CN116846202A - Negative sequence current suppression system and method based on network construction type converter - Google Patents

Negative sequence current suppression system and method based on network construction type converter Download PDF

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Publication number
CN116846202A
CN116846202A CN202310832983.4A CN202310832983A CN116846202A CN 116846202 A CN116846202 A CN 116846202A CN 202310832983 A CN202310832983 A CN 202310832983A CN 116846202 A CN116846202 A CN 116846202A
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China
Prior art keywords
negative sequence
phase
sequence component
value
voltage
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王亮
张曦
王桢
徐斌
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Beijing Institute of Technology BIT
Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd
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Beijing Institute of Technology BIT
Electric Power Research Institute of State Grid Anhui Electric Power Co Ltd
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Publication of CN116846202A publication Critical patent/CN116846202A/en
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    • 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
    • H02M1/00—Details of apparatus for conversion
    • H02M1/12—Arrangements for reducing harmonics from ac input or output
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
    • H02H9/00—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection
    • H02H9/02—Emergency protective circuit arrangements for limiting excess current or voltage without disconnection responsive to excess current
    • 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
    • H02J3/01—Arrangements for reducing harmonics or ripples
    • 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
    • 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
    • Y02E40/50—Arrangements for eliminating or reducing asymmetry in polyphase networks

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)

Abstract

The invention discloses a negative sequence current suppression system and method based on a network construction type converter, and relates to the technical field of grid-connected converters. The negative sequence current feedback module comprises: the first filtering unit filters the three-phase output current to obtain a negative sequence component instantaneous value; the amplifying unit amplifies the negative sequence component instantaneous value to obtain an amplified negative sequence component instantaneous value; the difference unit calculates the difference between the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a second voltage reference value; the negative sequence voltage feedforward control module comprises: the second filtering unit filters the three-phase system voltage to obtain a three-phase negative sequence component; and the summation unit performs summation calculation on the second voltage reference value and the three-phase negative sequence component to obtain a third voltage reference value. The invention reduces the negative sequence component in the output current of the converter and improves the running stability of the converter and the power system.

Description

Negative sequence current suppression system and method based on network construction type converter
Technical Field
The invention relates to the technical field of grid-connected converters, in particular to a negative sequence current suppression system and method based on a network construction type converter.
Background
Currently, most practical grid-connected converters adopt a network tracking (tracking) type control strategy. The basic principle is that a phase-locked loop (phase locked loop, PLL) is utilized to track the system voltage phase of the grid-connected point of the grid-connected converter, and a decoupled current tracking control strategy is utilized to respectively control active current and reactive current which are injected into or flow out of a power grid, which is equivalent to a three-phase current source.
On the one hand, the grid-connected control strategy decouples the active power and reactive power output by the grid-connected converter from the running state of the power grid, which is unfavorable for the frequency stability and the voltage stability of the power system.
On the other hand, there is strong coupling between the output of the phase-locked loop and the grid, which reduces the anti-interference stability of the grid-connected converter when it is incorporated into a weak system. With the continuous increase of the total capacity of the power electronic device, especially the installed capacity of new energy, the influence of the grid-connected converter on the stability of the power system is increasingly obvious.
In order to solve the problem of the following-net type converter, a network-structured (net-structured) converter has been proposed. The network-structured converter does not need a phase-locked loop, and can realize self-synchronization with a power grid. Meanwhile, the output characteristic of the power system can be equivalent to a three-phase voltage source, and the power system can work normally in isolated grid and grid-connected modes, so that the power system is beneficial to frequency support and voltage support, and the power system has been preliminarily applied to actual engineering. However, the grid-structured converter has a problem that the negative sequence component in the output current is high.
The reason for this is that: 1) Due to the control precision of pulse width modulation (Pulse width modulation, PWM) driving, asymmetric element parameters and other reasons, a slight asymmetric phenomenon may occur in the three-phase system voltage and the three-phase output current of the grid-type converter during normal operation, that is, a small amount of negative sequence components exist in the three-phase system voltage and the three-phase output current; 2) When the power system has an asymmetric fault, the system voltage at the outlet of the grid-connected converter is seriously asymmetric, and the grid-connected converter can only output positive sequence voltage, so that a negative sequence component with larger amplitude exists in the output current, and the grid-connected converter is over-current under partial working conditions, thereby causing adverse effects on the stable operation of the converter and the power system.
Disclosure of Invention
The embodiment of the invention aims to provide a negative sequence current suppression system and method based on a network construction type converter, so as to reduce the negative sequence component of the output current of the converter and improve the operation stability of the converter and a power system.
In order to achieve the above object, the embodiment of the present invention provides the following solutions:
the negative sequence current suppression system based on the network construction type converter comprises a grid-connected converter construction type control system, a negative sequence current feedback module and a negative sequence voltage feedforward control module;
the grid-connected converter grid-structured control system outputs three-phase output current;
the negative sequence current feedback module comprises:
the first filtering unit is used for filtering the three-phase output current to obtain a negative sequence component instantaneous value; the negative sequence component instantaneous value comprises any one phase of negative sequence component instantaneous value in the three-phase output current;
the amplifying unit is connected with the first filtering unit and is used for amplifying the negative sequence component instantaneous value to obtain an amplified negative sequence component instantaneous value;
the difference value unit is connected with the amplifying unit and is used for carrying out difference value calculation on the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value; the difference value is a second voltage reference value;
the negative sequence voltage feedforward control module comprises:
the second filtering unit is used for filtering the three-phase system voltage of the grid-connected point of the grid-connected converter to obtain three-phase negative sequence components; the three-phase negative sequence component comprises any one phase of negative sequence component in the three-phase system voltage;
the summing unit is connected with the second filtering unit and is used for carrying out summation calculation on the first voltage reference value and the three-phase negative sequence component to obtain a sum value; the sum is a third voltage reference.
Optionally, the negative sequence voltage feedforward control module further includes:
the judging unit is connected with the second filtering unit and is used for judging the line voltage effective value of the three-phase negative sequence component and the magnitude of a preset threshold value;
outputting the second voltage reference value if the line voltage effective value of the three-phase negative sequence component is smaller than or equal to the preset threshold value;
and if the line voltage effective value of the three-phase negative sequence component is larger than the preset threshold value, outputting the third voltage reference value.
Optionally, the first filtering unit includes:
the first Park conversion sub-module is used for carrying out Park conversion on the three-phase output current to obtain a converted three-phase output current;
the first filter is connected with the first Park conversion submodule and is used for filtering the converted three-phase output current to obtain a filtered three-phase output current;
and the first Park inverse transformation submodule is connected with the first filter and is used for carrying out Park transformation on the three-phase output current after filtering again to obtain the negative sequence component instantaneous value.
Optionally, the second filtering unit includes:
the second Park conversion sub-module is used for carrying out Park conversion on the three-phase system voltage to obtain a converted three-phase system voltage;
the second filter is connected with the second Park conversion submodule and is used for filtering the converted three-phase system voltage to obtain a filtered three-phase system voltage;
and the second Park inverse transformation submodule is connected with the second filter and is used for carrying out Park transformation on the filtered three-phase system voltage again to obtain the three-phase negative sequence component.
Optionally, the line voltage effective value calculation formula of the three-phase negative sequence component is:
wherein u is neg Line voltage effective value representing three-phase negative sequence component, u a_neg Representing the instantaneous value of the negative sequence component of phase a, u b_neg Representing the instantaneous value of the negative sequence component of phase b, u c_neg Representing the instantaneous value of the negative sequence component of phase c.
In order to achieve the above purpose, the embodiment of the present invention further provides the following solutions:
the negative sequence current suppression method based on the network construction type converter comprises the following steps of:
acquiring three-phase output current, and filtering the three-phase output current to obtain a negative sequence component instantaneous value; the grid-connected converter grid-structured control system outputs the three-phase output current; the negative sequence component instantaneous value comprises any one phase of negative sequence component instantaneous value in the three-phase output current;
amplifying the negative sequence component instantaneous value to obtain an amplified negative sequence component instantaneous value;
calculating a difference value between the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value; the difference value is a second voltage reference value;
acquiring a three-phase system voltage, and filtering the three-phase system voltage to obtain a three-phase negative sequence component; the three-phase negative sequence component comprises any one phase negative sequence component instantaneous value in the three-phase system voltage;
summing the first voltage reference value and the three-phase negative sequence component to obtain a sum value; the sum is a third voltage reference.
Optionally, the negative sequence current suppression method based on the network construction type converter further comprises the following steps:
judging the line voltage effective value of the three-phase negative sequence component and the magnitude of a preset threshold value;
outputting the second voltage reference value if the line voltage effective value of the three-phase negative sequence component is smaller than or equal to the preset threshold value;
and if the line voltage effective value of the three-phase negative sequence component is larger than the preset threshold value, outputting the third voltage reference value.
Optionally, the filtering the three-phase output current to obtain the negative sequence component instantaneous value specifically includes:
performing Park conversion on the three-phase output current to obtain a converted three-phase output current;
filtering the converted three-phase output current to obtain a filtered three-phase output current;
and performing Park inverse transformation on the three-phase output current after filtering to obtain the negative sequence component instantaneous value.
Optionally, filtering the three-phase system voltage to obtain a three-phase negative sequence component specifically includes:
performing Park conversion on the three-phase system voltage to obtain a converted three-phase system voltage;
filtering the transformed three-phase system voltage to obtain a filtered three-phase system voltage;
and performing Park inverse transformation on the filtered three-phase system voltage to obtain the three-phase negative sequence component.
Optionally, the line voltage effective value calculation formula of the three-phase negative sequence component is:
wherein u is neg Line voltage effective value representing three-phase negative sequence component, u a_neg Representing the instantaneous value of the negative sequence component of phase a, u b_neg Representing the instantaneous value of the negative sequence component of phase b, u c_neg Representing the instantaneous value of the negative sequence component of phase c.
In the embodiment of the invention, a negative sequence current feedback module and a negative sequence voltage feedforward control module are added on the basis of a grid-connected converter grid-connected control system based on a negative sequence current suppression system of a network-structured converter.
The negative sequence current feedback module comprises: the device comprises a first filtering unit, an amplifying unit and a difference unit.
The first filtering unit is used for filtering the three-phase output current to obtain a negative sequence component instantaneous value. The amplifying unit amplifies the negative sequence component instantaneous value to obtain the amplified negative sequence component instantaneous value. The difference unit calculates the difference between the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value; the difference is a second voltage reference. The negative sequence current feedback module can inhibit the generation of negative sequence current in a normal working state caused by factors such as PWM driving control precision of the grid-connected converter, parameter asymmetry of three-phase elements of the power system and the like, and reduces the negative sequence component output by the grid-connected converter.
The negative sequence voltage feedforward control module comprises: a second filtering unit and a summing unit.
And the second filtering unit filters the three-phase system voltage to obtain a three-phase negative sequence component. The summation unit performs summation calculation on the first voltage reference value and the three-phase negative sequence component to obtain a summation value; the sum value is a third voltage reference value. The negative sequence voltage feedforward control module enables the output voltage of the grid-connected converter to contain the negative sequence component which is the same as the three-phase system voltage on the basis of the negative sequence current feedback module, thereby preventing the negative sequence current from flowing into or flowing out of the grid-connected converter, further reducing the negative sequence current output by the grid-connected converter when the power system has an asymmetric fault, and improving the running stability of the grid-connected converter and the power system.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic structural diagram of a negative sequence current suppression system based on a network-structured converter according to an embodiment of the present invention;
FIG. 2 is a schematic waveform diagram of a three-phase output current according to an embodiment of the present invention;
FIG. 3 is a schematic waveform diagram of a second voltage reference value according to an embodiment of the present invention;
FIG. 4 is a schematic waveform diagram of a three-phase system voltage according to an embodiment of the present invention;
FIG. 5 is a schematic diagram of waveforms of currents output by a grid-connected inverter grid-formation control system according to an embodiment of the present invention;
FIG. 6 is a schematic diagram of waveforms of currents output by the negative sequence current feedback module according to an embodiment of the present invention;
FIG. 7 is a schematic waveform diagram of a negative sequence voltage feedforward control module according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of a first filtering unit according to an embodiment of the present invention;
fig. 9 is a flow chart of a negative sequence current suppression method based on a network configuration type converter according to an embodiment of the present invention.
Symbol description:
the system comprises a negative sequence current suppression system-1 based on a network construction type converter, a negative sequence current feedback module-11, a first filtering unit-111, an amplifying unit-112, a negative sequence voltage feedforward control module-12, a second filtering unit-121, a judging unit-122 and a grid-connected type converter construction type control system-2.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
With the acceleration of the construction of a novel power system, the development trend of high-proportion new energy and high-proportion power electronic equipment of the power system is increasingly obvious. The new energy units such as photovoltaic power generation, wind power generation and the like are all integrated into a power grid through a power electronic converter, and the devices such as electrochemical energy storage, flywheel energy storage and the like in the power system are also integrated into the power grid through the power electronic converter.
The negative sequence current suppression system of the network structure type converter directly generates the phase and amplitude of the output voltage of the converter according to the set active power and reactive power, and the phase and amplitude are equivalent to a controllable three-phase voltage source, similar to a synchronous generator. The network structure type converter does not depend on power grid frequency/phase measurement to realize frequency/phase synchronization, so that the regulation of frequency and voltage in a weak power grid is more flexible, and the stable operation of a power system is facilitated. In the power system with high proportion of new energy, the system strength is reduced due to the reduction of synchronous generators, and the converter is more suitable to adopt a net-structured control mode, so that the frequency stability and the voltage stability of the system are enhanced. The network-structured converter realizes system synchronization according to the active power of the equipment, and does not depend on the phase of a power grid. Therefore, the system can work normally in isolated network and grid-connected modes.
Fig. 1 shows an exemplary structure of the negative sequence current suppression system based on the network configuration type converter described above. At least comprises: the device comprises a negative sequence current feedback module 11, a first filtering unit 111, an amplifying unit 112, a difference unit, a negative sequence voltage feedforward control module 12, a second filtering unit 121 and a summation unit. The modules are described in detail below.
The negative sequence current suppression system 1 based on the network structure type converter is added with a negative sequence current feedback module 11 and a negative sequence voltage feedforward control module 12 on the basis of the grid-connected type converter structure type control system 2.
The grid-connected converter grid-structured control system 2 outputs three-phase output current;
the negative sequence current feedback module 11 includes at least: a first filtering unit 111, an amplifying unit 112, and a difference unit.
The first filtering unit 111 is configured to filter the three-phase output current to obtain a negative sequence component instantaneous value; the negative sequence component instantaneous value comprises any one phase negative sequence component instantaneous value in the three-phase output current.
In one example, the three-phase output current i of the inverter is extracted using the first filtering unit 111 abc_out The negative sequence component instantaneous value (negative sequence current component instantaneous value) in (a) a (b). The grid-connected inverter grid-structured control system 2 outputs three-phase output currents (for example, a-phase, b-phase and c-phase), please refer to fig. 2, the ordinate is the magnitude of the three-phase output current, the abscissa is the time, and the three curves are in one-to-one correspondence with the three-phase output current.
The amplifying unit 112 is connected to the first filtering unit 111, and the amplifying unit 112 is configured to amplify the negative sequence component instantaneous value to obtain an amplified negative sequence component instantaneous value.
In one example, the amplifying unit 112 may be specifically an amplifier.
The difference unit is connected with the amplifying unit 112, and is used for performing difference calculation on the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value; the difference value is the second voltage reference value u abc_ref1 。
Referring to fig. 3, the abscissa indicates time and the ordinate indicates voltage.
In one example, if the reactance of any one phase (e.g., a phase) of the power system transmission line is slightly greater than the reactance of the other two phases (e.g., b phase and c phase), the transmission line parameters are not equal in three phases. Although the output voltage of the converter is three-phase symmetrical, the output current still has slight asymmetry, and after the negative sequence current feedback is counted, the output voltage of the converter becomes slightly asymmetrical, so that the influence of the parameter asymmetry of the transmission line or other factors causing the asymmetry of the output current is counteracted, and the content of the negative sequence current in the power system is reduced.
First voltage reference value u abc_ref The amplified negative sequence component instantaneous value (e.g., a phase) is subtracted (e.g., a phase) to obtain a new three-phase voltage reference value as a second voltage reference value (e.g., a phase). For the detailed calculation of the second voltage reference values of the b-phase and the c-phase, please refer to the above, and a detailed description is omitted herein. The difference calculation between the first voltage reference value and the amplified negative sequence component instantaneous value does not involve a unit, but only a numerical calculation.
First voltage reference value u abc_ref Comprises a phase a output voltage reference value u a_ref1 B-phase output voltage reference u b_ref1 And c-phase output voltage reference u c_ref1 。
The negative sequence voltage feedforward control module 12 includes at least: a second filtering unit 121, a summing unit.
The second filtering unit 121 is configured to filter the three-phase system voltage at the grid-connected point of the grid-connected transformer to obtain a three-phase negative sequence component; the three-phase negative sequence component comprises any one phase negative sequence component in the three-phase system voltage.
In one example, the second filtering unit 121 is utilized to filter the three-phase system voltage u abc_sys Filtering to obtain three-phase negative sequence component u abc_neg . The grid-connected inverter grid-formation control system 2 outputs three-phase system voltages (for example, a-phase, b-phase and c-phase), please refer to fig. 4, the abscissa is time, the ordinate is three-phase system voltage, and the three curves are in one-to-one correspondence with the three-phase system voltages.
The summing unit is connected to the second filtering unit 121 for comparing the first voltage reference value u abc_ref0 And a three-phase negative sequence component u abc_neg A summation calculation is performed so that,obtaining a sum value; the sum is the third voltage reference value u abc_ref2 。
In one example, the summing unit is configured to sum the first voltage reference value u abc_ref0 Any one phase (e.g., a-phase) and a three-phase negative sequence component u abc_neg Summing the corresponding phases (for example, a phase) to obtain a sum value; and the sum value is the corresponding third voltage reference value u abc_ref2 (e.g., phase a).
Referring to fig. 5, when an asymmetric short-circuit fault occurs in the power system, the grid-connected inverter constructs three-phase output current i of the grid-connected control system 2 abc_out There may be a negative sequence component of great magnitude which may cause overcurrent, damaging the device. At this time, if only the negative sequence current feedback module 11 is adopted, the magnitude of the negative sequence current is obviously suppressed, but still obvious, please refer to fig. 6. Adding a negative sequence voltage feedforward control module 12, and outputting three-phase output current i abc_out The negative sequence component in (b) is reduced to almost zero, see fig. 7.
In summary, the first filtering unit 111 is configured to filter the three-phase output current to obtain the negative sequence component instantaneous value. The amplifying unit 112 amplifies the negative sequence component instantaneous value to obtain an amplified negative sequence component instantaneous value. The difference unit calculates the difference between the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value; the difference is a second voltage reference. The negative sequence current feedback module 11 can inhibit the generation of negative sequence current in a normal working state caused by factors such as PWM driving control precision of the grid-connected converter and parameter asymmetry of three-phase elements of the power system, and reduce the negative sequence component output by the grid-connected converter, see fig. 6.
The second filtering unit 121 filters the three-phase system voltage to obtain a three-phase negative sequence component. The summation unit performs summation calculation on the first voltage reference value and the three-phase negative sequence component to obtain a summation value; the sum value is a third voltage reference value. The negative sequence voltage feedforward control module 12 makes the output voltage of the grid-connected converter have the same negative sequence component as the three-phase system voltage on the basis of the negative sequence current feedback module 11, thereby preventing the negative sequence current from flowing into or flowing out of the grid-connected converter, further reducing the negative sequence current output by the grid-connected converter when the power system has an asymmetric fault, and improving the running stability of the grid-connected converter and the power system, as shown in fig. 7.
In other embodiments of the present invention, the negative sequence voltage feedforward control module 12 further includes: the determination unit 122.
The determining unit 122 is connected to the second filtering unit 121, and the determining unit 122 is configured to determine the line voltage effective value of the three-phase negative sequence component and the magnitude of the preset threshold.
And if the line voltage effective value of the three-phase negative sequence component is smaller than or equal to a preset threshold value, outputting a second voltage reference value.
And if the line voltage effective value of the three-phase negative sequence component is larger than a preset threshold value, outputting a third voltage reference value.
In one example, a person skilled in the art may flexibly design the preset threshold, for example, the preset threshold is 3% of the three-phase output voltage rated value, the preset threshold is 5% of the three-phase output voltage rated value, the preset threshold is 8% of the three-phase output voltage rated value, and so on, which will not be described herein.
In other embodiments of the present invention, the first filtering unit 111 includes at least: the first Park conversion sub-module, the first filter and the first Park inverse conversion sub-module.
The first Park conversion sub-module is used for carrying out Park conversion on the three-phase output current to obtain a converted three-phase output current.
The first filter is connected with the first Park conversion submodule and is used for filtering the converted three-phase output current to obtain a filtered three-phase output current.
The first Park inverse transformation submodule is connected with the first filter and is used for carrying out Park inverse transformation on the three-phase output current after filtering to obtain a negative sequence component instantaneous value.
In one example, the first filter may be specifically classified into a band-stop filter and a low-pass filter. The frequency threshold of the band-stop filter is 100Hz, and the frequency range of the low-pass filter is 250-1000 Hz.
Referring to fig. 8, after the three-phase output current is input into the first Park conversion sub-module, the three-phase output current after the first Park conversion is obtained. The three-phase output current after transformation is filtered for the first time by a band-stop filter of 100Hz, and then is filtered for the second time by a low-pass filter of 250-1000 Hz, so as to obtain the three-phase output current after filtration. And obtaining a negative sequence component instantaneous value after the filtered three-phase output current is subjected to Park conversion for the second time by the first Park inverse conversion sub-module.
In another example, the negative value- θ (-120 degrees) of the positive sequence three-phase output voltage phase angle of the power system is utilized to carry out Park conversion on the three-phase output voltage instantaneous value, and after the obtained d-axis and q-axis voltage signals pass through a 100Hz band-stop filter and another low-pass filter, the negative value- θ is utilized to carry out Park reverse conversion, so that the three-phase negative sequence component instantaneous value can be obtained.
In other embodiments of the present invention, the second filtering unit 121 includes at least: the second Park conversion sub-module, the second filter and the second Park inverse conversion sub-module.
And the second Park conversion sub-module is used for carrying out Park conversion on the three-phase system voltage to obtain the converted three-phase system voltage.
The second filter is connected with the second Park conversion sub-module and is used for filtering the converted three-phase system voltage to obtain the filtered three-phase system voltage.
The second Park inverse transformation sub-module is connected with the second filter and is used for carrying out Park inverse transformation on the filtered three-phase system voltage to obtain a three-phase negative sequence component.
In an example, please refer to the first filtering unit 111 above for the detailed description of the second filtering unit 121, which is not described herein.
In other embodiments of the present invention, the line voltage effective value of the three-phase negative sequence component is calculated as:
wherein u is neg Representing three-phase negativeLine voltage effective value of sequence component, u a_neg Representing the instantaneous value of the negative sequence component of phase a, u b_neg Representing the instantaneous value of the negative sequence component of phase b, u c_neg Representing the instantaneous value of the negative sequence component of phase c.
In order to achieve the above purpose, the embodiment of the present invention further provides the following solutions:
referring to fig. 9, a negative sequence current suppression method based on a network-structured converter, a negative sequence current suppression system based on a network-structured converter, includes:
step 1: and acquiring three-phase output current, and filtering the three-phase output current to obtain a negative sequence component instantaneous value. The grid-connected converter grid-structured control system outputs three-phase output current; the negative sequence component instantaneous value comprises any one phase negative sequence component instantaneous value in the three-phase output current.
Step 1 may be performed by the first filtering unit 111, and the detailed description of the first filtering unit 111 is referred to above, which is not repeated herein.
Step 2: amplifying the negative sequence component instantaneous value to obtain the amplified negative sequence component instantaneous value.
Step 2 may be performed by the amplifying unit 112, and the detailed description of the amplifying unit 112 is referred to the above, and is not repeated herein.
Step 3: and performing difference calculation on the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value. The difference is a second voltage reference.
Step 3 may be performed by the aforementioned difference unit, and the detailed description of the difference unit is referred to the foregoing, and is not repeated herein.
Step 4: and acquiring three-phase system voltage, and filtering the three-phase system voltage of the grid-connected point of the grid-connected converter to obtain three-phase negative sequence components. The three-phase negative sequence component comprises an instantaneous value of any one phase negative sequence component in the three-phase system voltage.
Step 4 may be performed by the second filtering unit 121, and the detailed description of the second filtering unit 121 is referred to above, which is not repeated herein.
Step 5: and carrying out summation calculation on the first voltage reference value and the three-phase negative sequence component to obtain a summation value. The sum value is a third voltage reference value.
Step 5 may be performed by the aforementioned summing unit, and the detailed description of the summing unit is referred to the foregoing, and is not repeated herein.
In other embodiments of the present invention, the negative sequence current suppression method based on the network configuration type converter further includes:
step 6: and judging the line voltage effective value of the three-phase negative sequence component and the magnitude of a preset threshold value.
And if the line voltage effective value of the three-phase negative sequence component is smaller than or equal to a preset threshold value, outputting a second voltage reference value.
And if the line voltage effective value of the three-phase negative sequence component is larger than a preset threshold value, outputting a third voltage reference value.
Step 6 may be performed by the aforementioned determination unit 122, and the detailed description of the determination unit 122 is referred to above, which is not repeated herein.
In other embodiments of the present invention, filtering the three-phase output current to obtain the negative sequence component instantaneous value specifically includes:
step 11: and performing Park conversion on the three-phase output current to obtain a converted three-phase output current.
Step 11 may be performed by the aforementioned first Park transformation submodule, and reference is made to the foregoing for detailed description of the first Park transformation submodule, which is not repeated herein.
Step 12: and filtering the converted three-phase output current to obtain a filtered three-phase output current.
Step 12 may be performed by the first filter, and the detailed description of the first filter is referred to above, which is not repeated herein.
Step 13: and performing Park inverse transformation on the three-phase output current after filtering to obtain a negative sequence component instantaneous value.
Step 13 may be performed by the aforementioned first Park inverse transform sub-module, and the detailed description of the first Park inverse transform sub-module is referred to above, and is not repeated herein.
In other embodiments of the present invention, filtering the three-phase system voltage to obtain the three-phase negative sequence component specifically includes:
step 41: and performing Park conversion on the three-phase system voltage to obtain a converted three-phase system voltage.
Step 41: the second Park conversion sub-module may be executed by the aforementioned second Park conversion sub-module, and the detailed description of the second Park conversion sub-module is referred to above, and is not repeated herein.
Step 42: and filtering the converted three-phase system voltage to obtain a filtered three-phase system voltage.
Step 42 may be performed by the second filter, and the detailed description of the second filter is referred to above, which is not repeated herein.
Step 43: and performing Park inverse transformation on the three-phase system voltage after filtering to obtain a three-phase negative sequence component.
Step 43 may be performed by the aforementioned second Park inverse transform sub-module, and the detailed description of the second Park inverse transform sub-module is referred to above, and is not repeated herein.
In other embodiments of the present invention, the line voltage effective value of the three-phase negative sequence component is calculated as:
wherein u is neg Line voltage effective value representing three-phase negative sequence component, u a_neg Representing the instantaneous value of the negative sequence component of phase a, u b_neg Representing the instantaneous value of the negative sequence component of phase b, u c_neg Representing the instantaneous value of the negative sequence component of phase c.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the system disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
The principles and implementations of the embodiments of the present invention have been described herein with reference to specific examples, the description of the above examples being only for the purpose of aiding in the understanding of the methods of the embodiments of the present invention and the core ideas thereof; also, it is within the spirit of the embodiments of the present invention for those skilled in the art to vary from one implementation to another and from application to another. In view of the foregoing, this description should not be construed as limiting the embodiments of the invention.

Claims (10)

1. The negative sequence current suppression system based on the network construction type converter is characterized by comprising a grid-connected converter construction type control system, a negative sequence current feedback module and a negative sequence voltage feedforward control module;
the grid-connected converter grid-structured control system is used for outputting three-phase output current;
the negative sequence current feedback module comprises:
the first filtering unit is used for filtering the three-phase output current to obtain a negative sequence component instantaneous value; the negative sequence component instantaneous value comprises any one phase of negative sequence component instantaneous value in the three-phase output current;
the amplifying unit is connected with the first filtering unit and is used for amplifying the negative sequence component instantaneous value to obtain an amplified negative sequence component instantaneous value;
the difference value unit is connected with the amplifying unit and is used for carrying out difference value calculation on the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value; the difference value is a second voltage reference value;
the negative sequence voltage feedforward control module comprises:
the second filtering unit is used for filtering the three-phase system voltage of the grid-connected point of the grid-connected converter to obtain three-phase negative sequence components; the three-phase negative sequence component comprises any one phase of negative sequence component in the three-phase system voltage;
the summing unit is connected with the second filtering unit and is used for carrying out summation calculation on the first voltage reference value and the three-phase negative sequence component to obtain a sum value; the sum is a third voltage reference.
2. The network-based converter negative-sequence current suppression system of claim 1, wherein the negative-sequence voltage feedforward control module further includes:
the judging unit is connected with the second filtering unit and is used for judging the line voltage effective value of the three-phase negative sequence component and the magnitude of a preset threshold value;
outputting the second voltage reference value if the line voltage effective value of the three-phase negative sequence component is smaller than or equal to the preset threshold value;
and if the line voltage effective value of the three-phase negative sequence component is larger than the preset threshold value, outputting the third voltage reference value.
3. The negative sequence current suppression system based on a network construction type converter according to claim 1, wherein the first filtering unit comprises:
the first Park conversion sub-module is used for carrying out Park conversion on the three-phase output current to obtain a converted three-phase output current;
the first filter is connected with the first Park conversion submodule and is used for filtering the converted three-phase output current to obtain a filtered three-phase output current;
and the first Park inverse transformation sub-module is connected with the first filter and is used for carrying out Park inverse transformation on the three-phase output current after filtering to obtain the negative sequence component instantaneous value.
4. The negative sequence current suppression system based on a network construction type converter according to claim 1, wherein the second filtering unit comprises:
the second Park conversion sub-module is used for carrying out Park conversion on the three-phase system voltage to obtain a converted three-phase system voltage;
the second filter is connected with the second Park conversion submodule and is used for filtering the converted three-phase system voltage to obtain a filtered three-phase system voltage;
and the second Park inverse transformation sub-module is connected with the second filter and is used for carrying out Park inverse transformation on the filtered three-phase system voltage to obtain the three-phase negative sequence component.
5. The negative sequence current suppression system based on network construction type converter according to claim 2, wherein the line voltage effective value calculation formula of the three-phase negative sequence component is:
wherein u is neg Line voltage effective value representing three-phase negative sequence component, u a_neg Representing the instantaneous value of the negative sequence component of phase a, u b_neg Representing the instantaneous value of the negative sequence component of phase b, u c_neg Representing the instantaneous value of the negative sequence component of phase c.
6. A negative sequence current suppression method based on a network-based converter, characterized in that the negative sequence current suppression system based on a network-based converter according to any one of claims 1-5 comprises:
acquiring three-phase output current, and filtering the three-phase output current to obtain a negative sequence component instantaneous value; the grid-connected converter grid-structured control system outputs the three-phase output current; the negative sequence component instantaneous value comprises any one phase of negative sequence component instantaneous value in the three-phase output current;
amplifying the negative sequence component instantaneous value to obtain an amplified negative sequence component instantaneous value;
calculating a difference value between the first voltage reference value and the amplified negative sequence component instantaneous value to obtain a difference value; the difference value is used as a second voltage reference value;
acquiring three-phase system voltage of grid-connected points of the grid-connected converter, and filtering the three-phase system voltage to obtain three-phase negative sequence components; the three-phase negative sequence component comprises any one phase negative sequence component instantaneous value in the three-phase system voltage;
summing the first voltage reference value and the three-phase negative sequence component to obtain a sum value; the sum is a third voltage reference.
7. The network-based converter negative-sequence current suppression method of claim 6, further comprising:
judging the line voltage effective value of the three-phase negative sequence component and the magnitude of a preset threshold value;
outputting the second voltage reference value if the line voltage effective value of the three-phase negative sequence component is smaller than or equal to the preset threshold value;
and if the line voltage effective value of the three-phase negative sequence component is larger than the preset threshold value, outputting the third voltage reference value.
8. The method for negative sequence current suppression based on network construction type converter according to claim 6, wherein the filtering the three-phase output current to obtain the negative sequence component instantaneous value specifically comprises:
performing Park conversion on the three-phase output current to obtain a converted three-phase output current;
filtering the converted three-phase output current to obtain a filtered three-phase output current;
and performing Park inverse transformation on the three-phase output current after filtering to obtain the negative sequence component instantaneous value.
9. The method for negative sequence current suppression based on network construction type converter according to claim 6, wherein the filtering the three-phase system voltage to obtain the three-phase negative sequence component specifically comprises:
performing Park conversion on the three-phase system voltage to obtain a converted three-phase system voltage;
filtering the transformed three-phase system voltage to obtain a filtered three-phase system voltage;
and performing Park inverse transformation on the filtered three-phase system voltage to obtain the three-phase negative sequence component.
10. The negative sequence current suppressing method based on a network configuration type converter according to claim 7, wherein the line voltage effective value calculation formula of the three-phase negative sequence component is:
wherein u is neg Line voltage effective value representing three-phase negative sequence component, u a_neg Representing the instantaneous value of the negative sequence component of phase a, u b_neg Representing the instantaneous value of the negative sequence component of phase b, u c_neg Representing the instantaneous value of the negative sequence component of phase c.
CN202310832983.4A 2023-04-04 2023-07-10 Negative sequence current suppression system and method based on network construction type converter Pending CN116846202A (en)

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