CN111628659A - Compressor variable frequency speed regulating system and control method of direct current bus voltage - Google Patents
Compressor variable frequency speed regulating system and control method of direct current bus voltage Download PDFInfo
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- CN111628659A CN111628659A CN202010506070.XA CN202010506070A CN111628659A CN 111628659 A CN111628659 A CN 111628659A CN 202010506070 A CN202010506070 A CN 202010506070A CN 111628659 A CN111628659 A CN 111628659A
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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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02J—CIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
- H02J3/00—Circuit arrangements for ac mains or ac distribution networks
- H02J3/01—Arrangements for reducing harmonics or ripples
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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
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M5/4585—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only having a rectifier with controlled elements
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- 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
- H02P25/00—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details
- H02P25/02—Arrangements or methods for the control of AC motors characterised by the kind of AC motor or by structural details characterised by the kind of motor
- H02P25/022—Synchronous motors
- H02P25/024—Synchronous motors controlled by supply frequency
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- 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
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- 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
- Y02E—REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION
- Y02E40/00—Technologies for an efficient electrical power generation, transmission or distribution
- Y02E40/40—Arrangements for reducing harmonics
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Control Of Ac Motors In General (AREA)
Abstract
The invention provides a compressor variable frequency speed control system and a control method of direct current bus voltage, which comprises the following steps: the rectifier module converts the alternating-current input voltage into direct-current bus voltage; the inverter module is used for converting the DC bus voltage into a motor driving voltage; a motor driven by a motor driving voltage; the control module is used for adjusting the direct-current bus voltage output by the rectifying module; and when the voltage of the direct current bus is lower than the maximum value of the voltage of the direct current bus, outputting the voltage of the direct current bus according to the alternating current input voltage and the rotating speed of the motor. The invention greatly reduces the low-order harmonic wave of the power grid, improves the system efficiency, and the variable frequency speed control system is in the highest-efficiency working mode.
Description
Technical Field
The invention relates to the field of frequency conversion, in particular to a compressor frequency conversion speed regulation system and a control method of direct current bus voltage.
Background
In the existing variable frequency speed control system of the compressor, a three-phase alternating current Power supply is generally adopted for supplying Power on an application occasion with Power of more than 8kW, an uncontrolled rectifier bridge is adopted for rectification at a front stage, and an IPM Module (Intelligent Power Module) is adopted for three-phase inversion at a rear stage to provide alternating current input for a motor, as shown in fig. 1. The system has the disadvantages that firstly, diodes in the rectifier bridge belong to uncontrollable devices, and a large amount of low-order harmonic current can be injected into a power grid when the system works; secondly, the direct current bus voltage is uncontrollable, and the fluctuation of the bus voltage is increased along with the increase of the load power.
Back electromotive voltage E of the permanent magnet synchronous motor is ke, wherein ke is a motor back electromotive constant, and the motor is fixed when leaving a factory; and n is the actual rotating speed of the motor. It follows that the back emf voltage E of the motor is directly proportional to the actual rotational speed n of the motor. When the actual rotating speed n is increased to a certain value, the back electromotive force voltage E of the motor is increased to exceed the maximum output voltage of the inverter, and at the moment, if the rotating speed is increased again, the stator magnetic field can be controlled to generate a certain component in the direction of the rotor magnetic field, and the direction of the component is opposite to the direction of the rotor magnetic field, so that the effect of offsetting the rotor magnetic field to a certain extent, namely weak magnetic speed increase, is achieved. When the field weakening is accelerated, the exciting current for field weakening only does useless work, so that the loss of the motor is increased, and the efficiency of the motor is lowered.
Therefore, how to reduce the low-order harmonic of the power grid and improve the efficiency of the variable frequency speed control system becomes one of the problems to be solved urgently by the technical personnel in the field.
Disclosure of Invention
In view of the above disadvantages of the prior art, an object of the present invention is to provide a variable frequency speed control system for a compressor and a method for controlling dc bus voltage, which are used to solve the problems of large low order harmonic of a power grid and low system efficiency in the prior art.
In order to achieve the above and other related objects, the present invention provides a method for controlling dc bus voltage in a variable frequency speed control system of a compressor, where the method for controlling dc bus voltage in a variable frequency speed control system of a compressor at least includes:
and when the voltage of the direct current bus is lower than the maximum value of the voltage of the direct current bus, outputting the voltage of the direct current bus according to the alternating current input voltage and the rotating speed of the motor.
Optionally, setting the first dc bus voltage higher than a peak value of the actual ac input voltage when the actual ac input voltage fluctuates within a preset proportional range of the rated ac input voltage;
obtaining a motor counter electromotive force according to the motor rotating speed, and setting the voltage of a second direct current bus to be higher than the motor counter electromotive force;
and if the second direct current bus voltage is greater than the first direct current bus voltage, setting the direct current bus voltage as the value of the second direct current bus voltage, otherwise, setting the direct current bus voltage as the value of the first direct current bus voltage.
More optionally, the motor rotation speed and the motor back electromotive force satisfy the following relationship:
E1＝ke*n1
wherein E1 is the motor back electromotive force; ke is a counter potential constant of the motor; n1 is the motor speed.
Optionally, when the actual ac input voltage fluctuates outside the preset proportional range of the rated ac input voltage, the power switching tube in the rectifier module is turned off, and a fault signal is output.
Optionally, when the dc bus voltage reaches the maximum dc bus voltage, entering a field weakening boost mode.
Optionally, the maximum value Vbus _ max of the dc bus voltage is Vce × k, where Vce is a maximum rated value of the power switching tube, k is a safety factor, and k is 0.6 to 0.8.
In order to achieve the above objects and other related objects, the present invention further provides a variable frequency speed control system for a compressor, which performs the method for controlling the dc bus voltage in the variable frequency speed control system for a compressor, wherein the variable frequency speed control system for a compressor at least comprises:
the rectifier module receives an alternating current input voltage and converts the alternating current input voltage into a direct current bus voltage;
the inversion module is connected with the output end of the rectification module and converts the direct-current bus voltage into motor driving voltage;
the motor is connected to the output end of the inversion module and is driven to operate by the driving voltage of the motor;
and the control module is connected with the motor, the rectifying module and the inversion module and is used for generating control signals of the rectifying module and the inversion module.
Optionally, the rectifier module is an active rectifier module; or the rectifying module comprises a passive rectifying unit and a boosting unit, and the boosting unit is connected to the output end of the passive rectifying unit.
More optionally, the active rectifier module is a VIENNA rectifier module.
More optionally, the VIENNA rectifying module includes six diodes, three inductors, six power switching tubes, and two sets of capacitors; the diodes are connected in parallel after being connected in series in the same direction, the connecting nodes of the first group of diodes in series are connected with the first phase of the alternating current input voltage through a first inductor, the connecting nodes of the second group of diodes in series are connected with the second phase of the alternating current input voltage through a second inductor, and the connecting nodes of the third group of diodes in series are connected with the third phase of the alternating current input voltage through a third inductor; two groups of capacitors are connected in series and then are connected in parallel with each group of series-connected diodes; and each power switch tube is connected in series in a pairwise reverse direction and then is respectively connected between the connection node of each group of series diode and the connection node of the two groups of capacitors.
As described above, the compressor variable frequency speed control system and the control method of the dc bus voltage of the present invention have the following beneficial effects:
1. the front stage of the variable frequency speed control system of the compressor adopts the active rectifier module, so that the low-order harmonic of a power grid is greatly reduced.
2. The compressor variable frequency speed control system and the control method of the direct current bus voltage set the direct current bus voltage according to the motor rotating speed and the alternating current input voltage, and postpone the permanent magnet motor to enter a weak magnetic area, so that the variable frequency speed control system and the controlled permanent magnet synchronous motor are in the highest-efficiency working mode.
Drawings
Fig. 1 is a schematic structural diagram of a compressor variable-frequency speed control system in the prior art.
Fig. 2 is a schematic structural diagram of the compressor variable frequency speed control system of the present invention.
Description of the element reference numerals
1 compressor variable frequency speed control system
11 rectification module
12 inversion module
13 electric machine
14 control module
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention.
Please refer to fig. 2. It should be noted that the drawings provided in the present embodiment are only for illustrating the basic idea of the present invention, and the components related to the present invention are only shown in the drawings rather than drawn according to the number, shape and size of the components in actual implementation, and the type, quantity and proportion of the components in actual implementation may be changed freely, and the layout of the components may be more complicated.
Example one
The embodiment provides a method for controlling direct-current bus voltage in a compressor variable-frequency speed control system, which comprises the following steps:
and when the direct current bus voltage Vbus is lower than the maximum direct current bus voltage Vbus _ max, outputting the direct current bus voltage according to the alternating current input voltage and the motor rotating speed.
In this embodiment, the method for controlling the dc bus voltage in the compressor variable frequency speed control system specifically includes the following steps:
1. when the direct-current bus voltage is lower than the maximum value Vbus _ max of the direct-current bus voltage, considering the influence of the power grid, and further setting the direct-current bus voltage based on the fluctuation range of the actual alternating-current input voltage (through closed-loop control, the actual voltage of the direct-current bus always tracks the preset voltage of the direct-current bus).
It should be noted that the maximum value Vbus _ max of the dc bus voltage satisfies the following relation:
Vbus_max＝Vce*k
vce is the maximum rated value of the power switching tube, k is a safety factor, and k is 0.6-0.8. As an example, the maximum value Vbus _ max of the dc bus voltage is set to 1200 (maximum rating of the power switching tube, i.e., power switching tube withstand voltage) × 0.6 (safety factor) ═ 720V. In practical use, the maximum value Vbus _ max of the dc bus voltage may be set based on actual needs, which is not limited to this embodiment.
Specifically, when the actual ac input voltage Vgrid fluctuates within a preset proportion range of the rated ac input voltage Vra (in this embodiment, the preset proportion range is set to be 80% to 120%, and the preset proportion range may be set as needed in actual use, which is not limited by this embodiment), the first dc bus voltage Vbus _1 is set to be higher than the peak value of the actual ac input voltage Vgrid. In this embodiment, if the actual ac input voltage Vgrid is set to 380V, the first dc bus voltage Vbus _1 satisfies the following relation:
Vbus_1＝Vgrid*1.414*1.01＝380*1.414*1.01＝543V
it should be noted that the value of the rated ac input voltage Vra may be set according to actual conditions, and different countries or regions may have different values, for example, the three-phase line voltage of the power grid power supply in china is 380V, which is not described herein in detail. In this embodiment, the first dc bus voltage Vbus _1 is set to 101% of the peak value of the actual ac input voltage Vgrid, and in actual use, the proportional relationship between the first dc bus voltage Vbus _1 and the peak value of the actual ac input voltage Vgrid may be set as needed, and may be set to 100% to 105% (excluding the endpoint 100%, including the endpoint 105%) as an example, without being limited by this embodiment.
Specifically, according to the motor speed n1 (through closed-loop control, the actual motor speed always tracks the preset motor speed, and the motor speed n1 can be obtained through the preset motor speed or through detection of the actual motor speed), the motor counter potential E1(E1 is a counter potential voltage peak value) is obtained, and the second direct-current bus voltage Vbus _2 is set to be higher than the motor counter potential E1. The motor speed n1 and the motor counter-potential E1 satisfy the following relation: e1 is ke n1, ke is the motor back electromotive constant. In this embodiment, the second dc bus voltage Vbus _2 ═ E1 × 1.01.
Note that the motor back electromotive force constant ke is a value fixed at the time of factory shipment. In this embodiment, the second dc bus voltage Vbus _2 is set to 101% of the motor back-emf E1, and in actual use, the proportional relationship between the second dc bus voltage Vbus _2 and the motor back-emf E1 may be set as required, and may be set to 100% to 105% (excluding the endpoint 100%, including the endpoint 105%) as an example, without being limited by this embodiment.
Specifically, if the second dc bus voltage Vbus _2 is greater than the first dc bus voltage Vbus _1, the dc bus voltage Vbus is set to the value of the second dc bus voltage Vbus _2, that is, Vbus is Vbus _ 2; otherwise, the dc bus voltage Vbus is set to the value of the first dc bus voltage Vbus _1, i.e. Vbus ═ Vbus _ 1.
Specifically, when the actual ac input voltage Vgrid fluctuates outside the preset proportional range of the rated ac input voltage Vra (i.e., is less than 80% of the rated ac input voltage Vra or greater than 120% of the rated ac input voltage Vra in this embodiment), the power switch in the rectifier module is turned off, that is, the control module in the system does not output the PWM driving signal, and outputs the fault signal. At the moment, the inversion side can carry out load reduction operation or soft shutdown. The fault signal includes, but is not limited to, an under-voltage protection signal and an over-voltage protection signal, which are not described herein in detail.
In another embodiment of the present invention, when the dc bus voltage Vbus reaches the maximum dc bus voltage Vbus _ max, if it is desired to continue increasing the motor speed at this time, the motor flux can be weakened only by changing the excitation current, that is, the motor enters the field weakening boost mode.
The active rectification module is adopted in the embodiment, so that the low-order harmonic of a power grid is greatly reduced; before the DC bus voltage reaches the maximum value, the DC bus voltage is set according to the preset rotating speed of the motor and the AC input voltage, and the DC bus voltage, namely the maximum output voltage of the inverter, is ensured to be larger than the back electromotive voltage of the motor, so that the motor is delayed to enter a weak magnetic region, and the overall efficiency of the variable frequency speed control system in a full speed range is improved.
Example two
As shown in fig. 2, the present embodiment provides a variable frequency speed control system 1 for a compressor, where the variable frequency speed control system 1 for a compressor includes:
the device comprises a rectification module 11, an inversion module 12, a motor 13 and a control module 14.
As shown in fig. 2, the rectifier module 11 receives an ac input voltage and converts the ac input voltage into a dc bus voltage Vbus.
Specifically, in this embodiment, the rectifier module 11 is a VIENNA rectifier module in an active rectifier module, and various modifications of VIENNA topology are applicable to the rectifier module 11 of the present invention. As an example, the rectifier module 11 includes six diodes, three inductors, six power switching tubes, and two sets of capacitors (two sets of capacitors may be a single capacitor or a combination of multiple capacitors connected in series and parallel), and the capacitance values of the two sets of capacitors are the same. Every two diodes are connected in series in the same direction and then connected in parallel, namely: the cathode of the first diode D1 is connected with the positive pole Vbus + of the direct current bus voltage, and the anode is connected with the cathode of the second diode D2; the anode of the second diode D2 is connected with the cathode Vbus-of the direct current bus voltage; the cathode of the third diode D3 is connected to the positive pole Vbus + of the dc bus voltage, and the anode is connected to the cathode of the fourth diode D4; the anode of the fourth diode D4 is connected with the negative pole Vbus-of the direct current bus voltage; the cathode of the fifth diode D5 is connected to the positive electrode Vbus + of the dc bus voltage, and the anode is connected to the cathode of the sixth diode D6; the anode of the sixth diode D6 is connected to the negative pole Vbus-of the dc bus voltage V. A connection node of the first diode D1 and the second diode D2 is connected to the first phase L1 of the ac input voltage, a connection node of the third diode D3 and the fourth diode D4 is connected to the second phase L2 of the ac input voltage, and a connection node of the fifth diode D5 and the sixth diode D6 is connected to the third phase L3 of the ac input voltage. Each phase of the ac input voltage is input through an inductor (the first inductor L11, the second inductor L12, and the third inductor L13). The first capacitor C1 and the second capacitor C2 are connected in series and then connected between the positive pole Vbus + and the negative pole Vbus-of the DC bus voltage. Each power switch tube is connected between the connection node of each group of series diode and the connection node of two groups of capacitors after being connected in series in a pairwise reverse direction, namely: the collector of the first power switch tube Q11 is connected with the connection node of the first diode D1 and the second diode D2, and the emitter is connected with the emitter of the second power switch tube Q12; the collector of the second power switch Q12 is connected with the connection node of the first group capacitor C1 and the second group capacitor C2; the collector of the third power switch Q13 is connected to the connection node of the third diode D3 and the fourth diode D4, and the emitter is connected to the emitter of the fourth power switch Q14; the collector of the fourth power switch Q14 is connected with the connection node of the first group capacitor C1 and the second group capacitor C2; the collector of the fifth power switch Q15 is connected to the connection node of the fifth diode D5 and the sixth diode D6, and the emitter is connected to the emitter of the sixth power switch Q16; the collector of the sixth power switch Q16 is connected to the node connecting the first capacitor C1 and the second capacitor C2. Each power switch tube in the rectifier module 11 is connected with a control signal.
It should be noted that the power supply of the power grid in this embodiment is a three-phase four-wire system (three live wires and one ground wire), and if the power supply is a three-phase five-wire system (three live wires and one neutral wire and one ground wire), the neutral wire is connected to the connection node of the two sets of capacitors.
In this embodiment, each power switch tube is an insulated gate bipolar transistor, and the type of each power switch tube may be set as needed in actual use. The rectifier module 11 may be any controllable active rectifier module; the power supply also comprises a passive rectifying unit and a boosting unit, wherein the boosting unit is connected to the output end of the passive rectifying unit; therefore, the controllable rectification is realized, and the present embodiment is not limited.
As shown in fig. 2, the inverter module 12 is connected to the output end of the rectifier module 11, and converts the dc bus voltage Vbus into a motor driving voltage.
Specifically, in this embodiment, the inverter module 12 includes six power switching tubes, which form a three-phase inverter bridge, wherein a seventh power switching tube Q21 and an eighth power switching tube Q22 are connected in series between a positive electrode Vbus + of the dc bus voltage and a negative electrode Vbus-of the dc bus voltage (a collector of the seventh power switching tube Q21 is connected to the positive electrode Vbus + of the dc bus voltage, an emitter of the seventh power switching tube Q21 is connected to the collector of the eighth power switching tube Q22, and an emitter of the eighth power switching tube Q22 is connected to the negative electrode Vbus-of the dc bus voltage); a ninth power switch Q23 and a tenth power switch Q24 are connected in series between the positive pole Vbus + of the dc bus voltage and the negative pole Vbus-of the dc bus voltage (the connection port is the same as the seventh power switch Q21 and the eighth power switch Q22, which is not described herein again); an eleventh power switch Q25 and a twelfth power switch Q26 are connected in series between the positive pole Vbus + of the dc bus voltage and the negative pole Vbus-of the dc bus voltage (the connection port is the same as the seventh power switch Q21 and the eighth power switch Q22, which is not described herein again); each power switch tube in the inverter module 12 is connected with a control signal.
In this embodiment, each power switch in the inverter module 12 is an insulated gate bipolar transistor, and the type of each power switch may be set as needed in actual use. The inverter module 12 may select any one of the structures according to the requirement, and is not limited to this embodiment.
As shown in fig. 2, the motor 13 is connected to an output end of the inverter module 12 and driven by the motor driving voltage to operate.
Specifically, in this embodiment, the motor 13 is a permanent magnet synchronous motor, and when three-phase ac power is supplied to a three-phase stator winding of the motor, a rotating magnetic field is generated, and the rotating magnetic field drives the rotor to rotate synchronously. In other embodiments, the motor 13 may also be an ac asynchronous motor or other three-phase motors, which are not described herein.
As shown in fig. 2, the control module 14 is connected to the motor 13, the rectifier module 11 and the inverter module 12, and generates control signals for the rectifier module 11 and the inverter module 12.
Specifically, in this embodiment, the control module 14 collects an ac input voltage and a signal on the motor 13, and controls the rectification module 11 and the inverter module 12 to execute the control method of the dc bus voltage in the variable frequency speed control system of the compressor according to the first embodiment or the second embodiment to realize the speed regulation of the motor 13, and the working principle refers to the first embodiment and the second embodiment, which is not repeated herein.
The compressor variable frequency speed control system of the embodiment greatly reduces low-order harmonic waves of a power grid, improves system efficiency, is always in a highest-efficiency working mode (including a controlled motor), and is suitable for industrial application.
In summary, the present invention provides a variable frequency speed control system for a compressor and a method for controlling dc bus voltage, including: the rectifier module receives an alternating current input voltage and converts the alternating current input voltage into a direct current bus voltage; the inversion module is connected with the output end of the rectification module and converts the direct-current bus voltage into motor driving voltage; the motor is connected to the output end of the inversion module and is driven to operate by the driving voltage of the motor; the control module is connected with the motor, the rectifying module and the inverting module and used for generating control signals of the rectifying module and the inverting module; and when the voltage of the direct current bus is lower than the maximum value of the voltage of the direct current bus, outputting the voltage of the direct current bus according to the alternating current input voltage and the rotating speed of the motor. The front stage of the variable frequency speed control system of the compressor adopts the active rectifier module, so that the low-order harmonic of a power grid is greatly reduced; and setting the direct-current bus voltage according to the rotating speed of the motor and the alternating-current input voltage, and delaying the permanent magnet motor from entering a weak magnetic region, so that the variable-frequency speed control system and the controlled permanent magnet synchronous motor are in a working mode with the highest efficiency. Therefore, the invention effectively overcomes various defects in the prior art and has high industrial utilization value.
The foregoing embodiments are merely illustrative of the principles and utilities of the present invention and are not intended to limit the invention. Any person skilled in the art can modify or change the above-mentioned embodiments without departing from the spirit and scope of the present invention. Accordingly, it is intended that all equivalent modifications or changes which can be made by those skilled in the art without departing from the spirit and technical spirit of the present invention be covered by the claims of the present invention.
Claims (10)
1. A control method for DC bus voltage in a compressor variable frequency speed control system is characterized in that the control method for DC bus voltage in the compressor variable frequency speed control system at least comprises the following steps:
and when the voltage of the direct current bus is lower than the maximum value of the voltage of the direct current bus, outputting the voltage of the direct current bus according to the alternating current input voltage and the rotating speed of the motor.
2. The method for controlling the direct-current bus voltage in the variable-frequency speed regulating system of the compressor according to claim 1, wherein the method comprises the following steps:
when the actual alternating current input voltage fluctuates within a preset proportion range of the rated alternating current input voltage, setting the voltage of the first direct current bus to be higher than the peak value of the actual alternating current input voltage;
obtaining a motor counter electromotive force according to the motor rotating speed, and setting the voltage of a second direct current bus to be higher than the motor counter electromotive force;
and if the second direct current bus voltage is greater than the first direct current bus voltage, setting the direct current bus voltage as the value of the second direct current bus voltage, otherwise, setting the direct current bus voltage as the value of the first direct current bus voltage.
3. The method for controlling the direct-current bus voltage in the variable-frequency speed regulating system of the compressor according to claim 2, wherein the method comprises the following steps: the motor rotating speed and the motor back electromotive force satisfy the following relation:
E1＝ke*n1，
wherein E1 is the motor back electromotive force; ke is a counter potential constant of the motor; n1 is the motor speed.
4. The method for controlling the direct-current bus voltage in the variable-frequency speed regulating system of the compressor according to claim 1, wherein the method comprises the following steps: and when the actual alternating current input voltage fluctuates outside the preset proportion range of the rated alternating current input voltage, a power switch tube in the rectification module is turned off, and a fault signal is output.
5. The method for controlling the direct-current bus voltage in the variable-frequency speed regulating system of the compressor according to claim 1, wherein the method comprises the following steps: and when the direct current bus voltage reaches the maximum value of the direct current bus voltage, entering a weak magnetic speed increasing mode.
6. The method for controlling the direct-current bus voltage in the variable-frequency speed regulating system of the compressor according to claim 1, wherein the method comprises the following steps: the maximum value Vbus _ max of the direct current bus voltage is Vce k, wherein Vce is the maximum rated value of the power switching tube, k is a safety factor, and k is 0.6-0.8.
7. A compressor variable frequency speed control system for executing the method for controlling the DC bus voltage in the compressor variable frequency speed control system according to any one of claims 1 to 6, wherein the compressor variable frequency speed control system at least comprises:
the rectifier module receives an alternating current input voltage and converts the alternating current input voltage into a direct current bus voltage;
the inversion module is connected with the output end of the rectification module and converts the direct-current bus voltage into motor driving voltage;
the motor is connected to the output end of the inversion module and is driven to operate by the driving voltage of the motor;
and the control module is connected with the motor, the rectifying module and the inversion module and is used for generating control signals of the rectifying module and the inversion module.
8. The variable frequency speed control system of the compressor of claim 7, wherein: the rectifying module is an active rectifying module; or the rectifying module comprises a passive rectifying unit and a boosting unit, and the boosting unit is connected to the output end of the passive rectifying unit.
9. The variable frequency speed control system of the compressor of claim 8, wherein: the active rectifier module is a VIENNA rectifier module.
10. The variable frequency speed control system of the compressor of claim 9, wherein: the VIENNA rectifying module comprises six diodes, three inductors, six power switch tubes and two groups of capacitors; the diodes are connected in parallel after being connected in series in the same direction, the connecting nodes of the first group of diodes in series are connected with the first phase of the alternating current input voltage through a first inductor, the connecting nodes of the second group of diodes in series are connected with the second phase of the alternating current input voltage through a second inductor, and the connecting nodes of the third group of diodes in series are connected with the third phase of the alternating current input voltage through a third inductor; two groups of capacitors are connected in series and then are connected in parallel with each group of series-connected diodes; and each power switch tube is connected in series in a pairwise reverse direction and then is respectively connected between the connection node of each group of series diode and the connection node of the two groups of capacitors.
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| WO2023202072A1 (en) * | 2022-04-22 | 2023-10-26 | 青岛海尔空调器有限总公司 | Method and apparatus for controlling compressor, and air conditioner and storage medium |
| CN118264175A (en) * | 2024-05-30 | 2024-06-28 | 深圳市新能安华技术有限公司 | Low-harmonic inverter circuit, control method, compressor driving device and air conditioning equipment |
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