A method and system for controlling the voltage stability of a frequency converter bus

Abstract

The present invention provides a method and system for controlling bus voltage stability of a frequency converter, belonging to the technical field of power electronics and electric drive, comprising: obtaining a DC bus voltage feedback Udc_fed and three-phase output currents ias and ibs from a standard motor drive control system, performing three-phase-two-phase conversion and rotation conversion on the three-phase output currents ias and ibs to obtain active current feedback CurQ_fed; calculating an output frequency correction amount △f according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed; calculating a ramp frequency command f_rmp, and superimposing the output frequency correction amount △f to obtain an output frequency f_run of the frequency converter; the present invention forms a dual closed-loop control of bus voltage and active current, and can realize bus stability control of the frequency converter without increasing the hardware cost of the system.

Description

Technical Field

[0001] The invention belongs to the technical field of power electronics and electric drive, and in particular relates to a method and system for controlling the voltage stability of a frequency converter bus. Background Art

[0002] Nowadays, frequency converters are widely used in speed control applications such as fans, water pumps and compressors. Frequency converters usually use rectifier modules to convert the input AC power into DC form, and then configure a certain number of capacitors to achieve voltage stabilization, energy storage and filtering. The bus voltage of the frequency converter is easily affected by the actual working conditions and the operating status of the motor. When the motor decelerates to generate electricity or the load changes suddenly, the bus voltage will be over-voltage due to the pump-up voltage generated by the motor kinetic energy feedback; the instantaneous power outage of the power grid will cause the bus voltage to be under-voltage due to power supply interruption. In order to prevent the bus voltage from changing drastically due to changes in the motor status, load or power supply conditions, thereby triggering the frequency converter trip protection.

[0003] The inverter generally integrates a bus voltage stability control algorithm to avoid frequent inverter tripping and affecting normal customer use. The common bus voltage stability control method is that when the actual bus voltage exceeds the set overvoltage warning value, the deceleration time is automatically extended according to the parameters set by the user to suppress the motor feedback energy, or the output frequency is increased to consume the bus voltage. When the actual bus voltage is lower than the undervoltage warning value, the output frequency is reduced according to the parameters set by the user, so that the motor feeds back energy to maintain the bus voltage stability. The disadvantage of the traditional method is that the final bus voltage stability is greatly affected by the parameter setting, and it is difficult to adapt to the needs of different loads. In addition, in order to obtain a satisfactory control effect, the relevant parameters need to be repeatedly debugged, which is very inconvenient to use. Summary of the invention

[0004] In view of the above-mentioned deficiencies in the prior art, the present invention provides a method and system for controlling the voltage stability of a frequency converter bus to solve the above-mentioned technical problems.

[0005] In a first aspect, the present invention provides a method for controlling a converter bus voltage stability, comprising:

[0006] A DC bus voltage feedback Udc_fed and three-phase output currents ias and ibs are obtained from a standard motor drive control system, and the three-phase output currents ias and ibs are transformed from three phases to two phases and rotated to obtain an active current feedback CurQ_fed;

[0007] Calculating the output frequency correction value △f according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed;

[0008] Calculate the ramp frequency command f_rmp, and add the output frequency correction value △f to obtain the output frequency f_run of the inverter;

[0009] According to the relationship between the set output voltage and the output frequency, determine the command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter, and perform angle integration on the output frequency f_run of the inverter to obtain the command voltage angle V_theta, and use the command voltage angle V_theta as the transformation angle of the rotation transformation;

[0010] The space vector PWM calculation is performed according to the command voltage amplitude V_rmp and the command voltage angle V_theta to obtain the modulation signal, which is fed back to the standard motor drive control system.

[0011] Further, the three-phase-to-two-phase conversion and rotation conversion are performed on the three-phase output currents ias and ibs to obtain active current feedback CurQ_fed, including:

[0012] The three-phase output currents ias and ibs are transformed into a coordinate system to obtain the two-phase output currents i_alfa and i_beta. The coordinate system transformation formula is as follows: i_alfa=ias; i_beta =1 / (ias+2×ibs);

[0013] According to the rotation angle V_theta, the two-phase output currents i_alfa and i_beta are rotated and transformed to obtain the active current feedback CurQ_fed. The rotation transformation formula is as follows:

[0014] CurQ_fed=i_alfa×cos(V_theta)+i_beta×sin(V_theta).

[0015] Further, the calculating of the output frequency correction value Δf according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed includes:

[0016] Obtain the bus voltage given range Udc_ref, form negative feedback with the DC bus voltage feedback Udc_fed, and obtain the active current command CurQ_ref through the bus voltage IP controller;

[0017] The active current command CurQ_ref is obtained, and a negative feedback is formed with the active current feedback CurQ_fed, and the output frequency correction value Δf is obtained through the active current IP controller.

[0018] Further, the calculation of the ramp frequency command f_rmp includes:

[0019] Get the motor operation command frequency f_set generated according to the given target frequency;

[0020] Taking the motor running command frequency f_set as the target, the ramp frequency command f_rmp is calculated according to the set acceleration and deceleration time.

[0021] Furthermore, it also includes:

[0022] The generation of the ramp frequency is controlled according to the output frequency correction value △f. When the output frequency correction value △f is not equal to 0, the frequency acceleration and deceleration are suspended and the output frequency remains unchanged; when the output frequency correction value △f is equal to 0, the ramp frequency instruction f_rmp continues to be generated.

[0023] In a second aspect, the present invention provides a converter bus voltage stability control system, comprising:

[0024] A standard motor drive control system, used to detect DC bus voltage feedback Udc_fed and output currents ias and ibs, including a three-phase power acquisition unit, an uncontrolled rectifier unit, and a three-phase inverter bridge. The three-phase power acquisition unit is used to obtain three-phase alternating current from the power grid, the uncontrolled rectifier unit is used to convert the three-phase alternating current into three-phase direct current, and the three-phase inverter bridge is used to convert the three-phase direct current into alternating current with adjustable frequency and voltage to drive the motor;

[0025] A current feedback unit, used for performing three-phase-to-two-phase conversion and rotation conversion on the three-phase output currents ias and ibs to obtain active current feedback CurQ_fed;

[0026] A frequency feedback unit, used for calculating an output frequency correction value △f according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed;

[0027] A frequency correction unit, used to calculate the ramp frequency command f_rmp, and superimpose the output frequency correction value △f to obtain the output frequency f_run of the frequency converter;

[0028] A voltage generating unit, used for determining a command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter according to the relationship between the set output voltage and the output frequency, and performing angle integration on the output frequency f_run of the inverter to obtain a command voltage angle V_theta, and using the command voltage angle V_theta as a transformation angle of the rotation transformation;

[0029] The space vector PWM unit performs space vector PWM calculation according to the command voltage amplitude V_rmp and the command voltage angle V_theta, obtains a modulation signal, and feeds it back to the standard motor drive control system.

[0030] Furthermore, the current feedback unit includes:

[0031] The three-phase to two-phase conversion unit is used to perform coordinate system conversion on the three-phase output currents ias and ibs to obtain the two-phase output currents i_alfa and i_beta. The coordinate system conversion formula is as follows: i_alfa=ias; i_beta =1 / (ias+2×ibs);

[0032] The rotation conversion unit is used to perform rotation conversion on the two-phase output currents i_alfa and i_beta according to the rotation angle V_theta to obtain the active current feedback CurQ_fed. The rotation conversion formula is as follows:

[0033] CurQ_fed=i_alfa×cos(V_theta)+i_beta×sin(V_theta).

[0034] Furthermore, the frequency feedback unit is used to: obtain a bus voltage given range Udc_ref, form negative feedback with the DC bus voltage feedback Udc_fed, and obtain an active current command CurQ_ref through a bus voltage IP controller; obtain the active current command CurQ_ref, form negative feedback with the active current feedback CurQ_fed, and obtain an output frequency correction amount △f through an active current IP controller.

[0035] Furthermore, the frequency correction unit includes:

[0036] The frequency command unit is used to obtain the motor operation command frequency f_set generated according to the given target frequency;

[0037] The ramp frequency generating unit is used to calculate the ramp frequency command f_rmp based on the set acceleration and deceleration time with the motor operation command frequency f_set as the target;

[0038] The adder is used to add the ramp frequency instruction f_rmp to the output frequency correction value Δf to obtain the output frequency f_run of the frequency converter.

[0039] Furthermore, the voltage generating unit comprises:

[0040] A V / F curve calculation unit, used to determine a command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter according to a set relationship between the output voltage and the output frequency;

[0041] The angle integrator is used to perform angle integration on the output frequency f_run of the frequency converter to obtain a command voltage angle V_theta, and use the command voltage angle V_theta as the transformation angle of the rotation transformation unit.

[0042] The beneficial effect of the present invention is that the present invention provides a method and system for controlling the bus voltage stability of a frequency converter, obtains feedback of the DC bus voltage and active current, performs online correction of the output frequency, and re-controls the bus voltage stability control through the corrected output frequency, forming a double closed-loop control of the bus voltage and active current, and can achieve the stable control of the frequency converter bus without increasing the system hardware cost, and prevent the frequent tripping protection of the frequency converter from affecting the normal use of customers when the motor state, load or power grid changes suddenly. In addition, the design principle of the present invention is reliable, the structure is simple, and it has a very broad application prospect. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, for ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0044] Figure 1 is a control block diagram of a method for stabilizing a frequency converter bus voltage in one embodiment of the present invention;

[0045] Figure 2 It is a schematic diagram of an IP controller used in one embodiment of the present invention. DETAILED DESCRIPTION

[0046] In order to enable those skilled in the art to better understand the technical solutions in the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present invention.

[0047] like Figure 1 As shown, the present invention forms an inner and outer double-loop control by adding a bus voltage closed loop and an active current closed loop to a standard motor drive control system, and keeps the bus voltage constant in both overvoltage and undervoltage states.

[0048] The standard motor drive control system includes: the three-phase power supply 11 converts the three-phase AC power into DC power through the uncontrolled rectifier unit 12, and the three-phase inverter bridge 13 converts the DC power into AC power with adjustable frequency and voltage to drive the motor 14. The inverter detects the DC bus voltage feedback Udc_fed of the three-phase inverter bridge 13, and also detects the three-phase output currents ias and ibs.

[0049] The method includes:

[0050] A DC bus voltage feedback Udc_fed and three-phase output currents ias and ibs are obtained from a standard motor drive control system, and the three-phase output currents ias and ibs are transformed from three phases to two phases and rotated to obtain an active current feedback CurQ_fed;

[0051] Calculating the output frequency correction value △f according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed;

[0052] Calculate the ramp frequency command f_rmp, and add the output frequency correction value △f to obtain the output frequency f_run of the inverter;

[0053] According to the relationship between the set output voltage and the output frequency, the command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter is determined, and the output frequency f_run of the inverter is angularly integrated to obtain the command voltage angle V_theta, the angle integral is V_theta=∫f_rundt, and the command voltage angle V_theta is used as the transformation angle of the rotation transformation;

[0054] The space vector PWM calculation is performed according to the command voltage amplitude V_rmp and the command voltage angle V_theta to obtain the modulation signal, which is fed back to the standard motor drive control system.

[0055] In this embodiment, the relationship between the output voltage and the output frequency is set by the user or the system. The present invention provides a method for stabilizing the bus voltage of a frequency converter, obtains feedback of the DC bus voltage and the active current, corrects the output frequency online, and re-controls the bus voltage through the corrected output frequency to form a dual closed-loop control of the bus voltage and the active current. Without increasing the hardware cost of the system, the bus stability control of the frequency converter can be achieved to prevent the frequent tripping of the frequency converter for protection when the motor state, load or power grid undergoes a sudden change, affecting the normal use of customers.

[0056] Optionally, as an embodiment of the present invention, the three-phase output currents ias and ibs are subjected to three-phase-to-two-phase transformation and rotation transformation to obtain active current feedback CurQ_fed, including: the three-phase output currents ias and ibs are subjected to coordinate system transformation to obtain two-phase output currents i_alfa and i_beta, and the coordinate system transformation formula is as follows: i_alfa=ias; i_beta=1 / (ias+2×ibs);

[0057] According to the rotation angle V_theta, the two-phase output currents i_alfa and i_beta are rotated and transformed to obtain the active current feedback CurQ_fed. The rotation transformation formula is as follows:

[0058] CurQ_fed=i_alfa×cos(V_theta)+i_beta×sin(V_theta).

[0059] In this embodiment, if Figure 2 As shown, the two-phase output current i_alfa and i_beta are decomposed to obtain the active current feedback CurQ_fed and the reactive current feedback CurD_fed, and the formula is:

[0060] CurD_fed=i_alfa×sin(V_theta)-i_beta×cos(V_theta);

[0061] CurQ_fed=i_alfa×cos(V_theta)+i_beta×sin(V_theta).

[0062] Optionally, as an embodiment of the present invention, the output frequency correction amount △f is calculated according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed, including: obtaining a bus voltage given range Udc_ref, forming negative feedback with the DC bus voltage feedback Udc_fed, and obtaining an active current command CurQ_ref through a bus voltage IP controller; obtaining the active current command CurQ_ref, forming negative feedback with the active current feedback CurQ_fed, and obtaining the output frequency correction amount △f through an active current IP controller.

[0063] In this embodiment, the bus voltage given range Udc_ref includes an upper limit given value Udc_Max and a lower limit given value Udc_Min. The upper limit given value Udc_Max is used as the final stable value when the bus voltage is overvoltage; the lower limit given value Udc_Min is used as the final stable value when the bus voltage is undervoltage. The use of an IP controller can effectively reduce the overshoot of the feedback amount. By reducing the overshoot, the first overshoot wave head of the actual bus voltage can be effectively suppressed to prevent overvoltage protection from occurring.

[0064] When the bus voltage feedback Udc_fed exceeds the upper limit given value Udc_Max, the inverter will have an overvoltage warning, and the bus voltage IP controller will start to act, outputting a positive active current command CurQ_ref, forming a negative feedback with the active current feedback CurQ_fed, and through the active current IP controller, outputting a positive frequency correction △f, driving the motor to establish a positive acceleration trend, and consuming the bus voltage of the inverter. Moreover, the more the bus voltage feedback Udc_fed exceeds the upper limit given value Udc_Max, the more positive the active current command CurQ_ref is, and the larger the final output positive frequency correction △f is, the faster the bus voltage of the inverter is consumed.

[0065] When the bus voltage feedback Udc_fed is lower than the lower limit given value Udc_Min, the inverter will have an undervoltage warning, and the bus voltage IP controller will start to act, outputting a negative active current command CurQ_ref, forming a negative feedback with the active current feedback CurQ_fed, and through the active current IP controller, outputting a negative frequency correction value △f, driving the motor to establish a deceleration trend, and feeding back energy to maintain the bus voltage stability of the inverter. Moreover, the more the bus voltage feedback Udc_fed is lower than the lower limit given value Udc_Min, the more negative the active current command CurQ_ref is, and the larger the final output negative frequency correction value △f is, and the faster the energy is fed back to maintain the bus voltage of the inverter.

[0066] The method provided in this embodiment can take into account both bus overvoltage and undervoltage conditions and achieve stable control of the bus voltage.

[0067] In one implementation, in order to further reduce system overshoot and speed up the response speed, when the bus voltage feedback Udc_fed reaches 95% of the upper limit given value Udc_Max, that is, the moment when overvoltage is about to occur, the integral unit of the bus voltage IP controller is assigned the maximum positive active current value, and the integral unit of the active current IP controller is assigned the value of: the maximum output frequency - the current output frequency; when the bus voltage feedback Udc_fed reaches 105% of the lower limit value Udc_Min, that is, the moment when undervoltage is about to occur, the integral unit of the bus voltage IP controller is assigned the maximum negative active current value, and the integral unit of the active current IP controller is assigned the value of: the maximum output frequency - the current output frequency.

[0068] Optionally, as an embodiment of the present invention, the calculation of the ramp frequency command f_rmp includes: obtaining a motor operation command frequency f_set generated according to a given target frequency, the given target frequency is given by a user or a system, and the motor operation command frequency f_set is used as a target, and according to set acceleration and deceleration time, the ramp frequency command f_rmp is calculated; the generation of the ramp frequency is controlled according to the output frequency correction amount △f, when the output frequency correction amount △f is not equal to 0, the frequency acceleration and deceleration is paused, and the output frequency remains unchanged; when the output frequency correction amount △f is equal to 0, the ramp frequency command f_rmp continues to be generated.

[0069] The definition of the inverter acceleration and deceleration time is as follows: the acceleration time is the time required for the output frequency to rise from 0 to the maximum value, and the deceleration time is the time required for the output frequency to fall from the maximum value to 0. Usually, the acceleration and deceleration time are determined by the rise and fall of the frequency setting signal. When the motor accelerates, the rise rate must be limited to prevent overcurrent, and when decelerating, the fall rate must be limited to prevent overvoltage. In this embodiment, the frequency ramp generation is suspended by the condition that the output frequency correction amount is zero, which plays an auxiliary role in the bus voltage stability control.

[0070] The present invention provides a method and system for controlling the voltage stability of a frequency converter bus, comprising:

[0071] A standard motor drive control system, used to detect the DC bus voltage feedback Udc_fed and the three-phase output currents ias and ibs, including a three-phase power supply acquisition unit, an uncontrolled rectifier unit, and a three-phase inverter bridge. The three-phase power supply acquisition unit is used to obtain three-phase alternating current from the power grid, the uncontrolled rectifier unit is used to convert the three-phase alternating current into three-phase direct current, and the three-phase inverter bridge is used to convert the three-phase direct current into alternating current with adjustable frequency and voltage to drive the motor;

[0072] A current feedback unit, used for performing three-phase-to-two-phase conversion and rotation conversion on the three-phase output currents ias and ibs to obtain active current feedback CurQ_fed;

[0073] A frequency feedback unit, used for calculating an output frequency correction value △f according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed;

[0074] A frequency correction unit, used to calculate the ramp frequency command f_rmp, and superimpose the output frequency correction value △f to obtain the output frequency f_run of the frequency converter;

[0075] A voltage generating unit, used for determining a command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter according to the relationship between the set output voltage and the output frequency, and performing angle integration on the output frequency f_run of the inverter to obtain a command voltage angle V_theta, and using the command voltage angle V_theta as a transformation angle of the rotation transformation;

[0076] The space vector PWM unit performs space vector PWM calculation according to the command voltage amplitude V_rmp and the command voltage angle V_theta, obtains a modulation signal, and feeds it back to the standard motor drive control system.

[0077] Optionally, as an embodiment of the present invention, the current feedback unit includes:

[0078] The three-phase to two-phase conversion unit is used to perform coordinate system conversion on the three-phase output currents ias and ibs to obtain the two-phase output currents i_alfa and i_beta. The coordinate system conversion formula is as follows: i_alfa=ias; i_beta=1 / (ias+2×ibs);

[0079] The rotation conversion unit is used to perform rotation conversion on the two-phase output currents i_alfa and i_beta according to the rotation angle V_theta to obtain the active current feedback CurQ_fed. The rotation conversion formula is as follows:

[0080] CurQ_fed=i_alfa×cos(V_theta)+i_beta×sin(V_theta).

[0081] Optionally, as an embodiment of the present invention, the frequency feedback unit is used to: obtain a bus voltage given range Udc_ref, form negative feedback with the DC bus voltage feedback Udc_fed, and obtain an active current command CurQ_ref through a bus voltage IP controller; obtain the active current command CurQ_ref, form negative feedback with the active current feedback CurQ_fed, and obtain an output frequency correction amount △f through an active current IP controller.

[0082] Optionally, as an embodiment of the present invention, the frequency correction unit includes:

[0083] The frequency command unit is used to obtain the motor operation command frequency f_set generated according to the given target frequency;

[0084] The ramp frequency generating unit is used to calculate the ramp frequency command f_rmp based on the set acceleration and deceleration time with the motor operation command frequency f_set as the target;

[0085] The adder is used to add the ramp frequency instruction f_rmp to the output frequency correction value Δf to obtain the output frequency f_run of the frequency converter.

[0086] Optionally, as an embodiment of the present invention, the voltage generating unit includes:

[0087] A V / F curve calculation unit, used to determine a command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter according to a set relationship between the output voltage and the output frequency;

[0088] The angle integrator is used to perform angle integration on the output frequency f_run of the frequency converter to obtain a command voltage angle V_theta, and use the command voltage angle V_theta as the transformation angle of the rotation transformation unit.

[0089] Although the present invention has been described in detail by referring to the accompanying drawings and in combination with the preferred embodiments, the present invention is not limited thereto. Without departing from the spirit and essence of the present invention, a person of ordinary skill in the art may make various equivalent modifications or substitutions to the embodiments of the present invention, and these modifications or substitutions shall be within the scope of the present invention or any person skilled in the art who is familiar with the present invention may easily think of changes or substitutions within the technical scope disclosed by the present invention, and shall be within the scope of protection of the present invention. Therefore, the scope of protection of the present invention shall be subject to the scope of protection of the claims.

Claims

1. A method for controlling the voltage stability of a frequency converter bus, characterized in that: include: A DC bus voltage feedback Udc_fed and three-phase output currents ias and ibs are obtained from a standard motor drive control system, and the three-phase output currents ias and ibs are transformed from three phases to two phases and rotated to obtain an active current feedback CurQ_fed; Calculating the output frequency correction value △f according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed; Calculate the ramp frequency command f_rmp, and add the output frequency correction value △f to obtain the output frequency f_run of the inverter; According to the relationship between the set output voltage and the output frequency, determine the command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter, and perform angle integration on the output frequency f_run of the inverter to obtain the command voltage angle V_theta, and use the command voltage angle V_theta as the transformation angle of the rotation transformation; Perform space vector PWM calculation based on command voltage amplitude V_rmp and command voltage angle V_theta to obtain a modulation signal, which is fed back to the standard motor drive control system; The ramp frequency is generated according to the output frequency correction value △f. When the output frequency correction value △f is not equal to 0, the frequency acceleration and deceleration are suspended and the output frequency remains unchanged. When the output frequency correction value △f is equal to 0, the ramp frequency command f_rmp continues to be generated; The step of calculating the ramp frequency command f_rmp comprises: Get the motor operation command frequency f_set generated according to the given target frequency; Taking the motor running command frequency f_set as the target, the ramp frequency command f_rmp is calculated according to the set acceleration and deceleration time.

2. The method according to claim 1, characterized in that The three-phase output currents ias and ibs are subjected to three-phase-to-two-phase conversion and rotation conversion to obtain active current feedback CurQ_fed, including: The three-phase output currents ias and ibs are transformed into a coordinate system to obtain two-phase output currents i_alfa and i_beta. The coordinate system transformation formula is as follows: i_alfa=ias; i_beta =1 / (ias+2×ibs); According to the rotation angle V_theta, the two-phase output currents i_alfa and i_beta are rotated and transformed to obtain the active current feedback CurQ_fed. The rotation transformation formula is as follows: CurQ_fed=i_alfa×cos(V_theta)+i_beta×sin(V_theta).

3. The method according to claim 1, characterized in that The calculating the output frequency correction value Δf according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed comprises: Obtain the bus voltage given range Udc_ref, form negative feedback with the DC bus voltage feedback Udc_fed, and obtain the active current command CurQ_ref through the bus voltage IP controller; The active current command CurQ_ref is obtained, and a negative feedback is formed with the active current feedback CurQ_fed, and the output frequency correction value Δf is obtained through the active current IP controller.

4. A frequency converter bus voltage stability control system, characterized in that: include: A standard motor drive control system, used to detect DC bus voltage feedback Udc_fed and output currents ias and ibs, including a three-phase power acquisition unit, an uncontrolled rectifier unit, and a three-phase inverter bridge. The three-phase power acquisition unit is used to obtain three-phase alternating current from the power grid, the uncontrolled rectifier unit is used to convert the three-phase alternating current into three-phase direct current, and the three-phase inverter bridge is used to convert the three-phase direct current into alternating current with adjustable frequency and voltage to drive the motor; A current feedback unit, used for performing three-phase-to-two-phase conversion and rotation conversion on the three-phase output currents ias and ibs to obtain active current feedback CurQ_fed; A frequency feedback unit, used for calculating an output frequency correction value △f according to the DC bus voltage feedback Udc_fed and the active current feedback CurQ_fed; A frequency correction unit, used to calculate the ramp frequency command f_rmp, and superimpose the output frequency correction value △f to obtain the output frequency f_run of the frequency converter; A voltage generating unit, used for determining a command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter according to the relationship between the set output voltage and the output frequency, and performing angle integration on the output frequency f_run of the inverter to obtain a command voltage angle V_theta, and using the command voltage angle V_theta as a transformation angle of the rotation transformation; The space vector PWM unit performs space vector PWM calculation according to the command voltage amplitude V_rmp and the command voltage angle V_theta, obtains the modulation signal, and feeds it back to the standard motor drive control system; The frequency correction unit comprises: A frequency command unit, used to obtain a motor operation command frequency f_set generated according to a given target frequency; The ramp frequency generating unit is used to calculate the ramp frequency command f_rmp according to the set acceleration and deceleration time with the motor operation command frequency f_set as the target; the ramp frequency generation is controlled according to the output frequency correction value △f; when the output frequency correction value △f is not equal to 0, the frequency acceleration and deceleration is suspended, and the output frequency remains unchanged; when the output frequency correction value △f is equal to 0, the ramp frequency command f_rmp continues to be generated; The adder is used to add the ramp frequency instruction f_rmp to the output frequency correction value Δf to obtain the output frequency f_run of the frequency converter.

5. The system according to claim 4, characterized in that The current feedback unit comprises: The three-phase to two-phase conversion unit is used to perform coordinate system conversion on the three-phase output currents ias and ibs to obtain the two-phase output currents i_alfa and i_beta. The coordinate system conversion formula is as follows: i_alfa=ias; i_beta =1 / (ias+2×ibs); The rotation conversion unit is used to perform rotation conversion on the two-phase output currents i_alfa and i_beta according to the rotation angle V_theta to obtain the active current feedback CurQ_fed. The rotation conversion formula is as follows: CurQ_fed=i_alfa×cos(V_theta)+i_beta×sin(V_theta).

6. The system according to claim 4, characterized in that The frequency feedback unit is used to: obtain the bus voltage given range Udc_ref, form negative feedback with the DC bus voltage feedback Udc_fed, and obtain the active current command CurQ_ref through the bus voltage IP controller; obtain the active current command CurQ_ref, form negative feedback with the active current feedback CurQ_fed, and obtain the output frequency correction value △f through the active current IP controller.

7. The system according to claim 5, characterized in that The voltage generating unit comprises: A V / F curve calculation unit, used to determine a command voltage amplitude V_rmp corresponding to the output frequency f_run of the inverter according to a set relationship between the output voltage and the output frequency; The angle integrator is used to perform angle integration on the output frequency f_run of the frequency converter to obtain a command voltage angle V_theta, and use the command voltage angle V_theta as the transformation angle of the rotation transformation unit.

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