CN104348180B - Distributed power supply grid-connected point and access mode selection method - Google Patents

Abstract

The invention discloses a method for selecting a grid-connected point and an access mode of a distributed power source, comprising the following steps: 1) determining the power generation characteristics of a distributed power source that needs to be grid-connected; 2) understanding the grid situation in the area where the distributed power source is located, and counting Calculate the weighted average value of the main transformer capacity of each voltage level for the single main transformer capacity and load size of the public substation with voltage level; 3) Preliminarily select the grid-connected voltage level according to the power generation capacity of the distributed power supply; 4) Determine the distributed power supply Access method; 5) Determine the access point of the distributed power supply. Adopting the distributed power grid connection point and the method for selecting the access mode of the present invention can minimize the impact of its access on the safe and stable operation of the grid under the premise of ensuring that the distributed power grid is effectively connected to the grid.

Description

Distributed power grid-connected point and access method selection method

technical field

The invention relates to the field of power supply, in particular to a method for selecting a grid connection point and an access mode of a distributed power supply.

Background technique

With the rapid development of wind power generation, photovoltaic power generation, biomass power generation and other energy-saving and environment-friendly power sources, the proportion of their power generation is increasing year by year. Wind power generation, photovoltaic power generation, biomass power generation and other types of new energy power generation generally have relatively small capacity, and are integrated into low-voltage power grids in the form of distributed power sources. Different from traditional large-capacity power supplies that are directly integrated into high-voltage power grids, distributed power supplies come in a variety of forms, and each type of power supply has its own operating characteristics; and distributed power supplies are close to the user side, which will change the traditional power grid. The radial power supply structure of the system has an impact on the safe and stable operation of the distribution network, power quality, active/reactive power control, protection and communication.

The above impacts will bring new challenges to the power grid, especially the distribution network operation enterprises. How to minimize the impact of distributed power generation on the safe and stable operation of the power grid under the premise of ensuring the effective access of distributed power to the power grid is the current engineering practice. A difficult problem that needs to be solved urgently.

Contents of the invention

The purpose of the present invention is to provide a method for selecting distributed power grid-connection points and access modes that can address the characteristics of distributed power generation, combine the urban distribution network grid structure, and comprehensively consider the factors affecting the distributed power access to the regional power grid.

In order to achieve the above object, the technical scheme of the present invention is as follows:

A method for selecting a grid-connected point and an access mode of a distributed power supply, comprising the following steps:

1) Determine the power generation characteristics of distributed power sources that need to be connected to the grid;

2) Understand the power grid situation in the area where the distributed power supply is located, count the single main transformer capacity and load size of the public substation at each voltage level, and calculate the weighted average of the main transformer capacity at each voltage level;

3) Preliminarily select the grid-connected voltage level according to the power generation capacity of the distributed power supply;

4) Determine the access mode of the distributed power supply;

5) Determine the access point of the distributed power supply.

Preferably, the distributed power sources in step 1) include synchronous motors, asynchronous motors and converter-type distributed power sources.

Preferably, the calculation formula for calculating the weighted average value of the main variable capacity of each voltage level in step 2) is as follows,

in,

- The weighted average of the main transformer capacity with access voltage "i" kV in the area where the distributed power generation is located;

i-voltage level, generally can take 380V, 10kV, 35kV, etc.;

ni - the number of main transformers with a voltage of "i" kV in the area where the distributed power supply is located;

T _ij - the area where the distributed power supply is located has the capacity of the jth main transformer with a voltage of "i" kV voltage level;

L _ij - the load rate of the jth main transformer with a voltage of "i" kV voltage level in the area where the distributed power supply is located;

L-constant is the threshold value of the main transformer load rate, which can be selected according to the grid situation;

if((L _ij -L)>0)-judgment weight, its value is 1 when (L _ij -L)>0, otherwise the value is 0.

Preferably, the formula for selecting its grid-connected voltage level in step 3) is as follows,

in,

In the above formula,

-The weighted average of the main transformer capacity with voltage "i" kV in the area where the distributed power generation is located;

i-voltage level, generally can take 380V, 10kV, 35kV, etc.;

N _T - a constant greater than 1;

C _DER - the installed capacity of the distributed power generation;

- a value when When the value is 1, otherwise it is 0;

V _DERi - The initial selection flag of the distributed power access voltage level. When its value is 1, it means that it can be integrated into the power grid with a voltage of "i" kV. Generally, two voltage levels are sufficient.

Preferably, the determination formula of the access mode of the distributed power supply in step 4) is,

in,

C _L - the transmission capacity of the grid-connected line;

N _l - a constant greater than 1;

F _DER - the access method of distributed power generation, its value is 1, which means that non-dedicated line access is available, and its value is 0, which means that dedicated line access is used.

Preferably, the step of determining the access point of the distributed power supply in step 5) is as follows,

If F _DER = 0, select the main transformer in the voltage level corresponding to the V _DERi flag, perform a weight calculation according to the formula (d), and then sort it, and take the one corresponding to the smallest value among the values D _ij is not zero The "i" kV voltage level side of the main transformer is used as the access point of the distributed power supply;

in,

m _maxij - the number of outgoing line intervals where the voltage of the j-th main transformer is "i"kV;

m _ij - The voltage of the jth main transformer at present is the number of outgoing lines in the "i" kV outgoing line interval;

n _ij - the number of distributed power sources connected to the kV side of the status quo where the voltage of the jth main transformer is "i";

C _DERk - The voltage of the jth main transformer at present is the installed capacity of the kth distributed power supply on the "i" kV side;

d _ij - the voltage from the distributed power supply to the jth main transformer is the distance from the grid-connected power line on the kV side of "i";

d _i - the upper limit of the reasonable power supply distance stipulated by the power supply company for the voltage level of "i"kV;

If F _DER = 1, then the distributed power supply is connected to a line with a voltage of "i" kV nearby;

If V _DERi = 1, but the "i" kV power grid does not meet the conditions determined above, it is necessary to transfer to the previous voltage level network of the "i" kV power grid to select the grid-connection point and access mode until a suitable one is determined. Up to the grid connection point and access mode; T _ij - the area where the distributed power supply is located has the capacity of the jth main transformer with a voltage of "i" kV voltage level.

According to the characteristics of distributed power generation, combined with the grid structure of urban distribution network, the distributed power grid connection point and access mode selection method of the present invention is proposed to comprehensively consider the influence factors of distributed power access to the regional power grid, in order to ensure that distributed power Under the premise of effectively connecting to the grid, the impact of its access on the safe and stable operation of the grid is minimized.

detailed description

The distributed power grid-connected point and access method selection method of the present invention comprises the following steps:

1) Determine the power generation characteristics of distributed power sources that need to be connected to the grid. Among them, distributed power sources include synchronous motors, asynchronous motors and converter-type distributed power sources.

2) Understand the power grid situation in the area where the distributed power supply is located, count the single main transformer capacity and load size of each voltage level public substation, and calculate the weighted average of the main transformer capacity of each voltage level, among which, calculate the weighted average of the main transformer capacity of each voltage level The formula for calculating the value is as follows,

In the above formula,

- The weighted average of the main transformer capacity with access voltage "i" kV in the area where the distributed power generation is located;

i-voltage level, generally can take 380V, 10kV, 35kV, etc.;

ni - the number of main transformers with a voltage of "i" kV in the area where the distributed power supply is located;

T _ij - the area where the distributed power supply is located has the capacity of the jth main transformer with a voltage of "i" kV voltage level;

L _ij - the load rate of the jth main transformer with a voltage of "i" kV voltage level in the area where the distributed power supply is located;

L-constant is the threshold value of the main transformer load rate, which can be selected according to the grid situation;

if((L _ij -L)>0)-judgment weight, its value is 1 when (L _ij -L)>0, otherwise the value is 0.

3) Preliminarily select the grid-connected voltage level according to the distributed power generation capacity, and the formula for selecting the grid-connected voltage level is as follows,

In the above formula,

-The weighted average of the main transformer capacity with voltage "i" kV in the area where the distributed power generation is located;

i-voltage level, generally can take 380V, 10kV, 35kV, etc.;

N _T - a constant greater than 1;

C _DER - the installed capacity of the distributed power generation;

- a value when When the value is 1, otherwise it is 0;

V _DERi - The initial selection flag of the distributed power access voltage level. When its value is 1, it means that it can be integrated into the power grid with a voltage of "i" kV. Generally, two voltage levels are sufficient.

4) Determine the access mode of the distributed power supply, wherein, the determination formula of the access mode of the distributed power supply is,

In the above formula,

C _L - the transmission capacity of the grid-connected line;

N _l - a constant greater than 1;

F _DER - the access method of distributed power generation, its value is 1, which means that non-dedicated line access is available, and its value is 0, which means that dedicated line access is used.

5) Determine the access point of the distributed power supply, wherein the determination steps of the access point of the distributed power supply are as follows,

If F _DER = 0, select the main transformer in the voltage level corresponding to the V _DERi flag, perform a weight calculation according to the formula (d), and then sort it, and take the one corresponding to the smallest value among the values D _ij is not zero The "i" kV voltage level side of the main transformer is used as the access point of the distributed power supply;

In the above formula,

m _maxij - the number of outgoing line intervals where the voltage of the j-th main transformer is "i"kV;

m _ij - The voltage of the jth main transformer at present is the number of outgoing lines in the "i" kV outgoing line interval;

n _ij - the number of distributed power sources connected to the kV side of the status quo where the voltage of the jth main transformer is "i";

C _DERk - The voltage of the jth main transformer at present is the installed capacity of the kth distributed power supply on the "i" kV side;

d _ij - the voltage from the distributed power supply to the jth main transformer is the distance from the grid-connected power line on the kV side of "i";

d _i - the upper limit of the reasonable power supply distance stipulated by the power supply company for the voltage level of "i"kV;

If F _DER = 1, then the distributed power supply is connected to a line with a voltage of "i" kV nearby;

If V _DERi = 1, but the "i" kV power grid does not meet the conditions determined in the above steps, it is necessary to transfer to the previous voltage level network of the "i" kV power grid and follow the above steps again to determine the grid connection point and access mode Select until the appropriate grid connection point and access method are determined; T _ij - the area where the distributed power supply is located has the capacity of the jth main transformer with a voltage of "i" kV voltage level.

The above description is only a preferred embodiment of the present invention. It should be pointed out that for those of ordinary skill in the art, without departing from the principle of the present invention, some improvements can also be made, and these improvements should also be regarded as the present invention. protection scope of the invention.

Claims (5)

1. A distributed power supply grid-connected point and access mode selection method is characterized by comprising the following steps:

1) determining the power generation characteristics of a distributed power supply needing grid connection;

2) the method comprises the steps of knowing the power grid condition of a region where a distributed power supply is located, counting the capacity and load of a single main transformer of each voltage level public substation, and calculating the weighted average value of the capacities of the main transformers of each voltage level;

3) preliminarily selecting a grid-connected voltage grade according to the power generation capacity of the distributed power supply;

4) determining an access mode of a distributed power supply;

5) determining access points for distributed power sources

The calculation formula for calculating the weighted average value of the main transformer capacity of each voltage class in the step 2) is as follows:

${\stackrel{\‾}{T}}_i=\frac{\underset{j=1}{\overset{ni}{\Σ}}{T}_{ij}\×if\left(\right(L_{ij}-L)>0)}{\underset{j=1}{\overset{ni}{\Σ}}if\left(\right(L_{ij}-L)>0)}---\left(a\right)$

wherein,

-the weighted average of the main transformer capacity with voltage of "i" kV accessible in the area where the distributed power supply is located;

i-voltage level;

ni-the number of main transformers with voltage of i kV in the area where the distributed power supply is located;

T_ij-the area where the distributed power supply is located has the capacity of the jth main transformer with a voltage of "i" kV class;

L_ij-the area of the distributed power supply has the load of the jth main transformer with voltage of "i" kV class

Rate; the L-constant is a threshold value of the load rate of the main transformer and can be selected according to the condition of the power grid;

if((L_ij－L)>0) -judging the weight, which is (L)_ij－L)>The value of 0 is 1, otherwise the value is 0.

2. The distributed power grid-connected point and access method selection method according to claim 1, wherein: the distributed power supply in the step 1) comprises a synchronous motor, an asynchronous motor and an inverter type distributed power supply.

3. The distributed power grid-connected point and access method selection method according to claim 1, wherein: the formula of the grid-connected voltage grade selected in the step 3) is as follows,

$V_{DERi}=if(C_{DER}<\frac{{\stackrel{\&OverBar;}{T}}_i}{N_T})---\left(b\right)$

wherein, on

In the formula,

-the voltage in the area of the distributed power supply is a weighted average of the main transformer capacity of "i" kV;

i-voltage level;

N_T-a constant greater than 1;

C_DER-installed capacity of the distributed power supply;

a value of whenThe value is 1, otherwise, the value is 0;

V_DERia preliminary selected flag bit for the class of the distributed power supply access voltage, whose value is 1, indicating that the incorporable voltage is

The power grid of the 'i' kV can be obtained by taking two voltage grades.

4. The distributed power grid-connected point and access method selection method according to claim 1, wherein: the determination formula of the access mode of the distributed power supply in the step 4) is as follows,

$F_{DER}=if(C_{DER}<\frac{C_L}{N_l})---\left(c\right)$

wherein,

C_L-transmission capacity of the grid-tied line;

N_l-a constant greater than 1;

F_DERthe access mode of the distributed power supply is represented by a value of 1, which indicates that non-dedicated access is adopted, and a value of 0, which indicates that dedicated access is adopted.

5. The distributed power grid-connected point and access method selection method according to claim 1, wherein: the determination step of the access point of the distributed power source in step 5) is as follows,

if F_DERWhen is equal to 0, select V_DERiCalculating a weight value of the main transformer in the voltage class corresponding to the zone bit according to a formula (D), then sorting, and taking D_ijThe i kV voltage level side of a main transformer corresponding to the minimum value in the non-zero numerical values is used as an access point of the distributed power supply;

$D_{ij}=if(m_{ij}<m_{\max ij})(\frac{C_{DER}+\underset{k=1}{\overset{nij}{\&Sigma;}}{C}_{DERk}}{T_{ij}}+\frac{d_{ij}}{d_i})---\left(d\right)$

wherein,

m_maxij-the voltage of the j-th main transformer is now the number of "i" kV outgoing line intervals;

m_ij-the voltage of the j-th main transformer is now the number of outgoing lines in the "i" kV outgoing line interval;

n_ij-the voltage of the j-th main transformer is now the number of "i" kV side access distributed power supplies;

C_DERkthe voltage of the jth main transformer is the installed capacity of the kth distributed power supply on the 'i' kV side;

d_ijthe voltage of the distributed power supply to the jth main transformer is the distance of the grid-connected power line at the side of 'i' kV;

d_i-an upper limit of a prescribed reasonable supply distance for the power supply enterprise at a voltage level of "i" kV;

T_ij-the area where the distributed power supply is located has the capacity of the jth main transformer with a voltage of "i" kV class;

C_DER-installed capacity of the distributed power supply;

a value of whenThe value is 1, otherwise, the value is 0;

if F_DERWhen the voltage of the distributed power supply is 1, the distributed power supply is connected to a line with the voltage of i kV nearby; if although V_DERiIf the i-kV power grid does not meet the determined conditions, the previous voltage class network of the i-kV power grid needs to be switched to for selecting a grid connection point and an access mode until a proper grid connection point and an access mode are determined.