alternating current generation sources include unsteady alternating current generation sources and controllable power and constant voltage alternating current generation sources.

If the energy storage is a DC energy storage, such as a battery, it is connected to the DC bus through a DC-DC converter; if it is an AC energy storage, such as a flywheel, it is connected to the DC bus through a DC-AC converter. It is also possible to include both a DC energy store and an AC energy store.

The DC bus voltage is preferably 300-500v. When there is no controllable and constant AC power generation source for the micro-grid, for example, only wind power generators, the DC bus voltage is controlled at 300v. Such a micro-grid is easy to control and maintain a constant voltage. When the micro-grid power generation source has a controllable and constant AC power source, keep the DC bus voltage at 500v.

Compared with prior art, the present invention has following advantage:

Micro-grids can add many power sources with different power generation properties, which will promote the development of micro-grids. The network structure of the DC bus can reduce the control difficulty of the micro-grid and improve the power supply quality of the micro-grid.

The network structure of the DC busbar can reduce the cost of the micro-grid composed of different power generation sources. Only two busbars are connected between different power generation sources, which can reduce the transmission loss, reduce the difficulty of controlling the grid connection of the AC power generation source, and reduce the controller cost , the difficulty of connecting the DC power generation source to the grid through the DC/DC converter is lower than that through the inverter, and the control cost is also reduced accordingly.

The network structure of the DC bus has great advantages in the connection between the micro-grid and the large-scale grid. When the grid is connected, the grid-connected inverter can be used to adjust the reactive power and active power of the micro-grid. This is very beneficial to the large power grid. .

Description of drawings

Fig. 1 Schematic diagram of micro-grid structure with DC bus.

Detailed ways

The present invention will be described in further detail below in conjunction with the accompanying drawings.

The DC bus mini-grid shown in Figure 1 includes a DC power source 1, an unsteady AC power source 3, a controllable power, a constant voltage AC power source 5, a DC load 15, an AC load 7, an inverter 8, Grid-connected inverter 16 , storage 11 , 13 , and system controller 14 .

(1) The voltage of the DC bus 9 is a constant voltage V set by the system controller, and the DC power generation source 1 (such as solar power generation) keeps the output voltage at a constant voltage V through the DC/DC converter 2, and the system controller 14 detects The output power of the DC power generation source gives a voltage maintenance instruction to the DC/DC converter 2 .

(2) The unsteady AC power generation source 3 (such as wind power generation) keeps the output voltage at a constant voltage V through the AC/DC converter 4. After the system controller 14 obtains the output power of the unsteady AC power generation source 3, a voltage is given A hold command is given to the AC/DC converter 4 .

(3) Controllable power, constant voltage AC power generation source 5 (such as natural gas power generation, diesel power generation, hydropower generation) keeps the output voltage at a constant voltage V through the AC/DC converter 6, and the system controller 14 detects the DC power generation source 1 , the voltage and output power of the AC generating source 3 and the voltage of the DC bus 9 are not constant, and a power command is sent to the AC generating source 5 to keep the bus voltage at a constant voltage V.

(4) The AC accumulator 11 and the DC accumulator 13 have the function of flattening the DC bus and maintaining the instantaneous voltage stability. When the DC bus voltage is higher than the constant voltage V, the AC accumulator 11 absorbs the grid energy through the DC/AC converter 10 At the same time, the DC storage 13 absorbs grid energy through the DC/DC converter 12. When the DC bus voltage is lower than the constant voltage V, the storage outputs energy to the grid to keep the DC bus voltage stable at the constant voltage V.

(5) The AC load 7 is connected to the DC bus 9 through the inverter 8 to absorb energy from the grid.

(6) The DC load 15 is directly connected to the DC bus 9 and absorbs energy from the bus. The DC bus 9 can also supply power to the DC load 15 through a DC/DC converter.

(7) The system controller 14 detects the output power and load power of all power generation sources. When the power output by the micro-grid is greater than the sum of the DC load and the AC load, and the micro-grid also has an output power adjustment margin, the grid-connected inverter 16 When it starts to work, the microgrid outputs power to the large grid; when the maximum output power of the microgrid is less than the sum of the loads, the grid-connected inverter starts to work and inputs energy from the large grid.

Claims (5)

1. A micro-grid networking method, characterized in that the AC power generation source is connected to the DC bus through the AC/DC converter, the DC power generation source is connected to the DC bus through the DC/DC converter, and the DC bus is inverted through the grid The AC/DC converter, DC/DC converter and grid-connected inverter are all controlled by the system controller. 2. The micro-grid networking method according to claim 1, characterized in that the AC power source includes an unsteady AC power source and a controllable power and voltage constant AC power source. 3. The networking method according to claim 2, characterized in that the energy storage is a DC energy storage, which is connected to the DC bus through a DC/DC converter. 4. The networking method according to claim 2, characterized in that the energy storage is an AC energy storage, which is connected to the DC bus through a DC/AC converter. 5. The networking method according to any one of claims 1 to 4, characterized in that the DC bus voltage is 300-500v.

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