CN107508323B - Low-voltage distribution room distributed photovoltaic access capability assessment method and system - Google Patents

Low-voltage distribution room distributed photovoltaic access capability assessment method and system Download PDF

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CN107508323B
CN107508323B CN201710874616.5A CN201710874616A CN107508323B CN 107508323 B CN107508323 B CN 107508323B CN 201710874616 A CN201710874616 A CN 201710874616A CN 107508323 B CN107508323 B CN 107508323B
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胡列翔
郑伟民
张全明
沈梁
傅旭华
王蕾
王坤
张西竹
王强强
谈历
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State Grid Corp of China SGCC
Economic and Technological Research Institute of State Grid Zhejiang Electric Power Co Ltd
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Abstract

The invention discloses a method and a system for evaluating distributed photovoltaic access capacity of a low-voltage transformer area. The existing low-voltage distribution network has the problem that a large number of medium-sized and small-sized distributed photovoltaic devices are accessed, and particularly the problem that the power supply capacity of a household photovoltaic device after the household photovoltaic device is accessed is difficult to evaluate. According to the invention, through the first section of two-port network equivalence of the terminal node, equivalent network parameters are calculated by using input and output states at different moments, the influence of distributed photovoltaic on the node and the first section of voltage can be calculated under the condition that the line parameters of a distribution network in a low-voltage transformer area are not obtained, meanwhile, the traditional simple planning design mode that a plurality of transformers are added to operate in parallel or a parallel newly-built distributed photovoltaic special distribution network is adopted is changed, and the overall investment of the distribution network is reduced by accurately evaluating the current carrying capacity of the low-voltage distribution network.

Description

Low-voltage distribution room distributed photovoltaic access capability assessment method and system
Technical Field
The invention belongs to the field of planning of distributed photovoltaic access low-voltage power distribution networks, and particularly relates to a low-voltage distribution area distributed photovoltaic access capacity evaluation method and system based on port equivalence.
Background
The poverty relief in China is rapid with the development of household distributed photovoltaic, the national grid company releases access to the distributed photovoltaic according to the national policy, but the access capacity is overlarge in the actual engineering, the intermittent fluctuation of the voltage of a distributed photovoltaic access area is increased, and partial voltage is out of limit, so that the public voltage quality in a low-voltage transformer area is influenced.
Therefore, relevant scholars in China carry out research on the aspects of a control mode of a distributed photovoltaic body, grid planning or local consumption of a medium-voltage side and the like, but neglect the planning of a power distribution network in a low-voltage distribution area, and lack the evaluation on the capability of accepting distributed photovoltaic by the low-voltage distribution area, so that excessive investment in engineering is caused, and if a plurality of transformers are added to operate in parallel or a parallel newly-built distributed photovoltaic special power distribution network is adopted, the problem that an effective evaluation tool is lacked in the investment of photovoltaic access to the low-voltage power distribution network is reflected.
Disclosure of Invention
The invention provides a low-voltage distribution network distributed photovoltaic access capacity evaluation method based on port equivalence, aiming at the problem that the existing low-voltage distribution network is difficult to evaluate the power supply capacity after a large number of medium-sized and small-sized distributed photovoltaics are accessed, particularly a user is accessed with photovoltaics, so that the current carrying capacity of the low-voltage distribution network is accurately evaluated, and the overall investment of the low-voltage distribution network is reduced.
Therefore, the invention adopts the following technical scheme: a low-voltage distribution area distributed photovoltaic access capacity evaluation method comprises the following steps:
1) selecting a low-voltage transformer area with photovoltaic power generation access, reading user numbers, active current, reactive current and voltage data of a user electric energy meter through a collector of the low-voltage transformer area, reading active current, reactive current and voltage data of a low-voltage side of a transformer through a distribution transformer monitoring terminal, requiring all data to be called once, ensuring the simultaneity of the data, and neglecting communication delay;
2) storing active current, reactive current, voltage data, user numbers and time scales of all single-phase or three-phase electric energy meters in the low-voltage transformer area called each time, and accurately measuring the time scales to be minutes;
3) reading and storing the current transformer transformation ratio of all single-phase or three-phase electric energy meters in the low-voltage transformer area, and taking the primary value as the maximum current I allowed to be accessed by the node Ii_max；
4) Inquiring user files according to user numbers of all single-phase or three-phase electric energy meters in the low-voltage distribution area, and determining the types of the users of the node i, including no power generation, spontaneous self-use and full-amount internet access;
5) taking the outgoing line position of a transformer in a low-voltage transformer area as a head end, acquiring active current, reactive current, voltage data, a user number and a time scale of a head section and a node i at 2 moments in stored data, wherein two groups of data are required to be different, and calculating equivalent two-port network parameters between the ith node and the head end;
6) active current, reactive current and voltage data of the first section of the spring-divided-day noon are selected, and the maximum current value I of the node I is comparedi_maxAs active current, setting reactive current as zero, calculating whether the voltage of a node i meets the upper and lower 10% deviation of 220V or not through the obtained equivalent two-port network parameters, if so, taking the voltage as the maximum current access capacity of the node, and if not, reducing the active current by taking 5% as step length until the voltage meets the maximum current access capacity of the node;
7) and according to the user types associated with the user numbers in the low-voltage transformer area, the sum of the maximum access current of photovoltaic-free power generation, full-rate internet surfing and spontaneous self-use is classified and counted, and the sum is used as the access capacity index of various users.
As a supplement to the above technical solution, in the step 5), the equivalent two-port network adopts a T-type network.
As a supplement to the above technical solution, the solution formula of the equivalent two-port network parameter is as follows:
Figure BDA0001417845910000031
in the formula (I), the compound is shown in the specification,
Figure BDA0001417845910000032
respectively at the first momentThe voltage and current values of the two ports,
Figure BDA0001417845910000033
Figure BDA0001417845910000034
the voltage and current values of the two ports at the second moment are respectively, the first subscript number of the symbol is a port number, and the second subscript number of the symbol is a moment number;
Z1，Z2，Z3three equivalent impedances for the T-network are shown.
As a supplement to the above technical solution, in step 6), the voltage of the node i is calculated by the following formula:
Figure BDA0001417845910000035
in the formula (I), the compound is shown in the specification,
Figure BDA0001417845910000036
the current flowing into the first port is controlled,
Figure BDA0001417845910000037
the current flowing into the second port or output port,
Figure BDA0001417845910000038
is the voltage of the second port.
As a supplement to the above technical solution, in the step 5), the specific content that two sets of data are required to be different is: and judging whether the relative difference value of the active current and the reactive current of the two groups of data is within 10%, if so, deleting one group, and reading a new group until the relative difference value of the active current and the reactive current of the two groups of data is more than or equal to 10%.
Another object of the present invention is to provide a low-voltage distribution grid area distributed photovoltaic access capability evaluation system, which includes:
a data reading module: selecting a low-voltage transformer area with photovoltaic power generation access, reading user numbers, active current, reactive current and voltage data of a user electric energy meter through a collector of the low-voltage transformer area, reading active current, reactive current and voltage data of a low-voltage side of a transformer through a distribution transformer monitoring terminal, requiring all data to be called once, ensuring the simultaneity of the data, and neglecting communication delay;
a data storage module: storing active current, reactive current, voltage data, user numbers and time scales of all single-phase or three-phase electric energy meters in the low-voltage transformer area called each time, and accurately measuring the time scales to be minutes;
the node is connected with a maximum current selection module: reading and storing the current transformer transformation ratio of all single-phase or three-phase electric energy meters in the low-voltage transformer area, and taking the primary value as the maximum current I allowed to be accessed by the node Ii_max；
A node user type determination module: inquiring user files according to user numbers of all single-phase or three-phase electric energy meters in the low-voltage distribution area, and determining the types of the users of the node i, including no power generation, spontaneous self-use and full-amount internet access;
the equivalent two-port network parameter calculation module: taking the outgoing line position of a transformer in a low-voltage transformer area as a head end, acquiring active current, reactive current, voltage data, a user number and a time scale of a head section and a node i at 2 moments in stored data, wherein two groups of data are required to be different, and calculating equivalent two-port network parameters between the ith node and the head end;
the current maximum access capability determining module: active current, reactive current and voltage data of the first section of the spring-divided-day noon are selected, and the maximum current value I of the node I is comparedi_maxAs active current, setting reactive current as zero, calculating whether the voltage of a node i meets the upper and lower 10% deviation of 220V or not through the obtained equivalent two-port network parameters, if so, taking the voltage as the maximum current access capacity of the node, and if not, reducing the active current by taking 5% as step length until the voltage meets the maximum current access capacity of the node;
an access capability index calculation module: and according to the user types associated with the user numbers in the low-voltage transformer area, the sum of the maximum access current of photovoltaic-free power generation, full-rate internet surfing and spontaneous self-use is classified and counted, and the sum is used as the access capacity index of various users.
The invention has the following beneficial effects: according to the invention, through the first section of two-port network equivalence of the terminal node, equivalent network parameters are calculated by using input and output states at different moments, the influence of distributed photovoltaic on the node and the first section of voltage can be calculated under the condition that the line parameters of a distribution network in a low-voltage transformer area are not obtained, meanwhile, the traditional simple planning design mode that a plurality of transformers are added to operate in parallel or a parallel newly-built distributed photovoltaic special distribution network is adopted is changed, and the overall investment of the distribution network is reduced by accurately evaluating the current carrying capacity of the low-voltage distribution network.
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FIG. 1 is a schematic diagram showing the structure of a T-type network in embodiment 1 of the present invention;
fig. 2 is a schematic flow chart of embodiment 1 of the present invention.
Detailed Description
Example 1
The embodiment is a method for evaluating the distributed photovoltaic access capacity of a low-voltage transformer area, which comprises the following steps:
1) the method comprises the steps of selecting a low-voltage transformer area with photovoltaic power generation access, reading user numbers, active current, reactive current and voltage data of a user electric energy meter through a collector of the low-voltage transformer area, reading active current, reactive current and voltage data of a low-voltage side of a transformer through a distribution transformer monitoring terminal, calling all data at one time, ensuring the simultaneity of the data and neglecting communication delay.
2) And storing active current, reactive current, voltage data, user numbers and time scales of all single-phase or three-phase electric energy meters in the low-voltage transformer area called each time, and the accuracy is up to minutes.
3) Reading and storing the current transformer transformation ratio of all single-phase or three-phase electric energy meters in the low-voltage transformer area, and taking the primary value as the maximum current I allowed to be accessed by the node Ii_max。
4) And inquiring user files according to the user numbers of all single-phase or three-phase electric energy meters in the low-voltage distribution area, and determining the types of the users of the node i, including no power generation, spontaneous self-use and full-amount internet access.
5) Taking the outlet position of a transformer in a low-voltage transformer area as a head end, acquiring active current, reactive current, voltage data, a user number and a time scale of a head section and a node i at 2 moments in stored data, judging whether the relative difference value of the active current and the reactive current of two groups of data is within 10%, if so, deleting one group of the two groups of data, reading a new group of the two groups of data until the relative difference value of the active current and the reactive current of the two groups of data is more than or equal to 10%, and calculating equivalent two-port network parameters between the ith node and the head end; the equivalent two-port network adopts a T-type network, and the solving formula of the equivalent two-port network parameters is as follows:
Figure BDA0001417845910000061
in the formula (I), the compound is shown in the specification,
Figure BDA0001417845910000062
the voltage and current values of the two ports at the first moment,
Figure BDA0001417845910000063
Figure BDA0001417845910000064
the voltage and current values of the two ports at the second moment are respectively, the first subscript number of the symbol is a port number, and the second subscript number of the symbol is a moment number;
Z1，Z2，Z3three equivalent impedances for the T-network are shown.
6) Active current, reactive current and voltage data of the first section of the spring-divided-day noon are selected, and the maximum current value I of the node I is comparedi_maxAs active current, setting reactive current as zero, calculating whether the voltage of a node i meets the upper and lower 10% deviation of 220V or not through the obtained equivalent two-port network parameters, if so, taking the voltage as the maximum current access capacity of the node, and if not, reducing the active current by taking 5% as step length until the voltage meets the maximum current access capacity of the node; the voltage at node i is calculated by:
Figure BDA0001417845910000065
in the formula (I), the compound is shown in the specification,
Figure BDA0001417845910000066
the current flowing into the first port is controlled,
Figure BDA0001417845910000067
the current flowing into the second port or output port,
Figure BDA0001417845910000068
is the voltage of the second port.
7) And according to the user types associated with the user numbers in the low-voltage transformer area, the sum of the maximum access current of photovoltaic-free power generation, full-rate internet surfing and spontaneous self-use is classified and counted, and the sum is used as the access capacity index of various users.
Example 2
The embodiment is a low-voltage distribution room distributed photovoltaic access capability evaluation system, which includes:
a data reading module: selecting a low-voltage transformer area with photovoltaic power generation access, reading user numbers, active current, reactive current and voltage data of a user electric energy meter through a collector of the low-voltage transformer area, reading active current, reactive current and voltage data of a low-voltage side of a transformer through a distribution transformer monitoring terminal, requiring all data to be called once, ensuring the simultaneity of the data, and neglecting communication delay;
a data storage module: storing active current, reactive current, voltage data, user numbers and time scales of all single-phase or three-phase electric energy meters in the low-voltage transformer area called each time, and accurately measuring the time scales to be minutes;
the node is connected with a maximum current selection module: reading and storing the current transformer transformation ratio of all single-phase or three-phase electric energy meters in the low-voltage transformer area, and taking the primary value as the maximum current I allowed to be accessed by the node Ii_max；
A node user type determination module: inquiring user files according to user numbers of all single-phase or three-phase electric energy meters in the low-voltage distribution area, and determining the types of the users of the node i, including no power generation, spontaneous self-use and full-amount internet access;
the equivalent two-port network parameter calculation module: taking the outgoing line position of a transformer in a low-voltage transformer area as a head end, acquiring active current, reactive current, voltage data, a user number and a time scale of a head section and a node i at 2 moments in stored data, wherein two groups of data are required to be different, and calculating equivalent two-port network parameters between the ith node and the head end;
the current maximum access capability determining module: active current, reactive current and voltage data of the first section of the spring-divided-day noon are selected, and the maximum current value I of the node I is comparedi_maxAs active current, setting reactive current as zero, calculating whether the voltage of a node i meets the upper and lower 10% deviation of 220V or not through the obtained equivalent two-port network parameters, if so, taking the voltage as the maximum current access capacity of the node, and if not, reducing the active current by taking 5% as step length until the voltage meets the maximum current access capacity of the node;
an access capability index calculation module: and according to the user types associated with the user numbers in the low-voltage transformer area, the sum of the maximum access current of photovoltaic-free power generation, full-rate internet surfing and spontaneous self-use is classified and counted, and the sum is used as the access capacity index of various users.
The above embodiments are illustrative of the present invention, and are not intended to limit the present invention, and any simple modifications of the present invention are within the scope of the present invention.

Claims (10)

1. A low-voltage distribution type photovoltaic access capacity evaluation method is characterized by comprising the following steps:
1) selecting a low-voltage transformer area with photovoltaic power generation access, reading user numbers, active current, reactive current and voltage data of a user electric energy meter through a collector of the low-voltage transformer area, reading active current, reactive current and voltage data of a low-voltage side of a transformer through a distribution transformer monitoring terminal, requiring all data to be called once, ensuring the simultaneity of the data, and neglecting communication delay;
2) storing active current, reactive current, voltage data, user numbers and time scales of all single-phase or three-phase electric energy meters in the low-voltage transformer area called each time, and accurately measuring the time scales to be minutes;
3) reading and storing the current transformer transformation ratio of all single-phase or three-phase electric energy meters in the low-voltage transformer area, and taking the primary value as the maximum current I allowed to be accessed by the node Ii_max；
4) Inquiring user files according to user numbers of all single-phase or three-phase electric energy meters in the low-voltage distribution area, and determining the types of the users of the node i, including photovoltaic power generation free, spontaneous self-use and full-amount internet surfing;
5) taking the outgoing line position of a transformer in a low-voltage transformer area as a head end, acquiring active current, reactive current, voltage data, a user number and a time scale of a head section and a node i at 2 moments in stored data, wherein two groups of data are required to be different, and calculating equivalent two-port network parameters between the ith node and the head end;
6) active current, reactive current and voltage data of the first section of the spring-divided-day noon are selected, and the maximum current value I of the node I is comparedi_maxAs active current, setting reactive current as zero, calculating whether the voltage of a node i meets the upper and lower 10% deviation of 220V or not through the obtained equivalent two-port network parameters, if so, taking the voltage as the maximum current access capacity of the node, and if not, reducing the active current by taking 5% as step length until the voltage meets the maximum current access capacity of the node;
7) and according to the user types associated with the user numbers in the low-voltage transformer area, the sum of the maximum access current of photovoltaic-free power generation, full-rate internet surfing and spontaneous self-use is classified and counted, and the sum is used as the access capacity index of various users.
2. The low-voltage distribution network photovoltaic access capability evaluation method as claimed in claim 1, wherein in the step 5), the equivalent two-port network is a T-type network.
3. The low-voltage transformer area distributed photovoltaic access capability evaluation method according to claim 2, wherein the solution formula of the equivalent two-port network parameters is as follows:
Figure FDA0002312646450000021
in the formula (I), the compound is shown in the specification,
Figure FDA0002312646450000022
the voltage and current values of the two ports at the first moment,
Figure FDA0002312646450000023
Figure FDA0002312646450000024
the voltage and current values of the two ports at the second moment are respectively, the first subscript number of the symbol is a port number, and the second subscript number of the symbol is a moment number;
Z1，Z2，Z3three equivalent impedances for the T-network are shown.
4. The method for evaluating the distributed photovoltaic access capability of the low-voltage transformer area according to claim 3, wherein in the step 6), the voltage of the node i is calculated by the following formula:
Figure FDA0002312646450000025
in the formula (I), the compound is shown in the specification,
Figure FDA0002312646450000026
the current flowing into the first port is controlled,
Figure FDA0002312646450000027
the current flowing in for the second port,
Figure FDA0002312646450000028
is the voltage at the second port, i.e., the output port.
5. The method for evaluating the distributed photovoltaic access capability of the low-voltage transformer area according to claim 1, wherein in the step 5), the specific contents that two sets of data are required to be different are as follows: and judging whether the relative difference value of the active current and the reactive current of the two groups of data is within 10%, if so, deleting one group, and reading a new group until the relative difference value of the active current and the reactive current of the two groups of data is more than or equal to 10%.
6. A low-voltage distribution type photovoltaic access capability evaluation system is characterized by comprising:
a data reading module: selecting a low-voltage transformer area with photovoltaic power generation access, reading user numbers, active current, reactive current and voltage data of a user electric energy meter through a collector of the low-voltage transformer area, reading active current, reactive current and voltage data of a low-voltage side of a transformer through a distribution transformer monitoring terminal, requiring all data to be called once, ensuring the simultaneity of the data, and neglecting communication delay;
a data storage module: storing active current, reactive current, voltage data, user numbers and time scales of all single-phase or three-phase electric energy meters in the low-voltage transformer area called each time, and accurately measuring the time scales to be minutes;
the node is connected with a maximum current selection module: reading and storing the current transformer transformation ratio of all single-phase or three-phase electric energy meters in the low-voltage transformer area, and taking the primary value as the maximum current I allowed to be accessed by the node Ii_max；
A node user type determination module: inquiring user files according to user numbers of all single-phase or three-phase electric energy meters in the low-voltage distribution area, and determining the types of the users of the node i, including photovoltaic power generation free, spontaneous self-use and full-amount internet surfing;
the equivalent two-port network parameter calculation module: taking the outgoing line position of a transformer in a low-voltage transformer area as a head end, acquiring active current, reactive current, voltage data, a user number and a time scale of a head section and a node i at 2 moments in stored data, wherein two groups of data are required to be different, and calculating equivalent two-port network parameters between the ith node and the head end;
the current maximum access capability determining module: active current, reactive current and voltage data of the first section of the spring-divided-day noon are selected, and the maximum current value I of the node I is comparedi_maxAs active current, setting reactive current as zero, calculating whether the voltage of a node i meets the upper and lower 10% deviation of 220V or not through the obtained equivalent two-port network parameters, if so, taking the voltage as the maximum current access capacity of the node, and if not, reducing the active current by taking 5% as step length until the voltage meets the maximum current access capacity of the node;
an access capability index calculation module: and according to the user types associated with the user numbers in the low-voltage transformer area, the sum of the maximum access current of photovoltaic-free power generation, full-rate internet surfing and spontaneous self-use is classified and counted, and the sum is used as the access capacity index of various users.
7. The system for evaluating the distributed photovoltaic access capability of the low-voltage transformer area according to claim 6, wherein in the equivalent two-port network parameter calculation module, a T-type network is adopted as an equivalent two-port network.
8. The low-voltage distribution room distributed photovoltaic access capability evaluation system as claimed in claim 7, wherein the solution formula of the equivalent two-port network parameters is as follows:
Figure FDA0002312646450000041
in the formula (I), the compound is shown in the specification,
Figure FDA0002312646450000042
the voltage and current values of the two ports at the first moment,
Figure FDA0002312646450000043
Figure FDA0002312646450000044
the voltage and current values of the two ports at the second moment are respectively, the first subscript number of the symbol is a port number, and the second subscript number of the symbol is a moment number;
Z1，Z2，Z3three of the T-type network, respectivelyThe effective impedance.
9. The system for evaluating the distributed photovoltaic access capability of the low-voltage transformer area according to claim 8, wherein in the module for determining the maximum current access capability, the voltage of the node i is calculated by the following formula:
Figure FDA0002312646450000045
in the formula (I), the compound is shown in the specification,
Figure FDA0002312646450000046
the current flowing into the first port is controlled,
Figure FDA0002312646450000047
the current flowing into the second port or output port,
Figure FDA0002312646450000048
is the voltage of the second port.
10. The low-voltage distribution room distributed photovoltaic access capability evaluation system of claim 6, wherein the specific contents requiring two different sets of data in the equivalent two-port network parameter calculation module are as follows: and judging whether the relative difference value of the active current and the reactive current of the two groups of data is within 10%, if so, deleting one group, and reading a new group until the relative difference value of the active current and the reactive current of the two groups of data is more than or equal to 10%.
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