CN109842154B - Relay control method and device of grid-connected inverter - Google Patents
Relay control method and device of grid-connected inverter Download PDFInfo
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- CN109842154B CN109842154B CN201910123430.5A CN201910123430A CN109842154B CN 109842154 B CN109842154 B CN 109842154B CN 201910123430 A CN201910123430 A CN 201910123430A CN 109842154 B CN109842154 B CN 109842154B
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Abstract
According to the method and the device for controlling the relay of the grid-connected inverter, the relay is controlled to be closed and timing is started after the inversion voltage of the grid-connected inverter reaches a stable state. And in the time period when the timing duration does not reach the time threshold, if the actual value of the inverter current is detected to be greater than or equal to the current threshold, controlling the actual value of the inverter current to be reduced to be within a preset current range. When the timing duration is greater than or equal to the time threshold, the relays are considered to have completed closing actions, and at this time, the grid-connected inverter is controlled to stop operating in the current working mode, for example, the grid-connected inverter can be controlled to directly stop operating, or the grid-connected inverter is controlled to be directly switched to the normal grid-connected working mode from the current working mode. According to the method, the inverter current of the grid-connected inverter is directly controlled, so that the method is not influenced by the voltage quality of a power grid, and can inhibit the impact current in the process of closing the relay when the voltage quality of the power grid is poor.
Description
Technical Field
The invention belongs to the technical field of inversion, and particularly relates to a relay control method and device of a grid-connected inverter.
Background
The frequency and the phase of the alternating current voltage output by the grid-connected inverter are synchronous with the frequency and the phase of the power grid voltage, so that the alternating current output by the grid-connected inverter can be directly input into the power grid. The grid-connected inverter is connected to a power grid through a relay. Because the inverter side has filter capacitors, if the relay is directly closed, the filter capacitors are directly charged by the power grid through the relay, the impact current during charging is very large, and important devices of the inverter system can be damaged in serious cases.
The method for inhibiting the impulse current when the relay is closed in the prior art comprises the following two modes: one is to close the relay at the zero crossing point of the grid voltage; and the other is to close the relay when the output voltage of the grid-connected inverter is controlled to be consistent with the voltage of the power grid. The two modes can effectively inhibit the impact current generated when the relay is closed when the voltage quality of the power grid is good, but the impact current generated when the relay is closed is still very large when the distortion of the power grid is serious or the voltage harmonic of the power grid is large.
Disclosure of Invention
In view of the above, the present invention provides a method for controlling a relay of a grid-connected inverter to suppress an impulse current generated by closing the relay when a power grid is severely distorted or a voltage harmonic is large, and the technical scheme is as follows:
in a first aspect, the present invention provides a method for controlling a relay of a grid-connected inverter, including:
after the inversion voltage of the grid-connected inverter is controlled to reach a stable state, a relay connected with the grid-connected inverter is controlled to be closed, and timing is started;
when the timing duration does not reach a time threshold, if the fact that the actual value of the inverter current of the grid-connected inverter is larger than or equal to a first current threshold is detected, the actual value of the inverter current is controlled to be reduced to a preset current range;
and when the timing duration is greater than or equal to the time threshold, controlling the grid-connected inverter to stop operating in the current working mode.
Optionally, the controlling the actual value of the inverter current to be reduced to be within a preset current range includes:
setting the inverter current reference value of the grid-connected inverter as a numerical value within the preset current range;
and controlling the actual value of the inversion current of the grid-connected inverter to be reduced to the preset current range by utilizing a feedback control mode according to the reference value of the inversion current and the actual value of the inversion current.
Optionally, the controlling the actual value of the inverter current to be reduced to the preset current range further includes:
and when the actual value of the inverter current is detected to be within the preset current range, taking the reference value of the inverter current as the actual value of the inverter current.
Optionally, when the absolute value of the voltage difference between the inversion voltage of the grid-connected inverter and the grid voltage is smaller than a voltage threshold, it is determined that the inversion voltage reaches a stable state.
In a second aspect, the present invention further provides a method for controlling a relay of a grid-connected inverter, including:
after the inversion voltage of the grid-connected inverter is controlled to reach a stable state, a relay connected with the grid-connected inverter is controlled to be closed, and timing is started;
when the timing duration does not reach a time threshold, detecting whether the actual value of the inverter current of the grid-connected inverter is greater than or equal to a second current threshold;
and if the actual value of the inverter current is greater than or equal to a second current threshold value, or the timing duration is greater than or equal to the time threshold value, controlling the grid-connected inverter to stop operating in the current working mode.
In a third aspect, the present invention further provides a relay control device for a grid-connected inverter, including:
the first relay control module is used for controlling a relay connected with the grid-connected inverter to be closed and starting timing after the inversion voltage of the grid-connected inverter is controlled to reach a stable state;
the current control module is used for controlling the actual value of the inverter current to be reduced to a preset current range if the actual value of the inverter current of the grid-connected inverter is detected to be larger than or equal to a first current threshold when the timing duration does not reach the time threshold;
and the first stop control module is used for controlling the grid-connected inverter to stop running in the current working mode when the timing duration is greater than or equal to the time threshold.
Optionally, the current control module comprises:
the first reference value setting submodule is used for setting an inverter current reference value of the grid-connected inverter to a numerical value within the preset current range;
and the control submodule is used for controlling the actual value of the inversion current of the grid-connected inverter to be reduced to the preset current range by utilizing a feedback control mode according to the reference value of the inversion current and the actual value of the inversion current.
Optionally, the current control module further comprises:
and the second reference value setting submodule is used for taking the inverter current reference value as the inverter current actual value when the inverter current actual value is detected to be within the preset current range.
Optionally, the relay control device of the grid-connected inverter further includes: and the stable state determining module is used for determining that the inversion voltage reaches a stable state when the absolute value of the voltage difference between the inversion voltage of the grid-connected inverter and the grid voltage is less than a voltage threshold.
In a fourth aspect, the present invention provides another relay control device for a grid-connected inverter, including:
the second relay control module is used for controlling a relay connected with the grid-connected inverter to be closed and starting timing after the inversion voltage of the grid-connected inverter is controlled to reach a stable state;
the current detection module is used for detecting whether the actual value of the inverter current of the grid-connected inverter is greater than or equal to a second current threshold value or not when the timing duration does not reach the time threshold value;
and the second stop control module is used for controlling the grid-connected inverter to stop operating in the current working mode if the actual value of the inverter current is greater than or equal to a second current threshold value or the timing duration is greater than or equal to the time threshold value. According to the method for controlling the relay of the grid-connected inverter, after the inverter voltage of the grid-connected inverter reaches a stable state, the relay is controlled to be closed, and timing is started. And in the time period when the timing duration does not reach the time threshold, if the actual value of the inverter current is detected to be greater than or equal to the current threshold, controlling the actual value of the inverter current to be reduced to be within a preset current range. And when the timing duration is greater than or equal to the time threshold, the relays are considered to complete closing actions, and the grid-connected inverter is controlled to stop operating in the current working mode. According to the method, the inverter current of the grid-connected inverter is directly controlled, so that the method is not influenced by the voltage quality of a power grid, and can inhibit the impact current in the process of closing the relay when the voltage quality of the power grid is poor.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a control schematic diagram of a grid-connected inverter provided by an embodiment of the invention before grid-connected operation;
fig. 2 is a flowchart of a relay control method of a grid-connected inverter according to an embodiment of the present invention;
fig. 3 is a flowchart of another relay control method for a grid-connected inverter according to an embodiment of the present invention;
FIG. 4 is a graph illustrating inverter currents corresponding to the control method shown in FIG. 3;
fig. 5 is a flowchart of a relay control method of a grid-connected inverter according to another embodiment of the present invention;
FIG. 6 is a graph illustrating inverter currents corresponding to the control method of FIG. 5;
fig. 7 is a block diagram of a relay control device of a grid-connected inverter according to an embodiment of the present invention;
fig. 8 is a block diagram of another relay control device for a grid-connected inverter according to an embodiment of the present invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
Referring to fig. 1, a control schematic diagram of a grid-connected inverter provided by an embodiment of the present invention before grid-connected operation is shown, before a relay is closed, the grid-connected inverter adopts a voltage loop and current loop dual-loop control manner, and a grid voltage feedforward is added.
As shown in FIG. 1, the voltage loop inverts the voltage reference Vinv_refAs input, with the actual value V of the inverted voltageinv_realFor feedback, the output of the voltage loop is an inverter current reference value Iinv_ref。
Current loop with inverted current reference value Iinv_refAs input, with the actual value I of the inverter currentinv_realFor feedback, the output of the current loop is the inverse voltage regulation difference Vdelta。
Then, V is putdeltaAnd the network voltage Vgrid(Or, the inverted voltage reference value Vinv_ref) Control the grid-connected inverter after superposition, i.e. V can be utilizeddeltaAnd VgridThe voltage output from the grid-connected inverter is controlled by superposition, or V may be useddeltaAnd Vinv_refAnd controlling the voltage output by the grid-connected inverter in a superposition manner.
The inversion voltage reference value can be obtained by calculating a power grid phase lock and a power grid voltage effective value; in addition, in order to alleviate errors caused by sampling delay, the grid voltage sampling value and the grid voltage differential value can be synthesized to obtain the inverter voltage reference value. The closer the reference value of the inversion voltage is to the actual value of the grid voltage, the better, when the closed-loop control is carried out on the inversion voltage of the grid-connected inverter, the closer the inversion voltage output by the grid-connected inverter is to the grid voltage.
Referring to fig. 2, a flowchart of a relay control method provided by an embodiment of the present invention is shown, where the method may be applied to a single-phase or multi-phase (e.g., two-phase, three-phase, etc.) grid-connected inverter, as shown in fig. 2, and the method may include the following steps:
and S110, after the inverter voltage of the grid-connected inverter is controlled to reach a stable state, the relay is controlled to be closed, and timing is started.
Before the grid-connected inverter starts to operate, the relay is in a disconnected state; when the relay needs to be closed, the control loop shown in fig. 1 is firstly utilized to control the operation of the grid-connected inverter, before the relay is closed, the grid-connected inverter and the voltage of the power grid do not form a closed loop, and no inversion current can be generated, but inversion voltage exists, so that at the moment, the voltage loop normally operates, the inversion current reference value of the current loop is finally determined by the output of the voltage loop, and the actual value of the inversion voltage output by the control grid-connected inverter is close to the inversion voltage reference value.
When the actual value V of the inverted voltage isinv_realAnd the network voltage VgridThe absolute value of the voltage difference between the two is less than the voltage threshold VΔlimitWhen, i.e. | Vinv_ref-Vgrid|＜VΔlimitAnd determining that the inversion voltage of the grid-connected inverter reaches a stable state, and indicating that the inversion voltage output by the grid-connected inverter is basically consistent with the voltage of the power grid.
The voltage threshold can be set according to the control accuracy requirement, for example, the higher the control accuracy requirement is, the smaller the voltage threshold is; the lower the control accuracy requirement, the larger the voltage threshold.
And when the inversion voltage output by the grid-connected inverter is basically consistent with the voltage of the power grid, sending a control instruction for controlling a relay connected with the grid-connected inverter to be closed, and starting timing.
S120, judging whether the timing duration reaches a time threshold value; if not, S130 is performed, and if yes, S150 is performed.
After a control instruction for controlling the closing of the relay is sent out, whether the timing duration T reaches a time threshold T or not is judgedlimit。
Wherein, TlimitDetermination of response time in conjunction with various relays, TlimitShould be slightly larger than the maximum response time, i.e. TlimitThe setting of (2) needs to ensure that all relays receiving the control instruction are finished under the normal conditionTo a closing action. E.g. TlimitCan be set in the range of 10ms to 50 ms.
S130, detecting whether the actual value of the inverter current of the grid-connected inverter is larger than or equal to a first current threshold value, and if so, executing S140; if not, returning to execute S120;
when the timing time length does not reach TlimitDetecting the actual value I of the inversion current of the grid-connected inverterinv_realWhether or not it is greater than or equal to the first current threshold Ilimit1Wherein, Ilimit1Less than the over-current protection value. By detecting whether the inverter current is greater than or equal to Ilimit1Can assist in determining whether the relay has completed a closing action.
And S140, controlling the actual value of the inverter current of the grid-connected inverter to be reduced to a preset current range.
Wherein the predetermined current range is [ -I ]limit2，Ilimit2]Wherein, Ilimit2＜Ilimit1。
In the application scene of the multiphase grid-connected inverter, if the inverter current is detected to be greater than or equal to Ilimit1Indicating that the at least two-phase relay has completed a closing action, forming at least one closed loop. However, at this time, it is not possible to determine whether all the multi-phase relays have completed the closing operation, and therefore, the grid-connected inverter cannot be directly controlled to stop the current working mode, but the inverter current of the grid-connected inverter is reduced to be within the preset current range. Specifically, the inverter current in the circuit is controlled within a preset current range by the current loop shown in fig. 1.
In the application scene of the single-phase grid-connected inverter, if the detected inversion current is larger than or equal to Ilimit1Indicating that the relay has completed a closing action, forming a closed loop in which current is generated. At this time, the inverter current of the grid-connected inverter is controlled to be reduced to the preset current range, the control process is the same as that in the three-phase application scene, and the description is omitted here.
I in application scene of single-phase grid-connected inverterlimit1Application scenario of multi-phase grid-connected inverterlimit1Is different in valueAnd the setting is required according to the actual application requirement.
After the execution of S140, the process returns to the execution of S120 to determine whether the time duration reaches the time threshold again.
And S150, controlling the grid-connected inverter to stop operating in the current working mode.
And executing S150 when the timing duration reaches the time threshold.
When the timing time length reaches TlimitThen, no matter the multi-phase grid-connected inverter or the single-phase grid-connected inverter, all the relays in the circuit are considered to have completed the closing action, at this time, the grid-connected inverter is controlled not to operate in the current working mode any more, wherein the current working mode refers to the working mode in which the grid-connected inverter is located in the relay closing process, for example, in such a working mode, the grid-connected inverter operates according to the control mode of the voltage loop and the current loop shown in fig. 1; for example, in one possible embodiment, the grid-connected inverter may be directly controlled to stop working; in another possible embodiment, the grid-tied inverter is switched from the current operating mode to the normal grid-tied operating mode.
According to the method for controlling the relay of the grid-connected inverter, after the inverter voltage of the grid-connected inverter reaches a stable state, the relay is controlled to be closed, and timing is started. And in the time period when the timing duration does not reach the time threshold, if the actual value of the inverter current is detected to be greater than or equal to the current threshold, controlling the actual value of the inverter current to be reduced to be within a preset current range. And when the timing duration is greater than or equal to the time threshold, the relays are considered to complete closing actions, and the grid-connected inverter is controlled to stop operating in the current working mode. The method directly controls the inverter current of the grid-connected inverter, so that the method is not influenced by the voltage quality of the power grid, and can inhibit the impact current in the process of closing the relay when the voltage quality of the power grid is poor.
Referring to fig. 3, a flowchart of another relay control method for a grid-connected inverter according to an embodiment of the present invention is shown, and the method will focus on a control process for controlling an actual value of an inverter current to decrease to a preset current range.
As shown in fig. 3, the method comprises the steps of:
and S210, after the inverter voltage of the grid-connected inverter is controlled to reach a stable state, the relay is controlled to be closed, and timing is started.
S220, judging whether the timing duration reaches a time threshold value; if not, S230 is performed, and if yes, S270 is performed.
S230, detecting whether the actual value of the inverter current of the grid-connected inverter is greater than or equal to a first current threshold value, and if so, executing S240; if not, returning to execute S220;
the implementation processes of S210 to S230 are the same as the implementation processes of S110 to S130, and are not described herein again.
And S240, setting the inverter current reference value of the grid-connected inverter to a numerical value within a preset current range.
When the timing time length does not reach TlimitWhen I is detectedinv_real≥Ilimit1Then the inversion current reference value I is setinv_refThe value is set to a fixed value within a preset range, preferably 0.
And S250, controlling the actual value of the inverter current to be reduced to the preset current range by using a feedback control mode according to the reference value of the inverter current and the actual value of the inverter current.
Then, I of the grid-connected inverter is controlled by using the current loop shown in FIG. 1inv_realTrend to Iinv_refAnd the change is carried out, so that the impact current generated in the closing process of the relay is avoided.
And S260, when the actual value of the inverter current is detected to be within the preset current range, feeding back the inverter current reference value serving as the actual value of the inverter current to the current loop.
When I isinv_realAfter the current is within the preset current range, the I does not need to be controlled continuouslyinv_realTo reach and Iinv_refAn equal level; and, if the control I is continuedinv_realBringing it to Iinv_refMay cause Vinv_realLarge variations occur, which in turn lead to inrush currents in the circuit. Therefore, V can be adjusted at this timeinv_realAssigned a value of Iinv_refI.e. this time of controlThe current loop is no longer active in the process.
Wherein, the change curve of the inversion current is shown in FIG. 4 when Iinv_realTo achieve Ilimit1Then quickly reducing to the preset current range [ -I [ ]limit2，Ilimit2]And (4) the following steps.
After the execution of S260, the process returns to the execution of S220 to re-determine whether the timed duration reaches the time threshold, and after the timed duration reaches the time threshold, the process executes S270.
And S270, controlling the grid-connected inverter to stop operating in the current working mode.
And when the timing duration reaches a time threshold, all relays in the circuit are considered to be closed, and the grid-connected inverter is controlled to stop operating in the current working mode.
According to the relay control method of the grid-connected inverter, after the fact that the inverter current is larger than the first current threshold value is detected, the inverter current reference value is directly set in the preset current range, the current loop is used for controlling the inverter current actual value to tend to the preset current range to change, the inverter current actual value is finally controlled in the preset current range until the timing duration reaches the time threshold value, and the grid-connected inverter is controlled to stop operating in the current working mode. According to the method, the inverter current of the grid-connected inverter is directly controlled, so that the method is not influenced by the voltage quality of a power grid, and can inhibit the impact current in the process of closing the relay when the voltage quality of the power grid is poor.
Referring to fig. 5, a flowchart of a relay control method for a grid-connected inverter according to another embodiment of the present invention is shown, where the method provided in this embodiment is suitable for a single-phase grid-connected inverter. As shown in fig. 5, the method may include the steps of:
and S310, after the inversion voltage of the grid-connected inverter is controlled to reach a stable state, a relay connected with the grid-connected inverter is controlled to be closed, and timing is started.
S320, judging whether the timing duration reaches a time threshold value; if not, S330 is performed, and if yes, S340 is performed.
The implementation process of S310 and S320 is the same as that of S110 and S120, and is not described herein again.
S330, detecting whether the actual value of the inverter current of the grid-connected inverter is greater than or equal to a second current threshold value; if so, go to S340; if not, return to execute S320.
Second current threshold Ilimit3Much smaller than the over-current protection value.
And S340, controlling the grid-connected inverter to stop operating in the current working mode.
When the actual value I of the inverter current of the grid-connected inverterinv_real≥Ilimit3When the single-phase inverter is started, the relay is determined to complete the closing action of all relays in the circuit where the single-phase inverter is located, so that a closed loop is formed, and therefore, larger current can appear in the circuit. And at the moment, controlling the grid-connected inverter to stop operating in the current working mode.
If the actual value of the inverter current does not reach the current threshold value all the time, after the timing duration reaches the time threshold value, the relays in the circuit are all considered to complete the closing action, and therefore the grid-connected inverter is controlled to stop operating in the current working mode.
The grid-connected inverter stopping operating in the current working mode may include: and controlling the grid-connected inverter to switch to a normal grid-connected working mode, or directly stopping running.
For the case of controlling the grid-connected inverter to directly stop operating, the change curve of the inverter current is as shown in fig. 6 when I isinv_realTo achieve Ilimit3Then, it rapidly decreases to 0.
According to the method for controlling the relay of the grid-connected inverter, after the inverter voltage of the grid-connected inverter reaches a stable state, the relay is controlled to be closed, and timing is started. And in the time period that the timing duration does not reach the time threshold, if the fact that the actual value of the inverter current is greater than or equal to the current threshold is detected, or after the timing duration is greater than or equal to the time threshold, the relays are all considered to complete the closing action, and at the moment, the grid-connected inverter is controlled to stop operating in the current working mode. The method directly controls the inverter current of the grid-connected inverter, so that the method is not influenced by the voltage quality of the power grid, and can inhibit the impact current in the process of closing the relay when the voltage quality of the power grid is poor.
Corresponding to the embodiment of the relay control method of the grid-connected inverter, the invention also provides an embodiment of a relay control device of the grid-connected inverter.
Referring to fig. 7, a block diagram of a relay control apparatus for a grid-connected inverter according to an embodiment of the present invention is shown, where the apparatus is applied to a single-phase or multi-phase grid-connected inverter, and as shown in fig. 7, the apparatus includes a first relay control module 110, a current control module 120, and a first stop control module 130.
And the first relay control module 110 is configured to control a relay connected to the grid-connected inverter to be closed and start timing after controlling the inverter voltage of the grid-connected inverter to reach a stable state.
The method includes the steps that whether the inversion voltage of the grid-connected inverter reaches a stable state or not can be detected through a stable state determination module, and specifically, when the absolute value of the voltage difference between the inversion voltage of the grid-connected inverter and the grid voltage is smaller than a voltage threshold value, it is determined that the inversion voltage reaches the stable state. For example, when inverting the actual value V of the voltageinv_realAnd the network voltage VgridThe absolute value of the voltage difference between the two is less than the voltage threshold VΔlimitWhen, i.e. | Vinv_ref-Vgrid|＜VΔlimitAnd then, determining that the inversion voltage of the grid-connected inverter reaches a stable state.
Before the grid-connected inverter starts to operate, the relay is in a disconnected state; and when the inversion voltage reaches a stable state, the relay is controlled to be closed, and timing is started.
And the current control module 120 is configured to, when the timing duration does not reach the time threshold, control the actual value of the inverter current to be reduced to a preset current range if it is detected that the actual value of the inverter current of the grid-connected inverter is greater than or equal to the first current threshold.
Wherein the time threshold value TlimitDetermination of response time in conjunction with various relays, TlimitShould be slightly larger than the maximum response time, i.e. TlimitThe setting of (2) needs to ensure that all relays receiving the control instruction are closed under the normal conditionAnd (5) performing a closing action. E.g. TlimitCan be set in the range of 10ms to 50 ms.
In the application scenario of the single-phase grid-connected inverter, if the timing duration does not reach the time threshold, the actual value of the inverter current (namely, the inverter current) is detected to be greater than or equal to Ilimit1Indicating that the relay has completed a closing action, forming a closed loop in which a current is generated. At the moment, the inverter current of the grid-connected inverter is controlled to be reduced to be within a preset current range.
In the application scene of the multiphase grid-connected inverter, if the timing duration does not reach the time threshold, the inverter current is detected to be greater than or equal to Ilimit1Indicating that the at least two-phase relay has completed a closing action, forming at least one closed loop. However, at this time, it is not possible to determine whether all the multi-phase relays have completed the closing operation, and therefore, the grid-connected inverter cannot be directly controlled to stop the current working mode, but the inverter current of the grid-connected inverter is reduced to be within the preset current range.
In one embodiment of the present invention, the current control module 120 includes a first reference value setting sub-module and a control sub-module.
The first reference value setting submodule is used for setting an inverter current reference value of the grid-connected inverter to a numerical value within a preset current range.
When the timing time length does not reach TlimitWhen I is detectedinv_real≥Ilimit1Then the inversion current reference value I is setinv_refThe value is set to a fixed value within a preset range, preferably 0.
The control submodule is used for controlling the actual value of the inversion current of the grid-connected inverter to be reduced to the preset current range by utilizing a feedback control mode according to the reference value of the inversion current and the actual value of the inversion current.
The control submodule controls the actual value I of the inversion current of the grid-connected inverter by using the current loop shown in FIG. 1inv_realTrend inversion current reference value Iinv_refAnd the change is carried out, so that the impact current generated in the closing process of the relay is avoided.
Optionally, the current control module further includes a second reference setting sub-module on the basis of the first reference value setting sub-module and the control sub-module.
And the second reference value setting submodule is used for taking the inverter current reference value as the inverter current actual value when the inverter current actual value is detected to be within the preset current range.
When I isinv_realAfter the current is within the preset current range, the I does not need to be controlled continuouslyinv_realTo reach and Iinv_refAn equal level; and, if the control I is continuedinv_realBringing it to Iinv_refMay cause Vinv_realLarge variations occur, which in turn lead to inrush currents in the circuit. Therefore, V can be adjusted at this timeinv_realAssigned a value of Iinv_refI.e. the current loop is no longer active during this control.
The first stop control module 130 is configured to control the grid-connected inverter to stop operating in the current working mode when the timing duration is greater than or equal to the time threshold.
When the timing time length reaches TlimitAnd then, whether the grid-connected inverter is a multi-phase grid-connected inverter or a single-phase grid-connected inverter, all relays in the circuit are considered to complete closing actions, and at the moment, the grid-connected inverter is controlled not to operate in the current working mode.
The relay control device for the grid-connected inverter provided in this embodiment controls the relay to close and starts timing after the inverter voltage of the grid-connected inverter reaches a stable state. And in the time period when the timing duration does not reach the time threshold, if the actual value of the inverter current is detected to be greater than or equal to the current threshold, controlling the actual value of the inverter current to be reduced to be within a preset current range. And when the timing duration is greater than or equal to the time threshold, the relays are considered to complete closing actions, and the grid-connected inverter is controlled to stop operating in the current working mode. The device directly controls the inverter current of the grid-connected inverter, so that the device is not influenced by the voltage quality of a power grid, and can inhibit the impact current in the process of closing the relay when the voltage quality of the power grid is poor.
Referring to fig. 8, a block diagram of another relay control device for a grid-connected inverter according to an embodiment of the present invention is shown, where the device is applied to a single-phase grid-connected inverter. As shown in fig. 8, the apparatus includes: a second relay control module 210, a current detection module 220, and a second stop control module 230.
And the second relay control module 210 is configured to control a relay connected to the grid-connected inverter to be closed and start timing after controlling the inverter voltage of the grid-connected inverter to reach a stable state.
And the current detection module 220 is configured to detect whether the actual value of the inverter current of the grid-connected inverter is greater than or equal to a second current threshold value when the timing duration does not reach the time threshold value.
Second current threshold Ilimit3Much smaller than the over-current protection value.
And the second stop control module 230 is configured to control the grid-connected inverter to stop operating in the current working mode if the actual value of the inverter current is greater than or equal to the second current threshold, or the timing duration is greater than or equal to the time threshold.
When the actual value I of the inverter current of the grid-connected inverterinv_real≥Ilimit3When the single-phase inverter is started, the relay is determined to complete the closing action of all relays in the circuit where the single-phase inverter is located, so that a closed loop is formed, and therefore, larger current can appear in the circuit. And at the moment, controlling the grid-connected inverter to stop operating in the current working mode.
If the actual value of the inverter current does not reach the current threshold value all the time, after the timing duration reaches the time threshold value, the relays in the circuit are all considered to complete the closing action, and therefore the grid-connected inverter is controlled to stop operating in the current working mode.
The grid-connected inverter stopping operating in the current working mode may include: and controlling the grid-connected inverter to switch to a normal grid-connected working mode, or directly stopping running.
In the relay control device for the grid-connected inverter provided by the embodiment, after the inverter voltage of the grid-connected inverter reaches a stable state, the relay is controlled to be closed, and timing is started. And in the time period that the timing duration does not reach the time threshold, if the fact that the actual value of the inverter current is greater than or equal to the current threshold is detected, or after the timing duration is greater than or equal to the time threshold, the relays are all considered to complete the closing action, and at the moment, the grid-connected inverter is controlled to stop operating in the current working mode. The device directly controls the inverter current of the grid-connected inverter, so that the device is not influenced by the voltage quality of a power grid, and can inhibit the impact current in the process of closing the relay when the voltage quality of the power grid is poor.
While, for purposes of simplicity of explanation, the foregoing method embodiments have been described as a series of acts or combination of acts, it will be appreciated by those skilled in the art that the present invention is not limited by the illustrated ordering of acts, as some steps may occur in other orders or concurrently with other steps in accordance with the invention. Further, those skilled in the art should also appreciate that the embodiments described in the specification are preferred embodiments and that the acts and modules referred to are not necessarily required by the invention.
It should be noted that, in the present specification, the embodiments are all 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 device-like embodiment, since it is basically similar to the method embodiment, the description is simple, and for the relevant points, reference may be made to the partial description of the method embodiment.
The steps in the method of each embodiment of the invention can be sequentially adjusted, combined and deleted according to actual needs.
The device and the modules and sub-modules in the terminal in the embodiments of the present invention can be combined, divided and deleted according to actual needs.
In the embodiments provided in the present invention, it should be understood that the disclosed terminal, apparatus and method may be implemented in other ways. For example, the above-described terminal embodiments are merely illustrative, and for example, the division of a module or a sub-module is only one logical division, and there may be other divisions when the terminal is actually implemented, for example, a plurality of sub-modules or modules may be combined or integrated into another module, or some features may be omitted or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or modules, and may be in an electrical, mechanical or other form.
The modules or sub-modules described as separate parts may or may not be physically separate, and parts that are modules or sub-modules may or may not be physical modules or sub-modules, may be located in one place, or may be distributed over a plurality of network modules or sub-modules. Some or all of the modules or sub-modules can be selected according to actual needs to achieve the purpose of the solution of the present embodiment.
In addition, each functional module or sub-module in each embodiment of the present invention may be integrated into one processing module, or each module or sub-module may exist alone physically, or two or more modules or sub-modules may be integrated into one module. The integrated modules or sub-modules may be implemented in the form of hardware, or may be implemented in the form of software functional modules or sub-modules.
Finally, it should also be noted that, herein, relational terms such as first and second, and the like may be used solely to distinguish one entity or action from another entity or action without necessarily requiring or implying any actual such relationship or order between such entities or actions. Also, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising an … …" does not exclude the presence of other identical elements in a process, method, article, or apparatus that comprises the element.
The previous description of the disclosed embodiments is provided to enable any person skilled in the art to make or use the present invention. 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 invention. Thus, the present invention 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.
The foregoing is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, various modifications and decorations can be made without departing from the principle of the present invention, and these modifications and decorations should also be regarded as the protection scope of the present invention.
Claims (8)
1. A relay control method of a grid-connected inverter is characterized by comprising the following steps:
after the inversion voltage of the grid-connected inverter is controlled to reach a stable state, a relay connected with the grid-connected inverter is controlled to be closed, and timing is started;
when the timing duration does not reach a time threshold, if the fact that the actual value of the inversion current of the grid-connected inverter is larger than or equal to a first current threshold is detected, the grid-connected inverter is controlled to maintain a current working mode, and the actual value of the inversion current is controlled to be reduced to a preset current range by a current control loop; wherein the time threshold is determined by a response time of the relay;
and when the timing duration is greater than or equal to the time threshold, controlling the grid-connected inverter to stop running.
2. The method according to claim 1, wherein the controlling the inverter current actual value to decrease to be within a preset current range comprises:
setting the inverter current reference value of the grid-connected inverter as a numerical value within the preset current range;
and controlling the actual value of the inversion current of the grid-connected inverter to be reduced to the preset current range by utilizing a feedback control mode according to the reference value of the inversion current and the actual value of the inversion current.
3. The method of claim 2, wherein the controlling the inverter current actual value to decrease to be within a preset current range further comprises:
and when the actual value of the inverter current is detected to be within the preset current range, taking the reference value of the inverter current as the actual value of the inverter current.
4. The method according to claim 1, wherein it is determined that the inverted voltage of the grid-connected inverter reaches a steady state when an absolute value of a voltage difference between the inverted voltage and a grid voltage is less than a voltage threshold.
5. A relay control device for a grid-connected inverter, comprising:
the first relay control module is used for controlling a relay connected with the grid-connected inverter to be closed and starting timing after the inversion voltage of the grid-connected inverter is controlled to reach a stable state;
the current control module is used for controlling the grid-connected inverter to maintain the current working mode and controlling the actual value of the inversion current to be reduced to a preset current range by using a current control loop if the actual value of the inversion current of the grid-connected inverter is detected to be greater than or equal to a first current threshold when the timing duration does not reach the time threshold; wherein the time threshold is determined by a response time of the relay;
and the first stop control module is used for controlling the grid-connected inverter to stop running in the current working mode when the timing duration is greater than or equal to the time threshold.
6. The apparatus of claim 5, wherein the current control module comprises:
the first reference value setting submodule is used for setting an inverter current reference value of the grid-connected inverter to a numerical value within the preset current range;
and the control submodule is used for controlling the actual value of the inversion current of the grid-connected inverter to be reduced to the preset current range by utilizing a feedback control mode according to the reference value of the inversion current and the actual value of the inversion current.
7. The apparatus of claim 6, wherein the current control module further comprises:
and the second reference value setting submodule is used for taking the inverter current reference value as the inverter current actual value when the inverter current actual value is detected to be within the preset current range.
8. The apparatus of claim 5, further comprising: and the stable state determining module is used for determining that the inversion voltage reaches a stable state when the absolute value of the voltage difference between the inversion voltage of the grid-connected inverter and the grid voltage is less than a voltage threshold.
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| CN113315401B (en) * | 2021-06-03 | 2022-03-29 | 昱能科技股份有限公司 | Micro inverter and grid-connected output control method and device thereof |
| CN113533954B (en) * | 2021-07-26 | 2024-04-12 | 爱士惟新能源技术(扬中)有限公司 | Method and control system for detecting relay closing time of energy storage inverter |
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