CN113725901A - Energy storage converter grid-connected and off-grid switching control method - Google Patents

Energy storage converter grid-connected and off-grid switching control method Download PDF

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Publication number
CN113725901A
CN113725901A CN202110977189.XA CN202110977189A CN113725901A CN 113725901 A CN113725901 A CN 113725901A CN 202110977189 A CN202110977189 A CN 202110977189A CN 113725901 A CN113725901 A CN 113725901A
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grid
energy storage
working state
storage converter
voltage
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顾海峰
樊小虎
汪盼
毛建良
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Suzhou Zhongchu Puhua Electric Power Co ltd
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Suzhou Zhongchu Puhua Electric Power Co ltd
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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
    • H02J3/381—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
    • H02J3/28—Arrangements for balancing of the load in a network by storage of energy
    • H02J3/32—Arrangements for balancing of the load in a network by storage of energy using batteries with converting means
    • 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
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • 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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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention relates to a grid-connected and off-grid switching control method for an energy storage converter, which comprises the steps of detecting the working state of the energy storage converter; when the working state of the energy storage converter is a grid-connected working state, detecting whether the three-phase grid voltage is smaller than a limit value, if so, taking the phase angle and the amplitude of the three-phase grid voltage of the energy storage converter in the grid-connected working state as the phase angle and the amplitude of the three-phase grid voltage in the off-grid working state, and realizing the smooth transition of the energy storage converter from the grid-connected working state to the off-grid working state; when the working state of the energy storage converter is an off-grid working state, whether the voltage of a three-phase power grid during off-grid operation is larger than a limit value is detected, if so, the difference value between the phase angle of the off-grid voltage and the phase angle of the voltage of the three-phase power grid in the off-grid working state is controlled to be within a specified range, and the energy storage converter is switched from the off-grid working state to a grid-connected working state. The system can realize the stable switching of the grid-connected and off-grid modes of the system, and improves the stability and reliability of the energy accumulator during working.

Description

Energy storage converter grid-connected and off-grid switching control method
Technical Field
The invention relates to the technical field of high-voltage energy storage, in particular to a grid-connected and off-grid switching control method for an energy storage converter.
Background
The high-voltage energy storage converter is a key device of a high-voltage energy storage system. When a distribution network fails or an upper computer sends a grid disconnection instruction, the high-voltage energy storage converter needs to be transited from a grid connection mode to a grid disconnection mode so as to ensure the operation in an island state; after the distribution network fault is eliminated, the high-voltage energy storage system needs to be transited from an off-grid mode to a grid-connected mode, and the power supply reliability of the power grid is improved.
In the prior art, the input voltage of the high-voltage energy storage converter reaches 1000V at most, when the grid-connected operation mode is switched to the off-grid operation mode, the energy storage converter is unstable in operation, the grid voltage is easy to change suddenly, the energy storage converter is unstable in operation, and the power supply quality of the load side of the energy storage converter is influenced finally.
Disclosure of Invention
The technical problem to be solved by the invention is to provide a grid-connected and off-grid switching control method for an energy storage converter, which can realize stable switching of grid-connected and off-grid modes of a system and improve the stability and reliability of an energy storage during working.
In order to solve the technical problem, the invention provides a grid-connected and off-grid switching control method for an energy storage converter, which comprises the following steps: detecting the working state of the energy storage converter; when the working state of the energy storage converter is a grid-connected working state, detecting whether the three-phase grid voltage of the energy storage converter during grid-connected operation is smaller than a limit value, if so, taking the phase angle and the amplitude of the three-phase grid voltage of the energy storage converter in the grid-connected working state as the phase angle and the amplitude of the three-phase grid voltage of the energy storage converter in an off-grid working state, and realizing the smooth transition of the energy storage converter from the grid-connected working state to the off-grid working state; when the working state of the energy storage converter is an off-grid working state, detecting whether the voltage of a three-phase power grid during the off-grid operation of the energy storage converter is larger than a limit value, if so, controlling the difference value between the off-grid voltage phase angle and the three-phase power grid voltage phase angle of the energy storage converter in the off-grid working state to be within a specified range, and realizing the stable switching of the energy storage converter from the off-grid working state to a grid-connected working state.
Preferably, the "smooth transition of the energy storage converter from the grid-connected working state to the off-grid working state" specifically includes the following steps: s101, the energy storage converter operates in a grid-connected working state and enters a grid-connected control loop; s102, acquiring a limit value of the voltage of the three-phase power grid; judging whether the three-phase power grid voltage of the energy storage converter in the grid-connected working state is smaller than the limit value or not, and if so, entering the next step; and S103, switching the energy storage converter to operate in an off-grid working state.
Preferably, the limit value for the three-phase system voltage is set to 80V.
Preferably, between S102 and S103, further comprising: when the energy storage converter operates in the grid-connected control loop, detecting and storing a phase angle and an amplitude value of the voltage of the three-phase power grid; disconnecting a relay in the grid-connected control loop, and converting the grid-connected control loop into an off-grid control loop; and taking the phase angle and the amplitude of the three-phase power grid voltage in the grid-connected control loop as the phase angle and the amplitude of the three-phase power grid voltage in the off-grid control loop.
Preferably, the "stable switching of the energy storage converter from the off-grid operating state to the grid-connected operating state" specifically includes the following steps: s201, the energy storage converter operates in an off-grid working state and enters an off-grid control loop; s202, acquiring a limit value of the three-phase power grid voltage; judging whether the three-phase power grid voltage of the energy storage converter is larger than a limit value in an off-grid working state, if so, entering the next step; and S203, the energy storage converter is switched to operate in a grid-connected working state.
Preferably, the limit value for the three-phase system voltage is set to 80V.
Preferably, between S203 and S203, further comprising: when the energy storage converter runs in the off-grid control loop, acquiring the off-grid voltage phase angle and the three-phase grid voltage phase angle; setting a difference range of the off-grid voltage phase angle and the three-phase grid voltage phase angle; calculating a difference value between the off-grid voltage phase angle and the three-phase grid voltage phase angle, and judging whether the difference value is within a difference value range; if the difference value is within the range of the difference value, converting the off-grid control loop into a grid-connected control loop; and if the difference value is not within the range of the difference value, adjusting the off-grid voltage and the three-phase power grid voltage.
Preferably, the difference range is set to 0 to 30V.
Preferably, the three-phase grid voltage phase angle of the energy storage converter in the off-grid working state is obtained according to a decoupling software phase locking method of a double synchronous coordinate system.
Preferably, the method for acquiring the phase angle of the three-phase grid voltage of the energy storage converter in the off-grid working state comprises the following steps of detecting the three-phase grid voltage when the energy storage converter is in the off-grid working state; the three-phase power grid voltage in the off-grid working state is subjected to Clark conversion and Park conversion to obtain positive sequence voltage and negative sequence voltage of the three-phase power grid; and processing the positive sequence voltage and the negative sequence voltage of the three-phase power grid by using a decoupling method of a double synchronous coordinate system to obtain a phase angle of the three-phase power grid voltage.
Compared with the prior art, the technical scheme of the invention has the following advantages:
1. the energy storage converter can be rapidly switched between two grid-connected and grid-disconnected operation modes, and can operate in a grid-connected mode and an off-grid mode. It integrates the advantages and disadvantages of grid-connected inverters and off-grid inverters.
2. When the energy storage AC device is switched from a grid-connected working state to an off-grid working state, a three-phase grid voltage phase angle and an amplitude value can be used as the three-phase grid voltage phase angle and the amplitude value of the energy storage converter in the off-grid working state; the output current cannot fluctuate, and the energy storage alternating current device can be smoothly switched from a grid-connected working state to an off-grid working state.
3. When the energy storage alternating current device is switched from the off-grid working state to the grid-connected working state, the difference value between the off-grid voltage phase angle and the three-phase grid voltage phase angle of the energy storage converter in the off-grid working state can be controlled within a specified range, the working stability of the energy storage converter is improved, and the power supply reliability of a micro-grid is improved.
Drawings
In order that the present disclosure may be more readily and clearly understood, reference is now made to the following detailed description of the present disclosure taken in conjunction with the accompanying drawings, in which:
FIG. 1 is a schematic flow chart of an energy storage converter switching from a grid-connected working state to an off-grid working state according to the present invention;
fig. 2 is a schematic flow chart of the energy storage converter switching from the off-grid working state to the grid-connected working state according to the present invention.
Detailed Description
The present invention is further described below in conjunction with the following figures and specific examples so that those skilled in the art may better understand the present invention and practice it, but the examples are not intended to limit the present invention.
Referring to fig. 1 to 2, the invention discloses a parallel-grid and off-grid switching control method for an energy storage converter, which includes:
the energy storage converter is switched from a grid-connected working state to an off-grid working state and the energy storage converter is switched from the off-grid working state to the grid-connected working state.
When the energy storage converter is switched from an off-grid working state to a grid-connected working state, the method specifically comprises the following steps:
and 101, enabling the energy storage converter to enter the grid-connected control loop, and enabling the energy storage converter to run in a grid-connected working state.
And 102, acquiring a limit value of the three-phase power grid voltage, wherein the limit value of the three-phase power grid voltage is preferably 80V.
And acquiring a three-phase power grid voltage value when the energy storage converter operates in a grid-connected working state. And judging whether the three-phase power grid voltage of the energy storage converter in the grid-connected working state is smaller than the limit value, and if so, entering the next step.
And 103, switching the energy storage converter to operate in an off-grid working state.
Preferably, when the three-phase grid voltage of the energy storage converter in the grid-connected working state is not less than the limit value, the energy storage converter still operates in the grid-connected working state. Further, between step 102 and step 103, further comprising: when the energy storage converter operates in a grid-connected control loop, the phase angle and the amplitude of the three-phase grid voltage at the moment are detected and stored. And initializing the related parameters, and simultaneously disconnecting a relay in the grid-connected control loop to convert the grid-connected control loop into an off-grid control loop. The phase angle and the amplitude of the three-phase power grid voltage of the energy storage converter in the grid-connected working state are used as the phase angle and the amplitude of the three-phase power grid voltage of the energy storage converter in the off-grid working state, and the voltage on a bus capacitor is prevented from sudden change by using a bus clamping voltage control method, so that the energy storage converter is smoothly transited from the grid-connected working state to the off-grid working state.
When the energy storage converter is switched from an off-grid working state to a grid-connected working state, the method specifically comprises the following steps:
step 201, the energy storage converter enters an off-grid control loop, so that the energy storage converter operates in an off-grid working state.
Step 202, acquiring a limit value of the three-phase power grid voltage when the energy storage converter operates in an off-grid working state, wherein the limit value of the three-phase power grid voltage is preferably 80V.
And acquiring a three-phase power grid voltage value when the energy storage converter operates in an off-grid working state. And judging whether the three-phase power grid voltage of the energy storage converter in the off-grid working state is greater than the limit value, and if so, entering the next step.
And 203, switching the energy storage converter to operate in a grid-connected working state.
Preferably, if the three-phase grid voltage of the energy storage converter in the off-grid working state is not greater than the limit value, the energy storage converter continues to operate in the off-grid working state.
Further preferably, the method further includes, between step 202 and step 203: when the energy storage converter operates in the off-grid control loop, an off-grid voltage phase angle and a three-phase grid voltage phase angle are obtained.
And setting the difference range of the off-grid voltage phase angle and the three-phase grid voltage phase angle, wherein the difference range is preferably 0-30V.
And calculating the difference value between the off-grid voltage phase angle and the three-phase grid voltage phase angle and judging whether the difference value is in the range of the difference value. And if the difference value is within the range of the difference value, converting the off-grid control loop into a grid-connected control loop. And if the difference value is not within the difference value range, adjusting the off-grid voltage and the three-phase power grid voltage to enable the difference value to meet the difference value range.
The method comprises the steps of obtaining a three-phase power grid voltage phase angle of an energy storage converter in an off-grid working state according to a decoupling software phase locking method of a double-synchronous coordinate system. When obtaining three-phase electric network voltage phase angle of energy storage converter under off-grid operating condition, specifically include: and when the energy storage converter is in an off-grid working state, detecting the voltage of the three-phase power grid.
Obtaining positive sequence voltage by Clark (Clark) and Park (Park) conversion
Figure BDA0003227760980000061
And
Figure BDA0003227760980000062
negative sequence voltage
Figure BDA0003227760980000063
And
Figure BDA0003227760980000064
derived by a decoupling method of a double synchronous coordinate system
Figure BDA0003227760980000065
Wherein, the above
Figure BDA0003227760980000066
For the positive sequence d-axis component of the voltage,
Figure BDA0003227760980000067
for the positive sequence q-axis component of the voltage,
Figure BDA0003227760980000068
is the d-axis component of the negative sequence of the voltage,
Figure BDA0003227760980000069
is a negative voltage sequence q-axis component.
Figure BDA00032277609800000610
For the decoupled positive sequence d-axis component of the voltage,
Figure BDA00032277609800000611
for the decoupled positive sequence q-axis component of the voltage,
Figure BDA00032277609800000612
for the decoupled negative sequence d-axis component of the voltage,
Figure BDA00032277609800000613
is the decoupled negative sequence q-axis component of the voltage.
Using formulas
Figure BDA00032277609800000614
The angular frequency w is determined, and then according to the formula d θ wdt, θ (w)1+w2+w3+ …) × dt, the real-time phase angle of the three-phase network is determined. Wherein kp is a proportionality coefficient, ki is an integral coefficient, d theta is a phase angle of unit time, theta is a real-time phase angle of a three-phase power grid, and w1, w2 and w3 are angular frequencies.
And after the phase synchronization is successful, comparing instantaneous values of the off-grid voltage phase angle and the three-phase grid voltage phase angle, and if the difference value of the two values is within a specified range, combining the grid relays and entering a grid-connected control loop.
Preferably, when the energy storage converter is switched from the off-grid mode to the grid-connected mode, the phase angle of the off-grid voltage and the phase angle of the three-phase grid voltage gradually approach each other, so that oscillation generated when the energy storage converter system operates is inhibited, stable switching of the grid-connected and off-grid modes of the system can be realized, and the stability and reliability of the energy storage device during operation are improved.
Examples
In the actual operation process of the micro-grid, under a grid-connected mode, a grid-connected control loop is entered, the frequency of the control loop is selected to be 20kHz, when the real-time three-phase grid voltage effective value is detected to be less than 40V, the micro-grid enters an off-grid state, meanwhile, the phase angle and the amplitude of the current three-phase grid voltage are stored, PI (proportional and integral) parameters of a voltage ring and a current ring of a battery and an off-grid are initialized, a grid-connected relay is disconnected, the current phase angle of the three-phase grid voltage is used as the phase angle of the off-grid voltage, and the amplitude of the three-phase grid voltage is used as the amplitude of the off-grid voltage.
The step length of the phase angle in the off-grid state is fixed, when the phase angle exceeds 360 degrees, the phase angle starts to participate in control from 0, when the voltage of the three-phase power grid is detected to be greater than 80V, the grid-connected mode is considered to be entered, the phase angle of the off-grid and the phase angle of the power grid are detected in real time, the phase angle of the power grid is realized by adopting a decoupling software phase-locking method based on a double synchronous coordinate system, the phase angle of the off-grid is compared with the phase angle of the three-phase power grid, and the instantaneous values delta U of the voltage of the three-phase power grid and the off-grid voltage are comparedd. Wherein Δ Ud＝UGrid-UEPS(UGridFor instantaneous value of network voltage, UEPSInstantaneous value of off-grid voltage) if the two are different by a value of DelauudAnd in a specified range, combining the grid relays and entering a grid-connected control loop. And in the grid-connected and off-grid switching process, a bus clamping voltage control method is added, and when the difference value between the voltage of the bus capacitor and the reference voltage of the bus capacitor is greater than 30V, the system is unstable, adjustment is needed, and the difference value is controlled within 30V.
As will be appreciated by one skilled in the art, embodiments of the present application may be provided as a method, system, or computer program product. Accordingly, the present application may take the form of an entirely hardware embodiment, an entirely software embodiment or an embodiment combining software and hardware aspects. Furthermore, the present application may take the form of a computer program product embodied on one or more computer-usable storage media (including, but not limited to, disk storage, CD-ROM, optical storage, and the like) having computer-usable program code embodied therein.
The present application is described with reference to flowchart illustrations and/or block diagrams of methods, apparatus (systems), and computer program products according to embodiments of the application. It will be understood that each flow and/or block of the flow diagrams and/or block diagrams, and combinations of flows and/or blocks in the flow diagrams and/or block diagrams, can be implemented by computer program instructions. These computer program instructions may be provided to a processor of a general purpose computer, special purpose computer, embedded processor, or other programmable data processing apparatus to produce a machine, such that the instructions, which execute via the processor of the computer or other programmable data processing apparatus, create means for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be stored in a computer-readable memory that can direct a computer or other programmable data processing apparatus to function in a particular manner, such that the instructions stored in the computer-readable memory produce an article of manufacture including instruction means which implement the function specified in the flowchart flow or flows and/or block diagram block or blocks.
These computer program instructions may also be loaded onto a computer or other programmable data processing apparatus to cause a series of operational steps to be performed on the computer or other programmable apparatus to produce a computer implemented process such that the instructions which execute on the computer or other programmable apparatus provide steps for implementing the functions specified in the flowchart flow or flows and/or block diagram block or blocks.
It should be understood that the above examples are only for clarity of illustration and are not intended to limit the embodiments. Other variations and modifications will be apparent to persons skilled in the art in light of the above description. And are neither required nor exhaustive of all embodiments. And obvious variations or modifications of the invention may be made without departing from the spirit or scope of the invention.

Claims (10)

1. A grid-connected and off-grid switching control method for an energy storage converter is characterized by comprising the following steps:
detecting the working state of the energy storage converter;
when the working state of the energy storage converter is a grid-connected working state, detecting whether the three-phase grid voltage of the energy storage converter during grid-connected operation is smaller than a limit value, if so, taking the phase angle and the amplitude of the three-phase grid voltage of the energy storage converter in the grid-connected working state as the phase angle and the amplitude of the three-phase grid voltage of the energy storage converter in an off-grid working state, and realizing the smooth transition of the energy storage converter from the grid-connected working state to the off-grid working state;
when the working state of the energy storage converter is an off-grid working state, detecting whether the voltage of a three-phase power grid during the off-grid operation of the energy storage converter is larger than a limit value, if so, controlling the difference value between the off-grid voltage phase angle and the three-phase power grid voltage phase angle of the energy storage converter in the off-grid working state to be within a specified range, and realizing the stable switching of the energy storage converter from the off-grid working state to a grid-connected working state.
2. The grid-connected and grid-disconnected switching control method of the energy storage converter according to claim 1, wherein the energy storage converter is in smooth transition from a grid-connected working state to a grid-disconnected working state, and the method specifically comprises the following steps:
s101, the energy storage converter operates in a grid-connected working state and enters a grid-connected control loop;
s102, acquiring a limit value of the voltage of the three-phase power grid; judging whether the three-phase power grid voltage of the energy storage converter in the grid-connected working state is smaller than the limit value or not, and if so, entering the next step;
and S103, switching the energy storage converter to operate in an off-grid working state.
3. The method according to claim 2, wherein the limit value of the three-phase grid voltage is set to 80V.
4. The grid-connected and grid-disconnected switching control method of the energy storage converter according to claim 2, wherein between the step S102 and the step S103, further comprising:
detecting a phase angle and an amplitude of three-phase grid voltage when the energy storage converter operates in a grid-connected control loop;
disconnecting a relay in the grid-connected control loop, and converting the grid-connected control loop into an off-grid control loop;
and taking the phase angle and the amplitude of the three-phase power grid voltage in the grid-connected control loop as the phase angle and the amplitude of the three-phase power grid voltage in the off-grid control loop.
5. The grid-connected and grid-disconnected switching control method of the energy storage converter according to claim 1, wherein the energy storage converter is stably switched from the grid-disconnected working state to the grid-connected working state, and specifically comprises the following steps:
s201, the energy storage converter operates in an off-grid working state and enters an off-grid control loop;
s202, acquiring a limit value of the three-phase power grid voltage; judging whether the three-phase power grid voltage of the energy storage converter in the off-grid working state is greater than a limit value, if so, entering the next step;
and S203, the energy storage converter is switched to operate in a grid-connected working state.
6. The method according to claim 5, wherein the limit value of the three-phase grid voltage is set to 80V.
7. The grid-connected and grid-disconnected switching control method of the energy storage converter according to claim 5, wherein between the S202 and the S203, further comprising:
when the energy storage converter runs in the off-grid control loop, acquiring the off-grid voltage phase angle and the three-phase grid voltage phase angle;
setting a difference range of the off-grid voltage phase angle and the three-phase grid voltage phase angle;
calculating a difference value between the off-grid voltage phase angle and the three-phase grid voltage phase angle, and judging whether the difference value is within a difference value range;
if the difference value is within the range of the difference value, converting the off-grid control loop into a grid-connected control loop; and if the difference value is not in the difference value range, adjusting the off-grid voltage and the three-phase power grid voltage until the difference value between the off-grid voltage phase angle and the three-phase power grid voltage phase angle is in the difference value range.
8. The method for controlling grid-connected and off-grid switching of the energy storage converter according to claim 1, wherein the difference range is set to 0-30V.
9. The grid-connected and grid-disconnected switching control method of the energy storage converter according to claim 1, wherein a three-phase grid voltage phase angle of the energy storage converter in an off-grid working state is obtained according to a decoupling software phase locking principle of a double synchronous coordinate system.
10. The grid-connected and grid-disconnected switching control method of the energy storage converter according to claim 7, wherein the obtaining of the phase angle of the three-phase grid voltage in the off-grid working state specifically comprises:
detecting the three-phase power grid voltage of the energy storage converter in an off-grid working state;
the three-phase power grid voltage in the off-grid working state is subjected to Clark conversion and Park conversion to obtain positive sequence voltage and negative sequence voltage of the three-phase power grid voltage;
and processing the positive sequence voltage and the negative sequence voltage by using a decoupling method of a double synchronous coordinate system to obtain a phase angle of the three-phase power grid voltage.
CN202110977189.XA 2021-08-24 2021-08-24 Energy storage converter grid-connected and off-grid switching control method Pending CN113725901A (en)

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Cited By (1)

* Cited by examiner, † Cited by third party
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

Cited By (2)

* Cited by examiner, † Cited by third party
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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