CN107482637B - Method and system for determining difference direct current short circuit ratio of active equipment - Google Patents
Method and system for determining difference direct current short circuit ratio of active equipment Download PDFInfo
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- H—ELECTRICITY
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- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
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Abstract
The invention relates to a method and a system for determining a differential direct current short-circuit ratio of active equipment, wherein the total three-phase short-circuit current of a direct current conversion bus of a generator is calculated according to a power grid model for calculating the short-circuit current; calculating short-circuit current provided by dynamic reactive active equipment, wherein the reactive active equipment comprises dynamic reactive power source active equipment and dynamic reactive load active equipment; accumulating the influence of the short-circuit current of the reactive power source active equipment from the total three-phase short-circuit current, and eliminating the influence of the short-circuit current of the dynamic reactive load active equipment from the total three-phase short-circuit current; and traversing all the direct current conversion buses, and calculating a direct current short-circuit ratio index. The method solves the problem that the traditional direct current short circuit ratio for evaluating the voltage supporting capability of the alternating current power grid is invalid by considering the dynamic characteristic difference of the active equipment, namely the difference of the quality of the reactive power attribute and the difference of the quantity of the reactive power.
Description
Technical Field
The invention relates to the field of power systems, in particular to a method and a system for determining a differential direct-current short-circuit ratio of active equipment.
Background
The direct current short-circuit ratio is a quantitative index for evaluating the dynamic voltage supporting capability of a direct current feed-in alternating current power grid defined on the basis of static electric parameters of the power grid such as short-circuit current and the like. On the basis, the domestic scholars research and propose new improvement indexes such as direct current external characteristic short circuit ratio, reactive effective short circuit ratio and generalized short circuit ratio. At the beginning of the index definition, except for a conventional generator, short-circuit current provided by other active equipment in a power grid can be ignored, so that the types of the active equipment are single and the characteristics are the same. Based on the knowledge that the larger the short-circuit current supplied by the generator is, the more the dynamic reactive capacity of the power grid is, the better the corresponding voltage recovery characteristic is, the larger the short-circuit ratio value is, the better the corresponding dynamic voltage supporting capability of the power grid is. Under the condition that active equipment presents diversified development, the difference of dynamic reactive characteristics of different equipment can obviously influence the effectiveness of short-circuit ratio evaluation dynamic voltage supporting capability.
Therefore, the conventional short-circuit ratio evaluation failure problem, namely, the problem that the voltage supporting capability is rather weaker as the short-circuit ratio is larger, contrary to the existing evaluation logic.
Disclosure of Invention
In order to solve the defects in the prior art, the invention aims to provide a method and a system for determining the differential direct current short-circuit ratio of active equipment.
The purpose of the invention is realized by adopting the following technical scheme:
the invention provides a method for determining a differential direct current short circuit ratio of active equipment, which is improved by the following steps:
calculating total three-phase short-circuit current of a direct current conversion bus of the generator according to a power grid model for calculating the short-circuit current;
calculating short-circuit current provided by dynamic reactive active equipment, wherein the reactive active equipment comprises dynamic reactive power source active equipment and dynamic reactive load active equipment;
accumulating the influence of the short-circuit current of the reactive power source active equipment from the total three-phase short-circuit current, and eliminating the influence of the short-circuit current of the dynamic reactive load active equipment from the total three-phase short-circuit current;
and traversing all the direct current conversion buses, and calculating a direct current short-circuit ratio index.
Further: the power grid model for calculating the short-circuit current is specifically established according to static models of lines and transformer power transmission and transformation elements, dynamic models of generators and motor elements, and generated power, load power and key section exchange power operation data of each region.
Further: the calculating of the three-phase short-circuit current of the direct current conversion bus provided by the generator comprises the following steps:
aiming at a multi-direct-current feed-in system with Nd total number of direct-current conversion buses, calculating influence factors of the multi-direct-current feed-in system;
calculating three-phase short-circuit current I of the direct current conversion bus I according to the influence factors "Fi；
The influence factors of the multi-DC feed-in system are as follows:
wherein: tp is a multi-DC feeding systemInfluence factors of the system; i. j represents a direct current conversion bus, and j is not equal to i; ziiThe self-impedance corresponding to the direct current conversion bus i in the equivalent impedance matrix; zijThe mutual impedance between the direct current conversion bus i and the direct current conversion bus j is obtained; pdjIs direct current power.
Further: calculating the short circuit current provided by the dynamic reactive active device comprises:
setting corresponding weight coefficients and related intermediate variables according to the dynamic reactive power source active equipment and the dynamic reactive load active equipment;
and calculating the short-circuit current of the dynamic reactive power supply type active equipment and the short-circuit current of the dynamic reactive load type active equipment in sequence.
Further: setting weight coefficients and related intermediate variables of the influence of the active equipment, including:
setting dynamic reactive power class EsActive equipment E of different types and dynamic reactive load class ELThe weight coefficients and intermediate variables of different active devices f;
for dynamic reactive power class EsIn different types of active equipment e, a weight coefficient alpha is set for calculating the influence degree of the active equipment on the short-circuit ratioe；
Class E for dynamic reactive loadsLThe weight coefficient beta of different active devices f is set and the influence degree of the active devices f on the short-circuit ratio is calculatedf；
Initializing an intermediate variable TP、TLAnd TSValues are all zero, TLAnd TSRespectively, intermediate variables, T, for dynamic reactive load-type active equipment and dynamic reactive power supply-type active equipmentPAre intermediate variables for accumulation.
Further: calculating the short-circuit current of the dynamic reactive power supply type active equipment according to the formula:
wherein: e'igAnd ZigRespectively of conventional generators gEquivalent internal potential and transfer impedance between the equivalent internal potential and a direct current conversion bus i; g represents the number of conventional generators;
the short-circuit current provided by the reactive power supply type active equipment is accumulated, and the influence is as the following formula:
wherein: i'SeFor dynamic reactive power supply class EsIn the short-circuit current, alpha, supplied by different types of active devices eeiFor dynamic reactive power supply class EsWeighting coefficients of the short-circuit ratio influence degree of direct-current conversion buses i of different types of active equipment e, wherein Ts is short-circuit current provided by reactive power supply type active equipment and accumulates the influence;
the short-circuit current of the dynamic reactive load type active equipment is calculated in sequence according to the formula:
in the formula, ZWw、ZPpRespectively the transfer impedance between equivalent internal potential and fault point of the w-th wind power and the p-th photovoltaic equipment; w and P are the total number of elements contained in the wind power and photovoltaic equipment respectively; e ″)WwAnd E ″)PpEquivalent internal potentials of a w-th wind power and a p-th photovoltaic device are respectively set, w represents the w-th wind power, and p represents the p-th photovoltaic;
the short-circuit current provided by the dynamic reactive load type active equipment eliminates the influence of the short-circuit current, and the formula is as follows:
wherein: i ″)LfFor dynamic reactive loads of the type ELShort-circuit current, beta, of different active devices ffiFor dynamic reactive loads of the type ELWeight coefficient of short-circuit ratio influence degree of direct current conversion bus i of different active equipment f in the process, TLIs dynamic withoutThe short-circuit current provided by the active device of the work load class cancels the influence of the short-circuit current.
Further: traversing all the direct current conversion buses, and calculating a direct current short-circuit ratio index, wherein the method comprises the following steps:
traversing all the direct current conversion buses;
calculating a direct current short-circuit ratio index according to the total three-phase short-circuit current of the direct current conversion bus and the short-circuit current of the dynamic active equipment;
the direct current short circuit ratio index is expressed as:
wherein: MISCRCQQiThe short-circuit ratio index of the direct current conversion bus i with active equipment difference is UN, the UN is rated voltage of the conversion bus, i is i +1, and all the direct current conversion buses are traversed in sequence until i>Nd。
The invention provides a determination system for taking difference direct current short circuit ratio of active equipment into account, and the improvement is that the system comprises:
the first calculation module is used for calculating the total three-phase short-circuit current of the direct current conversion bus of the generator according to the power grid model for calculating the short-circuit current;
the second calculation module is used for calculating short-circuit current provided by dynamic reactive power active equipment, and the reactive power active equipment comprises dynamic reactive power supply active equipment and dynamic reactive load active equipment; accumulating the influence of the short-circuit current of the reactive power source active equipment from the total three-phase short-circuit current, and eliminating the influence of the short-circuit current of the dynamic reactive load active equipment from the total three-phase short-circuit current;
and the third calculation module is used for traversing all the direct current conversion buses and calculating the direct current short-circuit ratio index.
Further, the first computing module further includes:
the first calculating unit is used for calculating influence factors of the multi-direct-current feed-in system aiming at the multi-direct-current feed-in system with the total number of the direct-current conversion buses being Nd;
a second calculating unit for calculating three-phase short-circuit current I of the DC conversion bus I according to the influence factor "Fi；
The reactive active equipment comprises: the second computing module further includes:
the setting unit is used for setting corresponding weight coefficients and related intermediate variables according to the dynamic reactive power source type active equipment and the dynamic reactive load type active equipment;
the third calculating unit is used for calculating the short-circuit current of the dynamic reactive power supply type active equipment and accumulating the influence of the short-circuit current in the total three-phase current;
and the fourth calculation unit is used for calculating the short-circuit current of the dynamic reactive power supply type active equipment and the short-circuit current of the dynamic reactive load type active equipment in sequence and eliminating the influence of the short-circuit currents from the total three phases.
Further, the setting unit further includes:
a first setting unit for setting dynamic reactive power type EsActive equipment E of different types and dynamic reactive load class ELThe weight coefficients and intermediate variables of different active devices f;
a second setting unit for a second class E for dynamic reactive power supplysIn different types of active equipment e, a weight coefficient alpha is set for calculating the influence degree of the active equipment on the short-circuit ratioe；
A third setting unit for setting a dynamic reactive load class ELThe weight coefficient beta of different active devices f is set and the influence degree of the active devices f on the short-circuit ratio is calculatedf；
An initialization unit for initializing intermediate variables, the intermediate variables comprising TP、TLAnd TSAll values of which are zero, TLAnd TSRespectively, intermediate variables, T, for dynamic reactive load-type active equipment and dynamic reactive power supply-type active equipmentPIs an intermediate variable for accumulation.
Further, the third computing module further comprises:
the traversing unit is used for traversing all the direct current conversion buses;
and the fifth calculating unit is used for calculating a direct current short-circuit ratio index according to the total three-phase short-circuit current of the direct current conversion bus and the short-circuit current of the dynamic active equipment.
Compared with the closest prior art, the technical scheme provided by the invention has the beneficial effects that:
the invention provides a direct current short-circuit ratio index for calculating difference of active equipment, which solves the problem that the traditional direct current short-circuit ratio estimation alternating current power grid voltage supporting capability is invalid by calculating the dynamic characteristic difference of the active equipment, namely the difference of reactive property quality and the difference of reactive magnitude quantity.
Drawings
FIG. 1 is a diagram of a DC short-circuit ratio MISCR that accounts for differences in active devices provided by the present inventionCQQCalculating a flow chart;
FIG. 2 is a schematic diagram of the variation of multiple DC short-circuit ratios under different duty ratios of the induction motor provided by the present invention;
fig. 3 is a schematic diagram of the recovery characteristic of large disturbance of the commutation bus voltage under different load ratios of the induction motor provided by the invention;
FIG. 4 is a block diagram of a system for determining a DC short circuit ratio in consideration of differences between active devices according to the present invention;
fig. 5 is a flowchart of a method for determining a dc-short ratio in consideration of differences between active devices according to the present invention.
Detailed Description
The following describes embodiments of the present invention in further detail with reference to the accompanying drawings.
The following description and the drawings sufficiently illustrate specific embodiments of the invention to enable those skilled in the art to practice them. Other embodiments may incorporate structural, logical, electrical, process, and other changes. The examples merely typify possible variations. Individual components and functions are optional unless explicitly required, and the sequence of operations may vary. Portions and features of some embodiments may be included in or substituted for those of others. The scope of embodiments of the invention encompasses the full ambit of the claims, as well as all available equivalents of the claims. Embodiments of the invention may be referred to herein, individually or collectively, by the term "invention" merely for convenience and without intending to voluntarily limit the scope of this application to any single invention or inventive concept if more than one is in fact disclosed.
The first embodiment,
To achieve the above object, the present invention provides a method for determining a differential dc-to-short ratio of active devices, a flowchart of which is shown in fig. 5, and the method of the present invention is described in detail with reference to fig. 1 as follows:
1) establishing a power grid model for short-circuit current calculation, comprising: the system comprises a static model of power transmission and transformation elements such as lines and transformers, a dynamic model of elements such as generators and motors, and operation data such as generated power, load power and critical section exchange power of each region.
2) Initializing weight coefficients and related intermediate variables considering the influence of active equipment, comprising the following steps: aiming at active equipment e of different types (such as different types of wind power generation, photovoltaic power generation and the like) in a dynamic reactive power supply class, a weight coefficient alpha for calculating the influence degree of the weight coefficient on a short-circuit ratio is sete(ii) a Setting a weight coefficient beta for calculating the influence degree of the dynamic reactive load on the short-circuit ratio according to different active devices f in the dynamic reactive load classf(ii) a Initializing an intermediate variable TP、TLAnd TSThe values are set to zero, respectively.
3) And calculating the three-phase short-circuit current of the direct current conversion bus provided by the generator.
Total number of direct current oriented is NdThe multi-direct-current feed-in system utilizes the formula (1) to accumulate and calculate the influence factor T of other direct currents j (j ≠ i) on the direct current aiming at the direct current i in sequenceP. In the formula, Zii、ZijRespectively corresponding self-impedance of the direct current i commutation bus in the equivalent impedance matrix and mutual impedance between the direct current i commutation bus and the direct current j commutation bus; pdIs a dc power.
Calculating three-phase short-circuit current I of DC converter bus I only considering conventional generator action by using power system short-circuit current calculation software, such as PSD-SCCPC "Fi. Wherein: the above formula represents a cyclic accumulation formula of Tp plus Zij/Zii×PdjThen, assigning Tp, and traversing all Z by circulating all the timeij/Zii×PdjAccumulation summation is realized, i and j both represent direct current conversion buses, and j is not equal to i; zii、ZijRespectively corresponding self-impedance of the direct current i commutation bus in the equivalent impedance matrix and mutual impedance between the direct current i commutation bus and the direct current j commutation bus; pdjIs a dc power.
Calculating a short circuit current provided by the dynamic reactive active device and adding/removing effects from the total three-phase short circuit current, comprising:
4) calculating the short-circuit current provided by the active equipment of dynamic reactive power supply type and accumulating the influence on the short-circuit currentsSequentially calculating short-circuit current I provided by each dynamic reactive power supply type active equipment e "SeAnd the influence is accumulated by using the formula (2),
calculating the short-circuit current of the dynamic reactive power supply type active equipment according to the formula:
wherein: e'igAnd ZigRespectively equal internal potential of a conventional generator g and transfer impedance between the equal internal potential and a direct current conversion bus i; g represents the number of conventional generators;
calculating the short-circuit current of the dynamic reactive load type active equipment according to the formula:
in the formula, ZWw、ZPpRespectively the transfer impedance between equivalent internal potential and fault point of the w-th wind power and the p-th photovoltaic equipment; w and P are the total number of elements contained in the wind power and photovoltaic equipment respectively; e ″)WwAnd E ″)PpThe equivalent internal potential of the w-th wind power and the p-th photovoltaic equipment are respectively, w represents the w-th wind power, and p represents the p-th photovoltaic.
The following formula represents the cumulative summation calculation:
in the formula, I "SeFor dynamic reactive power supply class EsOf different types of active devices eeiFor dynamic reactive power supply class EsAnd (2) weighting coefficients of short-circuit ratio influence degrees of direct-current converting buses i of different types of active equipment e, wherein Ts is short-circuit current provided by reactive power supply active equipment, and influence of the short-circuit current of the reactive power supply active equipment is accumulated from total three-phase short-circuit current.
5) Calculating short-circuit current provided by active equipment of dynamic reactive load class and eliminating influence on ELDifferent types of dynamic reactive load active equipment (such as induction motor) are adopted, and the short-circuit current I provided by each type of dynamic reactive power supply active equipment f is calculated in sequence "LfAnd the influence is eliminated by using a formula (3), wherein the elimination accumulated subtraction calculation is represented by the following formula:
wherein: i ″)LfFor dynamic reactive loads of the type ELShort-circuit current, beta, of different active devices ffiFor dynamic reactive loads of the type ELWeight coefficient of short-circuit ratio influence degree of direct current conversion bus i of different active equipment f in the process, TLIs dynamic withoutAnd the short-circuit current provided by the active equipment of the power load type eliminates the influence of the short-circuit current of the active equipment of the dynamic reactive load type from the total three-phase short-circuit current.
6) Calculating a DC short-circuit ratio index taking into account the difference of the active devices, and calculating a short-circuit ratio index MISCR of DC i taking into account the difference of the active devices by using a formula (4)CQQi，
Wherein: MISCRCQQiThe short-circuit ratio index of the direct current conversion bus i with active equipment difference is UN, the UN is rated voltage of the conversion bus, i is i +1, and all the direct current conversion buses are traversed in sequence until i>Nd。
Example II,
1) Establishing a power grid model for short-circuit current calculation:
taking the multi-direct-current feed-in receiving-end power grid corresponding to a certain planning scheme as an example, collecting data for short-circuit current calculation, including primary equipment electrical parameters such as lines and transformers, power output of a generator and load power consumption, and dynamic parameters such as transient reactance of the generator and an induction motor, and establishing a short-circuit current calculation power grid model.
2) And initializing weight coefficients and related intermediate variables considering the influence of the active equipment:
setting a weight coefficient beta for an induction motor in a dynamic reactive load class, the weight coefficient beta taking into account the influence degree of the induction motor on a short-circuit ratiof1.0; initializing an intermediate variable TP＝TL＝TS＝0。
3) Calculating three-phase short-circuit current of a direct current conversion bus provided by a generator:
aiming at the 2-loop extra-high voltage direct current feed-in system in Henan, aiming at direct currents in Hexi and Hezhong, accumulating and calculating the influence factor T of other direct currents j (j is not equal to i) on the direct currentP. In the formula, Zii、ZijRespectively corresponding self-impedance of the direct current i commutation bus in the equivalent impedance matrix and mutual impedance between the direct current i commutation bus and the direct current j commutation bus；PdIs direct current power.
The three-phase short-circuit current I "F of the yuxi dc and yuxi dc converter bus is calculated with the power system short-circuit current calculation software, such as PSD-SCCPC, taking into account only the normal generator action (i.e., setting the induction motor load ratio as a quantity).
4) Calculating short-circuit current provided by dynamic reactive power supply type active equipment and accumulating the influence of the short-circuit current:
because of the fact that in the Henan multi-direct current feed-in system, no active equipment such as a dynamic reactive power supply is arranged except a conventional generator, namely I in the formula (2) "SeThis step can be omitted because it is 0.
5) Calculating short-circuit current provided by the active equipment of the dynamic reactive load class and eliminating the influence of the short-circuit current:
aiming at the load of an induction motor, which is a dynamic reactive load active device in a multi-DC feed-in system in Henan, short-circuit current I provided by f is calculated "LfAnd the influence thereof is eliminated by using formula (3).
6) Calculating a direct current short circuit ratio index considering active equipment difference:
calculating the difference of active devices by using formula (4), and calculating the short circuit ratio index MISCR of Yuxi direct current and Yuzhong direct current respectivelyCQQi. In the formula of UNIs the rated voltage of the commutation bus.
MISCRCQQiIs provided withD, the short-circuit ratio index i of the direct current conversion buses of the source equipment difference, UN is rated voltage of the conversion buses, i is i +1, and all the direct current conversion buses are traversed in sequence until i>Nd。
Conventional short circuit ratio MISCR under different induction motor duty ratio conditions, short circuit ratio MISCR accounting for active device differential effectsCQQAnd the voltage recovery characteristics of the multi-dc-fed system under large disturbance are shown in fig. 2 and fig. 3, respectively. As can be seen from the figure, under the condition of the induction motor being switched in, the traditional short-circuit ratio MISCR evaluation dynamic voltage supporting capability is failed, that is, the index is increased, and the voltage supporting capability is judged to be enhanced, which is contrary to the grid voltage recovery characteristic shown by the simulation result. MISCR taking into account weakened voltage support capability of induction motorCQQThe weakening trend of the power grid strength or the voltage supporting capability judged by monotonous reduction of the numerical value is consistent with the deterioration situation of the voltage recovery characteristic of the power grid. The new index solves the failure problem of the traditional short circuit ratio evaluation dynamic voltage supporting capability.
Example III,
Based on the same inventive concept, the present invention further provides a system for determining a differential dc-to-short ratio of active devices, wherein a schematic diagram of the system is shown in fig. 4, and the system comprises:
a building module 301, configured to build a power grid model for calculating a short-circuit current;
the first calculating module 302 is configured to calculate a total three-phase short-circuit current of the generator dc converter bus according to the power grid model;
a second calculation module 303, configured to calculate a short-circuit current provided by the dynamic reactive active device and add/remove an influence from the total three-phase short-circuit current; the reactive active equipment comprises dynamic reactive power supply active equipment and dynamic reactive load active equipment;
calculating the influence of the short-circuit current of the dynamic reactive power supply active equipment accumulated from the total three-phase short-circuit current, and the short-circuit current of the dynamic reactive load active equipment and eliminating the influence from the total three-phase short-circuit current;
and a third calculating module 304, configured to traverse all the dc converter buses and calculate a dc short-circuit ratio indicator.
Further, the first calculating module 302 further includes:
the first calculating unit is used for calculating influence factors of the multi-direct-current feed-in system aiming at the multi-direct-current feed-in system with the total number of the direct-current conversion buses being Nd;
a second calculating unit for calculating three-phase short-circuit current I of the DC conversion bus I according to the influence factor "Fi；
In the present invention, the reactive active devices are classified into dynamic reactive power source active devices and dynamic reactive load active devices, and the second calculation module 303 further includes:
the setting unit is used for setting corresponding weight coefficients and related intermediate variables according to the dynamic reactive power source type active equipment and the dynamic reactive load type active equipment;
the third calculating unit is used for calculating the short-circuit current of the dynamic reactive power supply type active equipment and accumulating the influence of the short-circuit current on the total three-phase current;
and the fourth calculation unit is used for calculating the short-circuit current of the dynamic reactive load type active equipment and eliminating the influence of the short-circuit current from the total three-phase short-circuit current.
Further, the setting unit further includes:
a first setting unit for setting dynamic reactive power type EsActive equipment E of different types and dynamic reactive load class ELThe weight coefficients and intermediate variables of different active devices f;
a second setting unit for a second class E for dynamic reactive powersIn different types of active equipment e, a weight coefficient alpha is set for calculating the influence degree of the active equipment on the short-circuit ratioe；
A third setting unit for setting a dynamic reactive load class ELThe weight coefficient beta of different active devices f is set and the influence degree of the active devices f on the short-circuit ratio is calculatedf；
An initialization unit for initializing intermediate variables, the intermediate variables comprising TP、TLAnd TSWhich isValues are all zero, TLAnd TSRespectively, intermediate variables, T, for dynamic reactive load-type active equipment and dynamic reactive power supply-type active equipmentPAre intermediate variables for accumulation.
Further, the third computing module further includes:
the traversing unit is used for traversing all the direct current converting buses;
and the fifth calculating unit is used for calculating a direct current short-circuit ratio index according to the total three-phase short-circuit current of the direct current conversion bus and the short-circuit current of the dynamic active equipment.
Under the condition of diversified development of active equipment, the traditional direct current short-circuit ratio is difficult to adapt to the new requirements of power grid dynamic voltage supporting capability evaluation. The invention provides a direct current short-circuit ratio index for calculating difference of active equipment, and solves the problem that the traditional direct current short-circuit ratio estimation alternating current power grid voltage supporting capability is invalid by calculating the difference of dynamic characteristics of the active equipment, namely the difference of reactive property quality and the difference of reactive magnitude quantity.
Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art can make modifications and equivalents to the embodiments of the present invention without departing from the spirit and scope of the present invention, which is set forth in the claims of the present application.
Claims (11)
1. A method for determining a differential DC-to-short ratio of active devices is characterized in that:
calculating total three-phase short-circuit current of a direct current conversion bus of the generator according to a power grid model for calculating the short-circuit current;
calculating short-circuit current provided by dynamic reactive active equipment, wherein the reactive active equipment comprises dynamic reactive power source active equipment and dynamic reactive load active equipment; accumulating the influence of the short-circuit current of the reactive power source active equipment from the total three-phase short-circuit current, and eliminating the influence of the short-circuit current of the dynamic reactive active equipment from the total three-phase short-circuit current;
traversing all the direct current conversion buses, and calculating a direct current short-circuit ratio index;
calculating the three-phase short-circuit current of the direct current conversion bus i according to the formula:
wherein: e'igAnd ZigRespectively equal internal potential of a conventional generator g and transfer impedance between the equal internal potential and a direct current conversion bus i; g represents the number of conventional generators;
the short-circuit current provided by the reactive power supply type active equipment is accumulated, and the influence is as the following formula:
wherein: i'SeFor dynamic reactive power supply class EsOf different types of active devices eeiFor dynamic reactive power supply class EsWeighting coefficients of the short-circuit ratio influence degree of direct-current conversion buses i of different types of active equipment e, wherein Ts is short-circuit current provided by reactive power supply type active equipment and accumulates the influence;
calculating the short-circuit current of the dynamic reactive load type active equipment in sequence according to the formula:
in the formula, ZWw、ZPpRespectively the transfer impedance between equivalent internal potential and fault point of the w-th wind power and the p-th photovoltaic equipment; w and P are the total number of elements contained in the wind power and photovoltaic equipment respectively; e ″)WwAnd E ″)PpEquivalent internal potentials of a w-th wind power and a p-th photovoltaic device are respectively set, w represents the w-th wind power, and p represents the p-th photovoltaic;
the short-circuit current provided by the dynamic reactive load type active equipment eliminates the influence of the short-circuit current, and the formula is as follows:
wherein: i ″)LfFor dynamic reactive loads of the type ELShort-circuit current, beta, of different active devices ffiFor dynamic reactive loads of the type ELWeight coefficient of short-circuit ratio influence degree of direct current conversion bus i of different active equipment f in the process, TLShort-circuit current is provided for the active equipment of dynamic reactive load type and the influence of the short-circuit current is eliminated.
2. The determination method according to claim 1, characterized in that: the power grid model for calculating the short-circuit current is specifically established according to static models of lines and transformer power transmission and transformation elements, dynamic models of generators and motor elements, and generated power, load power and key section exchange power operation data of each region.
3. The determination method according to claim 2, characterized in that: the calculating of the three-phase short-circuit current of the direct current conversion bus provided by the generator comprises the following steps:
aiming at a multi-direct-current feed-in system with Nd total number of direct-current conversion buses, calculating influence factors of the multi-direct-current feed-in system;
calculating three-phase short-circuit current I of the direct current conversion bus I according to the influence factors "Fi；
The influence factors of the multi-DC feed-in system are as follows:
wherein: tp is an influence factor of the multi-DC feed-in system; i. j represents a direct current conversion bus, and j is not equal to i; ziiThe self-impedance corresponding to the direct current conversion bus i in the equivalent impedance matrix; z is a linear or branched memberijThe impedance is the mutual impedance between the direct current commutation bus i and the direct current commutation bus j.
4. The determination method according to claim 1, characterized in that: calculating the short-circuit current provided by the active equipment of the dynamic reactive load type comprises the following steps:
setting corresponding weight coefficients and related intermediate variables according to the dynamic reactive power source type active equipment and the dynamic reactive load type active equipment;
and calculating the short-circuit current of the dynamic reactive power supply type active equipment and the short-circuit current of the dynamic reactive load type active equipment in sequence.
5. The determination method according to claim 4, characterized in that: setting weight coefficients and related intermediate variables of the influence of the active equipment, including:
setting dynamic reactive power class EsActive equipment E of different types and dynamic reactive load class ELThe weight coefficients and intermediate variables of different active devices f;
for dynamic reactive power class EsIn different types of active equipment e, a weight coefficient alpha is set for calculating the influence degree of the active equipment on the short-circuit ratioe；
Class E for dynamic reactive loadsLThe weight coefficient beta of different active devices f is set and the influence degree of the active devices f on the short-circuit ratio is calculatedf；
Initializing an intermediate variable TP、TLAnd TSValues are all zero, TLAnd TSRespectively, intermediate variables, T, for dynamic reactive load-type active equipment and dynamic reactive power supply-type active equipmentPIs an intermediate variable for accumulation.
6. The determination method according to any one of claims 1 to 4, characterized in that: traversing all the direct current conversion buses, and calculating a direct current short-circuit ratio index, wherein the method comprises the following steps:
traversing all the direct current conversion buses;
calculating a direct current short-circuit ratio index according to the total three-phase short-circuit current of the direct current conversion bus and the short-circuit current of the dynamic active equipment;
the direct current short circuit ratio index is expressed as:
wherein: MISCRCQQiIs a short-circuit ratio index, U, of a direct current conversion bus i of active equipment differenceNSequentially traversing all the direct current conversion buses until i is up to i +1 for the rated voltage of the conversion bus>Nd；TPIs an intermediate variable for accumulation.
7. A determination system for use in any of claims 1-5 and a method of determining a differential dc-to-short ratio for an active device, the system comprising:
the first calculation module is used for calculating the total three-phase short-circuit current of the direct current conversion bus of the generator according to the power grid model for calculating the short-circuit current;
the second calculation module is used for calculating short-circuit current provided by dynamic reactive active equipment, and the reactive active equipment comprises dynamic reactive power source active equipment and dynamic reactive load active equipment; accumulating the influence of the short-circuit current of the reactive power source active equipment from the total three-phase short-circuit current, and eliminating the influence of the short-circuit current of the dynamic reactive load active equipment from the total three-phase short-circuit current;
and the third calculation module is used for traversing all the direct current conversion buses and calculating the direct current short-circuit ratio index.
8. The determination system of claim 7, wherein the first calculation module further comprises:
the first calculating unit is used for calculating influence factors of the multi-direct-current feed-in system aiming at the multi-direct-current feed-in system with the total number of the direct-current conversion buses being Nd;
a second calculation unit for calculating based onCalculating three-phase short-circuit current I of direct current conversion bus I by using the influence factors "Fi。
9. The determination system of claim 8, wherein the reactive active device is divided into: the second computing module further includes:
the setting unit is used for setting corresponding weight coefficients and related intermediate variables according to the dynamic reactive power source type active equipment and the dynamic reactive load type active equipment;
the third calculating unit is used for calculating the short-circuit current of the dynamic reactive power supply type active equipment and accumulating the influence of the short-circuit current on the total three-phase current;
and the fourth calculation unit is used for calculating the short-circuit current of the dynamic reactive load type active equipment and eliminating the influence of the short-circuit current from the total three-phase short-circuit current.
10. The determination system according to claim 9, wherein the setting unit further includes:
a first setting unit for setting dynamic reactive power type EsActive equipment E of different types and dynamic reactive load class ELThe weight coefficients and intermediate variables of different active devices f;
a second setting unit for a second class E for dynamic reactive power supplysIn different types of active equipment e, a weight coefficient alpha is set for calculating the influence degree of the active equipment on the short-circuit ratioe；
A third setting unit for setting a dynamic reactive load class ELThe weight coefficient beta of different active devices f is set and the influence degree of the active devices f on the short-circuit ratio is calculatedf；
An initialization unit for initializing intermediate variables, the intermediate variables comprising TP、TLAnd TSAll values of which are zero, TLAnd TSRespectively, intermediate variables, T, for dynamic reactive load-type active equipment and dynamic reactive power supply-type active equipmentPAs intermediate variables for accumulation。
11. The determination system of claim 7, wherein the third calculation module further comprises:
the traversing unit is used for traversing all the direct current conversion buses;
and the fifth calculating unit is used for calculating a direct current short-circuit ratio index according to the total three-phase short-circuit current of the direct current conversion bus and the short-circuit current of the dynamic active equipment.
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