A high-efficiency energy-saving operation control method for a permanent magnet motor frequency converter

Abstract

The application provides a high-efficiency energy-saving operation control method of a permanent magnet motor frequency converter, which comprises the following steps: identifying an output frequency and obtaining frequency converter output data when the frequency converter drives the permanent magnet motor in a non-reverse dragging and speed reduction state; calling rated parameters of the frequency converter, calculating a load rate according to the obtained output data; obtaining a target power factor from a permanent magnet motor load rate and power factor curve when back electromotive force matches applied voltage; obtaining related data of the target power factor, calculating a running frequency corresponding back electromotive force according to a compensation curve; correcting the back electromotive force EMF according to an output voltage value lifting curve; reducing operation adjustment of the frequency converter; making the permanent magnet motor in a high-efficiency energy-saving state, outputting maximum torque, and adjusting output current to adapt to load torque, so that more energy-saving driving control is realized. The application avoids the problem that the increase of current on the stator winding of the permanent magnet synchronous motor leads to the increase of stator copper loss and iron loss and the reduction of motor efficiency.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of permanent magnet motor control, and particularly relates to a high-efficiency energy-saving operation control method of a permanent magnet motor frequency converter. BACKGROUND

[0002] A variable-frequency drive (VFD) is a variable-frequency drive V / F control, vector control and direct torque control of a motor by using variable-frequency technology and microelectronic technology, so as to achieve the purpose of speed regulation and is widely used. For example, in the field of permanent magnet synchronous motor applications, a frequency converter is generally used to realize frequency speed regulation control of a permanent magnet synchronous motor.

[0003] However, since the characteristic parameter of the permanent magnet synchronous motor, i.e., the back electromotive force, is difficult to accurately measure in real time, the back electromotive force will change greatly due to reasons such as reverse magnetic field, vibration, fault, temperature rise and the like, and then the back electromotive force and the power supply voltage cannot be matched and controlled.

[0004] The conventional frequency converter controls the permanent magnet motor by V / F control or vector control or direct torque control based on the rated voltage and the rated power, at this time, the current on the stator winding of the permanent magnet synchronous motor will rapidly increase, thereby causing the stator copper loss and iron loss to increase and the motor efficiency to decrease. With the continuous use of the permanent magnet synchronous motor, the temperature of the motor will continue to rise, and the use of the above-mentioned conventional frequency converter for frequency control of the permanent magnet synchronous motor will continuously cause the motor energy consumption to increase, the efficiency to decrease, and even damage the permanent magnet synchronous motor, and also cause the conventional frequency converter to fail and cannot be normally used. SUMMARY

[0005] The present application provides a high-efficiency energy-saving permanent magnet motor frequency converter operation control method, the method comprising:

[0006] S11, in the state of no reverse drag and speed reduction of the frequency converter driving the permanent magnet motor, identifying an output frequency f and acquiring an output power factor PF and an output active power P of the frequency converter;

[0007] S12, setting parameters of a rated frequency fe and a rated power Pe of the frequency converter, acquiring a rated electric power Pef allowed by the output frequency f from a load torque type and a V / F curve, and calculating a load rate LR according to the acquired output active power P;

[0008] S13, acquiring a target power factor PFm when the back electromotive force and the applied voltage are matched from a permanent magnet motor load rate and power factor curve; the forward target power factor is +PFm and the negative target power factor is -PFm;

[0009] S14, setting the frequency converter output current phase to lag behind the output voltage and to be inductive, and taking the forward power factor +PF;

[0010] The output current phase leads the output voltage, and is set to be capacitive, taking a negative power factor -PF;

[0011] S15, when detecting that the forward power factor +PF < the forward target power factor +PFm, the back electromotive force of the permanent magnet motor is lower than the output side voltage of the frequency converter, the output voltage is gradually reduced, and the forward power factor tends to the forward target power factor +PFm;

[0012] When it is detected that the forward power factor +PF ≥ the forward target power factor +PFm, the frequency f and the load rate LR corresponding to the output voltage U- of the frequency converter are recorded;

[0013] S16, when detecting that the negative power factor -PF > the negative target power factor -PFm, the back electromotive force of the permanent magnet motor is higher than the output side voltage of the frequency converter, the output voltage is gradually increased, and the negative power factor -PF tends to the negative target power factor -PFm;

[0014] When it is detected that the negative power factor -PF ≤ the negative target power factor -PFm, the frequency f and the load rate LR corresponding to the output voltage U+ of the frequency converter are recorded;

[0015] S17, the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR obtained by the step S15 or the step S16 are used to calculate the compensation value according to the compensation curve, and then the back electromotive force EMF=U± value corresponding to the operating frequency f is calculated;

[0016] If the operating frequency f is below the cutoff frequency, the corresponding back electromotive force EMF is calculated from the EMF / U boost curve below the cutoff frequency;

[0017] Then the frequency f / back electromotive force EMF / output voltage U curve of the frequency converter is refreshed, the corresponding voltage U is output at any frequency f, and the operation adjustment of the frequency converter is reduced;

[0018] The frequency converter operates at the output frequency f, corresponding to the output voltage U, and the permanent magnet motor is in the maximum torque output.

[0019] It is further needed to be explained that the method further comprises:

[0020] S21, in the state of no back drag and speed reduction of the permanent magnet motor driven by the frequency converter, the output frequency f is identified, and the output reactive power Q and the output active power P of the frequency converter are obtained;

[0021] S22, the rated frequency fe and the rated power Pe parameters of the frequency converter are called, the load torque type and the V / F curve are set, the rated electric power Pef allowed by the output frequency f is obtained, and the load rate LR is calculated according to the obtained output side active power P;

[0022] S23, retrieve the rated power Pe of the permanent magnet motor, and calculate the target reactive power Qm from the permanent magnet motor load rate and reactive power curve when the back EMF matches the applied voltage;

[0023] The positive target reactive power is +Qm, and the negative target reactive power is -Qm;

[0024] S24, when the output current phase lags behind the output voltage, set it to inductive, and take the positive reactive power +Q;

[0025] When the output current phase leads the output voltage, set it to capacitive, and take the negative reactive power -Q;

[0026] S25, when the positive reactive power +Q is greater than the positive target reactive power +Qm, the back EMF of the permanent magnet motor is lower than the output voltage of the frequency converter, gradually reduce the output voltage, and make the reactive power +Q tend to the positive target reactive power +Qm;

[0027] When the positive reactive power +Q is less than or equal to the positive target reactive power +Qm, record the frequency f and load rate LR corresponding to the output voltage U- of the frequency converter;

[0028] S26, when the negative reactive power -Q is less than the negative target reactive power -Qm, the back EMF of the permanent magnet motor is higher than the output voltage of the frequency converter, gradually increase the output voltage, and make the negative reactive power -Q tend to the negative target reactive power -Qm;

[0029] When -Q is greater than or equal to -Qm, record the frequency f and load rate LR corresponding to the output voltage U+ of the frequency converter;

[0030] S27, obtain the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR from S25 or S26, calculate the compensation value according to the compensation curve, and then calculate the back EMF corresponding to the operating frequency f EMF=U± value+compensation value;

[0031] If the operating frequency f is below the cutoff frequency, calculate the corresponding back EMF from the EMF / U boost curve below the cutoff frequency;

[0032] Then refresh the frequency f / back EMF / output voltage U curve of the frequency converter, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter;

[0033] The frequency converter operates at the output frequency f and the output voltage U, and the permanent magnet motor is in maximum torque output.

[0034] Further need to be explained is that the method further comprises:

[0035] S31, in the frequency converter driving permanent magnet motor without reverse drag, in the state of speed reduction, identify the output frequency f, and obtain the output reactive current Iq and output active power P of the frequency converter;

[0036] S32, call the rated frequency fe and rated power Pe parameters of the frequency converter, obtain the rated electric power Pef allowed by the output frequency f from the setting load torque type and V / F curve, and calculate the load rate LR according to the obtained active power P;

[0037] S33, call the rated current Ie of the permanent magnet motor, and calculate the target reactive current Iqm from the permanent magnet motor load rate and reactive current curve when the back EMF matches the applied voltage;

[0038] The forward target reactive current is +Iqm, and the negative target reactive current is -Iqm;

[0039] S34, when the output current phase of the frequency converter lags behind the voltage, set it as inductive, and take the forward reactive current +Iq;

[0040] When the output current phase of the frequency converter leads the voltage, set it as capacitive, and take the negative reactive current -Iq;

[0041] S35, when it is detected that the forward reactive current +Iq> The forward target reactive current +Iqm, the back EMF of the permanent magnet motor is lower than the output side voltage of the frequency converter, gradually reduce the output voltage, so that the reactive current +Iq tends to the forward target reactive current +Iqm;

[0042] When +Iq≤+Iqm, record the frequency f and load rate LR corresponding to the output voltage U- of the frequency converter;

[0043] S36, when it is detected that the negative reactive current -Iq

[0044] When -Iq≥-Iqm, record the frequency f and load rate LR corresponding to the output voltage U+ of the frequency converter;

[0045] S37, obtain the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR from S35 step or S36 step, calculate the compensation value according to the compensation curve, and then calculate the back EMF = U± value + compensation value corresponding to the operating frequency f;

[0046] If the operating frequency f is below the cutoff frequency, calculate the corresponding back EMF from the EMF / U improvement curve below the cutoff frequency;

[0047] Then the frequency f of the frequency converter is refreshed, and the output voltage U corresponding to the output at any frequency f is reduced to reduce the operation adjustment of the frequency converter.

[0048] The frequency converter operates at the output frequency f, and the output voltage U corresponding to the output voltage U. The permanent magnet motor is in maximum torque output.

[0049] Further need to explain is, the method further comprises:

[0050] S41, in the state of no reverse drag and speed reduction of the frequency converter driving the permanent magnet motor, the output frequency f is identified, and the reactive power kvarh and the output active power P of the preset time period t are measured;

[0051] S42, the rated frequency fe and the rated power Pe of the frequency converter are called, and the rated electric power Pef allowed by the output frequency f is obtained from the load torque type and the V / F curve. The load rate LR is calculated according to the obtained output active power P;

[0052] S43, the rated power Pe of the permanent magnet motor is called, and the target reactive power varhM is calculated from the reactive voltage and the applied voltage matching the permanent magnet motor load rate and the reactive power curve; The forward target reactive power is + varhM, and the negative target reactive power is - varhM;

[0053] S44, when the output current phase lags behind the output voltage, it is identified as inductive, and the forward reactive power + varh is taken;

[0054] When the output current phase leads the output voltage, it is identified as capacitive, and the negative reactive power - varh is taken;

[0055] S45, when the forward reactive power + varh is greater than the forward target reactive power + varhM, it is indicated that the back EMF of the permanent magnet motor is lower than the output side voltage of the frequency converter, the output voltage is gradually reduced, and the reactive current + varh tends to the forward target reactive power + varhM;

[0056] When + varh≤+ varhM, the frequency f corresponding to the output voltage U- of the frequency converter and the load rate LR are recorded;

[0057] S46, when the negative reactive power - varh is less than the negative target reactive power - varhM, it is indicated that the back EMF of the permanent magnet motor is higher than the output side voltage of the frequency converter, the output voltage is gradually increased, and the negative reactive power - Iq tends to the negative target reactive power varhM;

[0058] When varh≥- varhM, the frequency f corresponding to the output voltage U+ of the frequency converter and the load rate LR are recorded;

[0059] S47, the output voltage value U- or U+, the operating frequency f and the load ratio LR of the target power factor are obtained from S45 or S46, the compensation value is calculated according to the compensation curve, and then the operating frequency f corresponding back EMF = U± value + compensation value is calculated;

[0060] If the operating frequency f is below the cutoff frequency, the corresponding back EMF is calculated from the EMF / U boost curve below the cutoff frequency;

[0061] Then refresh the frequency f / back EMF / output voltage U curve of the frequency converter, and output the corresponding voltage U at any frequency f to reduce the operation adjustment of the frequency converter;

[0062] The frequency converter operates at the output frequency f, and the permanent magnet motor is in the maximum torque output.

[0063] Further need to explain is that the method further comprises:

[0064] S51, in the state of no reverse drag and speed reduction of the frequency converter driving the permanent magnet motor, the output frequency f is identified, and the output active power P, the current and the phase angle Ψ of the voltage of the frequency converter are obtained;

[0065] When the output current phase lags behind the output voltage, it is identified as inductive, and the positive phase angle +Ψ is taken;

[0066] When the output current phase leads the output voltage, it is identified as capacitive, and the negative phase angle -Ψ is taken;

[0067] S52, the rated frequency fe and the rated power Pe parameters of the frequency converter are called, the rated electric power Pef allowed by the output frequency f is obtained from the load torque type and the V / F curve, and the load ratio LR is calculated according to the obtained output active power P;

[0068] S53, the target current / voltage phase angle Ψm when the back EMF and the applied voltage reach matching is obtained from the load ratio and the current / voltage phase angle number curve of the permanent magnet motor;

[0069] The target phase angle of the output current lagging behind the output voltage is +Ψm, and the target phase angle of the output current leading the output voltage is -Ψm;

[0070] S54, when the positive phase angle +Ψ is greater than the positive target phase angle +Ψm, the back EMF of the permanent magnet motor is lower than the output side voltage of the frequency converter, the output voltage is gradually reduced, and the positive phase angle +Ψ tends to the positive target phase angle +Ψm;

[0071] When +Ψ≤+Ψm, the frequency f corresponding to the output voltage U- of the frequency converter and the load ratio LR are recorded;

[0072] S55, when the negative phase angle -Ψ is acquired to be less than the negative target phase angle -Ψm, the back EMF of the permanent magnet motor is higher than the output voltage of the frequency converter, the output voltage is gradually increased, and the negative phase angle -Ψ tends to the negative target phase angle -Ψm;

[0073] When -Ψ≥-Ψm, the frequency f corresponding to the output voltage U+ of the frequency converter and the load rate LR are recorded;

[0074] S56, the output voltage value U- or U+ of the target phase angle, the output frequency f and the load rate LR are acquired, the compensation value is calculated according to the compensation curve, and then the operating frequency f corresponding back EMF EMF=U± value+compensation value is calculated;

[0075] If the operating frequency f is below the cutoff frequency, the corresponding back EMF EMF is calculated from the EMF / U rising curve below the cutoff frequency;

[0076] Then the frequency f / back EMF / output voltage U curve of the frequency converter is refreshed, the corresponding voltage U is output at any frequency f, and the operation adjustment of the frequency converter is reduced.

[0077] Further need to be explained is that the method further comprises:

[0078] S61, in the state of no back drag and speed reduction of the frequency converter driving the permanent magnet motor, the output frequency f is identified, and the output real-time reactive current Iq and output active power P of the frequency converter are acquired;

[0079] S62, the rated frequency fe and rated power Pe parameters of the frequency converter are called, the rated electric power Pef allowed by the output frequency f is acquired from the load torque type and V / F curve, and the load rate LR is calculated according to the acquired output active power P;

[0080] S63, the rated current Ie of the permanent magnet motor is called, and the target reactive current Iqm is calculated from the back EMF and the applied voltage matching, the load rate and the reactive current curve of the permanent magnet motor;

[0081] S64, when the real-time reactive current Iq is greater than the target reactive current Iqm, it is assumed to be a positive reactive current, the back EMF of the permanent magnet motor is lower than the output voltage of the frequency converter, the low output voltage k is fine-tuned, and k is 1-6 volts;

[0082] If the acquired real-time reactive current Iqn is less than the last reactive current Iqn-1, it is assumed to be correct, the low output voltage k is continuously fine-tuned, and the determination is continued every time, when Iq≤Iqm, the output voltage U- of the frequency converter, the corresponding frequency f and the load rate LR are recorded;

[0083] S65, fine-tune low output voltage k, if the new real-time reactive current Iqn is greater than the previous reactive current Iqn-1, it is assumed to be wrong, and the output voltage is adjusted in the opposite direction;

[0084] If the new real-time reactive current Iqn is less than the previous reactive current Iqn-1, continue to adjust the output voltage k, and continue to determine each time, when Iq≤Iqm, record the frequency f and load rate LR of the inverter output voltage U+;

[0085] S66, obtain the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR, calculate the compensation value according to the compensation curve, and then calculate the corresponding back EMF EMF=U± value+compensation value;

[0086] If the operating frequency f is below the cutoff frequency, calculate the corresponding back EMF EMF from the EMF / U boost curve below the cutoff frequency;

[0087] Then refresh the frequency f / back EMF / output voltage U curve of the inverter, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the inverter;

[0088] The inverter operates at an output frequency f and an output voltage U, and the permanent magnet motor is in maximum torque output.

[0089] Further need to explain is that the method further comprises:

[0090] S71, in the state of no back drag and speed reduction of the permanent magnet motor driven by the inverter, identify the output frequency f, and obtain the output power factor PF and output active current I of the inverter;

[0091] S72, call the rated frequency fe and rated current Ie parameters of the inverter, obtain the rated current Ief allowed by the output frequency f from the load torque type and V / F curve, and calculate the load rate LR according to the obtained output active current I;

[0092] S73, obtain the target power factor PFm when the back EMF matches the applied voltage from the permanent magnet motor load rate and power factor curve;

[0093] S74, when the output power factor PF is less than the target power factor PFm, it is assumed to be a positive power factor, and the low output voltage k is fine-tuned, k is 1-6 volts, if the new real-time power factor PFn is greater than the previous power factor PFn-1, it is assumed to be correct, continue to fine-tune the low output voltage k and continue to determine, until the obtained power factor PF≥target power factor PFm, record the current output voltage U-, the corresponding frequency f and the load rate LR;

[0094] In the process of fine-tuning the high output voltage k, if the real-time power factor PFn≤ the last power factor PFn-1 is obtained, the last output voltage U-, the corresponding frequency f and the load rate LR are recorded;

[0095] If the real-time power factor PFn< the last power factor PFn-1 is obtained, an error is assumed, and the high output voltage k is fine-tuned in the opposite direction;

[0096] If the real-time power factor PFn< the last power factor PFn-1 is obtained, an error is assumed, and the high output voltage k is fine-tuned in the opposite direction;

[0097] In the process of fine-tuning the high output voltage k, if the real-time power factor PFn≤ the last power factor PFn-1 is obtained, the last output voltage U-, the corresponding frequency f and the load rate LR are recorded;

[0098] S75, the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR are obtained, the compensation value is calculated according to the compensation curve, and then the counter electromotive force EMF=U± value corresponding to the operating frequency f is calculated;

[0099] If the operating frequency f is below the cutoff frequency, the corresponding counter electromotive force EMF is calculated from the EMF / U boost curve below the cutoff frequency;

[0100] Then the frequency f / counter electromotive force EMF / output voltage U curve of the frequency converter is refreshed, and the corresponding voltage U is output at any frequency f, reducing the operation adjustment of the frequency converter;

[0101] The frequency converter operates at the output frequency f, and the permanent magnet motor is in the maximum torque output.

[0102] Further need to be explained is that the method further comprises:

[0103] S81, in the state of no reverse drag and speed reduction of the frequency converter driving the permanent magnet motor, the output frequency f is identified, and the real-time reactive current Iq of the output side of the frequency converter is obtained;

[0104] S82, the low output voltage k is fine-tuned, k takes 1-6 volts, if the real-time reactive current Iqn< the last reactive current Iqn-1 is obtained, the output voltage k is continuously lowered, the determination is continuously made, until the Iqn≈0 is obtained, and the frequency converter output voltage U and the frequency f are recorded;

[0105] If the real-time reactive current Iqn> the last reactive current Iqn-1 is obtained, the last frequency converter output voltage U and the frequency f are recorded;

[0106] S83, fine-tuning low output voltage k, if the real-time reactive current Iqn is greater than the last reactive current Iqn-1, then the output voltage k is adjusted in the opposite direction;

[0107] If the real-time reactive current Iqn is less than the last reactive current Iqn-1, continue to fine-tune the high output voltage k, and continue to determine, when Iq is approximately 0, record the frequency f and the frequency f of the frequency converter output voltage U;

[0108] If the real-time reactive current Iqn is greater than the last reactive current Iqn-1, record the last frequency f and the frequency f of the frequency converter output voltage U;

[0109] S84, the obtained frequency f is considered as the approximate value of the back EMF of the running frequency f, if the obtained frequency f is lower than the cutoff frequency value, the EMF value is further corrected according to the EMF / U boost curve at the cutoff frequency, and then the back EMF / output voltage U / frequency f curve is refreshed, and the corresponding output voltage U is executed in any frequency f, and the operation adjustment of the frequency converter is reduced;

[0110] S85, the frequency converter runs at the voltage U corresponding to the output frequency f, the permanent magnet motor is in the maximum output torque, the output current is adjusted, the load torque is automatically adapted, and driving control is realized.

[0111] From the above technical solutions, the present application has the following advantages:

[0112] In the high-efficiency energy-saving operation control method of the permanent magnet motor frequency converter provided by the application, the parameter information of the output of the frequency converter is obtained, such as the output voltage value U, the output frequency f and the load rate LR, etc., the back EMF corresponding to the output frequency f is calculated according to the compensation curve, if the output frequency is less than the preset frequency, the EMF is corrected according to the output voltage value U boost curve, then the frequency f / back EMF / output voltage U curve of the frequency converter is refreshed, the corresponding voltage U is output at any frequency f, and the operation adjustment of the frequency converter is reduced.

[0113] In the control method of the application, the frequency converter runs at the output voltage corresponding to the output frequency, the permanent magnet motor is in a high-efficiency energy-saving state, the maximum output torque is output at this time, the output current is further adjusted, the load torque is automatically adapted, and more energy-saving driving control is realized.

[0114] The control method provided by the application can control the permanent magnet motor based on the rated voltage and rated power of the conventional frequency converter, avoiding the problem that the increase of current on the stator winding of the permanent magnet synchronous motor leads to the increase of stator copper loss and iron loss, and the reduction of motor efficiency.

[0115] The control method provided by the application can reduce the energy consumption of the motor, improve the operation efficiency, avoid damage to the permanent magnet synchronous motor, and reduce the failure of the frequency converter and the permanent magnet motor. BRIEF DESCRIPTION OF DRAWINGS

[0116] In order to more clearly illustrate the technical solutions of the present application, the drawings required to be used in the description will be briefly introduced as follows. Obviously, the drawings in the following description are only some embodiments of the present application, and all other drawings obtained by those skilled in the art without creative labor based on these drawings also belong to the protection scope of the present application.

[0117] Figure 1 Load torque type and V / F curve diagram;

[0118] Figure 2 Load rate LR and power factor PF curve diagram;

[0119] Figure 3 Inductive / capacitive phase identification diagram;

[0120] Figure 4 Compensation curve / decay curve diagram, output voltage decay curve diagram when LR>0.75;

[0121] Figure 5 EMF / U promotion curve at cut-off frequency, EMF / U curve diagram between cut-off frequency and rated frequency when LR≤0.75;

[0122] Figure 6 Load rate LR / reactive power Q curve diagram;

[0123] Figure 7 Load rate LR / reactive current Iq curve diagram;

[0124] Figure 8 Load rate LR / UI phase angle curve diagram. DETAILED DESCRIPTION

[0125] The technical solutions in the embodiments of the present application will be described clearly and completely in the following with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only some embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative labor also belong to the protection scope of the present application.

[0126] The units and algorithm steps of each example described in the embodiments disclosed in the high-efficiency energy-saving operation control method of the permanent magnet motor frequency converter can be realized by electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been described in the above description in general terms. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application.

[0127] The high-efficiency energy-saving operation control method of the permanent magnet motor frequency converter provided by the present application should be understood that the disclosed system, device and method can be implemented in other ways. For example, the device embodiments described above are only schematic. For example, the division of the units is only a logical function division, and there can be another division manner in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. In addition, the coupling or direct coupling or communication connection between the units shown or discussed can be indirect coupling or communication connection through some interface, device or unit, and can also be electrical, mechanical or other forms of connection.

[0128] Based on the high-efficiency energy-saving operation control method of the permanent magnet motor frequency converter, the output power factor PF and the output active power P of the frequency converter are combined to realize the high-efficiency energy-saving operation control of the permanent magnet motor frequency converter.

[0129] Specifically, S11, when the frequency converter drives the permanent magnet motor without reverse dragging and speed reduction, the output frequency f is identified, and the output power factor PF and the output active power P of the frequency converter are obtained;

[0130] S12, as shown in Figure 1 , the rated frequency fe and the rated power Pe parameters of the frequency converter are called, the rated electric power Pef allowed by the output frequency f is obtained from the load torque type and the V / F curve, and the load rate LR is calculated according to the obtained output active power P;

[0131] S13, as shown in Figure 1 and Figure 2 , the target power factor PFm is obtained from the permanent magnet motor load rate and power factor curve when the back electromotive force matches the applied voltage; the forward target power factor is +PFm, and the negative target power factor is -PFm;

[0132] S14, the output current phase of the frequency converter lags behind the output voltage, and is set to inductive, taking the forward power factor +PF;

[0133] The output current phase leads the output voltage, and is set to capacitive, taking a negative power factor -PF;

[0134] S15. When it is detected that the forward power factor +PF is less than the forward target power factor +PFm, the back electromotive force of the permanent magnet motor is lower than the output voltage of the inverter, and the output voltage is gradually reduced so that the forward power factor tends to the forward target power factor +PFm;

[0135] When it is detected that the forward power factor +PF ≥ the forward target power factor +PFm, the frequency f and load rate LR corresponding to the inverter output voltage U- are recorded;

[0136] S16, such as Figure 3 and Figure 4 As shown in FIG, when it is detected that the negative power factor -PF> the negative target power factor -PFm, the back electromotive force of the permanent magnet motor is higher than the voltage on the output side of the inverter, and the output voltage is gradually increased to make the negative power factor -PF tend to the negative target power factor -PFm;

[0137] When it is detected that the negative power factor -PF ≤ the negative target power factor -PFm, the frequency f and load rate LR corresponding to the inverter output voltage U+ are recorded;

[0138] S17. Obtain the output voltage value U- or U+ for the target power factor, the operating frequency f, and the load factor LR from step S15 or S16. Based on the compensation curve, first calculate the compensation value and the compensation coefficient △. Set the EMF to 2-8% depending on the type of permanent magnet motor. Then, calculate the back EMF corresponding to the operating frequency f = U± + compensation value.

[0139] If the operating frequency f is below the cutoff frequency, the corresponding back EMF is calculated from the EMF / U boost curve at the cutoff frequency. Then, the inverter frequency f / back EMF / output voltage U curve is refreshed, and the corresponding voltage U is output at any frequency f (when LR>0.75, the output voltage is attenuated according to the curve), reducing the inverter's operational adjustments.

[0140] The inverter operates at the output frequency f corresponding to the output voltage U. The permanent magnet motor is in a high-efficiency and energy-saving state. At this time, it outputs the maximum torque and further adjusts the output current to automatically adapt to the load torque to achieve more energy-saving drive control.

[0141] Based on the high-efficiency and energy-saving operation control method of the permanent magnet motor inverter, the present invention combines the output reactive power Q and output active power P of the inverter to achieve high-efficiency and energy-saving operation control of the permanent magnet motor inverter.

[0142] S21, when the inverter drives the permanent magnet motor in a non-reverse drag and speed reduction state, identifying the output frequency f, and obtaining the output reactive power Q and output active power P of the inverter;

[0143] S22, as shown in Figure 1 The rated frequency fe and the rated power Pe of the frequency converter are called, the load torque type and the V / F curve are set, the rated electric power Pef allowed by the output frequency f is obtained, and the load rate LR is calculated according to the obtained active power P on the output side;

[0144] S23, the rated power Pe of the permanent magnet motor is called, and the load rate and the reactive power curve of the permanent magnet motor are calculated when the back EMF matches the applied voltage, and the target reactive power Qm is calculated;

[0145] The forward target reactive power is +Qm, and the negative target reactive power is -Qm;

[0146] S24, when the output current phase lags behind the output voltage, it is set to inductive, and the forward reactive power +Q is taken;

[0147] When the output current phase leads the output voltage, it is set to capacitive, and the negative reactive power -Q is taken;

[0148] S25, as shown in Figure 2 and Figure 5 When the forward reactive power +Q is greater than the forward target reactive power +Qm, the back EMF of the permanent magnet motor is lower than the output voltage of the frequency converter, the output voltage is gradually reduced, and the reactive power +Q tends to the forward target reactive power +Qm;

[0149] When the forward reactive power +Q is less than or equal to the forward target reactive power +Qm, the frequency f and the load rate LR corresponding to the output voltage U- of the frequency converter are recorded;

[0150] S26, as shown in Figure 3 and Figure 4 When the negative reactive power -Q is less than the negative target reactive power -Qm, the back EMF of the permanent magnet motor is higher than the output voltage of the frequency converter, the output voltage is gradually increased, and the negative reactive power -Q tends to the negative target reactive power -Qm;

[0151] When -Q is greater than or equal to -Qm, the frequency f and the load rate LR corresponding to the output voltage U+ of the frequency converter are recorded;

[0152] S27, the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR obtained by S25 step or S26 step are obtained, the compensation value is calculated according to the compensation curve, and then the back EMF=U± value corresponding to the operating frequency f is calculated.

[0153] If the operating frequency f is below the cutoff frequency, the corresponding back EMF is calculated from the EMF / U boost curve below the cutoff frequency,

[0154] Then the frequency f of the frequency converter, the back EMF and the output voltage U curve are refreshed, and the corresponding voltage U is output at any frequency f (the output voltage is attenuated according to the curve when LR>0.75), and the operation adjustment of the frequency converter is reduced.

[0155] The frequency converter operates at the output frequency f, and the corresponding output voltage U, and the permanent magnet motor is in the maximum torque output.

[0156] Based on the high-efficiency energy-saving operation control method of the permanent magnet motor frequency converter, the output reactive current Iq and the output active power P of the frequency converter are combined to realize the high-efficiency energy-saving operation control of the permanent magnet motor frequency converter.

[0157] S31, in the state that the frequency converter drives the permanent magnet motor without reverse dragging and speed reduction, the output frequency f is identified, and the output reactive current Iq and the output active power P of the frequency converter are obtained;

[0158] S32, as shown in Figure 1 , the rated frequency fe and the rated power Pe parameters of the frequency converter are called, the rated electric power Pef allowed by the output frequency f is obtained from the setting load torque type and the V / F curve, and the load rate LR is calculated according to the obtained active power P;

[0159] S33, as shown in Figure 2 and 6 , the rated current Ie of the permanent magnet motor is called, and the target reactive current Iqm is calculated from the permanent magnet motor load rate and the reactive current curve when the back EMF matches the applied voltage;

[0160] The forward target reactive current is +Iqm, and the negative target reactive current is -Iqm;

[0161] S34, when the output current phase of the frequency converter lags behind the voltage, it is set to inductive, and the forward reactive current +Iq is taken;

[0162] When the output current phase of the frequency converter leads the voltage, it is set to capacitive, and the negative reactive current -Iq is taken;

[0163] S35, when it is detected that the forward reactive current +Iq> The forward target reactive current +Iqm, the back EMF of the permanent magnet motor is lower than the output side voltage of the frequency converter, the output voltage is gradually reduced, and the reactive current +Iq tends to the forward target reactive current +Iqm;

[0164] When +Iq≤+Iqm, the frequency f and the load rate LR corresponding to the output voltage U- of the frequency converter are recorded;

[0165] S36, as shown in Figure 4 and Figure 5As shown, when the negative reactive current -Iq is detected, the back EMF of the permanent magnet motor is higher than the output voltage of the frequency converter, the output voltage is gradually increased, and the negative reactive current -Iq tends to the negative target reactive current -Iqm;

[0166] When -Iq≥-Iqm, the frequency f corresponding to the frequency converter output voltage U+ and the load rate LR are recorded;

[0167] S37, the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR obtained by S35 step or S36 step are run, the compensation value is calculated according to the compensation curve, and then the operating frequency f corresponding back EMF=U± value+compensation value is calculated.

[0168] If the operating frequency f is below the cutoff frequency, the corresponding back EMF is calculated from the EMF / U rising curve below the cutoff frequency,

[0169] Then refresh the frequency converter frequency f / back EMF / output voltage U curve, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter;

[0170] The frequency converter runs at the output frequency f, and the corresponding output voltage U, and the permanent magnet motor is in the maximum torque output.

[0171] The method provided by the application further comprises: Figure 3 and Figure 6 As shown, S41, in the state of no reverse drag and speed reduction of the frequency converter driving the permanent magnet motor, the output frequency f is identified, and the reactive power kvarh and the output active power P in a preset time period t are measured;

[0172] S42, as shown, Figure 1 The rated frequency fe and the rated power Pe of the frequency converter are called, the rated electric power Pef allowed by the output frequency f is obtained from the load torque type and the V / F curve, and the load rate LR is calculated according to the obtained output active power P;

[0173] S43, the rated power Pe of the permanent magnet motor is called, the target reactive power varhM is calculated from the back EMF and the applied voltage matching, the permanent magnet motor load rate and the reactive power curve, the positive target reactive power is +varhM, and the negative target reactive power is -varhM;

[0174] S44, when the output current phase of the frequency converter lags behind the output voltage, it is identified as inductive, and the positive reactive power +varh is taken;

[0175] When the output current phase leads the output voltage, it is identified as capacitive, and the negative reactive power -varh is taken;

[0176] S45, when the positive reactive power +varh is greater than the positive target reactive power +varhM, it indicates that the back electromotive force of the permanent magnet motor is lower than the output voltage of the frequency converter, gradually reduce the output voltage, and make the positive reactive current +varh tend to the positive target reactive power +varhM;

[0177] When +varh is less than or equal to +varhM, record the frequency f corresponding to the output voltage U- of the frequency converter and the load rate LR;

[0178] S46, when the negative reactive power -varh is less than the negative target reactive power -varhM, it indicates that the back electromotive force of the permanent magnet motor is higher than the output voltage of the frequency converter, gradually increase the output voltage, and make the negative reactive power -varh tend to the negative target reactive power -varhM;

[0179] When varh is greater than or equal to -varhM, record the output voltage U+ of the frequency converter, the corresponding frequency f and the load rate LR;

[0180] S47, obtain the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR from S45 or S46, calculate the compensation value according to the compensation curve, and then calculate the corresponding back electromotive force EMF=U± value+compensation value.

[0181] If the operating frequency f is below the cutoff frequency, calculate the corresponding back electromotive force EMF from the EMF / U boost curve below the cutoff frequency,

[0182] Then refresh the frequency converter frequency f / back electromotive force EMF / output voltage U curve, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter;

[0183] The frequency converter operates at the output frequency f, corresponding to the output voltage U, and the permanent magnet motor is in the maximum torque output.

[0184] Based on the high-efficiency energy-saving operation control method of the permanent magnet motor frequency converter, the output active power P, current and voltage phase angle Ψ of the frequency converter are combined to realize the high-efficiency energy-saving operation control of the permanent magnet motor frequency converter.

[0185] Specifically, as shown in Figure 3 and 8 S51, in the state of no back drag and speed reduction of the permanent magnet motor driven by the frequency converter, the output frequency f is identified, and the output active power P, current and voltage phase angle Ψ of the frequency converter are obtained;

[0186] When the output current phase lags behind the output voltage, it is identified as inductive, and the positive phase angle +Ψ is taken;

[0187] When the output current phase leads the output voltage, it is identified as capacitive, and the negative phase angle -Ψ is taken;

[0188] S52, call the rated frequency fe and rated power Pe parameters of the frequency converter, obtain the rated electric power Pef of the output frequency f from the load torque type and V / F curve, and calculate the load rate LR according to the obtained output active power P;

[0189] S53, obtain the target current / voltage phase angle Ψm from the permanent magnet motor load rate and current / voltage phase angle curve when the back electromotive force and the applied voltage reach matching;

[0190] The target phase angle of the output current lagging behind the output voltage is +Ψm, and the target phase angle of the output current leading the output voltage is -Ψm;

[0191] S54, when the forward phase angle +Ψ is greater than the forward target phase angle +Ψm, the back electromotive force of the permanent magnet motor is lower than the output side voltage of the frequency converter, the output voltage is gradually reduced, and the forward phase angle +Ψ tends to the forward target phase angle +Ψm;

[0192] When +Ψ≤+Ψm, record the frequency f and the load rate LR corresponding to the output voltage U- of the frequency converter;

[0193] S55, when the negative phase angle -Ψ is less than the negative target phase angle -Ψm, the back electromotive force of the permanent magnet motor is higher than the output side voltage of the frequency converter, the output voltage is gradually increased, and the negative phase angle -Ψ tends to the negative target phase angle -Ψm;

[0194] When -Ψ≥-Ψm, record the frequency f and the load rate LR corresponding to the output voltage U+ of the frequency converter;

[0195] S56, obtain the output voltage value U- or U+ of the target phase angle, the output frequency f and the load rate LR, calculate the compensation value according to the compensation curve, and then calculate the corresponding back electromotive force EMF of the running frequency f.

[0196] If the running frequency f is below the cutoff frequency, calculate the corresponding back electromotive force EMF from the EMF / U boost curve below the cutoff frequency,

[0197] Then refresh the frequency converter frequency f / back electromotive force EMF / output voltage U curve, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter;

[0198] The method provided by the application further comprises: S61, identifying the output frequency f when the frequency converter drives the permanent magnet motor in the no-reverse drag and speed reduction state, and obtaining the output real-time reactive current Iq and output active power P of the frequency converter;

[0199] S62, call the rated frequency fe and rated power Pe parameters of the frequency converter, get the rated power Pef of the output frequency f from the load torque type and V / F curve, and calculate the load rate LR according to the obtained output active power P;

[0200] S63, call the rated current Ie of the permanent magnet motor, and calculate the target reactive current Iqm from the permanent magnet motor load rate and reactive current curve when the back EMF matches the applied voltage;

[0201] S64, when the real-time reactive current Iq is greater than the target reactive current Iqm, it is assumed to be a positive reactive current, then the back EMF of the permanent magnet motor is lower than the output voltage of the frequency converter, and the low output voltage k is fine-tuned, k is 1-6 volts;

[0202] If the obtained real-time reactive current Iqn is less than the last reactive current Iqn-1, it is assumed to be correct, and the low output voltage k is continuously fine-tuned, and the determination is continued every time, when Iq≤Iqm, the output voltage U- of the frequency converter, the corresponding frequency f and the load rate LR are recorded;

[0203] S65, fine-tune the low output voltage k, if the new real-time reactive current Iqn is greater than the last reactive current Iqn-1, it is assumed to be incorrect, and the output voltage is adjusted in the opposite direction;

[0204] If the new real-time reactive current Iqn is less than the last reactive current Iqn-1, continue to adjust the output voltage k, continue to determine every time, when Iq≤Iqm, record the output voltage U+ of the frequency converter, the frequency f and the load rate LR;

[0205] For this method, the output voltage value U- or U+, the output frequency f and the load rate LR of the minimum reactive current are obtained, the compensation value and the compensation coefficient △ are calculated according to the compensation curve, and the back EMF is calculated according to the type of permanent magnet motor, which is 2-8% EMF. Then calculate the running frequency f corresponding to the back EMF EMF=U± value+compensation value.

[0206] If the running frequency f is below the cutoff frequency, calculate the corresponding back EMF EMF from the EMF / U boost curve below the cutoff frequency, and then refresh the frequency converter frequency f / back EMF / output voltage U curve, output the corresponding voltage U at any frequency f (when LR>0.75, output voltage according to the curve attenuation), reduce the operation adjustment of the frequency converter.

[0207] The frequency converter runs at the output frequency f, corresponding to the output voltage U, and the permanent magnet motor is in a high-efficiency energy-saving state, at this time the maximum torque is output, the output current is further adjusted, the load torque is automatically adapted, and more energy-saving drive control is realized.

[0208] For the method, the frequency converter has no inductive / capacitive recognition, the load rate is determined by the current, but the output reactive power, reactive power, power factor, voltage and current phase angle can be obtained, and the energy-saving effect is the same by using the above-mentioned idea and the attempt tracking control, so that the frequency converter can be efficiently and safely operated.

[0209] The method further comprises: S71, identifying the output frequency f and obtaining the output power factor PF and the output active current I of the frequency converter when the frequency converter drives the permanent magnet motor in the non-reverse dragging and speed reduction state;

[0210] S72, as shown in Figure 1 and 2 , the rated frequency fe and the rated current Ie parameters of the frequency converter are called, the rated current Ief allowed by the output frequency f is obtained from the load torque type and the V / F curve, and the load rate LR is calculated according to the obtained output active current I;

[0211] S73, the target power factor PFm is obtained from the permanent magnet motor load rate and power factor curve when the back electromotive force matches the applied voltage;

[0212] S74, when the output power factor PF is less than the target power factor PFm, it is assumed to be a positive power factor, the low output voltage k is fine-tuned, k is 1-6 volts, if the new real-time power factor PFn is greater than the last power factor PFn-1, it is assumed to be correct, the low output voltage k is continuously fine-tuned and continuously judged, until the obtained power factor PF is greater than or equal to the target power factor PFm, the current output voltage U-, the corresponding frequency f and the load rate LR are recorded;

[0213] In the process of fine-tuning the high output voltage k, if the real-time power factor PFn is less than or equal to the last power factor PFn-1, the last output voltage U-, the corresponding frequency f and the load rate LR are recorded;

[0214] If the real-time power factor PFn is less than the last power factor PFn-1, it is assumed to be incorrect, and the high output voltage k is fine-tuned in the opposite direction;

[0215] If the real-time power factor PFq is greater than the last power factor PFq-1, the high output voltage is continuously fine-tuned, and each time the power factor PF is greater than or equal to the target power factor PFm, the current output voltage U+, the corresponding frequency f and the load rate LR are recorded;

[0216] In the process of fine-tuning the high output voltage k, if the real-time power factor PFn is less than or equal to the last power factor PFn-1, the last output voltage U+, the corresponding frequency f and the load rate LR are recorded;

[0217] S75, as shown in Figure 4 andFigure 5 As shown, the output voltage value U- or U+ of the above-mentioned target power factor acquisition, output frequency f and load rate LR are used to calculate the compensation value according to the compensation curve, and then the operating frequency f corresponding back electromotive force EMF = U± value + compensation value is calculated.

[0218] If the operating frequency f is below the cutoff frequency, the corresponding back electromotive force EMF is calculated from the EMF / U boost curve below the cutoff frequency, and then the frequency f / back electromotive force EMF / output voltage U curve is refreshed, and the corresponding voltage U is output at any frequency f.

[0219] The inductance and inductance recognition related to the present application uses current to determine the load rate, and the frequency converter can obtain the output side reactive current, reactive power, reactive power, voltage and current phase angle, according to the above idea, using trial tracking control, the energy saving effect is completely the same, and the frequency converter can be used efficiently, safely and economically.

[0220] As another method of the present application, S81, when the frequency converter drives the permanent magnet motor without reverse drag and speed reduction, the output frequency f is identified, and the real-time reactive current Iq of the output side of the frequency converter is obtained;

[0221] S82, fine-tune the low output voltage k, k takes 1-6 volts, if the real-time reactive current Iqn is less than the last reactive current Iqn-1, continue to lower the output voltage k, continue to determine, until the Iqn≈0 is obtained, record the frequency converter output voltage U and frequency f;

[0222] If the real-time reactive current Iqn is greater than the last reactive current Iqn-1, record the last frequency converter output voltage U and frequency f;

[0223] S83, fine-tune the low output voltage k, if the real-time reactive current Iqn is greater than the last reactive current Iqn-1, then adjust the output voltage k in the opposite direction;

[0224] If the real-time reactive current Iqn is less than the last reactive current Iqn-1, continue to fine-tune the high output voltage k, continue to determine, when Iq≈0, record the frequency converter output voltage U and frequency f;

[0225] If the real-time reactive current Iqn is greater than the last reactive current Iqn-1, record the last frequency converter output voltage U and frequency f;

[0226] S85, the obtained frequency converter output voltage U is regarded as the approximate value of the back electromotive force of the operating frequency f, if the obtained frequency f is lower than the cutoff frequency value, the EMF value is further corrected according to the EMF / U boost curve below the cutoff frequency, and then the back electromotive force EMF, output voltage U and frequency f curve is refreshed, and the corresponding output voltage U is executed at any frequency f, reducing the operation adjustment of the frequency converter;

[0227] S86, the frequency converter operates at the voltage U corresponding to the output frequency f, the permanent magnet motor is at the maximum output torque, the output current is adjusted, the load torque is automatically adapted, and the driving control is realized.

[0228] The non-capacitive / inductive identification involved in steps S81 to S86 of the application is based on non-load rate determination, and ordinary frequency converters can obtain the output side reactive power, reactive power, power factor, voltage and current phase angle, according to the above idea, self-learning attempt tracking control is adopted, and the energy-saving effect is completely the same, and the frequency converter can be efficiently and safely operated.

[0229] The permanent magnet motor frequency converter efficient energy-saving operation control method provided by the application is described in combination with the units and algorithm steps of each example of the embodiments disclosed in the present application, and can be realized by electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description. Whether the functions are executed in hardware or software depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the application.

[0230] Those skilled in the art can understand that each aspect of the permanent magnet motor frequency converter efficient energy-saving operation control method provided by the application can be realized as a system, method or program product. Therefore, each aspect of the present disclosure can be specifically implemented as follows: a complete hardware implementation, a complete software implementation (including firmware, microcode, etc.), or a combination of hardware and software aspects, which can be collectively referred to as "circuit", "module" or "system" here.

[0231] The above description of the disclosed embodiments enables those skilled in the art to implement or use the application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the application. Therefore, the application will not be limited to these embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A control method for high efficiency and energy saving operation of a permanent magnet motor inverter, characterized in that the method Comprise: S11, in the state of no reverse drag and speed reduction of the frequency converter driving permanent magnet motor, identify the output frequency f, and obtain the output power factor PF and output active power P of the frequency converter; S12, call the rated frequency fe and rated power Pe parameters of the frequency converter, obtain the rated electric power Pef allowed by the output frequency f from the load torque type and V / F curve, and calculate the load rate LR according to the obtained output active power P; S13, obtain the target power factor PFm when the back electromotive force matches the applied voltage from the load rate and power factor curve of the permanent magnet motor; The forward target power factor is +PFm, and the negative target power factor is -PFm; S14, the output current phase lags behind the output voltage of the frequency converter, which is set to inductive and takes the forward power factor +PF; The output current phase leads the output voltage, which is set to capacitive and takes the negative power factor -PF; S15, when it is detected that the forward power factor +PF < the forward target power factor +PFm, the back electromotive force of the permanent magnet motor is lower than the output voltage of the frequency converter, the output voltage is gradually reduced, so that the forward power factor tends to the forward target power factor +PFm; When it is detected that the forward power factor +PF ≥ the forward target power factor +PFm, record the frequency f and the load rate LR corresponding to the output voltage U- of the frequency converter; S16, when it is detected that the negative power factor -PF > the negative target power factor -PFm, the back electromotive force of the permanent magnet motor is higher than the output voltage of the frequency converter, the output voltage is gradually increased, so that the negative power factor -PF tends to the negative target power factor -PFm; When it is detected that the negative power factor -PF ≤ the negative target power factor -PFm, record the frequency f and the load rate LR corresponding to the output voltage U+ of the frequency converter; S17, obtain the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR obtained from step S15 or step S16, calculate the compensation value according to the compensation curve, and then calculate the back electromotive force EMF=U± value+compensation value corresponding to the operating frequency f; If the operating frequency f is below the cutoff frequency, correct the corresponding back electromotive force EMF from the EMF / U improvement curve below the cutoff frequency; If the operating frequency f is greater than or equal to the cutoff frequency, the EMF calculation value is not corrected; Then refresh the frequency f / back electromotive force EMF / output voltage U curve of the frequency converter, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter; The frequency converter runs at the output frequency f and the output voltage U, and the permanent magnet motor is in the maximum torque output.

2. The control method of claim 1, wherein, The method further comprises: S21, in the state of no reverse drag and speed reduction of the frequency converter driving permanent magnet motor, identify the output frequency f, and obtain the output reactive power Q and output active power P of the frequency converter; S22, call the rated frequency fe and rated power Pe parameters of the frequency converter, set the load torque type and V / F curve, obtain the rated electric power Pef allowed by the output frequency f, and calculate the load rate LR according to the obtained output active power P; S23, call the rated power Pe of the permanent magnet motor, and calculate the target reactive power Qm from the permanent magnet motor load rate and reactive power curve when the back EMF matches the applied voltage; The positive target reactive power is +Qm, and the negative target reactive power is -Qm; S24, when the frequency converter output current phase lags behind the output voltage, it is set to inductive, and the positive reactive power +Q is taken; When the output current phase leads the output voltage, it is set to capacitive, and the negative reactive power -Q is taken; S25, when the positive reactive power +Q is greater than the positive target reactive power +Qm, the back EMF of the permanent magnet motor is lower than the frequency converter output voltage, and the output voltage is gradually reduced to make the reactive power +Q tend to the positive target reactive power +Qm; When the positive reactive power +Q is less than or equal to the positive target reactive power +Qm, the frequency f corresponding to the frequency converter output voltage U- and the load rate LR are recorded; S26, when the negative reactive power -Q is less than the negative target reactive power -Qm, the back EMF of the permanent magnet motor is higher than the frequency converter output voltage, and the output voltage is gradually increased to make the negative reactive power -Q tend to the negative target reactive power -Qm; When -Q is greater than or equal to -Qm, the frequency f corresponding to the frequency converter output voltage U+ and the load rate LR are recorded; S27, the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR obtained from S25 or S26 are used to calculate the compensation value according to the compensation curve, and then the back EMF corresponding to the operating frequency f is calculated as EMF=U± value+compensation value; If the operating frequency f is below the cutoff frequency, the corresponding back EMF is corrected from the EMF / U improvement curve below the cutoff frequency; if the operating frequency f is greater than or equal to the cutoff frequency, the EMF calculation value is not corrected; Then refresh the frequency converter frequency f / back EMF / output voltage U curve, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter; The frequency converter operates at the output frequency f and the corresponding output voltage U, and the permanent magnet motor is in maximum torque output.

3. The control method of claim 1, wherein, The method further comprises: S31, in the state of no reverse drag and speed reduction of the permanent magnet motor driven by the frequency converter, the output frequency f is identified, and the output reactive current Iq and the output active power P of the frequency converter are obtained; S32, the rated frequency fe and the rated power Pe parameters of the frequency converter are called, and the rated electric power Pef allowed for the output frequency f is obtained from the set load torque type and V / F curve, and the load rate LR is calculated according to the obtained active power P; S33, call the rated current Ie of the permanent magnet motor, and calculate the target reactive current Iqm from the permanent magnet motor load rate and reactive current curve when the back EMF matches the applied voltage; The positive target reactive current is +Iqm, and the negative target reactive current is -Iqm; S34, when the frequency converter output current phase lags behind the voltage, it is set to inductive, and the positive reactive current +Iq is taken; When the frequency converter output current phase leads the voltage, it is set to capacitive, and the negative reactive current -Iq is taken; S35, when detecting that the forward reactive current +Iq > the forward target reactive current +Iqm, the back electromotive force of the permanent magnet motor is lower than the output side voltage of the frequency converter, gradually reduce the output voltage, and make the reactive current +Iq tend to the forward target reactive current +Iqm; When +Iq≤+Iqm, record the frequency f and the load rate LR corresponding to the output voltage U- of the frequency converter; S36, when detecting that the negative reactive current -Iq < the negative target reactive current -Iqm, the back electromotive force of the permanent magnet motor is higher than the output side voltage of the frequency converter, gradually increase the output voltage, and make the negative reactive current -Iq tend to the negative target reactive current -Iqm; When -Iq≥-Iqm, record the frequency f and the load rate LR corresponding to the output voltage U+ of the frequency converter; S37, obtain the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR from the S35 step or the S36 step, calculate the compensation value according to the compensation curve first, and then calculate the corresponding back electromotive force EMF=U± value of the operating frequency f + the compensation value; If the operating frequency f is below the cutoff frequency, correct the corresponding back electromotive force EMF from the EMF / U improvement curve below the cutoff frequency; if the operating frequency f is greater than or equal to the cutoff frequency, the EMF calculation value is not corrected; then refresh the frequency f / back electromotive force EMF / output voltage U curve of the frequency converter, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter; The frequency converter operates at the output frequency f and the corresponding output voltage U, and the permanent magnet motor is in the maximum torque output.

4. The control method of claim 1, wherein, The method further comprises: S41, in the state of no reverse drag and speed reduction of the permanent magnet motor driven by the frequency converter, identify the output frequency f, and measure the reactive power kvarh and the output active power P in a preset time period t; S42, call the rated frequency fe and the rated power Pe parameters of the frequency converter, obtain the rated electric power Pef allowed by the output frequency f from the load torque type and the V / F curve, and calculate the load rate LR according to the obtained output active power P; S43, call the rated power Pe of the permanent magnet motor, calculate the target reactive power varhM from the permanent magnet motor load rate and the reactive power curve when the back electromotive force matches the applied voltage; the forward target reactive power is +varhM, and the negative target reactive power is -varhM; S44, when the phase of the output current lags behind the output voltage, identify as inductive, and take the forward reactive power +varh; When the phase of the output current leads the output voltage, identify as capacitive, and take the negative reactive power -varh; S45, when the forward reactive power +varh > the forward target reactive power +varhM is obtained, it is indicated that the back electromotive force of the permanent magnet motor is lower than the output side voltage of the frequency converter, the output voltage is gradually reduced, and the reactive current power +varh tends to the forward target reactive power +varhM; When +varh≤+varhM, record the frequency f and the load rate LR corresponding to the output voltage U- of the frequency converter; S46, when the negative reactive power varh is less than the negative target reactive power varhM, it indicates that the back EMF of the permanent magnet motor is higher than the output voltage of the frequency converter, gradually increase the output voltage, and make the negative reactive power Iq tend to the negative target reactive power varhM; When varh≥-varhM, record the output voltage U+ of the frequency converter, the corresponding frequency f and the load rate LR; S47, obtain the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR from S45 or S46, calculate the compensation value according to the compensation curve first, and then calculate the corresponding back EMF EMF=U± value+compensation value of the operating frequency f; If the operating frequency f is below the cutoff frequency, correct the corresponding back EMF EMF from the EMF / U rising curve below the cutoff frequency; if the operating frequency f is greater than or equal to the cutoff frequency, the EMF calculation value is not corrected; then refresh the frequency converter frequency f / back EMF / output voltage U curve, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter; The frequency converter operates at the output frequency f and the corresponding output voltage U, and the permanent magnet motor is in the maximum torque output.

5. The control method of claim 1, wherein, The method further comprises: S51, in the state of no back drag and speed reduction of the permanent magnet motor driven by the frequency converter, identify the output frequency f, and obtain the output active power P, the current and the phase angle Ψ of the voltage of the frequency converter; When the output current phase lags behind the output voltage, it is identified as inductive, and the positive phase angle +Ψ is taken; When the output current phase leads the output voltage, it is identified as capacitive, and the negative phase angle -Ψ is taken; S52, call the rated frequency fe and the rated power Pe parameters of the frequency converter, obtain the rated electric power Pef allowed by the output frequency f from the load torque type and the V / F curve, and calculate the load rate LR according to the obtained output active power P; S53, obtain the target current / voltage phase angle Ψm when the back EMF and the applied voltage reach matching from the permanent magnet motor load rate and the current / voltage phase angle curve; The target phase angle of the output current lagging behind the output voltage is +Ψm, and the target phase angle of the output current leading the output voltage is -Ψm; S54, when the positive phase angle +Ψ is greater than the positive target phase angle +Ψm, the back EMF of the permanent magnet motor is lower than the output voltage of the frequency converter, gradually reduce the output voltage, and make the positive phase angle +Ψ tend to the positive target phase angle +Ψm; When +Ψ≤+Ψm, record the output voltage U- of the frequency converter, the corresponding frequency f and the load rate LR; S55, when the negative phase angle -Ψ is less than the negative target phase angle -Ψm, the back EMF of the permanent magnet motor is higher than the output voltage of the frequency converter, gradually increase the output voltage, and make the negative phase angle -Ψ tend to the negative target phase angle -Ψm; When -Ψ≥-Ψm, record the output voltage U+ of the frequency converter, the corresponding frequency f and the load rate LR; S56, obtain the output voltage value U- or U+ of the target phase angle, the output frequency f and the load rate LR, calculate the compensation value according to the compensation curve first, and then calculate the corresponding back EMF EMF=U± value+compensation value of the operating frequency f; If the operating frequency f is below the cutoff frequency, the corresponding counter EMF is corrected from the EMF / U rising curve below the cutoff frequency; if the operating frequency f is greater than or equal to the cutoff frequency, the EMF calculation value is not corrected; then the frequency f / counter EMF / output voltage U curve of the frequency converter is refreshed, and the corresponding voltage U is output at any frequency f, reducing the operation adjustment of the frequency converter.

6. The control method of claim 1, wherein, The method further comprises: S61, in the state of no counter dragging and speed reduction of the permanent magnet motor driven by the frequency converter, the output frequency f is identified, and the output real-time reactive current Iq and output active power P of the frequency converter are obtained; S62, the rated frequency fe and rated power Pe parameters of the frequency converter are called, the rated electric power Pef allowed by the output frequency f is obtained from the load torque type and V / F curve, and the load rate LR is calculated according to the obtained output active power P; S63, the rated current Ie of the permanent magnet motor is called, and the target reactive current Iqm is calculated from the permanent magnet motor load rate and reactive current curve when the counter EMF and the applied voltage are matched; S64, when the real-time reactive current Iq>Iqm, it is assumed to be a positive reactive current, the counter EMF of the permanent magnet motor is lower than the output voltage of the frequency converter, the low output voltage k is fine-tuned, and k is 1-6 volts; If the obtained real-time reactive current IqnIqn-1, it is assumed to be correct, the low output voltage k is continuously fine-tuned, and the determination is continued every time, when IqIqm, the output voltage U- of the frequency converter, the corresponding frequency f and the load rate LR are recorded; S65, the low output voltage k is fine-tuned, if the new real-time reactive current IqnIqn-1, it is assumed to be wrong, and the output voltage is adjusted in the opposite direction; If the new real-time reactive current IqnIqn-1, the output voltage k is continuously adjusted, and the determination is continued every time, when IqIqm, the output voltage U+ of the frequency converter, the frequency f and the load rate LR are recorded; S66, the output voltage value U- or U+ of the target power factor, the operating frequency f and the load rate LR are obtained, the compensation value is calculated according to the compensation curve, and then the counter EMF corresponding to the operating frequency f is calculated as EMF=U± value+compensation value; If the operating frequency f is below the cutoff frequency, the corresponding counter EMF is corrected from the EMF / U rising curve below the cutoff frequency; if the operating frequency f is greater than or equal to the cutoff frequency, the EMF calculation value is not corrected; then the frequency f / counter EMF / output voltage U curve of the frequency converter is refreshed, and the corresponding voltage U is output at any frequency f, reducing the operation adjustment of the frequency converter. The frequency converter runs at the output frequency f, corresponding to the output voltage U, and the permanent magnet motor is in the maximum torque output.

7. The control method of claim 1, wherein, The method further comprises: S71, in the state of no counter dragging and speed reduction of the permanent magnet motor driven by the frequency converter, the output frequency f is identified, and the output power factor PF and output active current I of the frequency converter are obtained; S72, the rated frequency fe and rated current Ie parameters of the frequency converter are called, the rated current Ief allowed by the output frequency f is obtained from the load torque type and V / F curve, and the load rate LR is calculated according to the obtained output active current I; S73, from the permanent magnet motor load rate and power factor curve, obtain the target power factor PFm when the back electromotive force matches the applied voltage; S74, when the output power factor PF is less than the target power factor PFm, assume positive power factor, fine-tune the low output voltage k, k takes 1-6 volts, if the new real-time power factor PFn obtained is greater than the last power factor PFn-1, it is assumed to be correct, continue to fine-tune the low output voltage k and continue to judge, until the obtained power factor PF is greater than or equal to the target power factor PFm, record the current output voltage U-, corresponding frequency f and load rate LR; In the process of fine-tuning the high output voltage k, if the real-time power factor PFn obtained is less than or equal to the last power factor PFn-1, record the last output voltage U-, corresponding frequency f and load rate LR; If the real-time power factor PFn obtained is less than the last power factor PFn-1, it is assumed to be incorrect, and the high output voltage k is fine-tuned in the opposite direction; If the real-time power factor PFq obtained is greater than the last power factor PFq-1, continue to fine-tune the high output voltage, and judge each time until the obtained power factor PF is greater than or equal to the target power factor PFm, record the current output voltage U+, corresponding frequency f and load rate LR; In the process of fine-tuning the high output voltage k, if the real-time power factor PFn obtained is less than or equal to the last power factor PFn-1, record the last output voltage U+, corresponding frequency f and load rate LR; S75, obtain the output voltage value U- or U+ of the target power factor, the running frequency f and the load rate LR, calculate the compensation value according to the compensation curve, and then calculate the corresponding back electromotive force EMF=U± value+compensation value; If the running frequency f is below the cutoff frequency, correct the corresponding back electromotive force EMF from the EMF / U improvement curve below the cutoff frequency; if the running frequency f is greater than or equal to the cutoff frequency, the EMF calculation value is not corrected; Then refresh the frequency converter frequency f / back electromotive force EMF / output voltage U curve, output the corresponding voltage U at any frequency f, and reduce the operation adjustment of the frequency converter; The frequency converter runs at the output frequency f, corresponding to the output voltage U, and the permanent magnet motor is in maximum torque output.

8. The control method of claim 1, wherein, The method further comprises: S81, in the state of no back dragging and speed reduction of the frequency converter driving the permanent magnet motor, identify the output frequency f, and obtain the real-time reactive current Iq on the output side of the frequency converter; S82 fine-tune the low output voltage k, k takes 1-6 volts, if the real-time reactive current Iqn obtained is less than the last reactive current Iqn-1, continue to lower the output voltage k, and continue to judge, until Iqn≈0 is obtained, record the frequency converter output voltage U and frequency f; If the real-time reactive current Iqn obtained is greater than the last reactive current Iqn-1, record the last frequency converter output voltage U and frequency f; S83, fine-tune the low output voltage k, if the real-time reactive current Iqn obtained is greater than the last reactive current Iqn-1, fine-tune the high output voltage k in the opposite direction; If the real-time reactive current Iqn obtained is less than the last reactive current Iqn-1, continue to fine-tune the high output voltage k, and continue to judge, when Iq≈0, record the frequency converter output voltage U and frequency f; If the real-time reactive current Iqn is greater than the previous reactive current Iqn-1, record the previous frequency converter output voltage U and frequency f; S84, the obtained frequency converter output voltage U is regarded as the counter EMF approximation of the operating frequency f, if the obtained frequency f is lower than the cutoff frequency value, further correct the EMF value according to the EMF / U rising curve under the cutoff frequency, then refresh the counter EMF, output voltage U and frequency f curve, at any frequency f, execute the corresponding output voltage U, reduce the operation adjustment of the frequency converter; S85, the frequency converter operates at the voltage U corresponding to the output frequency f, the permanent magnet motor is in the output maximum torque, the output current is adjusted, the load torque is automatically adapted, and the driving control is realized.

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