CN116896114B

CN116896114B - Control method based on grid-connected system and grid-connected system

Info

Publication number: CN116896114B
Application number: CN202311162298.1A
Authority: CN
Inventors: 胡文浩; 陈健聪; 姜亲宜
Original assignee: Shenzhen Sofarsolar Co Ltd
Current assignee: Shenzhen Sofarsolar Co Ltd
Priority date: 2023-09-11
Filing date: 2023-09-11
Publication date: 2024-02-06
Anticipated expiration: 2043-09-11
Also published as: CN116896114A

Abstract

The application discloses a control method based on a grid-connected system and the grid-connected system. The grid-connected system comprises a photovoltaic inverter, a light storage inverter, a first load and a second load, wherein the photovoltaic inverter is respectively connected with the light storage inverter, the first load and a power grid to a first node, the second load is connected with the power grid to a second node, and the control method based on the grid-connected system comprises the following steps: acquiring first power of a first node and second power of a second node; calculating the power sum of the first power and the second power; and when the power sum is greater than zero, reducing the output power of the photovoltaic inverter and/or the output power of the optical storage inverter so as to reduce the power sum until the power sum is less than or equal to zero. By the mode, the grid-connected system can be prevented from discharging to the power grid.

Description

Control method based on grid-connected system and grid-connected system

Technical Field

The application relates to the technical field of grid-connected systems, in particular to a control method based on a grid-connected system and the grid-connected system.

Background

The power generated by the photovoltaic system must be used by a local load, and the redundant power is not allowed to be sent into the power grid so as not to influence unstable factors such as harmonic waves introduced into the power grid.

Disclosure of Invention

The application aims to provide a control method based on a grid-connected system and the grid-connected system, which can prevent the grid-connected system from discharging to a power grid.

To achieve the above object, in a first aspect, the present application provides a control method based on a grid-connected system, where the grid-connected system includes a photovoltaic inverter, a light storage inverter, a first load and a second load, the photovoltaic inverter is connected to a first node with the light storage inverter, the first load and a power grid, and the second load is connected to a second node with the power grid, and the method includes:

acquiring first power of the first node and second power of the second node;

calculating a power sum of the first power and the second power;

and when the power sum is greater than zero, reducing the output power of the photovoltaic inverter and/or the output power of the light storage inverter so as to reduce the power sum until the power sum is less than or equal to zero.

In an alternative, the method further comprises:

and if the power sum is smaller than or equal to zero, controlling the full power output of the optical storage inverter.

In an alternative manner, the grid-connected system further comprises a third load and a switch, wherein the switch is connected between the third load and the first node;

said reducing the output power of the photovoltaic inverter and/or the output power of the light storage inverter when the power sum is greater than zero to reduce the power sum until the power sum is less than or equal to zero, comprising:

and when the power sum is greater than zero, reducing the output power of the photovoltaic inverter, and/or the output power of the light storage inverter, and/or closing the switch to reduce the power sum until the power sum is less than or equal to zero.

In an alternative manner, the light storage inverter comprises a photovoltaic converter, an energy storage converter and an inverter, wherein the photovoltaic converter is connected between a photovoltaic panel and the inverter, the energy storage converter is connected between a battery and the inverter, and the inverter is connected to the first node;

said reducing the output power of said photovoltaic inverter and/or the output power of said light storage inverter when said power sum is greater than zero, and/or closing said switch to reduce said power sum until said power sum is less than or equal to zero, comprising:

and when the power sum is greater than zero, adjusting the charge and discharge power of the battery to reduce the power sum until the power sum is less than or equal to zero.

In an optional manner, when the power sum is greater than zero, adjusting the charge and discharge power of the battery to reduce the power sum until the power sum is less than or equal to zero, including:

when the power sum is greater than zero, if the battery is determined to be in a discharging state, reducing the discharging power of the battery to reduce the power sum until the power sum is less than or equal to zero;

and when the discharging power of the battery is reduced to zero, if the power sum is greater than zero, switching the battery to a charging state so as to reduce the power sum until the power sum is less than or equal to zero.

In an alternative manner, the reducing the output power of the photovoltaic inverter and/or the output power of the light storage inverter when the power sum is greater than zero, and/or closing the switch to reduce the power sum until the power sum is less than or equal to zero, further comprises:

and after the battery is switched to be in a charging state, if the charging power of the battery is larger than the rated power of the third load, closing the switch.

In an alternative, the method further comprises:

if the battery is switched to a discharge state, the switch is turned off.

and after the switch is closed, if the charging power of the battery is rated charging power and the sum of the power is larger than zero, reducing the power output by the photovoltaic panel through the photovoltaic converter so as to reduce the sum of the power until the sum of the power is smaller than or equal to zero.

and after the power output by the photovoltaic panel through the photovoltaic converter is reduced, if the power output by the photovoltaic converter is reduced to zero and the power sum is greater than zero, reducing the output power of the photovoltaic inverter to reduce the power sum until the power sum is less than or equal to zero.

In a second aspect, the present application provides a grid-tie system, comprising:

the photovoltaic inverter comprises a light storage inverter, a photovoltaic inverter, a first load and a second load;

the light storage inverter is connected with the photovoltaic inverter, the first load and the power grid respectively and is connected with a first node, and the second load is connected with the power grid;

the light storage inverter includes a controller including:

at least one processor and a memory communicatively coupled to the at least one processor, the memory storing instructions executable by the at least one processor to enable the at least one processor to perform the method as described above.

In an alternative manner, the grid-connected system further includes:

a third load and a switch, the switch being connected between the third load and the first node, and the switch being connected with the controller;

the controller is used for controlling the switch to be closed or opened so as to control the third load to be powered on or powered off.

In an alternative manner, the light storage inverter further comprises a photovoltaic converter, an energy storage converter and an inverter, wherein the photovoltaic converter is connected between a photovoltaic panel and the inverter, the energy storage converter is connected between a battery and the inverter, the inverter is connected to the first node, and the controller is respectively connected with the photovoltaic converter and the energy storage converter;

the controller is used for controlling the photovoltaic converter to control the power output by the photovoltaic panel through the photovoltaic converter, and is used for controlling the energy storage converter to control the charge and discharge power of the battery.

The beneficial effects of this application are: the grid-connected system in the grid-connected system-based control method comprises a photovoltaic inverter, a light storage inverter, a first load and a second load, wherein the photovoltaic inverter is connected with the light storage inverter, the first load and a power grid respectively and is connected with a first node, and the second load is connected with the power grid and is connected with a second node. The method comprises the following steps: acquiring first power of a first node and second power of a second node; calculating the power sum of the first power and the second power; and when the power sum is greater than zero, reducing the output power of the photovoltaic inverter and/or the output power of the optical storage inverter so as to reduce the power sum until the power sum is less than or equal to zero. When the total power is controlled to be equal to zero, no electric quantity transmission process exists between the power grid and the grid-connected system; and when the total power is less than zero, discharging the grid to the grid-connected system. Therefore, the process of discharging the grid-connected system to the power grid does not exist, and the purpose of preventing the grid-connected system from discharging to the power grid is achieved.

Drawings

One or more embodiments are illustrated by way of example and not limitation in the figures of the accompanying drawings, in which like references indicate similar elements, and in which the figures of the drawings are not to be taken in a limiting sense, unless otherwise indicated.

Fig. 1 is a schematic structural diagram of a grid-connected system according to a first embodiment of the present application;

fig. 2 is a schematic structural diagram of a grid-connected system according to a second embodiment of the present application;

fig. 3 is a schematic structural diagram of a controller according to a first embodiment of the present disclosure;

fig. 4 is a flowchart of a control method based on a grid-connected system according to an embodiment of the present application;

FIG. 5 is a schematic diagram of an implementation of step 403 shown in FIG. 4 provided in example one of the present application;

FIG. 6 is a schematic diagram of an implementation of step 501 shown in FIG. 5 provided in one embodiment of the present application;

FIG. 7 is a schematic diagram of an implementation of step 601 shown in FIG. 6 provided in example I of the present application;

FIG. 8 is a schematic diagram of an embodiment of step 501 shown in FIG. 5 provided in example II of the present application;

FIG. 9 is a schematic diagram of controlling the power on or off of a third load according to the first embodiment of the present disclosure;

FIG. 10 is a schematic diagram of an implementation of step 501 shown in FIG. 5 provided in example III of the present application;

FIG. 11 is a schematic diagram of an embodiment of step 501 shown in FIG. 5 provided in example IV of the present application;

fig. 12 is a graph of power in a grid-connected system under different lighting conditions according to an embodiment of the present application.

Detailed Description

For the purposes of making the objects, technical solutions and advantages of the embodiments of the present application more clear, the technical solutions of the embodiments of the present application will be clearly and completely described below with reference to the drawings in the embodiments of the present application, and it is apparent that the described embodiments are some embodiments of the present application, but not all embodiments. All other embodiments, which can be made by one of ordinary skill in the art without undue burden from the present disclosure, are within the scope of the present disclosure.

Referring to fig. 1, fig. 1 is a schematic structural diagram of a grid-connected system according to an embodiment of the present application. As shown in fig. 1, the grid-tie system includes a light storage inverter 10, a photovoltaic inverter 20, a first load 30, and a second load 40.

The photovoltaic inverter 10, the first load 30 and the power grid 200 are connected to the first node N1, and the second load 40 and the power grid 200 are connected to the second node N2, respectively.

Wherein the photovoltaic inverter 20 is also connected to the first photovoltaic panel 300. The photovoltaic inverter 20 is capable of converting direct current generated by a solar photovoltaic panel (i.e., the first photovoltaic panel 300) into alternating current. Specifically, the photovoltaic inverter 20 inputs dc power, and outputs ac power meeting the power grid requirements through the inverter processing.

The first load 30 is a load network on the light storage inverter 10 and the photovoltaic inverter 20. The second load 40 is a load that is remote from the first load 30 or different from a transformer to which the first load 30 is connected, wherein the transformer is connected to the grid and is used to reduce the grid voltage. For example, in some embodiments, when the grid-tie system is used in a cottage, the first load 30 may be electricity used in the cottage, such as swimming pools; the second load 40 may be off-villa electricity, such as off-villa orchard electricity.

The light storage inverter 10, also referred to as a photovoltaic energy storage inverter, is a device that integrates a solar photovoltaic power generation system and an energy storage system. The light storage inverter 10 converts direct current generated by the solar photovoltaic panel into alternating current and stores the surplus electric energy into a battery or other energy storage device. When power is required, the light storage inverter can extract electric energy from the energy storage device and convert the electric energy into alternating current for household or commercial building use.

Referring to fig. 2 together, as shown in fig. 2, the light storage inverter 10 includes a controller 14.

In some embodiments, the controller 14 may be a general purpose processor, a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), a Field Programmable Gate Array (FPGA), a single-chip, ARM (Acorn RISC Machine) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, or any combination thereof. Also, the controller 14 may be any conventional processor, controller, microcontroller, or state machine. The controller 14 may also be implemented as a combination of computing devices, e.g., a combination of a DSP and a microprocessor, a plurality of microprocessors, one or more microprocessors in conjunction with a DSP and/or any other such configuration.

Referring to fig. 3, fig. 3 illustrates one configuration of the controller 14. As shown in fig. 3, the controller 14 includes: at least one processor 141; and a memory 142 communicatively coupled to the at least one processor 141, one processor 141 being illustrated in fig. 3. The memory 142 stores instructions executable by the at least one processor 141 to enable the at least one processor 141 to implement the grid-tie based control method of any of the embodiments of the present application. The processor 141 and the memory 142 may be connected by a bus or otherwise, for example in fig. 3.

The memory 142 serves as a non-volatile computer-readable storage medium for storing non-volatile software programs, non-volatile computer-executable programs, and modules. Processor 141 executes various functional applications of the server and data processing by running non-volatile software programs, instructions and modules stored in memory 142, i.e., implements the grid-tie-system-based control method in any of the embodiments of the present application.

Memory 142 may include a storage program area that may store an operating system, at least one application program required for functionality, and a storage data area; the storage data area may store data created according to the use of the data transmission device, and the like. In addition, memory 142 may include high-speed random access memory, and may also include non-volatile memory, such as at least one magnetic disk storage device, flash memory device, or other non-volatile solid-state storage device.

The one or more modules are stored in the memory 142, which when executed by the one or more processors 141, perform the grid-tie system based control method of any of the embodiments of the present application.

Referring back to fig. 2, the light storage inverter 10 further includes a photovoltaic converter 11, an energy storage converter 12, and an inverter 13.

The photovoltaic converter 11 is connected between the second photovoltaic panel 400 and the inverter 13. And the photovoltaic converter 11 is also connected to the controller 14. The photovoltaic converter is capable of converting direct current generated by the solar photovoltaic panel (i.e., the second photovoltaic panel 400) into alternating current. Also, the photovoltaic inverter 11 is controlled by the controller 14, i.e. the controller 14 is able to control the power output by the second photovoltaic panel 400 through the photovoltaic inverter 11 to increase, decrease or remain unchanged.

The energy storage converter 12 is connected between the battery 500 and the inverter 13, and the energy storage converter 12 is also connected to the controller 14. The energy storage converter is capable of converting the electrical energy stored in the battery 500 into alternating current or direct current. Wherein the energy storage converter 12 is controlled by the controller 14. That is, the controller 14 may control the charge-discharge power of the battery 500 to increase, decrease, or remain unchanged by controlling the energy storage converter 12.

The sum of the power output from the photovoltaic converter 11 and the power output from the energy storage converter 12 is the power input from the inverter 13. In turn, the controller 14 can control the power output by the inverter 13 by controlling the power output by the photovoltaic converter 11 and/or the power output by the energy storage converter 12 (i.e., the charge-discharge power of the battery 500). The inverter 13 is also connected to the first node N1, and the power output by the inverter 13 is the power output by the light storage inverter 10.

In one embodiment, the grid-tie system 100 further includes a third load 60 and a switch 50. The switch 50 is connected between the third load 60 and the first node N1, and the switch 50 is connected to the controller 14.

The third load 60 is a load that can be automatically controlled to be powered or powered off by the switch 50. Specifically, the controller 14 controls the switch 50 to be turned on or off to control the third load 60 to be powered on or powered off. Wherein the controller 14 controls the third load 60 to be powered when the switch 50 is closed, and the third load 60 consumes power; the controller 14 controls the third load 60 to lose power when the switch 50 is turned off, and the third load 60 consumes power.

In one embodiment, the grid-connected system 100 further includes a first transformer U1, a second transformer U2, a first electric meter 70 and a second electric meter 80.

The first transformer U1 and the second transformer U2 are used for reducing the voltage of the power grid 200.

The first electricity meter 70 is used to detect the power of the first node N1. And, the first electricity meter 70 establishes a communication connection with the controller 14 through the graph shown in fig. 2 to transmit the power of the first node N1 to the controller 14. In some embodiments, the first electricity meter 70 may be configured as a PCC electricity meter. Among these, the PCC meter (Point of Common Coupling Meter) is a meter for measuring and recording electrical energy data in an electrical power system. PCC meters are typically installed at a point of common coupling, also known as an access point or junction, of an electrical power system for monitoring and metering the power supply and load conditions of the electrical power system.

The second electricity meter 80 is used to detect the power of the second node N2. And, the second electricity meter 80 establishes a communication connection with the controller 14 through the graph shown in fig. 2 to transmit the power of the second node N2 to the controller 14. In some embodiments, the second electric meter 80 may be configured as a PCC electric meter.

It should be noted that the hardware configuration of the grid-tie system 100 as shown in fig. 2 is only one example, and the grid-tie system 100 may have more or fewer components than shown in the drawings, may combine two or more components, or may have different component configurations, and the various components shown in the drawings may be implemented in hardware, software, or a combination of hardware and software including one or more signal processing and/or application specific integrated circuits. For example, the grid-tie system 100 may further include a photovoltaic power meter connected between the photovoltaic inverter 20 and the first node N1, the photovoltaic power meter being configured to detect the output power of the photovoltaic inverter 20.

Referring to fig. 4, fig. 4 is a flowchart of a control method based on a grid-connected system according to an embodiment of the present application. The grid-connected system comprises a photovoltaic inverter, a light storage inverter, a first load and a second load, wherein the photovoltaic inverter is connected with the light storage inverter, the first load and a power grid respectively and is connected with a first node, and the second load is connected with the power grid and is connected with a second node. The specific structure of the grid-connected system may refer to the detailed descriptions of fig. 1 to 3, and will not be described herein.

As shown in fig. 4, the control method based on the grid-connected system includes the following steps:

step 401: the method comprises the steps of obtaining first power of a first node and second power of a second node.

Step 402: a power sum of the first power and the second power is calculated.

Step 403: and when the power sum is greater than zero, reducing the output power of the photovoltaic inverter and/or the output power of the optical storage inverter so as to reduce the power sum until the power sum is less than or equal to zero.

Specifically, taking the configuration shown in fig. 2 as an example, the first power (denoted as W1) of the first node N1 may be obtained through the first electric meter 70, and the second power (denoted as W2) of the second node N2 may be obtained through the second electric meter 80. Then, the first power and the second power are summed to obtain a power sum (i.e., W1+W2).

Then, if the sum of the power is smaller than zero (i.e. w1+w2 < 0), it can be determined that the illumination is weak at this time, and the total electric quantity output by the photovoltaic inverter 20 and the light storage inverter 20 is still insufficient to support the first load 30 and the second load 40 for power consumption. At this point, the full power output of the light storage inverter 20, i.e., the maximum power output of the light storage inverter 20, may be controlled to minimize power draw from the grid. And, the normal output of the photovoltaic inverter 10 is maintained without any limitation.

If the sum of the power is greater than zero (i.e., W1+W2 > 0), it can be determined that the total power output by the photovoltaic inverter 20 and the light storage inverter 20 is sufficient to support the first load 30 and the second load 40. And, at this time, there may be an abnormal situation in which grid-connected system 100 discharges to the grid, and therefore, it is necessary to reduce the output power of the photovoltaic inverter, and/or the output power of the photovoltaic inverter, to reduce the power sum until the power sum is less than or equal to zero. When the total power is controlled to be equal to zero, no electric quantity transmission process exists between the power grid and the grid-connected system; and when the total power is less than zero, discharging the grid to the grid-connected system. Therefore, the discharging process of the grid-connected system to the power grid is eliminated through the mode, and the purpose of preventing the grid-connected system from discharging to the power grid is achieved.

In an embodiment, when the grid-connected system 100 further includes the third load 60 and the switch 50 as shown in fig. 2, as shown in fig. 5, the specific implementation process of reducing the output power of the photovoltaic inverter and/or the output power of the photovoltaic inverter until the power sum is less than or equal to zero in step 403 includes the following steps:

step 501: and when the power sum is greater than zero, reducing the output power of the photovoltaic inverter, and/or the output power of the light storage inverter, and/or closing a switch to reduce the power sum until the power sum is less than or equal to zero.

Specifically, reducing the output power of at least one of the photovoltaic inverter 20 and the light storage inverter 10 can reduce the power sum. After the switch 50 is closed, the third load 60 is powered to consume power, and the purpose of reducing the total power can be achieved.

In another embodiment, when the light storage inverter 10 further includes the photovoltaic converter 11, the energy storage converter 12, and the inverter 13 as shown in fig. 2, the specific implementation process of reducing the output power of the photovoltaic inverter and/or closing the switch to reduce the power sum until the power sum is less than or equal to zero in step 501 when the power sum is greater than zero as shown in fig. 6 includes the following steps:

step 601: and when the power sum is greater than zero, adjusting the charge and discharge power of the battery to reduce the power sum until the power sum is less than or equal to zero.

Specifically, the purpose of reducing the total power can be achieved by adjusting the reduction of the discharge power of the battery or the increase of the charge power of the battery.

In one embodiment, as shown in fig. 7, when the sum of the power is greater than zero in step 601, the specific implementation process of adjusting the charge and discharge power of the battery to reduce the sum of the power until the sum of the power is less than or equal to zero includes the following steps:

step 701: and when the power sum is greater than zero, if the battery is determined to be in a discharging state, reducing the discharging power of the battery to reduce the power sum until the power sum is less than or equal to zero.

Step 702: and when the discharging power of the battery is reduced to zero, if the power sum is greater than zero, switching the battery to a charging state so as to reduce the power sum until the power sum is less than or equal to zero.

Specifically, when it is determined that the sum of the powers is greater than zero, it is first determined whether the battery 500 is in a discharged state. If it is determined that the battery 500 is in a discharged state, the battery 500 is controlled to gradually decrease the discharge power by controlling the energy storage converter 12. The power output from the light storage inverter 10 decreases, and the sum of the power decreases. Then, if the power sum can be reduced to less than or equal to zero, the discharge power of the battery 500 may no longer be reduced (in which case the discharge power of the battery 500 is still greater than zero), i.e., the discharge power of the battery 500 is kept unchanged. In addition, in this case, the power supply requirements of the first load 30 and the second load 40 can be satisfied by discharging the battery 500 in combination with the photovoltaic energy (i.e., the sum of the energy output from the photovoltaic inverter 20 and the photovoltaic converter 11), without taking power from the power grid 200.

However, if the discharge power of the battery 500 has been reduced to zero, but the total power is still greater than zero, then the battery 500 needs to be switched to a charged state. I.e. by controlling the energy storage converter 12 to charge the battery 500 and the charged power is derived from the power output by the photovoltaic converter 11. Meanwhile, as the charging power of the battery 500 increases, the power input to the inverter 13 may be reduced, and thus the power output from the inverter 13, that is, the power output from the light storage inverter 10 is reduced, and thus the sum of the power is also reduced. Then, if the power sum can be reduced to less than or equal to zero, the charging power of the battery 500 may not be increased any more, i.e., the discharging power of the battery 500 is kept unchanged. In addition, in this case, the photovoltaic energy is already greater than the power supply requirements of the first load 30 and the second load 40, and the battery 500 can be charged to absorb the redundant photovoltaic energy, so that the waste caused by discarding the light can be avoided.

In an embodiment, as shown in fig. 8, when the power sum is greater than zero in step 501, the output power of the photovoltaic inverter is reduced, and/or the output power of the photovoltaic inverter is/are reduced, and/or the switch is closed, so as to reduce the power sum until the power sum is less than or equal to zero, and the specific implementation process further includes the following steps:

step 801: after the battery is switched to a charging state, if the charging power of the battery is larger than the rated power of the third load, the switch is closed.

Specifically, after step 702 is performed, the battery 500 has been switched to a charged state. Thereafter, the charging power of the battery 500 is gradually increased until the power sum is not reduced to less than or equal to zero. When the charging power of the battery 500 is increased to be greater than the rated power of the third load 60, it can be determined that the photovoltaic energy at this time can satisfy not only the power supply requirements of the first load 30 and the second load 40, but also the power supply requirement of the third load 60. In turn, switch 50 may be closed to energize third load 60. Therefore, the third load 60 can be put into use only when the illumination condition is sufficient, and the management of each load can be more reasonably realized so as to ensure the stable operation of each load.

Then, after closing the switch, the present application also provides a way to open the switch. Specifically, the control method based on the grid-connected system further comprises the following steps: if the battery is switched to a discharge state, the switch is turned off.

Specifically, when the battery 500 is switched to the discharge state again in the application scenario after the switch 50 is closed, for example, when the illumination becomes weak enough to satisfy the power supply requirements of the first load 30 and the second load 40 and the battery 500 needs to be switched to the discharge state, the switch 50 is turned off to keep the electric quantity of the battery 500.

Reference is made specifically to fig. 9 for power up or power down of the third load 60. As shown in fig. 9, when the battery 500 is charged to a power equal to the rated power Z1 of the third load 60, the third load 60 is put in, i.e., the switch 50 is closed to energize the third load 60. Thereafter, as long as the battery 500 is in a charged state, the third load 60 remains put into operation.

The third load 60 is not cut off, i.e., the switch 50 is opened to de-energize the third load 60, until the battery 500 is switched to a discharged state. Thereafter, even if the battery 500 is switched to the charged state, the third charge 60 remains switched off as long as the charged power of the battery 500 does not reach the rated power Z1 of the third load 60.

In summary, the hysteresis control method of the third load 60 is realized, so that the third load 60 can be prevented from being repeatedly put into and cut out, which is beneficial to improving the working stability of the third load 60 and prolonging the service life thereof.

In an embodiment, as shown in fig. 10, when the power sum is greater than zero in step 501, the output power of the photovoltaic inverter is reduced, and/or the output power of the photovoltaic inverter is/are reduced, and/or the switch is closed, so as to reduce the power sum until the power sum is less than or equal to zero, and the specific implementation process further includes the following steps:

step 1001: after the switch is closed, if the charging power of the battery is rated charging power and the sum of the power is greater than zero, the power output by the photovoltaic panel through the photovoltaic converter is reduced so as to reduce the sum of the power until the sum of the power is less than or equal to zero.

Specifically, after step 801 is performed, the first load 30, the second load 40, and the third load 60 are all in the powered state, and the battery 500 is in the charged state. In this case, it may be determined that the illumination energy is strong so that the photovoltaic energy can not only satisfy the power supply requirements of the first load 30, the second load 40, and the third load 60, but also charge the battery 500.

Further, if the obtained power sum is reduced to be less than or equal to zero before the charging power of the battery 500 reaches the rated charging power, the current charging power of the battery 500 is kept unchanged, so as to keep the power supply requirements of the first load 30, the second load 40 and the third load 60 satisfied.

If the sum of the obtained power is still greater than zero after the charging power of the battery 500 reaches the rated charging power, the photovoltaic energy needs to be reduced at this time to prevent the grid-connected system 100 from discharging to the grid 500, thereby achieving the purpose of preventing backflow. In this case, since the photovoltaic inverter 11 is directly controlled by the controller 14, it has more excellent response speed and control accuracy, the power output from the second photovoltaic panel 400 through the photovoltaic inverter 11 is first reduced to reduce the power output from the inverter 13, and thus the power output from the light storage inverter 10.

In an embodiment, as shown in fig. 11, when the power sum is greater than zero in step 501, the output power of the photovoltaic inverter is reduced, and/or the output power of the photovoltaic inverter is/are reduced, and/or the switch is closed, so as to reduce the power sum until the power sum is less than or equal to zero, and the specific implementation process further includes the following steps:

step 1101: after the power output by the photovoltaic panel through the photovoltaic converter is reduced, if the power output by the photovoltaic converter is reduced to zero and the sum of the power is greater than zero, the output power of the photovoltaic inverter is reduced to reduce the sum of the power until the sum of the power is less than or equal to zero.

Specifically, after step 1001 is performed, if the sum of the obtained power of the output power of the photovoltaic inverter is reduced to less than or equal to zero before the power of the output power of the photovoltaic inverter is reduced to zero, the output power of the photovoltaic inverter is kept unchanged, so as to meet the power supply requirements of the first load 30, the second load 40 and the third load 60.

If the sum of the obtained power is still greater than zero after the power output by the photovoltaic inverter is reduced to zero, it may be determined that the energy output by the photovoltaic inverter 20 alone at this time is still remaining on the basis of satisfying the power supply requirements of the first load 30, the second load 40 and the third load 60 and charging the battery 500 with the rated power, and the output power of the photovoltaic inverter 20 needs to be reduced. Specifically, the controller 14 is communicatively connected to the photovoltaic inverter 20 through a dotted line as shown in fig. 2, and generates a communication command to the photovoltaic inverter 20 to cause the photovoltaic inverter 20 to reduce the output power. The sum of the powers is reduced until the sum of the powers is less than or equal to zero. Thus, the grid-connected system 100 is prevented from discharging to the grid 500, i.e., the anti-reverse flow function is realized.

For a better understanding of the present application, a description will be given below of how the reverse flow prevention process is implemented, taking the graph shown in fig. 12 as an example. Wherein a graph of power in a grid-tie system under different lighting conditions is shown in fig. 12.

As shown in fig. 12, the abscissa is the light condition, and the light condition gradually increases from right to left; the ordinate is power. Curve S1 is the photovoltaic power (denoted as P1) output by photovoltaic inverter 20; curve S2 is the photovoltaic power output by the photovoltaic inverter 10, i.e., the photovoltaic power output by the photovoltaic converter 11 (denoted as P2); the curve S3 is the charge/discharge power of the battery 500 (where the charge power is denoted as P3 and the discharge power is denoted as P4).

Before the light conditions are weaker and the light condition L1 is not reached, the sum of the powers obtained at this time is smaller than zero, i.e. w1+w2 < 0. The photovoltaic inverter 20 outputs the maximum photovoltaic power P1MAX, the light storage inverter 10 outputs the maximum photovoltaic power P2MAX, and the battery 500 outputs the maximum discharge power P3MAX1. At this time, p1max+p2max+p3max1 < z1+z2, where Z1 is the power consumption of the first load 30 and Z2 is the power consumption of the second load 40. Power is still required to be drawn to the grid 500. Of course, at this point the switch 50 is closed and the third load 60 is not energized.

If the illumination condition reaches L1, and before L2 is not reached, the photovoltaic energy is enhanced due to the enhancement of the illumination condition, so that P1MAX+P2MAX+P3MAX1 > Z1+Z2. In this case, W1+W2 > 0, there is a risk of reverse flow. The discharge power of the battery 500 should start to be reduced so that w1+w2 is reduced. Until w1+w2=0 to achieve the reverse flow prevention.

If the illumination condition reaches L2, and before L3 is not reached, the photovoltaic energy continues to be increased due to the increase in the illumination condition, such that P1MAX+P2MAX > Z1+Z2. In this case, W1+W2 > 0, there is a risk of reverse flow. Then, the battery 500 should be switched to the charged state to reduce w1+w2, and at the same time, the waste of electricity caused by discarding light can be avoided. If p1max+p2max=z1+z2+p4 can be reached with an increase in the charging power of the battery 500 during the charging of the battery 500, w1+w2=0 can be realized, thereby realizing backflow prevention; if the charging power of the battery 500 has reached the rated charging power P4MAX during the charging of the battery 500, the switch 50 is closed to power up the third load 60 to keep the third load 60 stably operating.

If the illumination condition reaches L3, and before L4 is not reached, the photovoltaic energy continues to increase due to the increase in the illumination condition, such that P1MAX+P2MAX > Z1+Z2+Z3+P4MAX. Wherein Z3 is the operating power of the third load 60. At this time, the sum of the photovoltaic power provided by the photovoltaic inverter 20 and the photovoltaic inverter 10 is greater than the sum of the power required by the first charge 30, the second charge 40, and the third charge 60 and the maximum charging power of the battery 500, w1+w2 > 0, and there is a risk of backflow. Then, it is necessary to start reducing the photovoltaic power P2 of the light storage inverter 10 so that w1+w2 is reduced. Until w1+w2=0 to achieve the reverse flow prevention.

If the illumination condition reaches L4, the photovoltaic energy is further enhanced due to the enhancement of the illumination condition, so that P1MAX > Z1+Z2+Z3+P4MAX. At this time, although the photovoltaic power P2 of the light storage inverter 10 has been reduced to zero, the output power of the photovoltaic inverter 20 is still greater than the sum of the power required by the first, second and third charges 30, 40, 60 and the maximum charging power of the battery 500, w1+w2 > 0, and there is a risk of backflow. Then, it is necessary to start reducing the photovoltaic power P1 of the photovoltaic inverter 20 so that w1+w2 is reduced. Until w1+w2=0 to achieve the reverse flow prevention.

Finally, it should be noted that: the above embodiments are only for illustrating the technical solution of the present application, and are not limiting thereof; the technical features of the above embodiments or in the different embodiments may also be combined under the idea of the present application, the steps may be implemented in any order, and there are many other variations of the different aspects of the present application as described above, which are not provided in details for the sake of brevity; 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 of the corresponding technical solutions from the scope of the technical solutions of the embodiments of the present application.

Claims

1. The control method based on the grid-connected system is characterized in that the grid-connected system comprises a photovoltaic inverter, a light storage inverter, a first load, a second load, a third load and a switch, wherein the photovoltaic inverter is respectively connected with the light storage inverter, the first load and a power grid to form a first node, the second load is connected with the power grid to form a second node, and the switch is connected between the third load and the first node;

the photovoltaic inverter comprises a photovoltaic converter, an energy storage converter and an inverter, wherein the photovoltaic converter is connected between a photovoltaic panel and the inverter, the energy storage converter is connected between a battery and the inverter, and the inverter is connected to the first node, and the method comprises the following steps:

acquiring first power of the first node and second power of the second node;

calculating a power sum of the first power and the second power;

when the discharging power of the battery is reduced to zero, if the power sum is greater than zero, switching the battery to a charging state so as to reduce the power sum until the power sum is less than or equal to zero;

after the battery is switched to a charging state, if the charging power of the battery is larger than the rated power of the third load, closing the switch;

opening the switch if the battery is switched to a discharged state after the switch is closed;

after the switch is closed, if the charging power of the battery is rated charging power and the sum of the power is greater than zero, reducing the power output by the photovoltaic panel through the photovoltaic converter to reduce the sum of the power until the sum of the power is less than or equal to zero;

2. The method according to claim 1, wherein the method further comprises:

3. A grid-tie system, comprising:

the light storage inverter includes a controller including:

at least one processor and a memory communicatively coupled to the at least one processor, the memory storing instructions executable by the at least one processor to enable the at least one processor to perform the method of any one of claims 1-2.

4. The grid-tie system of claim 3, further comprising:

5. The grid-tie system of claim 3 or 4, wherein the light storage inverter further comprises a photovoltaic converter, an energy storage converter and an inverter, the photovoltaic converter is connected between a photovoltaic panel and the inverter, the energy storage converter is connected between a battery and the inverter, the inverter is connected to the first node, and the controller is connected to the photovoltaic converter and the energy storage converter, respectively;