Distribution area distributed photovoltaic optimization access method considering reverse power flow and voltage deviation constraint

Abstract

The invention relates to a transformer area distributed photovoltaic optimization access method considering reverse power flow and voltage deviation constraints. The method comprises the following steps: step 1, collecting transformer area data; step 2, based on the transformer area data collected in the step 1, drawing an equivalent network of a complete loop from the first section to the tail end of the transformer area; 3, initially setting a distributed photovoltaic access position and capacity; 4, checking a reverse load rate based on the initially set position and capacity of distributed photovoltaic access in the step 3; 5, checking the voltage of each node based on the initially set position and capacity of distributed photovoltaic access in the step 3; and step 6, outputting the position and the capacity of photovoltaic access. According to the method, the distributed photovoltaic can be guided to access the power grid in order, and the method is of great significance to locating and sizing of the distributed photovoltaic.

Description

Technical Field

[0001] The present invention belongs to the technical field of optimized access of distributed renewable energy, and relates to a method for optimized access of distributed photovoltaic power generation in a substation, and in particular to a method for optimized access of distributed photovoltaic power generation in a substation taking into account reverse power flow and voltage deviation constraints. Background Art

[0002] Distributed photovoltaics are developing rapidly, and the industry is entering a period of rapid development. The amount of access in the substation area is increasing. In 2023, 96.2866 million kilowatts of distributed photovoltaics will be connected, and by the end of 2023, a total of 254.438 million kilowatts of distributed photovoltaics will be connected.

[0003] The access of distributed photovoltaic to low-voltage distribution network will significantly change the power flow distribution of the power grid in the substation area, and even change the power flow direction of the distribution network. This change in power flow affects the steady-state voltage distribution of the distribution network, which may cause high voltage or more serious long-term overvoltage at some nodes of the distribution network. In the large-scale access of distributed photovoltaic to the substation area, there are problems of overvoltage and low voltage to varying degrees, which are manifested as excessively high voltage during photovoltaic power generation and too low voltage during peak power consumption periods. The range of voltage fluctuation has exceeded -10% to +7%, threatening the safe operation of power grid equipment and affecting the normal power consumption of users.

[0004] At present, when conducting distributed photovoltaic access management, it is usually carried out in accordance with no more than 80% of the rated capacity of the equipment, and insufficient consideration is given to the reverse load rate and voltage deviation.

[0005] Therefore, the present invention proposes a distributed photovoltaic optimization access method in a substation considering reverse power flow and voltage deviation constraints, which can solve the above problems.

[0006] After searching, no public documents of the prior art identical or similar to the present invention were found. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a method for optimizing the access of distributed photovoltaic power stations in substations taking into account the constraints of reverse power flow and voltage deviation. The method fully considers the influence of the access of distributed photovoltaic power stations in substations on the two factors of reverse power flow and voltage deviation. The method finally calculates the location and capacity of distributed photovoltaic power stations through data collection, topological equivalence, setting the location and capacity of distributed photovoltaic power stations, reverse load rate verification, node voltage verification, and iterative calculation.

[0008] The present invention solves the practical problem by adopting the following technical solutions:

[0009] A distributed photovoltaic optimization access method in a substation considering reverse power flow and voltage deviation constraints comprises the following steps:

[0010] Step 1: Collect area data;

[0011] Step 2: Based on the area data collected in step 1, draw an equivalent network of a complete loop from the beginning to the end of the area;

[0012] Step 3: Initially set the location and capacity of distributed photovoltaic access;

[0013] Step 4: Based on the location and capacity of the distributed photovoltaic access initially set in step 3, check the reverse load rate;

[0014] Step 5: Based on the initial setting of the location and capacity of the distributed photovoltaic access in step 3, check the voltage of each node;

[0015] Step 6: Output the location and capacity of photovoltaic access.

[0016] Moreover, the specific method of step 1 is:

[0017] Collect the power supply network topology of the area;

[0018] Collect transformer parameters in the substation area, including capacity, voltage level, and impedance; line parameters, including length and impedance per unit length;

[0019] Collect area load data, including: load access capacity, load access location, and typical daily load curve;

[0020] Collect the existing PV data in the area, including: access location and access capacity;

[0021] Collect substation operation parameters, including: substation voltage operating range, load power factor, and substation minimum operating load.

[0022] Moreover, the specific method of step 2 is:

[0023] First, select the node with the farthest electrical distance from the substation as the end node;

[0024] Then, the equivalent power P of node m is calculated according to the load on the branch line, the access capacity and location of distributed photovoltaics. m ;

[0025] P m =α min ×∑P load -∑P PV

[0026] In the formula, α min Indicates the minimum load rate of the node, P load represents the sum of the capacities of all loads connected to the node, P PV Represents the sum of the capacities of all distributed photovoltaics connected to the node;

[0027] Finally, the equivalent line resistance R is calculated based on the electrical distance between nodes and the unit length impedance m ;

[0028] R m =r×l m

[0029] In the formula, r represents the line resistance per unit length, l m Indicates the length of the mth line segment;

[0030] Moreover, the specific method of step 3 is:

[0031] According to the plan or actual needs, determine the location and capacity of the distributed photovoltaic plan to be connected as the initial value for verification.

[0032] Moreover, the specific method of step 4 is:

[0033] Calculate the reverse load factor λ,

[0034] In the formula, n represents the total number of nodes, S N Indicates the rated capacity of the transformer in the substation.

[0035] If the reverse load rate is ≤80%, continue with the following steps; if the reverse load rate is >80%, return to step 3 to adjust the location and capacity of the photovoltaic access.

[0036] Moreover, the specific method of step 5 is:

[0037] Calculate the voltage deviation ΔU at each node m ;

[0038]

[0039] Where U m represents the voltage at node m, U m-1 represents the voltage of the m-1th node, U N Indicates rated voltage, U 0 represents the voltage at the head end of the substation, m represents the node number, n represents the total number of nodes, P i represents the equivalent power of node i, l i Indicates the length of the i-th line.

[0040] If the node voltage deviation is ≤ the limit, continue with the following steps; if the node voltage deviation is > the limit, return to step 3 to adjust the location and capacity of the photovoltaic access.

[0041] Advantages and beneficial effects of the present invention:

[0042] The present invention provides a distributed photovoltaic optimization access method in a substation considering the constraints of reverse power flow and voltage deviation, fully considering the influence of distributed photovoltaic access in the substation on the two factors of reverse power flow and voltage deviation, and obtaining the location and capacity of distributed photovoltaic through iterative calculation. The present invention is an important basis for carrying out distributed photovoltaic access planning, can guide the orderly access of distributed photovoltaic to the power grid, and is of great significance for the site selection and capacity determination of distributed photovoltaic. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a flow chart of the distributed photovoltaic optimization access in the substation considering the reverse power flow and voltage deviation of the present invention;

[0044] Figure 2 A schematic diagram of an equivalent network drawn for the present invention; DETAILED DESCRIPTION

[0045] The embodiments of the present invention are further described in detail below with reference to the accompanying drawings:

[0046] A distributed photovoltaic optimization access method considering reverse power flow and voltage deviation constraints, such as Figure 1 As shown, the following steps are included:

[0047] Step 1: Collect area data;

[0048] The specific method of step 1 is:

[0049] Collect the power supply network topology of the area;

[0050] Collect transformer parameters in the substation area, including capacity, voltage level, and impedance; line parameters, including length and impedance per unit length;

[0051] Collect area load data, including: load access capacity, load access location, and typical daily load curve;

[0052] Collect the existing PV data in the area, including: access location and access capacity;

[0053] Collect substation operation parameters, including: substation voltage operating range, load power factor, and substation minimum operating load.

[0054] Step 2: Based on the area data collected in step 1, draw an equivalent network of a complete loop from the beginning to the end of the area;

[0055] Draw a complete loop from the power source point (station) to the terminal, summarize and equalize the branch loads, and obtain an electrical network diagram with a total of n nodes. The simplified target structure is as follows Figure 2 shown.

[0056] The specific method of step 2 is:

[0057] First, select the node with the farthest electrical distance from the power source point (station area) as the end node;

[0058] Then, the equivalent power P of node m is calculated according to the load on the branch line, the access capacity and location of distributed photovoltaics. m ;

[0059] P m =α min ×∑P load -∑P PV

[0060] In the formula, α min Indicates the minimum load rate of the node, P load represents the sum of the capacities of all loads connected to the node, P PV Represents the sum of the capacities of all distributed photovoltaics connected to the node;

[0061] Finally, the equivalent line resistance R is calculated based on the electrical distance between nodes and the unit length impedance m ;

[0062] R m =r×l m

[0063] In the formula, r represents the line resistance per unit length, l m Indicates the length of the mth line segment;

[0064] Step 3: Initially set the location and capacity of distributed photovoltaic access;

[0065] The specific method of step 3 is:

[0066] According to the plan or actual needs, determine the location and capacity of the distributed photovoltaic plan to be connected as the initial value for verification.

[0067] Step 4: Based on the location and capacity of the distributed photovoltaic access initially set in step 3, check the reverse load rate;

[0068] The specific method of step 4 is:

[0069] Calculate the reverse load factor λ,

[0070] In the formula, n represents the total number of nodes, S N Indicates the rated capacity of the transformer in the substation.

[0071] If the reverse load rate is ≤80%, continue with the following steps; if the reverse load rate is >80%, return to step 3 to adjust the location and capacity of the photovoltaic access.

[0072] Step 5: Based on the initial setting of the location and capacity of the distributed photovoltaic access in step 3, check the voltage of each node;

[0073] The specific method of step 5 is:

[0074] Calculate the voltage deviation ΔU at each node m ,

[0075]

[0076] Where U m represents the voltage at node m, U m-1 represents the voltage of the m-1th node, U N Indicates rated voltage, U 0 represents the voltage at the head end of the substation, m represents the node number, n represents the total number of nodes, P i represents the equivalent power of node i, l i Indicates the length of the i-th line.

[0077] If the node voltage deviation is ≤ the limit, continue with the following steps; if the node voltage deviation is > the limit, return to step 3 to adjust the location and capacity of the photovoltaic access.

[0078] Step 6: Output the location and capacity of photovoltaic access;

[0079] The current location and capacity of photovoltaic access are output as results.

[0080] The working principle of the present invention is:

[0081] Step 1: Collect the power supply network topology of the substation; collect the transformer parameters (capacity, voltage level, impedance, etc.) and line parameters (length, impedance per unit length) of the substation; collect the load data of the substation (load access capacity, load access location, typical daily load curve); collect the existing photovoltaic data of the substation (access location and access capacity); collect the operating parameters of the substation (voltage operating range of the substation, load power factor, minimum operating load of the substation).

[0082] Step 2: Draw a complete loop from the power source point (station) to the terminal, summarize and equalize the branch loads, and obtain an electrical network diagram with a total of n nodes. The simplified target structure is as follows: Figure 1 shown.

[0083] Step 3: According to the plan or actual needs, determine the location and capacity of the distributed photovoltaic plan to be connected as the initial value for verification.

[0084] Step 4: Calculate the reverse load rate. If the reverse load rate is ≤80%, continue with the following steps; if the reverse load rate is >80%, return to step 3 to adjust the total capacity of the photovoltaic access.

[0085] Step 5: Calculate the voltage deviation of each node. If the node voltage deviation is less than or equal to the limit, continue with the following steps; if the node voltage deviation is greater than the limit, return to step 3 to adjust the location and capacity of the photovoltaic access.

[0086] Step 6: Output the current location and capacity of photovoltaic access as the result.

[0087] It should be emphasized that the embodiments of the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation modes. Any other implementation modes derived by those skilled in the art based on the technical solutions of the present invention also fall within the scope of protection of the present invention.

Claims

1. A distributed photovoltaic optimization access method in a substation considering reverse power flow and voltage deviation constraints, characterized by: The following steps are involved: Step 1: Collect area data; Step 2: Based on the area data collected in step 1, draw an equivalent network of a complete loop from the beginning to the end of the area; Step 3: Initially set the location and capacity of distributed photovoltaic access; Step 4: Based on the location and capacity of the distributed photovoltaic access initially set in step 3, check the reverse load rate; Step 5: Based on the initial setting of the location and capacity of the distributed photovoltaic access in step 3, check the voltage of each node; Step 6: Output the location and capacity of photovoltaic access.

2. According to claim 1, a distributed photovoltaic optimization access method in a substation considering reverse power flow and voltage deviation constraints is characterized by: The specific method of step 1 is: Collect the power supply network topology of the area; Collect transformer parameters in the substation area, including capacity, voltage level, and impedance; line parameters, including length and impedance per unit length; Collect area load data, including: load access capacity, load access location, and typical daily load curve; Collect the existing PV data in the area, including: access location and access capacity; Collect substation operation parameters, including: substation voltage operating range, load power factor, and substation minimum operating load.

3. According to claim 1, a distributed photovoltaic optimization access method in a substation considering reverse power flow and voltage deviation constraints is characterized by: The specific method of step 2 is: First, select the node with the farthest electrical distance from the substation as the end node; Then, the equivalent power P of node m is calculated according to the load on the branch line, the access capacity and location of distributed photovoltaics. m ; P m =a min ×∑P load -∑P PV In the formula, α min Indicates the minimum load rate of the node, P load represents the sum of the capacities of all loads connected to the node, P PV Represents the sum of the capacities of all distributed photovoltaics connected to the node; Finally, the equivalent line resistance R is calculated based on the electrical distance between nodes and the unit length impedance m ; R m ＝r×l m In the formula, r represents the line resistance per unit length, l m Indicates the length of the mth line segment.

4. According to claim 1, a distributed photovoltaic optimization access method in a substation considering reverse power flow and voltage deviation constraints is characterized by: The specific method of step 3 is: According to the plan or actual needs, determine the location and capacity of the distributed photovoltaic plan to be connected as the initial value for verification.

5. According to claim 1, a distributed photovoltaic optimization access method in a substation considering reverse power flow and voltage deviation constraints is characterized by: The specific method of step 4 is: Calculate the reverse load factor λ, In the formula, n represents the total number of nodes, S N Indicates the rated capacity of the transformer in the substation area; If the reverse load rate is ≤80%, continue with the following steps; if the reverse load rate is >80%, return to step 3 to adjust the location and capacity of the photovoltaic access.

6. The method for optimizing access to distributed photovoltaic power stations in a substation considering reverse power flow and voltage deviation constraints according to claim 1, characterized in that: The specific method of step 5 is: Calculate the voltage deviation ΔU at each node m ; Where U m represents the voltage at node m, U m-1 represents the voltage of the m-1th node, U N represents the rated voltage, U0 represents the voltage at the head end of the substation, m represents the node number, n represents the total number of nodes, P i represents the equivalent power of node i, l i represents the length of the i-th line; If the node voltage deviation is ≤ the limit, continue with the following steps; if the node voltage deviation is > the limit, return to step 3 to adjust the location and capacity of the photovoltaic access.

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