CN115224717A - Sending-end alternating current fault ride-through method of new energy island power grid sending-out system - Google Patents

Sending-end alternating current fault ride-through method of new energy island power grid sending-out system Download PDF

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CN115224717A
CN115224717A CN202211057669.5A CN202211057669A CN115224717A CN 115224717 A CN115224717 A CN 115224717A CN 202211057669 A CN202211057669 A CN 202211057669A CN 115224717 A CN115224717 A CN 115224717A
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sending
direct current
voltage
alternating current
flexible direct
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李桂源
郭铸
黄伟煌
蔡东晓
饶宏
蔡希鹏
李岩
赵晓斌
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CSG Electric Power Research Institute
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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
    • H02J3/24—Arrangements for preventing or reducing oscillations of power in networks
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/381—Dispersed generators
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/388—Islanding, i.e. disconnection of local power supply from the network
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/38—Arrangements for parallely feeding a single network by two or more generators, converters or transformers
    • H02J3/46—Controlling of the sharing of output between the generators, converters, or transformers
    • H02J3/466—Scheduling the operation of the generators, e.g. connecting or disconnecting generators to meet a given demand
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2300/00—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation
    • H02J2300/20—The dispersed energy generation being of renewable origin
    • H02J2300/22—The renewable source being solar energy
    • H02J2300/24—The renewable source being solar energy of photovoltaic origin
    • 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
    • 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
    • H02J2300/40—Systems for supplying or distributing electric power characterised by decentralized, dispersed, or local generation wherein a plurality of decentralised, dispersed or local energy generation technologies are operated simultaneously
    • 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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  • Power Engineering (AREA)
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Abstract

The invention discloses a sending end alternating current fault ride-through method of a new energy island power grid sending-out system, which is characterized in that when the sending end alternating current fault is detected, a control system of a sending end flexible direct current converter station enters low ride-through logic, an integral link of a d-axis controller and a q-axis controller is reset, an input voltage reference value of a d-axis voltage controller of the sending end flexible direct current converter station is made to be equal to an alternating current voltage reference value before the alternating current fault occurs minus a negative sequence alternating current voltage effective value after the alternating current fault occurs, amplitude limiting is carried out on the d-axis current reference value and the q-axis current reference value, the output of a direct current controller is kept before the alternating current fault occurs, and the technical problems that the coordination control capability of the sending end flexible direct current converter station and a new energy source unit is poor and the recovery characteristic is poor after the sending end alternating current fault is removed in the situation of the new energy island power grid sending-out system are solved by coordinating and controlling the actual alternating current voltage recovery speed when the alternating current voltage is recovered.

Description

Sending-end alternating current fault ride-through method of new energy island power grid sending-out system
Technical Field
The invention relates to the technical field of flexible direct current transmission, in particular to a sending end alternating current fault ride-through method of a new energy island power grid sending-out system.
Background
Most new energy bases are built in remote areas, the load level is low, the grid structure is weak, and the requirement for stable delivery of new energy islands is obvious. The flexible direct current transmission has the characteristics of flexibility, controllability, high efficiency and the like, and is one of important power transmission means for new energy transmission. For a sending end, the flexible direct current converter can provide stable alternating voltage for a new energy electric field, can operate in an isolated island mode, can sufficiently and quickly dynamically compensate, reduces the risk of the new energy unit being disconnected from the network, and improves the utilization rate of new energy. For a receiving end, the problem of phase commutation failure of flexible direct current does not exist, dynamic reactive compensation can be provided, and the method has important significance for effectively solving the problems of stability of a multi-direct-current feed-in alternating current power grid, resistance to serious faults of the power grid and the like.
The cross of a sending end alternating current fault is a key technology to be considered for a new energy island power grid sending-out system, and the following challenges are still faced currently: 1) Island alternating-current voltage is provided by a sending end flexible direct-current converter station, and the stability of the sending end alternating-current voltage is directly influenced by the alternating-current voltage control characteristic of the sending end flexible direct-current converter station; 2) The problem of overvoltage suppression under the condition of alternating current fault by the coordination control action between the new energy source unit at the sending end and the flexible direct current converter at the sending end is complex; 3) The stability of the sending end alternating current fault can restore the system operation problem.
Disclosure of Invention
The invention provides a sending end alternating current fault ride-through method of a new energy island power grid sending-out system, which is used for solving the technical problems that a sending end flexible direct current converter station and a new energy unit are poor in coordination control capability, poor in alternating current overvoltage suppression capability during alternating current fault and poor in recovery characteristic after the sending end alternating current fault is cleared when the new energy island power grid sending-out system is in the situation of sending end alternating current fault.
In view of this, the present invention provides a method for ride-through of a sending-end ac fault of a new energy island grid sending-out system, including:
the method includes the steps that S1, a new energy island power grid sending-out system is built, the new energy island power grid sending-out system comprises a new energy electric field, a sending end flexible direct current converter station, a receiving end flexible direct current converter station and a direct current overhead line, the new energy electric field is connected to the sending end flexible direct current converter station through a three-phase alternating current bus, the sending end flexible direct current converter station is connected with the receiving end flexible direct current converter station through a bipolar direct current overhead line, and the sending end flexible direct current converter station, the direct current overhead line and the receiving end flexible direct current converter station form a true bipolar direct current system;
s2, configuring control strategies of the sending-end flexible direct current converter stations and the receiving-end flexible direct current converter stations, wherein all the sending-end flexible direct current converter stations adopt a double-closed-loop constant alternating voltage and frequency control strategy, only one receiving-end flexible direct current converter station adopts a constant direct voltage control strategy, and the other receiving-end flexible direct current converter stations adopt a constant active power control strategy;
s3, detecting the alternating voltage of the flexible direct current converter station at the sending end in real time, judging whether an alternating current fault occurs according to the effective value of the alternating voltage, if so, generating a low alternating voltage signal Uac _ low, and simultaneously executing the steps S4 to S7;
s4, clearing an integration link of a d-axis voltage controller and a q-axis voltage controller of the sending end flexible direct current converter station during the generation of the low alternating current voltage signal Uac _ low;
s5, calculating the negative sequence alternating current voltage effective value of the sending end flexible direct current converter station in real time, and enabling the input voltage reference value of the d-axis voltage controller of the sending end flexible direct current converter station to be equal to the value obtained by subtracting the negative sequence alternating current voltage effective value after the alternating current fault from the alternating current voltage reference value before the alternating current fault occurs during the period of generating the low alternating current voltage signal Uac _ low;
s6, limiting the d-axis current reference value and the q-axis current reference value;
s7, keeping the output of the direct current controller at the output before the alternating current fault occurs;
and S8, detecting the alternating voltage of the flexible direct current converter station at the sending end in real time, judging whether the effective value of the alternating voltage is larger than a preset value, and if so, reducing the effective value of the negative sequence alternating voltage according to a preset slope, so that the reference value of the alternating voltage is recovered to 1pu.
Optionally, in step S8, the preset slope is 10pu/S to 30pu/S.
Optionally, step S7 specifically includes:
the output of the dc current controller is maintained at the output 100ms before the ac fault.
Optionally, in step S6, a clipping calculation formula for clipping the q-axis current reference value is as follows:
Figure BDA0003825734210000021
I q min ＝-I q max
wherein, I qmax Maximum value of q-axis current, I qmin Is the minimum value of the q-axis current, I max_set Maximum AC current, I, that the flexible DC converter at the sending end can bear dmax Is the d-axis current maximum.
Optionally, the effective value of the ac voltage of the transmitting-end flexible dc converter station is calculated by the following formula:
Figure BDA0003825734210000022
wherein, V m Is an effective value of AC voltage, V sd Voltage, V, being d-axis component of dq-axis component sq Of the dq-axis componentA voltage.
According to the technical scheme, the sending end alternating current fault ride-through method of the new energy island power grid sending-out system has the following advantages:
the invention provides a sending end alternating current fault ride-through method of a new energy island power grid sending-out system, when detecting that an alternating current fault occurs at a sending end, a control system of a sending end flexible direct current converter station enters low ride-through logic, an integral link of a d-axis controller and a q-axis controller is cleared, an input voltage reference value of a d-axis voltage controller of the sending end flexible direct current converter station is made to be equal to an alternating current voltage reference value before the alternating current fault occurs minus a negative sequence alternating current voltage effective value after the alternating current fault occurs, so that the alternating current voltage reference value of the sending end flexible direct current converter station is reduced, the d-axis current reference value and the q-axis current reference value are subjected to amplitude limiting, and the output of a direct current controller is kept to be output before the alternating current fault occurs, when the alternating voltage is recovered, the actual alternating voltage recovery speed is coordinately controlled, extra disturbance brought by a direct current controller in the sending end alternating current fault period is avoided, the phenomena of overvoltage and overcurrent of the system and the like caused by flexible direct control saturation in the recovery process can be effectively avoided, the alternating current fault ride-through capability of the new energy island power grid is greatly improved, the recovery characteristic after fault removal is improved, and the technical problems that the coordination control capability of a sending end flexible direct current converter station and a new energy unit is poor, the alternating current overvoltage suppression capability in the alternating current fault period is poor and the recovery characteristic after the sending end alternating current fault removal is poor in the sending end alternating current fault condition of the new energy island power grid sending-out system are solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other related drawings can be obtained according to the drawings without creative efforts.
Fig. 1 is a schematic flow chart of a sending-end ac fault ride-through method of a new energy island grid sending-out system according to an embodiment of the present invention;
fig. 2 is an architecture diagram of a new energy island power grid sending-out system provided in an embodiment of the present invention;
fig. 3 is a schematic control structure diagram of a flexible direct current converter station at a sending end of a new energy island grid sending-out system provided in an embodiment of the present invention;
fig. 4 is a schematic diagram showing a comparison of simulation results of a sending-end ac fault ride-through method of a new energy island power grid sending-out system provided in the embodiment of the present invention and an existing sending-end ac fault ride-through method.
Detailed Description
In order to make those skilled in the art better understand the technical solutions of the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be obtained by a person skilled in the art without making any creative effort based on the embodiments in the present invention, belong to the protection scope of the present invention.
For convenience of understanding, referring to fig. 1 and fig. 2, an embodiment of a sending-end ac fault ride-through method for a new energy island grid sending-out system is provided in the present invention, including:
step 101, a new energy island power grid sending-out system is built, the new energy island power grid sending-out system comprises a new energy electric field, a sending end flexible direct current converter station, a receiving end flexible direct current converter station and a direct current overhead line, the new energy electric field is connected to the sending end flexible direct current converter station through a three-phase alternating current bus, the sending end flexible direct current converter station is connected with the receiving end flexible direct current converter station through a bipolar direct current overhead line, and the sending end flexible direct current converter station, the direct current overhead line and the receiving end flexible direct current converter station form a true bipolar direct current system.
It should be noted that, in the embodiment of the present invention, a new energy island power grid sending-out system is first established, and a structure of the new energy island power grid sending-out system is as shown in fig. 2, and includes a new energy electric field, a sending-end flexible dc converter station, a receiving-end flexible dc converter station, and a dc overhead line, and may further include an ac energy consumption device, where the new energy electric field is commonly connected to the sending-end flexible dc converter station through a three-phase ac bus, the ac energy consumption device is connected between the new energy electric field and the sending-end flexible dc converter station, the sending-end flexible dc converter station is connected to the receiving-end flexible dc converter station through a bipolar dc overhead line, and the sending-end flexible dc converter station, the dc overhead line, and the receiving-end flexible dc converter station constitute a true bipolar dc system. The new energy electric field comprises a wind power plant, a photovoltaic electric field and other renewable energy electric fields. The alternating current energy consumption device is used for dissipating the continuous active power output of the new energy electric field when the active power transmission channel of the direct current line is blocked, and the problem of overvoltage caused by energy accumulation of the alternating current feeder line at the sending end is avoided.
The sending end flexible direct current converter station and the receiving end flexible direct current converter station can adopt a single valve group form or a double valve group series connection form, and the converter valve adopts a full-bridge submodule or a module formed by mixing the full-bridge submodule and a half-bridge submodule. The flexible direct current converter station is composed of six three-phase bridge arms, each phase comprises an upper bridge arm and a lower bridge arm, and each bridge arm is formed by connecting N sub-modules and bridge arm reactors in series. Each bridge arm is composed of the same number of converter valves with submodules, for example, when the direct current voltage is 400kV, the number of the submodules of each bridge arm is 200, and the capacitor voltage of each submodule is 2kV. The number of the sending end flexible direct current converter stations can be one or more, and single power supply or multi-power supply is realized. The number of the receiving end flexible direct current converter stations can be one or more, and single-drop or multi-drop power receiving is achieved. If a plurality of transmitting end or receiving end flexible direct current converter stations exist, the direct current overhead line mainly connects direct current sides of the converter stations at the ends, and the connection mode can be star connection or triangular connection. The transmitting end flexible direct current converter station, the direct current overhead line and the receiving end flexible direct current converter station form a true bipolar direct current system, bipolar is completely symmetrical, stable operation capacity of a direct current transmission system is greatly improved by bipolar operation, a grounding mode is simple and easy, and stable operation of a transmitting end island system can be maintained by a normal pole after a single pole fault even finally causes locking.
102, configuring control strategies of a sending-end flexible direct current converter station and a receiving-end flexible direct current converter station, wherein all the sending-end flexible direct current converter stations adopt a double-closed-loop constant alternating voltage and frequency control strategy, only one receiving-end flexible direct current converter station adopts a constant direct voltage control strategy, and the rest receiving-end flexible direct current converter stations adopt a constant active power control strategy.
It should be noted that control strategies are configured for the transmitting-end flexible direct current converter station and the receiving-end flexible direct current converter station, the transmitting ends both adopt double-closed-loop fixed alternating voltage and frequency control strategies to provide alternating voltage and frequency required by work for respective new energy electric fields, only one of the receiving-end flexible direct current converter stations adopts a fixed direct voltage control strategy to provide stable direct voltage for a direct current system, and the other receiving-end flexible direct current converter stations adopt fixed active power control strategies.
Step 103, detecting the alternating current voltage of the flexible direct current converter station at the sending end in real time, judging whether an alternating current fault occurs according to the effective value of the alternating current voltage, if so, generating a low alternating current voltage signal Uac _ low, and executing steps 104 to 107.
It should be noted that, in the dc engineering, the effective value of the ac voltage is lower than a set threshold to detect whether an ac fault occurs, the set threshold may be set according to the actual system condition, and 0.85pu is selected in the present invention. When the ac fault is detected, a low ac voltage signal Uac _ low (signal value is 1) is generated, and steps 104 to 107 are performed. The calculation formula of the effective value of the alternating voltage of the flexible direct current converter station at the sending end is as follows:
Figure BDA0003825734210000051
wherein, V m Is an effective value of AC voltage, V sd Voltage, V, being d-axis component of dq-axis component sq Is the voltage of the q-axis component of the dq-axis components.
And 104, clearing an integration link of a d-axis voltage controller and a q-axis voltage controller of the sending end flexible direct current converter station during the generation of the low alternating voltage signal Uac _ low.
It should be noted that, as shown in fig. 3, after detecting that an ac fault occurs in the sending-end flexible dc converter station, the control system of the sending-end flexible dc converter station enters a low-voltage ride-through logic, that is, a low-voltage ride-through mode, and bears a certain limit value of the low voltage of the power grid within a certain time without exiting the operation capability. And during a low voltage ride through period, namely a period when the low alternating voltage signal Uac _ low is 1, clearing the integration links of a d-axis voltage controller and a q-axis voltage controller of the sending end flexible direct current converter station.
And 105, calculating a negative sequence alternating current voltage effective value of the flexible direct current converter station at the sending end in real time, and enabling an input voltage reference value of a d-axis voltage controller of the flexible direct current converter station at the sending end to be equal to a value obtained by subtracting the negative sequence alternating current voltage effective value after the alternating current fault from an alternating current voltage reference value before the alternating current fault occurs during the period of generating a low alternating current voltage signal Uac _ low.
It should be noted that, after detecting that an ac fault occurs in the flexible dc converter station at the sending end, the negative sequence ac voltage effective value of the flexible dc converter station at the sending end is calculated in real time, and when the low ac voltage signal Uac _ low is 1, the input voltage reference value of the d-axis voltage controller of the flexible dc converter station at the sending end is equal to the value obtained by subtracting the negative sequence ac voltage effective value after the ac fault occurs from the ac voltage reference value before the ac fault occurs, so that the ac voltage reference value of the flexible dc converter station at the sending end is reduced, and the ac overvoltage phenomenon during the fault can be effectively avoided. The calculation formula of the negative sequence alternating current voltage effective value of the sending end flexible direct current converter station is as follows:
Figure BDA0003825734210000061
wherein, V fm Is an effective value of negative sequence alternating voltage, V sdN Negative sequence voltage, V, of d-axis component of dq-axis component sqN Is a negative sequence voltage of the q-axis component of the dq-axis components.
And 106, limiting the d-axis current reference value and the q-axis current reference value.
After detecting that an alternating current fault occurs in the sending-end flexible direct current converter station, the d-axis and q-axis current reference values are subjected to equal-proportion amplitude limiting. The d-axis current reference value is limited, and different values can be given to the limited value according to the voltage drop condition (the limited value can be set according to the actual application scene specifically without specific requirements). Then, the amplitude limiting value of the q-axis current reference value is calculated according to the amplitude limiting result of the d-axis current, and the amplitude limiting calculation formula for limiting the q-axis current reference value is as follows:
Figure BDA0003825734210000062
I q min ＝-I q max
wherein, I qmax Maximum value of q-axis current, I qmin Minimum value of q-axis current, I max_set Maximum AC current, I, that the flexible DC converter at the sending end can bear dmax Is the d-axis current maximum.
Step 107, the output of the dc current controller is maintained at the output before the ac fault occurs.
In order to avoid additional disturbance of the dc controller during the sending end ac fault, the output of the dc controller is maintained as the output before the fault after the sending end flexible dc converter station detects the ac fault, and preferably maintained as the output 100ms before the fault.
And 108, detecting the alternating voltage of the flexible direct current converter station at the sending end in real time, judging whether the effective value of the alternating voltage is greater than a preset value, and if so, reducing the effective value of the negative sequence alternating voltage according to a preset slope, so that the reference value of the alternating voltage is recovered to 1pu.
It should be noted that, the ac voltage of the transmitting end flexible dc converter station is detected in real time, and whether the ac voltage is greater than a preset value is determined, where the preset value may be set according to actual system conditions, and 0.9pu is selected in the present invention. And if the effective value of the alternating voltage is larger than the preset value, reducing the effective value of the negative sequence alternating voltage according to the preset slope, so that the reference value of the alternating voltage is recovered to 1pu. The slope reduction rate of the negative sequence alternating voltage effective value according to the preset slope is set by fully combining the rate of the new energy active power recovery, and if the alternating voltage recovery is too fast, the new energy output can be rapidly recovered. If the sending end flexible direct current system does not have time to send out the recovered power, the sending end flexible direct current control can be saturated and lose the alternating current voltage control, so that the sending end alternating current voltage recovery is over high instantly, even the system is continuously oscillated, and the recovery of the system is not facilitated. The value range of the preset slope in the embodiment of the invention is 10 pu/s-30 pu/s, and the recovery requirement of the system can be met.
A comparison schematic diagram of simulation results of the sending-end alternating current fault ride-through method of the new energy island power grid sending-out system provided in the embodiment of the present invention and the existing sending-end alternating current fault ride-through method is shown in fig. 4, the left side is a simulation result of the sending-end alternating current fault ride-through method of the new energy island power grid sending-out system provided in the embodiment of the present invention, and the right side is a simulation result of the existing sending-end alternating current fault ride-through method. As can be seen from fig. 4, by using the sending-end ac fault ride-through method of the new energy island power grid sending-out system provided in the embodiment of the present invention, the sending-end flexible dc converter station can safely and stably ride through the sending-end ac fault, after the fault is cleared, the ac voltage of the sending-end flexible dc converter station is stably recovered, the transient overvoltage condition is significantly improved, the voltage is reduced from 1.4pu to 1.2pu, the oscillation phenomenon does not occur after the system is recovered, and the fault ride-through effect is better than that of the existing fault ride-through method.
According to the sending end alternating current fault ride-through method of the new energy island power grid sending-out system provided by the embodiment of the invention, when the sending end alternating current fault is detected, the control system of the sending end flexible direct current converter station enters low ride-through logic, the integral links of the controllers of the d axis and the q axis are cleared, the input voltage reference value of the d axis voltage controller of the sending end flexible direct current converter station is made to be equal to the difference between the alternating current voltage reference value before the alternating current fault occurs and the negative sequence alternating current voltage effective value after the alternating current fault occurs, so that the alternating current voltage reference value of the sending end flexible direct current converter station is reduced, the amplitude of the d axis current reference value and the q axis current reference value is limited, and the output of the direct current controller is kept to be output before the alternating current fault occurs, when the alternating voltage is recovered, the actual alternating voltage recovery speed is coordinately controlled, extra disturbance brought by a direct current controller in the sending end alternating current fault period is avoided, the phenomena of overvoltage and overcurrent of the system and the like caused by flexible direct control saturation in the recovery process can be effectively avoided, the alternating current fault ride-through capability of the new energy island power grid is greatly improved, the recovery characteristic after fault removal is improved, and the technical problems that the coordination control capability of a sending end flexible direct current converter station and a new energy unit is poor, the alternating current overvoltage suppression capability in the alternating current fault period is poor and the recovery characteristic after the sending end alternating current fault removal is poor in the sending end alternating current fault condition of the new energy island power grid sending-out system are solved.
The above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; although the present invention has been described in detail with reference to the foregoing embodiments, it should be understood by those of ordinary skill in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some technical features may be equivalently replaced; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions of the embodiments of the present invention.

Claims (5)

1. A sending end alternating current fault ride-through method of a new energy island power grid sending-out system is characterized by comprising the following steps:
the method comprises the following steps of S1, constructing a new energy island power grid sending-out system, wherein the new energy island power grid sending-out system comprises a new energy electric field, a sending end flexible direct current converter station, a receiving end flexible direct current converter station and a direct current overhead line, the new energy electric field is connected to the sending end flexible direct current converter station through a three-phase alternating current bus, the sending end flexible direct current converter station is connected with the receiving end flexible direct current converter station through a bipolar direct current overhead line, and the sending end flexible direct current converter station, the direct current overhead line and the receiving end flexible direct current converter station form a true bipolar direct current system;
s2, configuring control strategies of a transmitting end flexible direct current converter station and a receiving end flexible direct current converter station, wherein all the transmitting end flexible direct current converter stations adopt a double-closed-loop fixed alternating current voltage and frequency control strategy, only one receiving end flexible direct current converter station adopts a fixed direct current voltage control strategy, and the rest receiving end flexible direct current converter stations adopt a fixed active power control strategy;
s3, detecting the alternating voltage of the flexible direct current converter station at the sending end in real time, judging whether an alternating current fault occurs according to the effective value of the alternating voltage, if so, generating a low alternating voltage signal Uac _ low, and simultaneously executing the steps S4 to S7;
s4, during the period of generating a low alternating voltage signal Uac _ low, clearing an integration link of a d-axis voltage controller and a q-axis voltage controller of the flexible direct current converter station at the sending end;
s5, calculating a negative sequence alternating current voltage effective value of the flexible direct current converter station at the sending end in real time, and enabling an input voltage reference value of a d-axis voltage controller of the flexible direct current converter station at the sending end to be equal to a value obtained by subtracting the negative sequence alternating current voltage effective value after the alternating current fault from an alternating current voltage reference value before the alternating current fault occurs during the period of generating a low alternating current voltage signal Uac _ low;
s6, limiting the d-axis current reference value and the q-axis current reference value;
s7, keeping the output of the direct current controller at the output before the alternating current fault occurs;
and S8, detecting the alternating voltage of the flexible direct current converter station at the sending end in real time, judging whether the effective value of the alternating voltage is larger than a preset value, and if so, reducing the effective value of the negative sequence alternating voltage according to a preset slope, so that the reference value of the alternating voltage is recovered to 1pu.
2. The sending-end alternating current fault ride-through method of the new energy island power grid sending-out system according to claim 1, wherein in the step S8, the preset slope is 10 pu/S-30 pu/S.
3. The sending-end alternating current fault ride-through method of the new energy island power grid sending-out system according to claim 1, wherein the step S7 specifically comprises:
the output of the dc current controller is maintained at the output 100ms before the ac fault.
4. The sending-end alternating current fault ride-through method of the new energy island power grid sending-out system according to claim 1, wherein in step S6, an amplitude limiting calculation formula for limiting a q-axis current reference value is as follows:
Figure FDA0003825734200000021
I qmin ＝-I qmax
wherein, I qmax Maximum value of q-axis current, I qmin Is the minimum value of the q-axis current, I max_set Is the maximum alternating current (I) borne by the flexible direct current converter at the sending end dmax Is the d-axis current maximum.
5. The method for ride-through of the alternating-current fault at the sending end of the new energy island power grid sending-out system according to claim 1, wherein a calculation formula of an effective value of the alternating-current voltage of the flexible direct-current converter station at the sending end is as follows:
Figure FDA0003825734200000022
wherein, V m Is an effective value of AC voltage, V sd Voltage, V, being d-axis component of dq-axis component sq Is the voltage of the q-axis component of the dq-axis components.
CN202211057669.5A 2022-08-30 2022-08-30 Sending-end alternating current fault ride-through method of new energy island power grid sending-out system Pending CN115224717A (en)

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Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116054288A (en) * 2022-12-29 2023-05-02 中国华能集团清洁能源技术研究院有限公司 Grid voltage support control method and device based on full-power converter wind turbine generator system
CN116865332A (en) * 2023-06-29 2023-10-10 南方电网科学研究院有限责任公司 Flexible direct current fault ride-through control method and device, storage medium and equipment
CN117498417A (en) * 2023-06-09 2024-02-02 国网经济技术研究院有限公司 Island operation control method of SLCC direct-current system
CN117498334A (en) * 2023-11-08 2024-02-02 南方电网科学研究院有限责任公司 Receiving end alternating current fault ride-through control method and device, electronic equipment and storage medium

Cited By (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN116054288A (en) * 2022-12-29 2023-05-02 中国华能集团清洁能源技术研究院有限公司 Grid voltage support control method and device based on full-power converter wind turbine generator system
CN117498417A (en) * 2023-06-09 2024-02-02 国网经济技术研究院有限公司 Island operation control method of SLCC direct-current system
CN116865332A (en) * 2023-06-29 2023-10-10 南方电网科学研究院有限责任公司 Flexible direct current fault ride-through control method and device, storage medium and equipment
CN116865332B (en) * 2023-06-29 2024-05-14 南方电网科学研究院有限责任公司 Flexible direct current fault ride-through control method and device, storage medium and equipment
CN117498334A (en) * 2023-11-08 2024-02-02 南方电网科学研究院有限责任公司 Receiving end alternating current fault ride-through control method and device, electronic equipment and storage medium

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