CN116632926B - Phase-locked grid-connected method based on communication - Google Patents
Phase-locked grid-connected method based on communication Download PDFInfo
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- CN116632926B CN116632926B CN202310911496.7A CN202310911496A CN116632926B CN 116632926 B CN116632926 B CN 116632926B CN 202310911496 A CN202310911496 A CN 202310911496A CN 116632926 B CN116632926 B CN 116632926B
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
- H02J3/40—Synchronising a generator for connection to a network or to another generator
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J13/00—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network
- H02J13/00006—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment
- H02J13/00016—Circuit arrangements for providing remote indication of network conditions, e.g. an instantaneous record of the open or closed condition of each circuitbreaker in the network; Circuit arrangements for providing remote control of switching means in a power distribution network, e.g. switching in and out of current consumers by using a pulse code signal carried by the network characterised by information or instructions transport means between the monitoring, controlling or managing units and monitored, controlled or operated power network element or electrical equipment using a wired telecommunication network or a data transmission bus
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Abstract
The invention relates to the technical field of photovoltaic energy storage and off-grid control, in particular to a phase-locked grid-connected method based on communication, which comprises the following steps: s1: carrying out phase locking operation on a power grid and the inverter through an external off-grid conversion device of the inverter to obtain power grid voltage phase information and inverter voltage phase information; s2: the obtained power grid voltage phase information and the inverter voltage phase information are transmitted back to the inverter through communication; s3: the inverter substitutes the deviation value of the power grid voltage phase information and the inversion voltage phase information into a phase delay synchronization algorithm so that the inversion voltage phase and the power grid voltage phase are synchronized; s4: after executing S3, the phase-locking operation information is acquired through the off-grid conversion device again. The method solves the problem of communication delay of a communication scheme by using an algorithm, and ensures that the inverter can complete synchronization of the inverter voltage to the voltage phase of the power grid after the phase information is acquired by communication.
Description
Technical Field
The invention relates to the technical field of photovoltaic energy storage and off-grid control, in particular to a phase-locked grid-connected method based on communication.
Background
The current scheme of separating the inverter from the parallel-to-off-grid device is that the phase locking part of the power grid is basically completed by the inverter.
In the prior art, the China patent application number is 201811393783.9 and the off-grid switching device comprises a grid-connected bus, an off-grid bus and a plurality of double-switching switches; the first contact of the double-cut switch is connected with the grid-connected bus, the second contact of the double-cut switch is connected with the off-grid bus, the connector of the double-cut switch is connected with different equipment in the micro-grid, and the connector can be switched between the first contact and the second contact; and the grid-connected bus is connected with a large power grid. After the parallel-to-off network switching device is used, the parallel-to-off network state of each device of the micro-grid is determined by each double-switching switch; when the double-cut switch is switched to the first contact, the equipment is connected to a large power grid through a grid-connected bus, and enters a grid-connected state; when the double-cut switch is switched to the second contact, the equipment is connected with the off-grid bus to enter an off-grid state, so that the flexibility of the micro-grid is greatly improved, and the stability and the safety of the micro-grid system are ensured.
The technology can also realize the separation of the inverter and the off-grid device. However, the power grid sampling signal is transmitted back to the inverter for processing through the signal line, and the power grid phase locking operation is not directly carried out by adopting the off-grid conversion device.
The disadvantage of this solution is that the grid signal is transmitted over long distance signal lines, which are highly likely to be disturbed, thus affecting the inverter operation control.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and provides a phase-locking grid-connection method based on communication, which realizes the phase-locking grid-connection control method based on communication and completes phase-locking operation on grid information through an external off-grid conversion device. The communication delay problem of the communication scheme is innovatively solved by using an algorithm, so that the inverter can complete synchronization of the inverter voltage to the power grid voltage phase after the phase information is acquired through communication, and the scheme can effectively isolate the influence of the sampling signal line interference on the phase-locked operation in the traditional scheme.
In order to solve the technical problems, the invention adopts the following technical scheme: a phase-locked grid-connected method based on communication comprises the following steps:
s1: carrying out phase locking operation on a power grid and the inverter through an external off-grid conversion device of the inverter to obtain power grid voltage phase information and inverter voltage phase information;
s2: the obtained power grid voltage phase information and the inverter voltage phase information are transmitted back to the inverter through communication;
s3: the inverter substitutes the deviation value of the power grid voltage phase information and the inversion voltage phase information into a phase delay synchronization algorithm to adjust the inversion voltage output phase, so that the inversion voltage phase and the power grid voltage phase are synchronous;
s4: and after S3 is executed, the phase-locked operation information is acquired through the off-grid conversion device again, whether the inverter voltage phase information and the grid voltage phase information are synchronous or not is judged, if so, the inverter performs communication and issues a closing command to the off-grid conversion device, and the off-grid conversion device closes the grid-connected relay to complete grid connection of the inverter.
Further, in S4, if it is determined that the synchronization is not performed, the process returns to S3 to continue the synchronization operation.
Further, the phase-locked operation method comprises the following steps: acquiring power grid voltage phase information and inverter voltage phase information by adopting a biquad generalized integrator single-phase-locked loop principle;
the inversion voltage is subjected to second-order generalized integrator to generate two orthogonal signals alpha and beta, then Park conversion is carried out to obtain vd and vq, wherein the phase value required by Park conversion is the phase value output by a phase-locked loop, vq is sent to a PI regulator, the output of the PI regulator can obtain the value of instantaneous angular frequency, and then the angular frequency is integrated to obtain a phase value theta 1;
the power grid voltage is subjected to second-order generalized integrator to generate two orthogonal signals alpha and beta, then Park conversion is carried out to obtain vd and vq, wherein the phase value required by Park conversion is the phase value output by a phase-locked loop, vq is sent to a PI regulator, the output of the PI regulator can obtain the value of instantaneous angular frequency, and then the angular frequency is integrated to obtain the phase value theta 2.
Further, the method for judging synchronization comprises the following steps:
when the deviation value of the power grid voltage phase information and the inverter voltage phase information is smaller than or equal to a preset threshold value, the synchronization of the power grid voltage phase information and the inverter voltage phase information can be judged;
when the deviation value of the power grid voltage phase information and the inverter voltage phase information is larger than a set threshold value, the fact that the power grid alternating current voltage phase information value and the inverter voltage phase information value are not synchronous can be judged.
Further, the deviation value is substituted into a phase delay synchronization algorithm to adjust the output phase of the inverter voltage, so that the inverter voltage and the grid voltage are in phase synchronization, and the method comprises the following steps: and adding the communication delay link into a closed-loop control algorithm for controlling the transfer function, thereby inhibiting the disturbance of the delay link.
Further, the communication is any one of 485 communication, CAN communication and serial communication.
Compared with the prior art, the invention has the beneficial effects that: the invention realizes the phase-locking grid-connected control method based on communication, and completes phase-locking operation on the power grid information through an external off-grid conversion device. The communication delay problem of the communication scheme is innovatively solved by using an algorithm, so that the inverter can complete synchronization of the inverter voltage to the power grid voltage phase after the phase information is acquired through communication, and the scheme can effectively isolate the influence of the sampling signal line interference on the phase-locked operation in the traditional scheme. Meanwhile, the calculation force can be balanced, and the influence on the control accuracy caused by overlarge calculation force load of the main controller is avoided.
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The disclosure of the present invention is described with reference to the accompanying drawings. It is to be understood that the drawings are designed solely for the purposes of illustration and not as a definition of the limits of the invention. In the drawings, like reference numerals are used to refer to like parts. Wherein:
FIG. 1 schematically shows a schematic flow diagram of an overall apparatus according to an embodiment of the present invention;
fig. 2 schematically shows a schematic diagram of a matching structure of an off-grid device, an inverter and a power grid according to an embodiment of the present invention;
fig. 3 schematically shows a formulation of the principle of a biquad generalized integrator single phase locked loop.
Detailed Description
It is to be understood that, according to the technical solution of the present invention, those skilled in the art may propose various alternative structural modes and implementation modes without changing the true spirit of the present invention. Accordingly, the following detailed description and drawings are merely illustrative of the invention and are not intended to be exhaustive or to limit the invention to the precise form disclosed.
Embodiment one:
as shown in fig. 1 and 2, the inverter and the off-grid device are separated from each other in the market, and the phase locking part of the power grid is basically completed. The power grid sampling signal is transmitted back to the inverter for processing through the signal line, and the power grid phase locking operation is not directly carried out by adopting the off-grid conversion device. The disadvantage of this solution is that the grid signal is transmitted over long distance signal lines, which may be disturbed, thereby affecting the inverter operation control. In order to overcome these problems, the following technical means are devised.
The parallel-to-off network conversion device is independent from the photovoltaic energy storage inverter to form an independent device outside the inverter, and the parallel-to-off network conversion device and the inverter are controlled in a communication mode, wherein the communication mode comprises any one of 485 communication, CAN communication, serial communication and the like. The external off-grid conversion device comprises a grid-connected relay and is used for establishing or disconnecting a connection with a power grid.
The external off-grid conversion device is provided with a control unit, the control unit acquires power grid voltage phase information of a power grid and inverter voltage phase information of an inverter by adopting a biquad generalized integrator single-phase-locked loop principle, and the phase information is a phase angle value. The power grid and the inverter are both alternating current, and the phase synchronization is synchronous. A specific method is as using the formula of fig. 3; the method comprises the steps of generating two orthogonal signals alpha and beta through a second-order generalized integrator, obtaining vd and vq through Park conversion, wherein the phase value required by Park conversion is the phase value output by a phase-locked loop, sending vq to a PI regulator, obtaining an instantaneous angular frequency value through output of the PI regulator, obtaining a phase value theta 1 through diagonal frequency integration, generating two orthogonal signals alpha and beta through the second-order generalized integrator by grid voltage, obtaining vd and vq through Park conversion, wherein the phase value required by Park conversion is the phase value output by the phase-locked loop, sending vq to the PI regulator, obtaining the instantaneous angular frequency value through output of the PI regulator, and obtaining the phase value theta 2 through diagonal frequency integration.
Substituting the deviation value of the obtained inverter voltage phase value theta 1 and the power grid voltage phase value theta 2 into a closed-loop control algorithm for controlling the transfer function, namelyWherein->For the controlled device->Is proportional gain->Action for integration->For integral gain +.>For differential gain +.>Is a differential action. The phase value of the power grid voltage is a target value, so that the phase value of the automatic control inverter voltage is close to the phase value of the power grid voltage. When the deviation value of the phase value of the inverter voltage and the phase value of the grid voltage is smaller than or equal to a preset threshold value, the phase value of the inverter voltage and the phase value of the grid voltage can be judged to be in a synchronous state. When the deviation value of the phase value of the inverter voltage and the phase value of the grid voltage is larger than a preset threshold value, the phase value of the inverter voltage and the phase value of the grid voltage can be judged to be in an asynchronous state. In order to enable whether the phase value of the inverter voltage and the phase value of the power grid voltage are synchronous or not to be judged stably and accurately, a communication delay link is added in a closed-loop control algorithm for controlling the transfer function, and interference of the communication delay on the control algorithm is eliminated through the communication delay link before operation of the closed-loop control algorithm for controlling the transfer function.
After correcting a closed-loop control algorithm of a control transfer function, performing phase locking operation through a parallel-to-off network conversion device, obtaining an inversion voltage phase value and a power grid voltage phase value, judging whether the deviation value of the inversion voltage phase value and the power grid voltage phase value is smaller than or equal to a preset deviation value at the moment, if the deviation value is smaller than or equal to the preset deviation value, judging that the inverter voltage phase information and the power grid voltage phase information are synchronous at the moment, and closing a grid-connected relay through the parallel-to-off network conversion device at the moment so that the inverter and the power grid are connected; and when the deviation value is larger than a preset deviation value, judging that the inverter voltage phase information and the grid voltage phase information are not synchronous at the moment, and continuously substituting the new deviation value into the closed-loop control algorithm of the control transfer function containing the communication delay link at the moment to perform re-synchronization operation. And after the synchronization operation is finished, calculating an inverter voltage phase value and a power grid voltage phase value according to the phase locking operation of the grid-connected/disconnected conversion device, calculating an offset value, judging whether the offset value is smaller than or equal to a preset threshold value, and judging that the inverter voltage phase information and the power grid voltage phase information are synchronous if the offset value is smaller than or equal to the preset threshold value. If the judgment result is larger than the preset threshold value, continuing to repeat the actions.
Embodiment two: adding a technical means for judging whether the inverter works normally or not;
after the synchronous operation, the phase locking operation of the parallel-to-off network conversion device is performed again, the inverter voltage phase value and the power grid voltage phase value are calculated, then the deviation value is calculated, whether the deviation value is smaller than or equal to a preset threshold value is judged, and if the deviation value is smaller than or equal to the preset threshold value, the synchronization of the inverter voltage phase information and the power grid voltage phase information is judged. If the judgment result is larger than the preset threshold value, continuing to repeat the actions. And after the actions are repeated for a preset time, judging that the voltage phase value of the inverter cannot be synchronized with the voltage phase value of the power grid, and carrying out alarm operation. And judging that the inverter cannot normally operate.
The other methods of this embodiment are the same as those of the first embodiment.
Compared with the traditional signal line in the way, the signal deviation caused by signal interference is relatively more accurate. However, communication has communication delay, and the device adopts a closed-loop control algorithm for adding a communication delay link to a control transfer function, so that disturbance of the delay link can be restrained. The integral design can well overcome the interference problem caused by the traditional signal line. The method transfers the phase-locking operation to the off-grid switching device, so that the calculation load force of the inverter is relatively reduced, and each module can operate more accurately and stably.
The technical scope of the present invention is not limited to the above description, and those skilled in the art may make various changes and modifications to the above-described embodiments without departing from the technical spirit of the present invention, and these changes and modifications should be included in the scope of the present invention.
Claims (3)
1. A phase-locked grid-connected method based on communication is characterized by comprising the following steps:
s1: carrying out phase locking operation on a power grid and the inverter through an external off-grid conversion device of the inverter to obtain power grid voltage phase information and inverter voltage phase information;
s2: the obtained power grid voltage phase information and the inverter voltage phase information are transmitted back to the inverter through communication;
s3: the inverter substitutes the deviation value of the power grid voltage phase information and the inversion voltage phase information into a phase delay synchronization algorithm to adjust the inversion voltage output phase, so that the inversion voltage phase and the power grid voltage phase are synchronous;
s4: after S3 is executed, phase-locked operation information is obtained through the off-grid conversion device again, whether the inverter voltage phase information and the grid voltage phase information are synchronous or not is judged, if the synchronization is judged, the inverter communicates and issues a closing command to the off-grid conversion device, the off-grid conversion device closes a grid-connected relay, and grid connection of the inverter is completed;
the external off-grid conversion device is provided with a control unit, the control unit acquires power grid voltage phase information of a power grid and inverter voltage phase information of an inverter by adopting a biquad generalized integrator single-phase-locked loop principle, and the phase information is a phase angle value; the power grid and the inverter are both alternating current, and the phase synchronization is synchronous; generating two orthogonal signals alpha and beta by an inversion voltage through a second-order generalized integrator, then obtaining vd and vq through Park conversion, wherein the phase value required by Park conversion is the phase value output by a phase-locked loop, sending vq to a PI regulator, obtaining an instantaneous angular frequency value by the output of the PI regulator, obtaining a phase value theta 1 through diagonal frequency integration, generating two orthogonal signals alpha and beta by a grid voltage through the second-order generalized integrator, obtaining vd and vq through Park conversion, wherein the phase value required by Park conversion is the phase value output by the phase-locked loop, sending vq to the PI regulator, obtaining the instantaneous angular frequency value by the output of the PI regulator, and obtaining the phase value theta 2 through diagonal frequency integration;
substituting the deviation value of the obtained inverter voltage phase value theta 1 and the power grid voltage phase value theta 2 into a closed-loop control algorithm for controlling the transfer function, namelyWherein->For the controlled device->Is proportional gain->Action for integration->For integral gain +.>For differential gain +.>The method is characterized by taking differential action, wherein the phase value of the grid voltage is a target value, so that the phase value of the automatic control inversion voltage is close to the phase value of the grid voltage, when the deviation value of the phase value of the inversion voltage and the phase value of the grid voltage is smaller than or equal to a preset threshold value, the phase value of the inversion voltage and the phase value of the grid voltage can be judged to be in a synchronous state, when the deviation value of the phase value of the inversion voltage and the phase value of the grid voltage is larger than the preset threshold value, the phase value of the inversion voltage and the phase value of the grid voltage can be judged to be in an asynchronous state, whether the phase value of the inversion voltage and the phase value of the grid voltage are synchronous or not can be accurately judged, a communication delay link is added in a closed-loop control algorithm for controlling a transfer function, and interference of communication delay on the control algorithm is eliminated through the communication delay link before operation of the closed-loop control algorithm for controlling the transfer function.
2. The method according to claim 1, wherein in S4, if it is determined that the synchronization is not performed, the synchronization operation is continued in S3.
3. The phase-locked grid-connected method based on communication according to claim 1, wherein the communication is any one of 485 communication, CAN communication and serial communication.
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| CN110165706A (en) * | 2019-05-30 | 2019-08-23 | 辽宁工程技术大学 | A kind of adaptive three-phase grid converter phaselocked loop and its locking phase control method |
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| CN102723741A (en) * | 2012-04-26 | 2012-10-10 | 南京航空航天大学 | Grid connection presynchronization control method of microgrid inverter based on droop control |
| CN105870972A (en) * | 2016-06-16 | 2016-08-17 | 扬州华鼎电器有限公司 | Intelligent control system of photovoltaic microgrid PWM (pulse-width modulation) inverter |
| CN110165706A (en) * | 2019-05-30 | 2019-08-23 | 辽宁工程技术大学 | A kind of adaptive three-phase grid converter phaselocked loop and its locking phase control method |
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