Frequency converter output voltage and current waveform quality closed-loop control method

Abstract

The invention discloses a frequency converter output voltage and current waveform quality closed-loop control method, and relates to the technical field of frequency converter motor power quality control. According to the three-phase asynchronous motor waveform quality phenomena of frequency converter output voltage harmonic distortion, frequency converter output current harmonic distortion, motor input current harmonic distortion and motor input current leakage, corresponding quantitative indexes are set, a voltage transformer and a current transformer are adopted, the DSP technology is combined, and the three-phase asynchronous motor waveform quality is obtained. Three-phase asynchronous motor waveform quality phenomena of frequency converter output voltage harmonic distortion, frequency converter output current harmonic distortion, motor input current harmonic distortion and motor input current leakage are rapidly identified; a self-adaptive control strategy is utilized to carry out quantitative analysis on three-phase asynchronous motor waveform quality indexes such as a frequency converter output voltage harmonic distortion rate, a frequency converter output current harmonic distortion rate, a motor input current harmonic distortion rate and a motor input leakage current value at the same time, and a weight factor is reasonably set.

Description

Technical Field

[0001] The present invention relates to the technical field of power quality control of inverter motors, and more specifically, to a closed-loop control method for the output voltage and current waveform quality of an inverter based on adaptive variable parameter control. Background Art

[0002] With the continuous increase in the control functions of inverters in three-phase asynchronous motors, the low-cost and high-performance closed-loop control design of a closed-loop controller for the output voltage and current waveform quality of an inverter with multiple control objectives for collaborative optimization control has become a great challenge. Existing closed-loop controllers for the output voltage and current waveform quality of inverters usually only target specific problems, adopt fixed output voltage and current waveform analysis methods, and combine closed-loop control technologies to form a closed-loop controller for the output voltage and current waveform quality of an inverter with special functions. For example, an inverter output voltage harmonic filter for suppressing output voltage harmonics, an inverter output current harmonic filter for suppressing output current harmonics, and a current leakage detector for monitoring leakage current.

[0003] The above closed-loop controllers for the output voltage and current waveform quality of inverters targeting specific inverter output waveform quality problems have obvious effects on specific problems. However, generally, they are powerless to other waveform quality problems. In some cases, they may even make other motor waveform quality problems more serious. When multiple motor waveform quality controllers are set to control the corresponding motor waveform quality problems respectively, the overall cost of motor waveform quality control is relatively high, and the volume and weight are also relatively large. In addition, due to the lack of mutual understanding between multiple motor waveform quality controllers, the actual performance may not reach the designed value. For example, the function of suppressing output voltage harmonics of an inverter may cause an increase in input current harmonics of the motor, and the reduction of the function of suppressing output current harmonics of the inverter may lead to an increase in leakage current of the motor. Summary of the Invention

[0004] In order to overcome the defects existing in the above-mentioned prior art, the present invention discloses a closed-loop control method for the output voltage and current waveform quality of an inverter, aiming to solve the problem of single control objective of the output power quality control of the existing three-phase asynchronous motor inverter from the software control method level. The purpose is to solve the technical problems existing in the existing three-phase asynchronous AC motor waveform quality control technology, such as the single control objective of the motor waveform quality of a single three-phase asynchronous motor waveform quality controller, the control effect may not reach the designed value when multiple three-phase asynchronous motor waveform quality controllers are used together, and the motor waveform quality controller targeting a specific three-phase asynchronous motor waveform quality problem may amplify other untreated three-phase asynchronous motor waveform quality problems in some cases.

[0005] Inventive concept of the present invention: First, the present invention identifies the waveform quality phenomenon of a three-phase asynchronous motor, then generates the weight coefficients of a multi-index adaptive objective function, and through a dynamic adjustment process, obtains the filtered reference current of a closed-loop controller for the output voltage and current waveforms of a frequency converter based on adaptive variable parameter control. Through closed-loop control, the comparison value of the pulse generator is updated, and through the isolation and amplification of the drive system, six drive signals are respectively applied to six SICMOS transistors in the closed-loop controller for the output voltage and current waveforms of the frequency converter based on adaptive variable parameter control, realizing multi-objective adaptive variable parameter closed-loop control.

[0006] To achieve the above objectives, the technical solution adopted by the present invention: A closed-loop control method for the output voltage and current waveforms of a frequency converter, comprising the following steps: I. Build a hardware platform Step 1: Connect a controller, as well as an AC voltage transformer and an AC current transformer for detecting the instantaneous value of the output voltage of the frequency converter, the instantaneous value of the output AC current, the instantaneous value of the input AC current of the motor, and the instantaneous value of the leakage current of the motor, to the three-phase AC asynchronous motor and the frequency converter. Preferably, in Step 1, a closed-loop controller for the output voltage and current waveforms of a frequency converter based on adaptive variable parameter control, as well as an additional AC voltage transformer PT1 for detecting the instantaneous value of the output voltage of the frequency converter, an AC current transformer CT1 for detecting the instantaneous value of the output AC current of the frequency converter, an AC current transformer CT2 for detecting the instantaneous value of the input AC current of the motor, and an AC current transformer CT3 for detecting the instantaneous value of the leakage current of the motor, are connected to the three-phase AC asynchronous motor and the frequency converter.

[0007] Preferably, in Step 1, each phase of the closed-loop controller for the output voltage and current waveforms of a frequency converter based on adaptive variable parameter control includes three inductors, three resistors, three capacitors, and a switching device composed of six SICMOS transistors.

[0008] Preferably, in Step 1, after the three inductors are respectively connected in series with the three SICMOS transistors, they are arranged between the output point of the frequency converter and the input point of the motor; the three resistors are respectively connected in series with the other three SICMOS transistors; the three capacitors are respectively connected in series with the three resistors; the other three SICMOS transistors are respectively connected to the input point of the motor; the other ends of the three capacitors are connected to each other and connected to the neutral point N of the power grid.

[0009] Preferably, in step 1, the AC voltage transformer PT1, the AC current transformer CT1, the AC current transformer CT2, and the AC current transformer CT3 constitute an isolation conditioning circuit, and provide the electrical parameter information necessary for adaptive control to the inverter output voltage and current waveform quality closed-loop controller based on adaptive variable parameter control, including the inverter output three-phase voltage, the inverter output three-phase current, the motor input three-phase current, and the motor leakage current.

[0010] 2. Electrical parameter information detection Step 2: Using an AC voltage transformer and an AC current transformer to detect the instantaneous value of the inverter output voltage, the instantaneous value of the inverter output AC current, the instantaneous value of the motor input AC current, and the instantaneous value of the motor leakage current; Preferably, in step 2, the instantaneous value of the inverter output voltage is detected by the AC voltage transformer PT1, the instantaneous value of the inverter output AC current is detected by the AC current transformer CT1, the instantaneous value of the motor input AC current is detected by the AC current transformer CT2, and the instantaneous value of the motor leakage current is detected by the AC current transformer CT3.

[0011] 3. Electrical parameter information sampling Step 3: transform the detected voltage instantaneous value and current instantaneous value into voltage signal amplitude and current signal amplitude, and obtain the corresponding instantaneous values ​​after transformation; Preferably, in step 3, a conditioning circuit is used to transform the voltage signal amplitude and the current signal amplitude of the detected instantaneous value of the inverter output voltage, the instantaneous value of the inverter output AC current, the instantaneous value of the motor input AC current and the instantaneous value of the motor leakage current, and the sampling module provided by the DSP chip is used to obtain the corresponding instantaneous value after the transformation.

[0012] In the present invention, the DSP chip refers to a chip capable of implementing digital signal processing technology, which is installed in the controller.

[0013] 4. Calculate the actual value of the motor running power quality index Step 4: Calculate the actual values ​​of the motor power quality indicators using the transformed corresponding instantaneous values, including the inverter output voltage harmonic distortion rate, the inverter output current harmonic distortion rate, the motor input current harmonic distortion rate, and the motor leakage current; Preferably, step 4 includes: through fast calculation of DSP, according to the calculation method specified in the existing IEC61000-4-30 power quality standard, real-time calculation is performed to obtain the actual value of the motor performance operating index, including: the harmonic distortion rate of the inverter output voltage, the harmonic distortion rate of the inverter output current, the harmonic distortion rate of the motor input current, and the motor leakage current.

[0014] Preferably, step 4 comprises: Through the rapid calculation of the DSP, the three-phase output voltage of the frequency converter, the three-phase output current of the frequency converter, and the three-phase input current of the motor are obtained; Through the rapid calculation of the DSP, the harmonic distortion rate of the output voltage of the frequency converter is obtained; Through the rapid calculation of the DSP, the harmonic distortion rate of the output current of the frequency converter is obtained; Through the rapid calculation of the DSP, the harmonic distortion rate of the input current of the motor is obtained; Through the rapid calculation of the DSP, the leakage current of the motor is obtained.

[0015] V. Generation of weight coefficients Step 5: Generate the weight coefficients of respective indicators according to the actual values of the power quality indicators of the motor operation; Preferably, the step 5 includes: Define the weight coefficient of the harmonic distortion rate of the output voltage of the frequency converter and calculate it; Define the weight coefficient of the harmonic distortion rate of the output current of the frequency converter and calculate it; Define the weight coefficient of the harmonic distortion rate of the input current of the motor and calculate it; Define the weight coefficient of the leakage current of the motor and calculate it.

[0016] VI. Calculation of the given value of the filtering current for the objective function Step 6: Use the power quality indicators of the motor operation and their weight coefficients to define an objective function with the given value of the filtering current as the objective, and use the objective function to calculate the given value of the filtering current; VII. Calculation of the input amount of the filter Step 7: Use the output current of the AC current transformer of the frequency converter output and the output current of the AC current transformer of the motor input to obtain the actual value of the filtering current, and compare it with the given value of the filtering current to judge the input amount of the filter; Preferably, the step 7 includes: calculating the actual value of the filtering current according to the output current of the AC current transformer CT1 of the frequency converter output and the output current of the AC current transformer CT2 of the motor input of the closed-loop controller for the waveform quality of the output voltage and current of the frequency converter based on the adaptive variable parameter control; If the given value of the filtering current is greater than the actual value of the filtering current, increase the filter bank; If the given value of the filtering current is less than the actual value of the filtering current, reduce the filter bank; If the given value of the filtering current is equal to the actual value of the filtering current, keep the number of the filter bank unchanged.

[0017] VIII. Generation of the switching quantity of the SICMOS tube Step 8: Generate the switching quantity of the SICMOS tube for the closed-loop controller of the output voltage and current waveform quality of the frequency converter based on adaptive variable parameter control according to the input quantity of the filter.

[0018] Preferably, step 8 includes: Using the pulse generation module built in the DSP to generate control pulses, and driving the six SICMOS tubes of the device for the closed-loop controller of the output voltage and current waveform quality of the frequency converter based on adaptive variable parameter control through an isolation and amplification circuit.

[0019] IX. Redetect the electrical parameter information Step 9: After the output current of the closed-loop controller of the output voltage and current waveform quality of the frequency converter based on adaptive variable parameter control works for a period of time, redetect the electrical parameter information; Preferably, step 9 includes: After the output current of the closed-loop controller of the output voltage and current waveform quality of the frequency converter based on adaptive variable parameter control works for a period of time, detect the instantaneous value of the output voltage of the frequency converter through the AC voltage transformer PT1, detect the instantaneous value of the output AC current of the frequency converter through the AC current transformer CT1, detect the instantaneous value of the input AC current of the motor through the AC current transformer CT2, and detect the instantaneous value of the leakage current of the motor through the AC current transformer CT3.

[0020] X. Calculation of the harmonic distortion rate of the output voltage of the frequency converter Step 10: Calculate the harmonic distortion rate of the output voltage of the frequency converter using the detected electrical parameter information. If the harmonic distortion rate of the output voltage of the frequency converter exceeds the standard, adjust the weight coefficient of the harmonic distortion rate of the output voltage of the frequency converter; otherwise, keep the weight coefficient of the harmonic distortion rate of the output voltage of the frequency converter unchanged. Preferably, step 10 includes: Step 10.1: If the harmonic distortion rate of the output voltage of the frequency converter is greater than the designed value of the harmonic distortion rate of the output voltage of the frequency converter, increase the weight coefficient of the harmonic distortion rate of the output voltage of the frequency converter by 1%, and enter step 10.4; Step 10.2: If the harmonic distortion rate of the output voltage of the frequency converter is lower than the designed value of the harmonic distortion rate of the output voltage of the frequency converter and lower than 0.5 times the designed value, reduce the harmonic distortion rate of the output voltage of the frequency converter by 1%, and enter step 10.4; Step 10.3: If neither 10.1 nor 10.2 is applicable, maintain the weight coefficient of the harmonic distortion rate of the output voltage of the frequency converter unchanged, and enter step 10.4; Step 10.4: Keep the weight coefficient of the harmonic distortion rate of the output voltage of the frequency converter unchanged for a period of time, observe the change of the waveform quality phenomena of other three-phase asynchronous motors, and enter step 11.

[0021] XI. Calculation of the harmonic distortion rate of the output current of the frequency converter Step 11: Calculate the harmonic distortion rate of the inverter output current using the detected electrical parameter information. If the harmonic distortion rate of the inverter output current exceeds the standard, adjust the weight coefficient of the harmonic distortion rate of the inverter output current; otherwise, keep the weight coefficient of the harmonic distortion rate of the inverter output current unchanged. Preferably, step 11 includes: Step 11.1: If the harmonic distortion rate of the inverter output current is greater than the designed value of the harmonic distortion rate of the inverter output current, increase the weight coefficient of the harmonic distortion rate of the inverter output current by 1%, and proceed to step 11.4; Step 11.2: If the harmonic distortion rate of the inverter output current is lower than the designed value of the harmonic distortion rate of the inverter output current and lower than 0.5 times the designed value, reduce the weight coefficient of the harmonic distortion rate of the inverter output current by 1%, and proceed to step 11.4; Step 11.3: If neither 11.1 nor 11.2 applies, keep the weight coefficient of the harmonic distortion rate of the inverter output current unchanged, and proceed to step 11.4; Step 11.4: Keep the weight coefficient of the harmonic distortion rate of the inverter output current unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to step 12.

[0022] XII. Calculation of the harmonic distortion rate of the motor input current Step 12: Calculate the harmonic distortion rate of the motor input current using the detected electrical parameter information. If the harmonic distortion rate of the motor input current exceeds the standard, adjust the weight coefficient of the harmonic distortion rate of the motor input current; otherwise, keep the weight coefficient of the harmonic distortion rate of the motor input current unchanged. Preferably, step 12 includes: Step 12.1: If the harmonic distortion rate of the motor input current is greater than the designed value of the harmonic distortion rate of the motor input current, increase the weight coefficient of the harmonic distortion rate of the motor input current by 1%, and proceed to step 12.4; Step 12.2: If the harmonic distortion rate of the motor input current is lower than the designed value of the harmonic distortion rate of the motor input current and lower than 0.5 times the designed value, reduce the weight coefficient of the harmonic distortion rate of the motor input current by 1%, and proceed to step 12.4; Step 12.3: If neither 12.1 nor 12.2 applies, maintain the weight of the harmonic distortion rate of the motor input current unchanged, and proceed to step 12.4; Step 12.4: Keep the weight coefficient of the harmonic distortion rate of the motor input current unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to step 13.

[0023] XIII. Calculation of the motor leakage current Step 13: Calculate the motor leakage current using the detected electrical parameter information. If the motor leakage current exceeds the standard, adjust the weight coefficient of the motor leakage current; otherwise, keep the weight coefficient of the motor leakage current unchanged. Preferably, step 13 includes: Step 13.1: If the motor leakage current is greater than the designed value of the motor leakage current, increase the weight coefficient of the motor leakage current by 1% and proceed to step 13.4. Step 13.2: If the motor leakage current is lower than the designed value of the motor leakage current and lower than 0.5 times the designed value, reduce the weight coefficient of the motor leakage current by 1% and proceed to step 13.4. Step 13.3: If neither 13.1 nor 13.2 is applicable, maintain the weight coefficient of the motor leakage current unchanged and proceed to step 13.4. Step 13.4: Keep the weight coefficient of the motor leakage current unchanged for a period of time, observe the changes in the waveform quality phenomena of the other three-phase asynchronous motors, and proceed to step 14.

[0024] Fourteen. Update Pulse Step 14: Apply the pulse generation module built into the DSP to generate control pulses. Through the isolation and amplification circuit, drive the six SICMOS tubes of the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control, and adjust the on and off times of the six SICMOS according to the weight coefficient to control the magnitude of the three-phase filter current of the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control.

[0025] Advantages of the present invention: The present invention sets corresponding quantitative indicators for the three-phase asynchronous motor waveform quality phenomena of the inverter output voltage harmonic distortion, the inverter output current harmonic distortion, the motor input current harmonic distortion, and the motor input current leakage, and adopts voltage and current transformers, combined with DSP technology, to quickly identify the three-phase asynchronous motor waveform quality phenomena of the inverter output voltage harmonic distortion, the inverter output current harmonic distortion, the motor input current harmonic distortion, and the motor input current leakage, and uses an adaptive control strategy to simultaneously adjust the inverter output voltage harmonic distortion rate, the inverter output current harmonic distortion rate, the motor input current harmonic distortion rate, and the motor input leakage. The waveform quality indicators of three-phase asynchronous motors such as dew current value are quantitatively analyzed, weight factors are reasonably set, a multi-indicator adaptive objective function is constructed, the value of the multi-indicator adaptive objective function is calculated, and closed-loop control is performed, so that the waveform quality problems of multiple three-phase asynchronous motors are alleviated at the same time, and multiple indicators of the waveform quality of the three-phase asynchronous motor are optimized at the same time. The treatment of the waveform quality problem of a single three-phase asynchronous motor will not aggravate the waveform quality problems of other three-phase asynchronous motors. Multiple problems of the waveform quality of the three-phase asynchronous motor are dealt with as a whole and at the same time from the root, thereby realizing multi-objective variable parameter adaptive control of the waveform quality of the three-phase asynchronous motor. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is an electrical system configuration diagram of the inverter output voltage and current waveform quality closed-loop controller based on adaptive variable parameter control of the present invention; Figure 2 It is the main circuit diagram of the invention of the inverter output voltage and current waveform quality closed-loop controller based on adaptive variable parameter control; Figure 3 It is a control principle diagram of a closed-loop control method for the quality of the output voltage and current waveform of a frequency converter based on adaptive variable parameter control; Figure 4 The invention is a control flow chart of a closed-loop control method for output voltage and current waveform quality of a frequency converter based on adaptive variable parameter control.

[0027] In the figure: 1. Closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 2. Main circuit of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 3. Shunt absorption resistor in the main circuit of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 4. Control board of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 5. Control algorithm of the control board of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 6. Three-phase AC asynchronous motor input waveform quality phenomenon recognition module in the control algorithm of the control board of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 7. Adaptive weight coefficient generation module in the control algorithm of the control board of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 8. Equipment body of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 9. Phase C circuit in the A, B, and C phase circuits of the main circuit of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 10. Pulse generation module; 11. Isolation and amplification circuit; 12. Series-connected SICMOS transistors in the main circuit of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 13. Series-connected inductor in the main circuit of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 14. Parallel-connected SICMOS in the main circuit of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 15. Shunt absorption resistor in the main circuit of the closed-loop controller for the waveform quality of the output voltage and current of a frequency converter with adaptive variable parameters; 16. AC current transformer CT3 for detecting the leakage current of the motor; 17. Sampling module. Specific embodiments

[0028] The following will clearly and completely describe the concept, specific structure, and technical effects of the present invention in combination with embodiments and drawings to fully understand the purpose, features, and effects of the present invention.

[0029] The present invention discloses a closed-loop control method for the waveform quality of the output voltage and current of a frequency converter based on adaptive variable parameter control, including a closed-loop controller for the waveform quality of the output voltage and current of a frequency converter based on multi-objective variable parameter adaptive control connected between the frequency converter and a three-phase asynchronous AC motor, as well as additional AC voltage transformer PT1 for detecting the instantaneous value of the output voltage of the frequency converter, AC current transformer CT1 for detecting the instantaneous value of the output AC current of the frequency converter, AC current transformer CT2 for detecting the instantaneous value of the input AC current of the motor, and AC current transformer CT3 for detecting the instantaneous value of the leakage current of the motor, and is completed according to the following steps: collecting the instantaneous value of the output voltage of the frequency converter through voltage transformer PT1, and collecting the instantaneous values of the output AC current of the frequency converter, the input current of the motor, and the leakage current of the motor through current transformers CT1, CT2, and CT3; transforming the instantaneous values of the output voltage of the frequency converter, the output current of the frequency converter, the input current of the motor, and the leakage current of the motor through a conditioning circuit, and obtaining the corresponding discretized instantaneous values through the A / D sampling function of the DSP chip; through the fast operation of the DSP, calculating in real time the actual values of the waveform quality indexes of the three-phase asynchronous AC motor such as the harmonic distortion rate of the output voltage of the frequency converter, the harmonic distortion rate of the output current of the frequency converter, the harmonic distortion rate of the input current of the motor, and the leakage current of the motor; generating the weight coefficient of the adaptive weight function, and obtaining the reference current of the closed-loop controller for the waveform quality of the output voltage and current of the frequency converter based on adaptive variable parameter control after dynamically adjusting the weight coefficient; through closed-loop control, updating the comparison value of the pulse generator, and applying the drive signal to the SICMOS tube through the isolation and amplification of the drive system to achieve adaptive closed-loop control. The present invention is applicable to a closed-loop control method for the waveform quality of the output voltage and current of a frequency converter based on adaptive variable parameter control, and solves the following three problems existing in the existing waveform quality control technology of three-phase asynchronous AC motors: the waveform quality control target of a single three-phase asynchronous motor waveform quality controller is single, the control effect may not reach the design value when multiple three-phase asynchronous motor waveform quality controllers are used together, and the motor waveform quality controller for a specific three-phase asynchronous motor waveform quality problem may amplify other untreated three-phase asynchronous motor waveform quality problems in some cases.

[0030] The specific solution of this embodiment is as follows: A closed-loop control method for the waveform quality of the output voltage and current of a frequency converter, as Figure 1 、 2 shown in 3 and 4, includes the following steps: Step 1: Build a hardware platform In a three-phase AC asynchronous motor, a closed-loop controller for the waveform quality of the output voltage and current of a frequency converter based on adaptive variable parameter control is connected, as well as an additional AC voltage transformer PT1 for detecting the instantaneous value of the output voltage of the frequency converter, an AC current transformer CT1 for detecting the instantaneous value of the output AC current of the frequency converter, an AC current transformer CT2 for detecting the instantaneous value of the input AC current of the motor, and an AC current transformer CT3 for detecting the instantaneous value of the leakage current of the motor. As Figure 2 shown, each phase of the closed-loop controller for the waveform quality of the output voltage and current of the frequency converter based on adaptive variable parameter control includes inductors L1, L2, L3, resistors R1, R2, R3, capacitors C1, C2, C3, and a switching device composed of six SICMOS transistors A - F; the inductors L1, L2, L3 are respectively connected in series with the SICMOS transistors A, B, C and are arranged between the output point of the frequency converter and the input point of the motor; the resistors R1, R2, R3 are respectively connected in series with the SICMOS transistors D, E, F; the capacitors C1, C2, C3 are respectively connected in series with the resistors R1, R2, R3; the SICMOS transistors D, E, F are respectively connected to the input point of the motor; the other ends of the capacitors C1, C2, C3 are connected to each other and are connected to the neutral point N of the power grid.

[0031] Correspondingly, the AC voltage transformer PT1, the AC current transformer CT1, the AC current transformer CT2, and the leakage current transformer CT3 form an isolation conditioning circuit and provide the electrical parameter information necessary for adaptive control to the closed-loop controller for the waveform quality of the output voltage and current of the frequency converter based on adaptive variable parameter control, including the three-phase output voltage Ua, Ub, Uc of the frequency converter, the three-phase output current iaINV, ibINV, icINV of the frequency converter, the three-phase input current iaMOTOR, ibMOTOR, icMOTOR of the motor, and the leakage current Idc1 of the motor.

[0032] Step 2, Detection of electrical parameter information Detect the instantaneous value of the output voltage of the frequency converter through the AC voltage transformer PT1, detect the instantaneous value of the output AC current of the frequency converter through the AC current transformer CT1, detect the instantaneous value of the input AC current of the motor through the AC current transformer CT2, and detect the instantaneous value of the leakage current of the motor through the AC current transformer CT3.

[0033] Step 3, Sampling of electrical parameter information The instantaneous value of the output voltage of the frequency converter, the instantaneous value of the output AC current of the frequency converter, the instantaneous value of the input AC current of the motor, and the instantaneous value of the leakage current of the motor detected in step 2 are subjected to voltage signal amplitude transformation (such as the transformation between 1000V and 5V) and current signal amplitude transformation (such as the transformation between 2000A / 5A) through the conditioning circuit, and the corresponding discretized instantaneous values are obtained by the A / D sampling module 17 built in the DSP chip; Step 4, calculate the actual values of the motor operation power quality indicators Through the fast operation of the DSP, according to the calculation methods specified in the existing IEC61000-4-30 power quality standard, the actual values of the motor performance operation indicators such as the harmonic distortion rate of the output voltage of the frequency converter INV_DUTHD, the harmonic distortion rate of the output current of the frequency converter INV_DITHD, the harmonic distortion rate of the input current of the motor MOTOR_DITHD, and the leakage current of the motor MOTOR_DI are calculated in real time; Step 4.1, assume that the three-phase output voltages of the frequency converter are ua, ub, and uc respectively, the three-phase output currents of the frequency converter are iaINV, ibINV, and icINV respectively, and the three-phase input currents of the motor are iaMOTOR, ibMOTOR, and icMOTOR respectively; Step 4.2, through the fast calculation of the DSP, the harmonic distortion rate of the output voltage of the frequency converter is obtained as INV_DUTHD; Step 4.3, through the fast calculation of the DSP, the harmonic distortion rate of the output current of the frequency converter is obtained as INV_DITHD; Step 4.4, through the fast calculation of the DSP, the harmonic distortion rate of the input current of the motor is obtained as MOTOR_DITHD; Step 4.5, through the fast calculation of the DSP, the leakage current of the motor is obtained as MOTOR_DI; Step 5, generate the weight coefficients of each motor performance operation indicator According to the actual values of the motor performance operation indicators, the weight coefficients of their respective indicators are generated. The parameters and calculation methods of the specific weight coefficients are shown in steps 5.1-5.4; Step 5.1, define the weight coefficient of the harmonic distortion rate of the output voltage of the frequency converter as m_INV_DUTHD, and the calculation method is m_INV_DUTHD = INV_DUTHD; Step 5.2, define the weight coefficient of the harmonic distortion rate of the output current of the frequency converter as m_INV_DITHD, and the calculation method is m_INV_DITHD = INV_DITHD; Step 5.3, define the weight coefficient of the harmonic distortion rate of the input current of the motor as m_MOTOR_DITHD, and the calculation method is m_MOTOR_DITHD = MOTOR_DITHD; Step 5.4, define the weight coefficient of the motor leakage current as m_MOTOR_DI, and the calculation method is m_MOTOR_DI = MOTOR_DI; Step 6, define the objective function Ilvboref with the filtered current set value as the target to obtain the current set value; Objective function Ilvboref = m_INV_DUTHD * INV_DUTHD + m_INV_DITHD * INV_DITHD + m_MOTOR_DITHD * MOTOR_DITHD + m_MOTOR_DI * MOTOR_DI; Step 7, calculate the input amount of the filter; According to the output current of the inverter output AC current transformer CT1 and the output current of the motor input AC current transformer CT2 of the closed-loop controller for the waveform quality of the inverter output voltage and current based on adaptive variable parameter control, calculate the actual value Ilvbo of the filtered current. If Ilvboref is greater than Ilvbo, increase the filter bank.

[0034] If Ilvboref is less than Ilvbo, reduce the filter bank.

[0035] If Ilvboref is equal to Ilvbo, keep the number of filter banks unchanged.

[0036] Step 8, generate the switching quantity of the SICMOS tube of the closed-loop controller for the waveform quality of the inverter output voltage and current based on adaptive variable parameter control; Use the pulse generation module 10 built in the DSP to generate control pulses, and through the isolation and amplification circuit 11, drive the six SICMOS tubes A - F of the device of the closed-loop controller for the waveform quality of the inverter output voltage and current based on adaptive variable parameter control respectively.

[0037] Step 9, re-detect the electrical parameter information After the closed-loop controller for the waveform quality of the inverter output voltage and current based on adaptive variable parameter control works for a period of time with the output current, detect the instantaneous value of the inverter output voltage through the AC voltage transformer PT1, detect the instantaneous value of the inverter output AC current through the AC current transformer CT1, detect the instantaneous value of the motor input AC current through the AC current transformer CT2, and detect the instantaneous value of the motor leakage current through the AC current transformer CT3.

[0038] Step 10: Use the DSP to calculate the harmonic distortion rate INV_DUTHD of the inverter output voltage. If the harmonic distortion rate INV_DUTHD of the inverter output voltage exceeds the standard, adjust the weight coefficient m_INV_DUTHD of the harmonic distortion rate INV_DUTHD of the inverter output voltage. Otherwise, keep the weight coefficient m_INV_DUTHD of the harmonic distortion rate INV_DUTHD of the inverter output voltage unchanged and proceed to Step 11; Step 10.1: If INV_DUTHD is greater than the designed value of the harmonic distortion rate of the inverter output voltage, update m_INV_DUTHD according to the formula m_INV_DUTHD = 1.01 * m_INV_DUTHD and proceed to Step 10.4; Step 10.2: If INV_DUTHD is lower than the designed value of the harmonic distortion rate of the inverter output voltage and lower than 0.5 times the designed value, update m_INV_DUTHD according to the formula m_INV_DUTHD = 0.99 * m_INV_DUTHD and proceed to Step 10.4; Step 10.3: If neither 10.1 nor 10.2 is applicable, keep m_INV_DUTHD unchanged and proceed to Step 10.4; Step 10.4: Keep m_INV_DUTHD unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 11.

[0039] Step 11: Use the DSP to calculate the harmonic distortion rate INV_DITHD of the inverter output current. If the harmonic distortion rate INV_DITHD of the inverter output current exceeds the standard, adjust the weight coefficient m_INV_DITHD of the harmonic distortion rate INV_DITHD of the inverter output current. Otherwise, keep the weight coefficient m_INV_DITHD of the harmonic distortion rate INV_DITHD of the inverter output current unchanged and proceed to Step 12; Step 11.1: If INV_DITHD is greater than the designed value of the harmonic distortion rate of the inverter output current, update m_INV_DITHD according to the formula m_INV_DITHD = 1.01 * m_INV_DITHD and proceed to Step 11.4; Step 11.2: If INV_DITHD is lower than the designed value of the harmonic distortion rate of the inverter output current and lower than 0.5 times the designed value, update m_INV_DITHD according to the formula m_INV_DITHD = 0.99 * m_INV_DITHD and proceed to Step 11.4; Step 11.3: If neither 11.1 nor 11.2 is applicable, keep m_INV_DITHD unchanged and proceed to Step 11.4; Step 11.4, keep m_INV_DITHD unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 12.

[0040] Step 12, use the DSP to calculate the harmonic distortion rate MOTOR_DITHD of the motor input current. If the harmonic distortion rate MOTOR_DITHD of the motor input current exceeds the standard, adjust the weighting coefficient m_MOTOR_DITHD of the harmonic distortion rate MOTOR_DITHD of the motor input current. Otherwise, keep the weighting coefficient m_MOTOR_DITHD of the harmonic distortion rate MOTOR_DITHD of the motor input current unchanged, and proceed to Step 13; Step 12.1, if MOTOR_DITHD is greater than the designed value of the harmonic distortion rate of the motor input current, update m_MOTOR_DITHD according to the formula m_MOTOR_DITHD = 1.01 * m_MOTOR_DITHD, and proceed to Step 12.4; Step 12.2, if MOTOR_DITHD is lower than the designed value of the harmonic distortion rate of the motor input current and lower than 0.5 times the designed value, update m_MOTOR_DITHD according to the formula m_MOTOR_DITHD = 0.99 * m_MOTOR_DITHD, and proceed to Step 12.4; Step 12.3, if neither 12.1 nor 12.2 applies, keep m_MOTOR_DITHD unchanged, and proceed to Step 12.4; Step 12.4, keep m_MOTOR_DITHD unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 13.

[0041] Step 13, use the DSP to calculate the leakage current MOTOR_DI of the motor. If the leakage current MOTOR_DI of the motor exceeds the standard, adjust the weighting coefficient m_MOTOR_DI of the leakage current MOTOR_DI of the motor. Otherwise, keep the weighting coefficient m_MOTOR_DI of the leakage current MOTOR_DI of the motor unchanged, and proceed to Step 14; Step 13.1, if MOTOR_DI is greater than the designed value of the leakage current of the motor, update m_MOTOR_DI according to the formula m_MOTOR_DI = 1.01 * m_MOTOR_DI, and proceed to Step 13.4; Step 13.2, if MOTOR_DI is lower than the designed value of the leakage current of the motor and lower than 0.5 times the designed value, update m_MOTOR_DI according to the formula m_MOTOR_DI = 0.99 * m_MOTOR_DI, and proceed to Step 13.4; Step 13.3, if neither 13.1 nor 13.2 is applicable, maintain m_MOTOR_DI unchanged and proceed to Step 13.4; Step 13.4, keep m_MOTOR_DI unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 14.

[0042] Step 14, apply the pulse generation module built into the DSP to generate control pulses, and through the isolation and amplification circuit, drive the six SICMOS transistors A - F of the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control, adjust the on and off times of the six SICMOS A - F, so as to control the magnitudes of the three-phase filtered currents ialvbo, iblvbo, and iclvbo of the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control.

[0043] The above has specifically described the embodiments of the present invention, but the present invention is not limited to the described embodiments. Those skilled in the art can also make various equivalent variations or substitutions without departing from the spirit of the present invention, and these equivalents or substitutions are all included within the scope defined by the claims of the present invention.

Claims

1. A closed-loop control method for the waveform quality of the output voltage and current of a frequency converter, characterized in that, It includes the following steps: Step 1: Connect a controller, as well as an AC voltage transformer and an AC current transformer for detecting the instantaneous value of the output voltage of the frequency converter, the instantaneous value of the output AC current, the instantaneous value of the input AC current of the motor, and the instantaneous value of the leakage current of the motor, to the three-phase AC asynchronous motor and the frequency converter; Step 2: Use the AC voltage transformer and the AC current transformer to detect the instantaneous value of the output voltage of the frequency converter, the instantaneous value of the output AC current of the frequency converter, the instantaneous value of the input AC current of the motor, and the instantaneous value of the leakage current of the motor; Step 3: Perform transformation on the amplitude of the voltage signal and the amplitude of the current signal for the detected instantaneous voltage value and instantaneous current value, and obtain the corresponding transformed instantaneous values; Step 4: Use the corresponding transformed instantaneous values to calculate the actual values of the motor operation power quality indicators, including the output voltage harmonic distortion rate of the frequency converter, the output current harmonic distortion rate of the frequency converter, the input current harmonic distortion rate of the motor, and the leakage current of the motor; Step 5: Generate the weight coefficients for each indicator based on the actual values of the motor operation power quality indicators; Step 6: Define an objective function with the given value of the filtering current as the target using the motor operation power quality indicators and their weight coefficients, and calculate the given value of the filtering current using the objective function; Step 7: Use the output current of the AC current transformer of the frequency converter output and the output current of the AC current transformer of the motor input to obtain the actual value of the filtering current, and compare it with the given value of the filtering current to determine the input amount of the filter; Step 8: Generate the switching quantity of the SICMOS tube of the closed-loop controller for the output voltage and current waveform quality of the frequency converter based on adaptive variable parameter control according to the input amount of the filter; 2. The control method according to claim 1, wherein It also includes: Step 9: After the closed-loop controller for the output voltage and current waveform quality of the frequency converter based on adaptive variable parameter control has been operating the output current for a period of time, re-detect the electrical parameter information; Step 10: Calculate the output voltage harmonic distortion rate of the frequency converter using the detected electrical parameter information. If the output voltage harmonic distortion rate of the frequency converter exceeds the standard, adjust the weight coefficient of the output voltage harmonic distortion rate of the frequency converter, otherwise, keep the weight coefficient of the output voltage harmonic distortion rate of the frequency converter unchanged; Step 11: Calculate the output current harmonic distortion rate of the frequency converter using the detected electrical parameter information. If the output current harmonic distortion rate of the frequency converter exceeds the standard, adjust the weight coefficient of the output current harmonic distortion rate of the frequency converter, otherwise, keep the weight coefficient of the output current harmonic distortion rate of the frequency converter unchanged; Step 13: Calculate the input current harmonic distortion rate of the motor using the detected electrical parameter information. If the input current harmonic distortion rate of the motor exceeds the standard, adjust the weight coefficient of the input current harmonic distortion rate of the motor, otherwise, keep the weight coefficient of the input current harmonic distortion rate of the motor unchanged; Step 14: Calculate the leakage current of the motor using the detected electrical parameter information. If the leakage current of the motor exceeds the standard, adjust the weight coefficient of the leakage current of the motor, otherwise, keep the weight coefficient of the leakage current of the motor unchanged; Step 14: Apply the pulse generation module built in the DSP to generate control pulses. Through the isolation and amplification circuit, drive the six SICMOS transistors of the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control, and adjust the on and off times of the six SICMOS according to the weight coefficients to control the magnitude of the three-phase filtered current of the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control.

3. The control method according to claim 1, characterized in that In Step 1, connect the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control, as well as the additional AC voltage transformer PT1 for detecting the instantaneous value of the inverter output voltage, the AC current transformer CT1 for detecting the instantaneous value of the inverter output AC current, the AC current transformer CT2 for detecting the instantaneous value of the motor input AC current, and the AC current transformer CT3 for detecting the instantaneous value of the motor leakage current to the three-phase AC asynchronous motor and the inverter.

4. The control method according to claim 3, wherein In Step 1, each phase of the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control includes three inductors, three resistors, three capacitors, and a switching device composed of six SICMOS transistors; In Step 1, after the three inductors are respectively connected in series with the three SICMOS transistors, they are arranged between the inverter output point and the motor input point; the three resistors are respectively connected in series with the other three SICMOS transistors; the three capacitors are respectively connected in series with the three resistors; the other three SICMOS transistors are respectively connected to the motor input point; the other ends of the three capacitors are connected to each other and connected to the power grid neutral point N; In Step 1, the AC voltage transformer PT1, the AC current transformer CT1, the AC current transformer CT2, and the AC current transformer CT3 form an isolation conditioning circuit and provide the electrical parameter information necessary for adaptive control to the closed-loop controller for the output voltage and current waveform quality of the inverter based on adaptive variable parameter control, including the three-phase voltage output by the inverter, the three-phase current output by the inverter, the three-phase current input to the motor, and the motor leakage current.

5. The control method according to claim 1, characterized in that, In Step 2, detect the instantaneous value of the inverter output voltage through the AC voltage transformer PT1, detect the instantaneous value of the inverter output AC current through the AC current transformer CT1, detect the instantaneous value of the motor input AC current through the AC current transformer CT2, and detect the instantaneous value of the motor leakage current through the AC current transformer CT3.

6. The control method according to claim 1, wherein, In Step 3, use the conditioning circuit to perform the transformation of the voltage signal amplitude and the transformation of the current signal amplitude on the detected instantaneous values of the inverter output voltage, the inverter output AC current, the motor input AC current, and the motor leakage current, and use the sampling module built in the DSP chip to obtain the corresponding transformed instantaneous values.

7. The control method according to claim 1, wherein, Step 4 includes: through the fast operation of the DSP, according to the calculation method specified in the existing IEC61000-4-30 power quality standard, the actual values of the motor performance operation indicators are calculated in real time, including: the harmonic distortion rate of the inverter output voltage, the harmonic distortion rate of the inverter output current, the harmonic distortion rate of the motor input current, and the motor leakage current; Step 4 includes: Through the fast calculation of the DSP, the three-phase output voltage of the inverter, the three-phase output current of the inverter, and the three-phase input current of the motor are obtained; Through the fast calculation of the DSP, the harmonic distortion rate of the inverter output voltage is obtained; Through the fast calculation of the DSP, the harmonic distortion rate of the inverter output current is obtained; Through the fast calculation of the DSP, the harmonic distortion rate of the motor input current is obtained; Through the fast calculation of the DSP, the motor leakage current is obtained.

8. The control method according to claim 1, characterized in that, Step 5 includes: Define the weight coefficient of the harmonic distortion rate of the inverter output voltage and calculate it; Define the weight coefficient of the harmonic distortion rate of the inverter output current and calculate it; Define the weight coefficient of the harmonic distortion rate of the motor input current and calculate it; Define the weight coefficient of the motor leakage current and calculate it.

9. The control method according to claim 1, characterized in that Step 7 includes: according to the output current of the inverter output AC current transformer CT1 and the output current of the motor input AC current transformer CT2 of the closed-loop controller for the waveform quality of the inverter output voltage and current based on adaptive variable parameter control, the actual value of the filtered current is calculated; If the given value of the filtered current is greater than the actual value of the filtered current, the filter bank is increased; If the given value of the filtered current is less than the actual value of the filtered current, the filter bank is reduced; If the given value of the filtered current is equal to the actual value of the filtered current, the number of filter banks remains unchanged.

10. The control method according to claim 1, characterized in that Step 8 includes: using the pulse generation module built in the DSP to generate control pulses, and through the isolation and amplification circuit, driving the six SICMOS tubes of the device of the closed-loop controller for the waveform quality of the inverter output voltage and current based on adaptive variable parameter control respectively.

11. The control method according to claim 2, wherein, Step 9 includes: after the closed-loop controller for the waveform quality of the inverter output voltage and current based on adaptive variable parameter control works for a period of time in the output current, the instantaneous value of the inverter output voltage is detected through the AC voltage transformer PT1, the instantaneous value of the inverter output AC current is detected through the AC current transformer CT1, the instantaneous value of the motor input AC current is detected through the AC current transformer CT2, and the instantaneous value of the motor leakage current is detected through the AC current transformer CT3.

12. The control method according to claim 2, wherein Step 10 includes: Step 10.1: If the harmonic distortion rate of the inverter output voltage is greater than the designed value of the harmonic distortion rate of the inverter output voltage, increase it by 1% according to the weight coefficient of the harmonic distortion rate of the inverter output voltage, and enter Step 10.4; Step 10.2: If the harmonic distortion rate of the inverter output voltage is lower than the designed value of the harmonic distortion rate of the inverter output voltage and lower than 0.5 times the designed value, reduce the harmonic distortion rate of the inverter output voltage by 1%, and enter Step 10.4; Step 10.3: If neither 10.1 nor 10.2 is applicable, keep the weight coefficient of the output voltage harmonic distortion rate of the frequency converter unchanged and proceed to Step 10.4; Step 10.4: Keep the weight coefficient of the output voltage harmonic distortion rate of the frequency converter unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 11.

13. The control method according to claim 2, wherein The said Step 11 includes: Step 11.1: If the output current harmonic distortion rate of the frequency converter is greater than the designed value of the output current harmonic distortion rate of the frequency converter, increase the weight coefficient of the output current harmonic distortion rate of the frequency converter by 1% and proceed to Step 11.4; Step 11.2: If the output current harmonic distortion rate of the frequency converter is lower than the designed value of the output current harmonic distortion rate of the frequency converter and lower than 0.5 times the designed value, reduce the weight coefficient of the output current harmonic distortion rate of the frequency converter by 1% and proceed to Step 11.4; Step 11.3: If neither 11.1 nor 11.2 is applicable, keep the weight coefficient of the output current harmonic distortion rate of the frequency converter unchanged and proceed to Step 11.4; Step 11.4: Keep the weight coefficient of the output current harmonic distortion rate of the frequency converter unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 12.

14. The control method according to claim 2, wherein The said Step 12 includes: Step 12.1: If the input current harmonic distortion rate of the motor is greater than the designed value of the input current harmonic distortion rate of the motor, increase the weight coefficient of the input current harmonic distortion rate of the motor by 1% and proceed to Step 12.4; Step 12.2: If the input current harmonic distortion rate of the motor is lower than the designed value of the input current harmonic distortion rate of the motor and lower than 0.5 times the designed value, reduce the weight coefficient of the input current harmonic distortion rate of the motor by 1% and proceed to Step 12.4; Step 12.3: If neither 12.1 nor 12.2 is applicable, keep the weight of the input current harmonic distortion rate of the motor unchanged and proceed to Step 12.4; Step 12.4: Keep the weight coefficient of the input current harmonic distortion rate of the motor unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 13.

15. The control method according to claim 2, wherein The said Step 13 includes: Step 13.1: If the leakage current of the motor is greater than the designed value of the leakage current of the motor, increase the weight coefficient of the leakage current of the motor by 1% and proceed to Step 13.4; Step 13.2: If the leakage current of the motor is lower than the designed value of the leakage current of the motor and lower than 0.5 times the designed value, reduce the weight coefficient of the leakage current of the motor by 1% and proceed to Step 13.4; Step 13.3: If neither 13.1 nor 13.2 is applicable, keep the weight coefficient of the leakage current of the motor unchanged and proceed to Step 13.4; Step 13.4: Keep the weight coefficient of the leakage current of the motor unchanged for a period of time, observe the changes in the waveform quality phenomena of other three-phase asynchronous motors, and proceed to Step 14.

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