CN108879729B - Frequency emergency support and quick recovery control method and system for direct current interconnection system - Google Patents

Frequency emergency support and quick recovery control method and system for direct current interconnection system Download PDF

Info

Publication number
CN108879729B
CN108879729B CN201810820526.2A CN201810820526A CN108879729B CN 108879729 B CN108879729 B CN 108879729B CN 201810820526 A CN201810820526 A CN 201810820526A CN 108879729 B CN108879729 B CN 108879729B
Authority
CN
China
Prior art keywords
frequency
direct current
control
current
power
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Active
Application number
CN201810820526.2A
Other languages
Chinese (zh)
Other versions
CN108879729A (en
Inventor
李可军
孙凯祺
刘智杰
王美岩
王卓迪
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Shandong University
Original Assignee
Shandong University
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Shandong University filed Critical Shandong University
Priority to CN201810820526.2A priority Critical patent/CN108879729B/en
Publication of CN108879729A publication Critical patent/CN108879729A/en
Application granted granted Critical
Publication of CN108879729B publication Critical patent/CN108879729B/en
Active legal-status Critical Current
Anticipated expiration legal-status Critical

Links

Images

Classifications

    • 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
    • H02J3/36—Arrangements for transfer of electric power between ac networks via a high-tension dc link
    • 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]

Landscapes

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

Abstract

The invention discloses a direct current interconnection system frequency emergency support and rapid recovery control method and a system, when an electric power system is disturbed, direct current emergency support control is carried out by adopting frequency deviation values at two sides as control values, frequency stability identification is added until the frequency fluctuation of alternating current systems at two sides of a direct current connecting line is smaller than a set value, the power value on the current direct current connecting line is kept unchanged, frequency correction control is carried out, additional power adjustment values are input into the system, the system frequency at one side with the deviation value between the current system frequency and the system steady-state frequency exceeding an allowable range is corrected, when the system reaches the lowest safe operation frequency, secondary frequency modulation control is started, the system frequency is adjusted without difference, and the system operation frequency is rapidly recovered to the steady-state operation frequency.

Description

Frequency emergency support and quick recovery control method and system for direct current interconnection system
Technical Field
The invention belongs to the field of direct-current power transmission control operation, and particularly relates to a frequency emergency support and quick recovery control method and system for a direct-current interconnection system.
Background
With the development of energy internet, the demand of long-distance power transmission is continuously increased, the power generation proportion of renewable energy sources is continuously improved, and the traditional alternating current power transmission faces a plurality of technical challenges in the aspects of large-scale new energy access and long-distance energy transmission. To further improve the flexibility, economy and reliability of power systems, the interconnection of power grids is increasingly scaled. Due to the complexity of the interconnected network structure, the load characteristics of each region and the system operation mode have significant differences. When the interconnected system suffers disturbance, the stability of the regional power grid is affected, and the interconnected system faces problems of low-frequency oscillation, cascading failure and the like. Because the direct current power has insensitivity to the frequency fluctuation of the alternating current power grid, the direct current connecting lines are used for interconnecting the alternating current power grids, the occurrence of cascading faults of the system can be effectively reduced on the basis of ensuring the flexibility and economy of the interconnected system, and the disturbance resistance of the interconnected system is improved.
Currently, some electric utilities have attempted to power support and frequency stability control of systems subject to disturbances using conventional direct current transmission technology (LCC-HVDC). When LCC-HVDC power flow inversion control is carried out, the voltage polarity needs to be inverted, and the frequency control capability of the LCC-HVDC power flow inversion control is limited. The flexible direct current transmission technology (VSC-HVDC) based on the voltage source type converter has the advantages of rapid power reversal capability, independent control of active power and reactive power, black start, capability of being connected with a weak alternating current network and the like, and can improve the mutual support capability of interconnected systems and the flexibility of regional standby complementation.
Because the direct-current transmission has rapid and accurate frequency response capability, the frequency of the alternating-current power grid is controlled through the direct-current transmission, rapid power support can be realized during fault, and the transient safety of the alternating-current power grid is ensured; during steady-state operation, the system self reserve capacity can be reduced in a mode of sharing the system reserve capacity, and the economic benefit of the system is obviously improved. Taking the power grid of the united states as an example, three major power grids (WECC, EI and ERCOT) are based on historical power supply removal accident information, and the requirements of the hot standby capacity of the system are 2740MW,4500MW and 2750MW respectively. After the addition of the dc links, the system hot spare capacity of each grid can be reduced by 1800MW, assuming that each dc link can deliver 900MW emergency power support. In view of The economics of sharing system back-up capacity using dc links, The Pacific National Laboratory in north west (The Pacific north National Laboratory) is also exploring The feasibility of frequency stability control of north american power grids using multi-terminal flexible dc transmission.
In recent years, research on stable control of frequency of an interconnection system by using direct current transmission has been conducted at home and abroad. The literature proposes a multipurpose dc network that can achieve frequency response, connect different types of loads and renewable energy, and improve the efficiency of energy transactions. To the inventor's knowledge, there is an additional frequency control strategy based on local control in the existing literature to achieve power support for one ac system when it experiences large frequency fluctuations. However, emergency power support in case of accident is only a part of the system frequency recovery process, which is a complicated process. At present, domestic and foreign researches mainly focus on direct current power support response after disturbance occurs, and few researches are made on how a direct current system and an alternating current system perform effective and economic cooperative control after power support.
Disclosure of Invention
The invention provides a frequency emergency support and rapid recovery control method and system of a direct current interconnection system to solve the problems, and the invention can realize emergency power support in an accident and reduce the frequency variation after the alternating current system accident; and the system continues to participate in the system frequency recovery process after the accident, so that the effects of stabilizing the frequency and accelerating the system frequency recovery are achieved.
In order to achieve the purpose, the invention adopts the following technical scheme:
a frequency emergency support and quick recovery control method for a direct current interconnection system is characterized in that after an electric power system is disturbed, direct current emergency support control is carried out by taking frequency deviation values on two sides as control values, frequency stability identification is added until frequency fluctuation of alternating current systems on two sides of a direct current connecting line is smaller than a set value of the alternating current systems, the power value on the current direct current connecting line is kept unchanged, frequency correction control is carried out, an additional power adjustment value is input into the system, one side system frequency with the deviation value of the current system frequency and the system steady-state frequency exceeding an allowable range is corrected, when the system reaches the lowest safe operation frequency, secondary frequency modulation control is started, the system frequency is adjusted in a non-differential mode, and the system operation frequency is quickly recovered to the steady-state operation frequency.
Further, the direct current emergency support control simultaneously responds to the frequency change condition of alternating current systems at two sides of the direct current tie line and adjusts the power of the direct current tie line at any time; by setting different frequency deviation dead zones and control slopes, the response capability of the two-side converter stations to the frequency fluctuation of the alternating current system on the other side is independently adjusted under the condition that the frequency modulation capability of the alternating current systems on the two sides is different, the emergency power support is provided for the alternating current system on the opposite side while the safe operation of the alternating current system on the side is ensured, and the condition that the power support system provides power support exceeding the self standby capacity for the supported system is prevented.
Further, when the system frequency tends to be stable, the direct current connecting line keeps the current direct current control quantity; and adding frequency stabilization identification control to ensure that the direct current connecting line automatically keeps the power quantity on the current direct current connecting line after the system frequency is stabilized.
Furthermore, in the process of frequency stability identification control, the frequency fluctuation condition of the system is judged by monitoring the change of the first derivative of the frequency of an alternating current system connected with the direct current station, and the frequency target derivative value can be adjusted according to the actual condition of the systems on two sides of the direct current connecting line; and when the frequency fluctuation of the alternating current systems on the two sides of the direct current tie line is smaller than the set value, keeping the power quantity on the current direct current tie line unchanged.
Further, if the system is disturbed again, the dc emergency support control will again be involved in stabilizing the ac system frequency when the frequency fluctuation is greater than the frequency target derivative setting by the frequency stability identification.
Further, if the stabilized frequency of the system on one side of the direct current tie line exceeds the safe operation frequency range, the control inputs an additional power adjustment amount into the system, and corrects the frequency of the system on the side so as to enable the frequency to continuously rise to the safe frequency limit value.
Furthermore, in the process of frequency correction control, the set frequency margin is subtracted from the deviation target value of the set safety frequency and the system steady-state frequency so as to ensure that the frequency can be stabilized at the lowest safe operation frequency.
Further, direct current frequency modulation recovery control is adopted, so that the direct current tie line continuously participates in system secondary frequency modulation control, the difference adjustment coefficient represented by the direct current tie line in the system is determined, and the generator participating in secondary frequency modulation is subjected to non-difference adjustment product-difference adjustment according to the difference adjustment coefficient.
Furthermore, the difference adjustment coefficient is a ratio of a per unit value of the current frequency and the system frequency deviation amount to a per unit value of the direct current power deviation amount.
A frequency emergency support and fast recovery control system of a direct current interconnection system comprises a primary frequency modulation controller and a secondary frequency modulation controller, wherein:
the primary fm controller includes a dc emergency support controller, a frequency stability identification controller, and a frequency correction controller configured to: when the system frequency is abnormally fluctuated, the system is put into operation, and the direct current emergency support controller starts to provide emergency power support for the disturbed system; the frequency stabilization identification controller identifies the frequencies on two sides of the direct current tie line in real time; when the frequencies on the two sides of the line are stable, the frequency stability identification controller sends a signal to keep the current direct current control quantity of the direct current emergency support control unchanged, and simultaneously, the frequency correction controller is started; when the system reaches the lowest safe operation frequency, the direct current connecting line quits the primary frequency modulation control;
and the secondary frequency modulation controller is configured to realize the adjustment of the system frequency without difference by matching with a frequency modulation unit of the system when the direct current frequency modulation recovery control receives a starting signal, and quickly recover the system operation frequency to the steady state operation frequency.
Compared with the prior art, the invention has the beneficial effects that:
1. by changing the structure of the split-range partition plate, the invention can realize the weld seam flaw detection, ensure the product quality, improve the problems of the operating environment of operators and the like, and achieve multiple purposes.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this application, illustrate embodiments of the application and, together with the description, serve to explain the application and are not intended to limit the application.
FIG. 1 is an exemplary diagram of a visual notification of a fault;
FIG. 2 is a network security topology;
FIG. 3 is a schematic diagram showing the distance between two points of a sphere;
FIG. 4 is a reflection and refraction of a traveling fault wave when a fault occurs in a cable run;
FIG. 5 is a catadioptric view of a fault traveling wave when the fault occurs on an overhead line;
FIG. 6 is a flowchart of an algorithm routine;
the specific implementation mode is as follows:
the invention is further described with reference to the following figures and examples.
It should be noted that the following detailed description is exemplary and is intended to provide further explanation of the disclosure. Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs.
It is noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments according to the present application. As used herein, the singular forms "a", "an" and "the" are intended to include the plural forms as well, and it should be understood that when the terms "comprises" and/or "comprising" are used in this specification, they specify the presence of stated features, steps, operations, devices, components, and/or combinations thereof, unless the context clearly indicates otherwise.
In the present invention, terms such as "upper", "lower", "left", "right", "front", "rear", "vertical", "horizontal", "side", "bottom", and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the drawings, and are only terms of relationships determined for convenience of describing structural relationships of the parts or elements of the present invention, and are not intended to refer to any parts or elements of the present invention, and are not to be construed as limiting the present invention.
In the present invention, terms such as "fixedly connected", "connected", and the like are to be understood in a broad sense, and mean either a fixed connection or an integrally connected or detachable connection; may be directly connected or indirectly connected through an intermediate. The specific meanings of the above terms in the present invention can be determined according to specific situations by persons skilled in the relevant scientific or technical field, and are not to be construed as limiting the present invention.
The present embodiment is described in detail in the following aspects:
(1) a DC emergency support control is provided to make the DC link participate in the primary frequency modulation of the system, so as to reduce the frequency variation after the AC system accident.
(2) In order to automatically maintain the power amount of the direct current link after the system frequency is stabilized, a frequency stabilization identification control is provided, which can start an emergency support control when the system frequency changes and prevent frequency oscillation after the frequency is stabilized.
(3) In order to ensure that the stable frequency is in a safe range after the system frequency is stable, frequency correction control is provided to ensure that the system operates in the safe frequency range.
(4) In order to improve the secondary frequency modulation speed of the system, a direct current frequency modulation recovery control is provided, so that a direct current connecting line continuously participates in the secondary frequency modulation control of the system after participating in the primary frequency modulation control of the system.
As shown in fig. 1, the overall process of frequency control response after a given system is disturbed is shown. In an electric power system, the frequency of a power grid reflects the balance relationship between generated power and load, and is an important control parameter for the operation of the electric power system. Power system frequency control is considered to be one of the most important secondary controls. Through frequency control, the system frequency can stably operate within an acceptable safety range. Frequency control after a power system is disturbed can be generally divided into two stages: primary frequency modulation control and secondary frequency modulation control.
The primary fm control belongs to the emergency power support control. When the system is disturbed (taking the generator in the system as an example of the station drop), the primary frequency modulation control changes the output of the prime motor through the speed regulator, and the frequency variation of the power grid is reduced by utilizing the self frequency modulation function of the generator in the system. At present, the online standby capacity of the domestic power grid is mainly based on a coal-fired generator. Due to the characteristic limitation of the coal-fired unit, the adjusting capacity of the coal-fired unit is relatively poor, and the time for reaching the target load is long. When the system is greatly disturbed, the transient frequency of the system can be too low, so that the low-frequency load shedding is caused, and the safe and stable operation of the system is threatened. Meanwhile, the requirement of primary frequency modulation control on the rotating reserve capacity of the system is high, and the economic benefit of the system is reduced during normal operation. The secondary frequency modulation control of the system belongs to frequency recovery control. After the primary frequency modulation control is finished, the stable frequency of the power grid is gradually recovered by the secondary frequency modulation control and generally in an AGC mode. At present, the frequency recovery of the secondary frequency modulation control from participation to completion generally needs 3 to 15 minutes, in the period, the system is in the non-rated frequency operation, and the longer the frequency modulation time is, the greater the influence on the safe and economic operation of equipment is.
Direct current transmission is used for participating in primary frequency modulation control of the system, and when the system runs stably, the rotation standby of the system can be reduced, and the running benefit of the system is improved; when the system is disturbed, the direct current transmission is utilized to carry out rapid power support, and the transient stability of the system is improved. After the system is stabilized, direct current transmission is used for participating in secondary frequency modulation control of the system, so that the rapid recovery of frequency can be realized, and the operating time of the system under the working condition of non-rated frequency is reduced.
Fig. 2 shows a dc frequency support and recovery control method proposed herein. The dc frequency support and recovery control strategy specifically includes the following parts: (1) direct current emergency support control, (2) frequency stabilization identification, (3) frequency correction control, and (4) direct current frequency modulation recovery control. Wherein, the direct current emergency support control, the frequency stability identification and the frequency correction control correspond to the system primary frequency modulation control and are collectively called direct current frequency support control; and D, restoring and controlling the secondary frequency modulation of the corresponding system by the direct current frequency modulation.
The dc emergency support control aims to reduce the frequency variation after an ac system accident. In a conventional converter station, a fixed proportionality coefficient is mostly adopted for direct current frequency control, and the frequency modulation capability of an opposite-side alternating current system participating in frequency modulation is not considered, so that a large deviation may occur to the frequency of the opposite-side alternating current system in the process of supporting direct current power, and the safe and stable operation of the opposite-side alternating current system is affected. To avoid this problem, the amount of both-side frequency deviation is used herein as a control amount.
As shown in fig. 3, a controller structure of the proposed dc emergency support control is provided. In the figure, frefiIs the steady-state frequency of the system, fi is the actual frequency of the system, Ki represents the regulation slope of active power-frequency, fdeadbandFor frequency deviation dead band, i is 1 or 2, Pmax/PminFor active power control upper/lower limits, PfecyAnd controlling the output active power value for the direct current emergency support.
The system on both sides of the DC link is assumed to be the system I and the system II. When the frequency of the system is decreased due to disturbance, the dc link power is changed to:
PDC＝Pref+K1*(fref1-f1) (1)
the second system will provide additional power to the first system to stabilize the first system frequency. At this time, the unbalanced power of the second system occurs, the frequency is also reduced, and the power of the dc link at this time is:
PDC＝Pref+K1*(fref1-f1)+K2*(fref2-f2) (2)
as can be seen from the expressions (1) and (2), the dc emergency support control can adjust the dc link power at any time in response to the frequency change of the ac systems on both sides of the dc link. By setting different frequency deviation dead zones and control slopes, the response capability of the two-side converter stations to the frequency fluctuation of the alternating current system on the other side can be independently adjusted under the condition that the frequency modulation capability of the alternating current systems on the two sides is different, the emergency power support is provided for the alternating current system on the opposite side while the safe operation of the alternating current system on the side is ensured, and the condition that the power support system provides power support exceeding the self standby capacity for the supported system is prevented.
The purpose of the dc emergency support control is to reduce the amount of frequency change after an ac system accident. When the system frequency tends to be stable, the direct current connecting line should keep the current direct current control quantity. In order to make the direct current connecting wire automatically keep the power quantity of the current direct current connecting wire after the system frequency is stabilized, a frequency stabilization identification controller is added on the basis of direct current emergency support control.
As shown in fig. 4, the frequency stability identification controller is configured. In the figure, f is the actual frequency of the system, f'setThe signal is the signal output by the controller after the frequency is stabilized. The controller judges the system frequency fluctuation condition by monitoring the first derivative change of the frequency of the alternating current system connected with the direct current station. Because the steady-state frequency of the system still fluctuates in a small range, different frequency target derivative values can be set according to the actual conditions of the systems on two sides of the direct current connecting line. When the frequency fluctuation of the alternating current systems on the two sides of the direct current tie line is smaller than the set value, the controller sends out a signal to keep the power quantity on the current direct current tie line unchanged.
The frequency stability identification control can identify the frequency fluctuation condition of the systems on both sides at the same time, and the direct current emergency support control is quitted after the systems on both sides are ensured to be stable. Meanwhile, if the system is disturbed again, through frequency stabilization identification, when the frequency fluctuation is larger than the frequency target derivative set value, the direct current emergency support control is involved again in stabilizing the alternating current system frequency.
In some cases, due to insufficient speed regulation capability of the generator inside the system, although the frequency variation of the ac system is reduced by the dc emergency support control, the frequency after the system is stabilized may not be within the safe operating frequency range. At present, the frequency deviation limit value under the normal operation condition of the power system in China does not exceed +/-0.2 HZ. In order to ensure that the system is in a safe operation frequency range after being stabilized, frequency correction control is added after the system frequency is stabilized.
As shown in fig. 5, the controller structure of the frequency correction control is shown. Δ fsafeTo a safety frequency fsafeAnd the system steady-state frequency frefDeviation target value, Δ Psafe-MWThe power adjustment quantity output after the frequency correction control is obtained.
As shown in fig. 5, when the system frequency is stable, the frequency correction control is enabled to determine whether the deviation amount between the current system frequency and the system steady-state frequency is within the allowable range. If the stabilized frequency of the system on one side of the direct current tie line exceeds the safe operation frequency range, the control inputs an additional power adjustment quantity delta P to the systemsafe-MWThe side system frequency is corrected to continue rising to the safe frequency limit.
ΔPsafe-MW＝K3*(Δf1-Δfsafe1)+K4*(Δf2-Δfsafe2) (3)
There may be a problem with the control system in that there is a deviation in the control output from the set minimum safe operating frequency value. Therefore, on the basis of the set minimum safe operation frequency, a frequency margin is added to ensure that the frequency can be stabilized at the minimum safe operation frequency after the control is finished:
Δfsafe＝fref-fsafe- (4)
the frequency correction control can simultaneously judge the frequency condition of the stable systems on the two sides of the direct current tie line, and the safe and stable operation of the systems on the two sides is ensured. The frequency correction control is started by a signal identified by frequency stability, so that the direct current emergency support control is prevented from being influenced by simultaneous operation during the direct current emergency support control.
The primary frequency modulation control of the system belongs to difference adjustment, and when the system stabilizes the frequency through the primary frequency modulation control, a certain difference value generally exists between the frequency and the steady-state operation frequency. In order to restore the system frequency to the steady state operating frequency, a system chirp control is required. In order to enable the system to recover to the rated operation frequency as soon as possible, after the direct current connecting line participates in the primary frequency modulation control of the system, the direct current frequency modulation recovery control is adopted, the direct current connecting line continues to participate in the secondary frequency modulation control of the system, and the secondary frequency modulation speed of the system is improved.
Considering that the dc link participates in the secondary frequency modulation of the system, the difference coefficient represented by the dc link in the system should be determined. According to the secondary frequency modulation characteristic of the power system, the difference coefficient K of the secondary frequency modulation characteristicDCCan be expressed as:
Figure BDA0001741283320000111
wherein, Δ f is a per unit value of the deviation amount between the current frequency and the system frequency; delta PDCIs the per unit value of the DC power deviation value; Δ f is the deviation of the current frequency and the system frequency; f. of0Is the system steady-state frequency; delta PDCIs the amount of power deviation; pDC0Is the converter station capacity.
Assuming that n generators participating in secondary frequency modulation are arranged in a disturbed system, adopting a product-difference adjusting method without difference adjustment, considering that direct current participates in secondary frequency modulation, the method comprises the following steps:
Figure BDA0001741283320000112
wherein, Δ f is the per unit value of the deviation between the current frequency and the system frequency; delta PGiThe active power variation per unit value of the ith frequency modulation unit; kGiThe difference adjusting coefficient of the difference adjuster of the ith frequency adjusting unit.
The direct current frequency modulation recovery control participates in the system secondary frequency modulation control, and the system frequency modulation equation is as follows:
Figure BDA0001741283320000113
where Δ P is a per unit value of the power increase required to recover the system steady-state frequency.
Assuming that the frequencies of the various points in the system are identical, the integral ^ Δ f × dt of the frequencies of the various units can be considered equal. Then there are:
Figure BDA0001741283320000121
in the secondary frequency modulation of the system, the per unit value of the secondary frequency modulation power of the system borne by the direct current tie line is as follows:
Figure BDA0001741283320000122
wherein, KSecondaryControlling the power distribution coefficient for direct current frequency modulation recovery:
Figure BDA0001741283320000123
as shown in fig. 6, the overall controller structure of the proposed dc frequency support and recovery control strategy is shown. When the system frequency fluctuates abnormally, the system primary frequency modulation control intervenes. At this point, the DC emergency support control initiates the provision of emergency power support to the disturbed system. Meanwhile, the frequency stability identification controller identifies the frequencies on the two sides of the direct current tie line in real time. When the frequencies on the two sides of the line are stable, the frequency stability identification controller sends out a signal to keep the current direct current control quantity of the direct current emergency support control unchanged, and meanwhile, the frequency correction control is started. And when the system reaches the lowest safe operation frequency, the direct current tie line quits the primary frequency modulation control, and the primary frequency modulation control of the system is finished.
After the secondary frequency modulation control of the system is started, the direct current frequency modulation recovery control receives a starting signal, and the direct current frequency modulation recovery control is matched with a frequency modulation unit of the system to realize the adjustment of the system frequency without difference and quickly recover the system operating frequency to the steady state operating frequency.
The above description is only a preferred embodiment of the present application and is not intended to limit the present application, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, improvement and the like made within the spirit and principle of the present application shall be included in the protection scope of the present application.
Although the embodiments of the present invention have been described with reference to the accompanying drawings, it is not intended to limit the scope of the present invention, and it should be understood by those skilled in the art that various modifications and variations can be made without inventive efforts by those skilled in the art based on the technical solution of the present invention.

Claims (9)

1. A frequency emergency support and fast recovery control method of a direct current interconnection system is characterized in that: when the power system is disturbed, performing direct current emergency support control by using frequency deviation quantities at two sides as control quantities, adding frequency stability identification until the frequency fluctuation of alternating current systems at two sides of a direct current tie line is smaller than a set value, keeping the power quantity on the current direct current tie line unchanged, performing frequency correction control, inputting an additional power regulation quantity into the system, correcting the system frequency at one side of which the deviation quantity of the current system frequency and the system steady-state frequency exceeds an allowable range, starting secondary frequency modulation control when the system reaches the lowest safe operation frequency, performing no-difference adjustment on the system frequency, and realizing that the system operation frequency is quickly recovered to the steady-state operation frequency;
when the system frequency tends to be stable, the direct current connecting line keeps the current direct current control quantity; and adding frequency stabilization identification control to ensure that the direct current connecting line automatically keeps the power quantity on the current direct current connecting line after the system frequency is stabilized.
2. The method as claimed in claim 1, wherein the frequency emergency support and fast recovery control method of the dc interconnect system comprises: the direct current emergency support control simultaneously responds to the frequency change condition of alternating current systems at two sides of the direct current tie line and adjusts the power of the direct current tie line at any time; by setting different frequency deviation dead zones and control slopes, the response capability of the two-side converter stations to the frequency fluctuation of the alternating current system on the other side is independently adjusted under the condition that the frequency modulation capability of the alternating current systems on the two sides is different, the emergency power support is provided for the alternating current system on the opposite side while the safe operation of the alternating current system on the side is ensured, and the condition that the power support system provides power support exceeding the self standby capacity for the supported system is prevented.
3. The method as claimed in claim 1, wherein the frequency emergency support and fast recovery control method of the dc interconnect system comprises: in the process of frequency stability identification control, the frequency fluctuation condition of the system is judged by monitoring the change of the first derivative of the frequency of an alternating current system connected with a direct current station, and the frequency target derivative value is adjustable according to the actual condition of the systems at two sides of the direct current connecting line; and when the frequency fluctuation of the alternating current systems on the two sides of the direct current tie line is smaller than the set value, keeping the power quantity on the current direct current tie line unchanged.
4. The method as claimed in claim 1, wherein the frequency emergency support and fast recovery control method of the dc interconnect system comprises: if the system is disturbed again, the direct current emergency support control is again involved in stabilizing the alternating current system frequency when the frequency fluctuation is greater than the frequency target derivative set value through frequency stability identification.
5. The method as claimed in claim 1, wherein the frequency emergency support and fast recovery control method of the dc interconnect system comprises: if the stabilized frequency of the system on one side of the direct current tie line exceeds the safe operation frequency range, the control inputs an additional power adjustment amount into the system, and corrects the frequency of the system on the side so as to enable the frequency to continuously rise to the safe frequency limit value.
6. The method as claimed in claim 1, wherein the frequency emergency support and fast recovery control method of the dc interconnect system comprises: in the process of frequency correction control, the set frequency margin is subtracted from the deviation target value of the set safety frequency and the system steady-state frequency so as to ensure that the frequency can be stabilized at the lowest safe operation frequency.
7. The method as claimed in claim 1, wherein the frequency emergency support and fast recovery control method of the dc interconnect system comprises: and D, adopting direct-current frequency modulation recovery control to enable the direct-current tie line to continuously participate in system secondary frequency modulation control, determining a difference adjustment coefficient represented by the direct-current tie line in the system, and performing non-difference adjustment product-difference adjustment on the generator participating in the secondary frequency modulation according to the difference adjustment coefficient.
8. The method as claimed in claim 7, wherein the frequency emergency support and fast recovery control method of the dc interconnect system comprises: and the difference adjustment coefficient is the ratio of the per-unit value of the current frequency and the system frequency deviation amount to the per-unit value of the direct current power deviation amount.
9. A frequency emergency support and fast recovery control system of a direct current interconnection system is characterized in that: including primary control ware and secondary control ware, wherein:
the primary fm controller includes a dc emergency support controller, a frequency stability identification controller, and a frequency correction controller configured to: when the system frequency is abnormally fluctuated, the system is put into operation, and the direct current emergency support controller starts to provide emergency power support for the disturbed system; the frequency stabilization identification controller identifies the frequencies on two sides of the direct current tie line in real time; when the frequencies on the two sides of the line are stable, the frequency stability identification controller sends a signal to keep the current direct current control quantity of the direct current emergency support control unchanged, and simultaneously, the frequency correction controller is started; when the system reaches the lowest safe operation frequency, the direct current connecting line quits the primary frequency modulation control;
and the secondary frequency modulation controller is configured to realize the adjustment of the system frequency without difference by matching with a frequency modulation unit of the system when the direct current frequency modulation recovery control receives a starting signal, and quickly recover the system operation frequency to the steady state operation frequency.
CN201810820526.2A 2018-07-24 2018-07-24 Frequency emergency support and quick recovery control method and system for direct current interconnection system Active CN108879729B (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
CN201810820526.2A CN108879729B (en) 2018-07-24 2018-07-24 Frequency emergency support and quick recovery control method and system for direct current interconnection system

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
CN201810820526.2A CN108879729B (en) 2018-07-24 2018-07-24 Frequency emergency support and quick recovery control method and system for direct current interconnection system

Publications (2)

Publication Number Publication Date
CN108879729A CN108879729A (en) 2018-11-23
CN108879729B true CN108879729B (en) 2020-11-27

Family

ID=64304700

Family Applications (1)

Application Number Title Priority Date Filing Date
CN201810820526.2A Active CN108879729B (en) 2018-07-24 2018-07-24 Frequency emergency support and quick recovery control method and system for direct current interconnection system

Country Status (1)

Country Link
CN (1) CN108879729B (en)

Families Citing this family (5)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN111654040A (en) * 2020-06-17 2020-09-11 浙江大学 Frequency supporting method of interconnected power system containing HVDC (high voltage direct current) with consideration of support of transmitting end and receiving end
CN113013930B (en) * 2021-03-04 2022-03-11 山东大学 Secondary frequency modulation control method and system for flexible direct current delivery of virtual power plant
CN113241778A (en) * 2021-05-25 2021-08-10 云南电网有限责任公司电力科学研究院 AGC control method based on multi-region interconnected power grid
CN113452039B (en) * 2021-07-16 2023-05-26 云南电网有限责任公司电力科学研究院 Frequency modulation method and system for new energy station
CN113422377B (en) * 2021-08-25 2021-11-09 中国电力科学研究院有限公司 DC modulation and secondary frequency modulation coordinated optimization configuration method and device

Family Cites Families (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2744182B2 (en) * 1992-12-09 1998-04-28 株式会社東芝 DC interconnection frequency controller
CN103384068B (en) * 2013-03-25 2016-02-24 南京南瑞集团公司 Transient Security for Power Systems stablizes emergency control strategy of on-line optimized calculation method
CN103986170B (en) * 2014-03-05 2016-08-31 国家电网公司 A kind of DC transmission system combines the startup method of frequency modulation with generating set
CN107046291B (en) * 2017-04-25 2019-11-05 国网四川省电力公司电力科学研究院 Steady frequency calculation method and system after a kind of asynchronous operation grid disturbance
CN107294127B (en) * 2017-08-14 2019-07-05 郑州轻工业学院 A kind of adaptive HVDC emergency DC power support method
CN108011390B (en) * 2017-12-11 2019-10-08 华中科技大学 A kind of back-to-back flexible HVDC transmission system and bicyclic additional frequency control method

Also Published As

Publication number Publication date
CN108879729A (en) 2018-11-23

Similar Documents

Publication Publication Date Title
CN108879729B (en) Frequency emergency support and quick recovery control method and system for direct current interconnection system
JP5308511B2 (en) Output control method and output control apparatus for wind power generation equipment
US20210325922A1 (en) Method and apparatus for control of intelligent loads in microgrids
CN107240934B (en) AC/DC hybrid micro-grid multi-mode operation coordination control method and smooth switching method
BRPI0621491A2 (en) SYSTEM AND METHODS FOR A SELF-HEALING GRID USING SIDE DEMAND MANAGEMENT AND ENERGY STORAGE TECHNIQUES
CN110137999B (en) Direct-current power coordination control method and system with participation of receiving-end wind power plant
CN107681688A (en) Possess the grid-connected converter and its isolated island method of discrimination and device of VSG features
CN115864520A (en) Control method and system for accessing hybrid power grid based on high-proportion photovoltaic energy
JP6376997B2 (en) Power system and control method of power system
Azad et al. Stability enhancement of a DC-segmented AC power system
JP2017147875A (en) Reactive power output device, control method for reactive power output device, and power system
CN116250156A (en) Fault control device and method for power distribution system
US11898540B2 (en) Method for feeding electrical power into an electrical supply network
WO2020030671A1 (en) Grid-connected p-v inverter system and method of load sharing thereof
WO2023206959A1 (en) Micro-grid control method and apparatus, and power supply control method and apparatus
US20220294229A1 (en) Method and stabilization controller for operating a stand-alone grid
Gebremariam et al. Enhanced dc-link voltage control in a virtual synchronous generator-based building-to-building grid considering islanded mode operation
CN111654040A (en) Frequency supporting method of interconnected power system containing HVDC (high voltage direct current) with consideration of support of transmitting end and receiving end
CN109659965A (en) A kind of flexible HVDC transmission system active power controller method and system
CN112054550A (en) Direct-current power mutual-aid method of multi-loop extra-high voltage direct-current feed-in alternating-current system
Ahmed et al. BESS Assisted Frequency Management for Black Start Process of Microgrid
Fahad et al. Functions of microgrid hierarchal control structure
WO2020170626A1 (en) Wide area participation-type autonomous blackout avoidance control device
JP6791343B1 (en) Distributed power system
CN117955178B (en) Thermal power starting and output configuration method suitable for large-scale wind power direct current end system

Legal Events

Date Code Title Description
PB01 Publication
PB01 Publication
SE01 Entry into force of request for substantive examination
SE01 Entry into force of request for substantive examination
GR01 Patent grant
GR01 Patent grant