CN115528740A - Synchronous control method for voltage converted from off-grid to grid-connected - Google Patents
Synchronous control method for voltage converted from off-grid to grid-connected Download PDFInfo
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- CN115528740A CN115528740A CN202211147487.7A CN202211147487A CN115528740A CN 115528740 A CN115528740 A CN 115528740A CN 202211147487 A CN202211147487 A CN 202211147487A CN 115528740 A CN115528740 A CN 115528740A
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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
- H02J3/42—Synchronising a generator for connection to a network or to another generator with automatic parallel connection when synchronisation is achieved
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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
-
- 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
- H02J3/381—Dispersed generators
-
- 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
- H02J3/44—Synchronising a generator for connection to a network or to another generator with means for ensuring correct phase sequence
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/493—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode the static converters being arranged for operation in parallel
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
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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
- H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
- H02J2300/20—The dispersed energy generation being of renewable origin
- H02J2300/22—The renewable source being solar energy
- H02J2300/24—The renewable source being solar energy of photovoltaic origin
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E10/00—Energy generation through renewable energy sources
- Y02E10/50—Photovoltaic [PV] energy
- Y02E10/56—Power conversion systems, e.g. maximum power point trackers
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Inverter Devices (AREA)
Abstract
The invention discloses a synchronous control method for converting an off-grid voltage into a grid voltage, which is used for restoring the grid voltage and frequency of a power grid in off-grid operation according to preset time, executing a phase synchronization program according to the sampled grid voltage so as to lock the phase of the grid voltage, wherein the q-axis component is equal to 0, so that phase synchronization is achieved; taking the effective value of the power grid voltage as the voltage effective value ring reference of the inverter; controlling low-order harmonic synchronization according to a formula of inversion voltage reference = voltage effective value ring + power grid voltage instantaneous sampling value-power grid voltage low-pass filtering value; controlling higher harmonic synchronization according to modulation target voltage = inverter current loop output + grid voltage feedforward; and outputting a driving signal for driving the IGBT according to the PWM modulation so as to synchronize the amplitude, and immediately switching to grid-connected operation. When the off-grid is converted into the grid-connected, a control method that the off-grid voltage is consistent with the grid voltage in high and low order harmonics is realized, so that zero current switching from the off-grid to the grid-connected is ensured, and impact current is avoided.
Description
Technical Field
The invention relates to the technical field of photovoltaic system operation control, in particular to a method for synchronously controlling off-grid to grid-connected voltage.
Background
At present, in the operation process of a photovoltaic system, when switching from off-grid to grid-connected, harmonic current is large, when a grid-connected relay is not powered off, harmonic waves of off-grid voltage and grid voltage can not be consistent, fundamental wave consistency can only be achieved, large impact can be caused to a grid, when new energy power generation is connected into the grid, the impact on the quality of electric energy of a traditional grid is large, control on the quality of electric energy is not facilitated, the large power impact can have certain harmfulness on the voltage and frequency of the traditional grid, voltage instability can be caused, the power consumption of a user is influenced, and grid-connected equipment can be damaged when the power impact is serious.
Disclosure of Invention
The invention aims to solve the defects of the prior art and provides an off-grid to grid voltage synchronous control method, which has the following specific mode.
The invention discloses a synchronous control method for converting off-grid voltage into grid-connected voltage, which is characterized by comprising the following steps of:
the method comprises the following steps that S1, the voltage and the frequency of a power grid in off-grid operation are recovered according to preset time, and if the recovery time is not reached and the voltage and the frequency of the power grid are abnormal, the recovery is restarted; if the recovery time is up and the voltage and frequency of the power grid are normal, the step S2 is entered;
s2, sampling the grid voltage in off-grid operation, and executing a phase synchronization program according to the sampled grid voltage to lock the grid voltage in phase, wherein the q-axis component is equal to 0, so that phase synchronization is achieved; if the phase synchronization is not successful, the phase synchronization procedure is repeatedly executed until the phase synchronization is successful; if the phase synchronization is successful, the step S3 is entered;
s3, synchronizing effective values, taking the effective value of the grid voltage as a voltage effective value ring reference of the inverter, and entering the step S4;
s4, synchronizing low-order harmonics, controlling the low-order harmonics of the off-grid voltage to be synchronized with the low-order harmonics of the grid voltage according to a formula of inversion voltage reference = voltage effective value ring + grid voltage instantaneous sampling value-grid voltage low-pass filtering value, and entering the step S5;
step S5, synchronizing higher harmonics, controlling the higher harmonics of the off-grid voltage to be synchronized with the higher harmonics of the grid voltage according to the modulation target voltage = inverter current loop output + grid voltage feedforward, and entering step S6;
s6, outputting a driving signal for driving the IGBT according to PWM modulation so as to synchronize the amplitude; if the amplitude synchronization is successful, immediately switching from off-grid operation to grid-connected operation; if the amplitude synchronization fails.
According to the above off-grid to grid voltage synchronization control method, the phase synchronization program is executed as follows:
s21, performing closed-loop regulation according to the sampled power grid voltage to enable the q-axis component of the power grid voltage to be 0, and meanwhile, outputting a phase-locked frequency fo which serves as the current off-grid operation frequency;
step S22, integrating the fo frequency to obtain a phase locking Angle PLL _ Angle, and carrying out dq transformation on the power grid voltage by using the phase locking Angle PLL _ Angle to obtain a q-axis component of the power grid voltage; if the grid voltage phase locking is successful, namely the q-axis component is equal to 0, the phase synchronization is successful, and if the grid voltage phase locking is unsuccessful, namely the q-axis component is not equal to 0, the phase synchronization is failed, and the steps S21 and S22 are repeatedly executed.
The invention describes a synchronous control method for converting off-grid voltage into grid-connected voltage, which utilizes amplitude synchronization to ensure that a voltage loop in off-grid operation can output low-frequency harmonic waves contained in a power grid, namely the low-frequency harmonic waves are smaller than the loop bandwidth of the voltage loop, and higher harmonic waves depend on feed-forward of a current loop, namely feed-forward of the instantaneous value of the power grid voltage is adopted, so that the same frequency, same phase, same amplitude and same harmonic waves of the off-grid output voltage of an inverter and the power grid voltage can be ensured, impact current in the process of converting off-grid voltage into grid-connected voltage is avoided, and the balanced distribution of power of a plurality of off-grid parallel machines is not influenced.
In addition, when the off-grid is converted into the grid-connected, a control method that the off-grid voltage is consistent with the grid in terms of high and low order harmonics is realized, so that zero current switching of the off-grid to the grid-connected is guaranteed.
Drawings
FIG. 1 is a control flow chart for switching between grid-connection and off-grid operation;
FIG. 2 is a phase synchronization control flow chart;
FIG. 3 is a flow chart of amplitude synchronization control.
Detailed Description
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 only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments that can be derived by one of ordinary skill in the art from the embodiments given herein are intended to be within the scope of the present invention.
The embodiment is as follows:
as shown in fig. 1 to fig. 3, the method for synchronously controlling an off-grid to on-grid voltage described in this embodiment is characterized by including the following steps:
the method comprises the following steps that S1, the voltage and the frequency of a power grid in off-grid operation are recovered according to preset time, and if the recovery time is not reached and the voltage and the frequency of the power grid are abnormal, the recovery is restarted; if the recovery time is up and the voltage and frequency of the power grid are normal, the step S2 is entered;
s2, sampling the grid voltage in off-grid operation, and executing a phase synchronization program according to the sampled grid voltage to lock the grid voltage in phase, wherein the q-axis component is equal to 0, so that phase synchronization is achieved; if the phase synchronization is not successful, the phase synchronization procedure is repeatedly executed until the phase synchronization is successful; if the phase synchronization is successful, the step S3 is entered;
s3, synchronizing effective values, taking the effective value of the grid voltage as a voltage effective value ring reference of the inverter, and entering the step S4;
s4, synchronizing low-order harmonics, controlling the synchronization of the low-order harmonics of the off-grid voltage and the low-order harmonics of the grid voltage according to a formula of inverter voltage reference = voltage effective value ring + grid voltage instantaneous sampling value-grid voltage low-pass filtering value, and entering the step S5; the low-order harmonic of the off-grid voltage is extracted and superposed on the reference value of the voltage instantaneous value ring to participate in control, the response is slow in a loop implementation mode, only the low-order harmonic can be tracked, and therefore the low-order harmonic of the off-grid voltage and the low-order harmonic of the grid voltage are synchronized.
Step S5, synchronizing higher harmonics, controlling the higher harmonics of the off-grid voltage to be synchronized with the higher harmonics of the grid voltage according to the modulation target voltage = inverter current loop output + grid voltage feedforward, and entering step S6; the harmonic component is obtained by the instantaneous value of the power grid voltage and the filtered value of the power grid voltage, the harmonic component is used as voltage feedforward and current loop output to jointly act on PWM, the response is fast, and finally the inversion voltage synchronous with the power grid voltage is obtained.
S6, outputting a driving signal for driving the IGBT according to PWM modulation so as to synchronize the amplitude; if the amplitude synchronization is successful, immediately switching from off-grid operation to grid-connected operation; if the amplitude synchronization fails. In the field of power electronic control, PWM is a common form of implementing strong electric control with weak signals, and IGBT is an execution unit, playing an amplifying role. When the amplitude is detected to be asynchronous, PWM is adjusted through feedback closed-loop control, the inverter output voltage is adjusted after the IGBT is executed, the inverter output voltage gradually approaches the target voltage, and finally the steady-state error is controlled to be 0, so that the amplitude is also synchronous.
According to the above off-grid to on-grid voltage synchronization control method, the phase synchronization program is executed as follows:
s21, performing closed-loop regulation according to the sampled power grid voltage to enable the q-axis component of the power grid voltage to be 0, and meanwhile, outputting a phase-locked frequency fo which serves as the current off-grid operation frequency;
step S22, integrating fo frequency to obtain a phase-locked Angle PLL _ Angle, and carrying out dq conversion on the power grid voltage by the phase-locked Angle PLL _ Angle to obtain a q-axis component of the power grid voltage; if the grid voltage phase locking is successful, that is, the q-axis component is equal to 0, the phase synchronization is successful, and if the grid voltage phase locking is unsuccessful, that is, the q-axis component is not equal to 0, the phase synchronization is failed, and the steps S21 and S22 are repeatedly executed.
The synchronous control method for the voltage from the off-grid to the grid-connected utilizes amplitude synchronization, so that a voltage loop in off-grid operation can output low-frequency harmonic waves contained in a power grid, namely the low-frequency harmonic waves are smaller than the loop bandwidth of the voltage loop, and higher harmonic waves depend on feedforward of a current loop, namely the feedforward of the instantaneous value of the power grid voltage is adopted, so that the same frequency, the same phase, the same amplitude and the same harmonic waves of the voltage of the power grid of the inverter can be ensured, the impact current in the process of converting from the off-grid to the grid-connected is avoided, and the balanced distribution of the power of a plurality of off-grid parallel machines is not influenced.
In addition, when the off-grid is converted into the grid-connected, a control method that the off-grid voltage is consistent with the grid in terms of high and low order harmonics is realized, so that zero current switching of the off-grid to the grid-connected is guaranteed.
The present invention is not limited to the above-mentioned preferred embodiments, and any other products in various forms can be obtained by anyone in the light of the present invention, but any changes in the shape or structure thereof, which have the same or similar technical solutions as those of the present application, fall within the protection scope of the present invention.
Claims (2)
1. A synchronous control method for converting off-grid voltage into grid-connected voltage is characterized by comprising the following steps:
the method comprises the following steps that S1, the voltage and the frequency of a power grid in off-grid operation are recovered according to preset time, and if the recovery time is not reached and the voltage and the frequency of the power grid are abnormal, the recovery is restarted; if the recovery time is up and the voltage and frequency of the power grid are normal, the step S2 is entered;
s2, sampling the grid voltage in off-grid operation, and executing a phase synchronization program according to the sampled grid voltage to lock the grid voltage in phase, wherein the q-axis component is equal to 0, so that phase synchronization is achieved; if the phase synchronization is not successful, the phase synchronization procedure is repeatedly executed until the phase synchronization is successful; if the phase synchronization is successful, the step S3 is entered;
s3, synchronizing effective values, taking the effective value of the grid voltage as a voltage effective value ring reference of the inverter, and entering the step S4;
s4, synchronizing low-order harmonics, controlling the low-order harmonics of the off-grid voltage to be synchronized with the low-order harmonics of the grid voltage according to a formula of inversion voltage reference = voltage effective value ring + grid voltage instantaneous sampling value-grid voltage low-pass filtering value, and entering the step S5;
step S5, synchronizing higher harmonics, controlling the higher harmonics of the off-grid voltage to be synchronized with the higher harmonics of the grid voltage according to the modulation target voltage = inverter current loop output + grid voltage feedforward, and entering step S6;
s6, outputting a driving signal for driving the IGBT according to PWM modulation so as to synchronize the amplitude; if the amplitude synchronization is successful, immediately switching from off-grid operation to grid-connected operation; if the amplitude synchronization fails.
2. The off-grid to grid-connected voltage synchronization control method according to claim 1, wherein the phase synchronization program is executed by the following method:
s21, performing closed-loop regulation according to the sampled power grid voltage to enable the q-axis component of the power grid voltage to be 0, and meanwhile, outputting a phase-locked frequency fo which serves as the current off-grid operation frequency;
step S22, integrating the fo frequency to obtain a phase locking Angle PLL _ Angle, and carrying out dq transformation on the power grid voltage by using the phase locking Angle PLL _ Angle to obtain a q-axis component of the power grid voltage; if the grid voltage phase locking is successful, that is, the q-axis component is equal to 0, the phase synchronization is successful, and if the grid voltage phase locking is unsuccessful, that is, the q-axis component is not equal to 0, the phase synchronization is failed, and the steps S21 and S22 are repeatedly executed.
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| CN202211147487.7A CN115528740A (en) | 2022-09-19 | 2022-09-19 | Synchronous control method for voltage converted from off-grid to grid-connected |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116316728A (en) * | 2023-03-14 | 2023-06-23 | 上海正泰电源系统有限公司 | Automatic off-grid-to-grid phase tracking method based on bilateral phase locking |
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2022
- 2022-09-19 CN CN202211147487.7A patent/CN115528740A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN116316728A (en) * | 2023-03-14 | 2023-06-23 | 上海正泰电源系统有限公司 | Automatic off-grid-to-grid phase tracking method based on bilateral phase locking |
| CN116316728B (en) * | 2023-03-14 | 2024-03-29 | 上海正泰电源系统有限公司 | Automatic off-grid-to-grid phase tracking method based on bilateral phase locking |
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