WO2015003443A1

WO2015003443A1 - Anti-countercurrent grid-connected photovoltaic power generation system

Info

Publication number: WO2015003443A1
Application number: PCT/CN2013/086634
Authority: WO
Inventors: 崔明; 宋行宾; 韩晓艳; 杨培环
Original assignee: 京东方科技集团股份有限公司; 北京京东方能源科技有限公司
Priority date: 2013-07-09
Filing date: 2013-11-06
Publication date: 2015-01-15
Also published as: CN103346587B; CN103346587A

Abstract

An anti-countercurrent grid-connected photovoltaic power generation system (1) comprises at least one inverter (11) and an acquisition and control unit (12) connected with each inverter. The acquisition and control unit determines whether a countercurrent phenomenon occurs according to power output to a load (3) by a public power grid (2) and power output to the load by the grid-connected photovoltaic power generation system, which are acquired in real time. When it is determined that a countercurrent phenomenon occurs, the acquisition and control unit controls operation of the inverter, and reduces the power output to the load by the anti-countercurrent grid-connected photovoltaic power generation system until the acquisition and control unit determines that no trend toward a countercurrent phenomenon exists. The system can predict occurrence of a countercurrent phenomenon in advance, and avoid occurrence of the countercurrent phenomenon.

Description

Anti-countercurrent photovoltaic grid-connected power generation system

The invention relates to a photovoltaic power generation grid-connecting technology, in particular to a backflow prevention photovoltaic grid-connected power generation system.

Background technique

In order to achieve sustainable energy and environmental development, solar photovoltaic power generation in the world regards the development of new energy and renewable energy. At present, the photovoltaic power generation grid-connected system can be divided into two types of photovoltaic grid-connected power generation systems, namely, reversible flow and non-reversible flow. The non-reversible flow system means that the power generation of the photovoltaic grid-connected system is always less than or equal to the power consumption of the load. When the power is insufficient, the power is supplied by the grid. That is, the photovoltaic grid-connected power generation system and the power grid form a dual power supply to supply power to the load. Even if the residual electric energy is generated for some reason, it can only be handled or abandoned by technical means. Since there is no case where the photovoltaic grid-connected system transmits power to the grid, it is called a non-reversible flow system.

In order to ensure the safety and stability of the public power grid, most of the photovoltaic grid-connected power generation systems require a no-flow system. In order to ensure that the PV grid-connected power generation system does not have reverse-current reverse power into the public power grid, the photovoltaic grid-connected power generation system must have anti-backflow function.

In the prior art, the direction and magnitude of voltage, current and power of the photovoltaic grid-connected power generation system are collected and detected by adding an acquisition device, and these data are analyzed by a reverse power relay to determine whether a backflow phenomenon occurs, and then the control signal is output to the control network. The AC side performs power regulation to achieve reverse current protection. This protection mode can only issue a control signal for reverse current protection when a backflow phenomenon occurs, and the countercurrent phenomenon cannot be predicted in advance, so that the countercurrent phenomenon cannot be completely avoided.

Summary of the invention

In order to solve the technical problems existing in the prior art, embodiments of the present invention provide a backflow prevention photovoltaic grid-connected power generation system, which can predict the occurrence of the reverse flow phenomenon in advance, thereby completely avoiding the occurrence of the reverse flow phenomenon.

Embodiments of the present invention adopt the following technical solutions:

An anti-backflow photovoltaic grid-connected power generation system, comprising at least one inverter, and an acquisition control unit connected to each of the inverters;

The acquisition control unit outputs the work of the public power grid to the load according to the real-time acquisition Rate, and the power output by the photovoltaic grid-connected power generation system to the load, to determine whether there is a trend of countercurrent phenomenon;

When it is determined that there is a trend of the occurrence of the flow phenomenon, the acquisition control unit controls the operation of the inverter, and reduces the power output by the anti-backflow photovoltaic grid-connected power generation system to the load until the control acquisition unit determines There is no tendency for countercurrent phenomena to occur.

Optionally, a preset power unit is disposed in the collection control unit, and the power output by the collection control unit to the load is reduced to a preset power, and the photovoltaic grid-connected power generation system is When the power output to the load is gradually increased, the acquisition control unit sends a derated output command to at least one inverter in the anti-backflow photovoltaic grid-connected power generation system, so that the first inverter is directed to the load The output power is reduced by a certain amount until the power of the public grid to the load obtained by the control acquisition unit is increased to above the preset power, and the power of the photovoltaic grid-connected power generation system to the load is no longer increased. .

Optionally, the preset power may be determined according to an actual output power of the public grid and the photovoltaic grid. In theory, the preset power may be set to an arbitrary value between 0 and a maximum power output from the public grid to the load. The preset power unit may be integrally disposed in the acquisition control unit.

Optionally, the collection control unit has an interface for adjusting the preset power, so that the preset power may be set according to a specific situation.

Optionally, the anti-backflow photovoltaic grid-connected power generation system includes a plurality of inverters; if the power output by the at least one inverter to the load is reduced to 0, and the acquisition control unit collects the obtained The power output by the public power grid to the load still does not exceed the preset power, and the power output by the photovoltaic grid-connected power generation system to the load still increases;

The acquisition control unit sends a shutdown instruction to the at least one inverter to stop the at least one inverter while at least one of the inverters that are not stopped in the anti-countercurrent photovoltaic grid-connected power generation system The transformer sends a derating output command, so that the power output by the at least one inverter of the non-stopped inverter to the load is reduced by a certain amount until the control acquisition unit collects the obtained public grid direction The power of the load is increased above the preset power, and the power output by the photovoltaic grid-connected power generation system to the load is no longer increased.

Optionally, the acquisition control unit is further configured to output to the load on the public power grid. When the sum of the power and the power outputted by the photovoltaic grid-connected power generation system to the load increases, sending a power-on command to the stopped inverter, and sending an increased output command to the de-rated output inverter, so that the shutdown The inverter is powered on, and the power output by the derated output inverter to the load is increased by a certain amount.

Optionally, the acquisition control unit is based on digital signal processing digital signal processing

(Digital Signal Processing, DSP) processor hardware platform; Bei' J,

The acquisition control unit is connected to each of the inverters through a serial communication interface or an Ethernet port, so that the power output by each inverter to the load is collected in real time, thereby obtaining the photovoltaic grid-connected power generation system to the load. Output power;

The acquisition control unit is connected to the low-voltage power distribution side multi-function electric meter of the public power grid through a serial communication interface or an Ethernet port, and the real-time acquisition and acquisition of the power output by the public power grid to the load.

Optionally, the collection control unit is connected to each of the inverters by using a communication cable; and the collection control unit is connected to a low-voltage distribution side multi-function meter of the public power grid by using a communication cable.

The anti-countercurrent photovoltaic grid-connected power generation system provided by the embodiment of the present invention, the acquisition control unit obtains the power output by the public grid to the load according to real-time acquisition, and the power output by the photovoltaic grid-connected power generation system to the load, and determines whether there is a trend of occurrence of a countercurrent phenomenon; and when determining a trend of occurrence of a flow phenomenon, controlling the operation of the inverter, reducing the power output by the anti-backflow photovoltaic grid-connected power generation system to the load until the control acquisition The unit judges that there is no tendency for the countercurrent phenomenon to occur. In this way, the acquisition control unit can control the operation of the inverter to prevent the occurrence of the reverse flow phenomenon before the occurrence of the reverse flow phenomenon, so that the occurrence of the reverse flow phenomenon can be predicted in advance, thereby completely avoiding the occurrence of the reverse flow phenomenon.

DRAWINGS

FIG. 1 is a schematic structural diagram of a grid-connected photovoltaic grid-connected power generation system and a public grid grid-connected power generation according to an embodiment of the present invention.

Description of the reference numerals

1- anti-countercurrent photovoltaic grid-connected power generation system, 2-public grid, 3-load, 11-inverter, 12-acquisition control unit, 21-multi-function meter. detailed description

The technical solutions in the embodiments of the present invention are clearly and completely described in the following with reference to the accompanying drawings. It is to be understood that the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments.

Embodiments of the present invention provide a backflow prevention photovoltaic grid-connected power generation system. As shown in FIG. 1, the anti-backflow photovoltaic grid-connected power generation system 1 includes at least one inverter 1 1 and an acquisition control unit 12 connected to each of the inverters 1 1 .

The acquisition control unit 12 determines whether there is a trend of occurrence of a backflow phenomenon according to the power output from the public power grid 2 to the load 3 obtained by the real-time acquisition and the power output by the photovoltaic grid-connected power generation system 1 to the load 3; When there is a trend of the flow phenomenon, the acquisition control unit 12 controls the operation of the inverter 1 1 to reduce the power output by the anti-backflow photovoltaic grid-connected power generation system 1 to the load until the control acquisition The unit judges that there is no tendency for the countercurrent phenomenon to occur.

The acquisition control unit 12 can separately collect the power output from the public power grid 2 to the load 3 and the power output by the photovoltaic grid-connected power generation system 1 to the load 3. Then, according to the power output from the public grid obtained by the real-time acquisition to the load, and the change of the power output by the photovoltaic grid-connected power generation system to the load, the occurrence of the reverse flow phenomenon is predicted in advance, and then the inverter is controlled by Working, reducing the power outputted by the anti-backflow photovoltaic grid-connected power generation system to the load, thereby completely avoiding the occurrence of a backflow phenomenon.

Optionally, the collection control unit 1 2 may be configured with a preset power unit, when the power output by the public power grid 2 to the load 3 is reduced to a preset power, and the photovoltaic grid-connected power generation system 1 is loaded to the load. When the output power of the output is gradually increased, the acquisition control unit 12 can determine the trend of the occurrence of the reverse flow phenomenon, and the acquisition control unit 12 can be used in the anti-countercurrent photovoltaic grid-connected power generation system 1 At least one inverter sends a derated output command, so that the power output by the at least one inverter to the load is reduced by a certain amount until the power output by the acquisition control unit to the utility grid is increased. Up to the preset power, and the power output by the photovoltaic grid-connected power generation system to the load is no longer increased, that is, until the control acquisition unit determines that there is no tendency for the reverse flow phenomenon to occur.

In the embodiment of the present invention, the preset power may be determined according to an actual output power of a public grid and a photovoltaic grid. In theory, the preset power may be set to be greater than 0 to a maximum power output from the public grid to the load. Any value. The preset power unit can be set The grounding is disposed in the collection control unit. Optionally, the collection control unit has an interface for adjusting the preset power, so that the preset power can be set according to a specific situation.

In the embodiment of the present invention, the sum of the power output by the public power grid 2 to the load 3 and the power output by the photovoltaic grid-connected power generation system 1 to the load 3 is the sum of the power consumption of the load on the user side. The power output from the public power grid 2 to the load 3 is gradually reduced, and when the power output from the photovoltaic grid-connected power generation system 1 to the load 3 is gradually increased, the photovoltaic grid-connected power generation system 1 gradually occupies the dominant power supply for the load 3. . When the power output by the utility grid 2 to the load 3 is reduced to zero, it is stated that the photovoltaic grid-connected power generation system 1 completely replaces the utility grid 2 to supply the load 3. When the power output by the public power grid 2 to the load 3 is reduced to a negative value, it is indicated that the photovoltaic grid-connected power generation system 1 not only completely replaces the public power grid 2 to supply power to the load 3, but also generates residual power. A countercurrent phenomenon in which the photovoltaic grid-connected power generation system 1 transmits power to the public power grid 2 occurs.

It can be seen from the above that the acquisition control unit 12 can preset a preset power, and the preset power tends to 0 but greater than 0, and the specific value can be determined according to actual conditions. When the power output from the public network 2 to the load obtained by the acquisition control unit 12 is reduced to a preset power, and the power of the photovoltaic grid-connected power generation system 1 is gradually increased, the description is about to occur. a countercurrent phenomenon, at this time, the acquisition control unit 12 sends a derating output command to at least one inverter in the anti-backflow photovoltaic grid-connected power generation system, and outputs the at least one inverter to the load The power is reduced by a certain amount, thus suppressing the power output by the photovoltaic grid-connected power generation system 1 to the load. At the same time, the acquisition control unit 12 also collects the power obtained by the public grid 2 to the load in real time, and the power output by the photovoltaic grid-connected power generation system 1 to the load. If the power output by the public power grid 2 to the load 3 does not exceed the preset power, and the power output by the photovoltaic grid-connected power generation system 1 to the load 3 still increases, the acquisition control unit 12 continues. Sending a derating output command to the at least one inverter in the anti-countercurrent photovoltaic grid-connected power generation system 1 to curb the power output by the photovoltaic grid-connected power generation system 1 to the load until the control acquisition unit 12 The power outputted by the public grid 2 to the load is increased to above the preset power, and the power of the photovoltaic grid-connected power generation system 1 to the load is no longer increased, that is, until there is no trend of backflow phenomenon .

It should be noted here that when the acquisition control unit 12 predicts that an inverse will occur In the case of a flow phenomenon, the acquisition control unit 12 may send a derating output command to one inverter in the photovoltaic grid-connected power generation system 1, or may also send multiple inversions to the photovoltaic grid-connected power generation system 1. Even all of the inverters send a derated output command to reduce the power output by the at least one inverter to the load by a certain amount. Here, the reduced amount may be carried in the derating output command to be sent to the inverter; or may be preset in the inverter, after the inverter receives the derating output command, The power output by the inverter to the load is reduced by a certain amount. The value of the reduced amount may be any value, for example, may be 1 / 3 of the current power generated by the inverter, or may be a fixed value of 100 W, and the like.

Optionally, if the at least one inverter is one or more inverters in the volt-connected power generation system 1, instead of all the inverters, the at least one inverter is When the power of the load 3 output is reduced to 0, the following may occur: the power output by the acquisition control unit 12 to the utility grid 2 to the load 3 still does not exceed the preset power, and the photovoltaic The power output from the network power generation system 1 to the load 3 is still increasing, that is, there is still a tendency for a reverse flow phenomenon to occur. At this time, the acquisition control unit 12 may send a shutdown instruction to the at least one inverter, so that the An inverter is stopped, and at least one inverter in the non-stopped inverter in the anti-backflow photovoltaic grid-connected power generation system transmits a derating output command, so that at least one of the non-stopped inverters is reversed The power output from the transformer to the load 3 is reduced by a certain amount until the power output from the public network 2 to the load 3 obtained by the control acquisition unit 12 is increased to the preset power On to, and the photovoltaic power generation system 1 to the output power to the load 3 not increase.

In summary, the acquisition control unit 12 may select to send a derated output command to any one or more inverters when it is predicted that a reverse flow phenomenon is to occur, and determine any one or more inverters in the one or more inverters. Whether the countercurrent phenomenon is suppressed after derating the output power, and if not, continues to derate the output of any one or more inverters until the one or more inverters are When the power of the load output is reduced to 0, the backflow phenomenon is still not contained, and the acquisition control unit 12 can send a shutdown instruction to the any one or more inverters to stop the operation, and continue to the defense. Any one or more of the inverters that are not stopped in the counter current photovoltaic grid-connected power generation system transmit a derated output command until the control acquisition unit 12 determines that there is no tendency for a backflow phenomenon to occur.

The acquisition control unit 12 is also used for the work outputted by the public power grid 2 to the load 3. When the sum of the power output from the photovoltaic grid-connected power generation system 1 to the load 3 increases, that is, when the power consumption of the load 3 increases, the power-on command is sent to the stopped inverter, and the inverter is output to the derating. The device sends an incremental output command to turn on the stopped inverter to increase the power output by the derated output inverter to the load by a certain amount. The increased amount may be carried in the incremental output command and sent to the inverter; or may be preset in the inverter. After receiving the incremental output command, the inverter increases the power output by the inverter to the load by a certain amount. The increased amount may be any value, for example, the increased amount may be a fixed value of 100 W, and the increased amount may also increase the power output by the inverter to the load to the inverter. The full amount of power output, etc.

In this way, when a countercurrent phenomenon occurs, the power of the photovoltaic grid-connected power generation system to the load is reduced, and when the reverse current phenomenon does not occur, and the power consumption of the load increases, the power of the photovoltaic grid-connected power generation system to the load is increased. It can realize the intelligent balance between the power generation capacity of the photovoltaic grid-connected power generation system and the load power consumption, and the automatic recovery function of the photovoltaic grid-connected power generation system, so that the photovoltaic grid-connected power generation system has the optimal use efficiency and running time.

Optionally, in the embodiment of the present invention, the acquisition control unit 12 may be a hardware platform based on a DSP microprocessor; therefore, the acquisition control unit may be externally connected through a serial communication interface or an Ethernet interface.

Therefore, the acquisition control unit 12 can be connected to each of the inverters through a serial communication interface or an Ethernet port, thereby real-time collecting the power output by each inverter to the load, thereby obtaining the photovoltaic and The power output from the grid power system 1 to the load. The power output by the photovoltaic grid-connected power generation system to the load is the sum of the powers of all the inverters in the photovoltaic grid-connected power generation system 1 to the load.

The acquisition control unit 12 can also be connected to the low-voltage power distribution side multi-function electric meter of the public power grid through a serial communication interface or an Ethernet port, thereby real-time collecting and obtaining the power output by the public power grid to the load.

Illustratively, the acquisition control unit 12 is connected to each of the inverters 1 1 by using a communication cable; the acquisition control unit 12 and the low-voltage distribution side multi-function electricity meter 21 of the public power grid 2 Communication cables are also used for connection.

With the prior art, the power load control PLC (Power load ing control) needs to increase The acquisition device and the transmitter use the analog acquisition cable to collect data, and the control signal cable is used to send the control signal to the control system. The acquisition control unit is used in the embodiment of the present invention.

1 2 Data acquisition and power adjustment can be realized by communication cable, the wiring tube is convenient, and the structure is also simple.

The above is only the specific embodiment of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily think of changes or substitutions within the technical scope of the present invention. It should be covered by the scope of the present invention. Therefore, the scope of the invention should be determined by the scope of the claims.

Claims

claims

1. An anti-backflow photovoltaic grid-connected power generation system, including:

At least one inverter;

a collection control unit connected to each of said inverters,

The acquisition control unit determines whether there is a tendency for a reverse flow phenomenon to occur based on the power output by the public power grid to the load and the power output by the photovoltaic grid-connected power generation system to the load obtained through real-time collection;

When the trend of flow phenomenon is determined, the acquisition control unit controls the operation of the inverter and reduces the power output by the anti-backflow photovoltaic grid-connected power generation system to the load until the control acquisition unit determines There is no tendency for countercurrent phenomenon to occur.

2. The anti-backflow photovoltaic grid-connected power generation system according to claim 1, wherein the collection control unit is provided with a preset power unit. When the collection control unit collects the power output by the public power grid to the load, When the power is reduced to the preset power and the power output by the photovoltaic grid-connected power generation system to the load gradually increases, the collection control unit sends a derating signal to at least one inverter in the anti-backflow photovoltaic grid-connected power generation system. Output instructions to reduce the power output by the first inverter to the load by a certain amount until the power from the public grid to the load collected by the control acquisition unit increases above the preset power, and The power of the photovoltaic grid-connected power generation system to the load no longer increases.

3. The anti-backflow photovoltaic grid-connected power generation system according to claim 2, wherein the preset power unit can be integrally provided in the collection control unit.

4. The anti-backflow photovoltaic grid-connected power generation system according to claim 2, wherein the collection control unit has an interface for adjusting the preset power, so that the preset power can be set according to specific conditions.

5. The anti-backflow photovoltaic grid-connected power generation system according to claim 2, including multiple inverters;

If the power output by the at least one inverter to the load is reduced to 0, and the power output by the public grid to the load collected by the collection control unit still does not exceed the preset power, the photovoltaic When the power output by the grid-connected power generation system to the load is still increasing, the acquisition control unit sends a shutdown command to the at least one inverter to shut down the at least one inverter, and at the same time sends the anti-backflow photovoltaic grid connection There is no shutdown in the power generation system At least one of the inverters sends a derating output command to reduce the power output by at least one of the inverters that is not shut down to the load by a certain amount until the control collects The power collected by the unit from the public grid to the load increases above the preset power, and the power output by the photovoltaic grid-connected power generation system to the load no longer increases.

6. The anti-backflow photovoltaic grid-connected power generation system according to claim 5, wherein the acquisition control unit is further configured to determine the difference between the power output by the public grid to the load and the power of the photovoltaic grid-connected power generation system to the load. When the sum increases, a startup command is sent to the stopped inverter, and an increase output command is sent to the inverter with derated output, so that the stopped inverter is started, and the inverter with derated output is started. The power output to the load is increased by a certain amount.

7. The anti-backflow photovoltaic grid-connected power generation system according to any one of claims 1 to 6, wherein the acquisition control unit is a hardware platform based on a digital signal processing DSP microprocessor - the acquisition control unit passes a serial The communication interface or Ethernet port is connected to each of the inverters, so as to collect the power output by each inverter to the load in real time, and then obtain the power output by the photovoltaic grid-connected power generation system to the load;

The collection control unit is connected to the multi-function meter on the low-voltage distribution side of the public power grid through a serial communication interface or an Ethernet port, and then collects and obtains the power output by the public power grid to the load in real time.

8. The anti-backflow photovoltaic grid-connected power generation system according to claim 7, wherein the collection control unit and each of the inverters are connected using communication cables; the collection control unit and the public power grid are connected. The multi-function meters on the low-voltage distribution side are connected using communication cables.