CN108616137B - Direct current protection parameter optimization method for realizing coordination recovery of alternating current and direct current systems - Google Patents

Direct current protection parameter optimization method for realizing coordination recovery of alternating current and direct current systems Download PDF

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CN108616137B
CN108616137B CN201810437060.8A CN201810437060A CN108616137B CN 108616137 B CN108616137 B CN 108616137B CN 201810437060 A CN201810437060 A CN 201810437060A CN 108616137 B CN108616137 B CN 108616137B
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direct current
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alternating current
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王玉
侯玉强
刘福锁
薛峰
李威
李兆伟
吴雪莲
朱玲
赵学茂
罗峰
张倩
顾晓玲
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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
    • 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
    • H02J5/00—Circuit arrangements for transfer of electric power between ac networks and dc 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
    • H02J2003/365—Reducing harmonics or oscillations in HVDC
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Abstract

The invention discloses a direct current protection parameter optimization method for realizing coordination and recovery of an alternating current-direct current system, and belongs to the technical field of power systems and automation thereof. The method of the invention comprises the following steps: and calculating the effective short-circuit ratio of the direct current inversion side converter station in the current operation mode, calculating the dynamic recovery capability index of the alternating current-direct current system under the fault in real time according to the effective short-circuit ratio of the direct current and the bus voltage of the inversion side converter station in the transient process, and dynamically calculating the key parameters of the direct current commutation failure prediction control and the low-voltage current limiting link according to the index. The method fully considers the influence of the strength and fault impact of the alternating current system on the alternating current and direct current recovery capability, sets the direct current protection parameter adjustment amplitude limit, and improves the coordination recovery capability of the alternating current and direct current systems under the condition of ensuring the stability of the direct current self-control system.

Description

Direct current protection parameter optimization method for realizing coordination recovery of alternating current and direct current systems
Technical Field
The invention relates to a direct current protection parameter optimization method for realizing coordination and recovery of an alternating current-direct current system, and belongs to the technical field of power automation.
Background
With the gradual operation of high-capacity ultrahigh voltage direct current, the characteristics of strong direct current and weak alternating current of a power grid are increasingly prominent, and the alternating current and direct current coupling effect is increasingly compact. At present, a plurality of power grids such as China east power grid, China power grid, Guangdong power grid and the like form a typical direct current feed-in system. Problems such as direct current commutation failure and the like become important factors for restricting the safe and stable operation of the extra-high voltage alternating current and direct current power grid.
The direct current commutation fails and large reactive power exchange exists with an alternating current system in the recovery process. When an alternating current system is weak or fault impact is large, if direct current is recovered too fast, a large amount of reactive power can be absorbed from the alternating current system, so that the voltage recovery of the alternating current system is slow, even the voltage of a receiving end is unstable, and the alternating current and direct current systems cannot be recovered; however, if the dc recovery speed is too slow, a large power impact may be caused to the ac system, which may cause a risk of power angle and frequency safety of the ac system. Therefore, in the ac/dc interconnection system, it is necessary to control the dc recovery speed and improve the ac/dc system coordination recovery capability.
Disclosure of Invention
The invention aims to overcome the defects in the prior art, provides a direct current protection parameter optimization method for realizing the coordination recovery of an alternating current and direct current system, and solves the technical problem that the coordination recovery capability of the alternating current and direct current system is poor due to the fact that the direct current recovery speed is difficult to control after direct current commutation failure in the prior art.
In order to solve the technical problems, the technical scheme adopted by the invention is as follows: a direct current protection parameter optimization method for realizing coordination recovery of an alternating current-direct current system comprises the following steps:
calculating the effective short-circuit ratio of the direct current inversion side converter station in the current operation mode;
calculating the dynamic recovery capability index of the AC/DC system under the fault in real time according to the effective short circuit ratio and the bus voltage of the inverter side converter station in the transient process;
and dynamically adjusting parameters of the direct current commutation failure prediction control and the low-voltage current limiting link according to the dynamic recovery capability index.
Further, an effective short circuit ratio is calculated according to formula (1):
Figure BDA0001654925570000021
wherein, MESCRiFor the effective short-circuit ratio, S, of the converter station on the direct current i inversion sideaciFor short-circuit capacity, Q, of converter station on the inverting side of direct current iciCompensating the capacity for a filter on the direct current i inversion side; pdiAnd outputting power for the inversion side of the direct current i.
Further, a dynamic recovery capability index is calculated according to formula (2):
RFi＝MESCRi*UFi (2)
in the formula, RFiThe direct current i and the bus voltage coordination recovery capability index of the inversion side converter station are obtained; u shapeFiThe real-time bus voltage of the direct current i inversion side converter station under the fault condition is obtained.
Further, the method for dynamically adjusting the direct current commutation failure prediction control parameter comprises the following steps:
critical standard R for determining dynamic recovery capability strength of alternating current and direct current systemFlim；
Optimizing the phase change failure predictive control starting voltage value according to a formula (3):
Figure BDA0001654925570000022
in the formula of Ucfp1For predicting control starting voltage calculation value for phase change failure without considering amplitude limit, RFiThe direct current i and the bus voltage coordination recovery capability index of the inversion side converter station are obtained; u shapecfprCalculating a reference value for a starting voltage of a commutation failure prediction control link;
considering the amplitude limiting requirement, the phase-commutation failure prediction control starting voltage is valued according to a formula (4):
Ucfp＝min[Ucfp1,0.85] (4)。
further, the method for dynamically adjusting the parameters of the low-voltage current limiting link comprises the following steps:
critical standard R for determining dynamic recovery capability strength of alternating current and direct current systemFlim；
The start-up voltage and the cut-off voltage are optimized according to the formulas (5) and (6):
Figure BDA0001654925570000031
Figure BDA0001654925570000032
in the formula: u shapedh1Calculating a starting voltage value of a low-voltage current limiting link when amplitude limiting is not considered; u shapedl1Calculating a cutoff voltage value of a low-voltage current-limiting link when amplitude limiting is not considered; u shapedhrCalculating a reference value for a low-voltage current-limiting link starting voltage; u shapedlrCalculating a reference value for the cut-off voltage of the low-voltage current-limiting link; rFiThe direct current i and the bus voltage coordination recovery capability index of the inversion side converter station are obtained;
taking into account the clipping requirement, Udh、UdlTaking values according to formulas (7) and (8) respectively:
Figure BDA0001654925570000033
Figure BDA0001654925570000034
in the formula: u shapedhIs a starting voltage; u shapedlIs the cut-off voltage.
Further, the critical standard R of the dynamic recovery capability of the AC/DC systemFlimCalculated according to the formula (3):
RFlim＝MESCRlim*Ucr (9)
wherein, MESCRiThe effective short circuit ratio of the direct current i inversion side converter station is obtained;ucr is the AC system transient voltage stability threshold.
Compared with the prior art, the invention has the following beneficial effects:
the influence of the strength and fault impact of an alternating current system on the alternating current and direct current recovery capability is fully considered, the direct current protection parameter is set to adjust amplitude limiting, the coordination recovery capability of the alternating current and direct current system is improved under the condition that the direct current self control system is stable, and technical support is provided for the safe and stable operation control of the extra-high voltage alternating current and direct current power grid.
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FIG. 1 is a flow chart of the method of the present invention.
Detailed Description
Commutation failure prediction control and low-voltage current-limiting control are two links closely related to direct-current commutation failure in direct-current protection, and have great influence on direct-current recovery speed and reactive power exchange of an alternating-current and direct-current system. The invention provides a direct current protection parameter optimization method for realizing the coordination recovery of an alternating current and direct current system, which fully considers the influence of the intensity and fault impact of the alternating current system on the alternating current and direct current recovery capability, sets the adjustment and amplitude limit of the direct current protection parameter, and improves the coordination recovery capability of the alternating current and direct current system under the condition of ensuring the stability of a direct current self-control system.
The invention is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
As shown in fig. 1, the present invention provides a dc protection parameter optimization method for realizing ac/dc system coordination recovery, which includes the following steps:
the method comprises the following steps: according to the formula (1), calculating the effective short-circuit ratio of the direct current i inversion side converter station under the current operation mode:
Figure BDA0001654925570000041
wherein, MESCRiFor the effective short-circuit ratio, S, of the converter station on the direct current i inversion sideaciFor short-circuit capacity, Q, of converter station on the inverting side of direct current iciTo the direct current i inversion sideA filter compensation capacity; pdiAnd outputting power for the inversion side of the direct current i.
Step two: calculating the dynamic recovery capability index of the AC/DC system under the fault according to the formula (2):
RFi＝MESCRi*UFi (2)
in the formula, RFiThe direct current i and the bus voltage coordination recovery capability index of the inversion side converter station are obtained; u shapeFiThe real-time bus voltage of the direct current i inversion side converter station under the fault condition is obtained.
Step three: dynamically calculating parameters of direct current commutation failure prediction control and low-voltage current limiting link:
3-1) determining the dynamic recovery capability strength standard of an AC/DC system:
according to engineering experience, when the effective short-circuit ratio is larger than the critical value MESCRlim(generally takes a value of 3.0 in engineering), the system can be considered as a strong system; meanwhile, according to the transient voltage stability criterion of the safety and stability calculation technical specification of the power system, in the dynamic process of the power system after disturbance, the voltage of the load bus is recovered to be above 0.8 per unit of value within 10s, and Ucr can be valued according to 0.8. Therefore, the critical standard R of the dynamic recovery capability of the AC/DC systemFlimCan be calculated according to equation (3):
RFlim＝3.0*0.8＝2.4 (3)
3-2) determining a commutation failure prediction control parameter adjustment method:
according to the principle of predicting the action of a control link in commutation failure, starting a voltage value U of the linkcfpIs one of the key parameters affecting the ac/dc recovery characteristics. Therefore, the commutation failure predictive control starting voltage value is optimized according to the formula (4):
Figure BDA0001654925570000051
in the formula of Ucfp1Predictive control of the starting voltage calculation for commutation failure, UcfprAnd starting a voltage reference value for a commutation failure prediction control link. According to engineering experience, the starting voltage of the link is generally between 0.75p.u. and 0.85p.u., namely the AC busWhen the line voltage falls to 0.75p.u. -0.85 p.u., the link is started, then U is startedcfprThe value of 0.85p.u.
According to engineering experience, the higher the starting voltage of a commutation failure prediction control link is, the more reactive power needs to be absorbed from an alternating current system in the direct current recovery process, the recovery of the alternating current system is not facilitated, and generally, the recommended value is not more than 0.85 p.u.. Therefore, the commutation failure prediction control starting voltage value can be taken according to the formula (5):
Ucfp＝min[Ucfp1,0.85] (5)
3-3) determining the adjusting method of the low-pressure flow-limiting ring section parameters:
according to the action principle of a low-voltage current-limiting link, the link starts a voltage UdhAnd cutoff voltage UdlIs an important parameter affecting the dc recovery process. Therefore, the start-up voltage and the cut-off voltage are optimized according to equations (6) and (7):
Figure BDA0001654925570000052
Figure BDA0001654925570000061
according to the low-voltage current-limiting control principle, Udh>Udl(ii) a Meanwhile, according to engineering experience, the starting voltage is generally not higher than 0.85p.u., the cut-off voltage is generally not lower than 0.1p.u., and a certain margin is considered for Udh、UdlPerform clipping, Udh、UdlThe following values can be taken:
Figure BDA0001654925570000062
Figure BDA0001654925570000063
in the formula: u shapedh1Calculating a starting voltage value of a low-voltage current limiting link when amplitude limiting is not considered;Udl1calculating a cutoff voltage value of a low-voltage current-limiting link when amplitude limiting is not considered; u shapedhrCalculating a reference value for a low-voltage current-limiting link starting voltage; u shapedlrCalculating a reference value for the cut-off voltage of the low-voltage current-limiting link; u shapedhStarting voltage for a low-voltage current-limiting link; u shapedlThe low-voltage current-limiting link is cut off voltage.
In summary, the present invention is a dc protection parameter optimization method for realizing coordination and recovery of ac/dc systems. The influence of the strength and fault impact of an alternating current system on the alternating current and direct current recovery capability is fully considered, the direct current protection parameter is set to adjust amplitude limiting, the coordination recovery capability of the alternating current and direct current system is improved under the condition that the direct current self control system is stable, and technical support is provided for the safe and stable operation control of the extra-high voltage alternating current and direct current power grid.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.

Claims (4)

1. A direct current protection parameter optimization method for realizing the coordination recovery of an alternating current and direct current system is characterized by comprising the following steps:
calculating the effective short-circuit ratio of the direct current inversion side converter station in the current operation mode;
calculating the dynamic recovery capability index of the AC/DC system under the fault in real time according to the effective short circuit ratio and the bus voltage of the inverter side converter station in the transient process;
dynamically adjusting parameters of direct current commutation failure prediction control and low-voltage current limiting links according to the dynamic recovery capacity index;
the method for dynamically adjusting the parameters of the low-voltage current limiting link comprises the following steps:
critical standard R for determining dynamic recovery capability strength of alternating current and direct current systemFlim；
The start-up voltage and the cut-off voltage are optimized according to the formulas (5) and (6):
Figure FDA0003068097030000011
Figure FDA0003068097030000012
in the formula: u shapedh1Calculating a starting voltage value of a low-voltage current limiting link when amplitude limiting is not considered; u shapedl1Calculating a cutoff voltage value of a low-voltage current-limiting link when amplitude limiting is not considered; u shapedhrCalculating a reference value for a low-voltage current-limiting link starting voltage; u shapedlrCalculating a reference value for the cut-off voltage of the low-voltage current-limiting link; rFiThe direct current i and the bus voltage coordination recovery capability index of the inversion side converter station are obtained;
considering the amplitude limiting requirement, the starting voltage and the cut-off voltage of the low-voltage current limiting link are respectively valued according to formulas (7) and (8):
Figure FDA0003068097030000013
Figure FDA0003068097030000021
in the formula: u shapedhStarting voltage for a low-voltage current-limiting link; u shapedlThe voltage is cut off for the low-voltage current-limiting link;
critical standard R for dynamic recovery capability of AC/DC systemFlimCalculated according to the formula (9):
RFlim＝MESCRlim*Ucr (9)
wherein, MESCRlimIs an effective short circuit ratio threshold value; ucr is the AC system transient voltage stability threshold.
2. The method for optimizing direct current protection parameters to achieve coordinated recovery of an alternating current/direct current system according to claim 1, wherein the effective short-circuit ratio is calculated according to formula (1):
Figure FDA0003068097030000022
wherein, MESCRiFor the effective short-circuit ratio, S, of the converter station on the direct current i inversion sideaciFor short-circuit capacity, Q, of converter station on the inverting side of direct current iciCompensating the capacity for a filter on the direct current i inversion side; pdiAnd outputting power for the inversion side of the direct current i.
3. The method for optimizing direct current protection parameters to achieve coordinated recovery of an alternating current/direct current system according to claim 2, wherein the dynamic recovery capability index is calculated according to formula (2):
RFi＝MESCRi*UFi (2)
in the formula, RFiThe direct current i and the bus voltage coordination recovery capability index of the inversion side converter station are obtained; u shapeFiThe real-time bus voltage of the direct current i inversion side converter station under the fault condition is obtained.
4. The method for optimizing the direct current protection parameters for realizing the coordination and recovery of the alternating current and direct current system according to claim 1, wherein the method for dynamically adjusting the direct current commutation failure prediction control parameters comprises the following steps:
critical standard R for determining dynamic recovery capability strength of alternating current and direct current systemFlim；
Optimizing the phase change failure predictive control starting voltage value according to a formula (3):
Figure FDA0003068097030000023
in the formula of Ucfp1For predicting control starting voltage calculation value for phase change failure without considering amplitude limit, RFiThe direct current i and the bus voltage coordination recovery capability index of the inversion side converter station are obtained; u shapecfprCalculating a reference value for a starting voltage of a commutation failure prediction control link;
according to engineering experience, the phase commutation failure prediction control starting voltage is valued according to a formula (4):
Ucfp＝min[Ucfp1,0.85] (4)。
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