Method and system for calculating reactive power of variable frequency load

Abstract

The invention discloses a method and system for calculating variable frequency load reactive power, and belongs to the technical field of power system simulation. The method comprises the following steps: determining external parameter data of a to-be-tested variable frequency load under different working conditions; fitting the external parameter data to generate a fitting function; and according to the fitting function, solving reactive power of the variable frequency load to be tested under different working conditions. According to the method, the reactive power of the variable-frequency load can be effectively calculated through data fitting.

Description

Technical Field

[0001] The present invention relates to the technical field of power system simulation, and more specifically, to a method and system for calculating reactive power of variable frequency load. Background Art

[0002] With the high proportion of power electronic equipment and renewable energy input, the stability of the power system has changed. On the load side, controllable and flexible rectification and inversion technology is an important technology for flexible and efficient use of electric energy. Especially in the civilian field, the widespread use of inverters, such as inverter refrigerators, inverter air conditioners and other inverter equipment, has made the load side of the power system gradually develop towards a high proportion of power electronics.

[0003] At present, there are few studies on the calculation method of variable frequency load reactive power. Therefore, it is urgent to model the variable frequency load and seek the calculation method of the inverter reactive power, so as to more accurately analyze the impact of variable frequency load on power grid stability. Summary of the invention

[0004] In view of the above problems, the present invention proposes a method for calculating the reactive power of variable frequency load, comprising:

[0005] Determine the external parameter data of the variable frequency load to be tested under different working conditions;

[0006] Fitting the external parameter data to generate a fitting function;

[0007] According to the fitting function, the reactive power of the variable frequency load to be measured under different working conditions is obtained.

[0008] Optionally, external parameter data includes:

[0009] The effective value of the AC side voltage of the variable frequency load to be tested, the active power consumed by the variable frequency load to be tested, and the reactive power consumed by the variable frequency load to be tested.

[0010] Optionally, fitting the external parameter data includes:

[0011] A space point set is generated according to the external parameter data, and the space point set is fitted using a bivariate polynomial interpolation fitting method.

[0012] Optionally, the method also includes: after adding the fitting function to the electromechanical transient model, using the electromechanical transient model to obtain the simulated reactive power of the variable frequency load to be tested under different working conditions, and using the simulated reactive power to verify the accuracy of the reactive power of the variable frequency load to be tested under different working conditions.

[0013] In another aspect, the present invention further provides a system for calculating reactive power of variable frequency load, comprising:

[0014] A data acquisition unit, used to determine the external parameter data of the variable frequency load to be tested under different working conditions;

[0015] A fitting unit, used for fitting the external parameter data to generate a fitting function;

[0016] The output unit is used to obtain the reactive power of the variable frequency load to be measured under different working conditions according to the fitting function.

[0017] Optionally, external parameter data includes:

[0018] The effective value of the AC side voltage of the variable frequency load to be tested, the active power consumed by the variable frequency load to be tested, and the reactive power consumed by the variable frequency load to be tested.

[0019] Optionally, fitting the external parameter data includes:

[0020] A space point set is generated according to the external parameter data, and the space point set is fitted using a bivariate polynomial interpolation fitting method.

[0021] Optionally, the output unit is also used to: after adding the fitting function to the electromechanical transient model, use the electromechanical transient model to obtain the simulated reactive power of the variable frequency load to be tested under different working conditions, and use the simulated reactive power to verify the accuracy of the reactive power of the variable frequency load to be tested under different working conditions.

[0022] In yet another aspect, the present invention further provides a computing device, comprising: one or more processors;

[0023] a processor for executing one or more programs;

[0024] When the one or more programs are executed by the one or more processors, the above-described method is implemented.

[0025] In yet another aspect, the present invention further provides a computer-readable storage medium having a computer program stored thereon, wherein when the computer program is executed, the method described above is implemented.

[0026] Compared with the prior art, the present invention has the following beneficial effects:

[0027] The present invention provides a method for calculating the reactive power of a variable frequency load, comprising: determining external parameter data of a variable frequency load to be measured under different working conditions; fitting the external parameter data to generate a fitting function; and obtaining the reactive power of the variable frequency load to be measured under different working conditions according to the fitting function. The present invention can effectively calculate the reactive power of the variable frequency load through data fitting. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 is a flow chart of the method of the present invention;

[0029] Figure 2 A schematic diagram of a variable frequency load provided by an embodiment of the present invention;

[0030] Figure 3 A flow chart of a method for calculating reactive power of variable frequency load provided in an embodiment of the present invention;

[0031] Figure 4A A schematic diagram of a variable frequency air conditioner provided in an embodiment of the present invention when the voltage drops to 0.5 pu at an active power of 600 W;

[0032] Figure 4B A schematic diagram of a variable frequency air conditioner provided in an embodiment of the present invention when the voltage drops to 0.75 pu at an active power of 600 W;

[0033] Figure 4C A schematic diagram of a variable frequency air conditioner provided in an embodiment of the present invention when the voltage drops to 0.5 pu at an active power of 900 W;

[0034] Figure 4D A schematic diagram of a variable frequency air conditioner provided in an embodiment of the present invention when the voltage drops to 0.75 pu at an active power of 900 W;

[0035] Figure 5 It is a structural diagram of the system of the present invention. DETAILED DESCRIPTION

[0036] Now, exemplary embodiments of the present invention are described with reference to the accompanying drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. These embodiments are provided to disclose the present invention in detail and completely and to fully convey the scope of the present invention to those skilled in the art. The terms used in the exemplary embodiments shown in the accompanying drawings are not intended to limit the present invention. In the accompanying drawings, the same units / elements are marked with the same reference numerals.

[0037] Unless otherwise specified, the terms (including technical terms) used herein have the commonly understood meanings to those skilled in the art. In addition, it is understood that the terms defined in commonly used dictionaries should be understood to have the same meanings as those in the context of the relevant fields, and should not be understood as idealized or overly formal meanings.

[0038] Embodiment 1:

[0039] The present invention proposes a method for calculating the reactive power of variable frequency load, such as Figure 1 As shown, including:

[0040] Step 1, determining the external parameter data of the variable frequency load to be tested under different working conditions;

[0041] Step 2, fitting the external parameter data to generate a fitting function;

[0042] Step 3: According to the fitting function, the reactive power of the variable frequency load to be measured under different working conditions is obtained.

[0043] Among them, the external parameter data includes:

[0044] The effective value of the AC side voltage of the variable frequency load to be tested, the active power consumed by the variable frequency load to be tested, and the reactive power consumed by the variable frequency load to be tested.

[0045] Wherein, fitting the external parameter data includes:

[0046] A space point set is generated according to the external parameter data, and the space point set is fitted using a bivariate polynomial interpolation fitting method.

[0047] The method also includes: after adding the fitting function to the electromechanical transient model, using the electromechanical transient model to obtain the simulated reactive power of the variable frequency load to be tested under different working conditions, and using the simulated reactive power to verify the accuracy of the reactive power of the variable frequency load to be tested under different working conditions.

[0048] The present invention will be further described below in conjunction with implementation cases:

[0049] Figure 2 FIG. 1 is a schematic diagram of an inverter load equivalent circuit according to a preferred embodiment of the present invention, as shown in FIG. Figure 2 As shown, the variable frequency load includes a diode rectifier DRU, an inverter VSC, an equivalent resistance R and a DC capacitor C from the diode rectifier DRU to the inverter VSC, and a motor M. Among them, the AC side input voltage U ac , the DC side output voltage and current are U dc and i R , the voltage and current of the DC capacitor C are U c and i C , the inverter VSC input current is i dc , the output voltage is U abc , the current output to the motor M is i abc .

[0050] According to the equivalent circuit, an electromechanical transient equation (electromechanical transient model) of the variable frequency load to be measured is established, wherein the electromechanical transient equation includes:

[0051] P=P M +P C (1)

[0052] P C =I C ·U C (2)

[0053] P M =I M ·U C (3)

[0054] I MC =I C +I M (4)

[0055]

[0056] U MA =C st ·U ac (6)

[0057]

[0058] Where P M and I M are respectively the active power consumed by the motor of the variable frequency load to be measured and the current flowing through the motor; P C , U C , I C and C are the charging and discharging power, voltage, current and capacitance value of the DC capacitor of the variable frequency load to be tested respectively; P is the active power consumed by the variable frequency load to be tested; I MC U is the DC side current of the diode rectifier of the variable frequency load to be measured; ac and U MA are the AC side voltage and DC side voltage of the diode rectifier of the variable frequency load to be tested respectively; C st is the conversion multiple of the AC side voltage and the DC side voltage of the diode rectifier of the variable frequency load to be measured, and R is the equivalent resistance value from the diode rectifier of the variable frequency load to be measured to the inverter.

[0059] The specific implementation steps are as follows: Figure 3 As shown, including:

[0060] The external parameter values ​​of the variable frequency load to be measured under different working conditions are obtained, wherein the external parameters include the effective value of the AC voltage of the variable frequency load to be measured, the active power consumed by the variable frequency load to be measured, and the reactive power consumed by the variable frequency load to be measured.

[0061] The active power of the variable frequency load, the effective value of the AC side voltage and the reactive power under different working conditions are fitted with functions to obtain the reactive power expression of the variable frequency load to be measured.

[0062] Obtain the values ​​of external parameters of the variable frequency load to be tested under different working conditions, including:

[0063] Select a plurality of different working conditions (e.g., 10 kinds), and the active power and / or AC side voltage effective value of the variable frequency load operation under each working condition are different;

[0064] The variable frequency load is controlled to operate under different active powers, and the reactive power of the variable frequency load and the effective value of the AC side voltage of the variable frequency load under different working conditions are obtained.

[0065] Among them, under some working conditions, 6 different effective values ​​of the voltage on the AC side of the variable frequency load are selected, such as the effective value of the voltage increases step by step from 0.5pu to 1.0pu in steps of 0.1pu.

[0066] Among them, the active power of the variable frequency load, the effective value of the AC side voltage and the reactive power under different working conditions are fitted to obtain the reactive power expression of the variable frequency load to be measured, that is, the fitting function of the reactive power of the variable frequency load with respect to the active power and the effective value of the AC side voltage, including:

[0067] The active power of the variable frequency load, the effective value of the AC side voltage and the reactive power under different working conditions are fitted to obtain the fitting function of the reactive power of the variable frequency load with respect to the active power and the effective value of the AC side voltage.

[0068] The active power of the variable frequency load is set to x, the effective value of the AC side voltage is set to y, and the reactive power is set to z; a spatial point set (x, y, z) is formed; the point set is fitted using a binary polynomial interpolation fitting method, wherein x and y each have a quadratic term, and the fitting function expression is z=a+bx+cy+dx 2 +exy+fy 2 By fitting the active power of the variable frequency load, the effective value of the AC side voltage and the reactive power under different working conditions, the values ​​of the coefficients in the fitting function can be obtained, and then the fitting function of the reactive power of the variable frequency load with respect to the active power and the effective value of the voltage can be obtained.

[0069] After obtaining the fitting function, add the fitting function to the electromechanical transient model built by the simulation software, and observe the reactive power calculated by the fitting function under other working conditions. Compare whether the reactive power under electromechanical transient is consistent with the reactive power under electromagnetic transient generated by the electromagnetic transient model built by the simulation software.

[0070] Among them, under the conditions of 600W and 900W active power and different variable frequency load AC side voltage effective values, the variable frequency load to be tested is controlled to operate, and the reactive power under electromagnetic transient is obtained. The reactive power obtained under electromagnetic transient and the reactive power under electromechanical transient calculated using the fitting function are displayed in 4A to 4D The blue solid line is the reactive power under electromagnetic transient response, and the green solid line is the reactive power under electromechanical transient response. 4A to 4D It can be seen that the reactive power under electromechanical transient state obtained by fitting function calculation under different working conditions can well correspond to the reactive power under electromagnetic transient state of variable frequency load to be measured, which fully demonstrates the accuracy of the aforementioned steps for calculating the reactive power of variable frequency load to be measured.

[0071] In summary, the variable frequency load modeling and parameter identification method of this embodiment fits the acquired external parameters to obtain the function of the variable frequency load reactive power with respect to the active power and the effective value of the voltage, which can more accurately analyze the reactive power changes in the transient process of the variable frequency load when modeling the actual frequency converter, making the qualitative analysis more reliable.

[0072] Embodiment 2:

[0073] The present invention also proposes a system 200 for calculating reactive power of variable frequency load, such as Figure 5 As shown, including:

[0074] The data acquisition unit 201 is used to determine the external parameter data of the variable frequency load to be tested under different working conditions;

[0075] A fitting unit 202, used for fitting the external parameter data to generate a fitting function;

[0076] The output unit 203 is used to obtain the reactive power of the variable frequency load to be measured under different working conditions according to the fitting function.

[0077] Among them, the external parameter data includes:

[0078] The effective value of the AC side voltage of the variable frequency load to be tested, the active power consumed by the variable frequency load to be tested, and the reactive power consumed by the variable frequency load to be tested.

[0079] Wherein, fitting the external parameter data includes:

[0080] A space point set is generated according to the external parameter data, and the space point set is fitted using a bivariate polynomial interpolation fitting method.

[0081] Among them, the output unit 203 is also used to: after adding the fitting function to the electromechanical transient model, use the electromechanical transient model to obtain the simulated reactive power of the variable frequency load to be tested under different working conditions, and use the simulated reactive power to verify the accuracy of the reactive power of the variable frequency load to be tested under different working conditions.

[0082] The present invention can effectively calculate the reactive power of the variable frequency load through data fitting.

[0083] Embodiment 3:

[0084] Based on the same inventive concept, the present invention also provides a computer device, which includes a processor and a memory, wherein the memory is used to store a computer program, the computer program includes program instructions, and the processor is used to execute the program instructions stored in the computer storage medium. The processor may be a central processing unit (CPU), or other general-purpose processors, digital signal processors (DSP), application-specific integrated circuits (ASIC), field-programmable gate arrays (FPGA) or other programmable logic devices, discrete gates or transistor logic devices, discrete hardware components, etc. It is the computing core and control core of the terminal, which is suitable for implementing one or more instructions, and is specifically suitable for loading and executing one or more instructions in the computer storage medium to implement the corresponding method flow or corresponding functions, so as to implement the steps of the method in the above embodiment.

[0085] Embodiment 4:

[0086] Based on the same inventive concept, the present invention also provides a storage medium, specifically a computer-readable storage medium (Memory), which is a memory device in a computer device for storing programs and data. It is understandable that the computer-readable storage medium here can include both a built-in storage medium in a computer device and an extended storage medium supported by the computer device. The computer-readable storage medium provides a storage space, which stores the operating system of the terminal. In addition, one or more instructions suitable for being loaded and executed by a processor are also stored in the storage space, and these instructions can be one or more computer programs (including program codes). It should be noted that the computer-readable storage medium here can be a high-speed RAM memory or a non-volatile memory, such as at least one disk memory. The processor can load and execute one or more instructions stored in the computer-readable storage medium to implement the steps of the method in the above embodiment.

[0087] It will be appreciated by those skilled in the art that embodiments of the present invention may be provided as methods, systems, or computer program products. Therefore, the present invention may take the form of a complete hardware embodiment, a complete software embodiment, or an embodiment combining software and hardware. Moreover, the present invention may take the form of a computer program product implemented on one or more computer-usable storage media (including but not limited to disk storage, CD-ROM, optical storage, etc.) containing computer-usable program codes. The schemes in the embodiments of the present invention may be implemented in various computer languages, for example, object-oriented programming language Java and literal scripting language JavaScript, etc.

[0088] The present invention is described with reference to flowcharts and / or block diagrams of methods, devices (systems), and computer program products according to embodiments of the present invention. It should be understood that each process and / or block in the flowchart and / or block diagram, as well as the combination of processes and / or blocks in the flowchart and / or block diagram, can be implemented by computer program instructions. These computer program instructions can be provided to a processor of a general-purpose computer, a special-purpose computer, an embedded processor, or other programmable data processing device to produce a machine, so that the instructions executed by the processor of the computer or other programmable data processing device generate instructions for implementing the processes in the flowchart and / or block diagram. Figure 1 A process or multiple processes and / or boxes Figure 1 A device that provides the functions specified in a block or multiple blocks.

[0089] These computer program instructions may also be stored in a computer-readable memory capable of directing a computer or other programmable data processing device to operate in a specific manner, so that the instructions stored in the computer-readable memory produce an article of manufacture comprising an instruction device, which implements the process Figure 1 A process or multiple processes and / or boxes Figure 1 A function specified in one or more boxes.

[0090] These computer program instructions can also be loaded onto a computer or other programmable data processing device so that a series of operating steps are executed on the computer or other programmable device to produce a computer-implemented process, thereby providing instructions for implementing the process. Figure 1 A process or multiple processes and / or boxes Figure 1 A step that specifies a function in one or more boxes.

[0091] Although the preferred embodiments of the present invention have been described, those skilled in the art may make other changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0092] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A method for calculating reactive power of variable frequency load, characterized in that: include: Determine the external parameter data of the variable frequency load to be tested under different working conditions; Fitting the external parameter data to generate a fitting function; According to the fitting function, the reactive power of the variable frequency load to be measured under different working conditions is obtained.

2. The method according to claim 1, characterized in that The external parameter data includes: The effective value of the AC side voltage of the variable frequency load to be tested, the active power consumed by the variable frequency load to be tested, and the reactive power consumed by the variable frequency load to be tested.

3. The method according to claim 1, characterized in that The fitting of the external parameter data comprises: A space point set is generated according to the external parameter data, and the space point set is fitted using a bivariate polynomial interpolation fitting method.

4. The method according to claim 1, characterized in that The method also includes: after adding the fitting function to the electromechanical transient model, using the electromechanical transient model to obtain the simulated reactive power of the variable frequency load to be measured under different working conditions, and using the simulated reactive power to verify the accuracy of the reactive power of the variable frequency load to be measured under different working conditions.

5. A system for calculating reactive power of variable frequency load, characterized in that: include: A data acquisition unit, used to determine the external parameter data of the variable frequency load to be tested under different working conditions; A fitting unit, used for fitting the external parameter data to generate a fitting function; The output unit is used to obtain the reactive power of the variable frequency load to be measured under different working conditions according to the fitting function.

6. The system according to claim 5, characterized in that The external parameter data includes: The effective value of the AC side voltage of the variable frequency load to be tested, the active power consumed by the variable frequency load to be tested, and the reactive power consumed by the variable frequency load to be tested.

7. The system according to claim 5, characterized in that The fitting of the external parameter data comprises: A space point set is generated according to the external parameter data, and the space point set is fitted using a bivariate polynomial interpolation fitting method.

8. The system according to claim 5, characterized in that The output unit is also used to: after adding the fitting function to the electromechanical transient model, use the electromechanical transient model to obtain the simulated reactive power of the variable frequency load to be tested under different working conditions, and use the simulated reactive power to verify the accuracy of the reactive power of the variable frequency load to be tested under different working conditions.

9. A computer device, characterized in that: include: one or more processors; a processor for executing one or more programs; When the one or more programs are executed by the one or more processors, the method according to any one of claims 1 to 4 is implemented.

10. A computer-readable storage medium, characterized in that: A computer program is stored thereon, and when the computer program is executed, the method according to any one of claims 1 to 4 is implemented.

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