Equivalent modeling method and device for power distribution network

Abstract

The invention is suitable for the technical field of power distribution networks, provides a power distribution network equivalent modeling method and device, and particularly relates to a power distribution network containing a distributed power supply. The method comprises the steps of determining a single-machine model of each distributed power supply controller based on the type of each distributed power supply controller in a power distribution network, and performing aggregation processing on the single-machine models of the distributed power supply controllers of the same type to obtain distributed power supply controller equivalent models of different types; obtaining a power distribution network line topology, obtaining the total power loss of the power distribution network based on the topology type corresponding to each node in the line topology, and obtaining a power distribution network line equivalent model according to the total power loss; and constructing a distributed power distribution network equivalent model according to different types of distributed power supply controller equivalent models and power distribution network line equivalent models, and performing power distribution network operation analysis based on the distributed power distribution network equivalent model. According to the method, the work amount and complexity of distributed power distribution network equivalent model construction are reduced, and the problem that the calculation result is not convergent is avoided.

Description

Technical Field

[0001] The present application relates to the technical field of distribution network, and in particular to a distribution network equivalent modeling method and device. Background Art

[0002] With the advancement of the construction of new power systems, the distribution network is gradually transforming into a power network that integrates source, grid, load and storage and is flexibly coupled with the upper power grid. Its functions in promoting the local consumption of distributed power sources and carrying new loads are becoming increasingly prominent. Building an equivalent model of the distribution network containing distributed power sources is crucial for studying the characteristics of distributed power sources, improving power grid reliability, reducing investment and operating costs, and improving emergency response capabilities.

[0003] In the related art, when building an equivalent model of a distribution network containing distributed power sources, a corresponding detailed model is usually constructed for each distributed power controller and the line topology corresponding to each node in the distribution network. However, there are many manufacturers of distributed power controllers, and their control strategies are different. It is a huge project to conduct semi-physical simulation tests and control strategy parameter identification on each type of distributed power controller to obtain the corresponding detailed model, which is computationally complex and does not converge the computer results. Similarly, the distribution network lines have the characteristics of wide coverage, long lines and complex layout. The work of statistically analyzing the detailed structure of the line topology and constructing a detailed model is also particularly huge and arduous, with high computational complexity. This affects the construction of the equivalent model of the distribution network containing distributed power sources, and further affects the operation analysis of the distribution network. Summary of the invention

[0004] In view of this, an embodiment of the present application provides a distribution network equivalent modeling method and device to solve the technical problems of large-scale engineering, high calculation complexity and non-convergence of calculation results when building an equivalent model of a distribution network containing distributed power sources in related technologies.

[0005] In a first aspect, an embodiment of the present application provides a distribution network equivalent modeling method, comprising:

[0006] Obtaining the dynamic output characteristics of each distributed power source controller in the distribution network when a voltage drop fault occurs in the distribution network, and determining the type of each distributed power source controller according to the dynamic output characteristics of each distributed power source controller; the type is determined according to whether the distributed power source controller has a high and low voltage ride-through function;

[0007] Based on the type of each distributed power controller, determine the stand-alone model of each distributed power controller, and aggregate the stand-alone models of distributed power controllers of the same type to obtain equivalent models of distributed power controllers of different types;

[0008] Acquire a line topology of the distribution network, obtain a total power loss of the distribution network based on a topology type corresponding to each node in the line topology, and obtain an equivalent model of the distribution network line according to the total power loss;

[0009] According to different types of distributed power supply controller equivalent models and distribution network line equivalent models, a distributed distribution network equivalent model is constructed to perform distribution network operation analysis based on the distributed distribution network equivalent model.

[0010] In a possible implementation, the dynamic output characteristic includes changes in the active power output by the distributed power controller over time; the types of distributed power controllers include types with a ride-through function and types without a ride-through function;

[0011] The method of determining the type of each distributed power source controller according to the dynamic output characteristics of each distributed power source controller includes:

[0012] For each distributed power controller, detecting whether the output power of the distributed power controller is greater than a preset power threshold during a voltage drop fault in the distribution network;

[0013] If the output power of the distributed power controller is greater than the preset power threshold, determining that the type of the distributed power controller is a type with a ride-through function;

[0014] If the output power of the distributed power controller is less than or equal to the preset power threshold, it is determined that the type of the distributed power controller is a type without a ride-through function.

[0015] In a possible implementation, the single machine model includes the current of the distributed power supply controller in a fault state;

[0016] For the distributed power supply controller with ride-through function, the expression of the single machine model is:

[0017]

[0018] Where V t ≤V L In the fault state, V t is the terminal voltage of the distributed power supply controller, V L is the low voltage ride-through judgment threshold, I PLV1,b and I QLV1,b They are respectively the active current and reactive current of the distributed power controller with ride-through function under fault condition, and is the active power calculation coefficient, and is the reactive power calculation coefficient; and are the initial active current and initial reactive current respectively, and are active current setting value and reactive current setting value respectively; among which, and is an independent parameter, and is the coupling parameter;

[0019] For the distributed power supply controller without ride-through function, the expression of the single machine model is:

[0020] V t ≤V L , I PLV2,b =0,I QLV2,b =0

[0021] In the formula, I PLV2,b and I QLV2,b They are respectively the active current and reactive current of the distributed power supply controller without ride-through function under fault condition.

[0022] In a possible implementation, the single-machine models of distributed power supply controllers of the same type are aggregated to obtain equivalent models of distributed power supply controllers of different types, including:

[0023] Based on the independent parameters in all the stand-alone models of the distributed power controllers with the ride-through function, the aggregated linear independent parameters are obtained, and based on the coupled parameters in all the stand-alone models of the distributed power controllers with the ride-through function, the aggregated linear coupled parameters are obtained;

[0024] According to the aggregated linear independent parameters and the aggregated linear coupling parameters, an equivalent model of the distributed power supply controller with ride-through function is obtained;

[0025] Based on the rated currents in all single-machine models of distributed power controllers without ride-through function, an equivalent model of distributed power controllers without ride-through function is obtained.

[0026] In a possible implementation, the obtaining of the dynamic output characteristics of each distributed power source controller in the distribution network when a voltage drop fault occurs in the distribution network includes:

[0027] For each distributed power controller in the distribution network, a target distributed power controller with the same model as the distributed power controller is connected to the simulation platform;

[0028] The simulation platform is used to simulate the voltage drop fault of the distribution network, and the dynamic output characteristics of the target distributed power supply controller are obtained as the dynamic output characteristics of the distributed power supply controller.

[0029] In a possible implementation manner, obtaining the total power loss of the distribution network based on the topology type corresponding to each node in the line topology includes:

[0030] Based on the structure of the line topology, determine the topology type corresponding to each node in the line topology; wherein the topology type includes a trunk type and a radial type;

[0031] For a node whose corresponding topology type is a trunk type, determining a first power loss according to the sum of an impedance of a wire corresponding to the node and an injected current of the node;

[0032] For a node corresponding to a radial topology type, determining a second power loss according to an impedance of a wire corresponding to the node and an injected current of the node;

[0033] Based on the first power loss and the second power loss, a total power loss of the power distribution network is obtained.

[0034] In a possible implementation, obtaining a distribution network line equivalent model according to the total power loss includes:

[0035] Obtain the load power of the distribution network;

[0036] According to the total power loss of the distribution network, the load power and the current injected into each node, the equivalent impedance of the distribution network line is obtained as the equivalent model of the distribution network line.

[0037] In a possible implementation, the expression of the distribution network line equivalent model is:

[0038]

[0039] In the formula, Z eq is the equivalent impedance of the distribution network line, S Loss is the total power loss of the distribution network, S Load is the load power of the distribution network, I m is the current injected into the mth node, and M is the number of nodes.

[0040] In a second aspect, an embodiment of the present application provides a distribution network equivalent modeling device, comprising:

[0041] An acquisition module is used to obtain the dynamic output characteristics of each distributed power source controller in the distribution network when a voltage drop fault occurs in the distribution network, and determine the type of each distributed power source controller according to the dynamic output characteristics of each distributed power source controller; the type is determined according to whether the distributed power source controller has a high and low voltage ride-through function;

[0042] An aggregation module is used to determine the stand-alone model of each distributed power controller based on the type of each distributed power controller, and aggregate the stand-alone models of distributed power controllers of the same type to obtain equivalent models of distributed power controllers of different types;

[0043] An obtaining module is used to obtain a line topology of a distribution network, obtain a total power loss of the distribution network based on a topology type corresponding to each node in the line topology, and obtain an equivalent model of a distribution network line according to the total power loss;

[0044] The building module is used to build a distributed distribution network equivalent model according to different types of distributed power supply controller equivalent models and distribution network line equivalent models, so as to perform distribution network operation analysis based on the distributed distribution network equivalent model.

[0045] In a possible implementation, the dynamic output characteristic includes changes in the active power output by the distributed power controller over time; the types of distributed power controllers include types with a ride-through function and types without a ride-through function;

[0046] The acquisition module is further used to detect, for each distributed power source controller, whether the output power of the distributed power source controller is greater than a preset power threshold during a voltage drop fault in the power distribution network;

[0047] If the output power of the distributed power controller is greater than the preset power threshold, determining that the type of the distributed power controller is a type with a ride-through function;

[0048] If the output power of the distributed power controller is less than or equal to the preset power threshold, it is determined that the type of the distributed power controller is a type without a ride-through function.

[0049] It can be understood that the beneficial effects of the second aspect mentioned above can be found in the relevant description of the first aspect mentioned above, and will not be repeated here.

[0050] The distribution network equivalent modeling method and device provided in the embodiment of the present application classify the distributed power supply controllers in the distribution network based on whether the distributed power supply controller has the high and low voltage crossing function, aggregate the distributed power supply controllers of the same type into one controller, and obtain the corresponding distributed power supply controller equivalent model. In addition, based on the line topology and power loss consistency principle of the distribution network, the distribution network topology structure is equivalently processed to obtain the distribution network line equivalent model. Afterwards, based on the distributed power supply controller equivalent model and the distribution network line equivalent model, a distributed distribution network equivalent model is constructed.

[0051] The embodiment of the present application utilizes an equivalent model of a distributed power supply controller to replace the detailed model of each distributed power supply controller, and utilizes an equivalent model of a distribution network line to replace the detailed model of the line topology corresponding to each node, thereby effectively solving the problems of large engineering workload and high complexity in building a detailed model and non-convergence of calculation results, reducing the engineering workload and complexity of constructing an equivalent model of a distributed distribution network, and avoiding the problem of non-convergence of calculation results. Subsequently, based on the constructed equivalent model of a distributed distribution network, effective distribution network operation analysis can be performed.

[0052] It is to be understood that the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the present specification. BRIEF DESCRIPTION OF THE DRAWINGS

[0053] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0054] Figure 1 It is a flow chart of a distribution network equivalent modeling method provided by an embodiment of the present application;

[0055] Figure 2 is a schematic diagram of the dynamic output characteristics of a distributed power supply controller provided in an embodiment of the present application;

[0056] Figure 3 It is a schematic diagram of the dynamic output characteristics of a distributed power supply controller with a ride-through function provided in one embodiment of the present application;

[0057] Figure 4 It is a schematic diagram of the dynamic output characteristics of a distributed power supply controller without a ride-through function provided in one embodiment of the present application;

[0058] Figure 5 This is a schematic diagram of a fault ride-through state transition of a distributed power supply controller with a ride-through function provided in an embodiment of the present application;

[0059] Figure 6 It is a schematic diagram of a trunk topology type and a radial topology type;

[0060] Figure 7 It is a structural schematic diagram of a distribution network equivalent modeling device provided in one embodiment of the present application. DETAILED DESCRIPTION

[0061] The present application is described more clearly below in conjunction with specific embodiments. The following embodiments will help those skilled in the art to further understand the effects of the present application, but are not intended to limit the present application in any form. It should be noted that, for those of ordinary skill in the art, several variations and improvements may be made without departing from the concept of the present application. These all fall within the scope of protection of the present application.

[0062] It should be understood that when used in the present specification and the appended claims, the term "comprising" indicates the presence of described features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or combinations thereof.

[0063] It should also be understood that the term “and / or” used in the specification and appended claims refers to any and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0064] In the description of the present application specification and the appended claims, the terms "first", "second", "third", etc. are only used to distinguish the descriptions and cannot be understood as indicating or implying relative importance.

[0065] References to "one embodiment" or "some embodiments" etc. described in the specification of this application mean that one or more embodiments of the present application include specific features, structures or characteristics described in conjunction with the embodiment. Therefore, the statements "in one embodiment", "in some embodiments", "in some other embodiments", "in some other embodiments", etc. that appear in different places in this specification do not necessarily refer to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "including", "comprising", "having" and their variations all mean "including but not limited to", unless otherwise specifically emphasized in other ways.

[0066] In addition, the “plurality” mentioned in the embodiments of the present application should be interpreted as two or more.

[0067] With the idea of ​​reducing the difficulty of building an equivalent model of a distributed distribution network and reducing the complexity of calculations, the inventors have discovered that the distributed power controllers in the distribution network can be classified based on whether the distributed power controllers have high and low voltage crossing functions, and the distributed power controllers of the same type can be aggregated into one controller to obtain the corresponding equivalent model of the distributed power controller. In addition, based on the principle of consistency of the line topology and power loss of the distribution network, the distribution network topology structure is equivalently processed to obtain an equivalent model of the distribution network line. Afterwards, based on the equivalent model of the distributed power controller and the equivalent model of the distribution network line, an equivalent model of the distributed distribution network is constructed.

[0068] In order to make the purpose, technical solutions and advantages of the present invention more clear, specific embodiments will be described below in conjunction with the accompanying drawings.

[0069] Figure 1 1 is a flow chart of a distribution network equivalent modeling method provided by an embodiment of the present application. Figure 1 As shown, the method in the embodiment of the present application may include:

[0070] Step 101: Acquire the dynamic output characteristics of each distributed power source controller in the distribution network when a voltage drop fault occurs in the distribution network, and determine the type of each distributed power source controller according to the dynamic output characteristics of each distributed power source controller.

[0071] Among them, the above types are determined according to whether the distributed power supply controller has the high and low voltage crossing function. The types of distributed power supply controllers include those with crossing function and those without crossing function. The distributed power supply controller with crossing function is a controller with high and low voltage crossing capability, that is, a device that can generate or absorb reactive power. The distributed power supply controller without crossing function is a controller that does not have the high and low voltage crossing capability, that is, when a fault occurs, the device will be disconnected from the grid until the fault is cleared.

[0072] In some embodiments, when obtaining dynamic output characteristics, for each distributed power controller in the distribution network, a target distributed power controller of the same model as the distributed power controller can be connected to a simulation platform. Then, the simulation platform is used to simulate a voltage drop fault in the distribution network, and the obtained dynamic output characteristics of the target distributed power controller are used as the dynamic output characteristics of the distributed power controller.

[0073] Exemplarily, in this embodiment, a virtual simulation model (such as a Simulink simulation model) is built on a simulation platform such as a Real-Time Laboratory (RT-LAB) real-time simulation platform to simulate the distribution network, and the target distributed power controllers with the same model as each distributed power controller in the distribution network are connected to the above-mentioned simulation platform. Specifically, the known parameters such as the analog output, digital output, digital input and analog input of the target distributed power controller are input into the simulation model, and the main circuit topology and photovoltaic components of the target distributed power controller are built on the simulation model, and the parameters are configured and the offline operation is completed to obtain the dynamic output characteristics later. The above-mentioned known parameters can be provided by the manufacturer of the distributed power controller.

[0074] When conducting simulation tests, the simulation model on the simulation platform is used to simulate the voltage drop fault of the distribution network. For example, high and low voltage ride-through disturbance tests of high power, low power, symmetrical power and asymmetrical power are respectively conducted, such as low voltage ride-through disturbance (0%, 20%, 40%, 60%, 80%) and high voltage ride-through disturbance (130%, 120%), and the dynamic output characteristics of the target distributed power controller are obtained as the dynamic output characteristics of the corresponding model of distributed power controller in the distribution network. Among them, the dynamic output characteristics include the change of the active power output of the distributed power controller over time, such as Figure 2 As shown, P g is the active power output by the distributed power supply controller, t1-t2 is the fault time period ①, that is, the time period when the voltage drop fault occurs at the distribution network connection point, t2-t3 is the power recovery starting time period after the fault is cleared ②, and t3-t4 is the power recovery time period ③.

[0075] In some embodiments, when determining the type of each distributed power supply controller, it is possible to detect for each distributed power supply controller whether the output power of the distributed power supply controller is greater than a preset power threshold during a voltage drop fault in the distribution network. If the output power of the distributed power supply controller is greater than the preset power threshold, the type of the distributed power supply controller is determined to be a type with a ride-through function; if the output power of the distributed power supply controller is less than or equal to the preset power threshold, the type of the distributed power supply controller is determined to be a type without a ride-through function.

[0076] In this embodiment, the distributed power controllers in the distribution network are first classified based on whether the distributed power controllers have high and low voltage ride-through capabilities, so as to subsequently determine the corresponding single-machine model and perform aggregation according to the type of distributed power controllers.

[0077] Exemplarily, each distributed power source controller is classified based on the obtained dynamic output characteristics of the distributed power source controller. Figure 3 If the output power P′ of the distributed power controller is greater than the preset power threshold value during the fault period t1-t2, the type of the distributed power controller is determined to be a type with a ride-through function. Here, the preset power threshold value can be set to 0 or a positive number close to 0. Figure 4 If, during the fault time period t1-t2, the output power P′ of the distributed power controller is less than or equal to the preset power threshold, it is determined that the type of the distributed power controller is a type without a ride-through function.

[0078] Step 102: based on the type of each distributed power source controller, determine the stand-alone model of each distributed power source controller, and aggregate the stand-alone models of distributed power source controllers of the same type to obtain equivalent models of distributed power source controllers of different types.

[0079] In this embodiment, a corresponding single-machine model is built based on the impact of different types of distributed power controllers on the load model. The key to the impact of the distributed power controller with ride-through function on the load model lies in its switching operation characteristics. In the case of voltage fluctuations in the distribution network, the distributed power controller with ride-through function provides reactive power support or absorbs reactive power, so its fault ride-through state transfer can refer to Figure 5 :1→2,V t <V L ; 2→1, V t >V L And the distributed power supply controller has no ability to climb after crossing; 2→3, V t >V L And the distributed power controller has the ability to climb after crossing; 3→4, after a calculation step; 4→1, the climbing ends (the power returns to the level before crossing); 4→2, V t <V L Among them, V t is the terminal voltage of the distributed power supply controller, V L It is the low voltage ride-through judgment threshold, usually 0.9pu.

[0080] In normal state, the output characteristic of the distributed power controller is constant power control. In ride-through state, the distributed power controller operates in a specified current control mode. For a distributed power controller with ride-through function, the expression of the single-machine model is:

[0081] V t >V L , I PLV1,a =I e , I QLV1,a =0

[0082]

[0083] Where V t >V L In normal state, V t ≤V L In the fault state, I PLV1,a and I QLV1,a are respectively the active current and reactive current of the distributed power supply controller with ride-through function in normal state, I e is the rated current; I PLV1,b and I QLV1,b They are respectively the active current and reactive current of the distributed power controller with ride-through function under fault condition, and is the active power calculation coefficient, and is the reactive power calculation coefficient; and are the initial active current and initial reactive current respectively, and are respectively the active current setting value and the reactive current setting value, and is the bias parameter (constant); among them, and is an independent parameter, and is the coupling parameter. In this way, the single-machine model of the distributed power controller with ride-through function in normal state and fault state is obtained.

[0084] Optionally, the distributed power controller without ride-through function does not have low voltage ride-through capability. When a low voltage fault occurs, a blocking wave (soft disconnection) phenomenon will occur. After the fault disappears, the power recovery process is a fixed linear recovery. For the distributed power controller without ride-through function, the expression of the single machine model is:

[0085] V t >V L , I PLV2,a =P N / V t , I QLV2,a =0

[0086] V t ≤V L , I PLV2,b =0,I QLV2,b =0

[0087] In the formula, I PLV2,a and I QLV2,a They are respectively the active current and reactive current of the distributed power supply controller without ride-through function in normal state; I PLV2,b and I QLV2,b are respectively the active current and reactive current of the distributed power supply controller without ride-through function under fault condition, P N is the rated power of the distributed power controller. In this way, the single-machine model of the distributed power controller without ride-through function in normal state and fault state is obtained.

[0088] In some embodiments, when obtaining equivalent models of different types of distributed power supply controllers, the following steps may be included:

[0089] S1. Based on the independent parameters in the single-machine model of all distributed power controllers with a through-function, the aggregated linear independent parameters are obtained, and based on the coupling parameters in the single-machine model of all distributed power controllers with a through-function, the aggregated linear coupling parameters are obtained.

[0090] S2. According to the aggregated linear independent parameters and the aggregated linear coupling parameters, an equivalent model of the distributed power supply controller with a ride-through function is obtained.

[0091] S3. Based on the rated currents in all single-machine models of distributed power supply controllers without ride-through function, an equivalent model of the distributed power supply controller without ride-through function is obtained.

[0092] Since there are a large number of distributed power controllers in the distribution network, it takes a long time and a large amount of calculation to build a detailed model for each distributed power control, and the calculation results are not easy to converge. In this embodiment, all single-machine models of distributed power controllers with a ride-through function are aggregated to obtain an equivalent model of a distributed power controller with a ride-through function, and all single-machine models of distributed power controllers without a ride-through function are aggregated to obtain an equivalent model of a distributed power controller without a ride-through function, so that one aggregated distributed power controller with a ride-through function and one aggregated distributed power controller without a ride-through function are used to replace multiple distributed power controllers in the distribution network.

[0093] Exemplarily, for a single-machine model of a distributed power supply controller with a ride-through function, the parameters in the single-machine model are divided into independent parameters and coupled parameters, and are superimposed and aggregated based on the characteristics of each parameter.

[0094] Optional, and As an independent parameter, it can be directly added or weighted averaged in the equivalent algorithm. For a distribution network containing n distributed generation controllers with ride-through function, the capacity of the aggregated distributed generation controllers with ride-through function is:

[0095]

[0096] In the formula, S eq is the capacity of the distributed power controller with ride-through function after aggregation, the subscript eq represents the equal value (i.e., aggregated) parameter, S i is the capacity of the i-th distributed power supply controller with ride-through function.

[0097] Post-aggregation parameters for:

[0098]

[0099] In the formula, is the active current setting value after aggregation, is the active current setting value of the i-th distributed power supply controller with ride-through function.

[0100] Similarly, the aggregated parameters can be obtained

[0101]

[0102] In the formula, is the active current setting value after aggregation, is the reactive current setting value of the i-th distributed power supply controller with ride-through function.

[0103] Post-aggregation parameters for:

[0104]

[0105] Post-aggregation parameters for:

[0106]

[0107] In the formula, and They are respectively the active power calculation coefficient and reactive power calculation coefficient after aggregation, and are respectively the active power calculation coefficient and reactive power calculation coefficient of the i-th distributed power controller with ride-through function, I P0,i and I Q0,i They are the initial active current and initial reactive current of i distributed power supply controllers with ride-through function respectively.

[0108] Optional, and As a coupling parameter, it is a parameter that connects the input and output quantities in the distributed power control characteristics. The electrical quantities related to the above parameters generally have nonlinear characteristics. Taking aggregation as an example, coupling parameters Related parameters V t is a strongly nonlinear variable. During the transient process, the terminal voltage V t,i are different, even if all distributed power controllers with ride-through function in the distribution network All use the same value, equal value It is not a weighted average of all parameters. Therefore, a weak nonlinear variable I is used. QLV Replace V t .

[0109] For I QLV1,b-eq , the approximate requirements for equivalent values ​​are:

[0110]

[0111] Similarly, I PLV1,b-eq The approximate requirements for equivalence are:

[0112]

[0113] In the formula, I PLV1,b-eq and I QLV1,b-eq are respectively the active current and reactive current aggregated by the distributed power controller with ride-through function under fault condition, I PLV1,bu and I QLV1,bu They are respectively the active current and reactive current of the i-th distributed power controller with ride-through function under fault state.

[0114] The relationship between the voltage and current at the terminal of the distributed power controller during low voltage ride-through can be approximately expressed as:

[0115] V POC -V t,i =-I QLV1,bi X i

[0116] V POC -V t,eq =-I QLV1,b-eq X eq

[0117] Where V POC is the voltage at the point of common coupling (POC), V t,i and V t,eq are the terminal voltage of the i-th distributed power controller with ride-through function and the aggregated terminal voltage, X i and X eq They are respectively the reactance from the i-th distributed power controller with ride-through function to the POC point and the reactance after aggregation.

[0118] Will I QLV-eq Combined with the above formula for terminal voltage and current, the parameter K can be obtained: Q1-eq The expression is:

[0119]

[0120] In the formula, K Q1-eq is the first reactive power calculation coefficient after aggregation, K Q1,i is the first reactive power calculation coefficient of the i-th distributed power controller with ride-through function, and A is the intermediate parameter.

[0121] Similarly, the first active power calculation coefficient K after aggregation is P1-eq The calculation process and principle can refer to K Q1-eq The calculation process and principle will not be elaborated here.

[0122] In this way, the equivalent model of the distributed power supply controller with ride-through function can be obtained as follows:

[0123] V t >V L , I PLV1,a-eq =nI r , I QLV1,a-eq =0

[0124]

[0125] Among them, I PLV1,a-eq and I QLV1,a-eq are respectively the active current and reactive current aggregated by the distributed power controller with ride-through function in normal state, I PLV1,b-eq and I QLV1,b-eq They are respectively the active current and reactive current aggregated by the distributed power supply controller with ride-through function under fault condition.

[0126] In this way, the equivalent model of the distributed power supply controller with ride-through function is obtained.

[0127] Exemplarily, for a single-machine model of a distributed power controller without a ride-through function, taking into account the wave blocking phenomenon of the distributed power controller without a ride-through function during a fault period, only the output characteristics of the distributed power controller without a ride-through function during the steady-state period are aggregated. At this time, the steady-state output parameters of the distributed power controller without a ride-through function can be calculated according to independent parameters, and the capacity and current are directly superimposed.

[0128] The equivalent model of the distributed power supply controller without ride-through function is:

[0129]

[0130] V t ≤V L , I PLV2,b-eq =0,I QLV2,b-eq =0

[0131] In the formula, I PLV2,a-eq and I QLV2,a-eq are respectively the active current and reactive current after aggregation of the distributed power supply controller without ride-through function in normal state, I PLV2,b-eq and I QLV2,v-eq They are respectively the active current and reactive current aggregated by the distributed power controller without ride-through function under fault condition, S j is the capacity of the jth distributed generation controller without ride-through function, and m is the number of distributed generation controllers without ride-through function in the distribution network.

[0132] In this way, an equivalent model of the distributed power supply controller without ride-through function is obtained.

[0133] In this embodiment, the equivalent model of the distributed power controller with a ride-through function and the equivalent model of the distributed power controller without a ride-through function are obtained by aggregation, so that hundreds or even more distributed power controllers with a ride-through function in the distribution network are equivalent to an aggregated distributed power controller with a ride-through function and an aggregated distributed power controller without a ride-through function. That is, the equivalent models of different types of distributed power controllers are used to replace the detailed model of each distributed power controller, ensuring the consistency of the steady-state / transient operating points before and after the equivalent, and solving the problem of large engineering workload and high complexity in building detailed models, and non-convergence of calculation results.

[0134] Among them, in the aggregation process, the key parameters closely related to the transient characteristics of the large power grid are accurately extracted, and the key parameters are aggregated to obtain the equivalent model of the distributed power supply controller.

[0135] Step 103: Obtain the line topology of the distribution network, obtain the total power loss of the distribution network based on the topology type corresponding to each node in the line topology, and obtain the distribution network line equivalent model according to the total power loss.

[0136] In this embodiment, the distribution network includes high-voltage, medium-voltage and low-voltage distribution networks, and the line topology of the distribution network is obtained. The line topology includes data such as cable / overhead line model, length, starting point and end point, as well as data of each node in the distribution network. The nodes in the distribution network are the collection points of power flow, such as distribution transformers.

[0137] In some embodiments, when obtaining the total power loss of the distribution network, the topology type corresponding to each node in the line topology can be determined based on the structure of the line topology. For nodes whose corresponding topology type is a trunk type, the first power loss is determined according to the sum of the impedance of the wire corresponding to the node and the injected current of the node. For nodes whose corresponding topology type is a radial type, the second power loss is determined according to the impedance of the wire corresponding to the node and the injected current of the node. Thereafter, based on the first power loss and the second power loss, the total power loss of the distribution network is obtained.

[0138] Among them, see Figure 6 , topology types include trunk type and radial type. Starting from the terminal node in the distribution network, in the order from the terminal node to the upper level node, the topology type corresponding to each node is determined in turn, and the first power loss and the second power loss are calculated.

[0139] For nodes with trunk-type topology, the expression of the first power loss is:

[0140]

[0141] In the formula, S tol_Loss1 is the first power loss, Z kis the impedance of the kth wire segment corresponding to the node, I k The current injected into the node for the kth section of wire can be obtained according to the collection table.

[0142] For nodes with radial topology, the expression of the second power loss is:

[0143]

[0144] In the formula, S tol_Loss2 is the second power loss, Z l is the impedance of the lth wire segment corresponding to the node, I l The current injected into the node for the lth section of wire can be obtained according to the collection table.

[0145] The total power loss of the distribution network S Loss :

[0146] S Loss =∑S tol_Loss1 +∑S tol_Loss2

[0147] In some embodiments, when obtaining the distribution network line equivalent model, the load power of the distribution network can be obtained, and the distribution network line equivalent impedance can be obtained according to the total power loss, load power and current injected into each node of the distribution network as the distribution network line equivalent model.

[0148] Exemplarily, the present embodiment may also obtain the distribution network comprehensive load modeling data, and obtain the load power according to the above comprehensive load modeling data and the preset comprehensive load model. The present embodiment performs equalization on the distribution network line based on the principle of consistent power loss before and after equalization, and the distribution network line equivalent model is consistent with the original model in power before and after equalization, and is consistent with the voltage of the upper transmission network connection point.

[0149] The expression of the distribution network line equivalent model is:

[0150]

[0151] In the formula, Z eq is the equivalent impedance of the distribution network line, S Loss is the total power loss of the distribution network, S Load is the load power of the distribution network, I m is the current injected into the mth node, and M is the number of nodes. In this way, the equivalent model of the distribution network line can be obtained.

[0152] In addition, the above-mentioned embodiment describes the construction of the distribution network line equivalent model when the distribution network line topology information is complete. However, in practice, the distribution network structure is complex, especially the low-voltage distribution network (such as the distribution network in the community, urban streets, industrial parks, etc.) has a wide laying range and long lines, and the line topology information is difficult to obtain completely. In view of the incomplete distribution network line topology information, such as the incomplete low-voltage distribution network line topology information, in this embodiment, the low-voltage distribution network comprehensive load modeling data can be obtained, and the above-mentioned low-voltage distribution network comprehensive load modeling data is input into the preset distribution network loss reduction decision system to obtain the low-voltage distribution network line loss value as the low-voltage distribution network power loss.

[0153] Among them, the preset distribution network loss reduction decision system can collect various electrical parameters in the distribution network in real time, such as current, voltage and power, and process and analyze the above electrical parameters to accurately calculate the network loss situation, that is, to obtain the power loss of the distribution network such as the line loss value of the low-voltage distribution network.

[0154] Since the distribution network line topology information of the medium voltage distribution network and the high voltage distribution network is complete, the method in the above embodiment can be used to calculate the power loss of the medium voltage distribution network and the power loss of the high voltage distribution network. Afterwards, the sum of the power losses of the low voltage, medium voltage and high voltage distribution networks is taken as the total power loss of the distribution network to obtain the total power loss of the distribution network.

[0155] Step 104: construct a distributed distribution network equivalent model according to different types of distributed power source controller equivalent models and distribution network line equivalent models, so as to perform distribution network operation analysis based on the distributed distribution network equivalent model.

[0156] Exemplarily, the distributed distribution network equivalent model is composed of a distributed power source controller equivalent model, a distribution network line equivalent model, a load model, a transformer equivalent impedance model and a grid connection point PCC.

[0157] Optionally, when constructing the equivalent impedance model of the transformer, based on the principle of consistency of the losses before and after the equivalent and the voltage at the connection point with the upper-level transmission network, the impedance of the distribution transformer in the distribution network is calculated equivalently, and the impedance and admittance parameters of the distribution transformer are calculated based on the no-load and short-circuit tests of the transformer. After that, the impedance and admittance parameters of all distribution transformers are aggregated, and a set of equivalent impedance and admittance parameters are used to replace the impedance and admittance parameters of each distribution transformer.

[0158] Exemplarily, relevant data of the distribution transformer such as short-circuit impedance, short-circuit loss, no-load current and no-load loss are obtained, and based on the above relevant data, the resistance, reactance, conductance and susceptance parameters of the distribution transformer are calculated.

[0159] Transformer equivalent impedance model:

[0160]

[0161]

[0162] In the formula, r Ty 、x Ty , G Ty and B Ty are the resistance, reactance, conductance and susceptance parameters of the yth distribution transformer, r Teq 、x Teq , G Teq and B Teq They are the resistance, reactance, conductance and susceptance parameters of the equivalent transformer respectively.

[0163] Exemplarily, in this embodiment, when constructing a load model, an existing simplified distribution network load modeling method can be used, which includes three parts: establishing load data, including the composition of load types, the composition of electrical equipment in each load type, and the characteristics of each electrical equipment, integrating the load data into a general form of load characteristic parameters, including static load parameters and dynamic load parameters, and converting the general form of load characteristic parameters into a load model of the PSD-BPA power system analysis software package. Thus, a load model is obtained.

[0164] Thus, according to the equivalent model of the distributed power controller with a ride-through function, the equivalent model of the distributed power controller without a ride-through function, the equivalent model of the distribution network line, and the equivalent impedance model of the transformer, the load model and the grid connection point obtained in the aforementioned embodiment, the equivalent model of the distributed distribution network can be constructed. Afterwards, the equivalent model of the distributed distribution network can be deployed to the Bonneville Power Administration (BPA) large power grid simulation platform to facilitate the subsequent distribution network operation analysis based on the equivalent model of the distributed distribution network, such as using the equivalent model of the distributed distribution network to perform power grid safety analysis, safety verification, calculate the short-circuit ratio of the substation, etc., to improve the stability of the power grid, or study the characteristics of distributed power sources, improve the reliability of the power grid, reduce investment and operating costs, and improve emergency response capabilities.

[0165] The distribution network equivalent modeling method provided in the embodiment of the present application classifies each distributed power supply controller in the distribution network based on whether the distributed power supply controller has the high and low voltage crossing function, aggregates the distributed power supply controllers of the same type into one controller, and obtains the corresponding distributed power supply controller equivalent model. In addition, based on the line topology and power loss consistency principle of the distribution network, the distribution network topology structure is equivalently processed to obtain the distribution network line equivalent model. Afterwards, based on the distributed power supply controller equivalent model and the distribution network line equivalent model, a distributed distribution network equivalent model is constructed.

[0166] The embodiment of the present application utilizes an equivalent model of a distributed power supply controller to replace the detailed model of each distributed power supply controller, and utilizes an equivalent model of a distribution network line to replace the detailed model of the line topology corresponding to each node, thereby effectively solving the problems of large engineering workload and high complexity in building a detailed model and non-convergence of calculation results, reducing the engineering workload and complexity of constructing an equivalent model of a distributed distribution network, and avoiding the problem of non-convergence of calculation results. Subsequently, based on the constructed equivalent model of a distributed distribution network, effective distribution network operation analysis can be performed.

[0167] It should be understood that the size of the serial numbers of the steps in the above embodiments does not mean the order of execution. The execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0168] Figure 7 Schematic diagram of the structure of a distribution network equivalent modeling device provided in one embodiment of the present application. Figure 7 As shown, the distribution network equivalent modeling device provided in this embodiment may include: an acquisition module 701, an aggregation module 702, a obtaining module 703 and a construction module 704.

[0169] Among them, the acquisition module 701 is used to obtain the dynamic output characteristics of each distributed power supply controller in the distribution network when a voltage drop fault occurs in the distribution network, and determine the type of each distributed power supply controller based on the dynamic output characteristics of each distributed power supply controller; the type is determined based on whether the distributed power supply controller has a high and low voltage crossing function.

[0170] Aggregation module 702 is used to determine the stand-alone model of each distributed power controller based on the type of each distributed power controller, and aggregate the stand-alone models of distributed power controllers of the same type to obtain equivalent models of distributed power controllers of different types.

[0171] The obtaining module 703 is used to obtain the line topology of the distribution network, obtain the total power loss of the distribution network based on the topology type corresponding to each node in the line topology, and obtain the distribution network line equivalent model according to the total power loss.

[0172] The construction module 704 is used to construct a distributed distribution network equivalent model according to different types of distributed power supply controller equivalent models and distribution network line equivalent models, so as to perform distribution network operation analysis based on the distributed distribution network equivalent model.

[0173] Optionally, the dynamic output characteristic includes the change of the active power output by the distributed power supply controller over time; the type of the distributed power supply controller includes a type with a ride-through function and a type without a ride-through function; the acquisition module 701 is further used to:

[0174] For each distributed power controller, detecting whether the output power of the distributed power controller is greater than a preset power threshold during a voltage drop fault in the distribution network;

[0175] If the output power of the distributed power controller is greater than the preset power threshold, determining that the type of the distributed power controller is a type with a ride-through function;

[0176] If the output power of the distributed power controller is less than or equal to the preset power threshold, it is determined that the type of the distributed power controller is a type without a ride-through function.

[0177] Optionally, the aggregation module 702 is further configured to:

[0178] Based on the independent parameters in all the stand-alone models of the distributed power controllers with the ride-through function, the aggregated linear independent parameters are obtained, and based on the coupled parameters in all the stand-alone models of the distributed power controllers with the ride-through function, the aggregated linear coupled parameters are obtained;

[0179] According to the aggregated linear independent parameters and the aggregated linear coupling parameters, an equivalent model of the distributed power supply controller with ride-through function is obtained;

[0180] Based on the rated currents in all single-machine models of distributed power controllers without ride-through function, an equivalent model of distributed power controllers without ride-through function is obtained.

[0181] Optionally, the acquisition module 701 is further used for:

[0182] For each distributed power controller in the distribution network, a target distributed power controller with the same model as the distributed power controller is connected to the simulation platform;

[0183] The simulation platform is used to simulate the voltage drop fault of the distribution network, and the dynamic output characteristics of the target distributed power supply controller are obtained as the dynamic output characteristics of the distributed power supply controller.

[0184] Optionally, the obtaining module 703 is further used for:

[0185] Based on the structure of the line topology, determine the topology type corresponding to each node in the line topology; wherein the topology type includes a trunk type and a radial type;

[0186] For a node whose corresponding topology type is a trunk type, determining a first power loss according to the sum of an impedance of a wire corresponding to the node and an injected current of the node;

[0187] For a node corresponding to a radial topology type, determining a second power loss according to an impedance of a wire corresponding to the node and an injected current of the node;

[0188] Based on the first power loss and the second power loss, a total power loss of the power distribution network is obtained.

[0189] Optionally, the obtaining module 703 is further used for:

[0190] Obtain the load power of the distribution network;

[0191] According to the total power loss of the distribution network, the load power and the injected current of each node, the equivalent impedance of the distribution network line is obtained as the equivalent model of the distribution network line.

[0192] It should be noted that the information interaction, execution process, etc. between the above-mentioned devices / units are based on the same concept as the method embodiment of the present application. Their specific functions and technical effects can be found in the method embodiment part and will not be repeated here.

[0193] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described or recorded in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0194] Those of ordinary skill in the art will appreciate that the templates, units, and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, or a combination of computer software and electronic hardware. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0195] If the module / unit is implemented in the form of a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the present invention implements all or part of the processes in the above-mentioned embodiment method, and can also be completed by instructing the relevant hardware through a computer program. The computer program can be stored in a computer-readable storage medium, and the computer program can implement the steps of the above-mentioned method embodiments when executed by the processor. Among them, the computer program includes computer program code, and the computer program code can be in source code form, object code form, executable file or some intermediate form. The computer-readable medium may include: any entity or device that can carry the computer program code, recording medium, U disk, mobile hard disk, disk, optical disk, computer memory, read-only memory, random access memory, electrical carrier signal, telecommunication signal and software distribution medium.

[0196] The embodiments described above are only used to illustrate the technical solutions of the present invention, rather than to limit the same. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that the technical solutions described in the aforementioned embodiments may still be modified, or some of the technical features may be replaced by equivalents. Such modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention, and should all be included in the protection scope of the present invention.

Claims

1. A distribution network equivalent modeling method, characterized in that: include: Obtaining the dynamic output characteristics of each distributed power source controller in the distribution network when a voltage drop fault occurs in the distribution network, and determining the type of each distributed power source controller according to the dynamic output characteristics of each distributed power source controller; the type is determined according to whether the distributed power source controller has a high and low voltage ride-through function; Based on the type of each distributed power controller, determine the stand-alone model of each distributed power controller, and aggregate the stand-alone models of distributed power controllers of the same type to obtain equivalent models of distributed power controllers of different types; Acquire a line topology of the distribution network, obtain a total power loss of the distribution network based on a topology type corresponding to each node in the line topology, and obtain an equivalent model of the distribution network line according to the total power loss; According to different types of distributed power supply controller equivalent models and distribution network line equivalent models, a distributed distribution network equivalent model is constructed to perform distribution network operation analysis based on the distributed distribution network equivalent model.

2. The distribution network equivalent modeling method according to claim 1, characterized in that: The dynamic output characteristics include the change of the active power output by the distributed power controller over time; the types of distributed power controllers include types with ride-through function and types without ride-through function; The method of determining the type of each distributed power source controller according to the dynamic output characteristics of each distributed power source controller includes: For each distributed power controller, detecting whether the output power of the distributed power controller is greater than a preset power threshold during a voltage drop fault in the distribution network; If the output power of the distributed power controller is greater than the preset power threshold, determining that the type of the distributed power controller is a type with a ride-through function; If the output power of the distributed power controller is less than or equal to the preset power threshold, it is determined that the type of the distributed power controller is a type without a ride-through function.

3. The distribution network equivalent modeling method according to claim 2, characterized in that: The single machine model includes the current of the distributed power supply controller in a fault state; For the distributed power supply controller with ride-through function, the expression of the single machine model is: Where V t ≤V L In the fault state, V t is the terminal voltage of the distributed power supply controller, V L is the low voltage ride-through judgment threshold, I PLV1,b and I QLV1,b They are respectively the active current and reactive current of the distributed power controller with ride-through function under fault condition, and is the active power calculation coefficient, and is the reactive power calculation coefficient; and are the initial active current and initial reactive current respectively, and are active current setting value and reactive current setting value respectively; among which, and is an independent parameter, and is the coupling parameter; For the distributed power supply controller without ride-through function, the expression of the single machine model is: V t ≤V L ,I PLV2,b =0,I QLV2,b =0 In the formula, I PLV2,b and I QLV2,b They are respectively the active current and reactive current of the distributed power supply controller without ride-through function under fault condition.

4. The distribution network equivalent modeling method according to claim 3 is characterized in that: The single-machine models of distributed power supply controllers of the same type are aggregated to obtain equivalent models of distributed power supply controllers of different types, including: Based on the independent parameters in all the stand-alone models of the distributed power controllers with the ride-through function, the aggregated linear independent parameters are obtained, and based on the coupled parameters in all the stand-alone models of the distributed power controllers with the ride-through function, the aggregated linear coupled parameters are obtained; According to the aggregated linear independent parameters and the aggregated linear coupling parameters, an equivalent model of the distributed power supply controller with ride-through function is obtained; Based on the rated currents in all single-machine models of distributed power controllers without ride-through function, an equivalent model of distributed power controllers without ride-through function is obtained.

5. The distribution network equivalent modeling method according to claim 1, characterized in that: The obtaining of the dynamic output characteristics of each distributed power source controller in the distribution network when a voltage drop fault occurs in the distribution network includes: For each distributed power controller in the distribution network, a target distributed power controller with the same model as the distributed power controller is connected to the simulation platform; The simulation platform is used to simulate the voltage drop fault of the distribution network, and the dynamic output characteristics of the target distributed power supply controller are obtained as the dynamic output characteristics of the distributed power supply controller.

6. The distribution network equivalent modeling method according to any one of claims 1 to 5, characterized in that: The obtaining of the total power loss of the distribution network based on the topology type corresponding to each node in the line topology includes: Based on the structure of the line topology, determine the topology type corresponding to each node in the line topology; wherein the topology type includes a trunk type and a radial type; For a node whose corresponding topology type is a trunk type, determining a first power loss according to the sum of an impedance of a wire corresponding to the node and an injected current of the node; For a node corresponding to a radial topology type, determining a second power loss according to an impedance of a wire corresponding to the node and an injected current of the node; Based on the first power loss and the second power loss, a total power loss of the power distribution network is obtained.

7. The distribution network equivalent modeling method according to claim 6, characterized in that: The obtaining of a distribution network line equivalent model according to the total power loss comprises: Obtain the load power of the distribution network; According to the total power loss of the distribution network, the load power and the current injected into each node, the equivalent impedance of the distribution network line is obtained as the equivalent model of the distribution network line.

8. The distribution network equivalent modeling method according to claim 7, characterized in that: The expression of the distribution network line equivalent model is: In the formula, Z eq is the equivalent impedance of the distribution network line, S Loss is the total power loss of the distribution network, S Load is the load power of the distribution network, I m is the current injected into the mth node, and M is the number of nodes.

9. A distribution network equivalent modeling device, characterized in that: include: An acquisition module is used to obtain the dynamic output characteristics of each distributed power source controller in the distribution network when a voltage drop fault occurs in the distribution network, and determine the type of each distributed power source controller according to the dynamic output characteristics of each distributed power source controller; the type is determined according to whether the distributed power source controller has a high and low voltage ride-through function; An aggregation module is used to determine the stand-alone model of each distributed power controller based on the type of each distributed power controller, and aggregate the stand-alone models of distributed power controllers of the same type to obtain equivalent models of distributed power controllers of different types; An obtaining module is used to obtain a line topology of a distribution network, obtain a total power loss of the distribution network based on a topology type corresponding to each node in the line topology, and obtain an equivalent model of a distribution network line according to the total power loss; The building module is used to build a distributed distribution network equivalent model according to different types of distributed power supply controller equivalent models and distribution network line equivalent models, so as to perform distribution network operation analysis based on the distributed distribution network equivalent model.

10. The distribution network equivalent modeling device according to claim 9, characterized in that: The dynamic output characteristics include the change of the active power output by the distributed power controller over time; the types of distributed power controllers include those with a ride-through function and those without a ride-through function; The acquisition module is further used to detect, for each distributed power source controller, whether the output power of the distributed power source controller is greater than a preset power threshold during a voltage drop fault in the power distribution network; If the output power of the distributed power controller is greater than the preset power threshold, determining that the type of the distributed power controller is a type with a ride-through function; If the output power of the distributed power controller is less than or equal to the preset power threshold, it is determined that the type of the distributed power controller is a type without a ride-through function.

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