CN108123593B - PFC circuit, motor control system and variable frequency air conditioner - Google Patents

PFC circuit, motor control system and variable frequency air conditioner Download PDF

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Publication number
CN108123593B
CN108123593B CN201810093556.8A CN201810093556A CN108123593B CN 108123593 B CN108123593 B CN 108123593B CN 201810093556 A CN201810093556 A CN 201810093556A CN 108123593 B CN108123593 B CN 108123593B
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value
current
voltage
motor
axis
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CN108123593A (en
Inventor
霍军亚
段文训
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GD Midea Air Conditioning Equipment Co Ltd
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GD Midea Air Conditioning Equipment Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4225—Arrangements for improving power factor of AC input using a non-isolated boost converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P23/00—Arrangements or methods for the control of AC motors characterised by a control method other than vector control
    • H02P23/26—Power factor control [PFC]
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
    • H02P27/00—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage
    • H02P27/04—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage
    • H02P27/06—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters
    • H02P27/08—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation
    • H02P27/085—Arrangements or methods for the control of AC motors characterised by the kind of supply voltage using variable-frequency supply voltage, e.g. inverter or converter supply voltage using dc to ac converters or inverters with pulse width modulation wherein the PWM mode is adapted on the running conditions of the motor, e.g. the switching frequency
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

Abstract

The invention provides a PFC circuit, a motor control system and a variable frequency air conditioner, wherein the motor control system comprises a reactor, a rectifying part, a current detection part, a filter circuit, an alternating current voltage sampling part, a direct current voltage sampling part and an operation control part, the rectifying part is formed by connecting a rectifying unit comprising two rectifying diodes connected in series and a switching unit comprising two switching tubes connected in series in parallel, the operation control part comprises a PFC operation control part, and the operation control part comprises a PFC operation control part and is used for correcting power factors of input alternating current by acquiring a given value of a direct current bus voltage of the motor and generating a switching tube of the PFC switch duty ratio signal according to an alternating current input voltage value, a direct current bus voltage value and the given value of the direct current bus voltage. Compared with the traditional PFC circuit, the PFC circuit provided by the embodiment of the invention can effectively improve the efficiency and reduce the common mode noise, so that the reliability of the whole motor control system is improved.

Description

PFC circuit, motor control system and variable frequency air conditioner
Technical Field
The invention relates to the technical field of variable frequency air conditioners, in particular to a PFC circuit, a motor control system and a variable frequency air conditioner.
Background
In order to meet the energy-saving requirement of household appliances, variable frequency air conditioners are rapidly developed, and active power factor correction is widely applied to electric control parts of variable frequency air conditioners. At present, a Boost type circuit is adopted in the electric control power factor correction part of most variable frequency air conditioners, and after current flows through a rectifier bridge, the current is supplied to a motor inverter through an inductor and a diode; or a bridgeless PFC (power factor correction) circuit appears, but the bridgeless PFC circuit improves the AC-DC conversion efficiency to some extent, but has a problem of large common mode noise.
The foregoing is provided merely for the purpose of facilitating understanding of the technical solutions of the present invention and is not intended to represent an admission that the foregoing is prior art.
Disclosure of Invention
The invention mainly aims to provide a PFC circuit, a motor control system and a variable frequency air conditioner, and aims to solve the problems of low conversion efficiency or large common mode noise in the traditional PFC circuit.
In order to achieve the above object, the present invention provides a PFC circuit, which includes a reactor, a rectifying unit, a current detecting unit, a filter circuit, an ac voltage sampling unit, a dc voltage sampling unit, and an arithmetic control unit; the reactor is connected with the input end of the alternating current power supply, and the reactor and the rectifying part are connected in series in an alternating current power supply loop; the output end of the rectifying part is connected with a direct current bus, and the filter circuit is connected with the rectifying part through the direct current bus; the current detection part is connected in series with the direct current bus;
The rectifying part comprises a first diode, a second diode, a first switching tube and a second switching tube with freewheeling diodes, wherein a public connection point of the first diode and the second diode after being connected in series is connected with an L line of an alternating current power supply; the public connection point of the first switching tube and the second switching tube which are connected in series is connected with an N line of an alternating current power supply; one end of the first switching tube and one end of the second switching tube which are connected in series are connected with the cathode of the first diode, the other end of the first switching tube and the other end of the second switching tube which are connected in series are connected with the anode of the second diode, and the control ends of the first switching tube and the second switching tube are respectively connected with the operation control part; wherein the method comprises the steps of
The current detection part is used for detecting the direct current bus current and obtaining a corresponding direct current bus current value; the filter circuit is used for carrying out smooth filtering on the direct current output by the rectification module so as to output direct current bus voltage; the alternating current voltage sampling part is used for detecting alternating current input voltage and obtaining a corresponding alternating current input voltage value; the direct-current voltage sampling part is used for detecting the direct-current bus voltage and obtaining a corresponding direct-current bus voltage value;
the operation control part comprises a PFC operation control part, wherein the PFC operation control part is used for obtaining a DC bus voltage given value of motor operation and generating PFC switch duty ratio signals according to the AC input voltage value, the DC bus current value and the DC bus voltage given value to drive a switching tube of the rectifying part to work so as to correct power factors of the input AC.
Preferably, the current detection unit is connected in series between the rectifying unit and the filter circuit, and determines a current value passing through the reactor by detecting the dc bus current.
Preferably, the current detection unit performs current sampling at an intermediate time when the first switching tube or the second switching tube is turned off.
Preferably, the motor control system includes a phase current sampling part and an inverter;
the phase current sampling part is used for sampling a phase current signal of the motor and inputting the phase current signal to the motor operation control part;
the input end of the inverter is connected with the direct current bus, and the output end of the inverter is connected with the motor;
the operation control part also comprises a motor operation control part, wherein the motor operation control part is used for calculating and generating a pulse width signal according to the direct current bus voltage value, the phase current signal of the motor and the target rotating speed value of the motor, and also generating a triangular carrier signal and generating a PWM control signal to the inverter according to the triangular carrier signal and the pulse width signal so as to drive the motor to operate.
Preferably, the motor operation control unit includes:
a position/speed estimation module for estimating a rotor position of the motor to obtain a rotor angle estimate and a motor speed estimate of the motor;
The Q-axis given current value calculation module is used for calculating a Q-axis given current value according to the motor target rotating speed value and the motor speed estimated value;
the D-axis given current value calculation module is used for calculating a D-axis given current value according to the maximum output voltage of the inverter and the output voltage amplitude of the inverter;
the current control module is used for calculating and generating the pulse width signal according to the Q-axis given current value, the D-axis given current value, the motor speed estimated value, the direct current bus voltage value and the phase current value sampled by the motor, and generating the PWM control signal to the inverter according to the triangular carrier signal and the pulse width signal so as to drive the motor to run.
Preferably, the D-axis given current value calculation module includes:
the weak magnetic controller is used for calculating the maximum output voltage of the inverter and the output voltage amplitude of the inverter to obtain an initial value of a D-axis given current value;
and the amplitude limiting unit is used for carrying out amplitude limiting processing on the initial value of the D-axis given current value to obtain the D-axis given current value.
Preferably, the current control module further includes:
and the Q-axis current value and D-axis current value calculation unit is used for calculating according to the phase current value and the angle estimation value to obtain the Q-axis current value and the D-axis current value.
Preferably, the current control module is further configured to:
the phase current value of the motor operation is obtained, a first Q-axis inductance value, a second Q-axis inductance value, a first D-axis inductance value and a second D-axis inductance value which correspond to the pre-stored first phase current value and second phase current value are respectively obtained, and the Q-axis inductance value and the D-axis inductance value are calculated according to the phase current value, the first phase current value, the second phase current value, the first Q-axis inductance value, the second Q-axis inductance value, the first D-axis inductance value and the second D-axis inductance value.
Preferably, the PFC operation control unit includes a weak magnetic critical voltage calculation module, an ac voltage parameter determination module, a weak magnetic critical voltage value limiting module, an inductance current value calculation module, a PFC switching signal duty ratio calculation module, and a switching signal generation module; wherein the method comprises the steps of
The weak magnetic critical voltage value calculation module is used for calculating the weak magnetic critical voltage value when the motor operates according to the Q-axis given voltage value, the D-axis given voltage value and the modulation factor Kmax;
the alternating current voltage parameter determining module is used for calculating according to the alternating current input voltage value acquired by the alternating current voltage sampling part to respectively obtain an alternating current input voltage polarity identification signal, an alternating current input voltage effective value, an alternating current input voltage absolute value and a zero crossing detection signal;
The weak magnetic critical voltage value amplitude limiting module is used for limiting the weak magnetic critical voltage value to obtain the given value of the DC bus voltage;
the inductance current given value calculation module is used for calculating according to the direct current bus voltage given value and the direct current bus voltage value to obtain the inductance current given value;
the inductance current value calculation module is used for calculating the inductance current value according to the direct current bus current value;
the PFC switch signal duty ratio calculation module is used for calculating the PFC switch signal duty ratio signal according to the inductance current given value and the inductance current value;
the switching signal generation module is used for calculating a switching signal according to the PFC switching signal duty ratio signal, the alternating current input voltage polarity indication signal and the alternating current voltage zero crossing signal so as to control the first switching tube or the second switching tube to work.
In order to achieve the above purpose, the invention also provides a motor control system, which comprises the PFC circuit.
In order to achieve the above purpose, the invention also provides a variable frequency air conditioner, which comprises the motor control system.
The PFC circuit applied to the motor control system comprises a reactor, a rectifying part, a current detection part, a filter circuit, an alternating current voltage sampling part, a direct current voltage sampling part and an operation control part, wherein the rectifying part is formed by connecting a rectifying unit comprising two rectifying diodes in series and a switching unit comprising two switching tubes in series in parallel, so that a full-wave rectifying circuit is formed, the operation control part comprises the PFC operation control part, and the operation control part generates a PFC switch duty ratio signal according to an alternating current input voltage value, a direct current bus current value and a direct current bus voltage given value to drive the switching tubes of the rectifying part to work so as to correct power factors of input alternating current. Compared with the traditional PFC circuit, the PFC circuit provided by the embodiment of the invention can effectively improve the efficiency and reduce the common mode noise, so that the reliability of the whole motor control system is improved.
Drawings
Fig. 1 is a schematic circuit diagram of a PFC circuit according to a first embodiment of the present invention;
fig. 2 is a schematic circuit diagram of another circuit structure of the PFC circuit according to the first embodiment of the present invention;
fig. 3 is a schematic diagram of a current loop of the reactor according to the first embodiment, in which the current starts from the L line, when the reactor stores energy;
FIG. 4 is a schematic diagram of a current loop for charging an electrolytic capacitor from the L line in the first embodiment;
fig. 5 is a schematic diagram of a current loop of the reactor according to the first embodiment, in which the current starts from line N when energy is stored;
FIG. 6 is a schematic diagram of a current loop for charging an electrolytic capacitor from the N line in the first embodiment;
fig. 7 is a schematic diagram of a sine wave modulation waveform of a PWM signal controlling an inverter in the first embodiment;
fig. 8 is a schematic diagram of the correspondence between the PWM signal for controlling the inverter and the isosceles triangle carrier signal in the first embodiment;
fig. 9 is a schematic diagram showing a PWM signal waveform and an ac current waveform outputted from the PFC operation control section 51 according to the second embodiment of the PFC circuit of the present invention;
fig. 10 is a schematic diagram of a functional module of a motor operation control unit according to a third embodiment of the PFC circuit of the present invention;
FIG. 11 is a graph of D-axis inductance and Q-axis inductance of a motor as a function of current;
fig. 12 is a functional block diagram of a PFC operation control unit according to a fourth embodiment of the PFC circuit of the present invention.
Detailed Description
Embodiments of the present invention are described in detail below, examples of which are illustrated in the accompanying drawings, wherein like or similar reference numerals refer to like or similar elements or elements having like or similar functions throughout. The embodiments described below by referring to the drawings are illustrative and intended to explain the present invention and should not be construed as limiting the invention.
Referring to fig. 1, fig. 1 is a schematic diagram of a PFC circuit according to a first embodiment of the present invention, and for convenience of explanation, only a portion related to the embodiment of the present invention is shown, and the details are as follows:
the PFC of the embodiment of the invention is applied to a motor control system and comprises a reactor L, a rectifying part 4, a current detecting part 3, a filter circuit 7, an alternating current voltage sampling part 2, a direct current voltage sampling part 6 and an operation control part 5; wherein the method comprises the steps of
The reactor L is connected to the input end of the ac power supply 1, and the reactor L and the rectifying unit 4 are connected in series in an ac power supply circuit.
The output end of the rectifying part 4 is connected with a direct current bus, and the filter circuit 7 is connected with the rectifying part 4 through the direct current bus; the filter circuit 7 is used for smoothing and filtering the direct current output by the rectifying module to output direct current bus voltage, and the filter circuit 7 mainly comprises an electrolytic capacitor EC in the figure.
The current detection part 3 is connected in series with the dc bus and is used for detecting the dc bus current value Idc, where the current detection part 3 can be based on a series resistance type current sampling circuit, and then output through a differential circuit connected with two ends of the resistor, and such a sampling circuit belongs to the prior art and is not described herein.
The ac voltage sampling unit 2 and the dc voltage sampling unit 6 are respectively used for sampling an ac input voltage value Uac and a dc bus voltage value Udc, where the dc voltage sampling unit 6 may be based on a simple voltage division sampling circuit formed by connecting a first voltage division resistor R4 and a second voltage division resistor R5 in series in the figure, and the circuit of the ac voltage sampling unit 2 may be the same as the dc voltage sampling unit 6, or may be based on other existing voltage sampling circuits such as a voltage sampling circuit of a transformer structure type.
The operation control part 5 includes a PFC operation control part 51, and the PFC operation control part 51 is configured to obtain a dc bus voltage given value Udref for motor operation, and generate a PFC switching duty signal according to the ac input voltage value Uac, the dc bus voltage value Udc, the dc bus current value Idc, and the dc bus voltage given value Udref to drive a switching tube of the rectifying part 4 to operate, so as to perform power factor correction on the input ac.
Specifically, the rectifying unit 4 includes a first rectifying unit 41 and a second switching unit 42, the first rectifying unit 41 includes a first diode D1 and a second diode D3 connected in series, the second switching unit 42 includes a first switching tube S7 and a second switching tube S8 with freewheeling diodes connected in series, the first rectifying unit 41 and the second switching unit 42 are connected in parallel, control ends of the first switching tube S7 and the second switching tube S8 are respectively connected with the operation control unit 5, and common points of the first diode D1 and the second diode D3 and common points of the first switching tube S7 and the second switching tube S8 are respectively connected with an L line and an N line of an ac power supply, so as to form an ac power supply loop.
In the figure, the first diode D1 and the second diode D3 may be common low-speed rectifying diodes, the first diode S7 and the second diode S8 are MOS transistors (Metal Oxid Semiconductor, metal oxide semiconductor), or may be other types of power transistors, such as IGBT transistors (Insulated Gate Bipolar Transistor, insulated gate bipolar transistors), the first diode D1 and the second diode D3 are connected in series, that is, the anode of the first diode D1 is connected to the cathode of the second diode D3, the common connection point after the first diode D1 and the second diode D3 are connected in series with the live wire of the ac power supply, that is, the source is connected to the cathode of the first diode D1, the drain is connected to the anode of the second diode S8, the first diode S7 is connected in series with the second diode S8, that is, the D of the first diode S7 is connected to the S of the second diode S8, the common connection point of the first diode S7 and the second diode S8 is connected to the anode of the first diode S6, and the freewheeling diode S6 are connected in series with the anode of the first diode S6 and the freewheeling diode S6, and the freewheeling diode S6 are connected in series inside the freewheeling diode S6.
The current detection unit 3 may be connected in series to the positive electrode side of the dc bus bar in fig. 1 or to the negative electrode side of the dc bus bar, and as shown in fig. 2, the function of detecting the dc bus bar current value Idc is the same as that of fig. 1. The current detecting section 3 may be connected in series between the rectifying section 4 and the filter circuit 7.
The PFC circuit shown in this embodiment operates as follows: as shown in fig. 3, when the PFC operation control unit 51 controls the first switching tube S7 to be turned on and the second switching tube S8 to be turned off, the ac power supply current starts from the live wire, i.e., the L line, and returns to the ac power supply zero line, i.e., the N line, to form a loop through the first diode D1, the S pole and the D pole of the first switching tube S7, and the reactor L; when the PFC operation control unit 51 controls the first switching tube S7 to be turned off, as shown in fig. 4, an induced electromotive force is generated in the reactor L, and a current direction of a current generated by the electromotive force flowing through the reactor L is identical to a current direction of the current flowing through the reactor L before the first switching tube S7 is turned off, and at this time, the current generated by the induced electromotive force of the reactor L flows through the first diode D1, the current detection unit 3, the electrolytic capacitor EC, the flywheel diode D6 of the second switching tube S8, and the reactor L returns to the N line, which is the zero line of the ac power supply, to charge the electrolytic capacitor EC, thereby realizing power factor correction, which is phase correction of the ac voltage and the ac current input from the rectifying unit 4 when the ac power supply current starts from the L line.
When the PFC operation control unit 51 controls the first switching tube S7 to be turned off and the second switching tube S8 to be turned on, as shown in fig. 5, at this time, the ac power supply current starts from the zero line, i.e., the N line, and flows through the reactor L, the S pole and D pole of the second switching tube S8, and the second diode D3, and returns to the ac power supply live line, i.e., the L line to form a loop, thereby realizing energy storage for the reactor L; when the PFC operation control unit 51 controls the second switching tube S8 to be turned off, as shown in fig. 6, an induced electromotive force is generated in the reactor L, and a current direction of a current generated by the electromotive force flowing through the reactor L is consistent with a current direction of the current flowing through the reactor L before the second switching tube S8 is turned off, and at this time, the current generated by the induced electromotive force of the reactor L returns to the L line, which is a live line of the ac power supply, through the flywheel diode D5 of the first switching tube S7, the current detection unit 3, the electrolytic capacitor EC, and the second diode D3 to charge the electrolytic capacitor EC, thereby realizing power factor correction, which is phase correction of the ac voltage and the ac current input from the rectifying unit 4 when the ac power supply current starts from the N line.
Accordingly, the PFC operation control section 51 realizes the power factor correction function in the full-wave rectification mode by controlling the alternate on and off of the first switching tube S7 and the second switching tube S8, respectively.
Further, the motor control system cited by the PFC circuit according to the embodiment of the present invention further includes a phase current sampling portion 9, where the phase current sampling portion 9 is configured to detect a phase current signal of the motor 10, obtain a corresponding phase current value, and input the phase current signal to the motor operation control portion 5, for example, phase current signals Iu, iv, iw in fig. 1, where the current sampling portion 9 may be implemented based on a three-resistor and single-electron current sampling scheme, which belongs to the prior art and is not described herein again.
The input end of the inverter 8 is connected with a direct current bus, the rectifying bus provides the direct current power supply for the inverter 8 to work, the output end of the inverter 8 is connected with the motor 10, the operation control part 5 further comprises a motor operation control part 52, the motor operation control part 52 is used for calculating and generating pulse width signals according to the direct current bus voltage value Udc, phase current signals Iu, iv and Iw of the motor and a target rotating speed value ωref of the motor 10, the operation control part 5 further generates triangular carrier signals, and PWM control signals are generated to the inverter 8 according to the triangular carrier signals and the pulse width signals so as to drive the motor 10 to operate.
Specifically, the motor operation control section 52 outputs six PWM control signals to the inverter 8 through calculation by further acquiring the dc bus voltage value Udc and the target rotation speed value ωref of the motor 10, according to the sampled phase current signals Iu, iv, iw of the motor 10, wherein the PWM control signals are macroscopically based on the sine wave modulation principle, as shown in fig. 7, the PWM control signal waveforms of one of the paths are finally obtained through modulation of the isosceles triangle carrier S2 by the sine wave voltage signal S3, as shown in fig. 7, the period T of the PWM is generally set to 100us-250us, and finally the motor 10 is driven by the inverter 8, and the sine waveforms are finally formed on the three windings of the motor 10, as shown in the dotted line part waveform S4 in fig. 7, due to the inductance characteristics of the motor windings.
Since the PWM frequency is high, when the motor operation control unit 52 performs pulse width calculation and generates a PWM control signal finally, it is realized based on the voltage Space Vector Pulse Width Modulation (SVPWM) principle, that is, a continuous triangular carrier signal is generated by calculating the generated pulse width signal and by a timer inside the motor operation control unit 52, and the PWM control signal is output finally by comparing the pulse width signal with the triangular carrier signal, and the PWM control signal has six paths, so that the S1-S6 switching tubes of the inverter 8 are controlled to operate respectively, and finally the inverter 8 outputs a three-phase driving signal to the motor 10 to realize the driving operation of the motor 10.
As shown in fig. 8, the waveform of the triangular carrier signal generated by the timer in the motor operation control portion 52 is shown as S6, the pulse width signals thereof are shown as Du1, du2 and Du3 in the figure, the actual software generates the PWM control signal waveform by sending the pulse width signals to the comparison register, and finally, one of the PWM control signals is generated by the timer based on the triangular carrier S6 as S5, wherein each of the triangular carrier periods corresponds to one of the PWM control signal periods. Wherein, each triangle in the triangle carrier signal S6 is an isosceles triangle, and the peak of each isosceles triangle is the same as the middle time of the effective pulse width of the PWM control signal in the isosceles triangle carrier period, such as the position of the peak of the first isosceles triangle corresponding to the effective pulse width of the first PWM pulse waveform in the figure, that is, the middle point b time of the a-c time in the figure. Different effective pulse width PWM control signals are finally generated through different pulse width signals. Six paths of PWM control signals are added to six switching tubes of the inverter 8 and finally form three vectors with 120-degree spatial mutual difference when controlling the motor 10, voltage vector signals changing along with time are finally synthesized, the amplitude of the voltage vector signals is constant, and the motor 10 rotates according to the same frequency of sine waves, so that the motor 10 runs under the control of the voltage vector signals.
The PFC circuit applied to the motor control system comprises a reactor L, a rectifying part 4, a current detection part 3, a filter circuit 7, an alternating current voltage sampling part 2, a direct current voltage sampling part 6 and an operation control part 5, wherein the rectifying part 4 is formed by connecting a rectifying unit comprising two rectifying diodes in series and a switching unit comprising two switching tubes in series in parallel, thus forming a full-wave rectifying circuit, the operation control part comprises a PFC operation control part 51, and the operation control part is used for correcting the power factor of the input alternating current by acquiring a given value Udref of the direct current bus voltage of the motor and generating PFC switch duty ratio signals according to an alternating current input voltage value Uac, a direct current bus voltage value Udc and the given value Udref of the direct current bus voltage to drive the switching tubes of the rectifying part 4 to work. Compared with the traditional PFC circuit, the PFC circuit provided by the embodiment of the invention can effectively improve the efficiency and reduce the common mode noise, so that the reliability of the whole motor control system is improved.
Further, as a second embodiment of the PFC circuit provided by the present invention, based on the first embodiment of the PFC circuit of the present invention, in the present embodiment, the current value I through the reactor is determined by detecting the dc bus current Idc L The current detection unit 3 performs current sampling at an intermediate time when the first switching tube S7 or the second switching tube S8 is turned off.
As is clear from the description of the operation principle of the PFC circuit in the first embodiment, when the PFC operation control unit 51 controls the first switching tube S7 or the second switching tube S8 to be turned on, the ac power supply current stores energy in the reactor L, that is, the current I flowing through the reactor at this time L Since the electrolytic capacitor EC is not charged at this time without passing through the electrolytic capacitor EC, no current flows through the dc bus, and only when the PFC operation control unit 51 controls the first switching tube S7 or the second switching tube S8 to be turned off, the current I generated by the induced electromotive force generated in the reactor L L The electrolytic capacitor EC is charged, and the current is applied to the dc bus, so that the current of the dc bus should be detected during the closing period of the first switching tube S7 or the second switching tube S8 in order to accurately detect the current of the dc bus.
When the PWM signal waveform output by the PFC operation control unit 51 as shown in fig. 9 controls the switching state of the first switching tube S7 or the second switching tube S8 to switch as S7 to control the PFC circuit to perform the power factor correction, the current detection unit 3 samples the dc bus current in a period of the PWM control signal when the first switching tube S7 or the second switching tube S8 is controlled to be at the middle time of the T2 period in the off period diagram, such as at time T1 in the diagram, because the switching state of the first switching tube S7 or the second switching tube S8 is switched The reactor L can perform energy storage and release conversion, and the reactor L stores energy during the opening period of the switch tube, and the current value I of the reactor passes through L The induced electromotive force generated by the reactor L during the closing period of the switch tube discharges the filtered electrolytic capacitor, and the current value I passing through the reactor L Reduce the alternating current I passing through the reactor L L The waveform schematic diagram of the PWM following the switching tube is shown in S8, where the current of the device increases at t1 when the switching tube is turned on, and the current decreases during t2 when the switching tube is turned off, so that it is important to select a suitable current sampling point, otherwise, a problem of large sampling error is caused. Due to the current i through the reactor when the first switching tube S7 or the second switching tube S8 is turned on L The current i through the reactor is only when the first switching tube S7 or the second switching tube S8 is closed without passing through the electrolytic capacitor EC L The current i passing through the electrolytic capacitor, i.e. the reactor at that time L As for the DC bus current value Idc, it is determined through experiments that the current sampled at the middle time of the switching tube closing period can represent the actual current value of the AC current in each PWM period more accurately, as shown in I L Sample is the current value obtained by actual sampling, and the magnitude of the sample is close to the current I of the reactor L Mean value of PWM control signal device variation over the switching tube as current value I through the reactor L Thus, the accuracy of the sampled current value is ensured, and thus the accuracy with which the FC operation control portion 51 controls the switching tube to operate is ensured, thereby improving the accuracy of power factor correction.
Further, as a third embodiment of the PFC circuit provided by the present invention, based on the first embodiment of the PFC circuit of the present invention, as shown in fig. 10, the motor operation control section 52 of the motor control system of the present embodiment further includes:
a position/speed estimation module 521 for estimating a rotor position of the motor to obtain a rotor angle estimation θest and a motor speed estimation ωest of the motor 10;
a Q-axis given current value Iqref calculation module 522 for calculating a Q-axis given current value Iqref from the motor target rotation speed value ωref and the motor speed estimation value ωest;
a D-axis given current value Idref calculation module 523 for calculating a D-axis given current value Idref from the maximum output voltage Vmax of the inverter and the output voltage amplitude V1 of the inverter;
a current control module 524 for calculating pulse width signals according to the Q-axis given current value Iqref, the D-axis given current value Idref, the motor speed estimation value ωest, the DC bus voltage value Udc and the phase current values Iu, iv and Iw sampled by the motor 10, and generating PWM control signals to the inverter 8 according to the triangular carrier signals and the pulse width signals to drive the motor 10 to operate
Specifically, the motor 10 in the embodiment of the present invention may be a motor without a position sensor, and when the position/speed estimation module 521 determines the rotor angle estimated value θest and the motor speed estimated value ωest of the motor 10, the above functions may be implemented by a flux linkage observation method, specifically, firstly, the function may be implemented according to the voltage V on the two-phase stationary coordinate system α 、V β And current I α 、I β The estimated value of the effective magnetic flux of the compressor motor in the alpha and beta axis directions of the two-phase stationary coordinate system is calculated as follows according to the following formula (1):
wherein,and->Estimated values of effective magnetic flux of motor in alpha and beta axis directions respectively, V α And V β Voltages in the alpha and beta axis directions, respectively, I α And I β Currents in alpha and beta axes respectively, R is stator resistance, L q Is the q-axis inductance parameter of the motor.
Then, a rotor angle estimated value θest of the compressor motor and a motor actual rotation speed value ωest are calculated according to the following formula (2):
wherein K is p_pll And K i_pll Respectively proportional integral parameter, theta err For the deviation angle estimate, ω f Is the bandwidth of the speed low pass filter.
Specifically, the Q-axis given current value calculation module 522 includes a superposition unit and a PI regulator. The superposition unit is used for calculating the difference between the motor target rotating speed value omega ref and the motor speed estimated value omega est, and the PI regulator is used for PI regulating according to the difference between the motor target rotating speed value omega ref and the motor speed estimated value omega est output by the superposition unit so as to output a Q-axis given current value Iqref.
Specifically, the D-axis given current value calculating module 523 includes a field weakening controller for calculating a maximum output voltage Vmax of the inverter 8 and an output voltage amplitude V1 of the inverter 8 to obtain a D-axis given current value initial value Id0, and a clipping unit for clipping the D-axis given current value initial value Id0 to obtain a D-axis given current value Idref.
In an embodiment of the present invention, the field weakening controller may calculate the initial value Id0 of the D-axis given current value according to the following formula (3):
wherein I is d0 Giving an initial value of a current value for the D axis, K i In order to integrate the control coefficient(s), V 1 v is the amplitude of the output voltage of the inverter d For D-axis voltage, v q For Q axis voltage, V max For maximum output of inverter 8Output voltage V dc Which is the dc bus voltage output by the rectifier 4.
In the embodiment of the present invention, the clipping unit obtains the D-axis given current value according to the following equation (4):
wherein Idref is the D-axis given current value, I demag And (5) demagnetizing current limiting value for the motor.
Specifically, the specific calculation of the current control module 524 is as follows:
according to the method, U, V, W three-phase current values Iu, iv and Iw are obtained by sampling the motor 10, clark transformation is performed by a three-phase stationary-two-phase stationary coordinate conversion unit, and the current I of the motor in the alpha and beta axis directions of the two-phase stationary coordinate system is obtained based on the following formula (5) α And I β
I α ＝I u
Then according to the rotor angle estimated value theta est The actual current values Iq and Id of the D axis and Q axis in the two-phase rotation coordinate system are calculated by the following equation (6) by Park conversion by the two-phase stationary-two-phase rotation coordinate conversion unit.
I d ＝I α cosθ est +I β sinθ est
I q ＝-I α sinθ est +I β cosθ est (6)
The calculation of the actual current values Iq and Id of the D-axis and Q-axis by the Q-axis current value and D-axis current value calculation unit in the current control module 524 is achieved by the above-described equations (5) and (6).
Further, the current control module 524 may calculate the Q-axis given voltage value and the D-axis given voltage value according to the following equation (7):
wherein Vq is a Q-axis given voltage value, vd is a D-axis given voltage value, iqref is a Q-axis given current value, idref is a D-axis given current value, iq is a Q-axis current, id is a D-axis current, kpd and Kid are respectively a D-axis current control proportional gain and an integral gain, kpq and Kiq are respectively a Q-axis current control proportional gain and an integral gain, ω is a motor rotation speed, ke is a counter potential coefficient of the motor 10, ld and Lq are respectively a D-axis inductance and a Q-axis inductance, the two parameters can be provided by a motor manufacturer, in particular, rated values can be taken in a change curve graph of the D-axis and the Q-axis along with current of the motor provided by the motor manufacturer,representing the integral of x (τ) over time.
Further, to further accurately obtain the D-axis inductance Ld and the Q-axis inductance Lq, the current control module 524 is further configured to: the method comprises the steps of obtaining a phase current value of motor operation, calling a first Q-axis inductance value, a second Q-axis inductance value, a first D-axis inductance value and a second D-axis inductance value which correspond to a first phase current value and a second phase current value which are pre-stored respectively, and calculating the Q-axis inductance value and the D-axis inductance value according to the phase current value, the first phase current value, the second phase current value, the first Q-axis inductance value, the second Q-axis inductance value, the first D-axis inductance value and the second D-axis inductance value. Specifically, by acquiring the phase current signals Iu, iv, iw of the motor 10 acquired by the current sampling section 9, the three phase currents are the same in magnitude, and only one of them is required to be used. The graph of the change of the D-axis inductance and the Q-axis inductance of the motor provided by the motor manufacturer along with the current is shown in fig. 11, wherein i is the winding current of the motor, namely the phase current value, at this time, a first Q-axis inductance value Lq1, a second Q-axis inductance value Lq2, a first D-axis inductance value Ld1 and a second D-axis inductance value Ld2, which respectively correspond to the first phase current value i1 and the second phase current value i2, can be pre-stored through the graph, and the D-axis inductance value Ld and the Q-axis inductance value Lq, which correspond to the currently detected phase current i, can be calculated according to the following difference calculation formula:
Ld＝Ld1+(Ld2-Ld1)*(i-i1)/(i2-i1)
Lq＝Lq1+(Lq2-Lq1)*(i-i1)/(i2-i1)
The D-axis inductance Ld and Q-axis inductance Lq values corresponding to the phase currents of the current motor 10 can be determined relatively accurately by the above-described formulas.
After the Q-axis given voltage value Vq and the D-axis given voltage value Vd are obtained, the motor rotor angle estimation value θ can be obtained est And performing Park inverse transformation on the Vq and the Vd through a two-phase rotation-two-phase stationary coordinate transformation unit to obtain voltage values V alpha and V beta on a fixed coordinate system, wherein a specific transformation formula (8) is as follows:
here, θ is the rotor angle of the motor 10, and the above-mentioned estimated rotor angle value θest may be taken here.
Further, the Clark inverse transformation can be performed by a two-phase stationary-three-phase stationary coordinate transformation unit according to the voltage values vα and vβ on the fixed coordinate system, to obtain three-phase voltages Vu, vv and Vw, and the specific transformation formula (9) is as follows:
V u ＝V α
then, the duty ratio calculation unit may perform duty ratio calculation according to the dc bus voltage Udc and the three-phase voltages Vu, vv and Vw, to obtain duty ratio control signals, that is, three-phase duty ratios Du, dv and Dw, where the specific calculation formula (10) is as follows:
D u ＝(V u +0.5V dc )/V dc
D v ＝(V v +0.5V dc )/V dc
D w ＝(V w +0.5V dc )/V dc (10)
wherein Udc is the dc bus voltage.
The three-phase duty ratio signal includes three pulse width signals, such as duty ratio signals Du1, du2 and Du3 corresponding to one phase duty ratio Du in fig. 8 at different time, and finally, three-way PWM control signals corresponding to the three-way pulse width signals are generated by a triangular carrier signal generated by a timer in the operation control part to the three-way switching tube of the upper bridge arm of the inverter 8, and three-way control signals of the lower bridge arm and three-way PWM control signals corresponding to the three-way pulse width signals are complementary to each other, so that the three-phase duty ratio signal actually includes six PWM control signals, and finally, six-way switching tubes of the inverter 4 are controlled according to six-way PWM control signals corresponding to the three-phase duty ratios Du, dv and Dw, so as to realize driving operation of the motor 10.
Further, as a fourth embodiment of the PFC circuit according to the present invention, based on the third embodiment of the PFC circuit according to the present invention, as shown in fig. 12, in the present embodiment, the PFC operation control unit 51 includes a weak magnetic threshold voltage Us calculation module 511, an ac voltage parameter determination module 512, a weak magnetic threshold voltage Us clipping module 513, and an inductor current value I L A calculation module 516, a PFC switching signal duty cycle calculation module 515, and a switching signal generation module 517;
the weak magnetic critical voltage value Us calculation module 511 is configured to calculate the weak magnetic critical voltage value Us when the motor is running from the Q-axis given voltage value Vq, the D-axis given voltage value Vd and the modulation factor Kmax.
The ac voltage parameter determining module 512 is configured to calculate, based on the ac input voltage value Uac collected by the ac voltage sampling portion 2, an ac input voltage polarity identification signal, an ac input voltage effective value Urms, an ac input voltage absolute value ui, and a zero-crossing detection signal, respectively, where the ac input voltage value Uac is a voltage value of a sinusoidal variation, and thus it is not difficult to obtain the parameter value by analyzing and calculating the real-time voltage value thereof in one sinusoidal period.
The weak magnetic threshold voltage value Us amplitude limiting module 513 is configured to amplitude limit the weak magnetic threshold voltage value Us to obtain a dc bus voltage given value Udref.
Inductor current setpoint I Lref A calculation module 514 for calculating the inductance current set point I according to the DC bus voltage set point Udref and the DC bus voltage value Udc Lref ；
Inductance current value I L A calculating module 516 for calculating an inductance current value I according to the dc bus current value Idc L ；
A PFC switch signal duty cycle calculation module 515 for calculating a set value I according to the inductance current Lref And an inductor current value I L Calculating to obtain a PFC switching signal duty ratio signal;
the switching signal generating module 517 is configured to calculate a switching signal according to the duty cycle signal of the PFC switching signal, the polarity identification signal of the ac input voltage, and the zero crossing signal of the ac voltage, so as to control the switching operation of the first switching tube S7 or the second switching tube S8.
Specifically, the weak magnetic threshold voltage Us clipping module 513 performs calculation based on the following formula (11):
where Vd is a D-axis given voltage value, vq is a Q-axis given voltage value, and these two parameters are calculated by the current control module 524 of the motor operation control section 52 in the above-described third embodiment based on the formula (7), kmax is a modulation factor, that is, a ratio of the maximum output voltage of the inverter to the bus voltage. If the case of linear modulation is considered, then
Further, the weak magnetic threshold value Us clipping module 513 clips the weak magnetic threshold value Us [ U ] dc_min ,U dc_max ]Obtaining a command value Udref of the DC bus voltage, wherein U is as follows dc_min Based on input voltage determination, generally taking U dc_min ＝U ac_max +U 0 ,U ac_max At the maximum of alternating voltage, U 0 For constant, 5V-10V is recommended. U (U) dc_max According to the systemWithstand voltage and keep a certain margin to confirm, U dc_max ＝U rate -U 1 ,U rate For the device withstand voltage, the IPM module withstand voltage used in this embodiment may be 500V, i.e. U rate ＝500V，U 1 To maintain the withstand voltage margin, 50V-100V is recommended, U in this embodiment 1 Can be 100V.
Further, the inductance current is given value I Lref The calculation module 514 calculates the inductor current given value I Lref When the method is used, the given value Udref of the DC bus voltage and the voltage value Udc of the DC bus are firstly subjected to difference, PI control is carried out, the absolute value of the power supply voltage is multiplied by the absolute value of the power supply voltage, and then the power supply voltage is multiplied by the inverse 1/U of the square of the effective value of the power supply voltage 2 rms, obtain instruction value I of inductance current Lref 。
Further, the inductor current value I L The calculation module 516 calculates the inductor current value I L When the DC bus current value Idc is calculated, an inductance current value I is obtained L In the second embodiment, it can be seen that the dc bus current Idc is the inductance current I through the reactor L during the closing period of the first switching tube S7 or the second switching tube S8 L Therefore, the inductance current value I can be represented by the DC bus current value Idc L 。
Further, when the duty ratio calculation module 515 calculates the duty ratio signal of the PFC switching signal, the duty ratio signal of the PFC switching signal is calculated according to the given value I of the inductor current Lref And the actual value of the inductor current I L And performing difference making, and performing PI control to obtain the duty ratio D of the PFC switch signal.
Further, the switching signal generating module 517 finally determines a PWM control signal for switching the first switching tube S7 or the second switching tube S8 according to the PFC switching signal duty ratio signal D, the ac input voltage polarity identification signal, and the ac voltage zero crossing signal, so as to control the PFC circuit to operate.
In the process of calculating and generating the switching signal for controlling the switching tube to work, the PFC operation control unit 51 of the present embodiment introduces the real-time parameter in the process of controlling the motor 10 in the transportation control process because the motor operation control unit 51 calculates and generates the PWM control signal for controlling the inverter to finally obtain the relevant parameters of the motor 10 operation, such as the Q-axis given voltage value Vq and the D-axis given voltage value Vd, so that the control of the PFC circuit can monitor the load condition of the motor 10 in real time to change, thereby the control is more accurate.
The invention also provides a motor control system which can be used for driving the permanent magnet synchronous motor to operate and can be applied to household appliances such as an air conditioner or a washing machine for sampling the operation of the permanent magnet synchronous motor.
The invention also provides a variable frequency air conditioner, which comprises an indoor unit part and an outdoor unit part, wherein the outdoor unit controller and/or the indoor unit controller can comprise the motor control system disclosed by the embodiment of the invention so as to control the indoor fan or the outdoor compressor to run, and the reliability of the whole variable frequency air conditioner can be effectively improved.
In the description of the present specification, the descriptions of the terms "first embodiment," "second embodiment," "example," and the like, mean that a particular method, apparatus, or feature described in connection with the embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms are not necessarily directed to the same embodiment or example. Furthermore, the particular features, methods, apparatus, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples. Furthermore, the different embodiments or examples described in this specification and the features of the different embodiments or examples may be combined and combined by those skilled in the art without contradiction.
The foregoing description is only of the preferred embodiments of the present invention, and is not intended to limit the scope of the invention, but rather is intended to cover any equivalents of the structures or equivalent processes disclosed herein or in the alternative, which may be employed directly or indirectly in other related arts.

Claims (11)

1. The PFC circuit is applied to a motor control system and is characterized by comprising a reactor, a rectifying part, a current detection part, a filter circuit, an alternating current voltage sampling part, a direct current voltage sampling part and an operation control part; the reactor is connected with the input end of the alternating current power supply, and the reactor and the rectifying part are connected in series in an alternating current power supply loop; the output end of the rectifying part is connected with a direct current bus, and the filter circuit is connected with the rectifying part through the direct current bus; the current detection part is connected in series with the direct current bus;
the rectifying part comprises a first diode, a second diode, a first switching tube and a second switching tube with freewheeling diodes, wherein a public connection point of the first diode and the second diode after being connected in series is connected with an L line of an alternating current power supply; the public connection point of the first switching tube and the second switching tube which are connected in series is connected with an N line of an alternating current power supply; one end of the first switching tube and one end of the second switching tube which are connected in series are connected with the cathode of the first diode, the other end of the first switching tube and the other end of the second switching tube which are connected in series are connected with the anode of the second diode, and the control ends of the first switching tube and the second switching tube are respectively connected with the operation control part; wherein the method comprises the steps of
The current detection part is used for detecting the current on the direct current bus and obtaining a corresponding direct current bus current value; the filter circuit is used for carrying out smooth filtering on the direct current output by the rectifying part so as to output direct current bus voltage; the alternating current voltage sampling part is used for detecting alternating current input voltage and obtaining a corresponding alternating current input voltage value; the direct-current voltage sampling part is used for detecting the direct-current bus voltage and obtaining a corresponding direct-current bus voltage value;
the operation control part comprises a PFC operation control part, wherein the PFC operation control part is used for obtaining a DC bus voltage given value of motor operation and generating PFC switch duty ratio signals according to the AC input voltage value, the DC bus current value and the DC bus voltage given value to drive a switching tube of the rectifying part to work so as to correct power factors of the input AC.
2. The PFC circuit according to claim 1, wherein the current detection section is connected in series between the rectification section and the filter circuit, and a current value through the reactor is determined by detecting the dc bus current.
3. The PFC circuit of claim 2 wherein the current detection section performs current sampling at an intermediate time when the first switching tube or the second switching tube is turned off.
4. The PFC circuit of claim 1 wherein the motor control system includes a phase current sampling section and an inverter;
the phase current sampling part is used for sampling a phase current signal of the motor and inputting the phase current signal to the operation control part;
the input end of the inverter is connected with the direct current bus, and the output end of the inverter is connected with the motor;
the operation control part also comprises a motor operation control part, wherein the motor operation control part is used for calculating and generating a pulse width signal according to the direct current bus voltage value, the phase current signal of the motor and the target rotating speed value of the motor, and also generating a triangular carrier signal and generating a PWM control signal to the inverter according to the triangular carrier signal and the pulse width signal so as to drive the motor to operate.
5. The PFC circuit according to claim 4, wherein the motor operation control section includes:
a position/speed estimation module for estimating a rotor position of the motor to obtain a rotor angle estimate and a motor speed estimate of the motor;
The Q-axis given current value calculation module is used for calculating a Q-axis given current value according to the motor target rotating speed value and the motor speed estimated value;
the D-axis given current value calculation module is used for calculating a D-axis given current value according to the maximum output voltage of the inverter and the output voltage amplitude of the inverter;
the current control module is used for calculating and generating the pulse width signal according to the Q-axis given current value, the D-axis given current value, the motor speed estimated value, the direct current bus voltage value and the phase current value sampled by the motor, and generating the PWM control signal to the inverter according to the triangular carrier signal and the pulse width signal so as to drive the motor to run.
6. The PFC circuit of claim 5 wherein the D-axis given current value calculation module comprises:
the weak magnetic controller is used for calculating the maximum output voltage of the inverter and the output voltage amplitude of the inverter to obtain an initial value of a D-axis given current value;
and the amplitude limiting unit is used for carrying out amplitude limiting processing on the initial value of the D-axis given current value to obtain the D-axis given current value.
7. The PFC circuit of claim 5 wherein the current control module further comprises:
And the Q-axis current value and D-axis current value calculation unit is used for calculating according to the phase current value and the angle estimation value to obtain the Q-axis current value and the D-axis current value.
8. The PFC circuit of claim 5 wherein the current control module is further configured to:
the phase current value of the motor operation is obtained, a first Q-axis inductance value, a second Q-axis inductance value, a first D-axis inductance value and a second D-axis inductance value which correspond to the pre-stored first phase current value and second phase current value are respectively obtained, and the Q-axis inductance value and the D-axis inductance value are calculated according to the phase current value, the first phase current value, the second phase current value, the first Q-axis inductance value, the second Q-axis inductance value, the first D-axis inductance value and the second D-axis inductance value.
9. The PFC circuit according to any one of claims 5 to 8, wherein the PFC operation control section includes a weak magnetic threshold voltage value calculation module, an ac voltage parameter determination module, a weak magnetic threshold voltage value limiter module, an inductor current set point calculation module, an inductor current value calculation module, a PFC switching signal duty ratio calculation module, and a switching signal generation module; wherein the method comprises the steps of
The weak magnetic critical voltage value calculation module is used for calculating the weak magnetic critical voltage value when the motor operates according to the Q-axis given voltage value, the D-axis given voltage value and the modulation coefficient Kmax;
the alternating current voltage parameter determining module is used for calculating according to the alternating current input voltage value acquired by the alternating current voltage sampling part to respectively obtain an alternating current input voltage polarity identification signal, an alternating current input voltage effective value, an alternating current input voltage absolute value and a zero crossing detection signal;
the weak magnetic critical voltage value amplitude limiting module is used for limiting the weak magnetic critical voltage value to obtain the given value of the DC bus voltage;
the inductance current given value calculation module is used for calculating according to the direct current bus voltage given value and the direct current bus voltage value to obtain the inductance current given value;
the inductance current value calculation module is used for calculating the inductance current value according to the direct current bus current value;
the PFC switch signal duty ratio calculation module is used for calculating and obtaining a PFC switch signal duty ratio signal according to the inductance current given value and the inductance current value;
the switching signal generation module is used for calculating a switching signal according to the PFC switching signal duty ratio signal, the alternating current input voltage polarity indication signal and the alternating current voltage zero crossing signal so as to control the first switching tube or the second switching tube to work.
10. A motor control system comprising a PFC circuit according to any of claims 1 to 9.
11. A variable frequency air conditioner comprising the motor control system according to claim 10.
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