A measuring device and method for comprehensive electrical parameters of a permanent magnet synchronous motor

Abstract

The application belongs to the technical field of electric power detection, and provides a kind of permanent magnet synchronous motor comprehensive electric parameter measuring device and measuring method.The measuring device includes microcontroller module, and the power module, motor control module, voltage and current signal AD conversion module, zero-crossing detection module, storage module, data transmission module and touch display module all connected with microcontroller module;The microcontroller module is used to collect the voltage signal after power-off of motor according to the digital voltage signal, current signal input by voltage and current signal AD conversion module and zero-crossing signal input by zero-crossing detection module, and equivalent conversion is the counter electromotive force of the motor to be measured, or the voltage signal and current signal of motor are collected according to the expected acquisition frequency, and the voltage signal and current signal are fast fourier decomposed, the amplitude and phase of fundamental wave and each harmonic are obtained, and the active power, reactive power and power factor of the motor to be measured are calculated in real time.

Description

Technical Field

[0001] This invention belongs to the field of power detection technology, specifically relating to a measuring device and method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor. Background Technology

[0002] The statements in this section are merely background information related to the present invention and do not necessarily constitute prior art.

[0003] Permanent magnet synchronous motors (PMSMs) are widely used in engineering machinery, home appliances, transportation, and military defense due to their high power density, torque density, high power factor, excellent speed regulation performance, and high efficiency over a wide speed range. However, in practical applications, it has been found that the superior performance of PMSMs, especially their high power factor, is often difficult to fully realize. In many industrial applications where speed regulation requirements are not high, PMSMs are often selected based on the maximum load. Therefore, the motor's load rate during daily operation is not high. For example, with PMSMs used in oilfield pumping units, the average load during normal operation is only about 30% of the maximum load. This mismatch between the motor and the pumping unit load causes the motor to operate at low efficiency.

[0004] According to the operating theory of permanent magnet motors, the motor's operating power factor is closely related to the load rate and the magnitude of the critical back electromotive force (no-load back EMF). When the load rate is high, the power factor of the permanent magnet motor is often at a high level; when the load rate is low, and the stator voltage of the applied permanent magnet synchronous motor is equal to or approximately equal to the critical back EMF, the motor's reactive power is at its minimum and the power factor is at its maximum. However, as the applied voltage gradually exceeds the critical back EMF of the permanent magnet motor, the proportion of reactive power gradually increases, the power factor decreases accordingly, and the motor's energy consumption increases significantly.

[0005] As can be seen from the above description, the voltage, current, no-load back EMF, active power, reactive power, power factor and other parameters of permanent magnet motors are of great guiding significance for judging the current working state and energy consumption level of permanent magnet motors. Therefore, the invention of a measurement method and testing equipment that can conveniently and comprehensively measure the above parameters has significant engineering practical significance.

[0006] Among the electrical parameters of permanent magnet motors mentioned above, voltage and current are easy to measure, while measuring the motor's no-load back EMF and power factor is more difficult. For measuring the back EMF of a permanent magnet synchronous motor, the traditional method mainly involves using a permanent magnet synchronous motor of the same pole or a synchronous motor to drive the motor under test at its rated speed, and then detecting the open-circuit voltage of the motor windings. This voltage is the rated no-load back EMF. This measurement method is offline and requires a dedicated testing platform, which inevitably interrupts equipment production, consumes a lot of manpower and resources, and is extremely inconvenient to operate. It also makes it difficult to frequently monitor the back EMF of the permanent magnet synchronous motor. Furthermore, many permanent magnet synchronous motors are installed outdoors or in enclosed environments. With changes in the ambient temperature and load rate throughout the year, the operating temperature of the permanent magnets fluctuates within a wide range. Due to the sensitivity of magnetic properties to temperature, the no-load back EMF will also change within a certain range. Therefore, data obtained using offline measurement methods has a certain lag effect on on-site adjustment of the motor's power factor. For power factor measurement, current engineers primarily use power analyzers such as the FLUK43B or HIOKI3169. However, these power testing devices are expensive and difficult to modify. In reality, most permanent magnet synchronous motors (PMSMs) operate in a relatively simple mode with slow load changes. It can be assumed that the three-phase load of the motor is symmetrical at any given time. Therefore, it is not necessary to simultaneously collect the three-phase voltage and current of the motor for power factor calculation. Theoretically, only the voltage and current signals of one phase are needed for power factor measurement. Reducing the number of high-precision current sensors can significantly lower equipment costs. Summary of the Invention

[0007] To address the aforementioned problems, this invention proposes a measurement device and method for comprehensive electrical parameters of permanent magnet synchronous motors. This invention is applicable to the comprehensive parameter detection of various permanent magnet synchronous motors under different operating conditions, and can quickly and efficiently obtain the voltage, current, no-load back EMF, active power, reactive power, and power factor of the motor under test, providing technical support for the daily operation, maintenance, and energy efficiency improvement of permanent magnet synchronous motors in different working environments.

[0008] According to some embodiments, the present invention adopts the following technical solution:

[0009] In a first aspect, the present invention provides a device for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor.

[0010] A device for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor includes: a microcontroller module, and a power supply module, a motor control module, a voltage and current signal AD conversion module, a zero-crossing detection module, a storage module, a data transmission module, and a touch display module, all connected to the microcontroller module.

[0011] The microcontroller module is used to send on / off signals to the motor under test through the motor control module based on the digital voltage signal and current signal input from the voltage and current signal AD conversion module and the zero-crossing signal input from the zero-crossing detection module. It collects the voltage signal of the permanent magnet motor after power failure at the desired sampling frequency and converts it into the back electromotive force of the motor under test. Alternatively, it collects the voltage and current signals of the permanent magnet synchronous motor at the desired sampling frequency and performs fast Fourier decomposition on the voltage and current signals to obtain the amplitude and phase of the fundamental wave and each harmonic. Based on this, it calculates the active power, reactive power and power factor of the permanent magnet synchronous motor under test in real time. According to the commands issued by the touch display module, it analyzes the measured data and sends the relevant data to the touch display module, or saves the data to the storage module, or uploads the test data through the data transmission module.

[0012] Furthermore, the motor control module is used to control the start and stop of the permanent magnet synchronous motor under test.

[0013] Furthermore, the voltage and current signal AD conversion module is also connected to a voltage and current acquisition interface, which is connected to the permanent magnet synchronous motor under test through a voltage sensor and a current sensor.

[0014] The voltage sensor and current sensor are used to input the voltage and current signals of the permanent magnet synchronous motor under test to the voltage and current signal acquisition interface.

[0015] Furthermore, if the voltage sensor is connected to the permanent magnet synchronous motor under test using alligator clip-connected wires, then an input step-down module is connected between the voltage and current signal AD conversion module and the voltage and current acquisition interface.

[0016] Furthermore, the voltage sensor uses a high-voltage probe connected to the permanent magnet synchronous motor under test, so the voltage and current signal AD conversion module is directly connected to the voltage and current acquisition interface.

[0017] Secondly, the present invention provides a method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor.

[0018] A method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor, employing the measuring device for the comprehensive electrical parameters of a permanent magnet synchronous motor as described in the first aspect, comprising:

[0019] The permanent magnet synchronous motor under test is powered by an external power supply.

[0020] The periodic effective value of the line voltage of the three-phase winding of the permanent magnet synchronous motor is measured in real time, and the no-load line back electromotive force of the permanent magnet synchronous motor is measured online by instantaneously switching the power supply circuit of the motor under test.

[0021] The periodic effective value of the line voltage of the three-phase winding of the permanent magnet synchronous motor is measured. When the line voltage of the three-phase winding of the permanent magnet synchronous motor is symmetrical, the line voltage of the three-phase winding of the permanent magnet synchronous motor and the phase current of one phase are continuously measured to calculate the active power, reactive power, apparent power and power factor.

[0022] Calculate the average active power and average power factor over a continuous measurement period;

[0023] Record the test data related to the no-load back electromotive force and power factor of the permanent magnet synchronous motor under test.

[0024] Furthermore, the line voltage symmetry of the three-phase windings of the permanent magnet synchronous motor is determined based on the difference between the line voltages of each two phases being within 3%.

[0025] Furthermore, the process of online measurement of the no-load line back electromotive force of the permanent magnet synchronous motor includes:

[0026] Real-time acquisition of line voltage of three-phase stator windings of motor U and voltage frequency f ;

[0027] Set voltage capture frequency f 1. Rated operating frequency of permanent magnet synchronous motor f 2;

[0028] Instantly disconnect the armature winding of the permanent magnet synchronous motor under test to open the circuit;

[0029] When the armature is de-energized, the rotor speed increases or decreases, and the corresponding frequency of the no-load back electromotive force increases or decreases. When the frequency... f = f At time 1, the discrete waveform of the back electromotive force at frequency f1 is stored. {E 1 …E n } ;

[0030] Calculate the average value of the discrete waveform of the back electromotive force. The waveform is then equivalent to a sine wave with a frequency of f1 and a period average of E1.

[0031] The frequency of a sine wave with frequency f1 and average period E1 is reduced according to... The average periodic value E2 of the sine wave at frequency f2 is obtained.

[0032] according to The average value E2 of the sinusoidal waveform is converted into the effective value E0 of the sinusoidal waveform, which is the effective value of the no-load back electromotive force of the permanent magnet synchronous motor to be measured.

[0033] The permanent magnet synchronous motor was reconnected to the power supply circuit, and the motor returned to normal operation.

[0034] Furthermore, the process of continuously measuring the line voltage of the three-phase windings of the permanent magnet synchronous motor and the phase current of one phase includes:

[0035] The total acquisition time for calculating the power factor based on the working cycle of the motor under test. T Total number of collections N And calculate the time interval between single data collections. The current number of collections P Initialize to 0;

[0036] Select the phase of the current to be measured, which can be any one of phases A, B, and C;

[0037] Start measuring and compare the current number of data collections. P Total number of collections N The size, if P≤N The voltage and current of the motor are sampled and their spectra decomposed, and power-related parameters are calculated. The current sampling count is also recorded. P Increment by 1, iterate and loop until... P>N Collection complete.

[0038] Furthermore, the sampling and spectral decomposition of the motor's voltage and current, and the calculation of primary power-related parameters specifically include:

[0039] Frequency of input voltage measurement f in And set the number of harmonic analyses. N fft ,according to f in and N fft Calculate the voltage and current sampling frequency required for the current power acquisition. f 采 ;

[0040] Depending on the selected current phase, at the sampling rate f 采 The voltage and current are collected, and voltage data from several points and current data from several points are collected to form voltage arrays and current arrays for the current power acquisition time P.

[0041] The voltage and current signals of the current power acquisition P are decomposed using the Fast Fourier Transform (FFT) algorithm to obtain the fundamental frequency and each harmonic. {U P,1 , …, U P,N } , {I P,1 , …, IP,N } ;

[0042] Based on the fundamental and harmonic frequencies obtained from the decomposition, calculate the effective values ​​of the voltage and current at the current power acquisition level P. (Effective voltage value) RMS current value ;

[0043] Calculate the current power sampling time using the following formulas. P Apparent power S P Active power P P reactive power Q P and power factor λ P :

[0044]

[0045]

[0046]

[0047]

[0048] in, k F The harmonic active power compensation coefficient is taken as . , Indicates the current power sampling time. P The fundamental voltage RMS value, Indicates the current power sampling time P The effective value of the fundamental current, Indicates the current power sampling time P The fundamental voltage phase, Indicates the current power sampling time P The phase of the fundamental current.

[0049] Furthermore, the process of calculating the effective values ​​of voltage and current within a continuous measurement cycle, and calculating active power, reactive power, apparent power, and power factor includes:

[0050] Collect active power sequence within a continuous measurement period {P 1 ,…,P N } Power factor sequence {λ 1 ,…,λ N } ;

[0051] Calculate the average of the absolute values ​​of the active power series and the power factor series, i.e. , ;

[0052] Based on the results of the last active power calculation P N The positive and negative values ​​are obtained k This is used to calculate the average active power and the average power factor, i.e. , ,in .

[0053] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0054] 1. In addition to measuring the line voltage of the three-phase windings of a permanent magnet motor, this invention can also perform high-precision online measurement of the no-load back electromotive force of a permanent magnet synchronous motor in real time. The measured back electromotive force value can then be used as a reference standard for the input voltage of the permanent magnet synchronous motor under different load rates, or as a technical indicator of whether the permanent magnets of the permanent magnet motor have demagnetized.

[0055] 2. This invention enables dynamic power factor detection with low testing costs. Targeting the operating characteristics of permanent magnet motors in most industrial application scenarios, this invention pre-verifies the symmetry of the motor's three-phase load and uses only one phase current and voltage signal to complete the detection of three-phase power and power factor. This reduces the number of current sensors, which account for a large proportion of the cost in traditional measurement equipment, thereby significantly reducing the testing cost of power factor.

[0056] 3. This invention can flexibly set parameters such as total acquisition time, total acquisition times, and harmonic analysis times according to the working cycle of permanent magnet motors in different industrial application scenarios. It can design different test methods according to the actual working conditions of the motor as much as possible, making each test process more targeted and the test results more scientific.

[0057] 4. This invention can simultaneously provide the back electromotive force and instantaneous / periodic power factor of the motor under test to relevant engineering technicians during a single measurement process. This allows relevant personnel to immediately adjust the power supply voltage of the motor on-site based on the real-time measured back electromotive force value to improve its operating power factor and improve the energy consumption performance of the motor under test on-site.

[0058] 5. This invention can be further developed to meet the diverse testing needs of the permanent magnet motor under test in different scenarios, so as to satisfy more diverse testing requirements. Attached Figure Description

[0059] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0060] Figure 1 This is a schematic diagram of a module for an embodiment of comprehensive electrical parameter measurement of a permanent magnet synchronous motor;

[0061] Figure 2 This is a schematic diagram of the motor connection for online measurement of the no-load back electromotive force of a permanent magnet synchronous motor;

[0062] Figure 3 This is a schematic diagram of the motor connection for measuring the power factor of a permanent magnet synchronous motor;

[0063] Figure 4(a) is a schematic diagram of the comprehensive electrical parameter measurement device for permanent magnet synchronous motor;

[0064] Figure 4(b) is a front view of the comprehensive electrical parameter measuring device for permanent magnet synchronous motors;

[0065] Figure 4(c) is a rear view of the first embodiment of the comprehensive electrical parameter measuring device for permanent magnet synchronous motor;

[0066] Figure 4(d) is a rear view of the second embodiment of the comprehensive electrical parameter measuring device for permanent magnet synchronous motors;

[0067] Figure 5 This is a flowchart of the online measurement process for the no-load back electromotive force of a permanent magnet synchronous motor.

[0068] The components include: 1. Power supply module; 2. Motor control module; 3. Voltage and current acquisition interface; 4. Input step-down module; 5. Voltage and current signal AD conversion module; 6. Zero-crossing detection module; 7. Storage module; 8. Data transmission module; 9. Touch display module; 10. Microcontroller module; and 11. Housing. Detailed implementation method:

[0069] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0070] It should be noted that the following detailed description is illustrative and intended to provide further explanation of the invention. Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0071] It should be noted that the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the scope of exemplary embodiments according to the invention. As used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise. Furthermore, it should be understood that when the terms "comprising" and / or "including" are used in this specification, they indicate the presence of features, steps, operations, devices, components, and / or combinations thereof.

[0072] In this invention, terms such as "connected" and "linked" should be interpreted broadly, indicating a fixed connection, an integral connection, or a detachable connection; a direct connection or an indirect connection through an intermediate medium. Those skilled in the art can determine the specific meaning of these terms in this invention based on the specific circumstances, and they should not be construed as limitations on the invention.

[0073] Example 1

[0074] This embodiment provides a device for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor. This embodiment consists of the following modules, as shown in the schematic diagram below. Figure 1 As shown, it includes:

[0075] Power module 1 is used to power the internal modules of the device, converting the externally input 12V voltage into -12V, 5V and 3.3V for use by other modules of the device;

[0076] Motor control module 2 is used for start-stop control of the permanent magnet synchronous motor under test;

[0077] Voltage and current acquisition interface 3 is used to acquire the line voltage of the motor under test and the three-phase windings and the line current of one phase winding;

[0078] Input step-down module 4 is used to step down the high voltage of the input device for signal input;

[0079] The voltage-current signal AD conversion module 5 is used to convert the stepped-down analog voltage signal into a digital voltage signal for analysis and calculation by the microcontroller unit.

[0080] The voltage zero-crossing detection module 6 is used to determine the zero-crossing point of the input voltage waveform, thereby obtaining the frequency of the input signal in real time.

[0081] Storage module 7: Used for storing intermediate calculation results, final results, and historical data involved in this device;

[0082] Data transmission module 8: Used to transmit test data to the outside world via wired or wireless means;

[0083] Touch display module 9: Used for information and data interaction between the device and the user, accepting user commands and completing related operations, while displaying data and charts in the measurement process and historical data;

[0084] The microcontroller module 10 is electrically connected to the power supply module 1, motor control module 2, voltage / current signal AD conversion module 5, zero-crossing detection module 6, storage module 7, data transmission module 8, and touch display module 9, respectively. It is used to send on / off signals to the motor under test via the motor control module 2 based on the digital voltage and current signals input from the voltage / current signal AD conversion module 5 and the zero-crossing signal input from the zero-crossing detection module 6. It collects the voltage signal of the permanent magnet motor after power-off at the desired sampling frequency, converting it into the back electromotive force of the motor under test. Alternatively, it collects the voltage and current of the motor at the desired sampling frequency and performs Fast Fourier Decomposition on the voltage and current signals using the FFT algorithm to obtain the amplitude and phase of the fundamental wave and each harmonic in real time. It also calculates the active power, reactive power, and power factor of the motor under test in real time. Based on commands issued by the user on the touch display module 9, it analyzes the measured data and sends the relevant data to the touch display module 9, or saves the data to the storage module 7, or uploads the test data via the data transmission module 8.

[0085] In addition to the modules mentioned above, this embodiment also includes a voltage sensor and a current sensor connected to the motor under test, and inputs the voltage and current signals of the permanent magnet synchronous motor under test to the voltage and current signal acquisition interface.

[0086] As one or more embodiments, the voltage sensor can be a wire connected by an alligator clip, which directly inputs a high-voltage signal into the measuring device, and the input step-down module 4 in the measuring device converts it into a low-voltage signal for subsequent modules to process. Alternatively, it can be a high-voltage probe, in which case the input step-down module 4 is not required, and the voltage signal output by the probe is a low-voltage signal that can be directly processed by subsequent modules.

[0087] As one or more implementations, the current sensor described above can be a current probe or a Hall current sensor, used to convert the current signal into a low-voltage signal for input to subsequent modules for processing.

[0088] In addition to the modules mentioned above, this embodiment also includes a measuring device housing 11 as shown in Figures 4(a)-4(d), wherein the touch display module 9, the voltage and current acquisition interface 3, and the power supply module 1 are mounted on the device housing 11, and the motor control module 2, the input step-down module 4, the voltage and current signal AD conversion module 5, the voltage zero-crossing detection module 7, the storage module 8, the data communication module 9, and the microcontroller module 10 are mounted inside the device housing 11.

[0089] The power supply module mentioned above can be a 12V lithium battery or other portable power source as shown in Figure 4(c), or it can be a DC power supply module built into the housing as shown in Figure 4(d) to convert the 220V AC mains power to 12V, and then convert the 12V voltage to -12V and 5V for use by the various modules of the test device.

[0090] Example 2

[0091] This embodiment provides a method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor, including:

[0092] S1: Power the permanent magnet synchronous motor under test through an external power supply;

[0093] S2: Measure the line voltage of the three-phase windings of the motor. U ab , U bc and U ca The effective value of the period is used to check whether the three-phase windings of the motor are symmetrical and whether there are any broken wires or short circuits between turns. If the line voltage is symmetrical, then proceed to step S3.

[0094] S3: Measure the no-load back electromotive force of the permanent magnet synchronous motor online, record the value, and execute step S4;

[0095] S4: Continuously measure the line voltage of the three-phase windings of the motor and the phase current of one phase, and calculate the active power, reactive power and power factor;

[0096] S5: Post-processing of measurement data, calculating the effective values ​​of voltage and current within a continuous measurement cycle, and calculating the maximum, minimum, average, instantaneous values ​​and waveforms of active power, reactive power, apparent power, and power factor;

[0097] S6: Save and record the test data related to the no-load back EMF and power factor of the permanent magnet synchronous motor under test.

[0098] The above measurement method requires verifying the balance of the three-phase load of the permanent magnet synchronous motor. It is suitable for measuring motors operating in steady state or with slow dynamic changes. This method can be applied to most industrial applications of permanent magnet motors. Step S2 involves measuring the line voltage of the three-phase windings. U ab , U bc and U ca The effective value of the period is determined, and the difference between the line voltages is verified. If the difference between each pair is within 3%, it can be determined that the current motor is operating symmetrically, and the following measurement steps can be performed.

[0099] In the above measurement method, the specific implementation method of step S3 is as follows:

[0100] Q1: Real-time acquisition of the line voltage of the three-phase stator windings of the motor U and voltage frequency f ;

[0101] Q2: Set the voltage capture frequency f 1. Rated operating frequency of permanent magnet synchronous motor f 2;

[0102] Q3: Instantly disconnect the armature winding of the permanent magnet synchronous motor under test to open the circuit, and then proceed to step Q4;

[0103] Q4: After the armature is de-energized, the rotor speed increases or decreases, corresponding to an increase or decrease in the frequency of the no-load back electromotive force. When the frequency f = f1, store the discrete waveform of the back electromotive force at frequency f1. {E 1 …E n } And proceed to step Q5;

[0104] Q5: Calculate the average value of the waveform in Q4. And the waveform is equivalent to a frequency of f 1. The average value over the period is E A sine wave of 1 is generated, and step Q6 is executed;

[0105] Q6: The frequency is... f 1. The average value over the period is E Frequency reduction is performed on a sine wave of 1, based on... The average period of the sine wave at frequency f2 is obtained. E 2. Then proceed to step Q7;

[0106] Q7: Press averaging the sine waveform E 2 converted to the effective value of a sine waveform E 0, this value is the effective value of the no-load back electromotive force of the permanent magnet synchronous motor to be measured, and step Q8 is executed;

[0107] Q8: Reconnect the permanent magnet synchronous motor to the power supply circuit, and the motor will return to normal operation.

[0108] The above testing process is as follows: Figure 5 As shown, by following the steps above, the no-load back electromotive force of the permanent magnet synchronous motor under test can be obtained. This value has important reference significance for the given value of the supply voltage of the permanent magnet motor under test at different load rates.

[0109] like Figure 2 As shown, the measuring device using the above measurement method is connected to the permanent magnet synchronous motor under test as illustrated to complete the above back electromotive force test steps. The testing device can obtain the values ​​of the three-phase voltage signals of the permanent magnet synchronous motor in real time through an externally input voltage signal. U and frequency fMeanwhile, the testing device outputs a motor control signal to control the on / off state of the motor, so as to apply a power-off or power-on control signal to the motor under test in steps Q3 and Q8.

[0110] In the above measurement method, the specific implementation method of step S4 is as follows:

[0111] Y1: Total acquisition time for calculating the power factor based on the current working cycle of the permanent magnet motor under test. T Total number of collections N And calculate the time interval between single data collections. The current number of collections P Initialize to 0;

[0112] Y2: Select the phase of the current to be measured. The phase to be measured can be any one of phases A, B, and C.

[0113] Y3: Start measurement and compare with the current number of data collections. P Total number of collections N The size, if P≤N Execute step Y4, if P>N Then proceed to step Y5;

[0114] Y4: Samples and decomposes the voltage and current of the motor, calculates power-related parameters, and records the current sampling count. P Add 1, return to step Y3;

[0115] Y5: After data acquisition is complete, proceed to step S5 to perform post-processing of the power data.

[0116] In the above measurement method, the steps for calculating the average value of the measured active power and power factor sequences in step S5 are as follows:

[0117] K1: Based on the power acquisition steps described above, the active power sequence is obtained. {P 1 ,…,P N } Power factor sequence {λ 1 ,…,λ N } and execute step K2;

[0118] K2: Calculate the average of the absolute values ​​of the above active power and power factor sequences, i.e. , And execute step K3;

[0119] K3: Based on the results of the last active power calculation P N The positive and negative values ​​are obtained k Then the average value , ,in .

[0120] In the sub-process of step S4 of the above-mentioned method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor, the total acquisition time of the power factor in step Y1 is determined by the working cycle of the permanent magnet motor under test. t The decision is generally based on the total collection time. T Set as work cycle t The total acquisition time is an integer multiple of the time limit. If the motor under test is operating in a steady state without periodic dynamic processes, then the total acquisition time is... T It can be flexibly configured according to user needs.

[0121] In the sub-process S4 of the above-mentioned method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor, step Y2 uses different combinations of line voltage and current phase to calculate the motor's power factor based on the selection of different current phases. If current phase A is selected, then the line voltage is used... U ab and I a To calculate the motor power factor, if current phase B is selected, then the line voltage can be used. U bc and I b To calculate the motor power factor, if the current phase is selected as C, then the line voltage can be used. U ca and I c Calculate the motor power factor.

[0122] In the sub-process of step S4 of the above-mentioned method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor, the specific implementation method of step Y4 is as follows:

[0123] Z1: Frequency for measuring input voltage f in And set the number of harmonic analyses. N fft ,according to f in and N fft Calculate the voltage and current sampling frequency required for the current power acquisition. f 采 and execute step Z2;

[0124] Z2: Based on the selected current phase, at the sampling rate f 采 The voltage and current are collected, with 64 voltage data points and 64 current data points collected respectively, forming the voltage array and current array for the current power acquisition time P, and then step Z3 is executed;

[0125] Z3: Based on the FFT (Fast Fourier Transform) algorithm, the current power acquisition time... P The voltage and current signals are decomposed to obtain the fundamental frequency and each harmonic. {U P,1 , …, U P,N } , {I P,1 , …, I P,N } and execute step Z4;

[0126] Z4: Calculate the current power acquisition frequency based on the fundamental frequency and harmonics obtained from the decomposition. P The effective values ​​of voltage and current, effective voltage value RMS current value and execute step Z5;

[0127] Z5: Calculate the current power acquisition time based on the following formulas. P Apparent power S P Active power P P reactive power Q P and power factor λ P :

[0128]

[0129]

[0130]

[0131]

[0132] in, k F The harmonic active power compensation coefficient is taken as . In the above formulas, Indicates the current power sampling time P The fundamental voltage RMS value, Indicates the current power sampling time P The effective value of the fundamental current, Indicates the current power sampling time P The fundamental voltage phase, Indicates the current power sampling time P The phase of the fundamental current.

[0133] In the sub-process of step Y4 of the above-mentioned comprehensive electrical parameter measurement method for permanent magnet synchronous motors, the voltage and current signal sampling frequency in step Z1 is... f采 The calculation is shown in the following formula:

[0134] ;

[0135] In the sub-process of step Y4 of the above-mentioned method for measuring the comprehensive electrical parameters of a permanent magnet synchronous motor, step Z2 requires that in each power acquisition... P Downsampling 64 times, the total signal sampling time should be less than the interval between each power acquisition. Δt 0.5 times, that is .

[0136] like Figure 3 As shown, the measuring device using the above measurement method is connected to the permanent magnet synchronous motor under test to complete the power factor test steps. The current phase selected in the diagram is the A-phase winding of the motor; therefore, the testing equipment will... U ab and I a Perform the power and power factor calculations according to the above calculation process. The connection method shown in the diagram is only one of the optional methods. As mentioned above, the current phase can also be selected as either phase B winding or phase C winding. The specific power calculation methods for the corresponding selection have been mentioned in the description above.

[0137] This embodiment enables real-time measurement of the voltage and current of the three-phase windings of the permanent magnet motor under test, and realizes a high-precision online method for measuring the back electromotive force of a permanent magnet synchronous motor and a low-cost, highly flexible power factor measurement method. This method allows engineers in various fields to easily adjust the motor's input voltage based on the current load rate of the permanent magnet motor by measuring the motor's back electromotive force and power factor in real time, thereby improving the power factor of the permanent magnet motor and reducing energy consumption. This invention is of great significance for energy saving, consumption reduction, and economical operation of permanent magnet motors.

[0138] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A method of measuring integrated electrical parameters of a permanent magnet synchronous motor, characterized in that, include: The permanent magnet synchronous motor under test is powered by an external power supply. The periodic effective value of the line voltage of the three-phase winding of the permanent magnet synchronous motor is measured in real time, and the no-load line back electromotive force of the permanent magnet synchronous motor is measured online by instantaneously switching the power supply circuit of the motor under test. The periodic effective value of the line voltage of the three-phase winding of the permanent magnet synchronous motor is measured. When the line voltage of the three-phase winding of the permanent magnet synchronous motor is symmetrical, the line voltage of the three-phase winding of the permanent magnet synchronous motor and the phase current of one phase are continuously measured to calculate the active power, reactive power, apparent power and power factor. The process of continuously measuring the line voltage of the three-phase windings of the permanent magnet synchronous motor and the phase current of one phase includes: According to the working period of the motor to be measured, the total collection time of the power factor is calculated T , the total collection times N , and the single collection interval time , the current collection times P is initialized to 0; Select the phase of the current to be measured, which can be any one of phases A, B, and C; Start measurement and compare with the current number of data collections. P Total number of collections N The size, if P≤N The voltage and current of the motor are sampled and their spectra decomposed, and power-related parameters are calculated. The current sampling count is also recorded. P Increment by 1, iterate and loop until... P>N Collection complete; The process of calculating active power, reactive power, apparent power, and power factor includes: Collect active power sequence within a continuous measurement period {P 1 ,…,P N } Power factor sequence {λ 1 ,…,λ N } ; The average of the absolute values of the active power sequence and the power factor sequence is calculated, i.e. , ; According to the last active power calculation result P N the positive and negative of which are obtained k The average value of the active power and the average value of the power factor are calculated as , where ; Calculate the average active power and average power factor over a continuous measurement period; Record the test data related to the no-load back electromotive force and power factor of the permanent magnet synchronous motor under test.

2. The method of claim 1, wherein, The symmetry of the line voltage of the three-phase windings of the permanent magnet synchronous motor is determined based on the difference between the line voltages of each two phases being within 3%.

3. The method of claim 1, wherein, The process of online measurement of the no-load back electromotive force of the permanent magnet synchronous motor includes: Real-time acquisition of line voltages of three-phase stator windings of an electric machine U and the frequency of the voltage f ; Set voltage capture frequency f 1. Rated operating frequency of the permanent magnet synchronous motor f 2. Instantly disconnect the armature winding of the permanent magnet synchronous motor under test to open the circuit; When the armature is de-energized, the rotor speed increases or decreases, and the corresponding frequency of the no-load back electromotive force increases or decreases. When the frequency... f = f At time 1, the discrete waveform of the back electromotive force at frequency f1 is stored. {E 1 …E n } ; calculating an average value of the back EMF discrete waveform and equating the waveform to a sinusoidal wave with a frequency of f1 and a period average value of E1; The sinusoidal wave with a frequency of f1 and a periodic average value of E1 is frequency-converted to obtain a sinusoidal wave with a frequency of f2 and a periodic average value of E2 according to E2 = E1 * (f2 / f1) According to The sine waveform average value E2 is converted into a sine waveform effective value E0, which is the no-load back electromotive force effective value of the permanent magnet synchronous motor to be measured. The permanent magnet synchronous motor was reconnected to the power supply circuit, and the motor returned to normal operation.

4. The method of claim 1, wherein, The sampling and spectral decomposition of the motor's voltage and current, and the calculation of primary power-related parameters, specifically include: Frequency of input voltage measurement f in And set the number of harmonic analyses. N fft ,according to f in and N fft Calculate the voltage and current sampling frequency required for the current power acquisition. f 采 ; According to the selected current phase, the sampling rate f 采 The voltage and current are collected, and the voltage data of several points and the current data of several points are collected respectively to form a voltage array and a current array of the current power collection time P. The voltage and current signals of the current power acquisition P are decomposed using the Fast Fourier Transform (FFT) algorithm to obtain the fundamental frequency and each harmonic. {U P,1 , …, U P,N } , {I P,1 , …, I P,N } ; Based on the fundamental and harmonic frequencies obtained from the decomposition, calculate the effective values ​​of the voltage and current at the current power acquisition level P. (Effective voltage value) RMS current value ; Calculate the current power sampling time using the following formulas. P Apparent power S P Active power P P reactive power Q P and power factor λ P : in, k F The harmonic active power compensation coefficient is taken as . , Indicates the current power sampling time. P The fundamental voltage RMS value, Indicates the current power sampling time. P The effective value of the fundamental current, Indicates the current power sampling time. P The fundamental voltage phase, Indicates the current power sampling time. P The phase of the fundamental current.

5. A measuring device for comprehensive electrical parameters of a permanent magnet synchronous motor using the method described in claim 1, characterized in that, include: The microcontroller module, and power supply module, motor control module, voltage and current signal AD conversion module, zero-crossing detection module, storage module, data transmission module and touch display module, all connected to the microcontroller module; The microcontroller module is used to send on / off signals to the motor under test through the motor control module based on the digital voltage signal and current signal input from the voltage and current signal AD conversion module and the zero-crossing signal input from the zero-crossing detection module. It collects the voltage signal of the permanent magnet motor after power failure at the desired sampling frequency and converts it into the back electromotive force of the motor under test. Alternatively, it collects the voltage and current signals of the permanent magnet synchronous motor at the desired sampling frequency and performs fast Fourier decomposition on the voltage and current signals to obtain the amplitude and phase of the fundamental wave and each harmonic. Based on this, it calculates the active power, reactive power and power factor of the permanent magnet synchronous motor under test in real time. According to the commands issued by the touch display module, it analyzes the measured data and sends the relevant data to the touch display module, or saves the data to the storage module, or uploads the test data through the data transmission module.

6. The device for measuring integrated electrical parameters of a permanent magnet synchronous machine according to claim 5, characterized in that, The motor control module is used to control the start and stop of the permanent magnet synchronous motor under test.

7. The device for measuring integrated electrical parameters of a permanent magnet synchronous motor according to claim 5, characterized in that, The voltage and current signal AD conversion module is also connected to the voltage and current acquisition interface, which is connected to the permanent magnet synchronous motor under test through a voltage sensor and a current sensor. The voltage sensor and current sensor are used to input the voltage and current signals of the permanent magnet synchronous motor under test to the voltage and current signal acquisition interface.

8. The device for measuring integrated electrical parameters of a permanent magnet synchronous machine according to claim 7, characterized in that, If the voltage sensor is connected to the permanent magnet synchronous motor under test using alligator clip-connected wires, then an input step-down module is connected between the voltage and current signal AD conversion module and the voltage and current acquisition interface. Alternatively, if the voltage sensor uses a high-voltage probe connected to the permanent magnet synchronous motor under test, then the voltage and current signal AD conversion module is directly connected to the voltage and current acquisition interface.

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