A distributed photovoltaic control method considering voltage fluctuations between stations

Abstract

The present invention provides a distributed photovoltaic control method that takes into account voltage fluctuations between substations, which belongs to the field of automatic voltage control. Adjacent substations are divided by calculating the substation sensitivity matrix and the electrical relationship between substations under the same power supply path in the distribution network. A collaborative control strategy is calculated for adjacent substations that are highly coupled with the voltage-exceeding node substation, and voltage constraints are considered for adjacent substations that are balanced coupled with the voltage-exceeding node substation, so as to solve the problem of voltage fluctuation exceeding the limit in other adjacent substations caused by the voltage problem of regulating a certain node in the distribution network.

Description

Technical Field

[0001] The present invention belongs to the field of automatic voltage control, and in particular relates to a distributed photovoltaic control method that takes into account voltage fluctuations between stations. Background Art

[0002] Distributed generation (DG) technology generally refers to small-scale power generation devices based primarily on new and renewable energy sources, deployed close to the load. These include micro-gas turbines with capacities ranging from tens to hundreds of kW, fuel cells, solar photovoltaic technology, wind power generation, and the rapidly developing superconducting energy storage technology. Distributed power sources offer the advantages of low investment, minimal footprint, short construction periods, high energy efficiency, and energy conservation and environmental protection. Because distributed power sources are located close to the load, control of distributed power sources within a substation can directly impact the voltage at the substation's grid connection point. When the substation voltage fluctuates, regulating the active and reactive power of distributed power sources can smooth out the fluctuations, improve power supply reliability, and mitigate issues such as reduced power quality caused by load and voltage fluctuations. Under traditional distribution network models, due to the limited capacity of distributed photovoltaic and other renewable energy sources, distribution network regulation does not consider distributed renewable energy sources as controllable power sources and does not integrate them into the grid dispatching system. This makes it difficult for dispatching agencies to accurately monitor the operating status and output of various distributed energy sources and regulate them.

[0003] In 2021, the National Energy Administration recently issued the "Notice on Submitting the Pilot Plan for the Development of Rooftop Distributed Photovoltaic in the Whole County (City, District)", requiring the effective guarantee of large-scale "connection" of distributed photovoltaics in the pilot areas. A total of 676 counties participated in the pilot, accounting for more than 20% of the more than 3,000 counties and cities in the country. As the proportion of distributed energy increases, its impact on the distribution network is becoming more and more significant. Although distributed power generation technology has many advantages, access to the large power grid has brought a series of impacts on power quality and power dispatching operations. With the surge in distributed photovoltaic capacity, companies in various cities and counties have begun to pay attention to the management and control of distributed photovoltaics, especially the control of reactive power. The balance and reasonable distribution of reactive power are important factors affecting voltage quality and system economy. The current control method is to monitor the voltage of the grid connection point in the substation and adjust the active and reactive power of the distributed photovoltaics in the substation in real time to achieve the purpose of qualified substation voltage. However, this approach fails to consider the mutual influence between substations. Adjacent substations may experience significant voltage deviations due to differences in distributed photovoltaic installed capacity and source-load properties. When substations are close together, adjusting the voltage in one substation can have a significant impact on adjacent substations. To achieve better distributed photovoltaic regulation, a higher level of control and more precise control methods are required to ensure that the voltage in each distributed photovoltaic substation is within the normal range. By leveraging the interactive capabilities between distribution network substations, the capacity to accommodate distributed renewable energy can be increased, thereby improving the grid compatibility of large-scale intermittent renewable energy and optimizing the primary energy structure.

[0004] In summary, driven by various current policies, the installed capacity of distributed photovoltaics has surged. Due to the random output characteristics of distributed renewable energy, the voltage fluctuations in the active distribution network are very frequent. At present, the distributed photovoltaic control system only considers the constraints of directly connected substations for voltage fluctuation control, and does not consider the impact of this control method on adjacent substations. It does not meet the current and future control needs of distributed renewable energy distribution networks with high penetration rates. Summary of the Invention

[0005] The purpose of the present invention is to solve the problem that the voltage fluctuation of other adjacent substations exceeds the limit due to the voltage problem of regulating a certain node in the distribution network, and to provide a distributed photovoltaic control method that takes into account the voltage fluctuation between substations.

[0006] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0007] A distributed photovoltaic control method considering voltage fluctuations between stations includes the following steps:

[0008] Step 1: Calculate the distribution network flow based on the full distribution network model and measurement data, collect statistics on the substation information, and form five matrices: the substation reactive upper limit, reactive lower limit, real-time reactive power, voltage upper limit, voltage lower limit, and real-time voltage;

[0009] Step 2: Based on the power flow calculation results, use the topology search method to complete the power supply path search for all substations, group the substation power supply paths by feeder, and calculate the voltage sensitivity matrix between the distribution network substation nodes under the same power supply path;

[0010] Step 3: Calculate the electrical relationship of the substations based on the voltage sensitivity matrix between substations to complete the division of adjacent substations;

[0011] Step 4: When the voltage of a node in a distribution network area exceeds the limit, calculate the voltage deviation of node i in the area and the reactive power regulation required to eliminate the voltage exceeding the limit at node i in the area, and determine whether the adjustable resources of the area exceeding the limit are sufficient. If so, jump to step 5; if not, jump to step 6.

[0012] Step 5: Calculate the voltage change at node j in the adjacent substation caused by this adjustment, taking into account the high-coupling substation and the balanced substation, and determine whether the reactive power adjustment of the substation will cause node j in the adjacent substation to exceed the limit. If yes, jump to step 4; otherwise, jump to step 8.

[0013] Step 6: If the adjustable resources in the substation are insufficient, consider the coordinated regulation of resources in highly coupled adjacent substations, sort the resources by the electrical relationship with substation i, and calculate the voltage deviation after the adjustable resources in substation i are exhausted and the reactive power regulation of node j in the highly coupled adjacent substation.

[0014] Step 7: Determine whether the adjustable resources of node j in the highly coupled adjacent substation are sufficient. If so, jump to step 5. If not, jump to step 6 and continue to coordinate the adjustment based on the electrical relationship of the adjacent substations.

[0015] Step 8: The coordinated adjustment of the substations is completed and the substation adjustment instructions are issued.

[0016] Furthermore, the five matrices of the upper reactive power limit, lower reactive power limit, real-time reactive power, upper voltage limit, lower voltage limit, and real-time voltage in the substation area in step 1 are characterized by:

[0017] The upper limit of the adjustable reactive power in the substation is

[0018] The lower limit of adjustable reactive power in the substation is

[0019] The real-time reactive power of the substation is Q = [Q1, Q2, ..., Q n ];

[0020] The upper limit of the area voltage is

[0021] The lower limit of the station voltage is

[0022] The real-time voltage of the substation is U=[U1,U2,...,Un ].

[0023] Furthermore, the voltage sensitivity matrix is:

[0024]

[0025] Where A PV 、A QV They are the sensitivity matrix of voltage amplitude to node active power and the sensitivity matrix of voltage amplitude to node reactive power, which represent the influence of active and reactive power injected by the substation node on the voltage of other nodes. PV 、E QV They represent the sensitivity matrices of active and reactive injection of nodes in different substations to the voltage amplitude of other substations.

[0026] Furthermore, the electrical relationship is:

[0027]

[0028] Where: e ij Represents the electrical relationship between node i and node j, They respectively represent the sensitivity of node i voltage to node j active power, node j voltage to node i active power, node i voltage to node j reactive power, and node j voltage to node i reactive power. The greater the sensitivity between the two nodes, the closer the connection, and the greater the electrical relationship value based on active and reactive voltage sensitivity.

[0029] Furthermore, the voltage deviation of node i in the substation is:

[0030]

[0031] Where U i is the real-time voltage of node i in the substation, U i high is the voltage upper limit of node i in the substation;

[0032] The reactive power regulation required to eliminate the voltage over-limit at node i is:

[0033]

[0034] The conditions for judging whether the adjustable resources in the over-limit area are met are:

[0035]

[0036] Where Q i high It is the upper limit of adjustable reactive power of node i in the substation.

[0037] Furthermore, the voltage change of the adjacent station node j is:

[0038]

[0039] The conditions for judging whether the reactive power adjustment of the substation will cause the j node of the adjacent substation to exceed the limit are:

[0040]

[0041] Where U j is the real-time voltage of node j in the substation, U j high is the upper voltage limit of node j in the substation.

[0042] Furthermore, the voltage deviation after the adjustable resources of node i in the substation are exhausted is:

[0043]

[0044] Where Q j high is the upper limit of the adjustable reactive power of node j in the substation, is the increment of node voltage phase angle and amplitude;

[0045] The reactive regulation of node j in the highly coupled adjacent substation is:

[0046]

[0047] Furthermore, the conditions for determining whether the adjustable resources of node j in the highly coupled adjacent area meet the following criteria:

[0048]

[0049] The embodiments of the present invention bring the following beneficial effects:

[0050] The distributed photovoltaic control method designed by the present invention takes into account the voltage fluctuation between substations. When the voltage of the distribution network exceeds the limit due to the fluctuation of the output of distributed new energy, the adjacent substations are divided by calculating the substation sensitivity matrix and the electrical relationship between substations under the same power supply path in the distribution network. The collaborative control strategy is calculated for the adjacent substations that are highly coupled with the voltage-exceeding node substation, and the voltage constraint conditions are considered for the adjacent substations that are balanced coupled with the voltage-exceeding node substation, so as to solve the problem of voltage fluctuation exceeding the limit in other adjacent substations caused by the voltage problem of regulating a certain node in the distribution network.

[0051] Other features and advantages of the present invention will be described in the following description, and in part will become apparent from the description, or understood by practicing the present invention. The purposes and other advantages of the present invention are realized and obtained by the structures particularly pointed out in the description, claims and drawings.

[0052] In order to make the above-mentioned objects, features and advantages of the present invention more obvious and easy to understand, preferred embodiments are given below and described in detail with reference to the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] Figure 1 This is a flow chart of a distributed photovoltaic control method considering voltage fluctuations between stations provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0054] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0055] like Figure 1 As shown, an embodiment of the present invention provides a distributed photovoltaic control method considering voltage fluctuations between stations, including the following steps:

[0056] Step 1: First, calculate the distribution network flow based on the full distribution network model and measurement data, collect the substation information, and form five matrices: substation reactive upper limit, reactive lower limit, real-time reactive power, voltage upper limit, voltage lower limit, and real-time voltage.

[0057] Adjustable reactive power upper limit of the substation

[0058] Adjustable reactive power lower limit in the substation

[0059] The real-time reactive power of the area Q=[Q1,Q2,...,Q n ];

[0060] Substation voltage upper limit

[0061] Substation voltage lower limit

[0062] The real-time voltage of the substation is U=[U1, U2, ..., U n ];

[0063] Step 2: Using the substation as the starting point and the 10kV switch of the distribution network feeder as the end point, use the topology search method based on the power flow calculation results to complete the power supply path search for all substations and group the substation power supply paths by feeder.

[0064] Path f 1=[tg1,tg2,t g3 ,.....tgn ]

[0065] Path f 2=[tg6,tg7,tg8,....tg n ]

[0066] Step 3: Calculate the voltage sensitivity matrix between nodes in the distribution network under the same power supply path;

[0067]

[0068]

[0069] Where: and is the net active load and reactive load of node j in the distribution network area; and is the distributed photovoltaic active power and reactive power of node j in the distribution network area; and is the active load and reactive load of node j in the distribution network area;

[0070] Calculated sensitivity

[0071]

[0072] Where: Indicates the increment of active and reactive power injected into the node; Represents the increment of node voltage phase angle and amplitude; H, N, M, L are the elements in the Jacobian matrix;

[0073] Transform it to get:

[0074]

[0075]

[0076] Where: A PV 、A QV They are the sensitivity matrix of voltage amplitude to node active power and the sensitivity matrix of voltage amplitude to node reactive power, respectively, which represent the influence of active and reactive power injected by the substation node on the voltage of other nodes;

[0077] According to the above calculation process, the active and reactive sensitivity matrix of the node voltage in the same power supply path to the nodes in different areas is completed.

[0078]

[0079] Where E PV 、E QVThey represent the sensitivity matrices of active and reactive injection of nodes in different substations to the voltage amplitude of other substations.

[0080] Step 4: Calculate the electrical relationship of the substations based on the voltage sensitivity matrix between substations and complete the division of adjacent substations. The division criteria are as follows:

[0081]

[0082] Calculate electrical relationships:

[0083]

[0084] Where: e ij Represents the electrical relationship between node i and node j, The values ​​represent the sensitivity of node i voltage to node j's active power, node j voltage to node i's active power, node i voltage to node j's reactive power, and node j voltage to node i's reactive power, respectively. The greater the sensitivity between two nodes, the closer the connection, and the greater the electrical relationship value based on active and reactive voltage sensitivities. Substations within the same power supply path are divided according to the "Adjacent Substation Division Standard" to prepare for the next strategy.

[0085] Step 5: When the voltage of a node in a distribution network exceeds the limit, different strategies are formulated for adjacent nodes with different electrical relationships. For example, if node i in node i exceeds the limit, the voltage deviation is first calculated:

[0086]

[0087] Step 6: Calculate the reactive power regulation required to eliminate the voltage over-limit at node i:

[0088]

[0089] Step 7: Determine whether the adjustable resources in the over-limit area are sufficient. If they are, continue the execution. If not, jump to Step 10

[0090]

[0091] Step 8: Calculate the voltage change of the adjacent node j caused by this adjustment, considering the high coupling zone and the balanced zone:

[0092]

[0093] Step 9: Determine whether adjusting the reactive power of the substation will cause the j node in the adjacent substation to exceed the limit. If yes, jump to Step 5; if no, jump to Step 13 and issue a control instruction.

[0094]

[0095] Step 10: When the adjustable resources of the substation are insufficient, consider the coordinated adjustment of the resources of the highly coupled adjacent substations and call resources in order of their electrical relationship with substation i. For example, if substation j is ranked first, calculate the voltage deviation after the adjustable resources of substation i are exhausted:

[0096]

[0097] Step 11: Calculate the reactive regulation of node j in the highly coupled adjacent substation:

[0098]

[0099] Step 12: Determine whether the adjustable resources of the j-node in the highly coupled adjacent substation area are sufficient. If so, jump to Step 8. If not, jump to Step 10 and continue to coordinate the adjustment based on the electrical relationship of the j-node in the adjacent substation area.

[0100]

[0101] Step 13: The coordinated adjustment of the substations is completed and the substation adjustment instructions are issued.

[0102] It should be noted that, in this article, the terms "comprises", "includes" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or apparatus that includes a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements that are inherent to such process, method, article or apparatus.

[0103] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A distributed photovoltaic control method considering voltage fluctuations between stations, characterized in that: The following steps are included: Step 1: Calculate the distribution network flow based on the full distribution network model and measurement data, collect statistics on the substation information, and form five matrices: the substation reactive upper limit, reactive lower limit, real-time reactive power, voltage upper limit, voltage lower limit, and real-time voltage; Step 2: Based on the power flow calculation results, use the topology search method to complete the power supply path search for all substations, group the substation power supply paths by feeder, and calculate the voltage sensitivity matrix between the distribution network substation nodes under the same power supply path; Step 3: Calculate the electrical relationship of the substations based on the voltage sensitivity matrix between substations to complete the division of adjacent substations; Step 4: When the voltage of a node in a distribution network area exceeds the limit, calculate the voltage deviation of node i in the area and the reactive power regulation required to eliminate the voltage exceeding the limit at node i in the area, and determine whether the adjustable resources of the area exceeding the limit are sufficient. If so, jump to step 5; if not, jump to step 6. Step 5: Calculate the voltage change at node j in the adjacent substation caused by this adjustment, taking into account the high-coupling substation and the balanced substation, and determine whether the reactive power adjustment of the substation will cause node j in the adjacent substation to exceed the limit. If yes, jump to step 4; otherwise, jump to step 8. Step 6: If the adjustable resources in the substation are insufficient, consider the coordinated regulation of resources in highly coupled adjacent substations, sort the resources by the electrical relationship with substation i, and calculate the voltage deviation after the adjustable resources in substation i are exhausted and the reactive power regulation of node j in the highly coupled adjacent substation. Step 7: Determine whether the adjustable resources of node j in the highly coupled adjacent substation are sufficient. If so, jump to step 5. If not, jump to step 6 and continue to coordinate the adjustment based on the electrical relationship of the adjacent substations. Step 8: After the coordinated adjustment of the substation area is completed, the substation area adjustment instruction is issued; The electrical relationship in step 3 is: Where: e ij Represents the electrical relationship between node i and node j, They respectively represent the sensitivity of node i voltage to node j active power, node j voltage to node i active power, node i voltage to node j reactive power, and node j voltage to node i reactive power. The greater the sensitivity between the two nodes, the closer the connection, and the greater the electrical relationship value based on active and reactive voltage sensitivity.

2. The distributed photovoltaic control method according to claim 1, wherein the five matrices of the upper reactive power limit, lower reactive power limit, real-time reactive power, upper voltage limit, lower voltage limit, and real-time voltage in step 1 are characterized in that: The upper limit of the adjustable reactive power in the substation is The lower limit of adjustable reactive power in the substation is The real-time reactive power of the substation is Q = [Q1, Q2, ..., Q n ]; The upper limit of the area voltage is The lower limit of the station voltage is The real-time voltage of the substation is U=[U1,U2,...,U n ].

3. The distributed photovoltaic control method according to claim 1, wherein the step 2 of calculating the voltage sensitivity matrix between nodes in the distribution network area under the same power supply path is characterized in that: The voltage sensitivity matrix is: Where A PV 、A QV They are the sensitivity matrix of voltage amplitude to node active power and the sensitivity matrix of voltage amplitude to node reactive power, which represent the influence of active and reactive power injected by the substation node on the voltage of other nodes. PV 、E QV They represent the sensitivity matrices of active and reactive injection of nodes in different substations to the voltage amplitude of other substations.

4. The distributed photovoltaic control method according to claim 1, wherein the step 4 calculates the voltage deviation of the node i in the station area and the reactive power regulation required to eliminate the voltage exceeding the limit of the node i in the station area, and determines whether the adjustable resources of the exceeding station area are sufficient, characterized in that: The voltage deviation of node i in the substation is: Where U i is the real-time voltage of node i in the substation, U i high is the voltage upper limit of node i in the substation; The reactive power regulation required to eliminate the voltage over-limit at node i is: The conditions for judging whether the adjustable resources in the over-limit area are met are: Where Q i high It is the upper limit of adjustable reactive power of node i in the substation.

5. The distributed photovoltaic control method according to claim 1, wherein the step 5 calculates the voltage change of the node j in the adjacent area caused by the current adjustment, and determines whether the reactive power of the adjacent area will exceed the limit after the adjustment is made, characterized in that: The voltage change of node j in the adjacent station is: The conditions for judging whether the reactive power adjustment of the substation will cause the j node of the adjacent substation to exceed the limit are: Where U j is the real-time voltage of node j in the substation, U j high is the upper voltage limit of node j in the substation.

6. The distributed photovoltaic control method according to claim 1, wherein the step 6 of calculating the voltage deviation after the adjustable resources of the i-th node in the substation are exhausted and the reactive power regulation of the j-th node in the adjacent substation with high coupling is characterized by: The voltage deviation after the adjustable resources of node i in the substation are exhausted is: Where Q j high is the upper limit of the adjustable reactive power of node j in the substation, is the increment of node voltage phase angle and amplitude; The reactive regulation of node j in the highly coupled adjacent substation is:

7. The distributed photovoltaic control method according to claim 1, wherein the step 7 of determining whether the adjustable resources of the j-node in the high-coupling adjacent station area are satisfied is characterized in that: The conditions for determining whether the adjustable resources of node j in a highly coupled adjacent area are satisfied are:

Images