CN115800360A - Grid-connected power generation system and switching-on method - Google Patents
Grid-connected power generation system and switching-on method Download PDFInfo
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Abstract
The application discloses grid-connected power generation system and a switching-on method, wherein the system comprises: breaking equipment, a subarray and a transformer; when a plurality of sub-arrays are provided, each sub-array corresponds to one transformer, or a plurality of sub-arrays correspond to one transformer; each subarray including at least one energy conversion device; the output end of each subarray is connected with the primary side of a corresponding transformer, and the secondary side of the transformer is connected with a power grid through corresponding breaking equipment; before the breaking equipment is closed, the primary side of an excited transformer in the transformer is excited by an external power supply or a corresponding energy conversion device. The technical scheme can excite the transformer under the condition of insufficient input power, so that the transformer can complete excitation starting.
Description
Technical Field
The application relates to the technical field of new energy, in particular to a grid-connected power generation system and a switching-on method.
Background
At present, a photovoltaic power station or a grid-connected power generation system comprises a plurality of sub-arrays, each sub-array comprises a plurality of inverters, the output ends of the inverters of each sub-array are converged and then subjected to voltage transformation through corresponding sub-array transformers, and the transformed energy is fed to a power grid. The grid is typically a medium to high voltage grid.
Generally, a switch-off switch is arranged between a transformer and a power grid, and the connection relationship between the transformer and the power grid is controlled through the switch-off switch. Before the power grid is put into operation, in order to reduce the impact of the power grid on the transformer and other devices at the moment of the power grid input and prolong the service life of the devices, the transformer needs to be excited before the opening switch is closed, and then the opening switch is closed.
However, for a grid-connected power generation system with a plurality of transformers connected in parallel, if the transformers are excited under the condition that the input power is insufficient, the technical problem needs to be solved.
Disclosure of Invention
In view of this, the present application provides a grid-connected power generation system and a closing method, which can support excitation starting of a transformer.
The application provides a grid-connected power generation system, includes: breaking equipment, a subarray and a transformer;
each subarray including at least one energy conversion device;
the output end of each subarray is connected with the primary side of a corresponding transformer, and the secondary sides of the transformers are connected with a power grid through corresponding breaking equipment;
before the breaking equipment is closed, the primary side of an excited transformer in the transformer is excited by an external power supply or a corresponding energy conversion device.
Preferably, the input end of the corresponding energy conversion device or devices of the excited transformer is connected with an external power supply;
the external power supply is a direct current source or an alternating current source;
and the energy conversion device is used for adjusting the frequency and the phase of the output voltage according to the frequency and the phase of the power grid.
Preferably, the method further comprises the following steps: an external energy conversion device;
the input end of the external energy conversion device is connected with an external power supply, the output end of the external energy conversion device is connected with the primary side of the excited transformer, the external energy conversion device is used for exciting the excited transformer through the external power supply, and the external power supply is disconnected with the excited transformer after excitation is finished;
the external power supply is a direct current source or an alternating current source;
and the external energy conversion device is used for adjusting the frequency and the phase of the output voltage according to the frequency and the phase of the power grid.
Preferably, the method further comprises the following steps: a voltage regulating device;
the first end of the voltage regulating device is connected with an external power supply, and the second end of the voltage regulating device is connected with the primary side of the excited transformer; the voltage regulating equipment is used for exciting the excited transformer through an external power supply, and the external power supply is disconnected with the excited transformer after excitation is finished;
the external power source is first alternating current, and the voltage level of the first alternating current is lower than that of a power grid.
Preferably, the voltage regulating device is specifically configured to gradually increase the amplitude of the output voltage according to a preset amplitude gradient or gradually regulate the phase of the output voltage according to a preset phase gradient from zero voltage until the output voltage of the excited transformer has the same amplitude and the same phase as the voltage of the power grid.
Preferably, the method further comprises the following steps: a voltage transformation device;
the first end of the transformation device is connected with an external power supply, and the second end of the transformation device is connected with the primary side of the excited transformer; the transformation equipment is used for exciting the excited transformer through an external power supply, and the external power supply is disconnected from the excited transformer after excitation is finished;
the external power source is a power grid.
Preferably, the method further comprises the following steps: a voltage transformation device;
the first end of the transformation device is connected with an external power supply, and the second end of the transformation device is connected with the secondary side of the excited transformer; the transformation equipment is used for exciting the excited transformer through an external power supply, and the external power supply is disconnected from the excited transformer after excitation is finished;
the external power source is a power grid.
Preferably, the breaking apparatus comprises a breaking switch and a controller;
the opening switch is connected between the secondary side of the transformer and the power grid;
and the controller is used for obtaining the voltage amplitude and the phase of the power grid, and controlling the opening switch to be closed when the secondary side of the excited transformer outputs the voltage with the same amplitude and the same phase according to the voltage amplitude and the phase of the power grid.
Preferably, the controller is in communication connection with a plurality of energy conversion devices in each subarray and controls the breaking device to be disconnected when all the energy conversion devices meet the breaking condition.
Preferably, the transformer is a step-up transformer;
when the primary side of the excited transformer is excited by an external power supply, the external power supply is also used for supporting the breaking equipment to be closed, so that the energy conversion device on the primary side of the transformer performs reactive power compensation on a power grid.
Preferably, the energy conversion device of each subarray is an inverter, and an input end of the inverter is used for connecting a direct current source.
The application also provides a switching-on method of the grid-connected power generation system, and the grid-connected power generation system comprises the following steps: breaking equipment, a subarray and a transformer; each subarray including at least one energy conversion device; the output end of each subarray is connected with the primary side of a corresponding transformer, and the secondary sides of all the transformers are connected with a power grid through breaking equipment;
the method comprises the following steps:
before the breaking equipment is closed, controlling the primary side of an excited transformer in the N transformers to be connected with an external power supply, and exciting by the external power supply;
or, controlling the energy conversion device corresponding to the excited transformer to carry out excitation;
the excited transformer is one or more of N transformers.
Preferably, the method further comprises the following steps: and obtaining the voltage amplitude and the phase of the power grid, and controlling the breaking equipment to be closed when the secondary side of the excited transformer outputs the voltage with the same amplitude and the same phase according to the voltage amplitude and the phase of the power grid.
Preferably, the method further comprises the following steps: and when judging that all the energy conversion devices meet the breaking conditions, controlling the breaking equipment to be disconnected.
Therefore, the application has the following beneficial effects:
the technical scheme provided by the application aims to solve the problem that the transformer needs to be excited in advance before the breaking equipment is closed in order to solve the impact on the transformer and other devices before the breaking equipment is closed, an external power supply can be used for providing excitation energy for the transformer, and the transformer can also be excited through an inverter in a sub-array. After the excited transformer is excited, the connection between the external power supply and the transformer can be disconnected. The technical scheme can excite the transformer under the condition of insufficient input power, so that the transformer can complete excitation starting.
Drawings
Fig. 1 is a schematic diagram of a grid-connected power generation system according to an embodiment of the present disclosure;
fig. 2 is a schematic diagram of another grid-connected power generation system provided in an embodiment of the present application;
fig. 3 is a schematic diagram of another grid-connected power generation system provided in the embodiment of the present application;
fig. 4 is a schematic diagram of another grid-connected power generation system provided in an embodiment of the present application;
fig. 5 is a schematic diagram of another grid-connected power generation system provided in the embodiment of the present application;
fig. 6 is a schematic diagram of another grid-connected power generation system according to an embodiment of the present disclosure.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present application more comprehensible, embodiments accompanying the drawings are described in detail below.
Referring to fig. 1, the figure is a schematic diagram of a grid-connected power generation system according to an embodiment of the present application.
The application provides a grid-connected power generation system includes: breaking equipment, a subarray and a transformer; when a plurality of sub-arrays are provided, each sub-array corresponds to one transformer, or a plurality of sub-arrays correspond to one transformer; each subarray including at least one energy conversion device;
the output end of each subarray is connected with the primary side of a corresponding transformer, and the secondary sides of the transformers are connected with a power grid through corresponding breaking equipment; before the breaking equipment is closed, the primary side of an excited transformer in the transformer is excited by an external power supply or a corresponding energy conversion device.
The number of the breaking devices is not particularly limited in the embodiment of the application, and the breaking devices can be one or multiple, that is, when one breaking device is used, the secondary sides of all transformers are connected with the power grid through the same breaking device. When there are a plurality of breaking devices, a plurality of transformers may correspond to one breaking device, and one transformer may also correspond to one breaking device.
The present embodiment does not specifically limit the specific number of the sub-arrays and the transformers, for example, the number of the sub-arrays may be equal to the number of the transformers, i.e., a one-to-one correspondence relationship.
In addition, a plurality of sub-arrays may correspond to one transformer. The power supply includes: n sub-arrays; n is an integer greater than or equal to 1; each subarray including at least one energy conversion device; the output end of each sub-array is connected with the primary side of the corresponding transformer.
The present application also does not specifically limit the specific type of energy conversion device, depending on the type of power source to which the input of the energy conversion device is connected, e.g., if the power source is a dc source, then the energy conversion device is an inverter. If the power source is an ac source, the energy conversion device may be an ac-dc-ac conversion device or an ac-ac conversion device.
In the following, a sub-array corresponding to a transformer, that is, the number of the sub-array and the transformer are equal, and the energy conversion device is taken as an inverter as an example. The input end of the inverter can be connected with various direct current sources, is not limited to a photovoltaic module, and can also be a battery and the like. The grid-connected power generation system provided by the embodiment comprises: n subarrays, N transformers and a breaking device 100; n is an integer of 1 or more, that is, one or more subarrays may be provided. The number of the sub-arrays is the same as that of the transformers, and the sub-arrays correspond to the transformers one by one, namely, one sub-array is correspondingly connected with one transformer. Fig. 1 only illustrates two sub-arrays and two transformers, that is, the output end of the first sub-array 10 is connected to the primary side of the first transformer T1, and the secondary side of the first transformer T1 is connected to the grid through the breaking device 100. The output end of the second sub-array 20 is connected to the primary side of the second transformer T2, and the secondary side of the second transformer T2 is connected to the grid through the breaking device 100.
The input end of each subarray is connected with the photovoltaic array or the photovoltaic group string, each subarray can comprise a plurality of inverters, and the output ends of the plurality of inverters can be connected in parallel and connected with the primary side of the transformer together.
The secondary side of the transformer T is connected with the power grid through the breaking equipment 100; the voltage class of the power grid is not specifically limited herein, and for example, the voltage class may be medium-high voltage, and in one possible implementation, the voltage of the power grid may be 35kV. It should be understood that the grid voltage may also be other voltage levels.
When the voltage connected to the primary side of the transformer T is low and the grid voltage is high, the transformer may be a step-up transformer.
Under the condition of poor illumination conditions such as night or rainy days, the inverter of the grid-connected power generation system is in a standby state, and if the transformer is always connected with a power grid, the transformer generates no-load loss.
In order to solve the problem of no-load loss, the controller 200 may control the breaking apparatus 100 to be disconnected, so as to disconnect the secondary side of the transformer from the power grid, reduce the no-load loss of the transformer, and improve the overall efficiency of the system.
In addition, the grid-connected power generation system provided by the embodiment of the application may further include a power taking device 300, which is used for taking power from a power grid to supply power to the controller 200. The embodiment of the present application does not specifically limit the specific implementation form of the power taking device 300, and for example, the power taking device may include a transformer circuit and a rectifier circuit, so as to convert the ac power of the power grid into a power source that can be used by the controller 200.
In order to solve the problem that the transformer is required to be excited in advance before the breaking device 100 is closed in order to solve the impact on the transformer before the breaking device 100 is closed, several excitation implementation manners are introduced below.
The embodiments of the present application are not particularly limited, the number of the transformers to be excited may be one or multiple, and for convenience of description, the transformers to be excited are collectively referred to as excited transformers hereinafter.
Before the breaking equipment is closed, the primary side of an excited transformer in the N transformers is excited by an external power supply or is excited by off-grid starting of a corresponding inverter, and the excited transformer is one or more transformers in the N transformers.
Several specific excitation modes are respectively described below with reference to the accompanying drawings.
Referring to fig. 2, the figure is a schematic diagram of another grid-connected power generation system provided in the embodiment of the present application.
In the grid-connected power generation system provided by this embodiment, the input end of one or more inverters corresponding to the excited transformer is connected to the external power supply 400;
in the present embodiment, power electronic conversion is performed by using an inverter already existing in the grid-connected power generation system, and the energy of the external power supply 400 is supplied to the primary side of the excited transformer T.
The specific source of the external power source is not specifically limited in the embodiments of the present application, for example, the external power source 400 is an energy storage battery or a rectified power source. The inverter 21 may convert direct current supplied from the external power source 400 into alternating current.
In order to match the voltage frequency and the phase of the power grid, the inverter 21 is used for adjusting the frequency and the phase of the output voltage according to the frequency and the phase of the power grid to perform off-grid slow start, so that the frequency and the phase of the primary side voltage of the excited transformer T are consistent with the power grid, and when the excited transformer T changes the voltage into the secondary side voltage through transformation ratio and is consistent with the amplitude of the power grid voltage, namely when the voltage amplitude and the phase at two ends of the breaking equipment meet the synchronous condition, the breaking equipment is closed and connected to the power grid, namely the breaking equipment is closed.
The voltage amplitude and the phase position meet the synchronization condition means that the difference value of the voltage amplitude values at two ends of the breaking equipment is within a preset amplitude value range, the difference value of the voltage phase positions at two ends is within a preset phase position range, namely a certain error range is allowed, and as long as the difference value is within the range, the voltage amplitude values and the phase positions are adjusted in place by default, and the breaking equipment can be closed. For example, the preset amplitude range is 1% of rated voltage, and the rated voltage refers to the rated voltage of the power grid; for example, the preset phase range is 5 °, the above is only an example, and the specific value can be set according to actual needs.
It will be appreciated that the inverter 21 of the sub-array connected to the external power supply operates in off-grid mode, with the remaining inverters standing by and not operating.
The number of external power sources 400 is not limited, the number of inverters 21 is not limited, and the number of excited transformers T is not limited.
The inverter 21 may be connected to the photovoltaic string PV in addition to the external power source 400.
While the input terminals of the other inverters are connected to the photovoltaic string PV, the number of photovoltaic strings PV connected to the input terminal of each inverter is not specifically limited in the embodiment of the present application, and is only illustrated in fig. 2, and the number of photovoltaic strings is not limited.
In the grid-connected power generation system provided by the embodiment, the no-load loss of the transformer is provided by the external power supply, the external power supply is used for exciting the transformer before the breaking equipment is closed, and the existing inverter in the sub-array is used as the power electronic equipment. In addition, when the excitation of the transformer is successful and the breaking device is closed, the external power supply can be cut off, namely, the connection between the external power supply and the inverter is disconnected.
The inverter in the sub-array is used as the power electronic device, and an external energy conversion device is externally connected as the power electronic device. When the power source is a dc source, the external energy conversion device is an energy storage converter.
Referring to fig. 3, the figure is a schematic diagram of another grid-connected power generation system provided in the embodiment of the present application.
The grid-connected power generation equipment provided by the embodiment further comprises: an energy storage converter PCS;
the input end of the energy storage converter PCS is connected with an external power supply, the output end of the energy storage converter PCS is connected with the primary side of the excited transformer, the energy storage converter PCS is used for exciting the excited transformer through the external power supply, and the output end of the energy storage converter PCS is disconnected with the primary side of the excited transformer after excitation is finished;
the external power supply is an energy storage battery or a rectification power supply;
and the energy storage converter PCS is used for adjusting the frequency and the phase of the output voltage according to the frequency and the phase of the power grid.
The difference between the present embodiment and fig. 2 is that in fig. 2, the existing inverter of the subarray is used to convert the electric energy into the excitation transformer, the energy storage converter PCS is used as the excitation transformer in the present embodiment, and the external power source 400 may be a battery or a rectified power source. Similar to the inverter, the energy storage converter PCS also needs to control the frequency and phase of the output voltage according to the voltage frequency and phase of the power grid, so that the frequency and phase of the primary voltage of the excited transformer T are consistent with the power grid, and when the excited transformer T changes the voltage into the secondary voltage through transformation ratio, the secondary voltage is consistent with the amplitude of the power grid voltage, that is, when the amplitude and phase of the voltage at two ends of the breaking device satisfy the synchronization condition, the breaking device is closed and connected to the power grid, that is, the energy storage converter PCS is connected to the power grid.
In addition, when the excitation of the excited transformer is successful and the breaking device is closed, the external power supply can be cut off, namely, the connection between the external power supply and the inverter is disconnected.
According to the grid-connected power generation system provided by the embodiment, before the breaking equipment is switched on, electricity is taken from an external power supply by the PCS to be excited by the exciting transformer, so that no-load loss of the transformer is supported, and too large current impact on the transformer and medium-high voltage devices when the breaking equipment is switched on is avoided.
The above embodiment describes the case where the external power supply is a dc power supply, and the case where the external power supply is an ac power supply, which may be supplied to the excited transformer through voltage regulation or phase modulation, is described below. The alternating current power supply can be low-voltage alternating current for plant use or third-party alternating current or directly from a power grid.
Referring to fig. 4, the figure is a schematic diagram of another grid-connected power generation system provided in the embodiment of the present application.
The grid-connected power generation system provided by this embodiment further includes: a voltage regulating device Ta;
the embodiment of the application does not specifically limit the specific implementation form of the voltage regulating device Ta, and the voltage regulating device Ta can be a power electronic device, such as a thyristor voltage regulator or a thyristor converter, and can regulate voltage and phase.
A first end of the voltage regulating device Ta is connected to the external power supply 400, and a second end of the voltage regulating device Ta is connected to a primary side of an excited transformer T1 (only T1 is taken as an example); the voltage regulating device Ta excites the excited transformer T1 through the external power supply 400, and after excitation is finished, the external power supply is disconnected from the excited transformer T1;
the external power source 400 is a first alternating current having a voltage level lower than that of the grid. For example, the first alternating current is plant alternating current or a third party power supply. For example, the service power is 400V.
Fig. 4 only illustrates three transformers, one of which is an excited transformer, and the embodiment does not specifically limit the specific number of transformers, and may be set according to the number of sub-arrays.
Since the phase of the external power source may be different from that of the excited transformer, the circuit breaker QF in the breaking apparatus 100 is controlled to be closed only when the voltage regulating apparatus Ta is required to regulate the phase of the alternating current supplied from the external power source to be consistent with the potential of the power grid. In the present embodiment, the example in which the breaking apparatus 100 includes a circuit breaker is described.
In addition, in order to further avoid current impact, the voltage and the phase position can be adjusted step by step without being adjusted in place at one time.
The voltage regulating device of the grid-connected power generation system provided by this embodiment is specifically configured to gradually increase the amplitude of the output voltage according to a preset amplitude gradient or gradually regulate the phase of the output voltage according to a preset phase gradient from zero voltage until the output voltage of the excited transformer and the voltage of the power grid have the same amplitude and the same phase.
In addition, the pressure regulating device provided by the embodiment of the application can also be regulated according to different amplitude gradients, namely, the amplitude step length of each regulation can be unequal. Similarly, the phase step of each adjustment may be different, that is, the voltage amplitude and/or phase are adjusted in variable steps.
The external power supply can be directly obtained from the power grid besides the auxiliary power supply or the third-party power supply. The following description is made with reference to the accompanying drawings.
Referring to fig. 5, the figure is a schematic diagram of another grid-connected power generation system provided in the embodiment of the present application.
The grid-connected power generation system provided by the embodiment further comprises: a voltage transformation device Ts;
since the external power supply of this embodiment is derived from the power grid, it is not necessary to adjust the phase and the frequency, and only the voltage amplitude is adjusted to the voltage required by the primary side of the excited transformer T1.
The transforming device Ts may be implemented by a voltage regulating device, such as a transformer.
The first end of the transformation device Ts is connected with an external power supply, and the second end of the transformation device Ts is connected with the primary side of the excited transformer T1; the transformation equipment Ts is used for exciting the excited transformer T1 through an external power supply, and the second end of the transformation equipment Ts is disconnected with the primary side of the excited transformer T1 after the excitation is finished;
the external power supply is a Grid.
The transformation device Ts can be connected with the power grid through the switch QFs, and after the excitation of the excited transformer T1 is finished, the QFs can be disconnected, so that the excited transformer T1 is disconnected from the power grid.
According to the grid-connected power generation system provided by the embodiment, an external power supply is not required to be added, electricity is directly taken from a power grid to excite the excited transformer, the current impact when the breaking equipment is closed is reduced, and the transformer and other medium-high voltage devices are protected.
The above-described transforming device is connected to the primary side of the excited transformer, and in addition, the transforming device may also be connected to the secondary side of the excited transformer, that is, the grid-connected power generation system further includes: a voltage transformation device;
the first end of the transformation device is connected with an external power supply, and the second end of the transformation device is connected with the secondary side of the excited transformer; the transformation equipment is used for exciting the excited transformer through an external power supply, and the external power supply is disconnected from the excited transformer after excitation is finished; the external power source is a power grid.
In the grid-connected power generation system provided by this embodiment, the breaking device 100 includes a breaking switch and a controller; the opening switch can be realized by a high-voltage switch QF.
The opening switch is connected between the secondary side of the transformer and the power grid;
and the controller is used for obtaining the voltage amplitude and the phase of the power grid, and controlling the opening switch to be closed when the secondary side of the excited transformer outputs the voltage with the same amplitude and the same phase according to the voltage amplitude and the phase of the power grid.
In addition, the controller can be in communication connection with the plurality of inverters in each sub-array and controls the breaking equipment to be disconnected when all the inverters meet the breaking condition. I.e. the controller needs to communicate with the breaking device. The breaking condition can be that the inverter is in a standby state due to low direct-current source voltage of the input end, and can also be other working conditions needing to be disconnected, such as the condition that the inverter needs to be maintained.
The above embodiments describe the excitation of the excited transformer by using an external power source, and the following describes the excitation of the excited transformer by directly performing off-grid starting through the inverter in the subarray without using the external power source.
Referring to fig. 6, the figure is a schematic diagram of another grid-connected power generation system provided in the embodiment of the present application.
The grid-connected power generation system according to the present embodiment excites an excited transformer using an existing inverter in a sub-array.
For example, the inverters in one or more sub-arrays meeting the starting condition can be selected to operate in an off-grid slow-start state in an off-grid black-start mode, and the output voltage is adjusted according to the frequency and the phase of the grid voltage until the closing condition of the transformer is met, and the present embodiment supports the no-load loss of the transformer by means of the output power of a plurality of inverters. When the breaking equipment is closed, each inverter can be switched to a grid-connected mode to operate.
In this embodiment, the number of inverters to be started in an off-grid mode is not specifically limited, for example, the inverters in the N sub-arrays are all started in an off-grid mode, that is, the first array 10, the second sub-array 20, and up to the nth sub-array N0 correspond to the excitation transformers T1, T2, and up to Tn, respectively. It should be understood that off-grid starting can also be performed on part of inverters of one or more sub-arrays, in order to excite part of transformers, since the secondary sides of the transformers are connected with the breaking equipment, the impact caused by closing of the breaking equipment can also be reduced when part of the transformers are excited.
Because in order to reduce the no-load loss of the inverter during standby at night, the breaking equipment is disconnected, but after the breaking equipment is disconnected, if the power grid needs to perform reactive compensation at night, the reactive compensation at night cannot be realized, because the breaking equipment needs to be controlled to be closed when voltages at two ends reach the same frequency and the same phase with the same amplitude. However, according to the system provided by the embodiment of the application, when the excited transformer is excited by an external power supply, the voltages at the two ends of the breaking equipment can meet the conditions of same amplitude, same frequency and same phase through the external power supply, and then the breaking equipment can be closed at night, so that the requirement of reactive power compensation of a power grid at night is met. Based on the grid-connected power generation system provided by the above embodiment, the application also provides a switching-on method of the grid-connected power generation system, which is described in detail below.
In the switching method of the grid-connected power generation system provided by this embodiment, the grid-connected power generation system includes: breaking equipment, a subarray and a transformer; each subarray including at least one energy conversion device; the output end of each subarray is connected with the primary side of a corresponding transformer, and the secondary sides of all the transformers are connected with a power grid through breaking equipment;
the method comprises the following steps:
before the breaking equipment is closed, the primary side of an excited transformer in the control transformer is connected with an external power supply, and the external power supply is used for excitation;
or controlling an inverter corresponding to the excited transformer to carry out off-grid starting to carry out excitation;
when the number of the transformers is multiple, the excited transformer is one transformer or a plurality of transformers in the N transformers.
The method provided by the embodiment further comprises the following steps: and obtaining the voltage amplitude and the phase of the power grid, and controlling the breaking equipment to be closed when the secondary side of the excited transformer outputs the voltage with the same amplitude and the same phase according to the voltage amplitude and the phase of the power grid.
The method provided by the embodiment further comprises the following steps: and when all the inverters meet the breaking conditions, controlling the breaking equipment to be disconnected. The breaking condition can be that the inverter is in a standby state due to low direct-current power voltage of the input end, and can also be other working conditions needing to be disconnected, such as the need of maintenance of the inverter.
The technical scheme provided by the application aims to solve the problem that the transformer needs to be excited in advance before the breaking equipment is closed in order to solve the impact on the transformer and other devices before the breaking equipment is closed, an external power supply can be used for providing excitation energy for the transformer, and the transformer can also be excited by adopting off-grid starting through an inverter in a sub-array. After the excited transformer is excited, the connection between the external power supply and the transformer can be disconnected.
It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the system or the device disclosed by the embodiment, the description is simple because the system or the device corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
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 (14)
1. A grid-connected power generation system, comprising: breaking equipment, a subarray and a transformer;
each of the sub-arrays comprises at least one energy conversion device;
the output end of each subarray is connected with the primary side of the corresponding transformer, and the secondary side of the transformer is connected with a power grid through the corresponding breaking equipment;
before the breaking equipment is closed, the primary side of an excited transformer in the transformer is excited by an external power supply or a corresponding energy conversion device.
2. The system of claim 1, wherein the input terminals of the corresponding one or more energy conversion devices of the excited transformer are connected to the external power supply;
the external power supply is a direct current source or an alternating current source;
and the energy conversion device is used for adjusting the frequency and the phase of the output voltage according to the frequency and the phase of the power grid.
3. The system of claim 1, further comprising: an external energy conversion device;
the input end of the external energy conversion device is connected with the external power supply, the output end of the external energy conversion device is connected with the primary side of the excited transformer, the external energy conversion device excites the excited transformer through the external power supply, and the external power supply is disconnected from the excited transformer after excitation is finished;
the external power supply is a direct current source or an alternating current source;
and the external energy conversion device is used for adjusting the frequency and the phase of the output voltage according to the frequency and the phase of the power grid.
4. The system of claim 1, further comprising: a voltage regulating device;
the first end of the voltage regulating device is connected with the external power supply, and the second end of the voltage regulating device is connected with the primary side of the excited transformer; the voltage regulating equipment excites the excited transformer through the external power supply, and the connection between the external power supply and the excited transformer is disconnected after excitation is finished;
the external power source is first alternating current, and the voltage level of the first alternating current is lower than that of the power grid.
5. The system according to claim 4, wherein the voltage regulation device is configured to gradually increase the amplitude of the output voltage according to a predetermined amplitude gradient or gradually adjust the phase of the output voltage according to a predetermined phase gradient starting from zero voltage until the output voltage of the excited transformer is in phase with the voltage of the power grid.
6. The system of claim 1, further comprising: a voltage transformation device;
the first end of the transformation device is connected with the external power supply, and the second end of the transformation device is connected with the primary side of the excited transformer; the transformation equipment excites the excited transformer through the external power supply, and the connection between the external power supply and the excited transformer is disconnected after excitation is finished;
the external power source is the power grid.
7. The system of claim 1, further comprising: a voltage transformation device;
the first end of the transformation device is connected with the external power supply, and the second end of the transformation device is connected with the secondary side of the excited transformer; the transformation equipment excites the excited transformer through the external power supply, and the connection between the external power supply and the excited transformer is disconnected after excitation is finished;
the external power source is the power grid.
8. The system according to any of claims 1-7, wherein the breaking device comprises a breaking switch and a controller;
the opening switch is connected between the secondary side of the transformer and the power grid;
the controller is used for obtaining the voltage amplitude and the phase of the power grid, and controlling the opening switch to be closed when the secondary side of the excited transformer outputs the voltage with the same amplitude and the same phase according to the voltage amplitude and the phase of the power grid.
9. The system according to any one of claims 1 to 8, wherein the controller is communicatively connected to a plurality of energy conversion devices in each of the sub-arrays, and controls the breaking apparatus to break when all of the energy conversion devices meet a breaking condition.
10. The system of any one of claims 1-9, wherein the transformer is a step-up transformer;
when the primary side of the excited transformer is excited by the external power supply, the external power supply is also used for supporting the breaking equipment to be closed, so that the energy conversion device on the primary side of the transformer performs reactive compensation on a power grid.
11. The system according to any one of claims 1-9, wherein the energy conversion device of each said sub-array is an inverter, the input of said inverter being adapted to be connected to a dc source.
12. A switching-on method of a grid-connected power generation system is characterized in that the grid-connected power generation system comprises the following steps: breaking equipment, a subarray and a transformer; each subarray comprises at least one energy conversion device; the output end of each subarray is connected with the corresponding primary side of the transformer, and the secondary side of the transformer is connected with a power grid through the corresponding breaking equipment;
the method comprises the following steps:
before the breaking equipment is closed, controlling the primary side of an excited transformer in the N transformers to be connected with an external power supply, and exciting by the external power supply;
or, controlling the energy conversion device corresponding to the excited transformer to carry out excitation;
the excited transformer is one or more transformers in the N transformers.
13. The method of claim 12, further comprising: and obtaining the voltage amplitude and the phase of the power grid, and controlling the breaking equipment to be closed when the secondary side of the excited transformer outputs the voltage with the same amplitude and the same phase according to the voltage amplitude and the phase of the power grid.
14. The method of claim 12 or 13, further comprising: and when judging that all the energy conversion devices meet the breaking conditions, controlling the breaking equipment to be disconnected.
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| CN202211418957.9A CN115800360A (en) | 2022-11-14 | 2022-11-14 | Grid-connected power generation system and switching-on method |
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| CN202211418957.9A CN115800360A (en) | 2022-11-14 | 2022-11-14 | Grid-connected power generation system and switching-on method |
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