CN113471928A - Photovoltaic equipment cluster equivalence calculation method in power distribution network current protection setting process - Google Patents
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Abstract
The invention discloses a photovoltaic equipment cluster equivalence calculation method in a power distribution network current protection setting process, which comprises the following steps of: acquiring power distribution network line parameters and the total access capacity of photovoltaic equipment; obtaining branch photovoltaic equipment according to the power distribution network line parameters and the total access capacity; calculating the photovoltaic equipment of the trunk line through a lever-like photovoltaic cluster equivalent algorithm to obtain head-end photovoltaic equipment and tail-end photovoltaic equipment; respectively calculating short-circuit current values of the branch photovoltaic equipment, the head-end photovoltaic equipment and the tail-end photovoltaic equipment at the protective installation positions according to the transient characteristics of the photovoltaic equipment; and setting the photovoltaic equipment in the power distribution network current protection setting process according to the short-circuit current values of the branch photovoltaic equipment, the head end photovoltaic equipment and the tail end photovoltaic equipment at the protection installation position. According to the method provided by the embodiment of the invention, the current protection setting calculation of the power distribution network with a plurality of photovoltaic devices connected can be simplified, and the safety and stability of the power distribution network are effectively protected.
Description
Technical Field
The invention relates to the technical field of power systems, in particular to a photovoltaic equipment cluster equivalence calculation method in a power distribution network current protection setting process.
Background
Distributed energy refers to the generation of electric energy by a plurality of even various types of power generation equipment together in a certain geographical range so as to meet the requirement of large-scale electricity utilization on site. Photovoltaic is a distributed energy, and has characteristics such as clean environmental protection, two-way power supply, consumption on the spot. In recent years, as the permeability of photovoltaic equipment in a power distribution network system is continuously improved, when the system fails, the short-circuit current provided by a photovoltaic power supply is continuously increased, which inevitably affects the reliability and sensitivity of the original protection.
In the related technology, most relay protection of a 10kV power distribution network is configured to an overcurrent I section and an overcurrent III section, and the setting values of the overcurrent I section and the overcurrent III section are set according to the power supply load condition before photovoltaic access; after the photovoltaic distributed energy is connected, the correct action of the existing relay protection is inevitably influenced, for example, the protection false operation without a directional element caused by the photovoltaic reverse current, the protection cannot reach the required protection range, and the like. With the improvement of the access capacity of the photovoltaic equipment, the influence is continuously increased, so that the current protection of the power distribution network with the photovoltaic equipment access is imperatively reset to ensure the reliable operation of the power system.
However, as a distributed energy source, the photovoltaic power generation is distributed in the distribution network, and the capacity scales of the photovoltaic power generation are different, so that the complexity of the distribution network current protection setting calculation process is improved. Therefore, the cluster equivalence of the dispersed photovoltaic equipment is beneficial to simplifying the current protection setting calculation of the power distribution network with photovoltaic access, the current protection setting efficiency is improved, and the method has positive effects on the configuration and the setting value of the relay protection of the power distribution network.
Disclosure of Invention
The present invention is directed to solving, at least to some extent, one of the technical problems in the related art described above.
Therefore, one purpose of the invention is to provide a photovoltaic equipment cluster equivalence calculation method in the distribution network current protection setting process, which can simplify the distribution network current protection setting calculation containing multiple photovoltaic equipment accesses, and the error meets the protection setting requirement, so that the configuration and the fixed value of the distribution network relay protection can be guided, and the safety and the stability of the distribution network can be protected.
The invention also aims to provide a photovoltaic equipment cluster equivalent calculating device in the power distribution network current protection setting process.
In order to achieve the purpose, the invention discloses a photovoltaic equipment cluster equivalent calculation method in the power distribution network current protection setting process on one hand, which comprises the following steps: acquiring power distribution network line parameters and the total access capacity of photovoltaic equipment; obtaining the branch photovoltaic equipment according to the power distribution network line parameters and the total access capacity; calculating the trunk line photovoltaic equipment through a lever-like photovoltaic cluster equivalent algorithm to obtain head-end photovoltaic equipment and tail-end photovoltaic equipment; respectively calculating short-circuit current values of the branch photovoltaic equipment, the head-end photovoltaic equipment and the tail-end photovoltaic equipment at a protective installation position according to the transient characteristics of the photovoltaic equipment; and setting the photovoltaic equipment in the power distribution network current protection setting process according to the short-circuit current values of the branch photovoltaic equipment, the head end photovoltaic equipment and the tail end photovoltaic equipment at the protection installation position.
In addition, the photovoltaic equipment cluster equivalent calculation method in the distribution network current protection setting process according to the embodiment of the invention can also have the following additional technical characteristics:
according to an embodiment of the present invention, the acquiring power distribution network line parameters and total access capacity of photovoltaic equipment includes: acquiring a topological structure of the power distribution network and short-circuit impedance, line topology and impedance of the power distribution network; acquiring a node number of the photovoltaic equipment and an access photovoltaic capacity corresponding to the node number; and obtaining the total access capacity of the photovoltaic equipment according to the topological structure of the power distribution network, the node number of the photovoltaic equipment and the access photovoltaic capacity corresponding to the node number.
According to one embodiment of the invention, the capacity of the head-end photovoltaic installation and the capacity S' of the tail-end photovoltaic installation are calculated according to the following formulas:
calculating the capacity S "of the tail-end photovoltaic device according to the following formula:
wherein z is the unit impedance of the power distribution network line, knl is the length of n sections of lines, and n is a positive integer.
According to an embodiment of the present invention, the calculating the short circuit current values of the branch photovoltaic device, the head-end photovoltaic device and the tail-end photovoltaic device at the protection installation according to the transient characteristics of the photovoltaic devices respectively includes: according to the transient characteristics of the photovoltaic equipment, the photovoltaic equipment is equivalent to a current source; and obtaining the current value of the current source according to the control characteristic of the photovoltaic equipment and the voltage at the grid-connected position of the photovoltaic equipment.
According to one embodiment of the invention, the transient behavior of the photovoltaic device is obtained by the following formula:
wherein, IPVShort-circuit current output for photovoltaic installations, IratedIs the rated current of the photovoltaic device, PratedFor rated power of photovoltaic plants, UpccFor the named value of the grid-connected point voltage,
and p.u is a unit of per unit value of the voltage of the grid-connected point.
According to the photovoltaic equipment cluster equivalence calculation method in the distribution network current protection setting process, the problem caused by the fact that the distribution network current protection setting is conducted through scattered photovoltaic access is solved, the distribution network current protection setting calculation with multiple photovoltaic equipment access can be simplified, and errors meet the protection setting requirements, so that the configuration and the setting of relay protection of the distribution network can be guided, and the safety and the stability of the distribution network are protected.
The invention also discloses a photovoltaic equipment cluster equivalence calculating device in the distribution network current protection setting process, which comprises the following steps: the first acquisition module is used for acquiring power distribution network line parameters and the total access capacity of the photovoltaic equipment; the second acquisition module is used for acquiring the branch photovoltaic equipment according to the power distribution network line parameters and the total access capacity; the first calculation module is used for calculating the trunk line photovoltaic equipment through a lever-like photovoltaic cluster equivalent algorithm to obtain head-end photovoltaic equipment and tail-end photovoltaic equipment; the second calculation module is used for respectively calculating short-circuit current values of the branch photovoltaic equipment, the head-end photovoltaic equipment and the tail-end photovoltaic equipment at a protection installation position according to the transient characteristics of the photovoltaic equipment; and the setting module is used for setting the photovoltaic equipment in the power distribution network current protection setting process according to the short-circuit current values of the branch photovoltaic equipment, the head end photovoltaic equipment and the tail end photovoltaic equipment at the protection installation position.
According to an embodiment of the present invention, the first obtaining module is specifically configured to: acquiring a topological structure of the power distribution network and short-circuit impedance, line topology and impedance of the power distribution network; acquiring a node number of the photovoltaic equipment and an access photovoltaic capacity corresponding to the node number; and obtaining the total access capacity of the photovoltaic equipment according to the topological structure of the power distribution network, the node number of the photovoltaic equipment and the access photovoltaic capacity corresponding to the node number.
According to one embodiment of the invention, the capacity of the head-end photovoltaic installation and the capacity S' of the tail-end photovoltaic installation are calculated according to the following formulas:
calculating the capacity S "of the tail-end photovoltaic device according to the following formula:
wherein z is the unit impedance of the power distribution network line, knl is the length of n sections of lines, and n is a positive integer.
According to an embodiment of the present invention, the second calculating module is specifically configured to: according to the transient characteristics of the photovoltaic equipment, the photovoltaic equipment is equivalent to a current source; and obtaining the current value of the current source according to the control characteristic of the photovoltaic equipment and the voltage at the grid-connected position of the photovoltaic equipment.
According to one embodiment of the invention, the transient behavior of the photovoltaic device is obtained by the following formula:
wherein, IPVShort-circuit current output for photovoltaic installations, IratedIs the rated current of the photovoltaic device, PratedFor rated power of photovoltaic plants, UpccFor the named value of the grid-connected point voltage,
and p.u is a unit of per unit value of the voltage of the grid-connected point.
According to the photovoltaic equipment cluster equivalence calculating device in the distribution network current protection setting process, the problem caused by the fact that the distribution network current protection setting is conducted through scattered photovoltaic access is solved, the distribution network current protection setting calculation with multiple photovoltaic equipment access can be simplified, and errors meet the protection setting requirements, so that the configuration and the setting of relay protection of the distribution network can be guided, and the safety and the stability of the distribution network are protected.
Additional aspects and advantages of the invention will be set forth in part in the description which follows and, in part, will be obvious from the description, or may be learned by practice of the invention.
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The above and/or additional aspects and advantages of the present invention will become apparent and readily appreciated from the following description of the embodiments, taken in conjunction with the accompanying drawings of which:
fig. 1 is a flowchart of a photovoltaic equipment cluster equivalence calculation method in a power distribution network current protection setting process according to an embodiment of the present invention;
FIG. 2 is a topology diagram of a distribution grid including decentralized photovoltaic access, according to one embodiment of the present invention;
fig. 3 is a schematic view of the access situation of the photovoltaic devices of the distribution network lines before and after the cluster equivalence according to the embodiment of the invention;
FIG. 4 is a graph of photovoltaic device short circuit current versus grid-connected point voltage according to one embodiment of the present invention;
fig. 5 is a block schematic diagram of a photovoltaic equipment cluster equivalence calculating device in a power distribution network current protection setting process according to an embodiment of the invention.
Detailed Description
Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to the same or similar elements or elements having the same or similar function throughout. The embodiments described below with reference to the accompanying drawings are illustrative only for the purpose of explaining the present invention, and are not to be construed as limiting the present invention.
The photovoltaic equipment cluster equivalent calculation method in the power distribution network current protection setting process according to the embodiment of the invention is described below with reference to the accompanying drawings.
Fig. 1 is a flowchart of a photovoltaic device cluster equivalence calculation method in a power distribution network current protection setting process according to an embodiment of the present invention. As shown in fig. 1, the photovoltaic device cluster equivalence calculation method in the distribution network current protection setting process includes:
and S1, acquiring the power distribution network line parameters and the total access capacity of the photovoltaic equipment.
According to one embodiment of the invention, acquiring the power distribution network line parameters and the total access capacity of the photovoltaic equipment comprises the following steps: acquiring a topological structure of a power distribution network and short-circuit impedance, line topology and impedance of the power distribution network; acquiring a node number of the photovoltaic equipment and an access photovoltaic capacity corresponding to the node number; and obtaining the total access capacity of the photovoltaic equipment according to the topological structure of the power distribution network, the node number of the photovoltaic equipment and the access photovoltaic capacity corresponding to the node number.
Specifically, the embodiment of the invention can obtain the parameters of the power distribution network and the access capacity and position of the photovoltaic equipment, including the topological structure of the power distribution network, the system short circuit impedance of the connected power distribution network system, the line topology and impedance, the node number of the photovoltaic equipment and the access photovoltaic capacity corresponding to the node number.
As shown in fig. 2, fig. 2 is a topological structure of a certain distribution network, and table 1 shows node numbers of photovoltaic devices and access photovoltaic capacities corresponding to the node numbers.
TABLE 1
And S2, obtaining branch photovoltaic equipment according to the power distribution network line parameters and the total access capacity.
Specifically, the embodiment of the invention can perform simple capacity conversion on photovoltaic equipment outside the protection downstream main line. The distribution of the branch photovoltaic equipment has almost no influence on the short-circuit current at the head end protection position of the main line when the line fails, so that the branch photovoltaic equipment is simply clustered, that is, the photovoltaic equipment on the branch is equivalent to one photovoltaic equipment according to the total capacity.
As shown in fig. 2, a simple capacity conversion is performed on the photovoltaic devices outside the protection downstream main trunk line, and the protection installation is the head ends of the 01 line, the 02 line and the 03 line in fig. 2, that is, the photovoltaic devices on the 01 line, the 02 line and the 03 line branch are equivalent to one photovoltaic device according to the total capacity.
And S3, calculating the trunk line photovoltaic equipment through a lever-like photovoltaic cluster equivalent algorithm to obtain head-end photovoltaic equipment and tail-end photovoltaic equipment.
According to one embodiment of the invention, the capacity of the head-end photovoltaic installation and the capacity S' of the tail-end photovoltaic installation are calculated according to the following formulas:
the capacity S "of the trailing photovoltaic device is calculated according to the following formula:
wherein z is the unit impedance of the power distribution network line, knl is the length of n sections of lines, and n is a positive integer.
Specifically, a lever-like photovoltaic cluster equivalent algorithm is utilized to convert photovoltaic equipment on a main line at the downstream into two photovoltaic equipment connected to the head end and the tail end of the line. Taking line 01 shown in fig. 2 as an example, the capacities of the photovoltaic devices at the first end and the last end are respectively 0.41S and 0.59S after lever-like photovoltaic equivalence calculation, and other lines can be subjected to equivalence calculation similarly. Schematic diagrams of access situations of photovoltaic devices before and after the cluster are shown in fig. 3a and 3 b.
For example, the embodiment of the invention can convert the photovoltaic equipment on the protection downstream trunk line into two photovoltaic equipment connected to the head end and the tail end of the line by using a lever-like photovoltaic cluster equivalent algorithm.
The lever-like equivalence principle is similar to the lever principle in mechanics, and photovoltaic equipment capacity and line impedance are analogized into force and force arms respectively. And then, obtaining that the dispersed photovoltaic equipment is equivalent to the head end and the tail end of the protection downstream line through weighting calculation.
As shown in fig. 3, assuming that the photovoltaic devices on one line are connected at the position shown in fig. 3a, all the photovoltaic devices on the line can be equivalently connected to one photovoltaic device at the head end and the tail end of the line shown in fig. 3b through the cluster equivalence calculation. As shown in fig. 3a and 3b, the actually connected photovoltaic devices PV1, PV2, PV3 and PV4 in the line can be equivalent to the photovoltaic devices PV ' and PV ' connected in the first and last two sections of the line, and the capacity of the photovoltaic devices PV ' and PV "can be equivalent by calculating with the photovoltaic devices PV1, PV2, PV3 and PV 4.
Assuming that the unit impedance of the line is z, the length of each line is represented as knl (n is 1,2,3 …), where the total photovoltaic access amount of the line is S, the head end capacity of the clustered photovoltaic equipment is S', and the tail end capacity is S ″, the calculation can be performed according to the equations (1) and (2):
without loss of generality, as the photovoltaic access position is set to be random, Sn is set to be S/4(n is 1, 2)And 3,4), namely, the condition of the photovoltaic equipment access can be equivalently represented. In the above formula, k1+k2+k3+k4+k5Therefore, when the equivalent photovoltaic device capacities at random positions are equal (in special cases), the equivalent photovoltaic device capacity can be calculated as S ═ k (k)2+2k3+3k4+4k5×S/4，S″＝S-S′。
And S4, respectively calculating the short-circuit current values of the branch photovoltaic equipment, the head-end photovoltaic equipment and the tail-end photovoltaic equipment at the protective installation position according to the transient characteristics of the photovoltaic equipment.
And calculating the short-circuit current value of the equivalent photovoltaic equipment at the protective installation position by using the transient characteristic of the photovoltaic equipment. LVRT (low voltage ride through) control of the photovoltaic equipment ensures that the equipment is not disconnected during a certain time during the grid fault, and the limitation on the low voltage ride through capability of the photovoltaic power station is mainly the limitation of the alternating current output by the inverter. The low-voltage ride-through control of the photovoltaic equipment during the fault period is divided into an active power generation control strategy and a reactive power generation control strategy, and the two strategies are both based on a constant current control strategy.
The capacity of the inverter switching tube is a main factor limiting the output current of the photovoltaic device. Usually the maximum current output by the inverter does not exceed 1.2 times the rated current. Namely, the method comprises the following steps:
this is essentially a limitation of the photovoltaic device output power because:
therefore, when the short-circuit current at the protection installation position of the power distribution network is calculated, the short-circuit current can be equivalent to a current source according to the transient characteristic (low voltage ride through characteristic) of the photovoltaic equipment, and the magnitude of the output current of the current source is related to the control characteristic of the photovoltaic equipment and the voltage at the grid connection position of the photovoltaic equipment.
According to one embodiment of the invention, the short-circuit current values of the branch photovoltaic device, the head-end photovoltaic device and the tail-end photovoltaic device at the protective installation are respectively calculated according to the transient characteristics of the photovoltaic devices, and the method comprises the following steps: equating the photovoltaic device as a current source according to transient characteristics of the photovoltaic device; and obtaining the current value of the current source according to the control characteristic of the photovoltaic equipment and the voltage at the grid-connected position of the photovoltaic equipment.
According to one embodiment of the invention, the transient behavior of the photovoltaic device is obtained by the following formula:
wherein, IPVShort-circuit current output for photovoltaic installations, IratedIs the rated current of the photovoltaic device, PratedFor rated power of photovoltaic plants, UpccFor the named value of the grid-connected point voltage,
and p.u is a unit of per unit value of the voltage of the grid-connected point.
Specifically, the short-circuit current value of the photovoltaic equipment at the protection installation position after equivalence can be calculated by using the transient characteristics of the photovoltaic equipment. The transient characteristics of the photovoltaic devices in this distribution network are as follows:
the relationship between the short-circuit current of the photovoltaic device and the voltage of the grid-connected point corresponding to the above formula is shown in fig. 4, and it can be known from fig. 4 that the photovoltaic device can be equivalent to a current source when the cluster equivalence is performed. In the embodiment, the voltage of the grid-connected point is between 0.2p.u. and 0.83p.u. when the node is in short circuit, so that the node can be equivalent to a current source with the current being 1.2 times of the rated current.
Simulation calculation is carried out on DIgSILENT software, faults are set at each node to carry out short-circuit current calculation, representative points are selected to calculate short-circuit currents at 01 wire, 02 wire and 03 wire protection positions, the short-circuit currents are shown in table 2 and can be obtained from table 2, short-circuit current errors calculated before and after clustering are small (< 5%), and current protection setting calculation requirements are met.
TABLE 2
And S5, setting the photovoltaic equipment in the power distribution network current protection setting process according to the short-circuit current values of the branch photovoltaic equipment, the head end photovoltaic equipment and the tail end photovoltaic equipment at the protection installation position.
That is to say, the embodiment of the invention sets the protection by using the short-circuit current value of the photovoltaic equipment at the protection installation position after equivalence. The relay protection is configured and set according to the short-circuit current in the fault, and the step is related to the type and the requirement of the current protection of a specific power distribution network and is not described in detail here.
According to the photovoltaic equipment cluster equivalence calculation method in the distribution network current protection setting process, the problem caused by the fact that the distribution network current protection setting is conducted through scattered photovoltaic access is solved, the distribution network current protection setting calculation with multiple photovoltaic equipment access can be simplified, and errors meet the protection setting requirements, so that the configuration and the setting of relay protection of the distribution network can be guided, and the safety and the stability of the distribution network are protected.
Fig. 5 is a block schematic diagram of a photovoltaic device cluster equivalent calculating device in a power distribution network current protection setting process according to an embodiment of the present invention. As shown in fig. 5, the photovoltaic device cluster equivalence calculating device in the distribution network current protection setting process includes: a first obtaining module 100, a second obtaining module 200, a first calculating module 300, a second calculating module 400 and a tuning module 500.
The first obtaining module 100 is configured to obtain a power distribution network line parameter and a total access capacity of the photovoltaic device. The second obtaining module 200 is configured to obtain branch photovoltaic devices according to the power distribution network line parameters and the total access capacity. The first calculation module 300 is configured to calculate the trunk line photovoltaic device through a lever-like photovoltaic cluster equivalence algorithm to obtain a head-end photovoltaic device and a tail-end photovoltaic device. The second calculating module 400 is configured to calculate short-circuit current values of the branch photovoltaic device, the head-end photovoltaic device, and the tail-end photovoltaic device at the protection installation location according to the transient characteristics of the photovoltaic devices. The setting module 500 is used for setting the photovoltaic equipment in the power distribution network current protection setting process according to the short-circuit current values of the branch photovoltaic equipment, the head end photovoltaic equipment and the tail end photovoltaic equipment at the protection installation position.
According to an embodiment of the present invention, the first obtaining module is specifically configured to: acquiring a topological structure of a power distribution network and short-circuit impedance, line topology and impedance of the power distribution network; acquiring a node number of the photovoltaic equipment and an access photovoltaic capacity corresponding to the node number; and obtaining the total access capacity of the photovoltaic equipment according to the topological structure of the power distribution network, the node number of the photovoltaic equipment and the access photovoltaic capacity corresponding to the node number.
According to one embodiment of the invention, the capacity of the head-end photovoltaic installation and the capacity S' of the tail-end photovoltaic installation are calculated according to the following formulas:
the capacity S "of the trailing photovoltaic device is calculated according to the following formula:
wherein z is the unit impedance of the power distribution network line, knl is the length of n sections of lines, and n is a positive integer.
According to an embodiment of the present invention, the second calculating module is specifically configured to: equating the photovoltaic device as a current source according to transient characteristics of the photovoltaic device; and obtaining the current value of the current source according to the control characteristic of the photovoltaic equipment and the voltage at the grid-connected position of the photovoltaic equipment.
According to one embodiment of the invention, the transient behavior of the photovoltaic device is obtained by the following formula:
wherein, IPVShort-circuit current output for photovoltaic installations, IratedIs the rated current of the photovoltaic device, PratedFor rated power of photovoltaic plants, UpccFor the named value of the grid-connected point voltage,
and p.u is a unit of per unit value of the voltage of the grid-connected point.
It should be noted that the explanation of the foregoing embodiment of the photovoltaic device cluster equivalence method in the power distribution network current protection setting process is also applicable to the photovoltaic device cluster equivalence device in the power distribution network current protection setting process of this embodiment, and details are not repeated here.
According to the photovoltaic equipment cluster equivalence calculating device in the power distribution network current protection setting process, the problem caused by power distribution network current protection setting through scattered photovoltaic access is solved, power distribution network current protection setting calculation containing multiple photovoltaic equipment accesses can be simplified, and errors meet protection setting requirements, so that configuration and setting of relay protection of the power distribution network can be guided, and safety and stability of the power distribution network are protected.
Furthermore, the terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one such feature. In the description of the present invention, "a plurality" means at least two, e.g., two, three, etc., unless specifically limited otherwise.
In the present invention, unless otherwise expressly stated or limited, the terms "mounted," "connected," "secured," and the like are to be construed broadly and can, for example, be fixedly connected, detachably connected, or integrally formed; can be mechanically or electrically connected; they may be directly connected or indirectly connected through intervening media, or they may be connected internally or in any other suitable relationship, unless expressly stated otherwise. The specific meanings of the above terms in the present invention can be understood by those skilled in the art according to specific situations.
In the description herein, references to the description of the term "one embodiment," "some embodiments," "an example," "a specific example," or "some examples," etc., mean that a particular feature, structure, material, or characteristic described in connection with the embodiment or example is included in at least one embodiment or example of the invention. In this specification, the schematic representations of the terms used above are not necessarily intended to refer to the same embodiment or example. Furthermore, the particular features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, various embodiments or examples and features of different embodiments or examples described in this specification can be combined and combined by one skilled in the art without contradiction.
Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention, and that variations, modifications, substitutions and alterations can be made to the above embodiments by those of ordinary skill in the art within the scope of the present invention.
Claims (10)
1. A photovoltaic equipment cluster equivalence calculation method in a power distribution network current protection setting process is characterized by comprising the following steps:
acquiring power distribution network line parameters and the total access capacity of photovoltaic equipment;
obtaining the branch photovoltaic equipment according to the power distribution network line parameters and the total access capacity;
calculating the trunk line photovoltaic equipment through a lever-like photovoltaic cluster equivalent algorithm to obtain head-end photovoltaic equipment and tail-end photovoltaic equipment;
respectively calculating short-circuit current values of the branch photovoltaic equipment, the head-end photovoltaic equipment and the tail-end photovoltaic equipment at a protective installation position according to the transient characteristics of the photovoltaic equipment; and
and setting the photovoltaic equipment in the power distribution network current protection setting process according to the short-circuit current values of the branch photovoltaic equipment, the head end photovoltaic equipment and the tail end photovoltaic equipment at the protection installation position.
2. The method of claim 1, wherein the obtaining of the distribution network line parameters and the total access capacity of the photovoltaic devices comprises:
acquiring a topological structure of the power distribution network and short-circuit impedance, line topology and impedance of the power distribution network;
acquiring a node number of the photovoltaic equipment and an access photovoltaic capacity corresponding to the node number;
and obtaining the total access capacity of the photovoltaic equipment according to the topological structure of the power distribution network, the node number of the photovoltaic equipment and the access photovoltaic capacity corresponding to the node number.
3. The method of claim 2, wherein the capacity of the head-end photovoltaic plant and the capacity S' of the tail-end photovoltaic plant are calculated according to the following equations:
calculating the capacity S "of the tail-end photovoltaic device according to the following formula:
wherein z is the unit impedance of the power distribution network line, knl is the length of n sections of lines, and n is a positive integer.
4. The method of claim 1, wherein the calculating the short circuit current values of the branch photovoltaic device, the head-end photovoltaic device and the tail-end photovoltaic device at the protective installation according to the transient characteristics of the photovoltaic devices comprises:
according to the transient characteristics of the photovoltaic equipment, the photovoltaic equipment is equivalent to a current source;
and obtaining the current value of the current source according to the control characteristic of the photovoltaic equipment and the voltage at the grid-connected position of the photovoltaic equipment.
5. The method according to claim 4, wherein the transient characteristics of the photovoltaic device are obtained by the following formula:
wherein, IPVShort-circuit current output for photovoltaic installations, IratedIs the rated current of the photovoltaic device, PratedFor rated power of photovoltaic plants, UpccFor the named value of the grid-connected point voltage,
and p.u is a unit of per unit value of the voltage of the grid-connected point.
6. A photovoltaic equipment cluster equivalence calculating device in a power distribution network current protection setting process is characterized by comprising the following steps:
the first acquisition module is used for acquiring power distribution network line parameters and the total access capacity of the photovoltaic equipment;
the second acquisition module is used for acquiring the branch photovoltaic equipment according to the power distribution network line parameters and the total access capacity;
the first calculation module is used for calculating the trunk line photovoltaic equipment through a lever-like photovoltaic cluster equivalent algorithm to obtain head-end photovoltaic equipment and tail-end photovoltaic equipment;
the second calculation module is used for respectively calculating short-circuit current values of the branch photovoltaic equipment, the head-end photovoltaic equipment and the tail-end photovoltaic equipment at a protection installation position according to the transient characteristics of the photovoltaic equipment; and
and the setting module is used for setting the photovoltaic equipment in the power distribution network current protection setting process according to the short-circuit current values of the branch photovoltaic equipment, the head end photovoltaic equipment and the tail end photovoltaic equipment at the protection installation position.
7. The apparatus of claim 6, wherein the first obtaining module is specifically configured to:
acquiring a topological structure of the power distribution network and short-circuit impedance, line topology and impedance of the power distribution network;
acquiring a node number of the photovoltaic equipment and an access photovoltaic capacity corresponding to the node number;
and obtaining the total access capacity of the photovoltaic equipment according to the topological structure of the power distribution network, the node number of the photovoltaic equipment and the access photovoltaic capacity corresponding to the node number.
8. The apparatus of claim 7, wherein the capacity of the head-end photovoltaic device and the capacity S' of the tail-end photovoltaic device are calculated according to the following equations:
calculating the capacity S "of the tail-end photovoltaic device according to the following formula:
wherein z is the unit impedance of the power distribution network line, knl is the length of n sections of lines, and n is a positive integer.
9. The apparatus of claim 6, wherein the second computing module is specifically configured to:
according to the transient characteristics of the photovoltaic equipment, the photovoltaic equipment is equivalent to a current source;
and obtaining the current value of the current source according to the control characteristic of the photovoltaic equipment and the voltage at the grid-connected position of the photovoltaic equipment.
10. The apparatus of claim 9, wherein the transient characteristics of the photovoltaic device are obtained by the following equation:
wherein, IPVShort-circuit current output for photovoltaic installations, IratedIs the rated current of the photovoltaic device, PratedFor rated power of photovoltaic plants, UpccFor the named value of the grid-connected point voltage,
and p.u is a unit of per unit value of the voltage of the grid-connected point.
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| CN115021209A (en) * | 2022-08-08 | 2022-09-06 | 国网江西省电力有限公司电力科学研究院 | Photovoltaic string short-circuit protection method and device |
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