CN113036804A - AC/DC micro-grid control method and device - Google Patents

AC/DC micro-grid control method and device Download PDF

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Publication number
CN113036804A
CN113036804A CN202110303508.9A CN202110303508A CN113036804A CN 113036804 A CN113036804 A CN 113036804A CN 202110303508 A CN202110303508 A CN 202110303508A CN 113036804 A CN113036804 A CN 113036804A
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China
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power
grid
energy storage
microgrid
bidirectional converter
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CN202110303508.9A
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CN113036804B (en
Inventor
周强
张亚平
付勇
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Xian Linchr New Energy Technology Co Ltd
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Xian Linchr New Energy Technology Co Ltd
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Priority to CN202110303508.9A priority Critical patent/CN113036804B/en
Publication of CN113036804A publication Critical patent/CN113036804A/en
Priority to DE112021007351.6T priority patent/DE112021007351T5/en
Priority to PCT/CN2021/141325 priority patent/WO2022199173A1/en
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H02J7/35—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering with light sensitive cells
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J7/00—Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
    • H02J7/34—Parallel operation in networks using both storage and other dc sources, e.g. providing buffering
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2310/00—The network for supplying or distributing electric power characterised by its spatial reach or by the load
    • H02J2310/10—The network having a local or delimited stationary reach

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The application is suitable for 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 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-connected point, and the bidirectional converter is electrically connected between the AC micro-grid and the DC micro-grid, and the method comprises the following steps: detecting the power of a grid-connected point in real time; and if the power of the grid-connected point meets the preset anti-reflux protection triggering condition, controlling to disconnect the electric connection between the alternating-current micro-grid and the bidirectional converter. The alternating current-direct current 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 Generation (DG) has gradually attracted attention as an emerging power Generation mode. The Micro-Grid (Micro-Grid) is provided, which aims to realize flexible and efficient application of the distributed power supply and solve the Grid connection problem of the distributed power supplies with huge quantity and various forms. As a beneficial complement to centralized power generation, the access location of the microgrid is primarily near the users of the power distribution grid. 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 power distribution network at the user side will be changed, and the micro-grid may transmit power to the super-distribution power grid, so that the voltage distribution of the power distribution network itself is changed. Therefore, the grid-connected management regulations of the distributed power system are provided in each place, and part of the regulations are as follows: the energy storage power station user does not allow the reverse power transmission to the power grid (namely grid connection and no network connection).
Aiming at the current policies and technical situations, a microgrid control method provided by related researches mainly monitors the power of a grid-connected point in real time, and controls a microgrid to work in an island mode when the power of the grid-connected point and a backflow prevention protection threshold value meet a preset relation, or otherwise controls the microgrid to work in a grid-connected mode.
However, in the microgrid control method, the microgrid system is frequently switched between a grid-connected mode and an island mode, so that the reliability of load power supply is reduced.
Disclosure of Invention
The application provides an alternating current-direct current micro-grid control method and device, which can solve the problem of low reliability of load power supply.
In a first aspect, an embodiment of the present application provides an ac/dc microgrid control method, which is applied to an ac/dc microgrid, the ac/dc microgrid includes an ac microgrid, a dc microgrid, and a bidirectional converter, wherein the ac microgrid is connected to a power distribution network through a grid-connected point, and the bidirectional converter is electrically connected between the ac microgrid and the dc microgrid, and the method includes:
detecting the power of a grid-connected point in real time;
and if the power of the grid-connected point meets the preset anti-reflux protection triggering condition, controlling to disconnect the electric connection between the alternating-current micro-grid and the bidirectional converter.
In one embodiment, the positive direction of the current flowing from the power distribution network to the alternating current-direct current microgrid is used, and the anti-backflow protection triggering condition comprises the following steps: and the power of the grid-connected point is less than or equal to a first anti-backflow protection threshold value, wherein the first anti-backflow protection threshold value is greater than or equal to 0.
In one embodiment, the anti-reflux protection triggering condition further includes: and the duration of the power of the grid-connected point being less than or equal to the first anti-reflux protection threshold value is longer than the preset anti-reflux protection duration.
In one embodiment, after the controlling disconnects the ac microgrid from the bidirectional converter, the method further comprises:
and adjusting the power of the bidirectional converter to a preset power value, wherein under the preset power value, after the alternating current microgrid is connected with the bidirectional converter, the power of a grid-connected point is greater than a first anti-reflux protection threshold value.
In one embodiment, after the controlling disconnects the ac microgrid from the bidirectional converter, the method further comprises:
if the power of the grid-connected point meets the preset anti-reflux protection stopping condition, controlling to recover 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 greater than or equal to a second anti-backflow protection threshold value, wherein the second anti-backflow protection threshold value is greater than the first anti-backflow protection threshold value.
In one embodiment, the method further comprises:
and if the alternating-current microgrid is electrically connected with the bidirectional converter and the power of the grid-connected point is greater than the first anti-reflux protection threshold and less than the second anti-reflux protection threshold, adjusting the power of the bidirectional converter according to the second anti-reflux protection threshold and the power of the grid-connected point.
In one embodiment, the method further comprises:
and if the power of the grid-connected point does not meet the countercurrent-prevention 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 microgrid includes an ac load electrically connected to a grid connection point, the dc microgrid includes a power generation system, an energy storage system and a dc load electrically connected to the bidirectional converter, respectively, and the ac/dc microgrid is controlled to operate according to a predetermined energy storage and power generation plan, including:
according to the energy storage power generation plan, if the current time 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, the output power of the power generation system is gradually adjusted according to a first 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 energy storage system is charged according to the planned charging power in the energy storage power generation plan;
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, 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 the energy storage power generation plan, if the current time is in the energy storage discharge time interval and the electric quantity of the energy storage system is larger than a second preset electric quantity threshold value, the output power of the power generation system is adjusted step by step according to a second preset step length until the maximum power generation power is reached, and the power of the bidirectional converter is adjusted step by step according to a third preset step length according to the output power of the power generation system and the power of the direct current load, so that the energy storage system discharges according to the planned discharge power in the energy storage power generation plan;
and if the current moment is in the energy storage and discharge time interval and the electric quantity of the energy storage system is less than or equal to 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 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.
In one embodiment, the method further comprises:
according to the energy storage and power generation plan, if the current time is in the energy storage standing time period and the electric quantity of the energy storage system is smaller than a first preset electric quantity threshold value, the output power of the power generation system is gradually adjusted according to a first preset step length until the maximum power generation power is reached, and the power of the bidirectional converter is adjusted to be equal to the opposite number of the power of the alternating current load;
if the current time is in the energy storage standing time 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.
In a second aspect, an embodiment of the present application provides an ac/dc microgrid control device, is applied to an ac/dc microgrid, and the ac/dc microgrid includes an ac microgrid, a dc microgrid and a bidirectional converter, wherein the ac microgrid accesses a power distribution network through a grid-connected point, the bidirectional converter is electrically connected between the ac microgrid and the dc microgrid, and the ac/dc microgrid control device includes:
the detection module is used for detecting the power of a grid-connected point in real time;
and the protection module is used for controlling to disconnect the electric connection between the alternating current microgrid and the bidirectional converter if the power of the grid-connected point meets a preset anti-reflux protection triggering condition.
In a third aspect, an embodiment of the present application provides an ac/dc microgrid control device, including: the controller may further comprise a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the ac/dc microgrid control method according to any one of the first aspect when executing the computer program.
According to the alternating current-direct current microgrid control method and device, when the power of a grid-connected point meets the preset countercurrent-prevention protection triggering condition, the alternating current microgrid 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 commissioning cost is reduced. Moreover, 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 continues to supply power to the alternating-current load through the power distribution network. In addition, for the power distribution network, when reverse power protection is prevented, the alternating current load continues to get power, sudden unloading of the power distribution network cannot occur, too large 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 in the embodiments of the present application, the drawings needed to be used in the embodiments or the prior art descriptions will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present application, and it is obvious for those skilled in the art to obtain other drawings based on these drawings without inventive exercise.
Fig. 1 is a schematic structural diagram of an ac/dc microgrid provided in an embodiment of the present application;
fig. 2 is a schematic flowchart of a method for controlling an ac/dc microgrid according to an embodiment of the present application;
fig. 3 is a schematic diagram of a power regulation bidirectional converter according to a second anti-reflux protection threshold and a grid-connected point according to an embodiment of the present application;
fig. 4 is a schematic flowchart of an energy storage charging period ac/dc microgrid control method according to an embodiment of the present application;
fig. 5 is a schematic flowchart of an ac/dc microgrid control method in an energy storage and discharge period according to an embodiment of the present application;
fig. 6 is a schematic flowchart of an energy storage standing period ac/dc microgrid control method according to an embodiment of the present application;
fig. 7 is a schematic structural diagram of an ac/dc microgrid control device according to an embodiment of the present application.
Description of reference numerals:
AC/DC microgrid 10
AC microgrid 110
AC load 111
Second sampling device 112
DC microgrid 120
DC bus 121
Power generation system 122
Photovoltaic power generation apparatus 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
Microgrid 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 is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present application and are not intended to limit the present application.
It is to be understood that the terms "first," "second," "third," "fourth," and the like (if any) in the embodiments of the present application are used for distinguishing between similar elements and not necessarily for describing a particular sequential or chronological order.
It is understood that the term "and/or" as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.
In the conventional technology, the countercurrent phenomenon of an AC/DC micro-grid is mainly prevented by the following two ways:
the first is to arrange a reverse power protector between an AC/DC micro-grid and a grid-connected point. This approach, while capable of preventing backflow, is costly in terms of system cost.
And the second method 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 the anti-reflux protection threshold, the micro-grid is controlled to be switched into an island mode, otherwise, the micro-grid is controlled to work in a 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, and frequent sudden loading and sudden unloading of the power distribution network generate large impact on the power distribution network.
The alternating current-direct current microgrid control method and device provided by the embodiment of the application aim to solve the problems.
The technical solution in the present application will be described in detail below with reference to the accompanying drawings. It should be noted that, in the present application, different technical features may be combined with each other without conflict.
The alternating current-direct current microgrid control method provided by the embodiment of the application can be applied to an alternating current-direct current microgrid shown in fig. 1, and is used for controlling the alternating current-direct current microgrid, preventing countercurrent (namely, reverse power) and realizing grid connection and no internet surfing. 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 power distribution network 20 through a point-of-grid PCC, and bidirectional converter 130 is electrically connected between ac microgrid 110 and dc microgrid 120. Herein, the point-of-connection PCC is also referred to as a point of common connection, etc.
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 PCC. The distribution network 20 is connected to the step-down transformer 201 via a high-voltage ac bus 203. The distribution network 20 outputs 10kV or 35kV high-voltage alternating current through the high-voltage alternating current bus 203, and the step-down transformer 201 steps down the high-voltage alternating current output by the distribution network 20 to 400V alternating current, and outputs the high-voltage alternating current through the low-voltage alternating current bus 204. The first sampling device 202 and the breaker QF1 are connected in series on the low voltage ac bus 204 between the step-down transformer 201 and the point-of-connection PCC. The first sampling device 202 is used for collecting signals such as voltage, current or power on a low-voltage alternating current 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 mcu 140 through a measurement signal line, and transmit the acquired measurement signal to the mcu 140. The breaker QF1 is used for controlling the on-off between the step-down transformer 201 and the grid-connected point PCC. The circuit breaker QF1 may be connected to the microgrid control device 140 via a switching signal line, and the circuit breaker QF1 may be controlled by the microgrid control device 140, and may receive the switching signal sent by the microgrid control device 140 to implement switching on and off.
Ac microgrid 110 may include an ac load 111 electrically connected to a low voltage ac bus 204. Optionally, the ac microgrid 110 may also include a second sampling device 112 and a breaker QF 2. The second sampling device 112 and the breaker QF2 are connected between the ac load 111 and the low voltage ac busbar 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 mcu 140 through a measurement signal line, and transmit the collected measurement signal to the mcu 140. The breaker QF2 is used for controlling the on-off between the low-voltage ac busbar 204 and the ac load 111. The circuit breaker QF2 may be connected to the microgrid control device 140 via a switching signal line, and the circuit breaker QF2 may be controlled by the microgrid control device 140, and may receive the switching signal sent by the microgrid control device 140 to implement switching on and off.
The bidirectional converter 130 may be an AC/DC converter, and is a device for converting voltage between an AC bus and a DC bus, and is capable of realizing bidirectional flow of AC and DC energy. That is, the bidirectional converter 130 may convert the ac power on the low-voltage ac BUS 204 into 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 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 may be connected to the microgrid control device 140 through a communication signal line, so as to realize interaction of communication signals with the microgrid control device 140.
Illustratively, a breaker QF3 may be disposed between the ac microgrid 110 and the bidirectional converter 130. Specifically, the breaker QF3 is disposed between the low voltage ac bus 204 and the bidirectional converter 130 in the ac microgrid 110. The breaker QF3 is used for controlling the on-off between the low-voltage ac bus 204 and the bidirectional converter 130. The circuit breaker QF3 may be connected to the microgrid control device 140 via a switching signal line, and the circuit breaker QF3 may be controlled by the microgrid control device 140, and may receive the switching signal sent by the microgrid control device 140 to implement switching on and off.
Optionally, dc microgrid 120 may include a power generation system 122, an energy storage system 123, and a dc load 124 electrically connected to 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 takes the power generation system 122 as a photovoltaic power generation system as an example for explanation. The power generation system 122 may include a Photovoltaic (PV) device 1221 and a photovoltaic DC/DC 1222 coupled to the PV device 1221. The photovoltaic DC/DC 1222 is a conversion device for voltage between the DC 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 DC bus 121. Photovoltaic DC/DC 1222 operates in Maximum Power Point Tracking (MPPT) mode. Photovoltaic DC/DC 1222 may be connected to microgrid control device 140 via a communication signal line, and the maximum output power of photovoltaic DC/DC 1222 is regulated and controlled by microgrid control device 140. The Energy Storage System 123 may include an Energy Storage System (ESS) device 1231 and an Energy Storage DC/DC 1232 connected to the Energy Storage device 1231. The energy storage DC/DC 1232 may be connected to the microgrid control device 140 through a communication signal line. The energy storage DC/DC 1232 is a conversion device of voltage between the DC bus 121 and the energy storage device 1231, and can realize bidirectional flow of energy between the energy storage device 1231 and the DC bus 121. The energy storage DC/DC 1232 works in a direct current bus voltage stabilizing mode.
Optionally, a third sampling device 1223 and a breaker QF4 may be disposed between the photovoltaic DC/DC 1222 and the DC bus 121. The third sampling device 1223 is used for collecting signals such as voltage, current or power on a line between the photovoltaic DC/DC 1222 and the DC bus 121. The third sampling device 1223 may be in signal connection with the mcu 140 through a measurement signal line, and transmit the acquired measurement signal to the mcu 140. The breaker QF4 is used for controlling the connection and disconnection between the photovoltaic DC/DC 1222 and the direct current bus 121. The circuit breaker QF4 may be connected to the microgrid control device 140 via a switching signal line, and the circuit breaker QF4 may be controlled by the microgrid control device 140, and may receive the switching signal sent by the microgrid control device 140 to implement switching on and off.
Optionally, a fourth sampling device 1233 and a breaker QF5 may be disposed between the energy storage DC/DC 1232 and the DC bus 121. The fourth sampling device 1233 is used for collecting signals such as voltage, current or power on a line between the energy storage DC/DC 1232 and the DC bus 121. The fourth sampling device 1233 may be in signal connection with the mcu 140 through a measurement signal line, and transmit the acquired measurement signal to the mcu 140. The breaker QF5 is used for controlling the on-off between the energy storage DC/DC 1232 and the direct current bus 121. The circuit breaker QF5 may be connected to the microgrid control device 140 via a switching signal line, and the circuit breaker QF5 may be controlled by the microgrid control device 140, and may receive the switching signal sent by the microgrid control device 140 to implement switching on and off.
Optionally, a fifth sampling device 1241 and a breaker QF6 may be disposed between the dc load 124 and the dc bus 121. The fifth sampling device 1241 is configured to collect signals such as voltage, current, or power on a line between the dc load 124 and the dc bus 121. The fifth sampling device 1241 may be in signal connection with the microgrid control device 140 through a measurement signal line, and transmit the acquired measurement signal to the microgrid control device 140. The breaker QF6 is used for controlling the on/off between the dc load 124 and the dc bus 121. The circuit breaker QF6 may be connected to the microgrid control device 140 via a switching signal line, and the circuit breaker QF6 may be controlled by the microgrid control device 140, and may receive the switching signal sent by the microgrid control device 140 to implement switching on and off.
The microgrid control means 140 is the "brain" of the ac/dc microgrid 10. The microgrid control device 140 collects data such as voltage, current or power at 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 performs remote control, remote regulation, remote signaling and the like on the bidirectional converter 130, the power generation system 122 and the energy storage system 123 according to the data. Meanwhile, the microgrid control device 140 controls the opening or closing of the breaker QF1, the breaker QF2, the breaker QF3, the breaker QF4, the breaker QF5, or the breaker QF6 according to these data.
It should be noted that, in the embodiment of the present application, structures of each module, device, component, and the like in the ac/dc microgrid 10 are not limited at all, and may be selected according to actual requirements. The microgrid control device 140 may be a computer device, an upper computer, a Programmable Logic Controller (PLC), a microprocessor, or the like. The piconet 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 microgrid control method provided by the present application. The embodiment of the present application is described by taking the method as an example applied to the piconet controlling device 140 in fig. 1. As shown in fig. 2, the ac/dc microgrid control method provided in this embodiment may include:
s201, detecting power P of grid-connected point in real timepcc。
Optionally, the first sampling device may collect current and voltage of the sampling point, and the microgrid control device calculates power P of the grid-connected point according to the current and voltage of the sampling pointpcc。
S202, if the power P of the grid-connected pointpccAnd if the preset anti-reflux 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-reflux protection triggering condition refers to a preset condition for triggering anti-reflux protection. Optionally, the critical state where the reverse power occurs may be determined as the anti-reflux protection triggering condition, or a certain safety value may be reserved on the basis of the critical state of the reverse power to determine the anti-reflux protection triggering condition.
Power P when point of connectionpccIf the preset anti-reflux protection triggering condition is not met, the AC/DC micro-grid is considered to have no reverse power at the current moment, the anti-reflux protection is not needed, and the AC/DC micro-grid works in a grid-connected state.
Power P when point of connectionpccAnd if the preset anti-reflux protection triggering condition is met, the AC/DC micro-grid is considered to have the risk of reverse power at the current moment. The microgrid control device controls the circuit breaker QF3 to be disconnected, so that the alternating current microgrid and the bidirectional converter are disconnected electrically. At the moment, the direct current microgrid is disconnected with the alternating current microgrid, the direct current microgrid cannot output power to a grid-connected point any more, and the grid-connected point power cannot generate reverse power, so that the phenomenon of surfing the Internet cannot occur, and the occurrence of the reverse current phenomenon is prevented.
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 provide energy required by a direct current load together, so that normal power supply can be performed on the direct current load. On the other hand, after the direct-current microgrid is disconnected from the alternating-current microgrid, the direct-current microgrid can keep self balance. Specifically, when the direct current load increases, the microgrid control device controls the output power of the power generation system, and the power on the direct current bus is supplemented through the energy storage system. When the output of the power generation system is larger than the demand of the direct current load, the energy storage system absorbs the redundant power generation power. When the dc load is reduced or suddenly unloaded, the short term imbalance that occurs within the dc microgrid may be supplemented by an energy storage system.
The direct current micro-grid is disconnected with the alternating current micro-grid, the alternating current micro-grid is still connected with a grid-connected point, and power is continuously supplied to an alternating current load through a power distribution network, so that the alternating current load can keep working normally. For the power distribution network, the alternating current load continues to get power, the power distribution network is not unloaded, and overlarge impact on the power distribution network cannot be caused.
It should be noted that, in the conventional technology, when the power of the grid-connected point triggers the reverse-flow prevention protection threshold, the circuit breaker at the grid-connected point, that is, the circuit breaker QF, is disconnected1, switching the micro-grid into an island mode, wherein the power supply of the alternating-current micro-grid cannot be guaranteed. And the breaker QF1 is disconnected, and the power distribution network is suddenly unloaded, so that large impact is caused to the power distribution network. In the method for controlling an ac/dc microgrid provided in this embodiment, the power P at a grid-connected pointpccWhen the preset anti-reflux 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 microgrid can normally supply power to the direct current load through an internal energy storage system and a power generation system, and the alternating current microgrid continuously supplies power to the alternating current load through a power distribution network. In addition, for the power distribution network, when the power distribution network is subjected to anti-reflux protection, alternating current loads continue to get power, sudden unloading of the power distribution network cannot occur, too large impact on the power distribution network cannot be caused, and the stability of the power distribution network is improved.
The anti-reflux protection triggering condition may be a preset power threshold. It can be understood that when the positive direction of the setting is different, the triggering conditions of the anti-reflux protection are different. The following embodiment describes a specific method for controlling the anti-backflow protection triggering condition and the dc microgrid with the direction in which current flows from the distribution network to the ac/dc microgrid in fig. 1 (i.e., the direction indicated by the arrow in fig. 1) as the positive direction.
In one embodiment, the positive direction of the current flowing from the power distribution network to the ac/dc microgrid is the positive direction, and the anti-backflow protection triggering condition may include: power P of grid-connected pointpccLess than or equal to the first anti-reflux protection threshold P1. First anti-reflux protection threshold P1Is a preset fixed power value and has a 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 method for judging whether to trigger the anti-countercurrent protection is simple and reliable through the anti-countercurrent protection threshold value, and the anti-countercurrent protection efficiency can be improved.
Further, in one embodiment, theThe upstream protection triggering conditions may further include: power P of grid-connected pointpccLess than or equal to the first anti-reflux protection threshold P1The duration of (a) is longer than the preset anti-reflux protection duration. That is, when the power of the grid-connected point is less than or equal to the first anti-reflux protection threshold P1And if the duration time is longer than the anti-reflux protection duration time, triggering the anti-reflux protection action to control and disconnect the electric connection between the alternating current microgrid and the bidirectional converter. The duration of the anti-backflow protection can be set according to actual conditions, and can be 5s, 10s or 20s and the like. In the embodiment, the power P of the grid-connected point caused by the abnormity of the microgrid can be effectively prevented by setting the duration factor in the anti-reflux protection triggering conditionpccThe conditions such as occasional fluctuation and the like are misjudged as reverse flow, and the reverse flow prevention protection is mistriggered, so that the accuracy and the safety of the reverse flow 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 under the preset power value, after the alternating current micro-grid is connected with the bidirectional converter, the power P of a grid-connected pointpccGreater than a first anti-reflux protection threshold P1. Optionally, the preset power value may be 0. Therefore, when the breaker QF3 is closed again, and the alternating current microgrid is electrically reconnected with the bidirectional converter, the direct current microgrid does not output negative power to a grid-connected point and does not consume power output by the grid-connected point. Power P of grid-connected pointpccThe power of the ac load is subtracted from the power output by the distribution network. Therefore, the phenomenon of reverse flow can be avoided after the alternating current micro-grid is electrically reconnected with the bidirectional converter, and the safety of the power distribution network is ensured. 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 the fluctuation of other loads, so that the power mutation of a grid-connected point 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 power P of grid-connected pointpccIf the preset anti-reflux protection stopping condition is met, the AC micro-grid and the bidirectional micro-grid are controlled to be recoveredAnd (4) electric connection of the current transformer.
Specifically, after the breaker QF3 is turned off, the bidirectional converter no longer consumes the power of the grid-connected point, and no longer transmits the power in the negative direction to the grid-connected point, so the power P of the grid-connected pointpccIt will gradually recover. Power P when point of connectionpccAnd when the preset anti-reflux protection stopping condition is met, the microgrid control device controls the circuit breaker QF3 to be closed, and the electric connection between the alternating current microgrid and the bidirectional converter is recovered, so that the timely grid connection is ensured when the grid connection condition is met, and the stability and reliability of the alternating current/direct current microgrid are further improved.
Optionally, the anti-backflow protection stopping condition may correspond to the anti-backflow protection triggering condition, and may be, for example: power P of grid-connected pointpccGreater than a first anti-reflux protection threshold P1. Optionally, the backflow prevention protection stopping condition may also be: power P of grid-connected pointpccGreater than or equal to the second anti-reflux protection threshold P2Wherein the second anti-reverse-flow protection threshold value P2Greater than a first anti-reflux protection threshold P1. In other words, the anti-reflux protection stop conditions are: at a first anti-reflux protection threshold P1On the basis of the above-mentioned safety value, a certain safety range (i.e. second anti-reflux protection threshold value P) is set2With a first protection threshold against reverse flow P1The difference) of the alternating current and direct current micro-grid, so that the risk of generating reverse power after the alternating current and direct current micro-grid is restored to be connected with the grid again can be reduced, and the stability of the alternating current and direct current micro-grid is further improved.
In one embodiment, when the ac microgrid is electrically connected to the bidirectional converter, i.e. when the ac/dc microgrid is in a grid-connected state, if the power P of the grid-connected point is PpccIf the preset anti-reflux protection boundary condition is met, the power P of the grid-connected point is determined according to the anti-reflux protection boundary conditionpccRegulating power P of bidirectional converterACDC. The anti-reflux protection boundary condition is used for limiting and screening the condition that the anti-reflux protection triggering condition is not triggered, but the condition that the anti-reflux protection stopping condition is not met. That is, the reverse-flow prevention protection boundary condition is a condition between the reverse-flow prevention protection triggering condition and the reverse-flow prevention protection stopping condition. In a specific embodimentThe countercurrent-preventing boundary conditions are as follows: power P of grid-connected pointpccGreater than a first anti-reflux protection threshold P1And is less than the second anti-reflux protection threshold P2。
Due to PPCC＝PAC_Load+PACDCAnd the bidirectional converter is used as a controlled power source, and the power P of the grid-connected pointpccWhen the boundary condition of the anti-countercurrent protection is met, according to a second anti-countercurrent protection threshold value P2And power P of point of grid connectionPCCRegulating power P of bidirectional converterACDC. By regulating the power P of a bidirectional converterACDCThen the power P of the grid-connected point can be quickly adjustedpccEnsuring power P of grid-connected pointpccThe stability of (3) greatly reduces the risk of reverse power of the alternating current-direct current micro-grid.
In particular, FIG. 3 illustrates an embodiment based on a second protection threshold against reverse flow P2And power P of point of grid connectionpccRegulating power P of bidirectional converterACDCSchematic diagram of the principle of (1). As shown in fig. 3, the second anti-reverse flow protection threshold P2Given, the power P of the point of connection at the current timePCCAs feedback, the two are differentiated to perform PI (proportional plus integral) regulation, and then PI regulation output is limited, PACDC_SetPower P as a bidirectional converterACDCThe set value of (2). Through PI regulation, the power P of a grid-connected point can be realized in the first aspectpccRapid adjustment of (2). In the second aspect, the power of the bidirectional converter is equal to the power P of the DC loadPVPower P of energy storage systemESSAnd the output power P of the power generation systemPVSum, i.e. PACDC＝PDC_Load+PESS+PPVRegulating the output power P of the bidirectional converterACDCAnd the direct-current micro-grid can realize power self-balance without influencing the generated output of the power generation system. Compared with the mode that the power of the energy storage system and the power generation system is adjusted through the independent converters in the traditional technology, the method provided by the embodiment does not need to give consideration to the adjustment of the power of the energy storage system and the power generation system, can simply and quickly realize the power adjustment of the grid-connected point, can not be influenced by the power generation output, and fully exerts the function of the energy storage system as the power of the power generation systemThe advantage of a voltage source.
It can be understood that the power P of the point of connectionpccGreater than or equal to the second anti-reflux protection threshold P2When the adjustment mode is not selected, the adjustment mode is exited; power P when point of connectionpccLess than or equal to the first anti-reflux protection threshold P1Then, the adjustment mode is exited and step S202 is repeated.
The ac/dc microgrid control method provided by the embodiment of the application further includes a process of controlling the operation of the ac/dc microgrid according to an energy storage and power generation plan, which is described in detail below with reference to the embodiment.
In one embodiment, the method further comprises:
if power P of grid-connected pointpccAnd if the preset countercurrent-prevention protection triggering condition is not met, controlling the AC/DC micro-grid to operate according to a preset energy storage power generation plan.
In particular, the power P at the point of grid connectionpccGreater than a second anti-reflux protection threshold P2Namely: 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 and power generation plan can be made in advance according to the set peak valley-leveling time period, the electricity price and other source charge 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 time period, an energy storage discharging time period and an energy storage standing time period. The ac/dc microgrid control in each time interval is further described below with reference to the accompanying drawings:
1) energy storage charging period
Fig. 4 is a schematic flowchart of a method for controlling an ac/dc microgrid during an energy storage and charging period according to an embodiment of the present application. As shown in fig. 4, the step of controlling the ac/dc microgrid to operate according to a preset energy storage and power generation plan may include:
and according to the energy storage and power generation plan, if the current time is in the energy storage and charging time interval, executing the step S401.
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 for representing whether the current battery charge is close to the 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 large and close to the 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 less 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 performed.
S402, according to a first preset step length delta PPV1Stepwise adjustment of the output power P of a power generation systemPVUntil reaching the maximum power generation power and according to the output power P of the power generation systemPVAnd power P of DC loadDC_LoadAdjusting the power P of a bidirectional converterACDCSo that the energy storage system can charge according to the planned charging power P in the energy storage and power generation planESS_Plan1And (6) charging.
According to a first preset step length delta PPV1Stepwise adjustment of the output power P of a power generation systemPVCan prevent the output power P of the power generation system until the maximum power generation power is reachedPVAbrupt change of power P resulting in point of connectionpccThe sudden change triggers the anti-reflux protection, so that the stability of the alternating current and direct current micro-grid can be ensured. It should be noted that, for the photovoltaic power generation system, the maximum photovoltaic power limit value may be gradually increased until the maximum power tracking point is reached.
Due to PACDC＝PDC_Load+PESS+PPVAccording to the output power P of the power generation systemPVAnd power P of DC loadDC_LoadAdjusting the power P of the bidirectional converter in real timeACDCSo that P isESS＝PESS_Plan1。
S403, adjusting output power P of power generation systemPVPower P equal to DC loadDC_LoadAnd power P of AC loadAC_LoadSumming and adjusting the power of the bidirectional converter to be equal to the power P of the AC loadAC_LoadThe opposite number of (c).
Namely, 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 microgrid control is performedDevice for regulating output power P of power generation systemPV＝PAC_Load+PDC_Load. For a photovoltaic power generation system, photovoltaic tracking load output can be performed by limiting a photovoltaic maximum power limit. Meanwhile, the micro-grid control device adjusts the power P of the bidirectional converter in real timeACDC＝-PAC_LoadThat is, the bidirectional converter tracks the ac load contribution.
2) Period of energy storage discharge
Fig. 5 is a schematic flowchart of a method for controlling an ac/dc microgrid during an energy storage and discharge period according to an embodiment of the present application. As shown in fig. 5, the step of controlling the ac/dc microgrid to operate according to a preset energy storage and power generation plan may include:
according to the energy storage and power generation plan, if the current time is in the energy storage and discharge time period, executing the step S501;
and S501, judging whether the electric quantity of the energy storage system is larger than a second preset electric quantity threshold, if so, executing S502, and otherwise, executing S503.
And the second preset electric quantity threshold value is used for representing whether the current battery electric quantity is close to emptying. And the electric quantity of the energy storage system is smaller than a second preset electric quantity threshold value, which indicates that the current battery electric quantity is less and approaches to emptying. The electric quantity of the energy storage system is larger than or equal to a second preset electric quantity threshold value, and the situation that the current electric quantity is large and the emptying is not close is shown.
S502, according to a second preset step length delta PPV2Stepwise adjustment of the output power P of a power generation systemPVUntil reaching the maximum power generation power and according to the output power P of the power generation systemPVAnd power P of DC loadDC_LoadAccording to a third preset step length delta PACDCStep-by-step adjustment of the power P of a bidirectional converterACDCSo that the energy storage system discharges power P according to the plan in the energy storage power generation planESS_Plan2And (4) discharging.
According to a second preset step length delta PPV2Stepwise adjustment of the output power P of a power generation systemPVThe specific process and beneficial effects of the maximum generated power are referred to the step S402, which is not described herein again. Wherein the second preset step length Δ PPV2Can be matched with the first preset step length delta PPV1The same or different.
Due to PACDC＝PDC_Load+PESS+PPVAccording to a third preset step length delta PACDCStep-by-step adjustment of the power P of a bidirectional converterACDCThereby being able to reach PESS＝PESS_Plan2. Here, according to a third preset step Δ PACDCStep-by-step adjustment of the power P of a bidirectional converterACDCCan prevent the power P of the energy storage systemESSSudden or too fast a change results in a grid-connected point power PPCCSudden change triggers reverse power protection, so that the stability of the alternating current-direct current microgrid can be ensured.
S503, according to a second preset step length delta PPV2Stepwise adjustment of the output power P of a power generation systemPVUntil reaching the maximum power generation power and according to the output power P of the power generation systemPVAnd power P of DC loadDC_LoadAdjusting the power P of a bidirectional converterACDCSo that the discharge power of the energy storage system is 0.
In this step, the output power P of the power generation system is adjustedPVThe principle, advantageous effects, etc. are similar to those of step S502 except that the power P of the bidirectional converter is adjusted in step S502ACDCIs aimed at making PESS＝PESS_Plan2In this step, the power P of the bidirectional converter is adjustedACDCIs aimed at making PESS＝0。
3) Energy storage standing period
Fig. 6 is a schematic flowchart of a method for controlling an ac/dc microgrid during an energy storage standing period according to an embodiment of the present application. As shown in fig. 6, the step of controlling the ac/dc microgrid to operate according to a preset energy storage and power generation plan may include:
and according to the energy storage and power generation plan, if the current time is in the energy storage standing time period, executing the step S601.
S601, judging that the electric quantity of the energy storage system is smaller than a first preset electric quantity threshold, if the electric quantity of the energy storage system is smaller than the first preset electric quantity threshold, executing a step S602, otherwise, executing a step S603.
The step S401 is not repeated herein.
S602, according to a first preset step length delta PPV1Stepwise adjustment of the output power P of a power generation systemPVUntil the maximum power generation power is reached, and adjusting the power P of the bidirectional converterACDCPower P equal to AC loadAC_LoadThe opposite number of (c).
According to a first preset step length delta PPV1Stepwise adjustment of the output power P of a power generation systemPVThe specific process and beneficial effects until the maximum generated power is reached refer to step S402, which is not described herein again.
Adjusting PACDCSo that P isACDC_Set＝-PAC_LoadNamely, the bidirectional converter tracks the AC load output.
S603, adjusting output power P of power generation systemPVPower P equal to DC loadDC_LoadAnd power P of AC loadAC_LoadAnd adjusting the power of the bidirectional converter to be equal to the power of the alternating current load.
The process and beneficial effects of this step are equivalent to step S403, and are not described herein again.
In the embodiment, the alternating current-direct current micro-grid is controlled to operate according to the preset energy storage power generation plan, so that the 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 utilization value of the alternating current-direct current micro-grid can be improved through peak clipping and valley filling.
It should be understood that although the various steps in the flowcharts of fig. 2, 4-6 are shown in order as indicated by the arrows, the steps are not necessarily performed in order as indicated by the arrows. The steps are not performed in the exact order shown and described, and may be performed in other orders, unless explicitly stated otherwise. Moreover, at least some of the steps in fig. 2 and 4-6 may include multiple sub-steps or multiple stages that are not necessarily performed at the same time, but may be performed at different times, and the order of performing the sub-steps or stages is not necessarily sequential, but may be performed in turn or alternately with other steps or at least some of the sub-steps or stages of other steps.
Fig. 7 shows a block diagram of a structure of an ac/dc microgrid control device according to an embodiment of the present application. As shown in fig. 7, the ac/dc microgrid control apparatus provided in this embodiment may include:
a detection module 701, configured to detect power of a grid-connected point in real time;
and the protection module 702 is configured to control to disconnect the electrical connection between the ac microgrid and the bidirectional converter if the power of the grid-connected point meets a preset reverse-flow-prevention protection trigger 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 the power of a grid-connected point is greater than the first anti-reflux protection threshold after the ac microgrid is connected to the bidirectional converter at the preset power value.
In an embodiment, the ac/dc microgrid control apparatus further includes a recovery module 703 for controlling to recover the electrical connection between the ac microgrid 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 condition includes: and the power of the grid-connected point is greater than or equal to a second anti-backflow protection threshold value, wherein the second anti-backflow protection threshold value is greater than the first anti-backflow protection threshold value.
In an embodiment, the ac/dc microgrid control apparatus further includes a control module 704, configured to adjust the power of the bidirectional converter according to the second anti-reflux protection threshold and the power of the grid-connected point if the ac microgrid is electrically connected to the bidirectional converter and the power of the grid-connected point is greater than the first anti-reflux protection threshold and less than the second anti-reflux protection threshold.
In an embodiment, the ac/dc microgrid control apparatus further includes an energy storage plan module 705, configured to control the ac/dc microgrid to operate according to a preset energy storage power generation plan if the power of the grid-connected point does not meet the countercurrent protection trigger condition.
In one embodiment, the energy storage plan module 705 is specifically configured to, according to the energy storage power generation plan, if the current time is in the 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 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, 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 the energy storage power generation plan, if the current time is in the energy storage discharge period and the electric quantity of the energy storage system is greater than a second preset electric quantity threshold, gradually 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 gradually 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; and if the current moment is in the energy storage and discharge time interval and the electric quantity of the energy storage system is less than or equal to 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 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.
In one embodiment, the energy storage plan module 705 is specifically configured to, according to the energy storage power generation plan, if the current time is in the energy storage standing time 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 to be equal to the opposite number of the power of the ac load; if the current time is in the energy storage standing time 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.
The ac/dc microgrid control apparatus provided in this embodiment is used to execute the ac/dc microgrid control method provided in the embodiment of the method of the present application, and the technical principle and the technical effect are similar to each other.
It will be apparent to those skilled in the art that, for convenience and brevity of description, only the above-mentioned division of the functional units and modules is illustrated, and in practical applications, the above-mentioned functions may be distributed as different functional units and modules according to needs, that is, the internal structure of the apparatus may be divided into different functional units or modules to implement all or part of the above-mentioned functions. Each functional unit and module in the embodiments may be integrated in one processing unit, or each unit may exist alone physically, or two or more units are integrated in one unit, and the integrated unit may be implemented in a form of hardware, or in a form of 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 processes of the units and modules in the system may refer to the corresponding processes in the foregoing method embodiments, and are not described herein again.
The embodiment of the present application further provides a little electric network control device of alternating current-direct current, and this little electric network control device of alternating current-direct current includes: 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 above-described method embodiments when executing the computer program.
It should be clear that the processes, principles, advantages and the like of the computer program executed by the processor in the embodiments of the present application are consistent with the execution of the steps in the method described above, and specific reference may be made to the description above.
Embodiments of the present application further provide a computer-readable storage medium, which stores a computer program, and when the computer program is executed by a processor, the computer program can implement the steps in any of the above method embodiments.
It should be clear that the processes, principles, advantages and the like of the computer program executed by the processor in the embodiments of the present application are consistent with the execution of the steps in the method described above, and specific reference may be made to the description above.
It will be appreciated by those of ordinary skill in the art that any reference to memory, storage, databases, or other media used in the embodiments provided herein may include non-volatile and/or volatile memory. Non-volatile 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), Rambus Direct RAM (RDRAM), direct bus dynamic RAM (DRDRAM), and memory bus dynamic RAM (RDRAM).
The technical features of the above embodiments can be arbitrarily combined, and for the sake of brevity, all possible combinations of the technical features in the above embodiments are not described, but should be considered as the scope of the present specification as long as there is no contradiction between the combinations of the technical features.
The above-mentioned embodiments are only used for illustrating the technical solutions of the present application, and not for limiting the same; 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 solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; such modifications and substitutions do not substantially depart from the spirit and scope of the embodiments of the present application and are intended to be included within the scope of the present application.

Claims (12)

1. An AC/DC microgrid control method is characterized by being applied to an AC/DC microgrid, wherein the AC/DC microgrid comprises an AC microgrid, a DC microgrid and a bidirectional converter, the AC microgrid is connected to a power distribution network through a grid-connected point, and the bidirectional converter is electrically connected between the AC microgrid and the DC microgrid, 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-reflux protection triggering condition, controlling to disconnect the electric connection between the alternating current microgrid and the bidirectional converter.
2. The method of claim 1, wherein the anti-backflow protection triggering condition is based on a positive direction of current flow from the power distribution network to the AC/DC microgrid, and comprises: and the power of the grid-connected point is less than or equal to a first anti-backflow protection threshold value, wherein the first anti-backflow protection threshold value is greater than or equal to 0.
3. The method of claim 2, wherein the anti-reflux protection triggering condition further comprises: and the duration of the power of the grid-connected point being less than or equal to the first anti-reflux protection threshold is longer than the preset anti-reflux protection duration.
4. The method of claim 2, wherein after the controlling electrically disconnects the ac microgrid from the bidirectional converter, the method further comprises:
and adjusting the power of the bidirectional converter to a preset power value, wherein under the preset power value, after the alternating current microgrid is connected with the bidirectional converter, the power of the grid-connected point is greater than the first anti-reflux protection threshold value.
5. The method of any of claims 2 to 4, wherein after said controlling electrically disconnects said AC microgrid from said bidirectional converter, said method further comprises:
if the power of the grid-connected point meets a preset anti-reflux protection stopping condition, controlling to recover 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 greater than or equal to a second anti-backflow protection threshold value, wherein the second anti-backflow protection threshold value is greater than the first anti-backflow protection threshold value.
6. The method of claim 5, further comprising:
if the alternating current microgrid is electrically connected with the bidirectional converter and the power of the grid-connected point is greater than the first anti-reflux protection threshold and smaller than the second anti-reflux protection threshold, the power of the bidirectional converter is adjusted according to the second anti-reflux protection threshold and the power of the grid-connected point.
7. The method of any of claims 1-4, 6, further comprising:
and if the power of the grid-connected point does not meet the countercurrent-prevention protection triggering condition, controlling the alternating current-direct current micro-grid to operate according to a preset energy storage power generation plan.
8. The method of claim 7, wherein the AC microgrid comprises an AC load electrically connected with the grid-connected point, the DC microgrid comprises a power generation system, an energy storage system and a DC load respectively electrically connected with the bidirectional converter, and the controlling the AC/DC microgrid to operate according to a pre-established energy storage and power generation plan comprises:
according to the energy storage power generation plan, if the current time 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 that the energy storage system is charged according to the planned charging power in the energy storage power generation plan;
if the current time is in an 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, 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.
9. The method of claim 8, further comprising:
according to the energy storage power generation plan, if the current time is in an energy storage discharge time 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 the 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;
and if the current moment is in an energy storage and discharge period and the electric quantity of the energy storage system is less 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.
10. The method of claim 8, further comprising:
according to the energy storage and power generation plan, if the current moment is in an energy storage standing time period and the electric quantity of the energy storage system is smaller than the first preset electric quantity threshold value, the output power of the power generation system is gradually adjusted according to the first preset step length until the maximum power generation power is reached, and the power of the bidirectional converter is adjusted to be equal to the opposite number of the power of the alternating current load;
if the current time is in an energy storage standing time period and the electric quantity of the energy storage system is greater 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.
11. The utility model provides a little electric wire netting controlling means of alternating current-direct current, its characterized in that is applied to the little electric wire netting of alternating current-direct current, the little electric wire netting of alternating current-direct current includes exchanging little electric wire netting, direct current little electric wire netting and bidirectional converter, wherein, exchange little electric wire netting passes through the point of being connected in the power distribution network, bidirectional converter electricity is connected in exchange little electric wire netting with between the little electric wire netting of direct current, little electric wire netting controlling means of alternating current-direct current 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 a preset anti-reflux protection triggering condition.
12. A dc-ac microgrid control apparatus comprising a memory, a processor and a computer program stored in said memory and executable on said processor, said processor implementing the method according to any one of claims 1 to 10 when executing said computer program.
CN202110303508.9A 2021-03-22 2021-03-22 AC/DC micro-grid control method and device Active CN113036804B (en)

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