A method and device for quickly detecting the optimal efficiency point of a variable frequency motor system

Abstract

The present invention discloses a method and device for quickly detecting the optimal efficiency point of a variable frequency motor system, which belongs to the technical field of motor system detection, and includes: initializing the variable frequency motor system; selecting an initial test point, and obtaining a rough search range based on the initial test point; performing efficiency tests on each test point within the rough search range, obtaining the optimal efficiency of the current range and determining whether to update the global optimal efficiency; if updated, obtaining a high efficiency area based on the updated global optimal efficiency; after subdividing the high efficiency area into grids, testing each refined grid test point; if the change in the efficiency value meets the preset requirements, outputting the global optimal efficiency and the corresponding torque value and speed value. The present invention can adaptively adjust the torque and speed range, step size and test point duration, and allows for customized search ranges and convergence conditions; reduces the test probability of non-efficient working conditions, while significantly improving the test accuracy of efficient working conditions, and effectively optimizes detection efficiency and accuracy.

Description

Technical Field

[0001] The present invention belongs to the technical field of motor system detection, and in particular relates to a method and a device for quickly detecting an optimum efficiency point of a variable frequency motor system. Background Art

[0002] Variable frequency motor drive systems are widely used in industrial production, especially in scenarios where precise speed regulation is required, such as pumps, fans, compressors and other equipment, showing significant energy-saving and consumption-reducing effects. The operating efficiency of variable frequency motors is closely related to the "speed-load" operating point of the motor and the operating conditions of the inverter. Rapidly and accurately calibrating the optimal efficiency point of the variable frequency motor system is of great significance for improving the quality of motor products and reducing equipment energy consumption.

[0003] The detection method in the existing optimal efficiency point detection technology searches for the optimal efficiency point by traversing all "speed-torque" test points. This method requires fine adjustment of the test step parameters and efficiency evaluation mechanism, resulting in a complicated pre-debugging process in the early stage of the test, a long formal detection cycle and low efficiency. At the same time, it does not fully consider the differences between different batches or different models of variable frequency motors in actual detection, making it difficult to meet consistency requirements. In addition, once the test results of a certain test point deviate, it may affect the accuracy of the overall test results. Summary of the invention

[0004] In order to solve the above technical problems, the present invention proposes a method and device for quickly detecting the optimum efficiency point of a variable frequency motor system to solve the above problems existing in the prior art.

[0005] To achieve the above object, the present invention provides a method for quickly detecting the optimal efficiency point of a variable frequency motor system, comprising:

[0006] S1. Initialize the variable frequency motor system; the process includes: calibrating the speed sensor and the torque sensor, and setting the test parameters of the variable frequency motor system;

[0007] S2, selecting an initial test point, and obtaining a rough search range based on the initial test point;

[0008] S3, performing efficiency tests on each test point within the rough search range, obtaining the optimal efficiency of the current search range and determining whether to update the global optimal efficiency;

[0009] S4, obtaining a high-efficiency region based on the updated global optimal efficiency; after subdividing the high-efficiency region into grids, testing each refined grid test point to determine whether the change in the efficiency value meets the preset requirements, and if so, executing S5;

[0010] S5. Output the global optimal efficiency and the corresponding torque value and speed value.

[0011] Optionally, the test parameters in S1 include a global speed range, a global torque range, the number of speed test points, the number of torque test points, and the test time of the test points.

[0012] Optionally, in S1, the speed search step is determined based on the global speed range and the number of speed test points, and the torque search step is determined based on the global torque range and the number of torque test points; based on the search step, a uniform grid division method is used to obtain speed test points and torque test points.

[0013] Optionally, in S2, the initial test point is taken as the center, and each test point of one adjacent search step is taken as a rough search range;

[0014] The efficiency value set of the rough search range is as follows:

[0015] ;

[0016] Where η c is the efficiency value, is the pth speed test point, is the qth torque test point, , k is the number of speed test points, and m is the number of torque test points; wherein, at the beginning of the test, if the initial test points satisfy i-1<0 or j-1<0, these test points are removed from the set S.

[0017] Optionally, the process of performing efficiency testing on each test point within the rough search range in S3 includes:

[0018] Test points are set in the global speed range and the global torque range; when each test point is stably maintained, the motor operation data and the inverter internal operation parameter data are collected to construct a data group; the variable frequency motor system efficiency value is calculated based on the data group; the variable frequency motor system efficiency value is subjected to a first-order low-pass filtering process; and a stable efficiency value is obtained.

[0019] Optionally, a first-order low-pass filter is performed as follows:

[0020]

[0021] In the formula, The original efficiency data collected is is the efficiency data after filtering, x is the current sampling time, α is the filter coefficient, and the value range is 0<α<1; the filter coefficient is set according to the sampling frequency and dynamic response requirements.

[0022] The present invention also provides a device for realizing the above-mentioned method for quickly detecting the optimal efficiency point of the variable frequency motor system, comprising:

[0023] The variable frequency power supply system includes three-phase AC power supply and single-phase AC power supply, which are used to power the tested motor system, load motor system and main control system;

[0024] The main control system includes a data acquisition module, an efficiency calculation module, a communication module and a human-machine interface; the acquisition module is used to obtain the speed, torque and power data of the variable frequency motor system through the speed torque detection module and the current detection module; the efficiency calculation module is used to calculate the power and efficiency of each part; the communication module interacts with the outside to realize the operation and monitoring of the human-machine interface;

[0025] The motor system under test includes a frequency converter under test and a motor under test. The frequency converter under test receives control signals from the main control system, converts three-phase AC power into adapted AC power, and drives the motor under test to operate.

[0026] The load motor system includes a load inverter and a load motor, which are used to provide a load for the motor under test and detect the real-time speed of the variable frequency motor system;

[0027] The test bench system includes a motor fixture bench, which is used to fix the test motor, load motor and torque sensor.

[0028] Optionally, the three-phase AC power supply is electrically connected to the tested motor system and the load motor system via a three-phase cable, and the single-phase AC power supply is connected to the main control system.

[0029] Optionally, the motor under test, the torque sensor and the load motor are mechanically connected via a coupling to transmit the speed and torque sensor to detect the real-time torque of the motor system and transmit it to the main control system.

[0030] Compared with the prior art, the present invention has the following advantages and technical effects:

[0031] The present invention provides a method and device for quickly detecting the optimal efficiency point of a variable frequency motor system. In the method, first, the variable frequency motor system is initialized; then, an initial test point is selected, and a rough search range is obtained based on the initial test point; then, an efficiency test is performed on each test point within the rough search range to obtain the optimal efficiency of the current range and determine whether to update the global optimal efficiency; if updated, a high efficiency area is obtained based on the updated global optimal efficiency; finally, the high efficiency area is subdivided into grids, and each refined grid test point is tested; if the change in the efficiency value meets the preset requirements, the global optimal efficiency and the corresponding torque value and speed value are output.

[0032] The present invention adopts modular design and precise testing algorithm, which significantly shortens the efficiency detection time and quickly locates the optimal efficiency point of the variable frequency motor system. Users can flexibly define the range and step size of the efficiency test according to the actual working conditions, support optimization testing under different speed and accuracy requirements, intuitively evaluate the system operation performance, and improve the applicability and flexibility of the system. The iterative optimization process has good anti-interference ability and is insensitive to the measurement error of a single efficiency value. Different search processes can guarantee convergence to the correct optimal efficiency point, greatly improving the speed and accuracy of efficiency detection. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] The drawings constituting a part of the present application are used to provide a further understanding of the present application. The illustrative embodiments and descriptions of the present application are used to explain the present application and do not constitute an improper limitation on the present application. In the drawings:

[0034] Figure 1 A flowchart of the rapid detection of the optimal efficiency of the variable frequency motor system according to an embodiment of the present invention;

[0035] Figure 2 A schematic diagram of an automatic optimization process of an efficiency cloud graph according to an embodiment of the present invention;

[0036] Figure 3 4 is a hardware architecture diagram of a variable frequency motor efficiency detection system according to an embodiment of the present invention. DETAILED DESCRIPTION

[0037] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0038] It should be noted that the steps shown in the flowcharts of the accompanying drawings can be executed in a computer system such as a set of computer executable instructions, and that, although a logical order is shown in the flowcharts, in some cases, the steps shown or described can be executed in an order different from that shown here.

[0039] Embodiment 1

[0040] like Figure 1 As shown, this embodiment provides a method and device for quickly detecting the optimal efficiency point of a variable frequency motor system, including:

[0041] S1. Initialize the variable frequency motor system; the process includes: calibrating the speed sensor and the torque sensor, and setting the test parameters of the variable frequency motor system;

[0042] Furthermore, the test parameters in S1 include a global speed range, a global torque range, a number of speed test points, a number of torque test points, and a test time of a test point.

[0043] Furthermore, in S1, the search step length of the speed is determined based on the global speed range and the number of speed test points, and the search step length of the torque is determined based on the global torque range and the number of torque test points; based on the search step length, the speed test points and the torque test points are obtained by using a uniform grid division method.

[0044] Specifically, the variable frequency motor system is set to the initialization state, the speed sensor and torque sensor are calibrated first, and then the test parameters are set on the host computer of the control system, including setting the global speed range, global torque range, speed test points, torque test points, test point test time and other parameters, such as Figure 2 shown.

[0045] Global speed range [n min ,n max ]: Determine the global speed range based on the rated operating parameters of the motor to ensure that the range covers the possible best efficiency point, where n min Usually set to the lowest speed allowed by the motor. max Set it to the rated speed of the motor or close to its maximum allowable value;

[0046] Global torque range [T min ,T max ]: Define the global torque range according to application requirements and motor rated torque, T min Set as the torque of the motor when it is unloaded, T max Set to the motor rated torque or maximum allowable torque;

[0047] Speed ​​test points m: Use uniform grid division method to divide the range into k speed points on average. The speed division formula is:

[0048] (1)

[0049] Where ∆n is defined as the search step size of the speed:

[0050] (2)

[0051] Torque test point number k: Use uniform grid division method to divide the range into m torque points on average. The torque division formula is:

[0052] (3)

[0053] Where ∆T is defined as the torque search step size:

[0054] (4)

[0055] Test point test duration t: Determine the duration of each speed / torque test point operation, which needs to be greater than the response time of the motor system to ensure that the motor system is in a stable operation process when data is collected after speed / torque adjustment; preferably, the test duration is set to 5s;

[0056] The initial starting point of the iterative optimization process (n i ,T j ): Select the test starting point of the iterative process and decide where to start the search; preferably, the test starting point usually selects the minimum speed, and there is no limit on the torque, which is expressed as (n min ,T j );

[0057] The optimal efficiency value η in the global scope opt : Set the initial optimal efficiency value of the iterative optimization process to 0.

[0058] S2, selecting an initial test point, and obtaining a rough search range based on the initial test point;

[0059] Furthermore, in S2, each test point adjacent to one search step is defined as a rough search range with the initial test point as the center;

[0060] Specifically, in the test, the speed and torque of a test point are defined as (n i ,T j ), and its efficiency test value is η c (n i ,T j ), then the test point is taken as the center and each test point adjacent to it with a search step length is defined as a rough search range, such as Figure 2 As shown in the “rough search range”, the efficiency values ​​of each test point within this range can be expressed as a set S:

[0061] (5)

[0062] where η c is the efficiency value; at the beginning of the test, if the selected initial test points satisfy i -1< 0 or j -1< 0, these test points are removed from the set S; in particular, if the selected initial test point is (n0, T0), the set S can be degenerated into:

[0063] (6)

[0064] The optimal efficiency value in the current efficiency set S is defined as:

[0065] (7)

[0066] After the rough search range is defined, proceed to step S3.

[0067] S3, performing efficiency tests on each test point within the rough search range, obtaining the optimal efficiency of the current search range and determining whether to update the global optimal efficiency, if updated, executing S4; S3 includes 4 sequentially connected sub-processes;

[0068] S31: Set test points;

[0069] Within the set global range, if the motor initial speed n0 and initial torque T0 are given when the initial test point is first determined, and if the motor speed n is given during the test point iteration process p and torque T q The host computer of the main control system sends a control data packet to the tested inverter through the communication module to control the tested motor to reach the specified speed. The host computer sends a control data packet to the load inverter through the communication module to set the load motor to reach the specified load torque. Each test point maintains the test time t to ensure that the motor system has enough time to enter a stable operating state.

[0070] S32: Collecting operation data;

[0071] When the motor system runs stably at the set speed and torque, each sensor in the main control system acquisition module reads the operating data, including the motor speed n, the motor torque T, and the internal operating parameters of the inverter such as the output frequency f, the motor voltage U, the motor current I, the power factor cosφ, etc., to form a data group; to ensure that a sufficient number of data groups can be collected within the test time t, the preferred data sampling frequency is 5ms / group;

[0072] S33: Calculate system efficiency;

[0073] Based on the read motor operation data and inverter operation data, calculate the variable frequency motor system efficiency, which is usually defined as the motor output power P out With input power P in The ratio of

[0074] (8)

[0075] Among them, the motor output power P out It can be calculated by the motor torque T and speed n:

[0076] (9)

[0077] Motor input power P in It can be calculated from the motor input voltage U, current I and power factor cosφ:

[0078] (10)

[0079] During the test time t, the efficiency of the continuously collected data groups is calculated by using equations (8)-(10), and the multiple groups of efficiency values ​​are processed by first-order low-pass filtering to make the efficiency values ​​more stable:

[0080] (11)

[0081] In the formula, The original efficiency data collected is is the efficiency data after filtering, x is the current sampling time, α is the filter coefficient, and the value range is 0<α<1. The filter coefficient is set according to the sampling frequency and dynamic response requirements, usually α=0.1∼0.2.

[0082] S34: Efficiency optimization and updating search scope;

[0083] According to steps S31-S33, the efficiency of each test point within the rough search range is tested to obtain the efficiency value set S as expressed in formula (5), and the optimal efficiency η within the current rough search range is obtained according to formula (7): c_max ; If the optimal efficiency value of the current search range is greater than the optimal efficiency value of the previous search range, then update the current optimal efficiency to the global optimal efficiency, that is, if it satisfies:

[0084] (12)

[0085] but,

[0086] (13)

[0087] In the above formula, δ is the overall detection number of the rough search range;

[0088] With the current optimal efficiency η opt The corresponding test point is taken as the center, and the next rough search range is set. The efficiency search process of steps S31-S33 is repeated and iterated continuously, so that the new rough search range gradually approaches the global optimal efficiency point. The initialization of the new rough search range is:

[0089] (14)

[0090] Where i new 、j new Center test point for the updated rough search range;

[0091] If the optimal efficiency value of the current search range is less than the optimal efficiency value of the previous search range, the iteration of step S3 is stopped and the high-efficiency area refinement search phase of step S4 is entered.

[0092] S4, obtaining a high-efficiency region based on the updated global optimal efficiency; after subdividing the high-efficiency region into grids, testing each refined grid test point to determine whether the change in the efficiency value meets the preset requirements, and if so, executing S5;

[0093] Specifically, assuming n ref ,T ref is the current optimal efficiency η opt The corresponding speed and torque values ​​are defined as (n ref ,T ref ) is the center of the high efficiency region, and the step size is reduced and the grid is subdivided in the high efficiency region:

[0094] (15)

[0095] (16)

[0096] Generate refined mesh points:

[0097] (17)

[0098] (18)

[0099] Wherein, ∆n and ∆T are the aforementioned rough search steps, ∆n′ and ∆T′ are the refined search steps, and d is the refinement density, which can be set according to the requirements for search accuracy; preferably, considering minimizing the number of searches, d=2; if higher accuracy is required, the value of d can be increased;

[0100] The efficiency search process of steps S31-S33 is used to test all refined grid points and search for the optimal efficiency of the test points. x The changes satisfy:

[0101] (19)

[0102] Where η x is the efficiency value of the refined search area, γ is the number of detections in the refined search range, and ε is the preset minimum efficiency change; this condition is used to determine whether the change in the efficiency value tends to be stable. When the change is less than ε, it can be considered that the current efficiency value search accuracy has met the requirements, and enter step S5.

[0103] S5. Output the global optimal efficiency and the corresponding torque value and speed value.

[0104] Specifically, after accurately locating the optimal efficiency point, the search process ends and the optimal efficiency η of the point is recorded in detail. opt , and the corresponding torque value T opt and speed value n opt, and output the efficiency, speed and torque values ​​of the optimal efficiency point finally determined to the host computer for display.

[0105] like Figure 3 As shown, this embodiment also provides a device for implementing the above-mentioned method for quickly detecting the optimal efficiency point of the variable frequency motor system, including:

[0106] The variable frequency power supply system mainly includes a three-phase AC power supply and a single-phase AC power supply; the three-phase AC power supply is electrically connected to the tested motor system and the load motor system through a three-phase cable, and the single-phase AC power supply is connected to the main control system through an independent line to supply power to the main control system;

[0107] The motor system under test is composed of a frequency converter under test and a motor under test; the input end of the frequency converter under test is electrically connected to the aforementioned three-phase AC power supply, and the output end is electrically connected to the input end of the motor under test. The frequency converter under test receives the control signal of the main control system, converts the three-phase AC power into the adapted AC power, drives the motor under test to operate, and realizes effective control and testing of the motor under test;

[0108] The load motor system includes a load inverter and a load motor; the input end of the load inverter is electrically connected to the aforementioned three-phase AC power supply, and the output end is electrically connected to the input end of the load motor. The load inverter can apply different load torques to the tested motor, and the internal speed sensor detects the real-time speed of the motor system.

[0109] The test bench system includes a motor tooling bench, a torque sensor installed between the test motor and the load motor, and its fixing bracket; the test motor, the torque sensor and the load motor are mechanically connected through a coupling to transmit the speed and torque. At the same time, the torque sensor detects the real-time torque of the motor system and transmits it to the main control system;

[0110] The main control system, which consists of data acquisition, efficiency calculation, communication module and human-machine interface, is mainly used for data acquisition, processing and control of the entire variable frequency motor system; the acquisition module collects system speed, torque and power data, the calculation module calculates the power and efficiency of each part, and the communication module interacts with the outside to realize the operation and monitoring of the human-machine interface; each module is connected by electrical signals.

[0111] The present invention can adaptively adjust the torque and speed range, step size and test point duration, and allow users to specify target variables (such as efficiency) according to their needs, customize the search range and convergence conditions. By reducing the probability of testing in non-efficient working conditions and significantly improving the testing accuracy in efficient working conditions, the detection efficiency and accuracy are effectively optimized.

[0112] The above are only preferred specific implementations of the present application, but the protection scope of the present application is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed in the present application should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims

1. A method for quickly detecting the optimal efficiency point of a variable frequency motor system, characterized in that: The following steps are involved: S1. Initialize the variable frequency motor system; the process includes: calibrating the speed sensor and the torque sensor, and setting the test parameters of the variable frequency motor system; S2, selecting an initial test point, and obtaining a rough search range based on the initial test point; In S2, the initial test point is taken as the center, and each test point of one adjacent search step is taken as a rough search range; The efficiency value set of the rough search range is as follows: ； Where η c is the efficiency value, is the pth speed test point, is the qth torque test point, , , k is the number of speed test points, and m is the number of torque test points; wherein, at the beginning of the test, if the initial test points satisfy i-1<0 or j-1<0, these test points are removed from the set S; S3, perform efficiency test on each test point within the rough search range, obtain the optimal efficiency of the current search range and determine whether to update the global optimal efficiency, and define the optimal efficiency value in the current efficiency set S as: , if the optimal efficiency value of the current search range is greater than the optimal efficiency value of the previous search range, then update the current optimal efficiency to the global optimal efficiency, take the test point corresponding to the current optimal efficiency as the center, set the next rough search range, repeat the efficiency search process of step S3 and iterate continuously, so that the new rough search range gradually approaches the global optimal efficiency point; the initialization of the new rough search range is: , where i new 、j new is the center test point of the updated rough search range; if the optimal efficiency value of the current search range is less than the optimal efficiency value of the previous search range, the iteration of step S3 is stopped and the high-efficiency area refinement search phase of step S4 is entered; S4, obtaining a high-efficiency region based on the updated global optimal efficiency; after subdividing the high-efficiency region into grids, testing each refined grid test point to determine whether the change in the efficiency value meets the preset requirements, and if so, executing S5; S5. Output the global optimal efficiency and the corresponding torque value and speed value.

2. The method for rapidly detecting the optimum efficiency point of a variable frequency motor system according to claim 1, characterized in that: The test parameters in S1 include a global speed range, a global torque range, the number of speed test points, the number of torque test points, and the test time of the test points.

3. The method for rapidly detecting the optimum efficiency point of a variable frequency motor system according to claim 2, characterized in that: In S1, the search step length of the speed is determined based on the global speed range and the number of speed test points, and the search step length of the torque is determined based on the global torque range and the number of torque test points; based on the search step length, the speed test points and the torque test points are obtained by using a uniform grid division method.

4. The method for rapidly detecting the optimum efficiency point of a variable frequency motor system according to claim 1, characterized in that: The process of performing efficiency testing on each test point within the rough search range in S3 includes: Test points are set in the global speed range and the global torque range; when each test point is stably maintained, the motor operation data and the inverter internal operation parameter data are collected to construct a data group; the variable frequency motor system efficiency value is calculated based on the data group; the variable frequency motor system efficiency value is subjected to a first-order low-pass filtering process; and a stable efficiency value is obtained.

5. The method for rapidly detecting the optimum efficiency point of a variable frequency motor system according to claim 4, characterized in that: The first-order low-pass filtering process is as follows: ； In the formula, The original efficiency data collected is is the efficiency data after filtering, x is the current sampling time, α is the filter coefficient, and the value range is 0<α<1; the filter coefficient is set according to the sampling frequency and dynamic response requirements.

6. A device for implementing the method for quickly detecting the optimal efficiency point of a variable frequency motor system according to any one of claims 1 to 5, characterized in that: The variable frequency power supply system includes three-phase AC power supply and single-phase AC power supply, which are used to power the tested motor system, load motor system and main control system; The main control system includes a data acquisition module, an efficiency calculation module, a communication module and a human-machine interface; the acquisition module is used to obtain the speed, torque and power data of the variable frequency motor system through the speed torque detection module and the current detection module; the efficiency calculation module is used to calculate the power and efficiency of each part; the communication module interacts with the outside to realize the operation and monitoring of the human-machine interface; The motor system under test includes a frequency converter under test and a motor under test. The frequency converter under test receives control signals from the main control system, converts three-phase AC power into adapted AC power, and drives the motor under test to operate. The load motor system includes a load inverter and a load motor, which are used to provide a load for the motor under test and detect the real-time speed of the variable frequency motor system; The test bench system includes a motor fixture bench, which is used to fix the test motor, load motor and torque sensor.

7. The device according to claim 6, characterized in that The three-phase AC power supply is electrically connected to the tested motor system and the load motor system through a three-phase cable, and the single-phase AC power supply is connected to the main control system.

8. The device according to claim 6, characterized in that The tested motor, torque sensor and load motor are mechanically connected through a coupling to transmit the speed and torque sensor to detect the real-time torque of the motor system and transmit it to the main control system.

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