CN114865704A - Grid-connected and grid-disconnected switching control method and system of two-stage energy storage converter - Google Patents

Grid-connected and grid-disconnected switching control method and system of two-stage energy storage converter Download PDF

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CN114865704A
CN114865704A CN202210644741.8A CN202210644741A CN114865704A CN 114865704 A CN114865704 A CN 114865704A CN 202210644741 A CN202210644741 A CN 202210644741A CN 114865704 A CN114865704 A CN 114865704A
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grid
current
converter
output
energy storage
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CN114865704B (en
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桑顺
朱悦
张雷
薛晓岑
黄杰杰
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Nantong University
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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
    • H02J3/007—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources
    • H02J3/0073—Arrangements for selectively connecting the load or loads to one or several among a plurality of power lines or power sources for providing alternative feeding paths between load and source when the main path fails, e.g. transformers, busbars
    • 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
    • H02J9/00—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting
    • H02J9/04—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source
    • H02J9/06—Circuit arrangements for emergency or stand-by power supply, e.g. for emergency lighting in which the distribution system is disconnected from the normal source and connected to a standby source with automatic change-over, e.g. UPS systems
    • 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
    • Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
    • Y02E40/10—Flexible AC transmission systems [FACTS]

Abstract

The invention relates to the technical field of electrical control, in particular to a grid-connected and off-grid switching control method and a grid-connected and off-grid switching control system of a two-stage energy storage converter. The invention can realize the automatic synchronization of the power grid according to the dynamic state of the direct current side inductor during the grid-connected operation without a phase-locked loop; the amplitude and the frequency of the voltage at the alternating current side of the current source type converter can be controlled during off-grid operation, and stable power supply is provided for a load; when a power grid fails and is disconnected with a load and a battery energy storage system, the two-stage energy storage converter can be automatically switched from a grid-connected operation mode to an off-grid operation mode, so that uninterrupted power supply for the load is realized, and the power supply reliability is improved; the damping injection module can enhance the operation stability of the two-stage energy storage converter in grid-connected and off-grid operation modes, and avoid the problem of oscillation instability caused by abnormal interaction of the current source type converter, a power grid and a load.

Description

Grid-connected and grid-disconnected switching control method and system of two-stage energy storage converter
Technical Field
The invention relates to the technical field of electrical control, in particular to a grid-connected and off-grid switching control method and a grid-connected and off-grid switching control system of a two-stage energy storage converter.
Background
The battery energy storage system can realize real-time storage and release of energy, plays a role in peak clipping and valley filling in the power system, can also improve the quality of grid-connected electric energy, and improves the operation stability of the power system. In addition, when the power grid fails and cannot supply power to the load, the battery energy storage system can continuously supply power to the load, and power supply reliability is enhanced.
However, for a two-stage battery energy storage system containing a current source type converter, a control strategy which can stably operate in a grid-connected operation mode and an off-grid operation mode is still lacked; in addition, when the power grid fails and is disconnected from the load and the battery energy storage system, a control strategy of off-grid switching needs to be researched, so that the battery energy storage system can reliably supply power to the load.
Disclosure of Invention
The invention aims to solve the problems and provides a grid-connected and off-grid switching control method and a grid-connected and off-grid switching control system for a two-stage energy storage converter, which can realize that the two-stage energy storage converter containing a current source type converter can stably run in a grid-connected running mode and an off-grid running mode; when the grid fails and is disconnected with the load and the battery energy storage system, the two-stage energy storage converter can be automatically switched from a grid-connected operation mode to an off-grid operation mode.
In order to achieve the purpose, the invention adopts the following technical scheme:
a grid-connected and off-grid switching control method for a two-stage energy storage converter is characterized in that a pre-stage converter outputs a reference value P of active power eref Feedback value P with active power e The difference is fed into a PI regulator, the output of the PI regulator is used as the input of the position 1 of a gating switch S1, the input of the position 2 of a gating switch S1 is 0, the output G1 of an island detection module is used as a control signal of a gating switch S1, the output of the control signal of a gating switch S1 is position 1 when the control signal of the gating switch S1 is 0, and the output of the control signal of a gating switch S1 is 1 when the control signal of the gating switch S1 is 1The output is position 2, the initial position of the gate switch S1 is in position 1; output of gate switch S1 and rated value I of DC side current dcN The sum is the reference value i of the direct current side current dcref ，i dcref Feedback value i of DC side current dc The difference enters a PI regulator, and the output of the PI regulator generates a trigger pulse s of a pre-converter through a modulation module e ；
Feedback value i of direct current side current dc Multiplying 100 pi by the reference value i of the DC side current dcref Equal to angular frequency omega in ，ω in The output after the angular frequency amplitude limiting link is omega out ，ω out The output after the integration link is phase theta; filter capacitor voltage u of AC side CL type filter Cabc Converted into u by rotating dq Cd 、u Cq The phase used to rotate the dq transformation is θ; reference value U of grid-connected point voltage amplitude pref Feedback value U of voltage amplitude of grid-connected point p The difference is multiplied by a gain K p The output of which is the d-axis reference value u of the filter capacitor voltage Cdref Q-axis reference u of filter capacitor voltage Cqref Is 0; d-axis reference u of filter capacitor voltage Cdref And a feedback value u Cd The difference enters a PI regulator, and the output of the PI regulator is the d-axis component of the modulation current of the current source type converter
Figure BDA0003683635440000021
Q-axis reference u of filter capacitor voltage Cqref And a feedback value u Cq The difference enters a PI regulator, and the output of the PI regulator is the q-axis component of the modulation current of the current source type converter
Figure BDA0003683635440000022
And
Figure BDA0003683635440000023
after entering the current amplitude generating module, the amplitude I of the modulation current of the current source type converter is generated g ，I g Entering a current amplitude limiting link; feedback value i of direct current side current dc Entering a damping injection module to be injected into the damping injection module,its output I z Output I of current limiting link gout The sum is the current amplitude I t Amplitude of current I t The phase theta is connected with the modulation current generation module to generate the modulation current of the current source type converter
Figure BDA0003683635440000024
Figure BDA0003683635440000025
Generating trigger pulse s of current source type converter after entering modulation module gabc 。
As a preferred technical scheme of the invention: the angular frequency amplitude limiting link outputs omega out And input omega in Have the following relationship between:
Figure BDA0003683635440000026
as a preferred technical scheme of the invention: the current amplitude limiting link outputs I gout And input I g Have the following relationship between:
Figure BDA0003683635440000027
in the formula (2), I gN The current amplitude rating is modulated for a current source converter.
As a preferred technical scheme of the invention: output of the damping injection module I z And input i dc Have the following relationship between:
Figure BDA0003683635440000028
in formula (3), s is Laplace operator, T is high-pass filter time constant, and K dc Is a high-pass filter gain;
the high-pass filtering time constant T and the high-pass filtering gain K dc The following relationship is satisfied:
0.001≤T≤1 (4)
Figure BDA0003683635440000029
in the formula (5), I dcN Is the rated value of the direct current side current.
As a preferred technical scheme of the invention: the island detection module adopts the following control method: generating a flag bit G according to the saturation time of the angular frequency amplitude limiting link ω When the saturation time of the angular frequency amplitude limiting link is less than or equal to 0.05s, the flag bit G ω When the saturation time of the angular frequency amplitude limiting link is more than 0.05s, the flag bit G ω Has a value of 1; generating a flag bit G according to the saturation time of the current amplitude limiting link i When the saturation time of the current amplitude limiting link is less than or equal to 0.08s, the flag bit G i Is 0, and when the saturation time of the current amplitude limiting link is more than 0.08s, the flag bit G i Has a value of 1; generating a flag bit G according to the absolute value of the DC side current deviation dc When the absolute value of the deviation of the direct current side current is divided by the rated value of the direct current side current and is less than or equal to 0.05, the flag bit G dc Is 0, and when the absolute value of the deviation of the DC side current divided by the rated value of the DC side current is greater than 0.05, the flag G dc Has a value of 1; flag bit G i The output of the falling edge Delayer1 and a flag G pass through a falling edge Delayer1 ω Entering a logic AND operation module, the output of the logic AND operation module is a flag bit G after passing through a falling edge Delayer2 s (ii) a Flag bit G s And flag bit G dc And entering a logic OR operation module, wherein the output of the logic OR operation module is the output G1 of the island detection module.
A control system of a grid-connected and off-grid switching control method of a two-stage energy storage converter comprises a preceding-stage converter directly connected with energy storage and a current source type converter connected with a power grid; the pre-stage converter is a bidirectional direct current/direct current converter, one side of the pre-stage converter is connected with the energy storage battery, and the other side of the pre-stage converter is connected with the current source type converter through an inductor; the current source type converter is a bidirectional direct current/alternating current converter, the direct current side of the current source type converter is connected with the pre-stage converter through an inductor, and the alternating current side of the current source type converter is connected to a grid-connected point through a CL type filter; the Load is connected to a grid-connected point, and the grid-connected point is connected to a power grid through a breaker BRK.
Compared with the prior art, the grid-connected and off-grid switching control method and the system of the two-stage energy storage converter have the following technical effects by adopting the technical scheme:
the invention can realize the automatic synchronization of the power grid according to the dynamic state of the direct current side inductor during the grid-connected operation without a phase-locked loop; the amplitude and the frequency of the voltage at the alternating current side of the current source type converter can be controlled during off-grid operation, and stable power supply is provided for a load; when a power grid fails and is disconnected with a load and a battery energy storage system, the two-stage energy storage converter can be automatically switched from a grid-connected operation mode to an off-grid operation mode, so that uninterrupted power supply for the load is realized, and the power supply reliability is improved; the damping injection module can enhance the operation stability of the two-stage energy storage converter in grid-connected and off-grid operation modes, and avoid the problem of oscillation instability caused by abnormal interaction of the current source type converter, a power grid and a load.
Drawings
Fig. 1 is a schematic diagram illustrating grid-connected and off-grid switching control of a two-stage energy storage converter according to an embodiment of the present invention;
FIG. 2 is a control block diagram of an island detection module according to an embodiment of the present invention;
fig. 3 is a simulation waveform of the parallel-grid and off-grid switching of the two-stage tank converter according to a simulation embodiment of the present invention.
Detailed Description
The present invention will be further explained with reference to the drawings so that those skilled in the art can more deeply understand the present invention and can carry out the present invention, but the present invention will be explained below by referring to examples, which are not intended to limit the present invention.
As shown in figure 1, a grid-connected and off-grid switching control method of a two-stage energy storage converterMethod, reference value P of active power output by preceding converter eref Feedback value P with active power e The difference enters a PI regulator, the output of the PI regulator is used as the input of the position 1 of a gating switch S1, the input of the position 2 of a gating switch S1 is 0, the output G1 of an island detection module is used as a control signal of a gating switch S1, the output of the control signal of a gating switch S1 is position 1 when the control signal of the gating switch S1 is 0, the output of the control signal of a gating switch S1 is position 2 when the control signal of the gating switch S1 is 1, and the initial position of the gating switch S1 is position 1; output of gate switch S1 and rated value I of DC side current dcN The sum is the reference value i of the direct current side current dcref ，i dcref Feedback value i of DC side current dc The difference enters a PI regulator, and the output of the PI regulator generates a trigger pulse s of a pre-converter through a modulation module e ；
Feedback value i of direct current side current dc Multiplying 100 pi by the reference value i of the DC side current dcref Equal to angular frequency omega in ，ω in The output after the angular frequency amplitude limiting link is omega out ，ω out The output after the integration link is phase theta; filter capacitor voltage u of AC side CL type filter Cabc Converted into u by rotating dq Cd 、u Cq The phase used to rotate the dq transformation is θ; reference value U of grid-connected point voltage amplitude pref Feedback value U of voltage amplitude of grid-connected point p The difference is multiplied by a gain K p The output of which is the d-axis reference value u of the filter capacitor voltage Cdref Q-axis reference u of filter capacitor voltage Cqref Is 0; d-axis reference u of filter capacitor voltage Cdref And a feedback value u Cd The difference enters a PI regulator, and the output of the PI regulator is the d-axis component of the modulation current of the current source type converter
Figure BDA0003683635440000041
Q-axis reference u of filter capacitor voltage Cqref And a feedback value u Cq The difference enters a PI regulator, and the output of the PI regulator is the q-axis component of the modulation current of the current source type converter
Figure BDA0003683635440000042
And
Figure BDA0003683635440000043
after entering the current amplitude generating module, the amplitude I of the modulation current of the current source type converter is generated g ，I g Entering a current amplitude limiting link; feedback value i of direct current side current dc Entering a damping injection module with output I z Output I of current limiting link gout The sum is the current amplitude I t Amplitude of current I t The phase theta is connected with the modulation current generation module to generate the modulation current of the current source type converter
Figure BDA0003683635440000044
Figure BDA0003683635440000045
Generating trigger pulse s of current source type converter after entering modulation module gabc 。
Angular frequency amplitude limiting link output omega out And input omega in Have the following relationship between:
Figure BDA0003683635440000046
current limiting link output I gout And input I g Have the following relationship between:
Figure BDA0003683635440000047
in the formula (2), I gN The current amplitude rating is modulated for a current source converter.
Output of the damping injection module I z And input i dc Have the following relationship between:
Figure BDA0003683635440000051
in formula (3), s is Laplace operator, T is high-pass filter time constant, and K dc Is a high-pass filter gain;
the high-pass filtering time constant T and the high-pass filtering gain K dc The following relationship is satisfied:
0.001≤T≤1 (4)
Figure BDA0003683635440000052
in the formula (5), I dcN Is the rated value of the direct current side current.
As shown in fig. 2, the islanding detection module adopts the following control method: generating a flag bit G according to the saturation time of the angular frequency amplitude limiting link ω When the saturation time of the angular frequency amplitude limiting link is less than or equal to 0.05s, the flag bit G ω Is 0, when the saturation time of the angular frequency amplitude limiting link is more than 0.05s, the flag bit G ω Has a value of 1; generating a flag bit G according to the saturation time of the current amplitude limiting link i When the saturation time of the current amplitude limiting link is less than or equal to 0.08s, the flag bit G i Is 0, and when the saturation time of the current amplitude limiting link is more than 0.08s, the flag bit G i Has a value of 1; generating a flag bit G according to the absolute value of the DC side current deviation dc When the absolute value of the deviation of the direct current side current is divided by the rated value of the direct current side current and is less than or equal to 0.05, the flag bit G dc Is 0, and when the absolute value of the deviation of the DC side current divided by the rated value of the DC side current is greater than 0.05, the flag G dc Has a value of 1; flag bit G i The output of the falling edge Delayer1 and a flag G pass through a falling edge Delayer1 ω Entering a logic AND operation module, the output of the logic AND operation module is a flag bit G after passing through a falling edge Delayer2 s (ii) a Flag bit G s And flag bit G dc And entering a logic OR operation module, wherein the output of the logic OR operation module is the output G1 of the island detection module.
A control system of a grid-connected and off-grid switching control method of a two-stage energy storage converter comprises a pre-stage converter directly connected with energy storage and a current source type converter connected with a power grid; the pre-stage converter is a bidirectional direct current/direct current converter, the specific topological structure and the voltage grade are not limited, one side of the pre-stage converter is connected with the energy storage battery, and the other side of the pre-stage converter is connected with the current source type converter through an inductor; the current source type converter is a bidirectional direct current/alternating current converter, a reverse resistance type power switch device is adopted, the specific topological structure and the voltage grade are not limited, the direct current side of the current source type converter is connected with the pre-stage converter through an inductor, and the alternating current side of the current source type converter is connected to a grid connection point through a CL type filter; the Load is connected to a grid-connected point, and the grid-connected point is connected to a power grid through a breaker BRK.
As shown in fig. 3, in a simulation embodiment of the present invention, which is a simulation waveform of the parallel-to-off switching of the two-stage energy storage converter, before 13.8s, the two-stage energy storage converter operates in the grid-connected mode, and the grid-connected point voltage U is a voltage U pabc Direct side current i of a current source converter of rated value, i.e. 1.0p.u dc The output active power of the current source type converter is 1.0p.u., and the output reactive power is 0; when the voltage is 13.8s, the grid-connected point is disconnected with the power grid, the two-stage energy storage converter is automatically switched to the off-grid operation mode, the active power and the reactive power consumed by the accessed load are respectively 0.5p.u. and 0.25p.u., the current source type converter outputs the active power of 0.5p.u., and outputs the reactive power of 0.25p.u., and as can be seen from fig. 3, the two-stage energy storage converter can stably operate in the grid-connected mode and the off-grid mode, can be stably switched to the off-grid operation mode from the grid-connected operation mode, and is stable in the transition process.
The invention can realize the automatic synchronization of the power grid according to the dynamic state of the direct current side inductor during the grid-connected operation without a phase-locked loop; when the system runs off the grid, the amplitude and the frequency of the voltage on the alternating current side of the current source type converter can be controlled, and the power is stably supplied to a load. When the power grid fails and is disconnected with the load and the battery energy storage system, the two-stage energy storage converter can be automatically switched from a grid-connected operation mode to an off-grid operation mode, uninterrupted power supply to the load is achieved, and power supply reliability is improved. The provided damping injection module can enhance the operation stability of the two-stage energy storage converter in grid-connected and off-grid operation modes, and avoid the problem of oscillation instability caused by abnormal interaction of the current source type converter, a power grid and a load.
The above-mentioned embodiments, objects, technical solutions and advantages of the present invention are further described in detail, it should be understood that the above-mentioned embodiments are only illustrative of the present invention, and are not intended to limit the scope of the present invention, and any person skilled in the art should understand that equivalent changes and modifications made without departing from the concept and principle of the present invention should fall within the protection scope of the present invention.

Claims (6)

1. A grid-connected and off-grid switching control method of a two-stage energy storage converter is characterized in that a pre-stage converter outputs a reference value P of active power eref Feedback value P with active power e The difference enters a PI regulator, the output of the PI regulator is used as the input of the position 1 of a gating switch S1, the input of the position 2 of a gating switch S1 is 0, the output G1 of an island detection module is used as a control signal of a gating switch S1, the output of the control signal of a gating switch S1 is position 1 when the control signal of the gating switch S1 is 0, the output of the control signal of a gating switch S1 is position 2 when the control signal of the gating switch S1 is 1, and the initial position of the gating switch S1 is position 1; output of gate switch S1 and rated value I of DC side current dcN The sum is the reference value i of the direct current side current dcref ，i dcref Feedback value i of DC side current dc The difference enters a PI regulator, and the output of the PI regulator generates a trigger pulse s of a pre-converter through a modulation module e (ii) a Feedback value i of direct current side current dc Multiplying 100 pi by the reference value i of the DC side current dcref Equal to angular frequency omega in ，ω in The output after the angular frequency amplitude limiting link is omega out ，ω out The output after the integration link is phase theta; filter capacitor voltage u of AC side CL type filter Cabc Converted into u by rotating dq Cd 、u Cq The phase used to rotate the dq transformation is θ; reference value U of grid-connected point voltage amplitude pref Feedback value U of voltage amplitude of grid-connected point p The difference is multiplied by a gain K p The output of which is the d-axis reference value u of the filter capacitor voltage Cdref Q-axis reference u of filter capacitor voltage Cqref Is 0; d-axis reference u of filter capacitor voltage Cdref And a feedback value u Cd The difference enters a PI regulator, and the output of the PI regulator is the d-axis component of the modulation current of the current source type converter
Figure FDA0003683635430000011
Q-axis reference u of filter capacitor voltage Cqref And a feedback value u Cq The difference enters a PI regulator, and the output of the PI regulator is the q-axis component of the modulation current of the current source type converter
Figure FDA0003683635430000012
And
Figure FDA0003683635430000013
after entering the current amplitude generating module, the amplitude I of the modulation current of the current source type converter is generated g ，I g Entering a current amplitude limiting link; feedback value i of direct current side current dc Entering a damping injection module with output I z Output I of current limiting link gout The sum is the current amplitude I t Amplitude of current I t The phase theta is connected with the modulation current generation module to generate the modulation current of the current source type converter
Figure FDA0003683635430000014
Generating trigger pulse s of current source type converter after entering modulation module gabc 。
2. The on-grid and off-grid switching control method of the two-stage energy storage converter according to claim 1, wherein the angular frequency limiting link outputs ω out And input omega in Have the following relationship between:
Figure FDA0003683635430000015
3. the on-grid and off-grid switching control method of the two-stage energy storage converter according to claim 1, wherein the current limiting link outputs I gout And input I g Have the following relationship between:
Figure FDA0003683635430000021
in the formula (2), I gN The current amplitude rating is modulated for a current source converter.
4. The grid-connected and grid-disconnected switching control method of the two-stage energy storage converter according to claim 1, wherein the output I of the damping injection module z And input i dc Have the following relationship between:
Figure FDA0003683635430000022
in formula (3), s is Laplace operator, T is high-pass filter time constant, and K dc Is a high-pass filter gain;
the high-pass filter time constant T and the high-pass filter gain K dc The following relationship is satisfied:
0.001≤T≤1 (4)
Figure FDA0003683635430000023
in the formula (5), I dcN Is the rated value of the direct current side current.
5. The grid-connected and grid-disconnected switching control method of the two-stage energy storage converter according to claim 1, wherein the islanding detection module adopts the following stepsThe control method comprises the following steps: generating a flag bit G according to the saturation time of the angular frequency amplitude limiting link ω When the saturation time of the angular frequency amplitude limiting link is less than or equal to 0.05s, the flag bit G ω Is 0, when the saturation time of the angular frequency amplitude limiting link is more than 0.05s, the flag bit G ω Has a value of 1; generating a flag bit G according to the saturation time of the current amplitude limiting link i When the saturation time of the current amplitude limiting link is less than or equal to 0.08s, the flag bit G i Is 0, and when the saturation time of the current amplitude limiting link is more than 0.08s, the flag bit G i Has a value of 1; generating a flag bit G according to the absolute value of the DC side current deviation dc When the absolute value of the deviation of the direct current side current is divided by the rated value of the direct current side current and is less than or equal to 0.05, the flag bit G dc Is 0, and when the absolute value of the deviation of the DC side current divided by the rated value of the DC side current is greater than 0.05, the flag G dc Has a value of 1; flag bit G i The output of the falling edge Delayer1 and a flag G pass through a falling edge Delayer1 ω Entering a logic AND operation module, the output of the logic AND operation module is a flag bit G after passing through a falling edge Delayer2 s (ii) a Flag bit G s And flag bit G dc And entering a logic OR operation module, wherein the output of the logic OR operation module is the output G1 of the island detection module.
6. The control system based on the grid-connected and off-grid switching control method of the two-stage energy storage converter as claimed in any one of claims 1 to 5, comprises a pre-stage converter directly connected with energy storage and a current source type converter connected with a power grid; the pre-stage converter is a bidirectional direct current/direct current converter, one side of the pre-stage converter is connected with the energy storage battery, and the other side of the pre-stage converter is connected with the current source type converter through an inductor; the current source type converter is a bidirectional direct current/alternating current converter, the direct current side of the current source type converter is connected with the pre-stage converter through an inductor, and the alternating current side of the current source type converter is connected to a grid-connected point through a CL type filter; the Load is connected to a grid-connected point, and the grid-connected point is connected to a power grid through a breaker BRK.
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CN113964876A (en) * 2021-11-29 2022-01-21 南通大学 Full-power conversion wind turbine generator control system containing energy storage and control method thereof
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