CN113036804B

CN113036804B - AC/DC micro-grid control method and device

Info

Publication number: CN113036804B
Application number: CN202110303508.9A
Authority: CN
Inventors: 周强; 张亚平; 付勇
Original assignee: Xian Linchr New Energy Technology Co Ltd
Current assignee: Xian Linchr New Energy Technology Co Ltd
Priority date: 2021-03-22
Filing date: 2021-03-22
Publication date: 2024-01-26
Anticipated expiration: 2041-03-22
Also published as: CN113036804A; DE112021007351T5; WO2022199173A1

Abstract

The application is applicable to the technical field of micro-grids, and provides an alternating current/direct current micro-grid control method and device. The method is applied to an alternating-current/direct-current micro-grid, wherein the alternating-current/direct-current micro-grid comprises an alternating-current micro-grid, a direct-current micro-grid and a bidirectional converter, the alternating-current micro-grid is connected to a power distribution network through a grid connection point, and the bidirectional converter is electrically connected between the alternating-current micro-grid and the direct-current micro-grid, and the method comprises the following steps: detecting the power of the grid-connected point in real time; and if the power of the grid-connected point meets the preset anti-backflow protection triggering condition, controlling to disconnect the electric connection between the alternating-current micro-grid and the bidirectional converter. The AC/DC micro-grid control method can improve the reliability of load power supply.

Description

AC/DC micro-grid control method and device

Technical Field

The application belongs to the technical field of micro-grids, and particularly relates to an alternating current-direct current micro-grid control method and device.

Background

In recent years, distributed power sources (Distributed Generation, DG) have been increasingly attracting attention as an emerging power generation mode. The proposal of Micro-Grid aims to realize flexible and efficient application of distributed power sources and solve the Grid connection problem of the distributed power sources with huge quantity and various forms. As an advantageous complement to centralized power generation, the access location of the micro-grid is mainly in the vicinity of the distribution network users. However, in actual use, due to the fluctuation and instability of the distributed power generation, the magnitude and direction of the power flow of the user-side power distribution network will change, and the micro-grid may transmit power to the upper-level power distribution network, resulting in a change in the voltage distribution of the power distribution network. Thus, the distributed power system grid-tie management provision is successively taken out each time, wherein, in part, it is proposed: the energy storage power station user is not allowed to back-feed the power to the power grid (i.e., the grid connection is not on the net).

Aiming at the policies and the state of the art, the related researches put forward a micro-grid control method, which mainly monitors the power of a grid-connected point in real time, controls the micro-grid to work in an island mode when the power of the grid-connected point and an anti-backflow protection threshold meet a preset relation, and otherwise controls the micro-grid to work in a grid-connected mode.

However, in this micro grid control method, the micro grid system is frequently switched between the grid-connected mode and the island mode, reducing the reliability of load power supply.

Disclosure of Invention

The application provides a control method and device for an AC/DC micro-grid, which can solve the problem of low reliability of load power supply.

In a first aspect, an embodiment of the present application provides a method for controlling an ac/dc micro-grid, applied to an ac/dc micro-grid, where the ac micro-grid includes an ac micro-grid, a dc micro-grid, and a bidirectional converter, the ac micro-grid is connected to a power distribution network through a grid-connected point, and the bidirectional converter is electrically connected between the ac micro-grid and the dc micro-grid, the method includes:

detecting the power of the grid-connected point in real time;

and if the power of the grid-connected point meets the preset anti-backflow protection triggering condition, controlling to disconnect the electric connection between the alternating-current micro-grid and the bidirectional converter.

In one embodiment, with current flowing from the distribution network to the ac/dc micro grid as a positive direction, the anti-backflow protection triggering condition includes: the power of the grid-connected point is smaller than or equal to a first anti-backflow protection threshold value, wherein the first anti-backflow protection threshold value is larger than or equal to 0.

In one embodiment, the anti-reverse flow protection triggering condition further comprises: the duration that the power of the grid-connected point is smaller than or equal to the first anti-backflow protection threshold value is longer than the preset anti-backflow protection duration.

In one embodiment, after controlling to disconnect the ac microgrid from the bi-directional converter, the method further comprises:

and adjusting the power of the bidirectional converter to a preset power value, wherein the power of the grid connection point is larger than a first backflow prevention protection threshold value after the alternating current micro-grid is connected with the bidirectional converter under the preset power value.

if the power of the grid connection point meets the preset anti-backflow protection stop condition, controlling and recovering the electric connection between the alternating current micro-grid and the bidirectional converter; the anti-reflux protection stop conditions include: the power of the grid-connected point is larger than or equal to a second anti-backflow protection threshold value, wherein the second anti-backflow protection threshold value is larger than the first anti-backflow protection threshold value.

In one embodiment, the method further comprises:

and if the alternating current micro-grid is electrically connected with the bidirectional converter, the power of the grid connection point is larger than the first anti-backflow protection threshold value and smaller than the second anti-backflow protection threshold value, and the power of the bidirectional converter is regulated according to the second anti-backflow protection threshold value and the power of the grid connection point.

In one embodiment, the method further comprises:

and if the power of the grid-connected point does not meet the anti-backflow protection triggering condition, controlling the AC/DC micro-grid to operate according to a preset energy storage power generation plan.

In one embodiment, the ac micro-grid includes an ac load electrically connected to the grid-connected point, the dc micro-grid includes a power generation system, an energy storage system and a dc load electrically connected to the bidirectional converter, respectively, and the control ac/dc micro-grid operates according to a predetermined energy storage power generation plan, including:

according to an energy storage power generation plan, if the current moment is in an energy storage charging period and the electric quantity of an energy storage system is smaller than a first preset electric quantity threshold value, gradually adjusting the output power of the power generation system according to a first preset step length until the maximum power generation power is reached, and adjusting the power of the bidirectional converter according to the output power of the power generation system and the power of a direct current load so as to charge the energy storage system according to the planned charging power in the energy storage power generation plan;

If the current moment is in the energy storage charging period and the electric quantity of the energy storage system is larger than or equal to a first preset electric quantity threshold value, adjusting the output power of the power generation system to be equal to the sum of the power of the direct current load and the power of the alternating current load, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of the alternating current load.

In one embodiment, the method further comprises:

according to an energy storage power generation plan, if the current moment is in an energy storage discharge period and the electric quantity of the energy storage system is larger than a second preset electric quantity threshold value, gradually adjusting the output power of the power generation system according to a second preset step length until the maximum power generation power is reached, and gradually adjusting the power of the bidirectional converter according to a third preset step length according to the output power of the power generation system and the power of a direct current load so as to enable the energy storage system to discharge according to the planned discharge power in the energy storage power generation plan;

if the current moment is in the energy storage discharge period and the electric quantity of the energy storage system is smaller than or equal to a second preset electric quantity threshold value, the output power of the power generation system is gradually adjusted according to the second preset step length until the maximum power generation power is reached, and the power of the bidirectional converter is adjusted according to the output power of the power generation system and the power of the direct current load so that the discharge power of the energy storage system is 0.

In one embodiment, the method further comprises:

according to an energy storage power generation plan, if the current moment is in an energy storage standing period and the electric quantity of an energy storage system is smaller than a first preset electric quantity threshold value, gradually adjusting the output power of the power generation system according to a first preset step length until the maximum power generation power is reached, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of an alternating current load;

if the current moment is in the energy storage standing period and the electric quantity of the energy storage system is larger than or equal to a first preset electric quantity threshold value, adjusting the output power of the power generation system to be equal to the sum of the power of the direct current load and the power of the alternating current load, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of the alternating current load.

In a second aspect, an embodiment of the present application provides an ac/dc micro-grid control device, applied to an ac/dc micro-grid, where the ac/dc micro-grid includes an ac micro-grid, a dc micro-grid and a bidirectional converter, the ac micro-grid is connected to a power distribution network through a grid connection point, the bidirectional converter is electrically connected between the ac micro-grid and the dc micro-grid, and the ac/dc micro-grid control device includes:

the detection module is used for detecting the power of the grid-connected point in real time;

And the protection module is used for controlling to disconnect the electric connection between the alternating-current micro-grid and the bidirectional converter if the power of the grid-connected point meets the preset anti-backflow protection triggering condition.

In a third aspect, an embodiment of the present application provides an ac/dc micro-grid control device, including: a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the ac/dc microgrid control method of any one of the above first aspects when executing the computer program.

According to the AC/DC micro-grid control method and device, when the power of the grid connection point meets the preset anti-backflow protection triggering condition, the AC micro-grid is controlled to be disconnected from the bidirectional converter, the occurrence of reverse power is prevented, a reverse power protector is not required to be arranged, and the system construction cost is reduced. In addition, the direct-current micro-grid can normally supply power to the direct-current load through the internal energy storage system and the power generation system, and the alternating-current micro-grid continuously supplies power to the alternating-current load through the power distribution network, so that the alternating-current/direct-current micro-grid control method and the alternating-current micro-grid control device provided by the embodiment of the application can not influence the power supply of the alternating-current load and the direct-current load while preventing reverse-current protection, and the reliability of the power supply of the load is improved. In addition, for the power distribution network, when the anti-reverse power is protected, the alternating current load continues to take electricity, the power distribution network cannot be suddenly unloaded, excessive impact on the power distribution network cannot be caused, and the stability of the power distribution network is improved.

Drawings

In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings that are required for the embodiments or the description of the prior art will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present application, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.

Fig. 1 is a schematic structural diagram of an ac/dc micro-grid according to an embodiment of the present disclosure;

fig. 2 is a schematic flowchart of an ac/dc micro grid control method according to an embodiment of the present application;

fig. 3 is a schematic diagram of power regulation of the bidirectional converter according to the second anti-backflow protection threshold and the grid-connected point according to an embodiment of the present application;

FIG. 4 is a schematic flow chart of an energy storage charging period AC/DC micro grid control method according to an embodiment of the present application;

FIG. 5 is a schematic flow chart of an energy storage discharging period AC/DC micro-grid control method according to an embodiment of the present application;

FIG. 6 is a schematic flow chart of an energy storage standing period AC/DC micro-grid control method according to an embodiment of the present application;

Fig. 7 is a schematic structural diagram of an ac/dc micro-grid control device according to an embodiment of the present application.

Reference numerals illustrate:

AC/DC micro grid 10

AC micro-grid 110

Ac load 111

Second sampling device 112

DC micro-grid 120

DC bus 121

Power generation system 122

Photovoltaic power generation device 1221

Photovoltaic DC/DC 1222

Third sampling device 1223

Energy storage system 123

Energy storage device 1231

Energy storage DC/DC 1232

Fourth sampling device 1233

DC load 124

Fifth sampling device 1241

Bidirectional converter 130

Micro-grid control device 140

Distribution network 20

Step-down transformer 201

First sampling device 202

High voltage ac bus 203

Low voltage ac bus 204

Detailed Description

In order to make the objects, technical solutions and advantages of the present application more apparent, the present application will be further described in detail with reference to the accompanying drawings and examples. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the present application.

It is to be understood that the terms "first," "second," "third," "fourth," and the like in the embodiments of the present application, if any, are used for distinguishing between similar objects and not necessarily for describing a particular sequential or chronological order.

It is to be understood that the term "and/or" as used herein refers to any and all possible combinations of one or more of the associated listed items, and includes such combinations.

In the prior art, the phenomenon of countercurrent of an alternating current/direct current micro-grid is mainly prevented by the following two modes:

the first is to set an inverse power protector between the AC/DC micro-grid and the grid-connected point. This approach, while preventing backflow, is costly in the system.

The second is to realize the anti-reflux by controlling the AC/DC micro-grid. Specifically, by monitoring the power of the grid-connected point in real time, when the power of the grid-connected point triggers an anti-backflow protection threshold value, the micro-grid is controlled to be switched into an island mode, otherwise, the micro-grid is controlled to work in the grid-connected mode. The AC/DC micro-grid control method has two main problems:

1) The micro-grid is frequently switched between a grid-connected mode and an island mode, so that the reliability of load power supply is reduced;

2) The micro-grid is frequently switched between a grid-connected mode and an island mode, so that the micro-grid is frequently suddenly loaded and suddenly unloaded on the power distribution network, and a large impact is generated on the power distribution network.

The method and the device for controlling the AC/DC micro-grid aim to solve the problems.

The technical solutions in the present application will be described in detail below with reference to the accompanying drawings. It should be noted that, in the case of no conflict, different technical features may be combined with each other.

The AC/DC micro-grid control method provided by the embodiment of the application can be applied to the AC/DC micro-grid shown in FIG. 1, and is used for controlling the AC/DC micro-grid, preventing reverse flow (i.e. reverse power) and realizing grid connection without surfing the Internet. As shown in fig. 1, the ac/dc microgrid 10 includes an ac microgrid 110, a dc microgrid 120, a bidirectional converter 130, and an ac/dc microgrid control device (hereinafter referred to as a microgrid control device) 140. Ac microgrid 110 is connected to distribution network 20 via a grid-connected PCC and bi-directional converter 130 is electrically connected between ac microgrid 110 and dc microgrid 120. The grid-connected point PCC is also called a common connection point.

Specifically, a step-down transformer 201, a first sampling device 202, and a circuit breaker QF1 may be further disposed between the power distribution network 20 and the grid-connected point PCC in sequence. The distribution network 20 is connected to the step-down transformer 201 via a high voltage ac bus 203. The power distribution network 20 outputs high-voltage alternating current of 10kV or 35kV through a high-voltage alternating current bus 203, and the step-down transformer 201 steps down the high-voltage alternating current output by the power distribution network 20 to 400V alternating current and outputs the same through a low-voltage alternating current bus 204. The first sampling device 202 and the breaker QF1 are connected in series on a low voltage AC bus 204 between the step-down transformer 201 and the grid-tie point PCC. The first sampling device 202 is used for collecting signals such as voltage, current or power on a low-voltage ac bus 204 between the step-down transformer 201 and the grid-connected point PCC. The first sampling device 202 may be in signal connection with the micro-grid control device 140 through a measurement signal line, and transmit the collected measurement signal to the micro-grid control device 140. The breaker QF1 is used for controlling the on-off between the step-down transformer 201 and the grid-connected point PCC. The breaker QF1 can be connected with the micro-grid control device 140 through a switch signal line, and the breaker QF1 is controlled by the micro-grid control device 140 and can receive a switch signal sent by the micro-grid control device 140 to realize closing and opening.

The ac microgrid 110 may include an ac load 111 electrically connected to a low voltage ac bus 204. Optionally, the ac microgrid 110 may further comprise a second sampling device 112 and a breaker QF2. The second sampling device 112 and the breaker QF2 are connected between the ac load 111 and the low-voltage ac bus 204. The second sampling device 112 is used for collecting signals such as voltage, current or power on a line between the low-voltage ac bus 204 and the ac load 111. The second sampling device 112 may be in signal connection with the micro-grid control device 140 through a measurement signal line, and transmit the collected measurement signal to the micro-grid control device 140. The breaker QF2 is used to control the on-off between the low-voltage ac bus 204 and the ac load 111. The breaker QF2 can be connected with the micro-grid control device 140 through a switch signal wire, and the breaker QF2 is controlled by the micro-grid control device 140 and can receive a switch signal sent by the micro-grid control device 140 to realize closing and opening.

The bidirectional converter 130 may be an AC/DC converter, which is a device for converting voltage between an AC bus and a DC bus, and can implement bidirectional flow of AC/DC energy. That is, the bidirectional converter 130 may convert the ac power on the low-voltage ac BUS 204 into the DC power and output the DC power to the DC BUS (DC BUS) 121, or may convert the DC power on the DC BUS 121 into the ac power and output the ac power to the low-voltage DC BUS 204. The bi-directional converter 130 operates in a constant power mode. The bidirectional converter 130 can be connected with the micro-grid control device 140 through a communication signal line to realize the interaction of communication signals with the micro-grid control device 140.

For example, a circuit breaker QF3 may be provided between the ac micro grid 110 and the bidirectional converter 130. Specifically, the circuit breaker QF3 is disposed between the low voltage ac bus 204 and the bidirectional converter 130 in the ac micro grid 110. The breaker QF3 is used to control the on-off between the low voltage ac bus 204 and the bi-directional converter 130. The breaker QF3 can be connected with the micro-grid control device 140 through a switch signal wire, and the breaker QF3 is controlled by the micro-grid control device 140 and can receive a switch signal sent by the micro-grid control device 140 to realize closing and opening.

Alternatively, the dc micro-grid 120 may include a power generation system 122, an energy storage system 123, and a dc load 124 electrically connected to the dc load 121, respectively. Specifically, the power generation system 122 may be a photovoltaic power generation system, a wind power generation system, or both a photovoltaic power generation system and a wind power generation system. The embodiment of the present application will be described by taking the power generation system 122 as a photovoltaic power generation system as an example. The power generation system 122 may include a Photovoltaic (PV) device 1221 and a photovoltaic DC/DC 1222 connected to the photovoltaic device 1221. The photovoltaic DC/DC 1222 is a device for converting voltage between the direct current bus 121 and the photovoltaic power generation device 1221, and can realize bidirectional flow of energy between the photovoltaic power generation device 1221 and the direct current bus 121. The photovoltaic DC/DC 1222 operates in a maximum power point tracking (Maximum Power Point Tracking, MPPT) mode. The photovoltaic DC/DC 1222 can be connected to the micro-grid control device 140 through a communication signal line, and the maximum output power of the photovoltaic DC/DC 1222 is regulated and controlled by the micro-grid control device 140. Energy storage system 123 may include an energy storage (Energy Storage System, ESS) device 1231 and an energy storage DC/DC 1232 coupled to energy storage device 1231. The energy storage DC/DC 1232 may be connected to the micro-grid control device 140 through a communication signal line. The energy storage DC/DC 1232 is a device for converting voltage between the direct current bus 121 and the energy storage device 1231, and can realize bidirectional flow of energy between the energy storage device 1231 and the direct current bus 121. The energy storage DC/DC 1232 operates in a direct current bus regulated mode.

Optionally, a third sampling device 1223 and a breaker QF4 may be provided between the photovoltaic DC/DC 1222 and the direct current bus 121. The third sampling device 1223 is configured to collect signals such as voltage, current, or power on the line between the photovoltaic DC/DC 1222 and the direct current bus 121. The third sampling device 1223 may be in signal connection with the micro-grid control device 140 through a measurement signal line, and transmit the collected measurement signal to the micro-grid control device 140. The breaker QF4 is used to control the on-off between the photovoltaic DC/DC 1222 and the direct current bus 121. The breaker QF4 can be connected with the micro-grid control device 140 through a switch signal wire, and the breaker QF4 is controlled by the micro-grid control device 140 and can receive a switch signal sent by the micro-grid control device 140 to realize closing and opening.

Optionally, a fourth sampling device 1233 and a breaker QF5 may be provided between the stored energy DC/DC 1232 and the direct current bus 121. The fourth sampling device 1233 is configured to collect signals such as voltage, current, or power on a line between the energy storage DC/DC 1232 and the direct current bus 121. The fourth sampling device 1233 may be in signal connection with the micro-grid control device 140 through a measurement signal line, and transmit the collected measurement signal to the micro-grid control device 140. The breaker QF5 is used to control the on-off between the energy storage DC/DC 1232 and the direct current bus 121. The breaker QF5 can be connected with the micro-grid control device 140 through a switch signal wire, and the breaker QF5 is controlled by the micro-grid control device 140 and can receive a switch signal sent by the micro-grid control device 140 to realize closing and opening.

Optionally, a fifth sampling device 1241 and a breaker QF6 may be provided between the dc load 124 and the dc bus 121. The fifth sampling device 1241 is used for collecting signals such as voltage, current or power on the line between the dc load 124 and the dc bus 121. The fifth sampling device 1241 may be connected to the micro-grid control device 140 through a measurement signal line, and transmits the collected measurement signal to the micro-grid control device 140. The breaker QF6 is used to control the on-off between the dc load 124 and the dc bus 121. The breaker QF6 can be connected with the micro-grid control device 140 through a switch signal wire, and the breaker QF6 is controlled by the micro-grid control device 140 and can receive a switch signal sent by the micro-grid control device 140 to realize closing and opening.

The microgrid control device 140 is the "brain" of the ac/dc microgrid 10. The micro-grid control device 140 collects data such as voltage, current or power of each sampling point through the first sampling device 202, the second sampling device 112, the third sampling device 1223, the fourth sampling device 1233 and the fifth sampling device 1241, and remotely controls, adjusts, signals and the like the bidirectional converter 130, the power generation system 122 and the energy storage system 123 according to the data. Meanwhile, the micro-grid control device 140 performs opening or closing control of the circuit breaker QF1, the circuit breaker QF2, the circuit breaker QF3, the circuit breaker QF4, the circuit breaker QF5, or the circuit breaker QF6 based on these data.

It should be noted that, in the embodiment of the present application, the structures of each module, device, and apparatus in the ac/dc micro-grid 10 are not limited, and may be selected according to actual requirements. The micro-grid control device 140 may be a computer device, an upper computer, a programmable logic controller (Programmable Logic Controller, PLC), a microprocessor, or the like. The micro-grid control device 140 may include a memory, a processor, and a computer program stored in the memory and executable on the processor.

Fig. 2 shows a schematic flow chart of the ac/dc micro grid control method provided by the present application. The embodiment of the present application will be described by taking the application of the method to the micro-grid control device 140 in fig. 1 as an example. As shown in fig. 2, the method for controlling an ac/dc micro-grid provided in this embodiment may include:

s201, detecting the power P of the point of connection in real time _pcc 。

Alternatively, the current and the voltage of the sampling point can be collected through the first sampling device, and the micro-grid control device calculates the power P of the grid-connected point according to the current and the voltage of the sampling point _pcc 。

S202, if the power P of the point of connection _pcc And if the preset anti-backflow protection triggering condition is met, the electric connection between the alternating-current micro-grid and the bidirectional converter is controlled to be disconnected.

The anti-backflow protection triggering condition refers to a preset condition for triggering the anti-backflow protection. Optionally, the critical state of the reverse power can be determined as the anti-backflow protection triggering condition, and a certain safety value can be reserved on the basis of the critical state of the reverse power to determine the anti-backflow protection triggering condition.

Power P when the network is connected _pcc If the preset anti-backflow protection triggering condition is not met, the AC/DC micro-grid is considered to have no reverse power at the current moment, no anti-backflow protection is needed, and the AC/DC micro-grid works in a grid-connected state.

Power P when the network is connected _pcc And if the preset anti-backflow protection triggering condition is met, the AC/DC micro-grid at the current moment is considered to have the reverse power risk. The micro-grid control device controls the breaker QF3 to be opened, so that the electric connection between the alternating-current micro-grid and the bidirectional converter is disconnected. At the moment, the direct-current micro-grid is disconnected with the alternating-current micro-grid, the direct-current micro-grid can not output power to the grid-connected point any more, the power of the grid-connected point can not generate reverse power, and therefore the phenomenon of surfing the internet can not occur, and the situation is preventedThe occurrence of the reverse flow phenomenon is stopped.

Meanwhile, the direct-current micro-grid is disconnected with the alternating-current micro-grid, and a power generation system and an energy storage system in the direct-current micro-grid jointly provide energy required by a direct-current load, so that normal power supply can be provided for the direct-current load. On the other hand, after the direct-current micro-grid is disconnected from the alternating-current micro-grid, the direct-current micro-grid can keep self balance. Specifically, when the direct current load increases, the micro-grid control device controls the output power of the power generation system, and supplements the power on the direct current bus through the energy storage system. When the output of the power generation system is larger than the direct current load demand, the energy storage system absorbs redundant power. When the dc load decreases or suddenly unloads, the short-term imbalance that occurs within the dc microgrid may be supplemented by the energy storage system.

The direct-current micro-grid is disconnected from the alternating-current micro-grid, the alternating-current micro-grid is still connected with the grid connection point, and the power distribution network continues to supply power to the alternating-current load, so that the alternating-current load can keep working normally. For the power distribution network, the alternating current load continues to get electricity, the power distribution network is not unloaded, and excessive impact on the power distribution network is avoided.

In the conventional technology, when the grid-connected point power triggers the anti-backflow protection threshold, the micro-grid is switched to the island mode by opening a breaker at the grid-connected point, namely a breaker QF1, and at this time, the power supply of the alternating-current micro-grid cannot be ensured. And the breaker QF1 is disconnected, so that the power distribution network is suddenly unloaded, and a large impact is caused to the power distribution network. In the ac/dc micro-grid control method provided in this embodiment, the power P at the grid-connected point _pcc When the preset anti-backflow protection triggering condition is met, the electric connection between the alternating-current micro-grid and the bidirectional converter is controlled to be disconnected, the occurrence of reverse power is prevented, a reverse power protector is not required to be arranged, and the system construction cost is reduced. In addition, the direct-current micro-grid can normally supply power to the direct-current load through the internal energy storage system and the power generation system, and the alternating-current micro-grid continuously supplies power to the alternating-current load through the power distribution network, so that the alternating-current/direct-current micro-grid control method provided by the embodiment can not influence the power supply of the alternating-current load and the direct-current load while preventing reverse-current protection, and improves the reliability of the power supply of the load. In addition, for distribution networks When the anti-backflow protection is performed, alternating current loads continue to get electricity, sudden unloading can not occur in the power distribution network, excessive impact can not be caused to the power distribution network, and stability of the power distribution network is improved.

The anti-reverse flow protection trigger condition may be a preset power threshold. It can be appreciated that the anti-reflux protection triggering conditions are different when the set forward direction is different. The following embodiments describe a specific method for controlling the dc micro-grid and the anti-backflow protection triggering condition by taking the direction of the current flowing from the power distribution network to the ac/dc micro-grid in fig. 1 (i.e., the direction indicated by the arrow in fig. 1) as the positive direction.

In one embodiment, with the direction of current flowing from the distribution network to the ac/dc micro grid as the positive direction, the anti-backflow protection triggering condition may include: power P of the point of connection _pcc Less than or equal to the first anti-reflux protection threshold value P ₁ . First anti-reflux protection threshold value P ₁ Is a preset fixed power value with direction. In one embodiment, the anti-reflux protection threshold may be 0. In another embodiment, the anti-reflux protection threshold may also be a value greater than 0. The anti-backflow protection threshold is used for judging whether the anti-backflow protection method is triggered or not, so that the anti-backflow protection efficiency can be improved.

Further, in one embodiment, the anti-reverse flow protection triggering condition may further include: power P of the point of connection _pcc Less than or equal to the first anti-reflux protection threshold value P ₁ The duration of which is longer than a preset anti-reflux protection duration. That is, when the power of the point of connection is less than or equal to the first protection threshold P against reverse flow ₁ And if the duration is longer than the anti-backflow protection duration, triggering the anti-backflow protection action, and controlling to disconnect the electric connection between the alternating current micro-grid and the bidirectional converter. The anti-backflow protection duration can be set according to practical situations, for example, can be 5s, 10s or 20 s. In this embodiment, by setting the duration factor in the anti-backflow protection triggering condition, the grid-connected point power P caused by the micro-grid abnormality can be effectively prevented _pcc The conditions such as occasional fluctuation and the like are misjudged to be countercurrent, and the backflow prevention protection is triggered by mistake, so that the accuracy and the safety of the backflow prevention protection of the micro-grid can be improved.

In one embodiment, after step S202, the method further includes: adjusting the power of the bidirectional converter to a preset power value, wherein when the AC micro-grid is connected with the bidirectional converter under the preset power value, the power P of the grid connection point is adjusted _pcc Is greater than a first anti-reflux protection threshold value P ₁ . Alternatively, the preset power value may be 0. Thus, when the breaker QF3 is closed again, the direct-current micro-grid does not output negative power to the grid-connected point or consume the power output by the grid-connected point after the alternating-current micro-grid is electrically reconnected with the bidirectional converter. Power P of the point of connection _pcc The power of the alternating current load is subtracted from the power output by the distribution network. Therefore, the phenomenon of countercurrent does not occur after the alternating-current micro-grid is electrically reconnected with the bidirectional converter, and the safety of the power distribution network is guaranteed. Moreover, the preset power value is a fixed value, the bidirectional converter is used as a controlled power source and works in a constant power mode, and the power of the bidirectional converter is not influenced by fluctuation of other loads, so that power mutation of grid connection points is avoided, and the stability of a micro-grid and a power distribution network is ensured.

In one embodiment, after step S202, the method further includes:

if the power P of the point of connection _pcc And if the preset anti-backflow protection stopping condition is met, controlling and recovering the electric connection between the alternating-current micro-grid and the bidirectional converter.

Specifically, after the breaker QF3 is disconnected, the bidirectional converter does not consume the power of the grid-connected point any more and does not transmit the power in the negative direction to the grid-connected point any more, so that the power P of the grid-connected point _pcc Will gradually recover. Power P when the network is connected _pcc And when the preset reverse flow protection stopping condition is met, the micro-grid control device controls the closing circuit breaker QF3 to recover the electric connection between the alternating current micro-grid and the bidirectional converter, so that the timely grid connection is ensured when the grid connection condition is met, and the stability and the reliability of the alternating current/direct current micro-grid are further improved.

Alternatively, the anti-reverse flow protection stop condition may correspond to an anti-reverse flow protection trigger condition, and may be, for example: power P of the point of connection _pcc Is greater than a first anti-reflux protection threshold value P ₁ . Optionally, the anti-reflux protection stop condition can also beThe method comprises the following steps: power P of the point of connection _pcc Greater than or equal to the second anti-reflux protection threshold value P ₂ Wherein the second anti-reflux protection threshold value P ₂ Is greater than a first anti-reflux protection threshold value P ₁ . In other words, the reverse flow prevention protection stop condition is: at the first anti-reflux protection threshold value P ₁ On the basis of (1) a certain safety range (namely a second anti-reflux protection threshold value P ₂ With a first anti-reflux protection threshold value P ₁ And the difference of the power grid is improved), so that the risk of reverse power after the AC/DC micro-grid is restored again can be reduced, and the stability of the AC/DC micro-grid is further improved.

In one embodiment, when the ac micro-grid is electrically connected with the bidirectional converter, i.e. when the ac/dc micro-grid is in grid-connected state, the grid-connected power P _pcc Meeting the preset anti-reflux protection boundary condition, according to the anti-reflux protection boundary condition and the power P of the point of connection _pcc Regulating the power P of a bidirectional converter _ACDC . The anti-backflow protection boundary conditions are used for limiting and screening the non-triggered anti-backflow protection triggering conditions, but the condition of the anti-backflow protection stopping conditions is not met. That is, the reverse-flow prevention protection boundary condition is a condition between the reverse-flow prevention protection trigger condition and the reverse-flow prevention protection stop condition. In a specific embodiment, the anti-reflux boundary conditions are: power P of the point of connection _pcc Is greater than a first anti-reflux protection threshold value P ₁ And is smaller than a second anti-reflux protection threshold value P ₂ 。

Due to P _PCC ＝P _{AC_Load} +P _ACDC The bidirectional converter is used as a controlled power source, and the power P at the grid-connected point _pcc When the anti-backflow protection boundary condition is met, according to the second anti-backflow protection threshold value P ₂ And power P of the point of parallel connection _PCC Regulating the power P of a bidirectional converter _ACDC . By regulating the power P of the bi-directional converter _ACDC The power P of the point of connection can be quickly adjusted _pcc Ensure the power P of the point of connection _pcc The risk of reverse power of the AC/DC micro-grid is greatly reduced.

Specifically, FIG. 3 illustrates an embodiment according to a second anti-refluxProtection threshold P ₂ And power P of the point of parallel connection _pcc Regulating the power P of a bidirectional converter _ACDC Is a schematic diagram of the principle of (a). As shown in fig. 3, a second anti-reflux protection threshold value P ₂ Given the power P of the grid connection point at the current time _PCC As feedback, the two are subjected to PI (proportional plus integral) adjustment after difference, and then the PI adjustment output is limited in amplitude, P _{ACDC_Set} Power P as bi-directional converter _ACDC Is set at a set value of (a). By PI regulation, in the first aspect, the power P of the point of connection can be realized _pcc Is provided for the rapid adjustment of (a). In the second aspect, since the power of the bidirectional converter is equal to the power P of the DC load _PV Power P of energy storage system _ESS And the output power P of the power generation system _PV The sum, P _ACDC ＝P _{DC_Load} +P _ESS +P _PV Regulating bi-directional converter output power P _ACDC The direct current micro-grid can realize power self-balancing, and the power generation output of the power generation system is not affected. Compared with the mode that the energy storage system and the power generation system respectively regulate the power through separate converters in the prior art, the method provided by the embodiment does not need to regulate the power of the energy storage system and the power generation system, can simply and rapidly realize the grid-connected point power regulation, can not be influenced by the power generation output, and fully exerts the advantage of the energy storage system as a voltage source.

It can be appreciated that when the power P of the point of connection is _pcc Greater than or equal to the second anti-reflux protection threshold value P ₂ When the control mode is exited; power P when the network is connected _pcc Less than or equal to the first anti-reflux protection threshold value P ₁ When the adjustment mode is exited, and step S202 is repeated.

The method for controlling the ac/dc micro-grid further includes a process of controlling the operation of the ac/dc micro-grid according to the energy storage power generation plan, and is described in detail below with reference to the embodiments.

In one embodiment, the method further comprises:

if the power P of the point of connection _pcc And if the preset anti-backflow protection triggering condition is not met, controlling the AC/DC micro-grid to operate according to a preset energy storage power generation plan.

Specifically, the power P at the grid-connected point _pcc Is greater than a second anti-reflux protection threshold value P ₂ The method comprises the following steps: and when the AC/DC micro-grid is in a grid-connected state and no reverse power risk exists, controlling the AC/DC micro-grid to operate according to a preset energy storage power generation plan. The energy storage power generation plan can be formulated in advance according to the set peak-valley time period, electricity price, other source load storage data and the like. In the energy storage power generation plan, the energy storage power generation plan is divided according to time periods and can comprise an energy storage charging period, an energy storage discharging period and an energy storage standing period. The following further describes the ac/dc microgrid control in each period with reference to the accompanying drawings:

1) Energy storage charging period

Fig. 4 is a schematic flowchart of an energy storage charging period ac/dc micro-grid control method according to an embodiment of the present application. As shown in fig. 4, the controlling the ac/dc micro-grid to operate according to the preset energy storage power generation plan may include:

according to the energy storage power generation plan, if the current time is in the energy storage charging period, step S401 is executed.

S401, judging whether the electric quantity of the energy storage system is smaller than a first preset electric quantity threshold value.

The first preset charge threshold is used to characterize whether the current battery charge is near full charge. The electric quantity of the energy storage system is larger than or equal to a first preset electric quantity threshold value, and the current electric quantity of the battery is more and is close to full electric quantity. The electric quantity of the energy storage system is smaller than a first preset electric quantity threshold value, which indicates that the current electric quantity is smaller and is not close to the full electric quantity.

If the electric quantity of the energy storage system is smaller than the first preset electric quantity threshold value, executing step S402; otherwise, step S403 is executed.

S402, according to a first preset step length delta P _PV1 Stepwise adjustment of the output power P of a power generation system _PV Until reaching the maximum power generation, and according to the output power P of the power generation system _PV And power P of dc load _{DC_Load} Adjusting the power P of a bidirectional converter _ACDC So that the energy storage system charges the power P according to the energy storage power generation plan _{ESS_Plan1} And (5) charging.

According to a first preset step length delta P _PV1 Stepwise adjustment of the output power P of a power generation system _PV Until the maximum power is reached, the output power P of the power generation system can be prevented _PV Abrupt change results in power P of the point of connection _pcc Abrupt triggering anti-reflux protection can ensure the stability of the AC/DC micro-grid. It should be noted that, for the photovoltaic power generation system, the photovoltaic maximum power limit value may be gradually increased until the maximum power tracking point is reached.

Due to P _ACDC ＝P _{DC_Load} +P _ESS +P _PV According to the output power P of the power generation system _PV And power P of dc load _{DC_Load} Adjusting and adjusting power P of bidirectional converter in real time _ACDC So that P _ESS ＝P _{ESS_Plan1} 。

S403, adjusting the output power P of the power generation system _PV Power P equal to dc load _{DC_Load} And power P of AC load _{AC_Load} And adjusting the power of the bidirectional converter to be equal to the power P of the alternating current load _{AC_Load} Is a counter number to the above.

That is, if the current time is in the energy storage charging period and the electric quantity of the energy storage system is greater than or equal to the first preset electric quantity threshold value, the micro-grid control device adjusts the output power P of the power generation system _PV ＝P _{AC_Load} +P _{DC_Load} . For a photovoltaic power generation system, the photovoltaic tracking load output can be performed by limiting the photovoltaic maximum power limit. Meanwhile, the micro-grid control device adjusts the power P of the bidirectional converter in real time _ACDC ＝-P _{AC_Load} I.e. the bi-directional converter tracks the ac load output.

2) Period of energy storage discharge

Fig. 5 is a schematic flowchart of an energy storage discharging period ac/dc micro-grid control method according to an embodiment of the present application. As shown in fig. 5, the controlling the ac/dc micro-grid to operate according to the preset energy storage power generation plan may include:

according to the energy storage power generation plan, if the current moment is in the energy storage discharge period, executing step S501;

s501, judging whether the electric quantity of the energy storage system is larger than a second preset electric quantity threshold value, if so, executing S502, otherwise, executing S503.

The second preset charge threshold is used to characterize whether the current battery charge is near empty. The electric quantity of the energy storage system is smaller than a second preset electric quantity threshold value, which indicates that the current electric quantity of the battery is smaller and is close to emptying. The electric quantity of the energy storage system is larger than or equal to a second preset electric quantity threshold value, which indicates that the current electric quantity is more and is not close to emptying.

S502, according to a second preset step length delta P _PV2 Stepwise adjustment of the output power P of a power generation system _PV Until reaching the maximum power generation, and according to the output power P of the power generation system _PV And power P of dc load _{DC_Load} According to a third preset step length delta P _ACDC Stepwise adjustment of the power P of a bidirectional converter _ACDC So that the energy storage system discharges power P according to the energy storage power generation plan _{ESS_Plan2} And (5) discharging.

According to a second preset step length delta P _PV2 Stepwise adjustment of the output power P of a power generation system _PV The specific process and beneficial effects until the maximum generated power is reached refer to the above step S402, and are not described herein. Wherein the second preset step length delta P _PV2 Can be equal to a first preset step length delta P _PV1 The same or different.

Due to P _ACDC ＝P _{DC_Load} +P _ESS +P _PV According to a third preset step length delta P _ACDC Stepwise adjustment of the power P of a bidirectional converter _ACDC Thereby being capable of reaching P _ESS ＝P _{ESS_Plan2} . Here, according to the third preset step Δp _ACDC Stepwise adjustment of the power P of a bidirectional converter _ACDC Can prevent the power P of the energy storage system _ESS Abrupt or too rapid a change results in grid tie point power P _PCC The abrupt change triggers reverse power protection, so that the stability of the AC/DC micro-grid can be ensured.

S503, according to the second preset step length delta P _PV2 Stepwise adjustment of the output power P of a power generation system _PV Until the maximum power is reached, according toOutput power P of power generation system _PV And power P of dc load _{DC_Load} Adjusting the power P of a bidirectional converter _ACDC So that the discharge power of the energy storage system is 0.

In this step, the output power P of the power generation system is regulated _PV The principle, beneficial effects, etc. are similar to those of step S502, except that the power P of the bi-directional converter is regulated in step S502 _ACDC Is aimed at making P _ESS ＝P _{ESS_Plan2} In this step, the power P of the bidirectional converter is regulated _ACDC Is aimed at making P _ESS ＝0。

3) Energy storage standing period

Fig. 6 is a schematic flowchart of an energy storage standing period ac/dc micro-grid control method according to an embodiment of the present application. As shown in fig. 6, the controlling the ac/dc micro-grid to operate according to the preset energy storage power generation plan may include:

and according to the energy storage power generation plan, if the current moment is in the energy storage standing period, executing step S601.

S601, judging that the electric quantity of the energy storage system is smaller than a first preset electric quantity threshold, executing step S602 if the electric quantity of the energy storage system is smaller than the first preset electric quantity threshold, otherwise executing step S603.

This step is step S401, and will not be described in detail herein.

S602, according to a first preset step length delta P _PV1 Stepwise adjustment of the output power P of a power generation system _PV Until reaching the maximum power generation, and adjusting the power P of the bidirectional converter _ACDC Power P equal to ac load _{AC_Load} Is a counter number to the above.

According to a first preset step length delta P _PV1 Stepwise adjustment of the output power P of a power generation system _PV The specific process and the beneficial effects until the maximum generated power is reached refer to step S402, and are not described herein.

Adjusting P _ACDC So that P _{ACDC_Set} ＝-P _{AC_Load} I.e. the bi-directional converter tracks the ac load output.

S603, adjusting the output power P of the power generation system _PV Equal toPower P of dc load _{DC_Load} And power P of AC load _{AC_Load} And adjusting the power of the bidirectional converter to be equal to the power of the alternating current load.

The process and the beneficial effects of this step are the same as step S403, and are not described here again.

In the embodiment, the AC/DC micro-grid is controlled to operate according to a preset energy storage power generation plan, so that energy time shifting and power distribution capacity increasing of the energy storage system can be fully exerted, and the utilization rate of the energy storage system is improved. Meanwhile, the utility value of the AC/DC micro-grid can be improved through peak clipping and valley filling.

It should be understood that, although the steps in the flowcharts of fig. 2 and 4-6 are shown in order as indicated by the arrows, these steps are not necessarily performed in order as indicated by the arrows. The steps are not strictly limited to the order of execution unless explicitly recited herein, and the steps may be executed in other orders. Moreover, at least some of the steps of fig. 2, 4-6 may include multiple sub-steps or stages that are not necessarily performed at the same time, but may be performed at different times, nor does the order in which the sub-steps or stages are performed necessarily occur in sequence, but may be performed alternately or alternately with other steps or at least a portion of the sub-steps or stages of other steps.

Fig. 7 shows a block diagram of an ac/dc micro-grid control device according to an embodiment of the present application. As shown in fig. 7, the ac/dc micro-grid control device provided in this embodiment may include:

the detection module 701 is configured to detect the power of the point of connection in real time;

the protection module 702 is configured to control to disconnect the electrical connection between the ac micro-grid and the bidirectional converter if the power of the grid-connected point meets a preset anti-reverse current protection triggering condition.

In one embodiment, the protection module 702 is further configured to adjust the power of the bidirectional converter to a preset power value, where, at the preset power value, the power of the grid-connected point is greater than the first anti-backflow protection threshold after the ac micro-grid is connected to the bidirectional converter.

In one embodiment, the ac/dc micro-grid control device further includes a recovery module 703, configured to control and recover the electrical connection between the ac micro-grid and the bidirectional converter if the power of the grid-connected point meets a preset anti-backflow protection stop condition; the anti-reflux protection stop conditions include: the power of the grid-connected point is larger than or equal to a second anti-backflow protection threshold value, wherein the second anti-backflow protection threshold value is larger than the first anti-backflow protection threshold value.

In one embodiment, the ac/dc micro-grid control device further includes a regulation module 704 configured to regulate the power of the bidirectional converter according to the second anti-backflow protection threshold and the power of the grid-connected point if the ac micro-grid is electrically connected with the bidirectional converter and the power of the grid-connected point is greater than the first anti-backflow protection threshold and less than the second anti-backflow protection threshold.

In one embodiment, the ac/dc micro-grid control device further includes an energy storage planning module 705, configured to control the ac/dc micro-grid to operate according to a preset energy storage power generation plan if the power of the grid-connected point does not meet the anti-backflow protection triggering condition.

In one embodiment, the energy storage planning module 705 is specifically configured to, according to an energy storage power generation plan, if the current moment is in an energy storage charging period and the electric quantity of the energy storage system is smaller than a first preset electric quantity threshold, gradually adjust the output power of the power generation system according to a first preset step length until the maximum power generation power is reached, and adjust the power of the bidirectional converter according to the output power of the power generation system and the power of the dc load, so that the energy storage system charges according to the planned charging power in the energy storage power generation plan; if the current moment is in the energy storage charging period and the electric quantity of the energy storage system is larger than or equal to a first preset electric quantity threshold value, adjusting the output power of the power generation system to be equal to the sum of the power of the direct current load and the power of the alternating current load, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of the alternating current load.

In one embodiment, the energy storage planning module 705 is specifically configured to, according to an energy storage power generation plan, if the current moment is in an energy storage discharge period and the electric quantity of the energy storage system is greater than a second preset electric quantity threshold, step-by-step adjust the output power of the power generation system according to a second preset step length until the maximum power generation power is reached, and step-by-step adjust the power of the bidirectional converter according to a third preset step length according to the output power of the power generation system and the power of the dc load, so that the energy storage system discharges according to the planned discharge power in the energy storage power generation plan; if the current moment is in the energy storage discharge period and the electric quantity of the energy storage system is smaller than or equal to a second preset electric quantity threshold value, the output power of the power generation system is gradually adjusted according to the second preset step length until the maximum power generation power is reached, and the power of the bidirectional converter is adjusted according to the output power of the power generation system and the power of the direct current load so that the discharge power of the energy storage system is 0.

In one embodiment, the energy storage planning module 705 is specifically configured to, according to an energy storage power generation plan, if the current moment is in an energy storage standing period and the electric quantity of the energy storage system is smaller than a first preset electric quantity threshold, gradually adjust the output power of the power generation system according to a first preset step length until the maximum power generation power is reached, and adjust the opposite number of the power of the bidirectional converter equal to the power of the ac load; if the current moment is in the energy storage standing period and the electric quantity of the energy storage system is larger than or equal to a first preset electric quantity threshold value, adjusting the output power of the power generation system to be equal to the sum of the power of the direct current load and the power of the alternating current load, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of the alternating current load.

The ac/dc micro-grid control device provided in this embodiment is configured to execute the ac/dc micro-grid control method provided in the method embodiment of the present application, and the technical principle and the technical effect are similar, and specifically, reference may be made to the method embodiment section, and details are not repeated herein.

It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-described division of the functional units and modules is illustrated, and in practical application, the above-described functional distribution may be performed by different functional units and modules according to needs, i.e. the internal structure of the apparatus is divided into different functional units or modules to perform all or part of the above-described functions. The functional units and modules in the embodiment may be integrated in one processing unit, or each unit may exist alone physically, or two or more units may be integrated in one unit, where the integrated units may be implemented in a form of hardware or a form of a software functional unit. In addition, specific names of the functional units and modules are only for convenience of distinguishing from each other, and are not used for limiting the protection scope of the present application. The specific working process of the units and modules in the above system may refer to the corresponding process in the foregoing method embodiment, which is not described herein again.

The embodiment of the application also provides an alternating current-direct current micro-grid control device, which comprises: a processor, a memory and a computer program stored in the memory and executable on the processor, the processor implementing the steps of any of the method embodiments described above when the computer program is executed.

It should be clear that the process, principle, and beneficial effects of executing the computer program by the processor in the embodiments of the present application are consistent with the execution of the steps in the above method, and specific reference may be made to the foregoing description.

The present application also provides a computer readable storage medium storing a computer program which, when executed by a processor, performs the steps of any of the method embodiments described above.

Those skilled in the art will appreciate that any reference to memory, storage, database, or other medium used in the various embodiments provided herein may include non-volatile and/or volatile memory. The nonvolatile memory can include Read Only Memory (ROM), programmable ROM (PROM), electrically Programmable ROM (EPROM), electrically Erasable Programmable ROM (EEPROM), or flash memory. Volatile memory can include Random Access Memory (RAM) or external cache memory. By way of illustration and not limitation, RAM is available in a variety of forms such as Static RAM (SRAM), dynamic RAM (DRAM), synchronous DRAM (SDRAM), double Data Rate SDRAM (DDRSDRAM), enhanced SDRAM (ESDRAM), synchronous Link DRAM (SLDRAM), memory bus direct RAM (RDRAM), direct memory bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM), among others.

The technical features of the above embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.

The above embodiments are only for illustrating the technical solution of the present application, and are not limiting; although the present application has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical scheme described in the foregoing embodiments can be modified or some technical features thereof can be replaced by equivalents; such modifications and substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present application, and are intended to be included in the scope of the present application.

Claims

1. An ac/dc micro-grid control method, which is characterized by being applied to an ac/dc micro-grid, wherein the ac/dc micro-grid comprises an ac micro-grid, a dc micro-grid and a bidirectional converter, the ac micro-grid is connected to a power distribution network through a grid connection point, and the bidirectional converter is electrically connected between the ac micro-grid and the dc micro-grid, the method comprises:

Detecting the power of the grid-connected point in real time;

if the power of the grid connection point meets a preset anti-backflow protection triggering condition, controlling to disconnect the electric connection between the alternating current micro-grid and the bidirectional converter; under the condition that the alternating-current micro-grid is electrically disconnected with the bidirectional converter, adjusting the power of the bidirectional converter to a preset power value, wherein under the preset power value, the power of the grid-connected point is larger than a first anti-backflow protection threshold value after the alternating-current micro-grid is connected with the bidirectional converter; and taking the current flowing from the power distribution network to the AC/DC micro-grid as a positive direction, wherein the anti-backflow protection triggering condition comprises: the power of the grid-connected point is smaller than or equal to a first anti-backflow protection threshold value, wherein the first anti-backflow protection threshold value is larger than or equal to 0;

if the power of the grid-connected point is larger than the first anti-backflow protection threshold and smaller than a second anti-backflow protection threshold, adjusting the power of the bidirectional converter according to the second anti-backflow protection threshold and the power of the grid-connected point; the second anti-reflux protection threshold is greater than the first anti-reflux protection threshold.

2. The method of claim 1, wherein the anti-reverse flow protection trigger condition further comprises: and the duration time that the power of the grid-connected point is smaller than or equal to the first anti-backflow protection threshold value is longer than the preset anti-backflow protection duration time.

3. The method of claim 1 or 2, wherein after the controlling disconnects the ac microgrid from the bi-directional converter, the method further comprises:

under the condition that the alternating-current micro-grid is electrically disconnected from the bidirectional converter, if the power of the grid-connected point meets the preset anti-backflow protection stopping condition, controlling and recovering the electric connection between the alternating-current micro-grid and the bidirectional converter; the anti-reflux protection stop condition includes: and the power of the grid-connected point is larger than or equal to the second anti-backflow protection threshold value.

4. The method according to claim 1 or 2, characterized in that the method further comprises:

and under the condition that the alternating current micro-grid is electrically connected with the bidirectional converter, if the power of the grid-connected point is larger than the second anti-backflow protection threshold value, controlling the alternating current/direct current micro-grid to operate according to a preset energy storage power generation plan.

5. The method of claim 4, wherein the ac microgrid comprises an ac load electrically connected to the grid connection point, the dc microgrid comprises a power generation system, an energy storage system, and a dc load electrically connected to the bi-directional converter, respectively, and the controlling the ac/dc microgrid to operate according to a pre-established energy storage power generation schedule comprises:

According to the energy storage power generation plan, if the current moment is in an energy storage charging period and the electric quantity of the energy storage system is smaller than a first preset electric quantity threshold value, gradually adjusting the output power of the power generation system according to a first preset step length until the maximum power generation power is reached, and adjusting the power of the bidirectional converter according to the output power of the power generation system and the power of the direct current load so as to charge the energy storage system according to the planned charging power in the energy storage power generation plan;

and if the current moment is in the energy storage charging period and the electric quantity of the energy storage system is larger than or equal to the first preset electric quantity threshold value, adjusting the output power of the power generation system to be equal to the sum of the power of the direct current load and the power of the alternating current load, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of the alternating current load.

6. The method of claim 5, wherein the method further comprises:

according to the energy storage power generation plan, if the current moment is in an energy storage discharge period and the electric quantity of the energy storage system is larger than a second preset electric quantity threshold value, gradually adjusting the output power of the power generation system until the maximum power generation power is reached according to a second preset step length, and gradually adjusting the power of the bidirectional converter according to the output power of the power generation system and the power of the direct current load according to a third preset step length so as to enable the energy storage system to discharge according to the planned discharge power in the energy storage power generation plan;

And if the current moment is in the energy storage discharge period and the electric quantity of the energy storage system is smaller than or equal to the second preset electric quantity threshold value, gradually adjusting the output power of the power generation system according to the second preset step length until the maximum power generation power is reached, and adjusting the power of the bidirectional converter according to the output power of the power generation system and the power of the direct current load so as to enable the discharge power of the energy storage system to be 0.

7. The method of claim 5, wherein the method further comprises:

according to the energy storage power generation plan, if the current moment is in an energy storage standing period and the electric quantity of the energy storage system is smaller than the first preset electric quantity threshold value, gradually adjusting the output power of the power generation system according to the first preset step length until the maximum power generation power is reached, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of the alternating current load;

and if the current moment is in the energy storage standing period and the electric quantity of the energy storage system is larger than or equal to the first preset electric quantity threshold value, adjusting the output power of the power generation system to be equal to the sum of the power of the direct current load and the power of the alternating current load, and adjusting the power of the bidirectional converter to be equal to the opposite number of the power of the alternating current load.

8. The utility model provides an alternating current-direct current micro grid controlling means, its characterized in that is applied to alternating current-direct current micro grid, alternating current-direct current micro grid includes alternating current micro grid, direct current micro grid and two-way converter, wherein, alternating current micro grid inserts the distribution network through the grid connection point, two-way converter electricity is connected in between alternating current micro grid and the direct current micro grid, alternating current-direct current micro grid controlling means includes:

the protection module is used for controlling to disconnect the electric connection between the alternating current micro-grid and the bidirectional converter if the power of the grid-connected point meets the preset anti-backflow protection triggering condition; under the condition that the alternating-current micro-grid is electrically disconnected with the bidirectional converter, adjusting the power of the bidirectional converter to be a preset power value; the power of the grid-connected point is larger than a first anti-backflow protection threshold value after the alternating-current micro-grid is connected with the bidirectional converter under the preset power value; and taking the current flowing from the power distribution network to the AC/DC micro-grid as a positive direction, wherein the anti-backflow protection triggering condition comprises: the power of the grid-connected point is smaller than or equal to a first anti-backflow protection threshold value, wherein the first anti-backflow protection threshold value is larger than or equal to 0;

The protection module is further configured to adjust the power of the bidirectional converter according to the second anti-backflow protection threshold and the power of the grid-connected point if the power of the grid-connected point is greater than the first anti-backflow protection threshold and less than the second anti-backflow protection threshold; the second anti-reflux protection threshold is greater than the first anti-reflux protection threshold.

9. An ac/dc microgrid control device comprising a memory, a processor and a computer program stored in the memory and executable on the processor, the processor implementing the method according to any one of claims 1 to 7 when executing the computer program.