CN116316777A - LCC-HVDC operation range determining method and device - Google Patents

LCC-HVDC operation range determining method and device Download PDF

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CN116316777A
CN116316777A CN202310203521.6A CN202310203521A CN116316777A CN 116316777 A CN116316777 A CN 116316777A CN 202310203521 A CN202310203521 A CN 202310203521A CN 116316777 A CN116316777 A CN 116316777A
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determining
direct current
current system
parameter
voltage
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CN116316777B (en
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谢琦
郑子萱
任杰
肖先勇
李长松
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Sichuan University
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Sichuan 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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
    • H02J3/12—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load
    • H02J3/16—Circuit arrangements for ac mains or ac distribution networks for adjusting voltage in ac networks by changing a characteristic of the network load by adjustment of reactive power
    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
    • 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
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/28—The renewable source being wind energy
    • 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
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Inverter Devices (AREA)
  • Supply And Distribution Of Alternating Current (AREA)

Abstract

The invention provides a method and a device for determining the operation range of LCC-HVDC, comprising the following steps: collecting operation parameters of a direct current system and an alternating current system; judging whether the operation parameters meet a threshold range or not; if not, determining the Thevenin equivalent parameters of the communication system; acquiring a power parameter; determining the operation range of the direct current system under the synchronous stability constraint condition and the commutation failure inhibition constraint condition; and determining a control instruction of the direct current system by taking the minimum voltage deviation of the alternating current bus at the transmitting and receiving end as a target, and controlling the direct current system to operate based on the control instruction. The method can determine the operating range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after the high-proportion new energy is accessed, actively and fully exert the adjusting capability of the LCC-HVDC system to relieve the transient voltage disturbance of the transmitting and receiving end, and simultaneously inhibit the subsequent commutation failure, thereby having important significance for ensuring the safe and stable operation of the high-proportion new energy AC/DC hybrid system.

Description

LCC-HVDC operation range determining method and device
Technical Field
The invention relates to the technical field of power transmission systems, in particular to a method and a device for determining an operating range of LCC-HVDC.
Background
The conventional high-voltage direct current transmission system (Line commutated converter based high voltage direct current, LCC-HVDC) has the advantages of low cost, small loss, long transmission distance and the like, becomes one of the best choices for long-distance large-capacity power transmission, and is widely applied and rapidly developed. However, as the thyristor is adopted to form the converter valve, the LCC-HVDC is very sensitive to transient voltage disturbance of the transmitting and receiving end, such as voltage sag caused by AC short circuit fault, overvoltage caused by reactive surplus and the like, so that DC power fluctuation is caused, even phase conversion failure and blocking are caused, and serious impact is caused on safe and stable operation of an AC/DC hybrid power system. Therefore, there is a need to study the operating range of LCC-HVDC under multiple types of transient voltage disturbances, determine its operating limits, and propose a control method that actively uses LCC-HVDC regulation capability to support the voltage at the converter bus.
In the prior art, based on a short circuit ratio index (ShortCircuit Ratio, SCR), constraints of electric quantities such as direct current voltage, direct current, a rectifying side trigger angle, an inversion side arc extinction angle and the like are considered, and an accurate depiction method is provided for the running range of LCC-HVDC under steady-state conditions. However, considering the high-proportion new energy access of the transmitting end, the operation range of LCC-HVDC with transient time scale under the action of multi-type transient voltage disturbance still lacks related research. In addition, the traditional high-voltage direct-current control system adopts a low-voltage current limiting control link (Voltage Dependent Current Order Limiter, VDCOL) to limit a direct-current command when the alternating-current voltage is low, so that reactive consumption of a converter station is reduced to inhibit commutation failure, and the adjusting capability of LCC-HVDC can not be fully exerted.
Disclosure of Invention
In view of the above, the invention aims to provide a method and a device for determining the operation range of LCC-HVDC, which can determine the operation range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after high-proportion new energy is accessed, and actively and fully exert the adjustment capability of an LCC-HVDC system to relieve the transient voltage disturbance of a transmitting and receiving end, inhibit the subsequent commutation failure, and have important significance for ensuring the safe and stable operation of a high-proportion new energy alternating-current/direct-current hybrid system.
In a first aspect, an embodiment of the present invention provides a method for determining an operating range of an LCC-HVDC, the method comprising: collecting operation parameters of a direct current system and an alternating current system; judging whether the operation parameters meet a preset threshold range or not; if the operation parameters do not meet the threshold range, determining the Thevenin equivalent parameters of the alternating current system; acquiring a power parameter; wherein the power parameters include: active power and reactive power provided by an alternating current system, active power and reactive power provided by a wind farm, and reactive power provided by a reactive compensation device of a convertor station; determining a synchronous stability constraint condition and an operation range of the direct current system under a constraint condition of restraining commutation failure based on Thevenin equivalent parameters and power parameters; and determining a control instruction of the direct current system based on the minimum voltage deviation of the alternating current bus at the receiving end in the operation range of the direct current system, and controlling the direct current system to operate based on the control instruction.
In an alternative embodiment of the present application, the above-mentioned operating parameters include: the trigger angle of the rectifying side and the inverting side, the arc extinguishing angle of each converter valve of the inverting side, the direct current voltage and the direct current of the rectifying side and the inverting side, the alternating current voltage of the rectifying side and the inverting side, and the voltage and the current of the reactive compensation devices at two sides.
In an optional embodiment of the present application, the step of determining whether the operating parameter meets a preset threshold range includes: and judging whether the alternating current bus voltage at the rectifying side and the alternating current bus voltage at the inverting side meet the corresponding preset range or not, and whether the arc extinguishing angle at the inverting side is larger than a preset threshold value or not.
In an optional embodiment of the present application, after the step of determining whether the operating parameter meets the preset threshold range, the method further includes: and if the operation parameters meet the threshold range, controlling the direct current system to keep running.
In an alternative embodiment of the present application, the step of determining the Thevenin equivalent parameter of the communication system includes: collecting voltage and current of an alternating current system, and determining Thevenin equivalent parameters of the alternating current system based on the voltage and the current of the alternating current system; wherein, the Thevenin equivalent parameters include: equivalent voltage and equivalent impedance of the transmitting-end alternating current system and equivalent voltage and equivalent impedance of the receiving-end alternating current system.
In an alternative embodiment of the present application, the step of determining the operation range of the dc system under the synchronous stabilization constraint condition and the commutation failure constraint condition based on the wiener equivalent parameter and the power parameter includes: determining a power parameter of a rectifying side and a power parameter of an inverting side based on a preset quasi-steady equation; wherein, the power parameter of rectifying side includes: active power and reactive power of the rectifying side, and power parameters of the inverting side include: active power and reactive power of the inversion side; determining synchronous stability constraint conditions of the rectifying side and the inverting side based on the Thevenin equivalent parameter, the power parameter of the rectifying side and the power parameter of the inverting side; the operation range of the direct current of the rectifying side is determined based on the synchronous stabilization constraint condition of the rectifying side, the synchronous stabilization constraint condition of the inverting side and the predetermined restraint commutation failure constraint condition.
In an optional embodiment of the present application, when the above synchronous stability constraint condition meets a specified condition, the synchronous stability constraint condition is equivalent to a stability constraint condition that a short-circuit ratio index is greater than or equal to 2 in a single-feed high-voltage direct-current power transmission system; the short circuit ratio index represents the ratio of the short circuit capacity of the alternating current system to the rated direct current transmission capacity.
In an optional embodiment of the present application, the step of determining the control instruction of the dc system based on the minimum deviation of the voltage of the ac bus at the receiving end in the operating range of the dc system includes: determining an objective function; wherein the objective function is related to the direct current at the rectifying side; determining a reference current instruction minimizing an objective function as a control instruction of the direct current system based on the operation range of the direct current of the rectifying side; the minimum characteristic of the objective function is that the deviation of the voltage of the commutation bus at the rectifying side and the deviation of the voltage of the commutation bus at the inverting side are minimum in combination.
In an optional embodiment of the present application, after the step of controlling the dc system to operate based on the control instruction, the method further includes: judging whether the current operation parameters of the direct current system and the alternating current system continuously meet a threshold range; if the current operation parameters do not continuously meet the threshold range, determining Thevenin equivalent parameters of the communication system based on the current operation parameters; and if the current operation parameters continuously meet the threshold range, controlling the direct current system to keep running.
In a second aspect, an embodiment of the present invention further provides an apparatus for determining an operating range of an LCC-HVDC, the apparatus comprising: the operation parameter acquisition module is used for acquiring operation parameters of the direct current system and the alternating current system; the operation parameter judging module is used for judging whether the operation parameter meets a preset threshold range or not; the Thevenin equivalent parameter determining module is used for determining the Thevenin equivalent parameter of the communication system if the operation parameter does not meet the threshold range; the power parameter acquisition module is used for acquiring power parameters; wherein the power parameters include: active power and reactive power provided by an alternating current system, active power and reactive power provided by a wind farm, and reactive power provided by a reactive compensation device of a convertor station; the operation range determining module is used for determining the operation range of the direct current system under the synchronous stability constraint condition and the restraint commutation failure constraint condition based on the Thevenin equivalent parameter and the power parameter; and the direct current system control module is used for determining a control instruction of the direct current system based on the minimum voltage deviation of the alternating current bus at the receiving end of the operation range of the direct current system as a target, and controlling the direct current system to operate based on the control instruction.
The embodiment of the invention has the following beneficial effects:
the embodiment of the invention provides a method and a device for determining the operating range of LCC-HVDC, which can determine the operating range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after high-proportion new energy is accessed, and actively and fully exert the adjusting capability of an LCC-HVDC system to relieve the transient voltage disturbance of a transmitting and receiving end, inhibit subsequent commutation failure, and have important significance for ensuring the safe and stable operation of a high-proportion new energy alternating-current/direct-current hybrid system.
Additional features and advantages of the disclosure will be set forth in the description which follows, or in part will be obvious from the description, or may be learned by practice of the techniques of the disclosure.
The foregoing objects, features and advantages of the disclosure will be more readily apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings that are needed in the description of the embodiments or the prior art will be briefly described, and it is obvious that the drawings in the description below are some embodiments of the present invention, and other drawings can be obtained according to the drawings without inventive effort for a person skilled in the art.
Fig. 1 is a schematic diagram of a bipolar high-voltage direct-current transmission system with a wind power plant at a transmitting end according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a conventional hvdc transmission control system according to an embodiment of the present invention;
FIG. 3 is a schematic diagram of a simplified equivalent circuit of an AC/DC series-parallel system according to an embodiment of the present invention;
fig. 4 is a flowchart of a method for determining an operating range of LCC-HVDC according to an embodiment of the present invention;
fig. 5 is a flowchart of another method for determining an operating range of LCC-HVDC according to an embodiment of the present invention;
fig. 6 is a schematic diagram of a method for determining an operating range of LCC-HVDC according to an embodiment of the present invention;
fig. 7 is a schematic diagram of an ac/dc series-parallel system according to an embodiment of the present invention;
fig. 8 is a schematic structural diagram of an LCC-HVDC operation range determining device according to an embodiment of the present invention;
fig. 9 is a schematic structural diagram of an electronic device according to an embodiment of the present invention.
Detailed Description
For the purpose of making the objects, technical solutions and advantages of the embodiments of the present invention more apparent, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings, and it is apparent that the described embodiments are 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.
The conventional high-voltage direct-current transmission system has the advantages of low cost, small loss, long transmission distance and the like, becomes one of the best choices for long-distance large-capacity power transmission, and is widely applied and rapidly developed. However, as the thyristor is adopted to form the converter valve, the LCC-HVDC is very sensitive to transient voltage disturbance of the transmitting and receiving end, such as voltage sag caused by AC short circuit fault, overvoltage caused by reactive surplus and the like, so that DC power fluctuation is caused, even phase conversion failure and blocking are caused, and serious impact is caused on safe and stable operation of an AC/DC hybrid power system. Therefore, there is a need to study the operating range of LCC-HVDC under multiple types of transient voltage disturbances, determine its operating limits, and propose a control method that actively uses LCC-HVDC regulation capability to support the voltage at the converter bus.
In the prior art, based on a short circuit ratio index (ShortCircuit Ratio, SCR), constraints of electric quantities such as direct current voltage, direct current, a rectifying side trigger angle, an inversion side arc extinction angle and the like are considered, and an accurate depiction method is provided for the running range of LCC-HVDC under steady-state conditions. However, considering the high-proportion new energy access of the transmitting end, the operation range of LCC-HVDC with transient time scale under the action of multi-type transient voltage disturbance still lacks related research. In addition, the traditional high-voltage direct-current control system adopts a low-voltage current limiting control link (Voltage Dependent Current Order Limiter, VDCOL) to limit a direct-current command when the alternating-current voltage is low, so that reactive consumption of a converter station is reduced to inhibit commutation failure, and the adjusting capability of LCC-HVDC can not be fully exerted.
At present, the existing scheme only determines the running range of LCC-HVDC under steady-state conditions, and cannot accurately describe the running range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after the high-proportion new energy source at the transmitting end is accessed, and under certain conditions, the LCC-HVDC is possibly caused to exceed the safe running range to cause system instability; the existing scheme cannot fully exert the adjusting capability of the LCC-HVDC system during transient voltage disturbance and cannot support the voltage recovery of the converter bus to the greatest extent.
Based on the above, the embodiment of the invention provides a method and a device for determining the operation range of LCC-HVDC, in particular to a method for determining the operation limit of LCC-HVDC and actively supporting and controlling the LCC-HVDC under transient voltage disturbance. Firstly, establishing an equivalent model of an alternating current-direct current series-parallel system, and acquiring parameters of the equivalent model through real-time measurement and Thevenin equivalent; respectively establishing a power-voltage equation for the alternating current-direct current series-parallel system of the transmitting and receiving end, and deducing the operation range of the LCC-HVDC system under the constraint condition of synchronous stability common constraint and commutation failure inhibition of the transmitting and receiving end by combining with the LCC-HVDC quasi-steady state equation; and in the LCC-HVDC safe operation range, calculating a control instruction of the high-voltage direct-current power transmission system by taking the minimum voltage deviation of the current converting bus at the transmitting and receiving end as a target, and fully playing the active supporting role of the LCC-HVDC in the transient voltage disturbance period.
The method provided by the embodiment can determine the operation range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after the high-proportion new energy is accessed, and actively and fully exert the adjustment capability of the LCC-HVDC system to relieve the transient voltage disturbance of the transmitting and receiving end, and simultaneously is beneficial to inhibiting the subsequent commutation failure, and has important significance for ensuring the safe and stable operation of the high-proportion new energy alternating-current-direct-current hybrid system.
For the convenience of understanding the present embodiment, a detailed description will be first made of an LCC-HVDC operation range determining method disclosed in the embodiment of the present invention.
Embodiment one:
the embodiment of the invention provides an operation range determining method of LCC-HVDC, which aims at a high-voltage direct-current transmission system of a grid converter and needs to be modified according to control strategies of a rectifying station and an inverting station.
Reference may be made to a schematic diagram of a typical bi-polar hvdc transmission system for a wind farm at the delivery end shown in fig. 1 and a schematic diagram of a conventional hvdc transmission control system shown in fig. 2.
As shown in FIG. 2, I dr For rectifying side direct current, I dr_order Is a direct current command, beta rcc For rectifying the side lead firing angle alpha rcc For rectifying the side firing angle, alpha min For minimum firing angle, alpha r_order For rectifying side firing angle command, U di For dc voltage at inversion side, V dc_com To compensate for the post-voltage, I d_order A direct current instruction given to the main control layer, I di For inverting side DC current, I dr_error For current deviation, gamma iY And gamma i delta are the turn-off angles of the Y and delta valve groups respectively, CEC is a current deviation control link, sigma i,cec For CEC output, beta icc And beta cea Output quantity, beta, controlled by constant current and constant turn-off angle at inversion side respectively i_order For the inversion-side advance firing angle command, alpha i_order Is an inversion-side firing angle command. In fig. 2, min represents a small input amount, max represents a large input amount, and Min 1cycle represents a minimum value of the input amount within one cycle (20 ms).
For the convenience of explaining the technical solution of the present invention, reference may be made to a schematic diagram of a simplified equivalent circuit of an ac/dc series-parallel system shown in fig. 3. Wherein, the wind power plant and the near-zone alternating current systems except the wind power plant are all represented by Thevenin equivalent, and the equivalent voltage of the near-zone alternating current system at the transmitting end is E sr Equivalent impedance is R 1 +jX 1 ，Psr+jQ sr Representing the power supplied by an equivalent voltage source, P 1 +jQ 1 Representing the power provided by an alternating current system to a direct current system, wherein the equivalent voltage of a wind power plant is U w Equivalent impedance is R 2 +jX 2 ，P w +jQ w Representing the power supplied by a wind farm, P 2 +jQ 2 Representing the power provided by the wind power plant to the direct current system, wherein the equivalent voltage of the receiving end near-area alternating current system is E si Equivalent impedance is R 3 +jX 3 ，P si +jQ si Representing the power supplied by an equivalent voltage source, P 3 +jQ 3 Representing the power supplied by an AC system to a DC system, P dr +jQ dr Representing the power absorbed by the rectifying station, P di +jQ di Represents the power delivered by the inverter station, jQ cr And jQ ci Reactive power provided by reactive power compensation devices of rectifying station and inverting station are respectively represented, B cr And B is connected with ci Respectively the equivalent admittances of the corresponding reactive power compensation devices. U (U) pr For the voltage at the rectifying side converter bus/common Point (PCC), upi is the voltage at the inverting side converter bus, U dr 、U di And I d The direct current source is a rectifying side direct current voltage, an inverting side direct current voltage and a direct current, and Rd is a direct current line resistance.
Based on the above description, referring to a flowchart of an LCC-HVDC operation range determining method shown in fig. 4, the LCC-HVDC operation range determining method includes the steps of:
step S402, collecting operation parameters of a direct current system and an alternating current system.
In this embodiment, the operation parameters of the dc system and the operation parameters of the ac system such as voltage, current, trigger angle, arc extinction angle, etc. may be collected in real time for use in the subsequent steps.
Step S404, judging whether the operation parameters meet the preset threshold range.
After determining the operation parameters of the direct current system and the alternating current system, the embodiment can judge whether the operation parameters meet the preset threshold range, and if the operation parameters meet the threshold range, the direct current system is not required to be regulated, and the direct current system can be controlled to continue to operate. If the operating parameters do not meet the threshold range, the direct current system needs to be regulated, and the control instruction of the direct current system needs to be determined again.
In step S406, if the operating parameters do not meet the threshold range, the Thevenin equivalent parameters of the AC system are determined.
If the operation parameters do not meet the threshold range, the embodiment can estimate the Thevenin equivalent parameters of the AC system according to the AC system voltage and current acquired in real time for use in the subsequent steps.
Step S408, obtaining a power parameter; wherein the power parameters include: active and reactive power provided by the ac system, active and reactive power provided by the wind farm, and reactive power provided by the converter station reactive compensation device.
Some power parameters may also be obtained in this embodiment, including: active power and reactive power provided by the current system, active power and reactive power provided by the wind farm, reactive power provided by the reactive compensation device of the converter station, and the like, for use in subsequent steps.
Step S410, determining the operation range of the DC system under the synchronous stability constraint condition and the restraint commutation failure constraint condition based on the Thevenin equivalent parameter and the power parameter.
In this embodiment, synchronous stability constraint conditions of the rectifying side and the inverting side may be determined based on the Thevenin equivalent parameter and the power parameter calculated in the foregoing steps, and in order to avoid a subsequent commutation failure, constraint conditions for suppressing the commutation failure may be introduced in this embodiment, and the operating range of the direct current on the rectifying side may be determined jointly by the 2 constraint conditions as the operating range of the direct current system.
And step S412, determining a control command of the direct current system based on the minimum deviation of the voltage of the alternating current bus at the receiving end in the operation range of the direct current system, and controlling the direct current system to operate based on the control command.
After determining the operation range of the direct current on the rectifying side, the present embodiment may calculate a control command of the direct current system, which may also be referred to as a reference current command, considering that the deviation of the commutation bus voltage on the rectifying side is minimum and the deviation of the commutation bus voltage on the inverting side is minimum. After determining the reference current command, the present embodiment may control the dc system to operate based on the control command.
The embodiment of the invention provides a method for determining the operating range of LCC-HVDC, which can determine the operating range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after high-proportion new energy is accessed, and actively and fully exert the adjusting capability of an LCC-HVDC system to relieve the transient voltage disturbance of a transmitting and receiving end, inhibit subsequent commutation failure, and has important significance for ensuring the safe and stable operation of a high-proportion new energy alternating-current and direct-current hybrid system.
Embodiment two:
the present embodiment provides another method for determining an operating range of LCC-HVDC, which is implemented on the basis of the above embodiment, as shown in a flowchart of another method for determining an operating range of LCC-HVDC in fig. 5, and the method for determining an operating range of LCC-HVDC in the present embodiment includes the steps of:
step S502, collecting operation parameters of a direct current system and an alternating current system.
Specifically, the operation parameters in the present embodiment include: the trigger angle of the rectifying side and the inverting side, the arc extinguishing angle of each converter valve of the inverting side, the direct current voltage and the direct current of the rectifying side and the inverting side, the alternating current voltage of the rectifying side and the inverting side, and the voltage and the current of the reactive compensation devices at two sides.
Reference may be made to a schematic diagram of a method of determining the operating range of an LCC-HVDC system as shown in fig. 6 and a schematic diagram of an ac/dc series-parallel system as shown in fig. 7, which may be used in subsequent steps after the acquisition of the operating parameters.
Step S504, judging whether the operation parameters meet the preset threshold range.
Specifically, the embodiment can determine whether the ac bus voltage on the rectifying side and the ac bus voltage on the inverting side both satisfy the corresponding preset ranges, and whether the arc extinguishing angle on the inverting side is greater than the preset threshold.
As shown in fig. 6, in this embodiment, the operation mode can be determined and switched, and the ac bus voltage U on the rectifying and inverting side can be detected in real time pr 、U pi And judging the running state of the direct current system by the inversion side arc extinction angle gamma, and starting the control method provided by the embodiment when the transient voltage disturbance is detected.
In step S506, if the operation parameter satisfies the threshold range, the dc system is controlled to remain in operation.
As shown in FIG. 6, when the real-time detected AC bus voltage per unit value and the inversion side arc extinguishing angle gamma satisfy 0.9 < U pr < 1.1 and 0.9 < U pi When gamma is less than 1.1 and is more than 10 degrees, the system is considered to be in a normal running state, and the direct current system can be controlled to keep running without taking extra measures.
Step S508, if the operation parameters do not meet the threshold range, determining the Thevenin equivalent parameters of the AC system.
As shown in FIG. 6, when 0.9 < U pr ＜1.1、0.9＜U pi When any condition of < 1.1 and gamma > 10 degrees is not satisfied, the system is considered to be faulty, the enabling signal Ctrl takes 1, and the high-voltage direct-current control system is switched into the control method provided by the embodiment.
Specifically, the embodiment can collect the voltage and the current of the alternating current system, and determine the Thevenin equivalent parameters of the alternating current system based on the voltage and the current of the alternating current system; wherein, the Thevenin equivalent parameters include: equivalent voltage and equivalent impedance of the transmitting-end alternating current system and equivalent voltage and equivalent impedance of the receiving-end alternating current system.
As shown in fig. 6, the embodiment may obtain ac/dc series-parallel system parameters, where the ac/dc series-parallel system parameters may include: the Thevenin equivalent parameters and the power parameters, etc. The embodiment can estimate Thevenin equivalent parameters of the AC system according to the AC system voltage and current acquired in real time, including the equivalent voltage E of the AC system at the transmitting end sr And equivalent impedance R 1 +jX 1 Equivalent voltage E of receiving end alternating current system si And equivalent impedance R 3 +jX 3 。
The embodiment can realize online real-time estimation of Thevenin equivalent parameters, can meet the requirements under transient time scale, and does not limit a specific parameter estimation method.
Step S510, obtaining a power parameter; wherein the power parameters include: active and reactive power provided by the ac system, active and reactive power provided by the wind farm, and reactive power provided by the converter station reactive compensation device.
As shown in fig. 6, in this embodiment, active power and reactive power provided by an ac system, active power and reactive power provided by a wind farm, reactive power provided by a reactive compensation device of a converter station, and the like may be collected as power parameters. Alternatively, the present embodiment may employ an instantaneous power method for calculation, which has a faster calculation speed and accuracy.
Step S512, determining the operation range of the DC system under the synchronous stability constraint condition and the restraint commutation failure constraint condition based on the Thevenin equivalent parameter and the power parameter.
Specifically, the present embodiment may determine the power parameter of the rectifying side and the power parameter of the inverting side based on a quasi-steady equation set in advance; wherein, the power parameter of rectifying side includes: active power and reactive power of the rectifying side, and power parameters of the inverting side include: active power and reactive power of the inversion side; determining synchronous stability constraint conditions of the rectifying side and the inverting side based on the Thevenin equivalent parameter, the power parameter of the rectifying side and the power parameter of the inverting side; the operation range of the direct current of the rectifying side is determined together based on the synchronous stability constraint condition of the rectifying side, the synchronous stability constraint condition of the inverting side and the predetermined constraint condition for inhibiting commutation failure.
As shown in fig. 6, the operation range of the dc system under the synchronous stabilization constraint can be calculated in this embodiment. The stable operation of the alternating current-direct current series-parallel system requires that the alternating current system and the direct current system maintain synchronous stability, and is characterized in that the rectifying station should maintain synchronous operation with the alternating current equivalent system at the transmitting end, and the inverting station should maintain synchronous operation with the alternating current equivalent system at the receiving end.
The simplified equivalent circuit of the ac/dc series-parallel system shown in fig. 3 can obtain the following power-voltage expressions for the transmitting and receiving end system:
Figure SMS_1
（1）
Figure SMS_2
（2）
from the formulas (1) and (2), the following constraint can be obtained:
Figure SMS_3
（3）
Figure SMS_4
（4）
equation (3) and equation (4) represent synchronous stability constraints on the rectifying side and the inverting side, respectively. Wherein, thevenin equivalent parameter E sr 、R 1 +jX 1 、E si And R is 3 +jX 3 Obtained by the previous steps, P 2 、Q 2 、Q cr 、Q ci The reactive power compensation device comprises active power provided by a wind power plant to a direct current system, reactive power provided by the wind power plant to the direct current system, reactive power provided by a reactive power compensation device of a rectifying station and reactive power provided by a reactive power compensation device of an inversion station. Wherein the variables of the formula (3) and the formula (4) are only the rectifying side active power P dr Reactive power Q dr And inverter side active power P di Reactive power Q di 。
It is particularly emphasized that the synchronous stability constraint condition in the present embodiment is equivalent to a stability constraint condition requiring a short-circuit ratio index greater than or equal to 2 in the single-feed high-voltage direct-current transmission system when the specified condition is satisfied; the short circuit ratio index represents the ratio of the short circuit capacity of the alternating current system to the rated direct current transmission capacity.
The synchronous stability constraint deduced in this embodiment is equivalent to the stable operating limit expressed in terms of short-circuit ratio in a conventional single-feed hvdc transmission system when the following three conditions are met: 1) Irrespective of the access to the wind farm, i.e. P 2 =Q 2 =0, 2) the reactive compensation device of the converter station gives out reactive power and the reactive power of the converter station is balanced completely, i.e. Q cr =Q dr ，Q ci =Q di The reactive power is not exchanged between the AC and DC systems at the transmitting and receiving end, and 3) the AC system is a pure inductive system, namely R 1 =R 3 = 0。
The method provided in this embodiment can be deduced when the above conditions are satisfied:
Figure SMS_5
where x=r, y=1 or x=i, y=3, which is equivalent to the condition that the steady operation of the single-feed hvdc transmission system requires a short circuit ratio of more than 2. Thus, the present realityCompared with the existing scheme, the method provided by the embodiment is more universal and more suitable for the scene of high-proportion new energy access.
Further, the active power P on the rectifying side in the formulas (3) and (4) dr Reactive power Q at rectifying side dr Active power P on inversion side di Reactive power Q at inversion side di From the quasi-steady state equation of LCC-HVDC:
Figure SMS_6
（5）
Figure SMS_7
（6）
Figure SMS_8
（7）
Figure SMS_9
（8）
in the formulae (5) - (8), P dr And P di The calculated direct current active power at the rectifying side and the inversion side respectively, Q dr And Q di The calculated direct current reactive power of the rectifying side and the inversion side respectively, N is the number of 6 pulse wave converters in one converter valve, and N is 2 and T for a 12 pulse converter valve r And T is i The transformation ratio of the converter transformer at the rectifying side and the inversion side is respectively, alpha is the triggering angle at the rectifying side, gamma is the arc extinguishing angle at the inversion side, and alpha, gamma and U pr And U pi All can be obtained in real time, X cr And X is ci The rectifying side and the inverting side are respectively used for phase-change reactance. In the formulas (5) to (8), only the dc current Id on the rectifying side is an independent variable.
Thus, according to equation (3) equation- (8), substituting the system parameters of LCC-HVDC and the electric quantity measured in real time, the operating range of the direct current of LCC-HVDC under the common constraint of the synchronization stability of the transmitting and receiving end can be determined and the operating limit thereof can be determined.
On the other hand, to avoid a subsequent commutation failure that may occur during the fault recovery process, the dc current command should satisfy the following constraint that suppresses the commutation failure:
Figure SMS_10
（9）
wherein U is n For peak value of inversion side commutation voltage, alpha iN For the rated firing angle of the inversion side, gamma min The angle is closed for the inherent limit.
Furthermore, in order to maintain the system critical parameters of LCC-HVDC not out of limit, the following requirements should also be met:
Figure SMS_11
（10）
Figure SMS_12
（11）
Figure SMS_13
（12）
wherein I is dN Is rated for direct current.
The transient voltage disturbance of multiple types, including short-circuit fault, broken line fault, overvoltage caused by reactive surplus and the like, can be equivalently the change of the Thevenin equivalent parameter. Thus, according to the above formula, the present embodiment can determine the operating range of the LCC-HVDC system under transient time scale under multiple types of transient voltage disturbances and determine its operating limit.
And step S514, determining a control instruction of the direct current system based on the minimum deviation of the voltage of the alternating current bus at the receiving end of the operation range of the direct current system, and controlling the direct current system to operate based on the control instruction.
As shown in fig. 6, the present embodiment may calculate a control command of the HVDC system, that is, a reference current command, with the minimum voltage deviation at the converter bus as a target, so as to fully exert the active supporting capability of the LCC-HVDC system during transient voltage disturbance.
Specifically, the present embodiment can determine an objective function; wherein the objective function is related to the direct current at the rectifying side; determining a reference current instruction minimizing an objective function as a control instruction of the direct current system based on the operation range of the direct current of the rectifying side; the minimum characteristic of the objective function is that the deviation of the voltage of the commutation bus at the rectifying side and the deviation of the voltage of the commutation bus at the inverting side are minimum in combination.
The present embodiment can determine an objective function. Determining the priority of maintaining the minimum voltage deviation of the rectifying side converter bus and the minimum voltage deviation of the inverting side converter bus according to actual needs, and determining the objective function as follows:
Figure SMS_14
（13）
wherein U is prN 、U pIN Rated voltage, k, of ac bus bar on rectifying side and inverting side respectively 1 、k 2 The weight coefficients for keeping the minimum voltage deviation of the commutation bus at the rectifying side and the minimum voltage deviation of the commutation bus at the inverting side are respectively calculated as the following weight coefficients (0, 1) according to the specific scene (the strength of the alternating current system at the transmitting and receiving end)]And dynamically adjusting the range.
When k is 1 = 1，k 2 When=0, it means that the receiving ac system is strong at this time, only the rectifying side converter bus voltage is concerned with stability. For a high-proportion new energy source transmitting end system, the stability of transmitting end alternating voltage is more required to be concerned at the moment due to the fact that a large number of new energy source generating sets sensitive to transient voltage disturbance are connected. It should be noted that, since LCC-HVDC cannot adjust the reactive power of each phase individually, the present invention only focuses on exerting an active supporting effect of LCC-HVDC on symmetrical transient voltage disturbances, i.e. three-phase power adjustment simultaneously.
Thereafter, the present embodiment can solve the optimization problem. Taking the minimum of the formula (13) as an optimization target, taking the obtained LCC-HVDC operation range of the previous step as a constraint condition, and solving a high-voltage direct-current transmission system control instruction Idref1 for maximizing the LCC-HVDC adjustment capability. The optimization problem is that only the direct current I at the rectifying side d Decision variableIn practice, the solution is easy, so the invention does not prescribe the solution method.
In addition, the embodiment can also judge whether the current operation parameters of the direct current system and the alternating current system continuously meet the threshold range; if the current operation parameters do not continuously meet the threshold range, determining Thevenin equivalent parameters of the communication system based on the current operation parameters; and if the current operation parameters continuously meet the threshold range, controlling the direct current system to keep running.
As shown in fig. 6, when the per unit value of the voltage of the converter bus detected in real time and the arc extinction angle γ of the inversion side satisfy 0.9 < Up < 1.1 and γ > 10 ° and continue 50 ms, the system is considered to resume the normal operation state, and the control method provided in this embodiment can be withdrawn from operation, and the hvdc transmission system is switched to the conventional control.
The embodiment of the invention provides an LCC-HVDC operation range and limit determination method, which solves the defect that the existing scheme can not accurately describe the LCC-HVDC transient time scale operation range under the action of multi-type transient voltage disturbance after the high-proportion new energy source of a transmitting end is accessed, and can ensure the synchronous stability of an LCC-HVDC system and a transmitting and receiving end alternating current system under the multi-type transient voltage disturbance; compared with the conventional control strategy, the method can maximize the adjusting capability of LCC-HVDC on the premise of ensuring the stability of an AC-DC system, and actively supports the stability of the voltage of the commutation bus at the rectifying side and the inversion side.
According to the method provided by the embodiment, firstly, an equivalent model of an alternating-direct current series-parallel system is established, and parameters of the equivalent model are obtained through real-time measurement and Thevenin equivalent; respectively establishing a power-voltage equation for the alternating current-direct current series-parallel system of the transmitting and receiving end, and deducing the operation range and limit of the LCC-HVDC system under the common constraint of synchronous stability of the transmitting and receiving end by combining with the LCC-HVDC quasi-steady state equation; and in the LCC-HVDC safe operation range, calculating a control instruction of the high-voltage direct-current power transmission system by taking the minimum voltage deviation of the current converting bus at the transmitting and receiving end as a target, and fully playing the active supporting role of the LCC-HVDC in the transient voltage disturbance period.
The method provided by the embodiment can determine the operating range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after the high-proportion new energy is accessed, and actively and fully exert the adjusting capability of the LCC-HVDC system to relieve the transient voltage disturbance of the transmitting and receiving end, and simultaneously inhibit the subsequent commutation failure, thereby having important significance for ensuring the safe and stable operation of the high-proportion new energy alternating-current/direct-current hybrid system.
Embodiment III:
corresponding to the above method embodiments, an embodiment of the present invention provides an operation range determining device for LCC-HVDC, referring to a schematic structure diagram of an operation range determining device for LCC-HVDC shown in fig. 8, the operation range determining device for LCC-HVDC includes:
An operation parameter collection module 81, configured to collect operation parameters of the dc system and the ac system;
an operation parameter judging module 82, configured to judge whether the operation parameter meets a preset threshold range;
the Thevenin equivalent parameter determining module 83 is configured to determine the Thevenin equivalent parameter of the communication system if the operation parameter does not satisfy the threshold range;
a power parameter acquisition module 84 for acquiring power parameters; wherein the power parameters include: active power and reactive power provided by an alternating current system, active power and reactive power provided by a wind farm, and reactive power provided by a reactive compensation device of a convertor station;
an operation range determining module 85, configured to determine an operation range of the dc system under a synchronous stability constraint condition and a commutation failure constraint condition based on the davien equivalent parameter and the power parameter;
the dc system control module 86 is configured to determine a control instruction of the dc system based on the minimum deviation of the voltage of the ac bus at the receiving end in the operation range of the dc system, and control the dc system to operate based on the control instruction.
The embodiment of the invention provides a method and a device for determining the operating range of LCC-HVDC, which can determine the operating range of LCC-HVDC transient time scale under the action of multi-type transient voltage disturbance after high-proportion new energy is accessed, and actively and fully exert the adjusting capability of an LCC-HVDC system to relieve the transient voltage disturbance of a transmitting and receiving end, inhibit subsequent commutation failure, and have important significance for ensuring the safe and stable operation of a high-proportion new energy alternating-current/direct-current hybrid system.
The above-mentioned operating parameters include: the trigger angle of the rectifying side and the inverting side, the arc extinguishing angle of each converter valve of the inverting side, the direct current voltage and the direct current of the rectifying side and the inverting side, the alternating current voltage of the rectifying side and the inverting side, and the voltage and the current of the reactive compensation devices at two sides.
The operation parameter judging module is used for judging whether the alternating current bus voltage at the rectifying side and the alternating current bus voltage at the inverting side meet the corresponding preset range or not and whether the arc extinguishing angle at the inverting side is larger than a preset threshold value or not.
The device further comprises: and the direct current system keeps the operation module and is used for controlling the direct current system to keep operating if the operation parameters meet the threshold range.
The Thevenin equivalent parameter determining module is used for collecting the voltage and the current of the alternating current system and determining the Thevenin equivalent parameter of the alternating current system based on the voltage and the current of the alternating current system; wherein, the Thevenin equivalent parameters include: equivalent voltage and equivalent impedance of the transmitting-end alternating current system and equivalent voltage and equivalent impedance of the receiving-end alternating current system.
The operation range determining module is used for determining a power parameter of the rectifying side and a power parameter of the inverting side based on a preset quasi-steady equation; wherein, the power parameter of rectifying side includes: active power and reactive power of the rectifying side, and power parameters of the inverting side include: active power and reactive power of the inversion side; determining synchronous stability constraint conditions of the rectifying side and the inverting side based on the Thevenin equivalent parameter, the power parameter of the rectifying side and the power parameter of the inverting side; the operation range of the direct current of the rectifying side is determined based on the synchronous stabilization constraint condition of the rectifying side, the synchronous stabilization constraint condition of the inverting side and the predetermined restraint commutation failure constraint condition.
When the synchronous stability constraint condition meets the specified condition, the synchronous stability constraint condition is equivalent to a stability constraint condition requiring that the short circuit ratio index is more than or equal to 2 in a single-feed high-voltage direct-current power transmission system; the short circuit ratio index represents the ratio of the short circuit capacity of the alternating current system to the rated direct current transmission capacity.
The direct current system control module is used for determining an objective function; wherein the objective function is related to the direct current at the rectifying side; determining a reference current instruction minimizing an objective function as a control instruction of the direct current system based on the operation range of the direct current of the rectifying side; the minimum characteristic of the objective function is that the deviation of the voltage of the commutation bus at the rectifying side and the deviation of the voltage of the commutation bus at the inverting side are minimum in combination.
The device further comprises: the current operation parameter judging module is used for judging whether the current operation parameters of the direct current system and the alternating current system continuously meet a threshold range; if the current operation parameters do not continuously meet the threshold range, determining Thevenin equivalent parameters of the communication system based on the current operation parameters; and if the current operation parameters continuously meet the threshold range, controlling the direct current system to keep running.
It will be clear to those skilled in the art that, for convenience and brevity of description, the specific operation of the above-described LCC-HVDC operation range determining device may refer to the corresponding procedure in the foregoing embodiment of the LCC-HVDC operation range determining method, which is not described herein.
Embodiment four:
the embodiment of the invention also provides electronic equipment, which is used for operating the operation range determining method of the LCC-HVDC; referring to a schematic structural diagram of an electronic device shown in fig. 9, the electronic device includes a memory 100 and a processor 101, where the memory 100 is configured to store one or more computer instructions, and the one or more computer instructions are executed by the processor 101 to implement the above-mentioned LCC-HVDC operation range determining method.
Further, the electronic device shown in fig. 9 further includes a bus 102 and a communication interface 103, and the processor 101, the communication interface 103, and the memory 100 are connected through the bus 102.
The memory 100 may include a high-speed random access memory (RAM, random Access Memory), and may further include a non-volatile memory (non-volatile memory), such as at least one magnetic disk memory. The communication connection between the system network element and at least one other network element is implemented via at least one communication interface 103 (which may be wired or wireless), and may use the internet, a wide area network, a local network, a metropolitan area network, etc. Bus 102 may be an ISA bus, a PCI bus, an EISA bus, or the like. The buses may be divided into address buses, data buses, control buses, etc. For ease of illustration, only one bi-directional arrow is shown in fig. 9, but not only one bus or one type of bus.
The processor 101 may be an integrated circuit chip with signal processing capabilities. In implementation, the steps of the above method may be performed by integrated logic circuits of hardware in the processor 101 or instructions in the form of software. The processor 101 may be a general-purpose processor, including a central processing unit (Central Processing Unit, CPU for short), a network processor (Network Processor, NP for short), etc.; but also digital signal processors (Digital Signal Processor, DSP for short), application specific integrated circuits (Application Specific Integrated Circuit, ASIC for short), field-programmable gate arrays (Field-Programmable Gate Array, FPGA for short) or other programmable logic devices, discrete gate or transistor logic devices, discrete hardware components. The disclosed methods, steps, and logic blocks in the embodiments of the present invention may be implemented or performed. A general purpose processor may be a microprocessor or the processor may be any conventional processor or the like. The steps of the method disclosed in connection with the embodiments of the present invention may be embodied directly in the execution of a hardware decoding processor, or in the execution of a combination of hardware and software modules in a decoding processor. The software modules may be located in a random access memory, flash memory, read only memory, programmable read only memory, or electrically erasable programmable memory, registers, etc. as well known in the art. The storage medium is located in the memory 100 and the processor 101 reads information in the memory 100 and in combination with its hardware performs the steps of the method of the previous embodiments.
The embodiment of the invention also provides a computer readable storage medium, which stores computer executable instructions that, when being called and executed by a processor, cause the processor to implement the above-mentioned method for determining the operating range of LCC-HVDC, and the specific implementation can be seen in the method embodiment and will not be described herein.
The method, the device and the electronic equipment for determining the operation range of the LCC-HVDC provided by the embodiment of the invention comprise a computer readable storage medium storing program codes, and the instructions included in the program codes can be used for executing the method in the previous method embodiment, and specific implementation can be referred to the method embodiment and will not be repeated here.
It will be clear to those skilled in the art that, for convenience and brevity of description, specific working procedures of the above-described system and/or apparatus may refer to corresponding procedures in the foregoing method embodiments, which are not repeated herein.
In addition, in the description of embodiments of the present invention, unless explicitly stated and limited otherwise, the terms "mounted," "connected," and "connected" are to be construed broadly, and may be, for example, fixedly connected, detachably connected, or integrally connected; can be mechanically or electrically connected; can be directly connected or indirectly connected through an intermediate medium, and can be communication between two elements. The specific meaning of the above terms in the present invention will be understood in specific cases by those of ordinary skill in the art.
The functions, if implemented in the form of software functional units and sold or used as a stand-alone product, may be stored in a computer-readable storage medium. Based on this understanding, the technical solution of the present invention may be embodied essentially or in a part contributing to the prior art or in a part of the technical solution, in the form of a software product stored in a storage medium, comprising several instructions for causing a computer device (which may be a personal computer, a server, a network device, etc.) to perform all or part of the steps of the method according to the embodiments of the present invention. And the aforementioned storage medium includes: a U-disk, a removable hard disk, a Read-Only Memory (ROM), a random access Memory (RAM, random Access Memory), a magnetic disk, or an optical disk, or other various media capable of storing program codes.
In the description of the present invention, it should be noted that the directions or positional relationships indicated by the terms "center", "upper", "lower", "left", "right", "vertical", "horizontal", "inner", "outer", etc. are based on the directions or positional relationships shown in the drawings, are merely for convenience of describing the present invention and simplifying the description, and do not indicate or imply that the devices or elements referred to must have a specific orientation, be configured and operated in a specific orientation, and thus should not be construed as limiting the present invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance.
Finally, it should be noted that: the above examples are only specific embodiments of the present invention, and are not intended to limit the scope of the present invention, but it should be understood by those skilled in the art that the present invention is not limited thereto, and that the present invention is described in detail with reference to the foregoing examples: any person skilled in the art may modify or easily conceive of the technical solution described in the foregoing embodiments, or perform equivalent substitution of some of the technical features, while remaining within the technical scope of the present disclosure; such modifications, changes or substitutions do not depart from the spirit and scope of the technical solutions of the embodiments of the present invention, and are intended to be included in the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (10)

1. A method of operating range determination for LCC-HVDC, the method comprising:
collecting operation parameters of a direct current system and an alternating current system;
judging whether the operation parameters meet a preset threshold range or not;
if the operating parameter does not meet the threshold range, determining a Thevenin equivalent parameter of the alternating current system;
Acquiring a power parameter; wherein the power parameters include: the active power and the reactive power provided by the alternating current system, the active power and the reactive power provided by the wind farm and the reactive power provided by the reactive compensation device of the convertor station;
determining the operation range of the direct current system under a synchronous stability constraint condition and a commutation failure inhibition constraint condition based on the Thevenin equivalent parameter and the power parameter;
and determining a control instruction of the direct current system based on the minimum voltage deviation of the alternating current bus at the receiving end of the operating range of the direct current system, and controlling the direct current system to operate based on the control instruction.
2. The LCC-HVDC operating range determination method according to claim 1, wherein said operating parameters comprise: the trigger angle of the rectifying side and the inverting side, the arc extinguishing angle of each converter valve of the inverting side, the direct current voltage and the direct current of the rectifying side and the inverting side, the alternating current voltage of the rectifying side and the inverting side, and the voltage and the current of the reactive compensation devices at two sides.
3. The LCC-HVDC operation range determining method according to claim 2, wherein the step of judging whether the operation parameter satisfies a preset threshold range comprises:
And judging whether the alternating current bus voltage at the rectifying side and the alternating current bus voltage at the inverting side meet the corresponding preset range or not, and whether the arc extinguishing angle at the inverting side is larger than a preset threshold value or not.
4. The LCC-HVDC operation range determining method according to claim 1, wherein after the step of judging whether or not the operation parameter satisfies a preset threshold range, the method further comprises:
and if the operating parameter meets the threshold range, controlling the direct current system to keep operating.
5. The method of operating range determination for LCC-HVDC according to claim 1, wherein the step of determining the thevenin equivalent parameter of the ac system comprises:
collecting the voltage and the current of the alternating current system, and determining the Thevenin equivalent parameters of the alternating current system based on the voltage and the current of the alternating current system; wherein the Thevenin equivalent parameters include: equivalent voltage and equivalent impedance of the transmitting-end alternating current system and equivalent voltage and equivalent impedance of the receiving-end alternating current system.
6. The method of claim 1, wherein the step of determining the operating range of the dc system under synchronous stabilization constraints and suppressed commutation failure constraints based on the thevenin equivalent parameter and the power parameter comprises:
Determining a power parameter of a rectifying side and a power parameter of an inverting side based on a preset quasi-steady equation; wherein the power parameters of the rectifying side include: the active power and reactive power of the rectifying side, and the power parameters of the inverting side include: the inverter side active power and reactive power;
determining a synchronous stability constraint condition of the rectifying side and a synchronous stability constraint condition of the inverting side based on the Thevenin equivalent parameter, the power parameter of the rectifying side and the power parameter of the inverting side;
and determining the operation range of the direct current of the rectifying side based on the synchronous stability constraint condition of the rectifying side, the synchronous stability constraint condition of the inverting side and a predetermined constraint condition for inhibiting commutation failure.
7. The method according to claim 1, wherein the synchronous stability constraint is equivalent to a stability constraint requiring a short circuit ratio index greater than or equal to 2 in a single feed high voltage direct current transmission system when a specified condition is satisfied; the short circuit ratio index represents the ratio of the short circuit capacity of the alternating current system to the rated direct current transmission capacity.
8. The method of claim 1, wherein the step of determining the control command for the dc system based on the minimum deviation of the voltage of the ac bus at the receiving end from the operating range of the dc system comprises:
Determining an objective function; wherein the objective function is related to the direct current at the rectifying side;
determining a reference current instruction minimizing the objective function as a control instruction of the direct current system based on the operation range of the direct current of the rectifying side; the objective function is minimum, and represents that deviation of the commutation bus voltage at the rectifying side and deviation of the commutation bus voltage at the inverting side are minimum comprehensively.
9. The LCC-HVDC operation range determining method according to claim 1, wherein after the step of controlling the direct current system to operate based on the control instruction, the method further comprises:
judging whether the current operation parameters of the direct current system and the alternating current system continuously meet the threshold range or not;
if the current operation parameters do not continuously meet the threshold range, determining Thevenin equivalent parameters of the alternating current system based on the current operation parameters;
and if the current operation parameters continuously meet the threshold range, controlling the direct current system to keep running.
10. An LCC-HVDC operating range determining device, the device comprising:
the operation parameter acquisition module is used for acquiring operation parameters of the direct current system and the alternating current system;
The operation parameter judging module is used for judging whether the operation parameter meets a preset threshold range or not;
the Thevenin equivalent parameter determining module is used for determining the Thevenin equivalent parameter of the alternating current system if the operating parameter does not meet the threshold range;
the power parameter acquisition module is used for acquiring power parameters; wherein the power parameters include: the active power and the reactive power provided by the alternating current system, the active power and the reactive power provided by the wind farm and the reactive power provided by the reactive compensation device of the convertor station;
the operation range determining module is used for determining the operation range of the direct current system under the synchronous stability constraint condition and the restraint commutation failure constraint condition based on the Thevenin equivalent parameter and the power parameter;
and the direct current system control module is used for determining a control instruction of the direct current system based on the aim of minimum deviation of the voltage of the alternating current bus at the receiving end of the operating range of the direct current system, and controlling the direct current system to operate based on the control instruction.
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