Method and system for identifying power load component proportions using large disturbance data

Abstract

This invention provides a method and system for identifying the proportion of power load components using large disturbance data. The method first acquires dynamic response data of the power load when a large disturbance occurs in the power system causing a voltage drop. Then, based on the voltage drop and active power change during the voltage drop period, the steady-state active power of the static load is calculated. Next, the dynamic response containing only motor loads and power electronic interface loads is separated from the total load response. Subsequently, the steady-state active power of the power electronic interface load is determined based on the separation result of the motor load active power response and its highest fitting accuracy. Then, the steady-state active power of the static load and the power electronic interface load is subtracted from the total steady-state active power of the load to obtain the steady-state active power of the motor load. Finally, the proportions of the steady-state active power of the static load, the power electronic interface load, and the motor load are calculated.

Description

Technical Field

[0001] This invention relates to the field of smart grid technology, and in particular to the identification of power system load components in power systems. Specifically, it relates to a method and system for identifying the proportion of power load components using large disturbance data. Background Technology

[0002] Electrical load is a crucial component of a power system, encompassing all electrical equipment. To conduct power system simulation studies, it is necessary to establish an electrical load model. Furthermore, the accuracy of power system simulation analysis heavily depends on the accurate establishment of the load model; therefore, understanding the components of the electrical load is essential for creating an accurate load model.

[0003] The most commonly used classical load model in power system simulation mainly consists of parallel connections of motors and static loads. The motor component has a significant impact on the dynamic characteristics of the load; therefore, setting different motor proportions in the load model will significantly affect the simulation results of the power system. This has been confirmed through the inversion of power grid accidents. Currently, there are two main methods for obtaining the motor proportion in classical load models. One method calculates the motor proportion by statistically analyzing the composition of electrical equipment. However, this method actually yields the capacity ratio of motors, not the proportion of actual power consumption by the motors. Only online statistical synthesis methods based on smart meters can potentially obtain the actual power proportion of the motor load. The other method is based on large disturbance data, simultaneously identifying the motor proportion and other key parameters in the load model. Since there are numerous parameters in the load model, only some key parameters are involved in the identification; therefore, the accuracy of the motor proportion identification is affected by the accuracy of other parameters in the load model.

[0004] The composition of electrical loads has been constantly changing with the development of power systems. In recent years, more and more equipment has been connected to the grid through power electronics technology. Since neither static load models nor motor models can accurately describe the dynamic characteristics of power-electronic loads, some scholars have researched and proposed simplified models for power electronic interface loads. Therefore, to accurately characterize the current dynamic characteristics of electrical loads, the load model should include three load components: motors, static loads, and power electronic interface loads. Considering that constant power loads in static loads are usually loads using power electronic interfaces, and since power electronic interface loads will be represented by an independent model, constant power loads are no longer considered in static loads. Constant current loads in static loads mainly represent loads such as electric arc furnaces in the metallurgical industry. Since constant current equipment accounts for a small proportion of the power system, in most cases, static loads only consider constant impedance loads.

[0005] When using load models, the typical parameter values ​​of each component are usually kept constant. The time-varying nature of the load model is mainly reflected by changing the proportions of the load components. Therefore, accurately determining the proportions of load components is crucial for establishing an accurate load model. Currently, apart from online statistical synthesis methods, which offer relatively accurate results in determining the proportions of load components, overall identification methods cannot accurately identify the proportions of the three types of load components mentioned above. Summary of the Invention

[0006] The purpose of this invention is to propose a method for identifying the proportion of electrical load components using large disturbance data, which is used to obtain the proportion of three load components in the electrical load: motor, static load (constant impedance load) and power electronic interface load through measurement methods.

[0007] A first aspect of the present invention provides a method for identifying the proportion of electrical load components using large disturbance data, comprising the following steps:

[0008] Step 1: Obtain dynamic response data of the power load when a large disturbance occurs in the power system causing a voltage drop. This involves recording the load dynamic response at the load node under voltage drop conditions, including the voltage change U(t) and the active power change P. Σ (t);

[0009] Step 2: Calculate the steady-state power P of the constant impedance load based on the voltage drop and active power change during the fault duration. Z0 ;

[0010] Step 3, according to formula P Z (t)=P Z0 (U(t) / U0) 2 Calculate the dynamic response P of the constant impedance load. Z (t), in the total load response P Σ The dynamic response P of the constant impedance load is subtracted from (t). Z (t), separating the dynamic response P containing only the motor and power electronic interface load. ME (t), i.e., P ME (t)=P Σ (t)-P Z (t);

[0011] Step 4: Based on the motor load active power response P M The separation results of (t) and its highest fitting accuracy determine the steady-state active power P of the power electronic interface load. E0 ;

[0012] Step 5: The total steady-state active power P of the load... Σ0 The steady-state active power P minus the static loadZ0 Steady-state active power P of the power electronic interface load E0 The steady-state active power P of the motor load is obtained. M0 That is, P M0 =P Σ0 -P Z0 -P E0 ;

[0013] Step 6: Steady-state active power P based on three components: static load, power electronic interface load, and motor load. Z0 P E0 and P M0 Calculate its proportion p. Z p E and p M .

[0014] It should be understood that since constant current electrical equipment accounts for a small proportion of the power system, in most cases only constant impedance loads are considered as static loads. Therefore, in this invention, only constant impedance loads are considered as static loads. In various embodiments of this invention, static load specifically refers to constant impedance loads.

[0015] Combining the above technical solutions, when the voltage at a load node drops, the active power of the static load also drops, and the active power remains constant during the voltage drop. The active power of the motor load first experiences a downward impact, then rapidly recovers and undergoes a decaying oscillation process, with the active power after the oscillation subsides approaching the level before the fault. The active power of the power electronic interface load first drops rapidly, then quickly recovers to the level before the fault. This invention fully utilizes the differences in the dynamic response characteristics of the three load components when a large disturbance event occurs in the power system, causing a voltage drop at the load node, to identify their component proportions.

[0016] Compared with existing technologies, the method for identifying the proportion of power load components using large disturbance data proposed in this invention obtains the proportion of three load components in the power load—motor, static load (constant impedance load), and power electronic interface load—through measurement methods. The power load component proportion identification method only needs to measure the voltage drop process and the corresponding active power change process of the load node. The load component proportion identification process does not involve the identification of any load model parameters, thus solving the deficiency of existing load model overall measurement methods that cannot identify the proportion of the three components—static load, power electronic interface load, and motor load.

[0017] A second aspect of the present invention also provides a system for identifying the proportion of electrical load components using large disturbance data, comprising:

[0018] One or more processors;

[0019] The memory stores operable instructions that, when executed by the one or more processors, cause the one or more processors to perform operations, including the aforementioned process of identifying the proportion of electrical load components using large disturbance data.

[0020] A third aspect of the invention also provides a computer-readable medium for storing software, the software comprising instructions executable by one or more processors, the instructions causing the one or more processors to perform operations including the aforementioned process of identifying the proportion of electrical load components using large disturbance data.

[0021] It should be understood that all combinations of the foregoing concepts and the additional concepts described in more detail below may be considered part of the inventive subject matter of this disclosure, provided that such concepts do not contradict each other. Furthermore, all combinations of the claimed subject matter are considered part of the inventive subject matter of this disclosure.

[0022] The foregoing and other aspects, embodiments, and features of the teachings of the present invention will be more fully understood from the following description in conjunction with the accompanying drawings. Other additional aspects of the invention, such as features and / or beneficial effects of exemplary embodiments, will become apparent from the following description or may be learned through practice of specific embodiments according to the teachings of the present invention. Attached Figure Description

[0023] The accompanying drawings are not intended to be drawn to scale. In the drawings, every identical or nearly identical component shown in each figure may be indicated by the same reference numeral. For clarity, not every component is labeled in each figure.

[0024] Figure 1 This is a flowchart illustrating the method for identifying the proportion of power load components using large disturbance data according to an embodiment of the present invention.

[0025] Figure 2 This is a schematic diagram of a test system according to an example of the present invention, which includes static load, power electronic interface load and motor load.

[0026] Figure 3 It is a schematic diagram of the entire process of recording a large disturbance.

[0027] Figure 4 It is a dynamic response diagram containing only two types of loads: motor and power electronic interface load.

[0028] Figure 5 It is a fitted graph of the isolated dynamic response of the motor and the 8th order transfer function. Detailed Implementation

[0029] To better understand the technical content of the present invention, specific embodiments are described below in conjunction with the accompanying drawings.

[0030] Various aspects of the invention are described in this disclosure with reference to the accompanying drawings, which illustrate numerous illustrative embodiments. The embodiments of this disclosure are not necessarily intended to encompass all aspects of the invention. It should be understood that the various concepts and embodiments described above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed herein are not limited to any particular implementation. Furthermore, some aspects of the invention disclosed may be used alone or in any suitable combination with other aspects of the invention disclosed.

[0031] Combination Figures 1-5 For example, the method for identifying the proportion of power load components using large disturbance data proposed in this invention includes the following steps:

[0032] Step 1: Obtain dynamic response data of the power load when a large disturbance occurs in the power system causing a voltage drop. This involves recording the load dynamic response at the load node under voltage drop conditions, including the voltage change U(t) and the active power change P. Σ (t);

[0033] Step 2: Calculate the steady-state power P of the constant impedance load based on the voltage drop and active power change during the fault duration. Z0 ;

[0034] Step 3, according to formula P Z (t)=P Z0 (U(t) / U0) 2 Calculate the dynamic response P of the constant impedance load. Z (t), in the total load response P Σ The dynamic response P of the constant impedance load is subtracted from (t). Z (t), separating the dynamic response P containing only the motor and power electronic interface load. ME (t), i.e., P ME (t)=P Σ (t)-P Z (t);

[0035] Step 4: Based on the motor load active power response P M The separation results of (t) and its highest fitting accuracy determine the steady-state active power P of the power electronic interface load. E0 ;

[0036] Step 5: The total steady-state active power P of the load... Σ0 The steady-state active power P minus the static load Z0Steady-state active power P of the power electronic interface load E0 The steady-state active power P of the motor load is obtained. M0 That is, P M0 =P Σ0 -P Z0 -P E0 ;

[0037] Step 6: Steady-state active power P based on three components: static load, power electronic interface load, and motor load. Z0 P E0 and P M0 Calculate its proportion p. Z p E and p M .

[0038] In embodiments of the present invention, the power load component ratio refers to the proportion of the steady-state active power of constant impedance load, power electronic interface load, and motor load to the total steady-state active power of the load. The method for calculating the proportion of the three load components is as follows:

[0039] p Z =P Z0 / P Σ0 ;

[0040] p E =P E0 / P Σ0 ;

[0041] p M =P M0 / P Σ0 ;

[0042] The load component ratio refers to the proportion of steady-state active power of this type of load to the total active power of the load.

[0043] In step 2, the steady-state power P of the constant impedance load is calculated. Z0 The formula is:

[0044] P Z0 =ΔP / [(U / U0) 2 -1];

[0045] Where ΔP is the voltage drop in active power of the load during the duration of the fault, measured at the load node; U is the average voltage of the load node during the duration of the fault; and U0 is the steady-state voltage of the load node before the fault.

[0046] In step 4, the dynamic response P of the power electronic interface load is calculated. E The formula used for (t) is a piecewise exponential function, expressed as:

[0047]

[0048] The typical parameter used is T. f =1, λ=0.019, k=1, P onset =0.463.

[0049] In step 4, the motor response P is used for fitting. M The model of (t) adopts the 8th order transfer function model G8(s), which is consistent with the complete mathematical model of the three-phase asynchronous motor. The fitted response process is from the data point after the voltage drop to the data point before the voltage recovers.

[0050] In step 4, the steady-state power P of the power electronic interface load is determined. E0 The methods include:

[0051] Find an optimal P E0 Numerical analysis was used to fit the 8th-order transfer function G8(s) to the dynamic response P of the motor under load. M The error of (t) is the smallest.

[0052] It should be understood that, in combination Figure 1 The identification methods shown in the example further include:

[0053] Based on the fixed error of the identification algorithm, the component proportions of the motor load and the power electronic interface load are corrected to obtain the corrected component proportions.

[0054] As an optional embodiment, the correction of the component proportions of the motor load and the power electronic interface load includes:

[0055] When using known load components, a correction factor α is determined based on the direction and proportion of the deviation between the identification results and the true values. When the identification method is applied to other unknown load components, the component proportion of the motor load is first corrected to αp. M Then, the proportion of the power electronic interface load is corrected to p. E =1-p Z -αp M .

[0056] Below, we will further elaborate and explain the implementation process of the aforementioned embodiments with specific examples.

[0057] Step 1: Obtain dynamic response data of the power load when a large disturbance occurs in the power system causing a voltage drop. This involves recording the load's dynamic response under voltage drop conditions at the load nodes using a fault recorder or PMU device, primarily the voltage change U(t) and the active power change P. Σ (t).

[0058] This embodiment is based on a test system built using MATLAB software. The specific model structure diagram is shown below. Figure 2 As shown. Static load, power electronic interface load, and motor load are connected to the same node. The motor model is directly provided by MATLAB software; detailed explanations can be found in the MATLAB help documentation and will not be repeated here. In the system, the proportion of the three load components in the total load is changed by altering the steady-state active power of the power electronic interface load and the static load. In the experiment, the active power ratios of the static load, power electronic interface load, and motor load were set to 0.350, 0.350, and 0.300, respectively. In the model, the fault resistance R is set. ON The resistance is 41Ω, corresponding to a voltage drop of approximately 5%. The fault begins at 1 second, clears at 1.5 seconds, and lasts for 0.5 seconds.

[0059] Acquire large disturbance data at the nodes connected to the power load, including voltage U(t) and active power P of the total load on the bus. Σ (t). The aforementioned large disturbance data can be obtained from one of the electrical measuring devices installed on the busbar connected to the power load, such as a fault recorder, phasor measurement unit, or power quality detector. The entire recorded large disturbance process is as follows: Figure 3 This includes data recordings of voltage and active power.

[0060] Step 2: Calculate the steady-state power P of the static load (constant impedance load) based on the voltage drop and active power change during the voltage dip fault period. Z0 .

[0061] Furthermore, calculate the steady-state power P of the static load (constant impedance load). Z0 The formula is P Z0 =ΔP / [(U / U0) 2 -1], where ΔP is the decrease in active power of the load during the duration of the voltage drop fault measured at the load node, U is the average voltage of the load node during the duration of the fault, and U0 is the steady-state value of the load node voltage before the fault.

[0062] Based on the data of the entire large disturbance process recorded in step 1, the steady-state voltage U0 of the load node before the fault, the average voltage U of the load node during the fault duration, and the decrease in active power ΔP of the load during the fault duration are obtained as follows:

[0063] U0=1p.u.; U=0.95pu; ΔP=-0.0346pu

[0064] The steady-state power P of the constant impedance load is calculated based on this step. Z0 =0.3524 pu.

[0065] Step 3: According to formula P Z (t)=P Z0 (U(t) / U0) 2 Calculate the dynamic response P of the constant impedance load. Z (t), in the total load response P Σ Subtract P from (t) Z (t), separating the dynamic response P containing only the motor and power electronic interface load. ME (t), i.e., P ME (t)=P Σ (t)-P Z (t).

[0066] The dynamic response diagram for loads containing only electric motors and power electronic interface loads is shown below. Figure 4 As shown.

[0067] Step 4: Based on the motor load active power response P M The separation results of (t) and its highest fitting accuracy determine the steady-state active power P of the power electronic interface load. E0 .

[0068] Furthermore, the dynamic response P of the power electronic interface load is calculated. E (t) uses a piecewise exponential function: The typical parameter used is T f =1, λ=0.019, k=1, P onset =0.463.

[0069] Furthermore, from P ME The dynamic response of the motor load P is separated from (t) M The method of (t) is from P ME The dynamic response P of (t) after deducting the power electronic interface load E (t), i.e., P M (t)=P ME (t)-P E (t).

[0070] Furthermore, it is used to fit the motor response P M The model of (t) is an 8th-order transfer function model G8(s), whose model order is consistent with the complete mathematical model of a three-phase asynchronous motor. The fitted response process is from the data point after the voltage drop to the data point before the voltage recovers.

[0071] Furthermore, the steady-state power P of the power electronic interface load was determined. E0 The method is to find an optimal P E0 Numerical analysis was used to fit the 8th-order transfer function G8(s) to the dynamic response P of the motor under load.M The error of (t) is the smallest.

[0072] Based on this step, the steady-state power P of the constant impedance load is identified. E0 =0.3618pu, the dynamic response P of the separated motor M (t), with U(t) as input, P M (t) represents the output. An 8th-order transfer function G8(s) is used to fit the dynamic response of the motor, with a time step of 0.005s and a fit of 99.95%. The fitted response process is from one data point after a voltage drop to the data point before the voltage recovers. The specific fitted graph is shown below. Figure 5 As shown.

[0073] Step 5: The total steady-state active power P of the load... Σ0 The steady-state active power P minus the static load Z0 Steady-state active power P of the power electronic interface load E0 The steady-state active power P of the motor load is obtained. M0 That is, P M0 =P Σ0 -P Z0 -P E0 .

[0074] The steady-state power P of the constant impedance load is calculated based on this step. M0 =0.0672pu.

[0075] Step 6: Steady-state active power P of the three components: static load, power electronic interface load, and motor load. Z0 P E0 and P M0 Calculate its proportion p Z p E and p M .

[0076] Furthermore, the method for calculating the proportion of the three load components is p Z =P Z0 / P Σ0 p E =P E0 / P Σ0 and p M =P M0 / P Σ0 The load component ratio refers to the proportion of the steady-state active power of this type of load to the total active power of the load.

[0077] The calculated ratios of static load, power electronic interface load, and motor load are 0.353, 0.362, and 0.289, respectively. Compared with the actual ratios of these three loads (0.350, 0.350, and 0.300), the absolute errors are -0.003, 0.012, and -0.011, respectively.

[0078] In a further embodiment, when conditions permit, the component ratio of the motor load can be corrected first based on the fixed error of the identification algorithm, and then the component ratio of the power electronic interface load can be corrected, thereby further improving the identification accuracy of the load component ratio.

[0079] As an optional example, a specific method for correcting the component ratio of motor load and power electronic interface load is as follows: When using certain known load components, a correction factor α is determined based on the direction and proportion of the deviation between the identification result and the true value. When the identification method is applied to other unknown load components, the component ratio of the motor load is first corrected to αp. M Then, the proportion of the power electronic interface load is corrected to p. E =1-p Z -αp M .

[0080] In one example, the direction and proportion of the deviation between the identification results and the true values ​​are obtained based on multiple sets of experiments. For example, a correction factor α = 1.05 is obtained. After correction, the motor load ratio is p'. M =0.304, the power electronic interface load ratio is p E =0.349, and the absolute errors of the ratio of motor load and power electronic load after correction are 0.004 and -0.001, respectively.

[0081] In summary, the method for identifying the proportion of power load components using large disturbance data proposed in this invention uses load dynamic response data when a power system experiences a large disturbance. It identifies the proportion of these three load components based on the differences in the dynamic response characteristics of static load, power electronic interface load, and motor load under large disturbances. This method does not require simultaneous identification of other load model parameters and has high identification accuracy. It solves the problem that previous load model overall measurement methods could not identify the proportion of the three load components, which is of great significance for establishing accurate load models.

[0082] In conjunction with the above implementation of the method for identifying the proportion of power load components using large disturbance data, an embodiment of the present invention also proposes a system for identifying the proportion of power load components using large disturbance data, comprising: one or more processors and a memory. The memory is configured to store operable instructions, the execution of which causes the one or more processors to perform operations, including the flow of the method for identifying the proportion of power load components using large disturbance data as described in any of the foregoing embodiments.

[0083] In conjunction with the above implementation of the method for identifying the proportion of power load components using large disturbance data, an embodiment of the present invention also proposes a computer-readable medium for storing software, the software including instructions executable by one or more processors, the execution of which causes the one or more processors to perform operations including the flow of the method for identifying the proportion of power load components using large disturbance data as described in any of the foregoing embodiments.

[0084] While the present invention has been disclosed above with reference to preferred embodiments, it is not intended to limit the invention. Those skilled in the art can make various modifications and refinements without departing from the spirit and scope of the invention. Therefore, the scope of protection of the present invention shall be determined by the claims.

Claims

1. A method for identifying the proportion of electrical load components using large disturbance data, characterized in that, Includes the following steps: Step 1: Obtain dynamic response data of the power load when a large disturbance occurs in the power system causing a voltage drop. This involves recording the load dynamic response at the load node under voltage drop conditions, including the voltage change U(t) and the active power change P. Σ (t); Step 2: Calculate the steady-state power P of the constant impedance load based on the voltage drop and active power change during the fault duration. Z0 ; Step 3: According to formula P Z (t)=P Z0 (U(t) / U0) 2 Calculate the dynamic response P of the constant impedance load. Z (t), in the change of active power P Σ The dynamic response P of the constant impedance load is subtracted from (t). Z (t), separating the dynamic response P containing only the motor and power electronic interface load. ME (t), i.e., P ME (t)=P Σ (t)-P Z (t); Step 4: Based on the motor load active power response P M The separation results of (t) and its highest fitting accuracy determine the steady-state active power P of the power electronic interface load. E0 ; Step 5: The total steady-state active power P of the load... Σ0 The steady-state power P of the constant impedance load is subtracted from the constant impedance load. Z0 Steady-state active power P of the power electronic interface load E0 The steady-state active power P of the motor load is obtained. M0 That is, P M0 =P Σ0 -P Z0 -P E0 ; Step 6: Steady-state active power P based on three components: constant impedance load, power electronic interface load, and motor load. Z0 P E0 and P M0 Calculate its proportion p. Z p E and p M ; In step 2, the steady-state power P of the constant impedance load is calculated. Z0 The formula is: P Z0 =ΔP / [(U / U0) 2 -1]; Where ΔP is the drop in active power of the load during the duration of the voltage dip fault measured at the load node, U is the average voltage of the load node during the duration of the fault, and U0 is the steady-state value of the load node voltage before the fault. In step 4, the active power response P of the motor load is used for fitting. M The model of (t) adopts the 8th order transfer function model G8(s), which is consistent with the complete mathematical model of the three-phase asynchronous motor. The fitted response process is from the data point after the voltage drop to the data point before the voltage recovers. In step 4, the steady-state active power P of the power electronic interface load is determined. E0 The methods include: Find an optimal P E0 The numerical values ​​are used to fit the 8th-order transfer function G8(s) to the active power response P of the motor under load. M The error of (t) is the smallest.

2. The method for identifying the proportion of power load components using large disturbance data according to claim 1, characterized in that, In step 6, the steady-state active power of the constant impedance load, the power electronic interface load, and the motor load accounts for the proportion of the total steady-state active power of the load.

3. The method for identifying the proportion of power load components using large disturbance data according to claim 1, characterized in that, The method further includes: Based on the fixed error of the identification algorithm, the component proportions of the motor load and the power electronic interface load are corrected to obtain the corrected component proportions.

4. The method for identifying the proportion of power load components using large disturbance data according to claim 3, characterized in that, The corrections shown for the component proportions of the motor load and the power electronic interface load include: When using known load components, a correction factor α is determined based on the direction and proportion of the deviation between the identification results and the true values. When the identification method is applied to unknown load components, the component proportion of the motor load is first corrected to αp. M Then, the proportion of the power electronic interface load is corrected to p. E =1-p Z -αp M .

5. A system for identifying the proportion of electrical load components using large disturbance data, characterized in that, include: One or more processors; The memory stores operable instructions that, when executed by the one or more processors, cause the one or more processors to perform operations, including the process of the method for identifying the proportion of electrical load components using large disturbance data as described in any one of claims 1-4.

6. A computer-readable medium for storing software, characterized in that, The software includes instructions executable by one or more processors, which, upon execution, cause the one or more processors to perform operations including the process of the method for identifying the proportion of electrical load components using large disturbance data as described in any one of claims 1-4.

Images