CN107342587A - A kind of dc power in real time can hoisting power computational methods - Google Patents

A kind of dc power in real time can hoisting power computational methods Download PDF

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CN107342587A
CN107342587A CN201710583567.XA CN201710583567A CN107342587A CN 107342587 A CN107342587 A CN 107342587A CN 201710583567 A CN201710583567 A CN 201710583567A CN 107342587 A CN107342587 A CN 107342587A
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mrow
msub
power
current
max
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CN107342587B (en
Inventor
吴雪莲
李兆伟
方勇杰
刘福锁
李威
李碧君
黄慧
王燕君
张子龙
谭真
崔晓丹
侯玉强
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State Grid Corp of China SGCC
Nari Technology Co Ltd
State Grid Shanghai Electric Power Co Ltd
Nanjing NARI Group Corp
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State Grid Corp of China SGCC
Nari Technology Co Ltd
State Grid Shanghai Electric Power Co Ltd
Nanjing NARI Group Corp
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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
    • 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
    • H02J3/04—Circuit arrangements for ac mains or ac distribution networks for connecting networks of the same frequency but supplied from different sources
    • H02J3/06—Controlling transfer of power between connected networks; Controlling sharing of load between connected 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
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J2203/00—Indexing scheme relating to details of circuit arrangements for AC mains or AC distribution networks
    • H02J2203/20—Simulating, e g planning, reliability check, modelling or computer assisted design [CAD]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J3/00—Circuit arrangements for ac mains or ac distribution networks
    • H02J3/001—Methods to deal with contingencies, e.g. abnormalities, faults or failures
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
    • Y02E60/00—Enabling technologies; Technologies with a potential or indirect contribution to GHG emissions mitigation
    • Y02E60/60—Arrangements for transfer of electric power between AC networks or generators via a high voltage DC link [HVCD]

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

Abstract

The invention discloses a kind of dc power in real time can hoisting power computational methods, belong to Power System and its Automation technical field.The present invention is based on the current operating condition of direct current, the capability of overload of direct current self character decision is considered, the section ability to bear of the AC network of AC network sending end and receiving end, including the defeated scattered ability of trend and transient stability ability, and rectification side is limited by three aspects of the real-time maximum transmission capacity of power of alternating voltage enabling capabilities and current triggering angle value, so that it is determined that dc power in real time can hoisting power.The present invention is realizes that power Emergency Assistance provides effective controlled quentity controlled variable, it is ensured that HVDC Modulation function can be played effectively, the problems such as so as to alleviate the unbalanced power of power network, improve the security and stability of power network.

Description

Calculation method for real-time capacity improvement of direct current power
Technical Field
The invention belongs to the technical field of power systems and automation thereof, and more particularly relates to a calculation method for improving the real-time capacity of direct-current power.
Background
At present, a grid structure with multiple direct current feeds is formed in multiple regions in China, and compared with other emergency control measures of an alternating current system, the grid structure with the multiple direct current feeds utilizes the emergency power support (EDCPS) capability of the direct current system, and has the advantages of improving the transient stability of the alternating current system under high-power impact disturbance, being lower in control cost and being faster and more reliable in control. However, there is no clear calculation method for the real-time boost capability of the direct current power, and generally only the overload capability of the direct current power transmission can be obtained, and the long-term maximum overload current is generally 1.1 times of the rated current; the transient overload capacity can reach 1.5 times of rated current and can last for 3 s. However, whether the dc system can reach the maximum overload operation state instantaneously in any operation mode has a significant influence on the emergency control effect, because an unreasonable dc power emergency boost command may not only cause that the actual boost amount does not reach the set value, but also may damage the safe and stable operation of the system, thereby causing a cascading failure.
For an alternating current transmission system, especially for ultrahigh voltage and extra-high voltage direct current, because the capacity of direct current transmission is large, when the direct current runs at full power, the tidal current of a direct current near-zone section is heavy, and after the direct current power is increased, certain influence is generated on the static stability and the transient stability margin of a near-zone channel. When the direct current power is increased, firstly, it is ensured that the section current of the near region does not exceed the limit of thermal stability and transient stability.
For a direct current transmission system, the change of the transmission current of the direct current transmission system can be realized by adjusting the trigger control angle of the rectifying side and the inverter side and the valve side no-load voltage of the converter transformer of the rectifying side and the inverter side, wherein the trigger angle has extremely fast response speed which is usually within 1-4 ms, and the valve side no-load voltage is adjusted by changing the transformation ratio of the converter transformer, so the response speed is much slower than the adjustment of the trigger control angle, and generally 5-10 s are neededminControl (α)minThe minimum trigger delay angle of the rectifier station) to limit the promotion of direct current active work, at the moment, the inverter side is automatically switched to constant current control, and the setting value of the inverter side is 0.1p.u. smaller than that of the rectifier side. Because the direct current emergency boost power needs a large amount of reactive support, unreasonable direct current boost instructions may deteriorate the system voltage, even leading to direct current commutation failure. Therefore, when the voltage supporting capability of the ac system is insufficient and the reactive power compensation is insufficient, the real-time boost capability of the dc power needs to be determined, so as to ensure that the dc power boost can be accurately and effectively boosted to the target value following the command.
Disclosure of Invention
The purpose of the invention is: aiming at the defects of the prior art, a calculation method for the real-time capacity improvement of the direct current power is provided.
Specifically, the invention is realized by adopting the following technical scheme, which comprises the following steps:
1) obtaining the maximum overload power P of the direct current capable of safely operating in short timemax.dcObtaining the maximum liftable power delta P restricted by the direct current self-capabilitymax.dcComprises the following steps:
ΔPmax.dc＝Pmax.dc-P0
wherein, P0The current direct current active power;
2) according to the current operation grid structure and operation mode of the power grid, determining that the maximum Direct Current (DC) power that can be increased is delta P determined by the cross-section tidal current transmission capacity of the AC systemmax.ac；
3) Determining the maximum power P capable of running in real time according to the current running mode of the direct currentmax.onObtaining the maximum liftable power delta P restricted by the DC operation modemax.onComprises the following steps:
ΔPmax.on＝Pmax.on-P0
4) the real-time DC power boost capability integrating multiple limiting factors is as follows:
ΔPmax＝min(ΔPmax.ac,ΔPmax.dc,ΔPmax.on)
5) based on the on-line real-time data, checking that the current DC power is increased to P ═ P0+ΔPmaxThe transient stability of the time alternating current system is judged, and if the transient stability margin is smaller than the lower operation limit allowed by the system, the delta P is mademax＝ΔPmaxChecking when the DC power is increased to P ═ P0+ΔPmaxThe transient stability of the time alternating current system, wherein P is a gradient value for gradually reducing the check power, and the smaller the value of P is, the more accurate the obtained direct current can improve the power in real time; otherwise, when Δ PmaxWhen the direct current power is more than 0, the direct current power real-time boost capability is delta Pmax(ii) a When Δ PmaxWhen the current is less than or equal to 0, the direct current does not have the real-time power increasing capability.
The above technical solution is further characterized in that, in the step 2), a method for determining the maximum dc power that can be increased, which is determined by the cross-sectional power flow transfer capability of the ac system, is as follows.
Let the AC section with coupling property with DC transmission power be end face j, and its stable limit of transmission power be PjmaxTherefore, the maximum allowable DC boost power is limited by the stable operating limit of section j
In the formula, Pj0The current operation trend of the section j is obtained; k is a radical ofjThe change value of the section j tide is the change value when the direct current quantity of unit power is increased;
if there are n alternating current sections coupled with the direct current transmission power, the maximum allowable direct current boosted power is limited by the tidal current stable operation limit of the n coupling sections:
ΔPmax.ac＝min(ΔPmax.ac(1),ΔPmax.ac(j)…ΔPmax.ac(n))(j＝1,2……n)。
the above technical solution is further characterized in that, in the step 3), the method for determining the maximum power that can be operated in real time according to the current direct current operation mode specifically includes the following steps:
3-1) monitoring the current DC average value I0Direct voltage U from pole to ground of rectifier stationd0Trigger angle α of rectifier0Let X be the commutation reactance of each phase of the rectifier stationr1The DC loop resistance is R, and the minimum firing angle for DC enabled operation is αmin；
When α0＞αminIf so, turning to the step 3-2), otherwise, directly turning to the step 3-7);
3-2) calculating to obtain the effective value U of the no-load line voltage at the valve side of the converter transformer0Comprises the following steps:
wherein N is1The number of 6 pulsating converters in each pole of the converter station;
DC power of rectifier station is Pd0：
Pd0＝Ud0I0
Reactive power Q consumed by a converter station0Comprises the following steps:
3-3) if the increase of the current is Δ I, the increased current I1Comprises the following steps:
I1＝I0+ΔI
calculating the DC voltage U after the current increased1And DC power Pd1Comprises the following steps:
Ud1＝Ud0+RΔI
Pd1＝Ud1I1
3-4) solving the effective value of the no-load line voltage at the valve side of the converter transformer after the current is increased according to the Jacobian matrix at the AC side and the reactive power change consumed by the current converter of the rectifier station under the current state, wherein the specific method comprises the following steps:
from the point of view of the DC access point, the port characteristic of the AC system is expressed by a Jacobian matrix equation
P and Q are respectively active power and reactive power which are injected into the direct-current rectifying station by the alternating-current power grid; the phase angle difference between the alternating current equivalent potential of the equivalent alternating current single-port network and the alternating current voltage of the direct current access point; u is the amplitude of the alternating voltage of the direct current access point, and delta P, delta Q, delta and delta U respectively correspond to the variation of active power injected into the direct current rectifier station by the alternating current power grid, the variation of reactive power injected into the direct current rectifier station by the alternating current power grid, the variation of the phase angle difference between the alternating current equivalent potential and the alternating voltage of the direct current access point and the variation of the amplitude of the alternating current voltage of the direct current access point;
is a jacobian matrix, which is a matrix composed of the first partial derivatives of the corresponding functions, wherein,
at the moment, the effective value U of the valve-side no-load line voltage of the converter transformer1Comprises the following steps:
wherein,
3-5) calculating the firing angle α of the rectifier after the current increase1Comprises the following steps:
3-6) order I0＝I1，Ud0＝Ud1，α0＝α1If α0＞αminAnd returning to the step 3-2); otherwise, turning to the step 3-7);
3-7) direct current determined by the current mode of operation of direct currentMaximum operating power Δ Pmax.onComprises the following steps:
Pmax.on＝Ud0I0。
the invention has the following beneficial effects: the method of the invention utilizes the emergency power support capability of the direct current to quickly and effectively adjust the direct current power injected into the alternating current system under the condition of large disturbance fault of the system, compensates the transient unbalanced power of the receiving end power grid to the maximum extent and improves the transient stability of the system. The method can calculate the real-time lifting capability of the current power of the direct current based on the current running state of the alternating current-direct current system and the inherent characteristics of the alternating current-direct current power grid, provide clear available action quantity for emergency control measures of the system under the condition of large disturbance fault, ensure that the short-time maximum emergency support capability of the direct current is fully exerted on one hand, avoid the mismatch of emergency control instructions and the actual capability of the direct current on the other hand, reduce or eliminate the accident risk that the power lifting does not reach the standard or even the commutation failure occurs due to insufficient support of the alternating current voltage in the emergency power support process, and improve the transient stability of the power grid.
Drawings
FIG. 1 is a flow chart of the method of the present invention;
Detailed Description
The present invention is described in further detail below with reference to the attached drawings.
Example 1:
the basic principle of the embodiment is as follows: the method comprises the steps of determining real-time power lifting capacity based on a current operation mode of direct current, on one hand, avoiding that after the direct current power is lifted, the direct current near-zone section tide crosses a transmission power limit to damage safe and stable operation of an alternating current power grid, and on the other hand, avoiding the problems that in the direct current emergency power support process, due to the fact that the alternating current voltage of a converter station is too low, the direct current cannot be maintained to follow a current setting value output by a direct current power regulating device, the actual lifting power of the direct current cannot reach the standard, and even the phase change fails due to the fact that the voltage drops greatly. The method comprehensively considers the restriction of an alternating current system and the self running mode of direct current on the premise of considering the direct current overload capacity, and calculates the real-time maximum capacity of the direct current power based on a quasi-steady-state equation. For the constraint of the alternating current transmission section, on the basis of a known grid structure, the maximum power allowed to be improved by direct current can be estimated according to the power flow transfer ratio, the line stability limit and the real-time operation power of the section; for the restriction factors of direct current, analyzing the most commonly adopted constant current of a rectifier station and the real-time DC boost capability under the constant voltage control mode of an inverter station, gradually increasing the direct current by adopting a perturbation method, considering the influence of the increase of active power and reactive power of direct current transmission on alternating current voltage, and calculating the trigger angle of the rectifier at the moment. The specific implementation steps are shown in fig. 1.
Step 1 in fig. 1 illustrates the calculation of the maximum power that can be boosted, subject to the constraints of the dc capability itself.
Firstly, the maximum overload power P of direct current capable of safely operating for a short time (generally 2 hours) is obtainedmax.dcThen the maximum possible boosted power Δ P, constrained by the DC capability itselfmax.dcComprises the following steps:
ΔPmax.dc＝Pmax.dc-P0
wherein, P0The current direct current active power.
Step 2 in fig. 1 illustrates that the maximum possible dc boost power Δ P determined by the cross-sectional transmission capacity of the ac system is determined according to the current grid structure and operation modemax.acSpecifically, the following is made.
Let the AC section with coupling property with DC transmission power be end face j, and its stable limit of transmission power be PjmaxTherefore, subject to the stable operating limit of section j, the maximum allowed dc boost power is:
in the formula, Pj0The current operation trend of the section j is obtained; k is a radical ofjThe change value of the section j power flow when the direct current quantity of unit power is increased.
If there are n alternating current sections coupled with the direct current transmission power, the maximum allowable direct current boosted power is limited by the tidal current stable operation limit of the n coupling sections:
ΔPmax.ac＝min(ΔPmax.ac(1),ΔPmax.ac(j)…ΔPmax.ac(n))(j＝1,2……n)。
step 3 in fig. 1 illustrates the determination of the maximum power P that can be operated in real time from the current dc operating modemax.on. The maximum achievable boost power Δ P subject to the constraints of the dc operating modemax.onComprises the following steps:
ΔPmax.on＝Pmax.on-P0
the method for determining the maximum power capable of being operated in real time according to the current direct current operation mode specifically comprises the following steps:
3-1) monitoring the current DC average value I0Direct voltage U from pole to ground of rectifier stationd0Trigger angle α of rectifier0Let X be the commutation reactance of each phase of the rectifier stationr1The DC loop resistance is R, and the minimum firing angle for DC enabled operation is αmin(typically 5 °).
When α0＞αminWhen the step is carried out, the step is carried out to the step 3-2), otherwise, the step is directly carried out to the step 3-7)。
3-2) calculating to obtain the effective value U of the no-load line voltage at the valve side of the converter transformer0Comprises the following steps:
wherein N is1The number of 6 pulsating converters in each pole of the converter station.
DC power P of rectifier stationd0Comprises the following steps:
Pd0＝Ud0I0
reactive power Q consumed by a converter station0Comprises the following steps:
3-3) if the increase of the current is Δ I, the increased current I1Comprises the following steps:
I1＝I0+ΔI
calculating the DC voltage U after the current increased1And DC power Pd1Comprises the following steps:
Ud1＝Ud0+RΔI
Pd1＝Ud1I1
and 3-4) solving the effective value of the no-load line voltage at the valve side of the converter transformer after the current is increased according to the Jacobian matrix at the AC side and the reactive power change consumed by the current converter of the rectifier station under the current state, wherein the specific method is as follows.
From the perspective of the DC access point, the port characteristics of the AC system can be expressed as Jacobian matrix equation
P and Q are respectively active power and reactive power which are injected into the direct-current rectifying station by the alternating-current power grid; the phase angle difference between the alternating current equivalent potential of the equivalent alternating current single-port network and the alternating current voltage of the direct current access point; u is the amplitude of the AC voltage of the DC access point, and delta P, delta Q, delta and delta U respectively correspond to the variation of the active power injected into the DC rectifying station by the AC power grid, the variation of the reactive power injected into the DC rectifying station by the AC power grid, the variation of the phase angle difference between the AC equivalent potential and the AC voltage of the DC access point and the variation of the amplitude of the AC voltage of the DC access point.
Is a jacobian matrix, which is a matrix composed of the first partial derivatives of the corresponding functions, wherein,
at the moment, the effective value U of the valve-side no-load line voltage of the converter transformer1Comprises the following steps:
wherein,
3-5) calculating the firing angle α of the rectifier after the current increase1Comprises the following steps:
3-6) order I0＝I1，Ud0＝Ud1，α0＝α1If α0＞αminThen return to step 3-2). Otherwise, go to step 3-7).
3-7) the DC maximum operating power determined by the DC current operating mode is as follows:
Pmax.on＝Ud0I0
step 4 in fig. 1 describes a method for calculating the dc power real-time boost capability by integrating a plurality of limiting factors, which specifically includes:
ΔPmax＝min(ΔPmax.ac,ΔPmax.dc,ΔPmax.on)
step 5 in fig. 1 describes an online transient stability checking process, which specifically includes: based on the on-line real-time data, checking that the current DC power is increased to P ═ P0+ΔPmaxThe transient stability of the time alternating current system is judged, and if the transient stability margin is smaller than the lower operation limit allowed by the system, the delta P is mademax＝ΔPmax-P, re-checking when the dc power is boosted to P ═ P0+ΔPmaxThe transient stability of the time alternating current system, wherein P is a gradient value for gradually reducing the check power, and the smaller the value of P is, the more accurate the obtained direct current can improve the power in real time; otherwise, when Δ PmaxWhen the direct current power is more than 0, the direct current power real-time boost capability is delta Pmax(ii) a When Δ PmaxWhen the current is less than or equal to 0, the direct current does not have the real-time power increasing capability.
Although the present invention has been described in terms of the preferred embodiment, it is not intended that the invention be limited to the embodiment. Any equivalent changes or modifications made without departing from the spirit and scope of the present invention also belong to the protection scope of the present invention. The scope of the invention should therefore be determined with reference to the appended claims.

Claims (3)

1. A method for calculating real-time capacity-improving capability of direct current power is characterized by comprising the following steps:
1) obtaining the maximum overload power P of the direct current capable of safely operating in short timemax.dcObtaining the maximum liftable power delta P restricted by the direct current self-capabilitymax.dcComprises the following steps:
ΔPmax.dc＝Pmax.dc-P0
wherein, P0The current direct current active power;
2) according to the current operation network frame of the power gridStructure and operation mode, and determining maximum lifting power of DC (direct Current) determined by tidal current transmission capacity of section of AC system as delta Pmax.ac；
3) Determining the maximum power P capable of running in real time according to the current running mode of the direct currentmax.onObtaining the maximum liftable power delta P restricted by the DC operation modemax.onComprises the following steps:
ΔPmax.on＝Pmax.on-P0
4) the real-time DC power boost capability integrating multiple limiting factors is as follows:
ΔPmax＝min(ΔPmax.ac,ΔPmax.dc,ΔPmax.on)
5) based on the on-line real-time data, checking that the current DC power is increased to P ═ P0+ΔPmaxThe transient stability of the time alternating current system is judged, and if the transient stability margin is smaller than the lower operation limit allowed by the system, the delta P is mademax＝ΔPmaxChecking when the DC power is increased to P ═ P0+ΔPmaxThe transient stability of the time alternating current system, wherein P is a gradient value for gradually reducing the check power, and the smaller the value of P is, the more accurate the obtained direct current can improve the power in real time; otherwise, when Δ PmaxWhen the direct current power is more than 0, the direct current power real-time boost capability is delta Pmax(ii) a When Δ PmaxWhen the current is less than or equal to 0, the direct current does not have the real-time power increasing capability.
2. The method for calculating the real-time liftable capacity of the direct current power as claimed in claim 1, wherein the method for determining the maximum liftable power of the direct current power determined by the cross-sectional power flow transmission capacity of the alternating current system in the step 2) is as follows.
Let the AC section with coupling property with DC transmission power be end face j, and its stable limit of transmission power be PjmaxTherefore, the maximum allowable DC boost power is limited by the stable operating limit of section j
<mrow> <msub> <mi>&amp;Delta;P</mi> <mrow> <mi>m</mi> <mi>a</mi> <mi>x</mi> <mo>.</mo> <mi>a</mi> <mi>c</mi> </mrow> </msub> <mrow> <mo>(</mo> <mi>j</mi> <mo>)</mo> </mrow> <mo>=</mo> <mfrac> <mrow> <msub> <mi>P</mi> <mrow> <mi>j</mi> <mi>m</mi> <mi>a</mi> <mi>x</mi> </mrow> </msub> <mo>-</mo> <msub> <mi>P</mi> <mrow> <mi>j</mi> <mn>0</mn> </mrow> </msub> </mrow> <msub> <mi>k</mi> <mi>j</mi> </msub> </mfrac> </mrow>
In the formula, Pj0The current operation trend of the section j is obtained; k is a radical ofjThe change value of the section j tide is the change value when the direct current quantity of unit power is increased;
if there are n alternating current sections coupled with the direct current transmission power, the maximum allowable direct current boosted power is limited by the tidal current stable operation limit of the n coupling sections:
ΔPmax.ac＝min(ΔPmax.ac(1),ΔPmax.ac(j)…ΔPmax.ac(n))(j＝1,2……n)。
3. the method for calculating the real-time liftable capability of the direct current power according to claim 1, wherein the method for determining the real-time operable maximum power according to the current direct current operation mode in the step 3) specifically comprises the following steps:
3-1) monitoring the current DC average value I0Direct voltage U from pole to ground of rectifier stationd0Trigger angle α of rectifier0Let X be the commutation reactance of each phase of the rectifier stationr1The DC loop resistance is R, and the minimum firing angle for DC enabled operation is αmin；
When α0＞αminIf so, turning to the step 3-2), otherwise, directly turning to the step 3-7);
3-2) calculating to obtain the no-load line at the valve side of the converter transformerEffective value pressing U0Comprises the following steps:
<mrow> <msub> <mi>U</mi> <mn>0</mn> </msub> <mo>=</mo> <mfrac> <mn>1</mn> <mrow> <msqrt> <mn>2</mn> </msqrt> <msub> <mi>cos&amp;alpha;</mi> <mn>0</mn> </msub> </mrow> </mfrac> <mrow> <mo>(</mo> <mfrac> <mrow> <msub> <mi>&amp;pi;U</mi> <mrow> <mi>d</mi> <mn>0</mn> </mrow> </msub> </mrow> <mrow> <mn>3</mn> <msub> <mi>N</mi> <mn>1</mn> </msub> </mrow> </mfrac> <mo>+</mo> <msub> <mi>X</mi> <mrow> <mi>r</mi> <mn>1</mn> </mrow> </msub> <msub> <mi>I</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> </mrow>
wherein N is1The number of 6 pulsating converters in each pole of the converter station;
DC power of rectifier station is Pd0：
Pd0＝Ud0I0
Reactive power Q consumed by a converter station0Comprises the following steps:
<mrow> <msub> <mi>Q</mi> <mn>0</mn> </msub> <mo>=</mo> <msqrt> <mrow> <msup> <mrow> <mo>(</mo> <mfrac> <mrow> <mn>3</mn> <msqrt> <mn>2</mn> </msqrt> </mrow> <mi>&amp;pi;</mi> </mfrac> <msub> <mi>N</mi> <mn>1</mn> </msub> <msub> <mi>U</mi> <mn>0</mn> </msub> <msub> <mi>I</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>-</mo> <msubsup> <mi>P</mi> <mrow> <mi>d</mi> <mn>0</mn> </mrow> <mn>2</mn> </msubsup> </mrow> </msqrt> </mrow>
3-3) if the increase of the current is Δ I, the increased current I1Comprises the following steps:
I1＝I0+ΔI
calculating the DC voltage U after the current increased1And DC power Pd1Comprises the following steps:
Ud1＝Ud0+RΔI
Pd1＝Ud1I1
3-4) solving the effective value of the no-load line voltage at the valve side of the converter transformer after the current is increased according to the Jacobian matrix at the AC side and the reactive power change consumed by the current converter of the rectifier station under the current state, wherein the specific method comprises the following steps:
from the point of view of the DC access point, the port characteristic of the AC system is expressed by a Jacobian matrix equation
<mrow> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>P</mi> </mtd> </mtr> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>Q</mi> </mtd> </mtr> </mtable> </mfenced> <mo>=</mo> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <msub> <mi>J</mi> <mrow> <mi>p</mi> <mi>&amp;delta;</mi> </mrow> </msub> </mtd> <mtd> <msub> <mi>J</mi> <mrow> <mi>p</mi> <mi>v</mi> </mrow> </msub> </mtd> </mtr> <mtr> <mtd> <msub> <mi>J</mi> <mrow> <mi>q</mi> <mi>&amp;delta;</mi> </mrow> </msub> </mtd> <mtd> <msub> <mi>J</mi> <mrow> <mi>q</mi> <mi>v</mi> </mrow> </msub> </mtd> </mtr> </mtable> </mfenced> <mfenced open = "[" close = "]"> <mtable> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>&amp;delta;</mi> </mtd> </mtr> <mtr> <mtd> <mi>&amp;Delta;</mi> <mi>U</mi> </mtd> </mtr> </mtable> </mfenced> </mrow>
P and Q are respectively active power and reactive power which are injected into the direct-current rectifying station by the alternating-current power grid; the phase angle difference between the alternating current equivalent potential of the equivalent alternating current single-port network and the alternating current voltage of the direct current access point; u is the amplitude of the alternating voltage of the direct current access point, and delta P, delta Q, delta and delta U respectively correspond to the variation of active power injected into the direct current rectifier station by the alternating current power grid, the variation of reactive power injected into the direct current rectifier station by the alternating current power grid, the variation of the phase angle difference between the alternating current equivalent potential and the alternating voltage of the direct current access point and the variation of the amplitude of the alternating current voltage of the direct current access point;
is a jacobian matrix, which is a matrix composed of the first partial derivatives of the corresponding functions, wherein,
at the moment, the effective value U of the valve-side no-load line voltage of the converter transformer1Comprises the following steps:
<mrow> <msub> <mi>U</mi> <mn>1</mn> </msub> <mo>=</mo> <msub> <mi>U</mi> <mn>0</mn> </msub> <mo>+</mo> <mfrac> <mrow> <mi>m</mi> <mo>&amp;lsqb;</mo> <mi>k</mi> <mi>m</mi> <mrow> <mo>(</mo> <mi>w</mi> <mo>+</mo> <msub> <mi>mQ</mi> <mn>0</mn> </msub> <mo>-</mo> <msub> <mi>U</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mo>+</mo> <msqrt> <mrow> <msub> <mi>kmQ</mi> <mn>0</mn> </msub> <mrow> <mo>(</mo> <mn>2</mn> <mi>w</mi> <mo>-</mo> <mn>2</mn> <msub> <mi>U</mi> <mn>0</mn> </msub> <mo>+</mo> <msub> <mi>mQ</mi> <mn>0</mn> </msub> <mo>)</mo> </mrow> <mo>+</mo> <mi>k</mi> <msup> <mrow> <mo>(</mo> <msub> <mi>U</mi> <mn>0</mn> </msub> <mo>-</mo> <mi>w</mi> <mo>)</mo> </mrow> <mn>2</mn> </msup> <mo>+</mo> <mrow> <mo>(</mo> <msup> <mi>km</mi> <mn>2</mn> </msup> <mo>-</mo> <mn>1</mn> <mo>)</mo> </mrow> <msubsup> <mi>P</mi> <mrow> <mi>d</mi> <mn>1</mn> </mrow> <mn>2</mn> </msubsup> </mrow> </msqrt> <mo>&amp;rsqb;</mo> </mrow> <mrow> <msup> <mi>km</mi> <mn>2</mn> </msup> <mo>-</mo> <mn>1</mn> </mrow> </mfrac> <mo>-</mo> <msub> <mi>mQ</mi> <mn>0</mn> </msub> <mo>-</mo> <mi>w</mi> </mrow>
wherein,
3-5) calculating the firing angle α of the rectifier after the current increase1Comprises the following steps:
<mrow> <msub> <mi>&amp;alpha;</mi> <mn>1</mn> </msub> <mo>=</mo> <mi>arccos</mi> <mrow> <mo>(</mo> <mfrac> <mrow> <msub> <mi>&amp;pi;U</mi> <mrow> <mi>d</mi> <mn>1</mn> </mrow> </msub> <mo>+</mo> <mn>3</mn> <msub> <mi>N</mi> <mn>1</mn> </msub> <msub> <mi>X</mi> <mrow> <mi>r</mi> <mn>1</mn> </mrow> </msub> <msub> <mi>I</mi> <mn>1</mn> </msub> </mrow> <mrow> <mn>3</mn> <msqrt> <mn>2</mn> </msqrt> <msub> <mi>N</mi> <mn>1</mn> </msub> <msub> <mi>U</mi> <mn>1</mn> </msub> </mrow> </mfrac> <mo>)</mo> </mrow> </mrow>
3-6) order I0＝I1，Ud0＝Ud1，α0＝α1If α0＞αminAnd returning to the step 3-2); otherwise, turning to the step 3-7);
3-7) the maximum DC operating power determined by the current DC operating mode is Δ Pmax.onComprises the following steps:
Pmax.on＝Ud0I0。
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