Power distribution network relay protection collaborative optimization method and system considering new energy

Abstract

The invention relates to the technical field of relay protection, in particular to a power distribution network relay protection collaborative optimization method and system considering new energy, and the method comprises the steps: constructing a model architecture of a power distribution network; based on the new energy access characteristics, the topological structure of the power distribution network and the line parameters of the power distribution network, performing simulation and calculation on a short-circuit fault possibly occurring in the power distribution network to obtain a short-circuit current calculation result; determining relay protection equipment of the power distribution network according to the topological structure of the power distribution network, and determining a protection constant value of each protection section of the relay protection equipment according to a short-circuit current calculation result and a protection constant value setting principle; establishing an optimization model to update an iteration decision variable, and obtaining an optimal solution of the decision variable; and adjusting the configuration of the relay protection equipment according to the optimal solution of the decision variable. By comprehensively considering the influence of new energy access on short-circuit current distribution, the reliability and effectiveness of a relay protection system are improved, and the economic operation efficiency of a power distribution network is enhanced.

Description

Technical Field

[0001] The present invention relates to the technical field of relay protection, and in particular to a method and system for collaborative optimization of relay protection for a distribution network taking new energy sources into account. Background Art

[0002] With the development of new energy technologies, distributed new energy such as solar photovoltaic panels and wind turbines have gradually become an indispensable part of the power system. The access of these new energy sources has changed the single-side power supply characteristics of the traditional distribution network, making the originally fixed current direction dynamic. With the increasing number of new energy access, the effectiveness of the protection measures of the traditional distribution network protection system has been challenged.

[0003] Specifically, the current distribution network mainly adopts a single-side power supply radial power supply network structure, whose current and power directions are relatively fixed. Relay protection equipment is usually designed and configured based on a single-end power supply system, with conventional, simple and reliable current protection such as three-stage current speed protection and inverse time overcurrent protection as the mainstream. For feeders and some important cable lines with large changes in system operation mode, considering that current protection is difficult to meet the corresponding requirements, distance protection is often used for configuration. With the access of distributed new energy, longitudinal differential protection with good selectivity and speed has become a new feasible solution. In addition, the mainstream configuration of 10kV feeder protection is two-stage overcurrent protection. The overcurrent I stage protection is set according to the maximum three-phase short-circuit current at the end of the main line and the low backup current value of the main transformer in the station, while the overcurrent II stage protection is set according to the load current.

[0004] However, the problem with the existing technology is that when the penetration rate of new energy sources gradually increases, the selectivity and sensitivity of traditional distribution network relay protection schemes are limited, because most of these schemes do not fully consider the uncertainty of current direction caused by the access of new energy sources. As a result, in some cases, the protection device may not be able to accurately identify the fault location, thereby prolonging the fault isolation time. In addition, due to the change in the short-circuit current distribution in the distribution network caused by the access of new energy sources, the traditional relay protection setting calculation based on fixed current direction is no longer applicable, thereby reducing the reliability and effectiveness of the protection system. The existence of these problems makes the distribution network face the risk of unreasonable protection settings and reduced system stability when introducing new energy, which in turn affects the power supply quality and economic operation efficiency. Summary of the invention

[0005] In order to solve one of the above-mentioned problems in the prior art, the present invention provides a method and system for collaborative optimization of relay protection in a distribution network taking into account new energy.

[0006] To achieve the above invention, the present invention provides a coordinated optimization method for relay protection of a distribution network taking into account new energy. The distribution network is connected to distributed new energy. The method includes: constructing a model architecture of the distribution network, the model architecture at least including: new energy access characteristics, distribution network topology and distribution network line parameters, wherein the new energy access characteristics include: new energy capacity and new energy access location; based on the new energy access characteristics, the distribution network topology and the distribution network line parameters, simulating and calculating the short-circuit faults that may occur in the distribution network to obtain a short-circuit current calculation result; determining the relay protection device of the distribution network according to the distribution network topology, and determining the protection setting value of each protection section of the relay protection device according to the short-circuit current calculation result and the protection setting value setting principle, wherein the protection setting value is a threshold set for realizing relay protection; establishing an optimization model to update iterative decision variables to obtain the optimal solution of the decision variables, wherein the decision variables include configuration information of the relay protection device, and the configuration information at least includes the protection setting value; adjusting the configuration of the relay protection device according to the optimal solution of the decision variables.

[0007] On the other hand, the present invention provides a distribution network relay protection collaborative optimization system taking into account new energy, wherein the distribution network is connected to distributed new energy, and the system includes: a new energy access impact analysis module for constructing a model architecture of the distribution network, wherein the model architecture at least includes: new energy access characteristics, distribution network topology structure and distribution network line parameters, wherein the new energy access characteristics include: new energy capacity and new energy access location; and based on the new energy access characteristics, the distribution network topology structure and the distribution network line parameters, the short-circuit faults that may occur in the distribution network are simulated and calculated to obtain the short-circuit current calculation result. ; A relay protection setting evaluation module, used to determine the relay protection equipment of the distribution network according to the distribution network topology, and determine the protection setting of each protection section of the relay protection equipment according to the short-circuit current calculation result and the protection setting setting principle, wherein the protection setting is a threshold set for realizing relay protection; an operation mode optimization module, used to establish an optimization model to update iterative decision variables and obtain the optimal solution of the decision variables, wherein the decision variables include the configuration information of the relay protection equipment, and the configuration information at least includes the protection setting; and adjust the configuration of the relay protection equipment according to the optimal solution of the decision variables.

[0008] The beneficial effects of the present invention are reflected in that the distribution network relay protection collaborative optimization method and system taking into account new energy provided by the present invention consider the reliability evaluation of relay protection setting value and the collaborative optimization of operation mode under new energy, aiming to solve the distribution network protection problem brought about by the access of new energy. The system constructs a distribution network model including distributed power sources, quantitatively analyzes the impact of new energy access on the short-circuit current of the distribution network, and re-evaluates the relay protection setting value based on these impacts to ensure that the protection system can still operate effectively under the new operating conditions. The distribution network relay protection collaborative optimization system of the present invention solves the problem of insufficient selectivity and sensitivity of traditional protection schemes under the condition of new energy access by dynamically adjusting the relay protection setting value, ensures that the fault location can be accurately identified and quickly isolated, and shortens the fault recovery time. At the same time, by comprehensively considering the impact of new energy access on the distribution of short-circuit current, the reliability and effectiveness of the relay protection system are improved, and the problem of system stability degradation caused by unreasonable protection setting value is avoided, thereby improving the power supply quality and enhancing the economic operation efficiency of the distribution network. These improvement measures effectively overcome the limitations of the existing technology in dealing with new energy access, and provide a solid foundation for the safe and stable operation of the distribution network. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A block diagram of a coordinated optimization system for relay protection of a distribution network taking into account new energy provided in Example 1 of the present invention;

[0010] Figure 2 A schematic diagram of a specific example of the steps for implementing the optimization model algorithm provided in Example 1 of the present invention;

[0011] Figure 3 Another block diagram of the distribution network relay protection collaborative optimization system taking into account new energy provided in Embodiment 1 of the present invention;

[0012] Figure 4 This is a flow chart of the coordinated optimization method for relay protection of distribution network taking into account new energy provided in Example 1 of the present invention. DETAILED DESCRIPTION

[0013] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. 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 creative work are within the scope of protection of the present invention.

[0014] Example 1

[0015] This embodiment provides a distribution network relay protection collaborative optimization system 10 taking into account new energy sources, wherein the distribution network is connected to distributed new energy sources (also called distributed power sources, including solar photovoltaic panels, wind turbines, etc.). Figure 1 As shown, the distribution network relay protection collaborative optimization system 10 of the present invention includes: a new energy access impact analysis module 101, a relay protection constant value evaluation module 102 and an operation mode optimization module 103. Among them, the new energy access impact analysis module 101 is used to construct a distribution network model including distributed power sources, and simulate and analyze the impact of new energy access on short-circuit current; the relay protection constant value evaluation module 102 re-evaluates and adjusts the relay protection constant value based on the short-circuit current calculation results to adapt to multi-source power supply conditions; the operation mode optimization module 103 provides optimization strategies suitable for different operating states to ensure efficient and reliable system operation. The specific implementation of each module is as follows:

[0016] The new energy access impact analysis module 101 is used to construct a model framework of the distribution network, which at least includes: new energy access characteristics, distribution network topology structure and distribution network line parameters, wherein the new energy access characteristics include: new energy capacity and new energy access location; and based on the new energy access characteristics, distribution network topology structure and distribution network line parameters, the short-circuit faults that may occur in the distribution network are simulated and calculated to obtain the short-circuit current calculation results. By accurately calculating the short-circuit current, the impact of new energy access on the short-circuit current of the distribution network can be quantified.

[0017] Specifically, the new energy access impact analysis module 101 is one of the core components of the present invention. It is responsible for constructing a distribution network model including distributed power sources, and simulating and analyzing the impact of new energy access on the short-circuit current of the distribution network. This module forms a detailed network model through in-depth analysis of the topological structure of the distribution network, combined with factors such as the access location and capacity of the distributed power sources, so as to facilitate subsequent accurate short-circuit current calculation. In the process of model construction, it is necessary to collect and input distribution network line parameters, including but not limited to line resistance R, reactance X, and output characteristic parameters of the distributed power sources, such as maximum output power P max , output power factor PF, etc., thereby forming a mathematical model of the distribution network that can reflect the actual operating conditions.

[0018] After the distribution network model is built, the short-circuit current calculation will be performed. During the calculation process, all possible short-circuit types that may occur in the system must be determined first, including but not limited to three-phase short circuit, two-phase short circuit to ground, etc., and the model must be simulated based on each short-circuit type. The mathematical formulas involved in the simulation process can be network equations based on Ohm's law and Kirchhoff's law, such as:

[0019]

[0020] Among them, I represents the short-circuit current, U represents the voltage before the short circuit, and Z represents the comprehensive impedance at the short circuit point. The comprehensive impedance Z includes the line impedance and the internal impedance of the distributed power supply. For multi-source power supply, it is necessary to consider the contribution of all power supply points to the short circuit point, that is:

[0021] Z total =Z line +Z source

[0022] Among them, Z total Represents the comprehensive impedance, Z line Represents the impedance of the line from the power supply point to the short-circuit point, Z source Indicates the internal impedance of the power supply point.

[0023] After the short-circuit current calculation is completed, the short-circuit current calculation result will be used in the relay protection setting evaluation module 102 to provide data support for the subsequent protection setting adjustment. Through the accurately calculated short-circuit current, the setting value of the relay protection equipment can be adjusted more accurately to ensure that the distribution network can still maintain high reliability and economy when new energy is connected. In addition, the design of this module can also reserve an interface to connect with the operation mode optimization module 103, so as to adjust the protection setting according to different system operation states and realize dynamic optimization control.

[0024] The relay protection setting value evaluation module 102 is used to determine the relay protection equipment of the distribution network according to the topological structure of the distribution network, and determine the protection setting value of each protection segment of the relay protection equipment according to the short-circuit current calculation result and the protection setting value setting principle. The protection setting value is the threshold set for realizing relay protection. Specifically, relay protection equipment is provided in the distribution network system, and the start-up of these relay protection equipment requires certain triggering conditions. The protection setting value refers to the action value of the relay protection equipment set in order to protect the distribution network system and its components (such as generators, transformers, transmission lines, etc.) from the influence of faults or abnormal working conditions. These setting values ​​ensure that when a fault occurs in the distribution network system, the relay protection equipment can act quickly and accurately, cut off the faulty part or send out an alarm signal, thereby ensuring the safe and stable operation of the distribution network system. The relay protection equipment can have multiple protection segments (for example: overcurrent two-stage protection, overcurrent three-stage protection, etc.), and each protection segment can be set with the same or different protection setting values ​​to realize segmented protection.

[0025] The relay protection setting value evaluation module 102 is based on the short-circuit current calculation results provided by the new energy access impact analysis module 101, and according to the distribution network topology and system operation mode, it sorts out the current relay protection equipment conditions of the distribution network and determines the setting value of each protection section. The relay protection setting value evaluation module 102 analyzes the short-circuit current data obtained from the new energy access impact analysis module 101 and uses a series of setting rules to ensure that the relay protection system can still maintain high reliability and economy under the condition of introducing new energy.

[0026] Specifically, the relay protection setting evaluation module 102 first obtains the branch impedance matrix containing multi-level branch distribution networks based on the distribution network topology constructed in the new energy access impact analysis module 101, and uses the short-circuit current calculation results to determine the protection setting of each protection section. Factors such as the topology of the distribution network, the access location and capacity of the distributed power source need to be taken into consideration to ensure that the relay protection equipment can correctly and quickly respond to faults under different operating conditions and minimize the impact of faults.

[0027] In the distribution network, there are many relay protection methods that can be used, such as current protection, voltage protection, etc. Different relay protection methods can adopt different protection settings and protection setting principles. Overcurrent protection is one of the common protection forms. Therefore, in an optional implementation, the protection setting can be a current setting, which is the current threshold set to achieve overcurrent protection. Overcurrent protection can adopt a segmented protection mechanism, which can generally be two-stage protection or three-stage protection. Different protection settings can be set for each protection segment to achieve the effect of graded or segmented protection.

[0028] For example, for the 10kV feeder protection in the substation, two-stage overcurrent protection is the mainstream configuration. The overcurrent stage I protection is set according to the maximum three-phase short-circuit current at the end of the main line and the low backup current value of the main transformer in the station; the overcurrent stage II protection is set according to the load current, and comprehensively considers the safe current carrying capacity of the main line and the primary rated current value of the current transformer (CT).

[0029] In an optional implementation, the distribution network system can be configured with multiple switches to protect the distribution network. The first level of protection can be a substation switch, and other levels of protection can be other switches or other forms. The relay protection setting value evaluation module 102 can adopt the following protection setting value setting principles:

[0030] For the substation switch as the first level protection, the overcurrent I stage protection time is set to 0 seconds, the current setting value is set according to the maximum short-circuit current at the second level switch setting, and the minimum short-circuit current at the 10kV busbar in the minimum mode is used for verification. The specific calculation is as follows:

[0031] I set,I,1=K I I sc,2,max

[0032] Among them, I set,I,1 Indicates the current setting value of the first-level overcurrent I stage protection; K I is a coefficient, usually greater than 1, to ensure that the overcurrent I stage protection can reliably avoid the maximum short-circuit current at the second-stage switch; I sc,2,max Indicates the maximum short-circuit current at the second-stage switch.

[0033] For the second level protection, the time of overcurrent I stage protection is also set to 0 seconds, and the current setting value should be set to no more than 0.9 times the minimum short-circuit current at the third level switch. If there is no third level switch on the rear side, it should be set to no more than the minimum short-circuit current at the end of the channel where the second level switch is located. The specific calculation is as follows:

[0034] I set,I,2 =K I 0.9 I sc,3,min

[0035] Among them, I set,I,2 Indicates the current setting value of the second-level overcurrent I stage protection; I sc,3,min Indicates the minimum short-circuit current at the third-stage switch.

[0036] For the third level protection, the overcurrent I stage protection time is also 0 seconds, and the current setting value is set to be no greater than the minimum short-circuit current at the end of the line. The specific calculation is as follows:

[0037] I set,I,3 =K I I sc,end,min

[0038] Among them, I set,I,3 Indicates the current setting value of the third-level overcurrent I stage protection; I sc,end,min Indicates the minimum short-circuit current at the end of the line.

[0039] The overcurrent II protection time of the first-level protection is 0.2 seconds, and the current setting is set according to the maximum short-circuit current at the third-level switch setting, and is checked with the minimum short-circuit current at the second-level switch. The specific calculation is as follows:

[0040] I set,II,1 =K II I sc,3,max

[0041] Among them, I set,II,1 Indicates the current setting value of the first-level overcurrent II protection; I sc,3,max Indicates the maximum short-circuit current at the third-level switch; K IIIt is a coefficient, which is usually greater than 1 to ensure that the overcurrent II stage protection can reliably avoid the maximum short-circuit current at the third-level switch.

[0042] The protection time of the second-level overcurrent II stage is 0.5 to 0.8 seconds, and the current setting value is set to no more than 0.9 times of the first-level overcurrent III stage. The specific calculation is as follows:

[0043] I set,II,2 =K II 0.9 I set,III,1

[0044] Among them, I set,II,2 Indicates the current setting value of the second-level overcurrent II protection; I set,III,1 Indicates the current setting value of the first-level overcurrent III section.

[0045] The protection time of the overcurrent II stage of the third level protection is 0.3 to 0.5 seconds, and the current setting value is set to no more than 0.9 times of the second level overcurrent II stage. The specific calculation is as follows:

[0046] I set,II,3 =k II 0.9 I set,II,2

[0047] Among them, I set,II,3 Indicates the current setting value of the third-level overcurrent II protection; I set,II,2 Indicates the current setting value of the second-level overcurrent II section.

[0048] The time of overcurrent stage III protection is set to 0.7 to 1.0 seconds, and the current setting is set according to the maximum load and considering the conductor current and CT rated current. The specific calculation is as follows:

[0049] I set,III =min(K III I load,max ,K III I wire,max ,K III I CT,rated )

[0050] Among them, I set,III Indicates the current setting value of overcurrent III protection; I load,max Indicates the maximum load current; I wire,max Indicates the current carrying capacity of the conductor; I CT,rated Indicates the primary rated current of CT; K III It is a coefficient, usually greater than 1, to ensure that the overcurrent stage III protection can reliably avoid the maximum load current, the conductor current carrying capacity and the CT primary rated current.

[0051] Through the operation of the relay protection setting value evaluation module 102, the distribution network can maintain a high level of reliability and power supply quality while introducing new energy, ensuring efficient and economical operation under different operating conditions. The relay protection setting value evaluation module 102 not only improves the adaptability of the distribution network to the access of new energy, but also provides strong technical support for the safe and stable operation of the distribution network.

[0052] In an optional embodiment, after determining the protection setting of each protection section of the relay protection device, the relay protection setting evaluation module 102 is also used to verify through simulation or experiment whether the protection setting can enable the relay protection device to perform correct actions when a fault occurs in the distribution network; if the relay protection device does not perform correct actions, the protection setting is re-determined. The rationality and reliability of the protection setting can be verified through simulation or experiment to ensure that the relay protection device can perform correct actions when a fault occurs.

[0053] The operation mode optimization module 103 is used to establish an optimization model to update iterative decision variables and obtain the optimal solution of the decision variables, wherein the decision variables include the configuration information of the relay protection device, the configuration information at least includes the protection setting, and adjust the configuration of the relay protection device according to the optimal solution of the decision variables. Specifically, the relay protection device may include switches and other devices, and the decision variables may include the protection setting, switch status, etc. of the relay protection device.

[0054] Specifically, the operation mode optimization module 103 further develops optimization strategies applicable to different operation states based on the work of the relay protection setting evaluation module 102. The operation mode optimization module 103 develops a set of optimization strategies based on the topological structure of the distribution network, the access location and capacity of the distributed power source, and the system's large and small operation modes. Its purpose is to ensure that the distribution network can maintain high reliability, high power supply quality and economic operation efficiency while introducing new energy.

[0055] The operation mode optimization module 103 can first define different operating states of the distribution network system, including the system's large operation mode and small operation mode. The large operation mode usually refers to the distribution network system operating under higher load or larger output of new energy, while the small operation mode is the opposite. The operation mode optimization module 103 needs to consider factors such as the topological structure of the distribution network, the access location and capacity of the distributed power source based on these operating states to decide how to adjust the protection setting of the relay protection equipment to ensure that efficient protection action can be achieved in any operating mode.

[0056] In an optional embodiment, an optimization model is established to update and iterate decision variables to obtain the optimal solution of the decision variables, which may include the following steps: setting constraints on the decision variables according to the relay protection device; judging whether the decision variables satisfy the constraints; if the decision variables satisfy the constraints, judging whether the decision variables satisfy the preset optimal rules according to the total cost function, wherein the total cost function is determined according to the decision variables and is used to measure the total cost required to configure the relay protection device according to the configuration information of the relay protection device contained in the decision variables; if the preset optimal rules are satisfied, the decision variables are determined to be the optimal solution; if the preset optimal rules are not satisfied, the decision variables are repeatedly adjusted to obtain new decision variables until the new decision variables satisfy both the constraints and the preset optimal rules, and the new decision variables are determined to be the optimal solution.

[0057] Specifically, in order to achieve optimization, the operation mode optimization module 103 can adopt an optimization model algorithm based on constraints. The constraints are used to ensure that the optimization results meet the limitations in actual projects, such as the protection setting value cannot exceed the specified range, the switch state cannot violate the electrical connectivity and other constraints. The total cost function is used to measure the total cost of the distribution network system under the current configuration, which can include the weighted sum of reliability and economy. The preset optimal rule can be to calculate the total cost required under the decision variable (including reliability cost and economic cost) according to the total cost function. When the total cost required for the decision variable is lower than the preset threshold or lower than the total cost required for other decision variables, it can be considered that the decision variable meets the preset optimal rule. The goal of the optimization model algorithm is to improve the economy and reliability of the system as much as possible under the premise of ensuring the safe and stable operation of the distribution network.

[0058] The mathematical model of the algorithm can be expressed as:

[0059] Minimize: C(x) = w1·R + w2·D

[0060]

[0061] Where C(x) represents the total cost function; x represents the decision variable vector; w1 and w2 are weighting factors used to balance the two objectives of reliability and economy; R represents the reliability index, D represents the economy index; g i (x) and h j (x) represent inequality constraints and equality constraints respectively.

[0062] The following is a specific example of the implementation steps of the above optimization model algorithm. Figure 2 As shown, this can be achieved through the following steps:

[0063] (1) Initialize decision variables: First, initialize the decision variable x.

[0064] (2) Calculate the objective function (total cost function): Based on the current decision variable x, calculate the objective function C(x).

[0065] (3) Check constraints: Check whether the current decision variable x satisfies all constraints g i (x)≤0 and h j (x)=0.

[0066] (4) Update decision variables: If the current decision variable x does not satisfy the constraints, adjust the decision variable to make it satisfy the constraints. This process can be achieved through gradient descent or other optimization methods.

[0067] (5) Iterative optimization: The decision variable x is updated through repeated iterations. Each iteration checks whether the current decision variable satisfies all constraints and calculates the value of the objective function C(x). If the new decision variable x is worse than the previous historical optimal solution, the optimal solution is updated; if the new decision variable x is not as good as the previous historical optimal solution, the search direction is adjusted according to the strategy of the optimization algorithm, and the next decision variable x is searched until the termination condition is met or the preset upper limit of the number of iterations is reached.

[0068] In a specific implementation, in order to implement the above optimization model, the present invention can use a mixed integer linear programming method to solve problems with discrete decision variables. Assume that there are N protection devices in the distribution network, and each protection device has M possible setting configurations. Let x ij represents the state variable of the i-th protection device in the j-th configuration, y ij Indicates whether the i-th protection device selects the j-th configuration (0 or 1). Then the optimization model problem can be expressed as:

[0069]

[0070] Among them, c ij represents the cost of the i-th protection device in the j-th configuration; is the first constraint, which ensures that each protection device can only choose one configuration; ij ∈{0,1} is the second constraint, which means that y ij is a binary variable.

[0071] Through the operation of the operation mode optimization module 103, the configuration result of the relay protection equipment is optimized, thereby ensuring that the distribution network can maintain an efficient and reliable operation state when facing the uncertainty of the current direction caused by the access of new energy. The operation mode optimization module 103 not only improves the adaptability of the distribution network to the access of new energy, but also provides technical support for realizing the economic operation of the distribution network.

[0072] The distribution network relay protection collaborative optimization system considering new energy provided in this embodiment takes into account the reliability evaluation of relay protection settings and the collaborative optimization of operation modes under new energy, aiming to solve the distribution network protection problems brought about by the access of new energy. The system constructs a distribution network model including distributed power sources, quantitatively analyzes the impact of new energy access on the short-circuit current of the distribution network, and re-evaluates the relay protection settings based on these impacts to ensure that the protection system can still operate effectively under new operating conditions. The distribution network relay protection collaborative optimization system of this embodiment solves the problem of insufficient selectivity and sensitivity of traditional protection schemes under the condition of new energy access by dynamically adjusting the relay protection settings, ensuring that the fault location can be accurately identified and quickly isolated, and shortening the fault recovery time. At the same time, by comprehensively considering the impact of new energy access on the distribution of short-circuit current, the reliability and effectiveness of the relay protection system are improved, and the problem of system stability degradation caused by unreasonable protection settings is avoided, thereby improving the power supply quality and enhancing the economic operation efficiency of the distribution network. These improvement measures effectively overcome the limitations of the existing technology in dealing with new energy access, and provide a solid foundation for the safe and stable operation of the distribution network.

[0073] In an optional embodiment, if Figure 3 As shown, the distribution network relay protection collaborative optimization system 10 of this embodiment further includes:

[0074] The dynamic adjustment control module 104 is used to recalculate the protection setting according to a preset algorithm when a change in the operating state of the distribution network is detected, wherein the change in the operating state of the distribution network includes at least one of the following: output fluctuations of distributed new energy, changes in the load of the distribution network, or changes in the topology of the distribution network. When the operating state of the distribution network system changes, the existing protection setting may no longer be able to protect the distribution network system. Therefore, the dynamic adjustment control module 104 is responsible for adjusting the protection setting in real time under different working conditions to ensure the stability and effectiveness of the entire distribution network relay protection system.

[0075] The dynamic adjustment control module 104 is a key link after the relay protection setting evaluation module 102 and the operation mode optimization module 103. The module is designed to dynamically adjust the relay protection setting according to the actual operation state of the distribution network to ensure that the distribution network can operate efficiently and reliably under different working conditions. The dynamic adjustment control module 104 can receive the optimization results from the operation mode optimization module 103 and apply them to the actual system to achieve real-time dynamic adjustment.

[0076] In actual applications, the dynamic adjustment control module 104 monitors the state of the distribution network in real time, including but not limited to the real-time output power of the distributed power source, the system load, the change of the grid topology structure, etc. When a change in the operating state of the distribution network is detected, such as a fluctuation in the output of the distributed power source, a change in the load, or a change in the network topology, the dynamic adjustment control module 104 will recalculate the protection setting according to a pre-set algorithm. The goal of the algorithm is to minimize the fault response time and improve the selectivity of the protection while ensuring the safe and stable operation of the distribution network.

[0077] In an optional implementation, in order to achieve the control target, the dynamic adjustment control module 104 can also use an algorithm based on predictive control theory. The algorithm can adjust the protection setting value in advance based on the prediction of the distribution network operation state in the future to cope with the upcoming system changes. The mathematical model of the algorithm can be expressed as:

[0078]

[0079] Subject to:x(t+1)=Ax(t)+Bu(t)

[0080] e(t)=y d (t)-y(t)

[0081] Among them, x(t) represents the current state, x(t+1) represents the state at the next moment, J(x(t)) represents the performance index, and T p represents the prediction time window length, Q and R are weight matrices, e(t) represents the error signal, y d (t) represents the desired output, y(t) represents the actual output, u(t) represents the control input, x(t) represents the state variable, and A and B are system matrices.

[0082] Assume that the current system state is x(t), predict the future T p The states in time are x(t+1), x(t+2),…, x(t+T p ). Through the predictive control algorithm, the control input u(t) that can minimize the performance index J(x(t)) is found, and then the state variable x(t) is updated.

[0083] Specifically, assuming that the system state x(t) includes variables such as the protection setting of the protection device and the switch state, the system matrices A and B describe the relationship between the system state and time. Through the optimization algorithm, the optimal control input u(t) that can minimize the performance index J(x(t)) is found, and then the state variable x(t) is updated.

[0084] In practical applications, the dynamic adjustment control module 104 needs to obtain the state information of the distribution network in real time. When a change in the system state is detected, the dynamic adjustment control module 104 immediately calls the above algorithm model to adjust the protection setting and other configurations according to the current system state and the predicted future state change.

[0085] By dynamically adjusting the operation of the control module 104, the distribution network can maintain a high level of reliability and power supply quality while introducing new energy, ensuring efficient and economical operation under different operating conditions.

[0086] This embodiment also provides a distribution network relay protection collaborative optimization method taking into account new energy sources, which is used to implement the distribution network relay protection collaborative optimization system mentioned above in this embodiment. In the aforementioned distribution network relay protection collaborative optimization system, each module of the system has been described in detail, and will not be repeated here. Figure 4 As shown, the distribution network relay protection collaborative optimization method includes the following steps:

[0087] Step S401, construct a model framework of the distribution network, the model framework includes at least: new energy access characteristics, distribution network topology and distribution network line parameters, wherein the new energy access characteristics include: new energy capacity and new energy access location. Specifically, through an in-depth analysis of the distribution network topology, combined with factors such as the access location and capacity of distributed power sources, a detailed network model can be formed to facilitate subsequent accurate short-circuit current calculations. In the process of model construction, it is necessary to collect and input distribution network line parameters, including but not limited to line resistance, reactance, and output characteristic parameters of distributed power sources, such as maximum output power, output power factor, etc., so as to form a distribution network mathematical model that can reflect the actual operating conditions.

[0088] Step S402, based on the new energy access characteristics, the distribution network topology and the distribution network line parameters, the short-circuit faults that may occur in the distribution network are simulated and calculated to obtain the short-circuit current calculation results. After the distribution network model is built, the short-circuit current calculation will be performed. In the calculation process, it is first necessary to determine all possible short-circuit types that may occur in the system, including but not limited to three-phase short circuit, two-phase short circuit grounding, etc., and simulate the model based on each short-circuit type. By accurately calculating the short-circuit current, the impact of new energy access on the short-circuit current of the distribution network can be quantified, and the setting value of the relay protection equipment can be adjusted more accurately to ensure that the distribution network can still maintain high reliability and economy when new energy is accessed.

[0089] Step S403, determine the relay protection equipment of the distribution network according to the topological structure of the distribution network, and determine the protection setting value of each protection section of the relay protection equipment according to the short-circuit current calculation result and the protection setting value setting principle. The protection setting value is the threshold set for realizing relay protection. Specifically, relay protection equipment is provided in the distribution network system, and the startup of these relay protection equipment requires certain triggering conditions. The protection setting value refers to the action value of the relay protection equipment set in order to protect the distribution network system and its components (such as generators, transformers, transmission lines, etc.) from the influence of faults or abnormal working conditions. These setting values ​​ensure that when a fault occurs in the distribution network system, the relay protection equipment can act quickly and accurately, cut off the faulty part or send out an alarm signal, thereby ensuring the safe and stable operation of the distribution network system. The relay protection equipment can have multiple protection sections (for example: overcurrent two-stage protection, overcurrent three-stage protection, etc.), and each protection section can be set with the same or different protection setting values ​​to realize segmented protection. By calculating the protection setting value, the distribution network can maintain a high level of reliability and power supply quality while introducing new energy, ensuring efficient and economic operation under different operating conditions.

[0090] In the distribution network, there are many relay protection methods that can be used, such as current protection, voltage protection, etc. Different relay protection methods can adopt different protection settings and protection setting principles. Overcurrent protection is one of the common protection forms. Therefore, in an optional implementation, the protection setting can be a current setting, which is the current threshold set to achieve overcurrent protection. Overcurrent protection can adopt a segmented protection mechanism, which can generally be divided into two-stage protection or three-stage protection. Different protection settings can be set for each protection segment to achieve the effect of graded or segmented protection.

[0091] Step S404, establish an optimization model to update iterative decision variables and obtain the optimal solution of the decision variables, wherein the decision variables include the configuration information of the relay protection device, and the configuration information includes at least the protection setting. Specifically, the relay protection device may include devices such as switches, and the decision variables may include the protection setting, switch status, etc. of the relay protection device. The purpose of establishing the optimization model is to formulate an optimization strategy suitable for different operating conditions. According to factors such as the topological structure of the distribution network, the access location and capacity of the distributed power source, and the large and small operating modes of the system, a set of optimization strategies is formulated. The purpose is to ensure that the distribution network can maintain high reliability, high power supply quality and economic operation efficiency while introducing new energy.

[0092] In an optional embodiment, an optimization model is established to update and iterate decision variables to obtain the optimal solution of the decision variables, which may include the following steps: setting constraints on the decision variables according to the relay protection device; judging whether the decision variables satisfy the constraints; if the decision variables satisfy the constraints, judging whether the decision variables satisfy the preset optimal rules according to the total cost function, wherein the total cost function is determined according to the decision variables and is used to measure the total cost required to configure the relay protection device according to the configuration information of the relay protection device contained in the decision variables; if the preset optimal rules are satisfied, the decision variables are determined to be the optimal solution; if the preset optimal rules are not satisfied, the decision variables are repeatedly adjusted to obtain new decision variables until the new decision variables satisfy both the constraints and the preset optimal rules, and the new decision variables are determined to be the optimal solution.

[0093] Specifically, in order to achieve optimization, an optimization model algorithm based on constraints can be used. Constraints are used to ensure that the optimization results meet the limitations in actual projects, such as protection settings cannot exceed the specified range, and the switch state cannot violate electrical connectivity constraints. The total cost function is used to measure the total cost of the distribution network system under the current configuration, which can include the weighted sum of reliability and economy. The preset optimal rule can be to calculate the total cost required for the decision variable (including reliability cost and economic cost) according to the total cost function. When the total cost required for the decision variable is lower than the preset threshold or lower than the total cost required for other decision variables, it can be considered that the decision variable meets the preset optimal rule. The goal of the optimization model algorithm is to maximize the economy and reliability of the system while ensuring the safe and stable operation of the distribution network.

[0094] Step S405, adjusting the configuration of the relay protection device according to the optimal solution of the decision variable. By optimizing the configuration result of the relay protection device, it can be ensured that the distribution network can still maintain an efficient and reliable operation state when facing the uncertainty of the current direction caused by the access of new energy.

[0095] The coordinated optimization method of relay protection for distribution network taking into account new energy provided in this embodiment takes into account the reliability evaluation of relay protection setting value and the coordinated optimization of operation mode under new energy, aiming to solve the distribution network protection problem brought about by the access of new energy. The method constructs a distribution network model including distributed power sources, quantitatively analyzes the impact of new energy access on the short-circuit current of the distribution network, and re-evaluates the relay protection setting value based on these impacts to ensure that the protection system can still operate effectively under the new operating conditions. The coordinated optimization method of relay protection for distribution network in this embodiment solves the problem of insufficient selectivity and sensitivity of traditional protection schemes under the condition of new energy access by dynamically adjusting the relay protection setting value, ensures that the fault location can be accurately identified and quickly isolated, and shortens the fault recovery time. At the same time, by comprehensively considering the impact of new energy access on the distribution of short-circuit current, the reliability and effectiveness of the relay protection system are improved, and the problem of system stability degradation caused by unreasonable protection setting value is avoided, thereby improving the power supply quality and enhancing the economic operation efficiency of the distribution network. These improvement measures effectively overcome the limitations of the existing technology in dealing with new energy access, and provide a solid foundation for the safe and stable operation of the distribution network.

[0096] In an optional implementation, after determining the protection setting of each protection stage of the relay protection device in step S403, the method may further include:

[0097] Step S403a, verifying through simulation or experiment whether the protection setting can enable the relay protection device to perform correct action when a fault occurs in the distribution network;

[0098] Step S403b: if the relay protection device does not perform a correct action, redetermine the protection setting.

[0099] The rationality and reliability of protection settings can be verified through simulation or experiments to ensure that the relay protection equipment can operate correctly when a fault occurs.

[0100] In an optional implementation, the coordinated optimization method for relay protection of distribution network taking into account new energy sources in this embodiment further includes:

[0101] Step S406, when it is detected that the operating state of the distribution network has changed, the protection setting is recalculated according to a pre-set algorithm, wherein the change in the operating state of the distribution network includes at least one of the following: the output of the distributed new energy fluctuates, the load of the distribution network changes, or the topology of the distribution network changes. When the operating state of the distribution network system changes, the existing protection setting may no longer be able to protect the distribution network system. By dynamically adjusting the relay protection setting according to the actual operating state of the distribution network in step S406, it can be ensured that the distribution network can operate efficiently and reliably under different working conditions. In this step, the optimization results from the optimization model can be received and applied to the actual system to achieve real-time dynamic adjustment. An algorithm based on predictive control theory can also be used, which can adjust the protection setting in advance based on the prediction of the operating state of the distribution network in the future to cope with the upcoming system changes.

[0102] In the description of the embodiments of the present invention, it should be understood that the terms "upper", "lower", "front", "back", "left", "right", "vertical", "horizontal", "center", "top", "bottom", "top", "bottom", "inside", "outside", "inner side", "outer side" and the like indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. Among them, "inside" refers to an internal or enclosed area or space. "Periphery" refers to the area surrounding a specific component or a specific area.

[0103] In the description of the embodiments of the present invention, the terms "first", "second", "third", and "fourth" are used for descriptive purposes only and are not to be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first", "second", "third", and "fourth" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0104] In the description of the embodiments of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "install", "connect", "connect", and "assemble" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a direct connection, or an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0105] In the description of the embodiments of the present invention, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0106] In the description of the embodiments of the present invention, it is to be understood that "-" and "~" represent the range between two values, and the range includes the endpoints. For example: "AB" represents a range greater than or equal to A and less than or equal to B. "A~B" represents a range greater than or equal to A and less than or equal to B.

[0107] In the description of the embodiments of the present invention, the term "and / or" herein is merely a description of the association relationship of associated objects, indicating that three relationships may exist. For example, A and / or B may represent: A exists alone, A and B exist at the same time, and B exists alone. In addition, the character " / " herein generally indicates that the associated objects before and after are in an "or" relationship.

[0108] Although 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 the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for coordinated optimization of relay protection of a distribution network taking into account new energy, wherein the distribution network is connected to a distributed new energy, characterized in that: The method comprises: Constructing a model framework of the distribution network, the model framework at least including: new energy access characteristics, distribution network topology and distribution network line parameters, wherein the new energy access characteristics include: new energy capacity and new energy access location; Based on the new energy access characteristics, the distribution network topology and the distribution network line parameters, the short-circuit faults that may occur in the distribution network are simulated and calculated to obtain a short-circuit current calculation result; Determine the relay protection device of the distribution network according to the topological structure of the distribution network, and determine the protection setting value of each protection section of the relay protection device according to the short-circuit current calculation result and the protection setting value setting principle, wherein the protection setting value is a threshold value set for realizing relay protection; Establishing an optimization model to update iterative decision variables to obtain an optimal solution for the decision variables, wherein the decision variables include configuration information of the relay protection device, and the configuration information at least includes the protection setting; The configuration of the relay protection device is adjusted according to the optimal solution of the decision variable.

2. The coordinated optimization method for relay protection in distribution network according to claim 1, characterized in that: After determining the protection setting of each protection stage of the relay protection device, the method further includes: Verifying through simulation or experiment whether the protection setting can enable the relay protection device to perform correct action when a fault occurs in the distribution network; If the relay protection device does not perform a correct action, the protection setting is re-determined.

3. The coordinated optimization method for relay protection in distribution network according to claim 1, characterized in that: The method further comprises: When a change in the operating state of the distribution network is detected, the protection constant is recalculated according to a preset algorithm, wherein the change in the operating state of the distribution network includes at least one of the following: output fluctuations of the distributed new energy, changes in the load of the distribution network, or changes in the topology of the distribution network.

4. The coordinated optimization method for relay protection in distribution network according to claim 1, characterized in that: The step of establishing an optimization model to update iterative decision variables and obtain an optimal solution for the decision variables includes: Setting constraints of the decision variables according to the relay protection device; Determining whether the decision variable satisfies the constraint condition; If the decision variable satisfies the constraint condition, judging whether the decision variable satisfies a preset optimal rule according to a total cost function, wherein the total cost function is determined according to the decision variable and is used to measure the total cost required to configure the relay protection device according to the configuration information of the relay protection device contained in the decision variable; If the preset optimal rule is satisfied, determining the decision variable as the optimal solution; If the preset optimal rule is not satisfied, the decision variable is repeatedly adjusted to obtain a new decision variable until the new decision variable satisfies both the constraint condition and the preset optimal rule, and the new decision variable is determined to be the optimal solution.

5. The coordinated optimization method for relay protection of distribution network according to any one of claims 1 to 4, characterized in that: The protection setting value is a current setting value, and the current setting value is a current threshold value set to achieve overcurrent protection.

6. A distribution network relay protection collaborative optimization system taking into account new energy, wherein the distribution network is connected to a distributed new energy, characterized in that: The system comprises: A new energy access impact analysis module is used to construct a model framework of the distribution network, wherein the model framework at least includes: new energy access characteristics, distribution network topology structure and distribution network line parameters, wherein the new energy access characteristics include: new energy capacity and new energy access location; and based on the new energy access characteristics, the distribution network topology structure and the distribution network line parameters, simulate and calculate the short-circuit faults that may occur in the distribution network to obtain the short-circuit current calculation result; A relay protection setting value evaluation module, used to determine the relay protection equipment of the distribution network according to the topological structure of the distribution network, and determine the protection setting value of each protection section of the relay protection equipment according to the short-circuit current calculation result and the protection setting value setting principle, wherein the protection setting value is a threshold value set for realizing relay protection; An operation mode optimization module is used to establish an optimization model to update iterative decision variables to obtain the optimal solution of the decision variables, wherein the decision variables include configuration information of the relay protection device, and the configuration information at least includes the protection setting; and adjust the configuration of the relay protection device according to the optimal solution of the decision variables.

7. The distribution network relay protection collaborative optimization system according to claim 6, characterized in that: After determining the protection setting of each protection stage of the relay protection device, The relay protection setting evaluation module is also used to verify through simulation or experiment whether the protection setting can enable the relay protection device to perform correct action when a fault occurs in the distribution network; if the relay protection device does not perform correct action, the protection setting is re-determined.

8. The distribution network relay protection collaborative optimization system according to claim 6, characterized in that: The system further comprises: A dynamic adjustment control module is used to recalculate the protection constant according to a preset algorithm when a change in the operating state of the distribution network is detected, wherein the change in the operating state of the distribution network includes at least one of the following: output fluctuations of the distributed new energy, changes in the load of the distribution network, or changes in the topology of the distribution network.

9. The distribution network relay protection collaborative optimization system according to claim 6, characterized in that: The step of establishing an optimization model to update iterative decision variables and obtain an optimal solution for the decision variables includes: Setting constraints of the decision variables according to the relay protection device; Determining whether the decision variable satisfies the constraint condition; If the decision variable satisfies the constraint condition, judging whether the decision variable satisfies a preset optimal rule according to a total cost function, wherein the total cost function is determined according to the decision variable and is used to measure the total cost required to configure the relay protection device according to the configuration information of the relay protection device contained in the decision variable; If the preset optimal rule is satisfied, determining the decision variable as the optimal solution; If the preset optimal rule is not satisfied, the decision variable is repeatedly adjusted to obtain a new decision variable until the new decision variable satisfies both the constraint condition and the preset optimal rule, and the new decision variable is determined to be the optimal solution.

10. The distribution network relay protection collaborative optimization system according to any one of claims 6 to 9, characterized in that: The protection setting value is a current setting value, and the current setting value is a current threshold value set to achieve overcurrent protection.

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