Voltage regulation and control method for medium and low voltage distribution network and computer equipment

Abstract

The invention belongs to the field of power distribution network node voltage regulation and control, and particularly relates to a voltage regulation and control method of a medium and low voltage power distribution network and computer equipment. The method comprises the steps of judging whether reactive resources of the power distribution network are deficient or not when node voltages of the medium-voltage and low-voltage power distribution networks are out of limit; if the reactive resources are deficient, determining a voltage regulation and control strategy and performing regulation and control by taking the maximum system voltage quality score determined according to the weight of each power supply area of the power distribution network and the voltage deviation condition of each regulated and controlled power supply area as an objective function; the higher the priority of the power supply area is, the larger the weight is; if the reactive power resources are sufficient, taking the node with the maximum voltage offset as an analysis node, and taking the minimum total voltage offset of each node of the power distribution network system as an objective function; and determining a voltage regulation and control strategy meeting the corresponding constraint condition, and regulating and controlling the regulation and control equipment selected for analyzing the voltage sensitivity of the nodes in combination with the active power and the reactive power injected according to the nodes until the voltage of the nodes returns to normal.

Description

Technical Field

[0001] The present invention belongs to the field of voltage regulation of distribution network nodes, and in particular relates to a voltage regulation method and computer equipment for medium and low voltage distribution networks. Background Art

[0002] As the terminal part of the power grid, the distribution network is an important link between the power grid and users. The medium and low voltage distribution network is the key intermediate link to ensure that electricity can be "landed and used". As the last distribution and transformation link that directly supplies power to users, the quality of the voltage of the low voltage substation is directly related to the power supply efficiency of the power grid and the power consumption experience of users. With the rapid development of my country's economy, the scale of the distribution network has gradually expanded, and the technical level of distributed power sources has also continued to mature. Distributed power sources have the advantages of low cost, simple regulation, and environmental protection. In order to improve the utilization rate of clean energy, the power system allows and encourages a large number of photovoltaic systems (PV) to be connected to the distribution network, and its operation has also changed from passive to active. However, the power distribution and voltage quality in the distribution network are related to whether the distribution network can operate safely and stably. Therefore, it is necessary to coordinate the traditional reactive voltage control equipment with controllable PV, load, energy storage, etc. to achieve the optimal power flow distribution. More proactively deal with the voltage problems caused by PV grid connection, reduce the impact of PV randomness and volatility, and reduce the network loss of the distribution network.

[0003] In a distribution network with a high penetration rate of distributed power sources, traditional control methods can no longer cope with the challenges brought by the grid connection of distributed power sources. The high penetration rate of distributed power sources will bring the following challenges:

[0004] 1) The photovoltaic grid-connected power causes the traditional unidirectional power flow to be transformed into a bidirectional power flow, which increases the system loss and causes the node voltage to rise in reverse;

[0005] 2) The decentralization of distributed power sources makes the reactive power and voltage distribution of the system more complex, and traditional passive regulation cannot cope with it;

[0006] 3) The randomness and volatility of photovoltaic power brings uncertainty to the operation of distribution networks.

[0007] Therefore, low-voltage distribution networks with a high proportion of household photovoltaics will face serious risks of voltage over-limit, voltage imbalance and power fluctuation. In addition, the reverse flow generated in the low-voltage distribution network will also feed power into the medium-voltage distribution network through the nodes of the medium- and low-voltage distribution networks, causing voltage problems in the medium-voltage distribution network.

[0008] Usually, the reactive voltage regulation of distribution network is to change the reactive power distribution mode in distribution network by using transformer on-load tap changer combined with traditional reactive compensation device to adjust the voltage of grid user node. In the distribution network with high penetration rate of photovoltaic power generation, photovoltaic system is usually used to provide compensation to distribution network through photovoltaic active output; however, the ability of photovoltaic system to provide compensation to distribution network is limited, and the overall reactive voltage regulation effect is affected by the properties of each node of distribution network and actual working conditions, so it is difficult to guarantee the regulation effect, resulting in poor reliability of reactive voltage regulation result. Summary of the invention

[0009] The purpose of the present invention is to provide a voltage control method and computer equipment for medium and low voltage distribution networks, which are used to solve the problem that the reactive voltage control effect of the distribution network with high penetration rate photovoltaic power generation in the prior art is affected by the properties of each node of the distribution network and the actual working conditions, making it difficult to ensure the compensation effect, resulting in poor reliability of the reactive voltage control result.

[0010] In order to achieve the above object, the present invention provides a voltage control method for a medium and low voltage distribution network. If the node voltage of the medium and low voltage distribution network exceeds the limit, then:

[0011] 1) Determining whether the reactive power resources of the distribution network are scarce;

[0012] 2) If it is determined that reactive resources are scarce, the voltage regulation strategy is determined and regulated by taking the maximum system voltage quality score determined according to the weight of each power supply area of ​​the distribution network and the voltage deviation of each power supply area after regulation as the objective function; the higher the priority of the power supply area, the greater the weight;

[0013] Otherwise, it is determined that the reactive resources are sufficient, and the node with the largest voltage offset is taken as the analysis node. The minimum total voltage offset of each node in the distribution network system is taken as the objective function, and the voltage control strategy that meets the corresponding constraints is determined. The control device selected according to the voltage sensitivity of the analysis node to the active and reactive power injected by each node is used to perform control according to the voltage control strategy until the voltage of each node returns to normal.

[0014] Furthermore, when reactive power resources are sufficient, if the voltage of each node returns to normal after step 2), the voltage control further includes the following steps:

[0015] Eliminate the devices that have participated in the regulation in step 2) when the reactive resources are sufficient, and for the nodes corresponding to the remaining regulation devices, take the minimum network loss of the distribution network system as the objective function, determine the voltage regulation strategy that meets the corresponding constraints, and combine the network loss sensitivity of the system network loss corresponding to each node to the node injected active and reactive power to regulate the regulation devices until the change of the system network loss after regulation is less than the corresponding set threshold.

[0016] Furthermore, if the node voltages of the medium and low voltage distribution networks do not exceed the limit, then:

[0017] Taking the minimum network loss of the distribution network as the objective function, the voltage control strategy that meets the corresponding constraints is determined, and the control equipment selected according to the network loss sensitivity of the active and reactive power injected into the node according to the system network loss corresponding to each node is controlled until the change of the system network loss after control is less than the corresponding set threshold.

[0018] Further, the method of regulating the voltage sensitivity of the analysis node by the regulation device selected according to the active and reactive power injected into each node until the voltage of each node returns to normal includes:

[0019] a) According to the voltage sensitivity of the analysis node to the active and reactive power injected into each node, the control device at the node with the largest voltage sensitivity is selected;

[0020] b) Taking the minimum total voltage offset of each node as the objective function, determine the voltage control strategy that meets the corresponding constraint conditions and perform control in combination with the selected control device; if the voltage of each node does not return to normal after control, select the control device at the node with the largest voltage sensitivity other than the selected control device, and repeat step b) until the voltage of each node returns to normal;

[0021] The method for selecting the control device at the node with the largest voltage sensitivity is: if there is a node where the voltage sensitivity of both active and reactive power injected to the analysis node is the largest, then the control device at this node is selected; otherwise, if the control device at the node with the largest voltage sensitivity of reactive power to the analysis node has not been selected, then this control device is selected; if the control device at the node with the largest voltage sensitivity of reactive power to the analysis node has been selected, then the control device at the node with the largest voltage sensitivity of active power to the analysis node is selected.

[0022] Further, the method of regulating the control device selected according to the network loss sensitivity of the active and reactive power injected into the node according to the system network loss corresponding to each node until the change amount of the system network loss after regulation is less than the corresponding set threshold includes:

[0023] Determine from each node the node whose corresponding system network loss sensitivity to the active and reactive power injected by the node is negative and has the largest absolute value, and select the control device at the node;

[0024] Taking the minimum network loss of the distribution network as the objective function, determine the voltage control strategy that meets the corresponding constraints and combine it with the control equipment selected according to the network loss sensitivity of the active and reactive power injected into the node according to the system network loss corresponding to each node to perform control;

[0025] After each regulation, if the difference between the system network loss before and after this regulation is less than the set lower limit threshold, it is determined that the change in system network loss after regulation is less than the corresponding set threshold. Otherwise, the minimum network loss of the distribution network system is continued as the objective function, and the voltage regulation strategy that meets the corresponding constraints is re-determined for the next regulation.

[0026] Determine the node whose corresponding system network loss sensitivity to the active and reactive power injected into the node is negative and has the largest absolute value, and select the control device at the node as follows: if there is a node whose network loss sensitivity to the analysis node when active and reactive power are injected is negative and has the largest absolute value, then select the control device at the node; otherwise, if the control device at the node with the largest network loss sensitivity of reactive power to the analysis node has not been selected, select the control device; if the control device at the node with the negative network loss sensitivity of reactive power to the analysis node and the largest absolute value has been selected, select the control device at the node with the negative network loss sensitivity of active power to the analysis node and the largest absolute value.

[0027] Furthermore, the priority of the power supply area is determined by:

[0028] According to the weight values ​​of the evaluation indicators of the power supply area, the standardized indicator values ​​corresponding to the evaluation indicators are weighted and summed to obtain the priority evaluation value of the power supply area, which is used to determine the priority of the power supply area;

[0029] The method for determining the standardized index value corresponding to each evaluation index includes:

[0030]

[0031] In the formula, y ij is the original index value of the jth evaluation index of the ith station; z ij is the standardized index value of the jth evaluation index of the ith substation; min{} is the minimum value function, and max{} is the maximum value function.

[0032] Furthermore, the voltage sensitivity is determined by:

[0033]

[0034] In the formula, is the voltage sensitivity of node i to the active power injected into node j, where node i is the analysis node; R k is the real part of the line impedance; V k is the voltage of node k; The voltage sensitivity of node i to the reactive power injected into node j; X k is the imaginary part of the line impedance.

[0035] Furthermore, the method for determining the network loss sensitivity includes:

[0036]

[0037] In the formula, Represents the active power P of node i i Relative to the node voltage V i The rate of change, Represents the active power P of node i i Phase angle δ i The partial derivative of Represents the reactive power Q of node i i Relative to the node voltage V i The rate of change, Represents the reactive power Q of node i i Phase angle δ i The partial derivative of

[0038] in:

[0039]

[0040] In the formula, is the network loss sensitivity of the system network loss corresponding to node i to the active power injected into node i; P is the network loss sensitivity of the system network loss corresponding to node i to the reactive power injected into node i; loss is the system network loss; V i and V j are the voltages of nodes i and j respectively; G ij is the conductance between branches; δ ij is the phase angle difference between nodes; n is the total number of nodes.

[0041] Further, the corresponding constraint conditions include equality constraint conditions and inequality constraint conditions;

[0042] The equality constraints include:

[0043]

[0044] In the formula, ΔP i is the active power change at node i, ΔQ i is the reactive power change at node i; P load,i is the active power of the load at node i, Q load,i is the reactive power of the load at node i; V i and V j are the voltages of nodes i and j respectively; G ij and B ij are the conductance and susceptance between branches respectively; δ ijis the phase angle difference between nodes; P pv,i is the active power injected at node i; Q pv,i is the reactive power injected at node i; n is the total number of nodes;

[0045] The inequality constraint condition includes at least one of the constraint conditions corresponding to the constraint conditions on the upper and lower limits of the node voltage, the constraint on the transformer tap position, the constraint on the number of capacitor switching groups, the constraint on the photovoltaic output, the constraint on the inverter reactive output, the constraint on the energy storage capacity, and the constraint on the photovoltaic active power reduction;

[0046] The inequality constraint condition also includes a constraint condition corresponding to a penalty function; the penalty function f punish as follows:

[0047]

[0048] Where V i is the effective value of the voltage at the ith node, V n The rated voltage of the distribution network system; V imax is the voltage upper limit threshold corresponding to node i, V imin is the voltage lower limit threshold corresponding to node i; N is the total number of node voltages in the medium and low voltage distribution networks; the constraint condition corresponding to the penalty function is: the value of the penalty function is less than the corresponding upper limit threshold;

[0049] The objective function for minimizing the total voltage offset of each node in the distribution network system is:

[0050] F step1 =f step1 / f B1 +f punish

[0051] In the formula, F step1 is the objective function for minimizing the total voltage offset of each node in the distribution network system, f step1 is the sum of the voltage offsets of each node; f B1 is the total voltage offset of each node in the distribution network system before regulation; f punish is the penalty function;

[0052] The objective function of minimizing the network loss of the distribution network system is:

[0053] F step2 =f step2 / f B2 +f punish

[0054] In the formula, F step2 is the objective function of minimizing the network loss of the distribution network system, f step2 is the sum of active power losses of each branch of the distribution network system; fB2 The network loss of the distribution network before regulation; punish is the penalty function.

[0055] The above technical solution of the present invention provides a new voltage control method for medium and low voltage distribution networks, and its beneficial effects include:

[0056] In the case of scarce reactive resources, the interests of less influential substations are temporarily sacrificed to give priority to meeting the voltage demands of some dominant important substations, so that the voltage quality of high-priority substations can be guaranteed after regulation. In this way, the limited regulation resources can be used to minimize the losses caused by voltage exceeding the limit of distribution network nodes and maximize the overall regulation effect. In the case of sufficient reactive resources, the total voltage offset of each node in the distribution network system is minimized by regulation. At the same time, the regulation equipment selected by analyzing the voltage sensitivity of the node by combining the active and reactive power injected into each node is regulated, so that the regulation effect of the regulation strategy on the node with the largest voltage offset can be controlled, thereby controlling the overall regulation effect.

[0057] The present invention also provides a computer device, comprising a processor, wherein the processor is used to execute a computer program to implement the steps of the above-mentioned voltage control method for medium and low voltage distribution networks.

[0058] The technical solution of the computer device can achieve the same beneficial effects as the above-mentioned voltage control method for medium and low voltage distribution networks. BRIEF DESCRIPTION OF THE DRAWINGS

[0059] Figure 1 A flowchart of a voltage control method for a medium- and low-voltage distribution network in an embodiment of a voltage control method for a medium- and low-voltage distribution network of the present invention;

[0060] Figure 2 It is a structural schematic diagram of a low-voltage distribution network feeder having N nodes including a photovoltaic system in an embodiment of a voltage control method for a low-voltage distribution network of the present invention. DETAILED DESCRIPTION

[0061] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is further described in detail below with reference to the accompanying drawings and embodiments.

[0062] Voltage control method embodiment of medium and low voltage distribution network

[0063] This embodiment provides a technical solution for a voltage control method of a medium and low voltage distribution network. Figure 1 If the node voltage of the medium and low voltage distribution network exceeds the limit, the following steps are performed:

[0064] 1) Determine whether the reactive power resources of the distribution network are scarce;

[0065] 2) If it is determined that reactive resources are scarce, the voltage regulation strategy is determined and regulated by taking the maximum system voltage quality score determined according to the weights of each power supply area of ​​the medium and low voltage distribution network and the voltage deviation of each power supply area after regulation as the objective function; the higher the priority of the power supply area, the greater the weight;

[0066] Otherwise (i.e., reactive resources are not judged to be scarce), if it is determined that reactive resources are sufficient, the node with the largest voltage offset is taken as the analysis node, and the minimum total voltage offset of each node in the distribution network system is taken as the objective function. The voltage control strategy that meets the corresponding constraints is determined, and the control equipment selected according to the voltage sensitivity of the analysis node to the active and reactive power injected by each node is controlled according to the voltage control strategy until the voltage of each node returns to normal.

[0067] Therefore, it is equivalent to temporarily sacrificing the interests of less influential substations in the case of scarce reactive resources, giving priority to meeting the voltage demands of some dominant important substations, so that the voltage quality of high-priority substations can be guaranteed after regulation, thereby making use of limited regulation resources to minimize the losses caused by voltage exceeding the limit of distribution network nodes and maximize the overall regulation effect; and in the case of sufficient reactive resources, by regulating the total voltage offset of each node in the distribution network system to the minimum, and combining the active and reactive power injected into each node to select the regulation device for analyzing the voltage sensitivity of the node, it is possible to control the regulation effect of the regulation strategy on the node with the largest voltage offset, thereby controlling the overall regulation effect; on the basis of controlling the overall regulation effect better, the reliability of the reactive voltage regulation result can be improved.

[0068] The method of judging whether the reactive resources of the distribution network are scarce mainly includes: performing flow calculation according to the network topology of the distribution network, evaluating the voltage level and reactive power flow status of each node in the system, and thus judging whether the reactive resources are sufficient or scarce. Since the flow calculation of the power system is a common calculation method in the field of power systems, the method of determining the reactive resources in the current distribution network grid structure through flow calculation also belongs to the prior art, and will not be repeated here.

[0069] The calculation formula of voltage offset is:

[0070]

[0071] Among them, V control is the voltage offset, which is also used to indicate the amount of regulation required for the node voltage to return to normal; V imax 、V imin They represent the upper and lower limits of the voltage of node i respectively; the node with the largest voltage offset is taken as the analysis node. When the node with the largest voltage offset meets the limit requirements after voltage control, it means that all nodes in the system meet the limit requirements.

[0072] In the case of a shortage of reactive power resources, in step 2), the priority of the power supply area is determined by:

[0073] According to the weight values ​​of the evaluation indicators of the power supply substation, the standardized indicator values ​​corresponding to the evaluation indicators are weighted and summed to obtain the priority evaluation value of the power supply substation, which is used to determine the priority of the power supply substation;

[0074] The standardized index value corresponding to each evaluation index is determined by the following 0-1 standardized transformation:

[0075]

[0076] In the formula, y ij is the original index value of the jth evaluation index of the ith station; z ij is the standardized index value of the jth evaluation index of the ith substation; min{} is the minimum value function, and max{} is the maximum value function.

[0077] The selection of evaluation indicators for substation priority evaluation should be based on the perspective of the substation itself and the power grid department. It should not only reflect the current operating characteristics of the substation itself, but also intuitively reflect its importance to the power grid department. Therefore, in this embodiment, three first-level evaluation indicators are selected, namely: substation voltage quality indicator, substation power consumption indicator and substation load rate indicator. Next, the three first-level indicators are refined, and several second-level indicators are selected, which are used as the evaluation indicators of the power supply substation.

[0078] Specifically, the annual voltage qualification rate of the substation is selected as the secondary indicator of the voltage quality index; the annual voltage qualification rate of the substation refers to the ratio of the time when the voltage at the head end of the substation is within the qualified range in a year to the annual monitoring time, recorded as α, and the calculation formula is as follows:

[0079]

[0080] Where, T1 is the time that the substation voltage is within the qualified range, and T2 is the total annual monitoring time of the substation.

[0081] Annual electricity consumption and summer peak electricity consumption are selected as two secondary indicators under the power consumption index of the substation. Among them, the annual power consumption index of the substation refers to the total power consumption of the substation during the statistical period in one year, in kW.h. The summer peak power consumption index of the substation refers to the total power consumption of the substation corresponding to August in the same statistical year as the annual power consumption of the substation, in kW.h.

[0082] The annual load rate and the annual minimum load rate are selected as two secondary indicators under the area load rate indicator. Among them, the area annual load rate refers to the ratio of the average load of the area to the maximum load during the statistical period in units of years, recorded as β, and the calculation method is as follows:

[0083]

[0084] In the formula, It refers to the annual average load of the substation in the statistical year, P max It refers to the maximum load value that occurs in the area during the statistical year.

[0085] The annual minimum load rate refers to the ratio of the minimum load of the substation area during the statistical period to the maximum load of the substation area during the same period, which is recorded as γ and is calculated as follows:

[0086]

[0087] Where P min It refers to the minimum load of the area within a year, P max It has the same meaning as the above formula, and also refers to the maximum load value that occurs in the area during the statistical year.

[0088] The final evaluation indicators of the power supply area are shown in Table 1:

[0089] Table 1

[0090]

[0091] If it is assumed that there are m low-voltage stations in the feeder that needs voltage regulation, it can be expressed as: M = {M1, M2, ... M m}, each substation has n priority evaluation indicators, recorded as: Y = {Y1, Y2, ... Y n}; The five evaluation indicators selected above are all extremely large indicators. According to the above 0-1 standardization transformation method, the standardized matrix Z is obtained:

[0092]

[0093] When all entropy values ​​are close to 1, the traditional entropy weight method will over-amplify the gap and lead to unsatisfactory weighting results. Therefore, this embodiment adopts an improved entropy weight method to overcome the shortcomings of the traditional entropy weight method. The process of solving the weights of each evaluation index using the improved entropy weight method is as follows:

[0094] First, according to the definition of information entropy in information theory, the information entropy of a set of data, that is, the information entropy of the jth evaluation index in this embodiment, is:

[0095]

[0096] Among them, if pij =0, then

[0097] Then, according to the calculation formula of information entropy, the information entropy of each evaluation index is calculated as E1, E2, …, E n .

[0098] The calculation formulas of the evaluation indicators obtained by the improved entropy weight method used in the voltage control method of the medium and low voltage distribution network of this embodiment are as follows:

[0099]

[0100] Where W j is the weight of index j, E j is the entropy value of index j, is the average value of all entropy values ​​that are not 1; W 0j represents the initial weight of index j, W 3j Represents other weights of indicator j. Then, according to the weight values ​​of each evaluation indicator of the power supply area, the standardized indicator values ​​corresponding to each evaluation indicator are weighted and summed, and the priority evaluation value of the power supply area is obtained as follows:

[0101]

[0102] In the formula, τ i is the priority evaluation value of station i, W j is the weight of index j, z ij is the standardized index value of the jth evaluation index of the i-th station; τ i That is, it is used to determine the priority of the power supply area, according to the priority evaluation value τ of each area i The priority of the substations can be divided into 5 levels, as shown in Table 2, among which Level I substation has the highest priority and is the most important substation. The priority of substations decreases from Level I to Level V.

[0103] Table 2

[0104] <![CDATA[Priority evaluation value τ i > Area Priority >0.8 Ⅰ 0.6～0.8 Ⅱ 0.4～0.6 Ⅲ 0.2～0.4 Ⅳ <0.2 Ⅴ

[0105] The method of determining the system voltage quality score according to the weight of each power supply area of ​​the medium and low distribution network and the voltage deviation of each power supply area after regulation includes:

[0106] According to the voltage offset of each power supply substation after regulation, the voltage quality score of each power supply substation is determined respectively. The larger the voltage offset corresponding to the power supply substation, the smaller the voltage quality score of the power supply substation. According to the weight of each power supply substation in the distribution network, the voltage quality scores of each power supply substation are weighted and summed to determine the system voltage quality score.

[0107] In this embodiment, the voltage deviation of each power supply area after regulation is obtained by measuring the voltage deviation δ at the head end of each power supply area. i The specific method for determining the system voltage quality score is as follows:

[0108] When δ i When the national standard requirements are met (not exceeding ±7% of the rated voltage), the voltage quality score of the substation is f i The full score is 1 point; f i With δ i Increases and gradually decreases, δ i For every 2% increase, the voltage quality score of the substation area decreases by one level; i After it is greater than ±13%, f i is 0, which means that the voltage quality of this area has no improvement effect; as shown in Table 3:

[0109] Table 3

[0110] <![CDATA[Regulate the voltage deviation δ at the i-th end of the regulation background area i (%)]]> <![CDATA[Transformer substation voltage quality score f i > [-7,+7] 1 [-9,-7)∪(7,9] 0.7 [-11,-9)∪(9,11] 0.5 [-13,-11)∪(11,13] 0.3 <-13 or >+13 0

[0111] In order to quantify the importance of different priorities in bus voltage regulation, the weights ρ corresponding to different priorities are determined. i When the priority of the power supply area is higher, the weight is greater, as shown in Table 4:

[0112] Table 4

[0113] Area Priority <![CDATA[Occupancy weight ρ i > Ⅰ 20 Ⅱ 12 Ⅲ 8 Ⅳ 5 Ⅴ 1

[0114] According to the voltage quality scores f of all substations (a total of m) in the feeder i and the weight of the corresponding station ρ i The weighted sum can be used to obtain the system voltage quality score, which is regarded as the bus voltage regulation benefit:

[0115]

[0116] Q k When reactive power resources are scarce, the priority of the substation is considered, that is, the control resources are arranged to the substation with high priority first. k ) is taken as the objective function, and the voltage control strategy is determined and controlled to ensure that the power quality (i.e., voltage offset) of the high-priority substation is restored to normal as much as possible; after the system gradually stabilizes and the reactive resources become sufficient, the total voltage offset of the system is considered to be regulated while meeting the corresponding constraints.

[0117] In the case of sufficient reactive resources, in step 2), the voltage regulation strategy is determined by taking the minimum total voltage offset of each node of the distribution network system as the objective function, and the voltage sensitivity of the analysis node is selected according to the active and reactive power injected into each node to regulate the regulation device until the voltage of each node returns to normal. The method includes:

[0118] a) According to the voltage sensitivity of the analysis node to the active and reactive power injected into each node, the control device at the node with the largest voltage sensitivity (i.e., the node with the best voltage sensitivity) is selected;

[0119] b) Taking the minimum total voltage offset of each node as the objective function, determine the voltage control strategy that meets the corresponding constraints and perform control in combination with the selected control equipment; if the voltage of each node does not return to normal after control, select the control equipment at the node with the largest voltage sensitivity (that is, the next node, that is, the node with the second best voltage sensitivity) other than the selected control equipment, and repeat step b) until the voltage of each node returns to normal.

[0120] Specifically, the method of selecting the control device at the node with the largest voltage sensitivity is: if there is a node where the voltage sensitivity of the active and reactive power injected to the analysis node is the largest, then the control device at the node is selected; otherwise, if the control device at the node with the largest voltage sensitivity of reactive power to the analysis node has not been selected, then the control device is selected; if the control device at the node with the largest voltage sensitivity of reactive power to the analysis node has been selected, then the control device at the node with the largest voltage sensitivity of active power to the analysis node is selected; it is equivalent to first making a comprehensive selection: if there is a node, and the node has both high active and reactive sensitivities, then the device is selected. Then make an independent selection: if there is no node with both high active and reactive sensitivities, then the corresponding nodes are selected according to the sensitivities of active and reactive power. That is, first select a higher reactive sensitivity, corresponding to voltage regulation, and then select a higher active sensitivity.

[0121] Therefore, each time the control is performed, the control device with the highest voltage sensitivity to the analysis node by injecting active and reactive power relative to the node where it is located is selected from the control devices that have not participated in the control to participate in the control. This can make the best use of the control resources as much as possible on the basis of limited control resources, thereby further improving the overall control effect and further improving the reliability of the reactive voltage control results.

[0122] Among them, voltage sensitivity (VS) indicates the sensitivity of node injected active / reactive power to node voltage. Figure 2 As shown in the figure, the low-voltage distribution network feeder with N nodes including photovoltaic system is taken as an example (where PV is photovoltaic system), and the voltage of any node is V i, the voltage at the equilibrium node is V0. The line impedance is recorded as Z m =R m +jX m , the photovoltaic active power is P pv,i , the reactive power that photovoltaic can compensate is Q pv,i The load power is P load,i +jQ load,i . Then the voltage at any node is:

[0123]

[0124] Therefore, the voltage change of node i caused by the power injected into node j is approximately:

[0125]

[0126] Since voltage sensitivity represents the influence of the power injected into node j on the voltage change of node i, the active power injected into node P is pv,j and reactive power Q pv,j Taking partial derivatives we get:

[0127]

[0128] Based on the concept of voltage sensitivity and the result of partial derivative of the above formula, the voltage sensitivity can be determined by:

[0129]

[0130]

[0131] In the formula, is the voltage sensitivity of node i to the active power injected into node j, where node i is the analysis node; R k is the real part of the line impedance; V k is the voltage of node k; The voltage sensitivity of node i to the reactive power injected into node j; X k is the imaginary part of the line impedance. It can be seen that the voltage sensitivity between any two nodes is only related to the impedance of the feeder; the greater the line resistance, the greater the node sensitivity to active power; the greater the line reactance, the greater the node sensitivity to reactive power.

[0132] When reactive power resources are sufficient, if the voltage of each node returns to normal after step 2), the voltage control further includes the following steps:

[0133] Eliminate the devices that have participated in the regulation in step 2) when the reactive resources are sufficient, and for the nodes corresponding to the remaining regulation devices, take the minimum network loss of the distribution network system as the objective function, determine the voltage regulation strategy that meets the corresponding constraints, and combine the network loss sensitivity of the system network loss corresponding to each node to the node to inject active and reactive power. The regulation of the selected regulation devices is carried out until the change in the system network loss after regulation is less than the corresponding set threshold.

[0134] Furthermore, if the node voltages of the medium and low voltage distribution networks are not over-limited, the following steps are performed:

[0135] Taking the minimum network loss of the distribution network as the objective function, the voltage control strategy that meets the corresponding constraints is determined, and the control equipment is selected according to the network loss sensitivity of the system network loss corresponding to each node to the active and reactive power injected into the node to perform control until the dynamic change of the system network loss is less than the corresponding set threshold.

[0136] Therefore, on the basis of minimizing the offset of the control voltage and restoring the node voltage to normal as much as possible through regulation with the minimum total voltage offset of each node in the distribution network system as the objective function, the effect of minimizing the active power loss of the line is achieved through regulation with the minimum network loss of the distribution network system as the objective function; since the voltage changes greatly and the change rate is fast in the process of node voltage recovery through regulation with the minimum total voltage offset of each node in the distribution network system as the objective function, which may cause more active power loss, after the voltage is restored, the active power loss of the line is reduced as soon as possible through regulation with the minimum network loss of the distribution network system as the objective function, which can effectively reduce network loss and improve energy utilization.

[0137] In this embodiment, the control device selected according to the network loss sensitivity of the active and reactive power injected by the node according to the system network loss corresponding to each node is controlled until the change in the system network loss after control is less than the corresponding set threshold. The method includes:

[0138] Determine from each node the node whose corresponding system network loss sensitivity to the active and reactive power injected by the node is negative and has the largest absolute value, and select the control device at the node;

[0139] Taking the minimum network loss of the distribution network system as the objective function, determine the voltage control strategy that meets the corresponding constraints and combine the control equipment (i.e. the control equipment at the above-selected node) selected according to the network loss sensitivity of the system network loss corresponding to each node to the network loss of the active and reactive power injected into the node to perform control;

[0140] After each regulation, if the difference between the system network loss before and after this regulation is less than the set lower limit threshold, it is determined that the change in the system network loss after regulation is less than the corresponding set threshold. Otherwise, the objective function is to continue to minimize the distribution network system network loss, and re-determine the voltage regulation strategy that meets the corresponding constraints for the next regulation.

[0141] Therefore, each regulation is controlled by the control equipment at the node with the best network loss control effect (that is, the network loss sensitivity of the corresponding system network loss to the active and reactive power injected by the node is negative and the absolute value is the largest). This can make each regulation as effective as possible based on limited control resources, and stop the regulation in time when the control effect of the network loss tends to be flat, so as to avoid unnecessary increase in control costs.

[0142] Specifically, similar to the method of selecting the control device at the node with the largest voltage sensitivity, determine the node whose corresponding system network loss sensitivity to the active and reactive power injected into the node is negative and has the largest absolute value, and select the control device at the node as follows: if there is a node whose network loss sensitivity to the analysis node for the active and reactive power injected is both negative and has the largest absolute value, then select the control device at the node; otherwise, if the control device at the node with the largest network loss sensitivity of reactive power to the analysis node has not been selected, select the control device; if the control device at the node with the negative network loss sensitivity of reactive power to the analysis node and has the largest absolute value has been selected, select the control device at the node with the negative network loss sensitivity of active power to the analysis node and has the largest absolute value.

[0143] Among them, the network loss sensitivity (PLS) represents the sensitivity of the system's network loss to the active / reactive power injected by the node; since the system's network loss calculation formula is:

[0144]

[0145] Where P loss is the system network loss; V i and V j are the voltages of nodes i and j respectively; G ij and B ij are the conductance and susceptance between branches respectively; δ ij is the phase angle difference between nodes; n is the total number of nodes.

[0146] Then the partial derivative of the system network loss to the injected active power and reactive power is:

[0147]

[0148] Expressed in matrix form, we get:

[0149]

[0150] In the formula, Represents the active power P of node i i Relative to the node voltage V i The rate of change, Represents the active power P of node i i Phase angle δ i The partial derivative of Represents the reactive power Q of node i i Relative to the node voltage V i The rate of change, Represents the reactive power Q of node i i Phase angle δ i The partial derivative of ; where:

[0151]

[0152] In the formula, is the network loss sensitivity of the system network loss corresponding to node i to the active power injected into node i; P is the network loss sensitivity of the system network loss corresponding to node i to the reactive power injected into node i; loss is the system network loss; the left side of the equation in matrix form represents the sensitivity of the system network loss to the active / reactive power injected by the node, and the matrix on the right side of the equation can be obtained through the Jacobian matrix and the above formula.

[0153] In addition, in the present embodiment, the voltage control strategy that satisfies the corresponding constraints and is determined by taking the minimum total voltage offset of each node of the distribution network system as the objective function, and the voltage control strategy that satisfies the corresponding constraints and is determined by taking the minimum network loss of the distribution network system as the objective function, the corresponding constraints specifically include equality constraints and inequality constraints;

[0154] The equality constraints include:

[0155]

[0156] In the formula, ΔP i is the active power change at node i, ΔQ i is the reactive power change at node i; P load,i is the active power of the load at node i, Q load,i is the reactive power of the load at node i; V i and V j are the voltages of nodes i and j respectively; G ij and B ij are the conductance and susceptance between branches respectively; δ ij is the phase angle difference between nodes; P pv,i is the active power injected at node i; Q pv,iis the reactive power injected at node i; n is the total number of nodes;

[0157] The inequality constraints include at least one or more of the constraints on the upper and lower limits of node voltage, the constraints on the transformer tap position, the constraints on the number of capacitor switching groups, the constraints on photovoltaic output, the constraints on the inverter reactive output, the constraints on energy storage capacity, and the constraints on photovoltaic active power reduction. Among them, the constraints corresponding to the node voltage constraints are:

[0158] V imin ≤V i ≤V imax

[0159] The constraints corresponding to the voltage level of the on-load tap-changing transformer are:

[0160] T imin ≤T i ≤T imax

[0161] The corresponding constraint condition for the reactive power of the parallel capacitor is:

[0162] 0≤Q C,i ≤Q C,imax

[0163] The constraints corresponding to the photovoltaic output power are:

[0164] 0≤P pv,i ≤P pv,imax

[0165] The corresponding constraint condition for the inverter output reactive power is:

[0166]

[0167] The corresponding constraint condition for the photovoltaic active power reduction is:

[0168]

[0169] The constraints corresponding to the energy storage system are:

[0170] 0≤P ESS,i ≤P ESS,imax

[0171] In the above constraint expressions, V i is the voltage at node i, V imax 、V imin Respectively represent the upper and lower limits of the voltage at node i; T iis the tap position of the on-load transformer corresponding to node i (each node has a transformer, and a node is a power supply area), T imax , T imin Respectively represent the upper and lower limits of the tap position of the on-load transformer; Q C,i is the reactive power of the capacitor at node i, Q C,imax is the upper limit of the reactive power of the capacitor; P pv,imax is the upper limit of the PV active power at node i; S pv,i is the apparent power of the PV inverter at node i; is the photovoltaic active power reduction at node i; P ESS,i represents the power of the energy storage system at node i, P ESS,imax is the power upper limit of the energy storage system at node i.

[0172] The inequality constraint condition also includes the constraint condition corresponding to the penalty function; in this embodiment, the penalty function f punish as follows:

[0173]

[0174] Where V i is the effective value of the voltage at the ith node, V n The rated voltage of the distribution network system; V imax is the voltage upper limit threshold corresponding to node i, V imin is the voltage lower limit threshold corresponding to node i; N is the total number of node voltages in the medium and low voltage distribution networks; then the constraint condition corresponding to the penalty function is: the value of the penalty function is less than the corresponding upper limit threshold;

[0175] Since the voltage control strategy that satisfies the corresponding constraints is determined by taking the minimum total voltage offset of each node in the distribution network system as the objective function and taking the minimum network loss of the distribution network system as the objective function, in the voltage control strategy that satisfies the corresponding constraints, whether taking the minimum total voltage offset of each node in the distribution network system or taking the minimum network loss of the distribution network system as the objective function, the objective function and the penalty function have different dimensions, therefore, the objective function must be normalized accordingly; for example, the objective function of minimizing the total voltage offset of each node in the distribution network system should initially be:

[0176]

[0177] Where V i Represents the voltage value (voltage effective value) of the i-th node, V n Indicates the rated voltage of the system operation; N is the total number of medium-voltage and low-voltage network node voltages, and the low-voltage network node voltage is converted to the medium-voltage side through the transformer ratio for unified calculation; then f step1represents the sum of the voltage offsets of each node in the system; therefore, after normalization, the objective function for minimizing the total voltage offset of each node in the distribution network system is:

[0178] F step1 =f step1 / f B1 +f punish

[0179] In the formula, F step1 is the objective function for minimizing the total voltage offset of each node in the distribution network system, f step1 is the sum of the voltage offsets of each node; f B1 is the total voltage offset of each node in the distribution network system before regulation; f punish is the penalty function;

[0180] The initial objective function for minimizing the network loss of the distribution network should be:

[0181]

[0182] Where P loss,i represents the active power loss of the ith line, b represents the number of system branches; f step2 That is, it represents the sum of the losses of each branch of the system, that is, the system network loss; therefore, after normalization, the objective function of minimizing the network loss of the distribution network system is:

[0183] F step2 =f step2 / f B2 +f punish

[0184] In the formula, F step2 is the objective function of minimizing the network loss of the distribution network system, f step2 is the sum of active power losses of each branch of the distribution network system; f B2 The network loss of the distribution network before regulation; punish is the penalty function.

[0185] Taking a complete voltage control as an example, the specific steps of the control process are:

[0186] (I) First, obtain the historical 24-hour user voltage data and historical one-year data information of the low-voltage distribution network, use the topology verification algorithm to verify the low-voltage distribution network topology structure, and obtain accurate low-voltage distribution network topology information.

[0187] (II) After obtaining the accurate topology structure, the low-voltage side user area is transferred to the medium-voltage side for unified power flow calculation, and the voltage over-limit judgment is made on the nodes of the medium-voltage distribution network and the low-voltage distribution network.

[0188] (III) Calculate the control quantity of the over-limit node and determine whether the reactive power resources are scarce.

[0189] (IV) If reactive power resources are scarce, the priority of each power supply area is calculated to give priority to ensuring reliable power supply to important areas.

[0190] (V) If the reactive power resources are sufficient, the node i with the largest control value (voltage offset) is selected as the analysis node.

[0191] (VI) Calculate the voltage sensitivity of the active and reactive outputs of the node where the control device is located relative to node i, select the device with the largest voltage sensitivity as the control device (the control device here refers to the regulation device), and use the algorithm to optimize the system to minimize the total voltage offset. After the voltage control is completed, if the voltage has not returned to normal, select the device with the second best voltage sensitivity as the control device, and continue to optimize until the voltage level returns to normal. The specific regulation strategy includes the regulation of parameters such as P, Q, photovoltaic output, PCS operating status, parallel capacitor operating capacity, energy storage charging and discharging active power, and on-load tap-changing transformer gear, so as to achieve voltage control of the entire distribution network system; since these regulation strategies are actually existing technologies, they will not be repeated here.

[0192] (VII) If the voltage returns to normal after the first stage, the second stage is entered. The network loss sensitivity of each control variable is calculated, and the equipment that has participated in the regulation in the first stage is eliminated. For the remaining control equipment, the equipment with negative network loss sensitivity and the largest absolute value is selected as the control equipment in the network loss optimization stage, and then the network loss is optimized.

[0193] (VIII) If the voltage in the initial state does not exceed the limit, the network loss optimization stage is directly entered.

[0194] Computer equipment example:

[0195] This embodiment provides a technical solution for a computer device, including a processor, and the processor is used to execute a computer program to implement the steps of the voltage control method for the medium and low voltage distribution network in the above-mentioned embodiment of the voltage control method for the medium and low voltage distribution network.

[0196] Since the specific working principle and working method of the computer device of this embodiment have been described in detail in the above-mentioned voltage control method embodiment of the medium and low voltage distribution network, they will not be repeated here.

[0197] The present invention has the following characteristics:

[0198] ① In the case of scarce reactive resources, by temporarily sacrificing the interests of less influential substations, the voltage demands of some dominant important substations are met first, so that the voltage quality of high-priority substations can be guaranteed after regulation, so that the limited regulation resources can be used to minimize the losses caused by voltage exceeding the limit of distribution network nodes and maximize the overall regulation effect; and in the case of sufficient reactive resources, while the total voltage offset of each node in the distribution network system is minimized through regulation, the voltage sensitivity of the analysis node is selected to regulate the regulation equipment combined with the active and reactive power injected into each node, so as to ensure the regulation effect of the regulation strategy on the node with the largest voltage offset, thereby ensuring the overall regulation effect; on the basis of ensuring the overall regulation effect, the reliability of the reactive voltage regulation results can be improved.

[0199] ② For the regulation with the minimum total voltage offset of each node as the objective function, each regulation will select the regulation device with the greatest voltage sensitivity to the analysis node relative to the active and reactive power injected at the node from the regulation devices that have not participated in the regulation to participate in the regulation. This can make the best use of the regulation resources as much as possible on the basis of limited regulation resources, thereby further improving the overall regulation effect and the reliability of the reactive voltage regulation results.

[0200] ③ On the basis of minimizing the offset of the control voltage and restoring the node voltage to normal as much as possible through regulation with the minimum total voltage offset of each node in the distribution network system as the objective function, the effect of minimizing the active power loss of the line is achieved through regulation with the minimum network loss of the distribution network system as the objective function; since the voltage changes greatly and the change rate is fast in the process of node voltage recovery through regulation with the minimum total voltage offset of each node in the distribution network system as the objective function, more active power loss may be generated. Therefore, after the voltage is restored, the active power loss of the line is reduced as soon as possible through regulation with the minimum network loss of the distribution network system as the objective function, which can effectively reduce network loss and improve energy utilization.

[0201] ④ For the regulation with the objective function of minimizing the network loss of the distribution network system, each regulation is carried out through the regulation equipment at the node with the best network loss regulation effect (that is, the network loss sensitivity of the corresponding system network loss to the active and reactive power injected by the node is negative and the absolute value is the largest). This can make each regulation as much as possible based on the limited regulation resources, and stop the regulation in time when the regulation effect of the network loss tends to be flat, so as to avoid unnecessary increase in regulation cost.

[0202] It should be understood that the above specific embodiments of the present invention are only used to illustrate or explain the principles of the present invention, but do not constitute a limitation to the present invention.

Claims

1. A voltage control method for a medium and low voltage distribution network, characterized in that: If the node voltage of the medium and low voltage distribution network exceeds the limit, then: 1) Determining whether the reactive power resources of the distribution network are scarce; 2) If it is determined that reactive resources are scarce, the voltage regulation strategy is determined and regulated by taking the maximum system voltage quality score determined according to the weight of each power supply area of ​​the distribution network and the voltage deviation of each power supply area after regulation as the objective function; the higher the priority of the power supply area, the greater the weight; Otherwise, it is determined that the reactive resources are sufficient, and the node with the largest voltage offset is taken as the analysis node. The minimum total voltage offset of each node in the distribution network system is taken as the objective function, and the voltage control strategy that meets the corresponding constraints is determined. The control device selected according to the voltage sensitivity of the analysis node to the active and reactive power injected by each node is used to perform control according to the voltage control strategy until the voltage of each node returns to normal.

2. The voltage control method for medium and low voltage distribution networks according to claim 1, characterized in that: When reactive power resources are sufficient, if the voltage of each node returns to normal after step 2), the voltage control further includes the following steps: Eliminate the devices that have participated in the regulation in step 2) when the reactive resources are sufficient, and for the nodes corresponding to the remaining regulation devices, take the minimum network loss of the distribution network system as the objective function, determine the voltage regulation strategy that meets the corresponding constraints, and combine the network loss sensitivity of the system network loss corresponding to each node to the node injected active and reactive power to regulate the regulation devices until the change of the system network loss after regulation is less than the corresponding set threshold.

3. The voltage control method for medium and low voltage distribution networks according to claim 1, characterized in that: If the node voltages of the medium and low voltage distribution networks do not exceed the limit, then: Taking the minimum network loss of the distribution network as the objective function, the voltage control strategy that meets the corresponding constraints is determined, and the control equipment selected according to the network loss sensitivity of the active and reactive power injected into the node according to the system network loss corresponding to each node is controlled until the change of the system network loss after control is less than the corresponding set threshold.

4. The voltage control method for medium and low voltage distribution networks according to claim 1, characterized in that: The method of regulating the voltage sensitivity of the analysis node by regulating the control device selected according to the active and reactive power injected into each node until the voltage of each node returns to normal includes: a) According to the voltage sensitivity of the analysis node to the active and reactive power injected into each node, the control device at the node with the largest voltage sensitivity is selected; b) Taking the minimum total voltage offset of each node as the objective function, determine the voltage control strategy that meets the corresponding constraint conditions and perform control in combination with the selected control device; if the voltage of each node does not return to normal after control, select the control device at the node with the largest voltage sensitivity other than the selected control device, and repeat step b) until the voltage of each node returns to normal; The method for selecting the control device at the node with the largest voltage sensitivity is: if there is a node where the voltage sensitivity of both active and reactive power injected to the analysis node is the largest, then the control device at this node is selected; otherwise, if the control device at the node with the largest voltage sensitivity of reactive power to the analysis node has not been selected, then this control device is selected; if the control device at the node with the largest voltage sensitivity of reactive power to the analysis node has been selected, then the control device at the node with the largest voltage sensitivity of active power to the analysis node is selected.

5. The voltage control method for medium and low voltage distribution network according to claim 2 or 3, characterized in that: The method of regulating the control device selected according to the network loss sensitivity of the active and reactive power injected into the node according to the system network loss corresponding to each node until the change amount of the system network loss after regulation is less than the corresponding set threshold includes: Determine from each node the node whose corresponding system network loss sensitivity to the active and reactive power injected by the node is negative and has the largest absolute value, and select the control device at the node; Taking the minimum network loss of the distribution network as the objective function, determine the voltage control strategy that meets the corresponding constraints and combine it with the control equipment selected according to the network loss sensitivity of the active and reactive power injected into the node according to the system network loss corresponding to each node to perform control; After each regulation, if the difference between the system network loss before and after this regulation is less than the set lower limit threshold, it is determined that the change in system network loss after regulation is less than the corresponding set threshold. Otherwise, the minimum network loss of the distribution network system is continued as the objective function, and the voltage regulation strategy that meets the corresponding constraints is re-determined for the next regulation. Determine the node whose corresponding system network loss sensitivity to the active and reactive power injected into the node is negative and has the largest absolute value, and select the control device at the node as follows: if there is a node whose network loss sensitivity to the analysis node when active and reactive power are injected is negative and has the largest absolute value, then select the control device at the node; otherwise, if the control device at the node with the largest network loss sensitivity of reactive power to the analysis node has not been selected, select the control device; if the control device at the node with the negative network loss sensitivity of reactive power to the analysis node and the largest absolute value has been selected, select the control device at the node with the negative network loss sensitivity of active power to the analysis node and the largest absolute value.

6. The voltage control method for medium and low voltage distribution networks according to claim 1, characterized in that: The priority of power supply areas is determined by: According to the weight values ​​of the evaluation indicators of the power supply area, the standardized indicator values ​​corresponding to the evaluation indicators are weighted and summed to obtain the priority evaluation value of the power supply area, which is used to determine the priority of the power supply area; The method for determining the standardized index value corresponding to each evaluation index includes: In the formula, y ij is the original index value of the jth evaluation index of the ith station; z ij is the standardized index value of the jth evaluation index of the ith substation; min{} is the minimum value function, and max{} is the maximum value function.

7. The voltage control method for medium and low voltage distribution networks according to claim 1, characterized in that: The voltage sensitivity is determined by: In the formula, is the voltage sensitivity of node i to the active power injected into node j, where node i is the analysis node; R k is the real part of the line impedance; V k is the voltage of node k; The voltage sensitivity of node i to the reactive power injected into node j; X k is the imaginary part of the line impedance.

8. The voltage control method for medium and low voltage distribution networks according to claim 2 or 3, characterized in that: The method for determining the network loss sensitivity includes: In the formula, Represents the active power P of node i i Relative to the node voltage V i The rate of change, Represents the active power P of node i i Phase angle δ i The partial derivative of Represents the reactive power Q of node i i Relative to the node voltage V i The rate of change, Represents the reactive power Q of node i i Phase angle δ i The partial derivative of in: In the formula, is the network loss sensitivity of the system network loss corresponding to node i to the active power injected into node i; P is the network loss sensitivity of the system network loss corresponding to node i to the reactive power injected into node i; loss is the system network loss; V i and V j are the voltages of nodes i and j respectively; G ij is the conductance between branches; δ ij is the phase angle difference between nodes; n is the total number of nodes.

9. The voltage control method for medium and low voltage distribution networks according to claim 1 or 2, characterized in that: The corresponding constraints include equality constraints and inequality constraints; The equality constraints include: In the formula, ΔP i is the active power change at node i, ΔQ i is the reactive power change at node i; P load,i is the active power of the load at node i, Q load,i is the reactive power of the load at node i; V i and V j are the voltages of nodes i and j respectively; G ij and B ij are the conductance and susceptance between branches respectively; δ ij is the phase angle difference between nodes; P pv,i is the active power injected at node i; Q pv,i is the reactive power injected at node i; n is the total number of nodes; The inequality constraint condition includes at least one of the constraint conditions corresponding to the constraint conditions on the upper and lower limits of the node voltage, the constraint on the transformer tap position, the constraint on the number of capacitor switching groups, the constraint on the photovoltaic output, the constraint on the inverter reactive output, the constraint on the energy storage capacity, and the constraint on the photovoltaic active power reduction; The inequality constraint condition also includes a constraint condition corresponding to a penalty function; the penalty function f punish as follows: Where V i is the effective value of the voltage at the ith node, V n The rated voltage of the distribution network system; V imax is the voltage upper limit threshold corresponding to node i, V imin is the voltage lower limit threshold corresponding to node i; N is the total number of node voltages in the medium and low voltage distribution networks; the constraint condition corresponding to the penalty function is: the value of the penalty function is less than the corresponding upper limit threshold; The objective function for minimizing the total voltage offset of each node in the distribution network system is: F step1 =f step1 / f B1 +f punish In the formula, F step1 is the objective function for minimizing the total voltage offset of each node in the distribution network system, f step1 is the sum of the voltage offsets of each node; f B1 is the total voltage offset of each node in the distribution network system before regulation; f punish is the penalty function; The objective function of minimizing the network loss of the distribution network system is: F step2 =f step2 / f B2 +f punish In the formula, F step2 is the objective function of minimizing the network loss of the distribution network system, f step2 is the sum of active power losses of each branch of the distribution network system; f B2 The network loss of the distribution network before regulation; punish is the penalty function.

10. A computer device comprising a processor, characterized in that: The processor is used to execute a computer program to implement the steps of the voltage control method for a medium and low voltage distribution network as described in any one of claims 1-9.

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