CN219107064U

CN219107064U - Grid-connected power generation system

Info

Publication number: CN219107064U
Application number: CN202223022620.4U
Authority: CN
Inventors: 张中洋; 李海涛; 相国华; 程林; 潘年安
Original assignee: Sungrow Power Supply Co Ltd
Current assignee: Sungrow Power Supply Co Ltd
Priority date: 2022-11-14
Filing date: 2022-11-14
Publication date: 2023-05-30
Anticipated expiration: 2032-11-14

Abstract

The application discloses a grid-connected power generation system, include: breaking equipment and a transformer; the transformer is connected with a power grid through breaking equipment; when the power grid is three-phase, the breaking equipment comprises three groups of independent switches, and each phase of the three-phase power grid is connected with one group of switches in series; when the breaking equipment is closed, the three groups of independent switches are closed independently and sequentially. When the electric wire netting is thrown, in order to reduce the electric wire netting and throw in the moment to the impact of transformer and other medium-high voltage devices, improve life, need the electric wire netting throw in the front to the transformer excitation, establish the both ends of breaking equipment with the same amplitude same phase voltage of electric wire netting, then just can be closed a floodgate, this application only changes the switch in the breaking equipment into three independent switches of group, separately independent control, but let three switch of group as a whole linkage to can reduce the impact to transformer and other devices when electric wire netting throw in, improve its life.

Description

Grid-connected power generation system

Technical Field

The application relates to the technical field of new energy power generation, in particular to a grid-connected power generation system.

Background

At present, a distributed grid-connected power generation system comprises a plurality of subarrays, each subarray comprises a plurality of inverters, the output ends of the inverters of each subarray are converged and then transformed by corresponding subarray transformers, and energy is fed to a power grid after transformation.

For example, when the dc source of the distributed grid-connected power generation system is a photovoltaic array, the inverter is in a standby state due to poor lighting conditions such as night or rainy days, and if the transformer is always connected to the power grid, no-load loss is generated, so that the switch is connected between the transformer and the power grid.

However, when the opening switch is closed, impact is generated to the transformer and the switch, and the service life is reduced.

Disclosure of Invention

In view of this, the application provides a grid-connected power generation system, can reduce the impact to transformer and other devices when the electric wire netting is thrown, improves its life.

The application provides a grid-connected power generation system, comprising: breaking equipment and a transformer;

the transformer is connected with a power grid through breaking equipment;

when the power grid is three-phase, the breaking equipment comprises three groups of independent switches, and each phase of the three-phase power grid is connected with one group of switches in series;

when the breaking equipment is closed, the three groups of independent switches are closed independently and sequentially.

Preferably, the power supply includes: n subarrays;

each sub-array comprises a plurality of energy conversion devices;

n transformers are provided; n is an integer greater than or equal to 1;

the N subarrays are in one-to-one correspondence with the N transformers, and the output end of each subarray is connected with the primary side of the corresponding transformer.

Preferably, the power supply includes: n subarrays; n is an integer greater than or equal to 1; the subarrays correspond to the same transformer;

each sub-array comprises at least one energy conversion device;

the output end of each subarray is connected with the primary side of the corresponding transformer.

Preferably, the method further comprises: a controller;

and the controller is used for controlling the switch of the corresponding phase to be closed at the minimum point of the exciting current of the power grid.

Preferably, the controller is further configured to control the three independent groups of switches to be opened simultaneously or to be opened independently.

Preferably, the controller is further configured to communicate with a plurality of energy conversion devices in each sub-array, the plurality of energy conversion devices controlling the three independent sets of switches to be simultaneously turned off when the off condition is met.

Preferably, the method further comprises: a power supply device;

and the power supply device is used for taking power from the power grid to supply power for the controller.

Preferably, the switch is a high voltage switch.

Preferably, the transformer is a step-up transformer.

Preferably, the input of the energy conversion device is used for connecting a direct current source or an alternating current.

Preferably, the energy conversion device is an inverter, and the direct current source includes at least one of a battery and a photovoltaic array.

From this, this application has following beneficial effect:

according to the technical scheme, when the power grid is three-phase, the breaking equipment comprises three groups of independent switches, and each phase of the three-phase power grid is connected with one group of switches in series; when the breaking equipment is closed, the three groups of independent switches are respectively and independently closed in sequence. When the power grid is input, in order to reduce the impact on a transformer and other medium-high voltage devices in the moment of the input of the power grid, the service life is prolonged, the transformer is required to be excited before the input of the power grid, the two ends of the breaking equipment are set up to have the same amplitude and the same phase with the power grid, then the voltage can be switched on, but the scheme of setting up the same amplitude and the same phase is complex, and the switch in the breaking equipment is only changed into three groups of independent switches to be separately and independently controlled, rather than the three groups of switches are used for being integrally linked, so that the impact on the transformer and other devices in the input of the power grid can be reduced, and the service life is prolonged.

Drawings

Fig. 1 is a schematic diagram of a grid-connected power generation system provided in an embodiment of the present application;

FIG. 2 is a schematic diagram of the switch of the present application;

fig. 3 is a schematic diagram of another grid-connected power generation system according to an embodiment of the present application.

Detailed Description

In order to make the above objects, features and advantages of the present application more comprehensible, embodiments accompanied with figures and detailed description are described in further detail below.

Referring to fig. 1, the diagram is a schematic diagram of a grid-connected power generation system provided in an embodiment of the present application.

The grid-connected power generation system provided in this embodiment includes: a breaking device 100 and a transformer T;

for example, the primary side of the transformer T is connected to a power source; the embodiment of the application is not particularly limited to the specific type of the power supply, and the power supply can be a direct current source or an alternating current source, and when the power supply is a direct current source, the power supply further comprises an energy conversion device for converting the direct current source into the alternating current source and providing the alternating current source as the primary side of the transformer. For example, may include a photovoltaic array, and may also include a photovoltaic array and an energy storage cell.

For example, the secondary side of the transformer T is connected to the power grid through the breaking device 100; the application is not particularly limited to the voltage class of the grid here, but may be medium-high voltage, for example, and in one possible implementation, the grid voltage may be 35kV. It should be appreciated that the grid voltage may be of other voltage levels.

When the voltage of the primary side connection of the transformer T is lower and the voltage of the power grid is higher, the transformer T is a step-up transformer.

The power grid is taken as a three-phase power grid as an example, so that the breaking equipment comprises three groups of independent switches, and each phase of the three-phase power grid is connected with one group of switches in series; it should be understood that each set of independent switches includes at least one switch, and may also include a plurality of switches connected in series, the plurality of switches connected in series acting together to function as a set of switches.

The breaking apparatus 100 includes three sets of switches inside, K1, K2 and K3, respectively. For example, K1, K2 and K3 are connected in series with the A, B and C three phases of the grid, respectively.

It should be understood that when the power grid is three-phase, the transformer T is also three-phase, and in fig. 1, only one line is substituted, and the three phases are reduced to one line.

The type of each group of switches is not particularly limited in this application, and may be, for example, a high-voltage switch or the like.

When the breaking apparatus 100 is closed, the three groups of independent switches are closed in sequence, i.e. the three groups of independent switches in the three phases are not closed at the same time. Reference is specifically made to fig. 2, which provides a schematic diagram of the switch when closed.

For example, phase A reaches the excitation current minimum point first, at which time K1 is closed; then the B phase reaches the minimum point of exciting current, at this time K2 is closed, and finally the C phase reaches the minimum point of exciting current, at this time K3 is closed. For example, the excitation current minimum point for each phase corresponds to the peak point of the phase voltage.

In order to control the closing of the switches more accurately, the closing delay time of the breaking device needs to be considered, for example, delta t is used for indicating the closing delay time actually, and then a switch closing signal needs to be issued at the time of advancing the voltage peak by delta t, so that the switch is closed at the voltage peak just after the delta t is delayed. It should be appreciated that delay times are considered for the switches of each of the three phases, i.e., switch closure signals are issued at times each prior to the peak point of each phase by Δt.

As shown in fig. 2, the A, B and C three-phase voltages are sequentially out of phase by 120 degrees.

The three independent switches can be closed at the peak point or can be closed at other moments in sequence, but when the peak point is closed, the corresponding exciting current impact is minimum, so that other devices of the transformer can be protected to the greatest extent.

When the medium-high voltage power grid is input, in order to reduce the impact of the power grid input moment on a transformer and other medium-high voltage devices, the service life is prolonged, the transformer is required to be excited before the power grid input, the secondary side of the transformer is built with the same amplitude and the same phase voltage with the power grid, then the transformer can be switched on, but the scheme of building the same amplitude and the same phase is complex, and the switch in the breaking equipment is only changed into three groups of independent switches to be separately and independently controlled, and the three groups of switches are not linked as a whole, so that the impact on the transformer and other devices during the power grid input can be reduced, and the service life is prolonged.

The following describes an example of application of the grid-connected power generation system provided in the embodiment of the present application to photovoltaic power generation. The present embodiment does not specifically limit the specific number of subarrays and the transformer, for example, the number of subarrays may be equal to the number of transformers, that is, in a one-to-one correspondence.

In addition, a plurality of subarrays may correspond to one transformer. The power supply includes: n subarrays; n is an integer greater than or equal to 1; each sub-array comprises at least one energy conversion device; the output end of each subarray is connected with the primary side of the corresponding transformer.

The specific type of energy conversion device is also not specifically defined herein, and the energy conversion device is an inverter depending on the type of power source to which the energy conversion device is input connected, e.g., the power source is a direct current source. The power source is an ac source, and the energy conversion device may be an ac-dc-ac conversion device or an ac-ac conversion device.

In the following, a transformer is used as a sub-array, that is, the number of the transformers is equal, and the energy conversion device is taken as an inverter for example.

Referring to fig. 3, a schematic diagram of another grid-connected power generation system according to an embodiment of the present application is shown.

In the grid-connected power generation system provided in this embodiment, the power supply includes: n subarrays; for example, a first subarray 201, a second subarray 202, etc.

Each sub-array includes a plurality of inverters; the number of inverters included in each subarray is not particularly limited, and may be set according to the capacity of the inverter and the capacity of each subarray.

Wherein, the number of the transformers is N; n is an integer greater than or equal to 1;

the N subarrays are in one-to-one correspondence with the N transformers, and the output end of each subarray is connected with the primary side of the corresponding transformer. That is, each subarray corresponds to one transformer, and the output end of each subarray is connected to the power grid through the corresponding transformer, for example, the output end of the first subarray 201 is connected to the primary side of the transformer T1, and the secondary side of the transformer T1 is connected to the power grid through the breaking device 100.

The input end of each inverter is connected with a corresponding photovoltaic array or a photovoltaic group string, the photovoltaic group string is not shown in the figure, in addition, the input end of each inverter can be connected with the photovoltaic group string, and the input end of each inverter is connected with a battery.

The embodiment provides a grid-connected power generation system, further including: a controller 200;

and the controller 200 is used for controlling the switch of the corresponding phase to be closed at the peak point of the power grid voltage, namely controlling the independent switches in the breaking equipment 100 to be sequentially closed.

In addition, the controller 100 is further configured to control the three groups of independent switches to be opened simultaneously or to be opened independently when the breaking apparatus 100 is opened. Since the breaking apparatus 100 is turned off without considering the impact of the exciting current of the transformer, all the switches in the breaking apparatus 100 can be controlled to be turned off at the same time; it should be understood that it is also possible to control the three sets of switches to be opened independently of each other.

According to the grid-connected power generation system, for photovoltaic power generation, under the condition of poor illumination conditions such as night or rainy days, the inverter can be in a standby state, if the transformer is always connected with a power grid, no-load loss can be generated, so that in order to reduce the no-load loss generated by the transformer, a switch in breaking equipment is required to be disconnected when the inverter is in standby. When the photovoltaic string connected with the inverter outputs electric energy, a switch in the breaking equipment is closed again.

Specifically, the controller 200 is further configured to communicate with a plurality of inverters in each subarray, where the plurality of inverters control three independent sets of switches to be simultaneously turned off when the turn-off condition is met, i.e. in order to reduce no-load loss. The off condition may be that the inverter is in a standby state due to low dc source voltage at the input end, or may be other operating conditions that the inverter needs maintenance and the like and needs to be turned off.

In addition, the grid-connected power generation system provided by the embodiment of the application further comprises: a power supply device 300;

the power supply device 300 is used for supplying power to the controller 200 by taking power from a power grid or taking power from the secondary side of the transformer. The embodiment of the present application is not particularly limited to the internal implementation form of the power supply device 300, and may include, for example, a transformer device or the like.

The individual transformers in fig. 3 may be step-up transformers for stepping up the output voltage of each sub-array to coincide with the grid voltage.

In addition, the grid-connected power generation system may be a photovoltaic system, an energy storage system or a light storage system, and the embodiment of the application is not particularly limited, and the power source may be a direct current source or an alternating current source, for example, when the power source is a direct current source, the power source may be a photovoltaic array, a battery or a combination of the photovoltaic array and the battery.

According to the grid-connected power generation system provided by the embodiment of the application, the current impact on devices such as a transformer and the like during grid connection can be reduced only by setting the switch in the breaking equipment as an independent switch, and other equipment in the system such as an inverter and the like is not required to be improved and upgraded.

It should be noted that, in the present description, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different manner from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.

The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present application. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other embodiments without departing from the spirit or scope of the application. Thus, the present application is not intended to be limited to the embodiments shown herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A grid-tie power generation system, comprising: breaking equipment and a transformer;

the transformer is connected with a power grid through the breaking equipment;

2. The system of claim 1, wherein the primary-side connected power supply of the transformer comprises: n subarrays;

each of the subarrays comprises a plurality of energy conversion devices;

the number of the transformers is N; the N is an integer greater than or equal to 1;

3. The system of claim 1, wherein the primary-side connected power supply of the transformer comprises: n subarrays; the N is an integer greater than or equal to 1; the subarrays correspond to the same transformer;

each of said sub-arrays comprising at least one energy conversion device;

4. A system according to claim 2 or 3, further comprising: a controller;

5. The system of claim 4, wherein the controller is further configured to control the three independent sets of switches to be opened simultaneously or separately.

6. The system of claim 5, wherein the controller is further configured to communicate with a plurality of energy conversion devices in each of the sub-arrays, the plurality of energy conversion devices controlling the three independent sets of switches to be simultaneously open when an open condition is met.

7. The system of claim 6, further comprising: a power supply device;

and the power supply device is used for taking power from a power grid to supply power for the controller.

8. The system of claim 6, wherein the switch is a high voltage switch.

9. The system of claim 6, wherein the transformer is a step-up transformer.

10. The system of claim 6, wherein the input of the energy conversion device is configured to be connected to a direct current source or an alternating current source.

11. The system of claim 10, wherein the energy conversion device is an inverter and the dc source comprises at least one of a battery and a photovoltaic array.