CN108471244A - A kind of frequency-changeable compressor reduces the compensation circuit and its control method of leakage current - Google Patents
A kind of frequency-changeable compressor reduces the compensation circuit and its control method of leakage current Download PDFInfo
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- CN108471244A CN108471244A CN201810614695.0A CN201810614695A CN108471244A CN 108471244 A CN108471244 A CN 108471244A CN 201810614695 A CN201810614695 A CN 201810614695A CN 108471244 A CN108471244 A CN 108471244A
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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
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B35/00—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for
- F04B35/04—Piston pumps specially adapted for elastic fluids and characterised by the driving means to their working members, or by combination with, or adaptation to, specific driving engines or motors, not otherwise provided for the means being electric
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B13/00—Compression machines, plants or systems, with reversible cycle
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B49/00—Arrangement or mounting of control or safety devices
- F25B49/02—Arrangement or mounting of control or safety devices for compression type machines, plants or systems
- F25B49/022—Compressor control arrangements
-
- 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
- H02M1/12—Arrangements for reducing harmonics from ac input or output
-
- 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
- H02M1/44—Circuits or arrangements for compensating for electromagnetic interference in converters or inverters
-
- 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
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25B—REFRIGERATION MACHINES, PLANTS OR SYSTEMS; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS
- F25B2600/00—Control issues
- F25B2600/02—Compressor control
- F25B2600/021—Inverters therefor
-
- 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
- H02M1/12—Arrangements for reducing harmonics from ac input or output
- H02M1/123—Suppression of common mode voltage or current
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- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Thermal Sciences (AREA)
- Electromagnetism (AREA)
- Control Of Ac Motors In General (AREA)
Abstract
The invention belongs to Compressor Technology fields, a kind of compensation circuit of frequency-changeable compressor reduction leakage current is provided, it is characterized in that, compensating electric capacity one end of the compensation circuit is grounded, the other end is connected to by a switch element respectively with AGND and busbar, and the switch element is opened and disconnected using software control；PWM variable-frequency motor dragging system medium-high frequency common-mode voltage variation rate dv/dt are calculated, when dv/dt is positive value, the compensating electric capacity of compensation circuit is connected to AGND, is disconnected with busbar, and compensating electric capacity absorbs compressor leakage electric current；When dv/dt is negative value, the compensating electric capacity of compensation circuit connects busbar, is disconnected with AGND, generates external compensation electric current, and when dv/dt is 0, the compensating electric capacity of compensation circuit is disconnected with AGND and busbar simultaneously.The present invention accurately controls compensation by being carried out to leakage current, can effectively reduce leakage current, improves the electrical safety and reliability of equipment, not complicated component, saves cost.
Description
Technical field
The invention belongs to the compensation circuits that Compressor Technology field more particularly to a kind of frequency-changeable compressor reduce leakage current
And its control method.
Background technology
Convertible frequency air-conditioner has obtained being widely recognized as market since its appearance, with its higher efficiency and electricity saving performance, and
The main product of current major air-conditioning manufacturer.But the use of frequency conversion direct current compressor PWM control technologies and high-speed switching devices, gives
More high frequency common mode interference is introduced in compressor stator winding, is leaked to greatly using the coupled capacitor between stator and shell
Ground, causes compressor leakage electric current to increase, and the leakage current of frequency-changeable compressor is generally more larger than invariable frequency compressor.Each state is all to family
The electrical safety of electrical appliance has corresponding standard, to the requirement of leakage current also finite value.
Industry is developed in frequency conversion product process, for the exceeded improvement of leakage current, three kinds of schemes of generally use：
1) structure for changing compressor direct current generator, increases the dielectric strength between motor stator and motor housing；
2) it adds passive or active low-pass filter in frequency-variable controller IPM drive module three-phase output ends and connects compressor again
Load；
3) compressor leakage regularly absorb or compensate using external leakage current compensation circuit, reach reduction
Purpose.
The first scheme is insulated by reinforcing, and barrier leakage current generates path, is the most commonly used scheme；Theory of correlation
Text, patent also have in-depth study to second scheme, it is proposed that various effective filter schemes；The third passive reduction is let out
Study less in the scheme industry of leakage current, CN107078657A proposes a kind of leakage current compensation circuit, passes through a height
The electric current of common-mode leakage current transformer the induction zero curve and firewire of precision, the direction of leakage current is judged by difference, is triggered
Compensation circuit compensates compressor leakage, while the rotor-position for obtaining compressor controls the break-make of compensation circuit
System, prevents overcompensation.But this scheme has the shortcomings that certain：High-precision transformer request is higher, and cost is also larger；Compensation electricity
The break-make on road is based on experiment experience, and compensation is inaccurate, and difficulty reaches optimum efficiency.
The present invention proposes, based on the compensation scheme of software control compensation circuit, to trigger as control without mutual inductor,
Compensation is more accurate.
Invention content
In view of existing in the prior art above-mentioned technical problem, the purpose of the present invention is to provide a kind of frequency-changeable compressor reduction to let out
The compensation circuit of leakage current, the compensation circuit using software control, for frequency-changeable compressor leakage current reduction propose it is new
Solution reduces cost of compensation.
Another object of the present invention is to provide the controlling party for the compensation circuit that the frequency-changeable compressor reduces leakage current
Method proposes the leakage current compensation scheme of software control, according to the rule according to the regularity of frequency-changeable compressor Leakage Current
Accurate compensation leakage current.
In order to reach foregoing invention purpose, present invention employs following technical solutions.
The present invention provides a kind of compensation circuit of frequency-changeable compressor reduction leakage current, the compensating electric capacity of the compensation circuit
One end is grounded, and the other end is connected to by a switch element respectively with AGND and busbar, and the switch element is controlled using software
It opens and disconnects；PWM variable-frequency motor dragging system medium-high frequency common-mode voltage variation rate dv/dt are calculated, when dv/dt is positive value,
AGND is connected in the compensating electric capacity of compensation circuit, is disconnected with busbar, and compensating electric capacity absorbs compressor leakage electric current；When dv/dt is negative
When value, the compensating electric capacity of compensation circuit connects busbar, is disconnected with AGND, generates external compensation electric current, when dv/dt is 0, mends
The compensating electric capacity for repaying circuit is disconnected with AGND and busbar simultaneously.
The software realizes that microcontroller is connect by network with switch element using microcontroller, i.e., the described switch
Element is opened and is disconnected using microcontroller control, and microcontroller connects two switch elements.
In general, the compensating electric capacity in compensation circuit is larger, and coupled capacitor parameter very little in motor, the two can not possibly reach
It is completely the same, it is susceptible to that compensation electric current is excessive to be caused leakage the case where instead increasing, to need according to compressor leakage electric current
Size selects appropriate compensation circuit current-limiting resistance Z1, limitation compensation current amplitude.Therefore, it is necessary to the ground connection in the compensating electric capacity
End connection current-limiting resistance, the size of the current-limiting resistance are determined according to actually detected leakage current size, to ensure compensation electricity
The compensation electric current that road generates is offseted with actual leakage current.
Because leaking and compensating current amplitude very little, compensation circuit is not limited to use forceful electric power that power supply occurs as compensation electric current.
When use forceful electric power PFC-DC as compensation circuit in compensation electric current occur power supply when, switch element use IGBT switching tubes；When making
When using the light current such as ± 15V that power supply occurs as compensation circuit compensation electric current, triode can be used in switch element.No matter forceful electric power is used
Or as compensation electric current power supply occurs for light current, and the control program of compensation circuit is consistent with following control methods.
Switch element in the present invention is opened and is broken according to the regularity control of frequency-changeable compressor Leakage Current using software
It opens.
In modern PWM conversion power supplies system, two level of generally use, voltage source shape, AC and DC hybrid transmission system.Pass through rectifier
It is direct current by grid side AC conversion.It is converted into stable DC by intermediate DC link filter, then by inverse
Become device by DC conversion as the alternating current of frequency, amplitude needed for load.In rectification side, using the uncontrollable rectification of diode.
Inverter side, using the conducting of space vector pulse width modulation Signal-controlled switch pipe, so that it is a series of in the output of inverter outlet side
Constant amplitude, not wide voltage signal.With the development of power electronic technique, switching tubes of the generally use IGBT as inverter side,
The rise time of switching tube generally all only has hundreds of ns.Therefore the voltage of output side transducer will produce prodigious dv/dt, can be right
Inverter load generates especially strong impact.
For in frequency-changeable compressor circuit, the electricity of three phase supply end UVW over the ground can be obtained by Kirchoff s voltage theorem
Pressure is：
The addition of three formulas can obtain：
Wherein, Uug、Uvg、UwgRespectively inverter output end voltage-to-ground；ia、ib、icRespectively inverter output end stream
Current instantaneous value through machine winding；R, L is machine winding equivalent inductance；UNgFor motor stator winding neutral point voltage-to-ground,
That is common-mode voltage.
To three-phase induction motor, the electric current that any time flows through stator winding is ia、ib、icSince stator winding is completely right
Claim, at any time,：ia+ib+ic=0, so, in inverter output terminal, can obtain：
It follows that when motor uses the Alternating Current Power Supply of traditional three-phase symmetrical, stator winding neutral point voltage is zero,
When using the space vector pulse width modulation mode of two level, is combined by the switching tube of inverter IPM upper and lower bridge arms and open, close
It is disconnected, so that output side transducer is exported a series of not wide pulse voltage of constant amplitudes to be equivalent to alternating current.At any time, they
The sum of amplitude be not zero, down tube cannot simultaneously turn at any time on same bridge arm.According to its SVPWM modulation principle, altogether
There are 8 kinds of switch combination states (by taking G2, G4, G6 open 1, shutdown 0 as an example), corresponding obtained UcomVoltage is approximately：
This portion voltage is the common-mode voltage of system medium-high frequency, they are not involved in energy transmission, but to entire electrical system
Bring negative effect.Since there are stator winding as shown in Fig. 2 inside three phase electric machine electricity is closed to casing Jian Said
Hold Cwf, stator winding to rotor Jian Said close capacitance Cwr, rotor to the coupled capacitor C between casingrfDistribution inside equal motors
Parameter, high frequency common mode voltage change ratio dv/dt form leakage current over the ground by these capacitances.
Electric system is emulated by establishing dragging system model, establishes motor coupled capacitor ginseng according to Fig.2,
In exponential model such as Fig. 1 shown in B, simulation result is as shown in figure 3, wherein IleakageFor compressor leakage electric current, UcomFor stator winding
Common-mode voltage, it can be deduced that conclusion is positive value as common-mode voltage dv/dt, also as rising edge when, compressor coil has pair
The positive leakage current on ground, when dv/dt is negative value, also as failing edge when, compressor coil has the leakage of negative sense over the ground
Electric current has certain phase rule.
Therefore, the compensation current canceling with leakage current opposite in phase can be exported by compensation circuit integrally to external leakage
Electric current.Compensating electric capacity one end of compensation circuit of the present invention is grounded, and the other end is switched by one respectively with AGND and busbar
Element is connected to.When dv/dt is positive value, AGND is connected in the compensating electric capacity of compensation circuit, and compensating electric capacity absorbs compressor leakage electricity
Stream；When dv/dt is negative value, the compensating electric capacity of compensation circuit connects busbar, generates external compensation electric current.
The present invention also provides it is a kind of suitable for above-mentioned frequency-changeable compressor reduce leakage current compensation circuit control method,
Described method includes following steps：
1) continuous acquisition i+1 groups inverter IPM outputs voltages of the UVW with respect to AGND, wherein i=0,1,2 ...；
2) common-mode voltage U is calculatedcom, the on off state being presently in is determined according to value；
If 3) Ucomi<Ucomi+1, then the switch element of connection AGND is opened, the switch element of connection busbar is disconnected；If
Ucomi>Ucomi+1, then the switch element of connection busbar is opened, the switch element of connection AGND is disconnected；If not occurring level change
Change, then remains open the switch element of AGND and busbar, wherein Ucomi、Ucomi+1For i-th group or the calculated common mode of i+1 group
Voltage.
The calculation formula of the common-mode voltage is：
Wherein, Uug、Uvg、UwgRespectively inverter output end voltage-to-ground, UNgIt is electric over the ground for motor stator winding neutral point
Pressure, i.e. common-mode voltage.
In further technical solution, in order to ensure the stability of control, increases examination step after step 2), that is, sentence
The calculated common-mode voltage U of disconnected step 2)comIn error range whether close to 0, Udc/3,2Udc/3, Udc, if it is
By UcomEqual to the theoretical value of corresponding on off state, it is stored in temporary register and obtains Ucomi、Ucomi+1, otherwise, re-start
Step 1) and 2).The theoretical value of the corresponding on off state is 0, in Udc/3,2Udc/3, Udc with calculated common-mode voltage
UcomThat most similar value.
In the above method, if Ucomi<Ucomi+1, then dv/dt>0；If Ucomi>Ucomi+1, then dv/dt<0；It is described not occur electricity
Flat variation, as Ucomi=Ucomi+1And dv/dt=0.According to the rule obtained is emulated above, when common-mode voltage dv/dt is just
Value, also as rising edge when, compressor coil has positive leakage current over the ground, is also to decline when dv/dt is negative value
Along when, compressor coil has negative sense leakage current over the ground.So, if Ucomi<Ucomi+1, also as rising edge, compressor
Coil has positive leakage current over the ground.At this point, opening the switch element of connection AGND, the switch member of connection busbar is disconnected
Part, compensation circuit can absorb the leakage current.If Ucomi>Ucomi+1, also as failing edge when, compressor coil has over the ground
Negative sense leakage current.At this point, opening the switch element of connection busbar, the switch element of connection AGND is disconnected, just will produce pair
Outer compensation electric current.If Ucomi=Ucomi+1, namely not occurring level change, compressor need not absorb or compensate electric current, only
Need to remain open the switch element of AGND and busbar.
The present invention also provides another controls for being suitable for above-mentioned frequency-changeable compressor and reducing the compensation circuit of leakage current
Method, described method includes following steps：
1) the drive signal level height for obtaining three switching tubes of SVPWM algorithms control inverter represents high electricity with 1
It is flat, represent low level with 0；
2) three on off states are added summation；
3) it is tabled look-up according to previous next state and current state and confirms current state present position, predict next state；
4) it provides moment output compensating circuit switch element in next group of inverter switching device signal and controls signal, if next
Three on off state sums of a state are more than three on off state sums of current state, then control opening connection
The switch element of AGND disconnects the switch element of connection busbar；If three on off state sums of next state are small
In three on off state sums of current state, then the switch element for opening connection busbar is controlled, disconnects connection AGND's
Switch element；If three on off state sums of next state and three on off state sums of current state
It is identical, then disconnect the switch element of AGND and busbar.
According to seven segmentation drive signal rules of SVPWM, in general, no matter being in which sector in six sectors, drive signal
The sum of (by taking G2, G4, G6 open 1, shutdown 0 as an example) conducting state is always according to the rule of (0,1,2,3,3,2,1,0,0,1 ...)
Variation.Get eve on off state and on off state this moment, you can prediction next time state change when UcomRising edge
Or failing edge situation, in state transformation next time, punctual output compensating circuit switching tube drive signal, compensates.
In from the discussion above it is found that according to its SVPWM modulation principle, shares 8 kinds of switch combination states and (opened with G2, G4, G6
Logical 1, for shutdown 0), corresponding obtained UcomVoltage is approximately：
As it can be seen that when the sum of on off state is gradually to increase, UcomVoltage also gradually increases, i.e. dv/dt is positive value；When opening
The sum of off status is U when being gradually reducedcomVoltage is gradually lowered, i.e. dv/dt is negative value；When the sum of on off state is constant,
UcomVoltage is also constant, i.e. dv/dt is 0.So, moment output compensating circuit switch is provided in next group of inverter switching device signal
Element controling signal, if three on off state sums of next state are more than three on off state phases of current state
In addition and, then the switch element for opening connection AGND is controlled, disconnects the switch element of connection busbar；If the three of next state
A on off state sum is less than three on off state sums of current state, then controls the switch for opening connection busbar
Element disconnects the switch element of connection AGND；If three on off state sums of next state and current state
Three on off state sums are identical, then disconnect the switch element of AGND and busbar.
The present invention has the advantages that：1, by carrying out accurately controlling compensation to leakage current, can effectively subtract
Few leakage current, improves the electrical safety and reliability of equipment；2, not complicated component saves cost.
Description of the drawings：
Fig. 1 is PWM conversion power supplies system and leakage current compensation circuit schematic diagram in the embodiment of the present invention；
Fig. 2 is frequency-changeable compressor coupled capacitor schematic diagram in the embodiment of the present invention；
Fig. 3 is leakage current phase rule schematic diagram in the embodiment of the present invention；
Fig. 4 is control program flow chart in the embodiment of the present invention 1；
Fig. 5 is control program flow chart in the embodiment of the present invention 2；
Wherein, 1 is stator, and 2 be permanent magnet, and 3 be rotor, and 4 be shell.
Specific implementation mode：
Illustrate technical scheme of the present invention with reference to specific embodiment.But following embodiments are only skills of the present invention
It is several rather than all in art scheme, following embodiments should not be interpreted as to the limitation to technical solution of the present invention.
Embodiment 1
With reference to figure 1, the present embodiment is that (PFC is a kind of common variable-frequency motor dragging system A of PWM modulation with Boost
Example, but be not limited to) setting compensation circuit.In dragging system A first, it is direct current by grid side AC conversion by rectifier
Electricity；Then, stable DC is converted by intermediate DC link filter, then by inverter by DC conversion is negative
The alternating current of frequency, amplitude needed for carrying.In rectification side, using the uncontrollable rectification of diode.In inverter side, using space vector arteries and veins
The conducting of wide modulated signal control switching tube, and then export a series of constant amplitudes, not wide voltage signal in inverter outlet side.
The present embodiment devises compensation circuit shown in C in Fig. 1, and compensating electric capacity one end of the compensation circuit is grounded, separately
One end is connected to AGND by a switching tube G9, and with busbar by a switching tube G8 unicom, the switch element uses soft
Part control is opened and is disconnected；PWM variable-frequency motor dragging system medium-high frequency common-mode voltage variation rate dv/dt are calculated, when dv/dt is just
When value, AGND is connected in the compensating electric capacity of compensation circuit, is disconnected with busbar, and compensating electric capacity absorbs compressor leakage electric current；Work as dv/dt
For negative value when, the compensating electric capacity of compensation circuit connects busbar, is disconnected with AGND, generates external compensation electric current, when dv/dt is 0
When, the compensating electric capacity of compensation circuit is disconnected with AGND and busbar simultaneously.
The software realizes that microcontroller is connect by network with switch element using microcontroller, i.e., the described switch
Element using microcontroller control open and disconnect, microcontroller connect two switch elements, such as microcontroller by calculating after
Electric signal directly is sent out, by electrical transmission to switch element, after controlling its opening and disconnection or microcontroller by calculating
Send out radio signal (can also be the signals such as infrared, bluetooth, wireless network), the signal receiving circuit being connect with switch element
It is converted into drive signal after receiving signal, carrys out driving switch element and opens and disconnect.
The microcontroller can be the control mainboard using the electric appliance (such as air-conditioning, refrigerator) of the frequency-changeable compressor.
Compensating electric capacity C4 is larger in practical compensation circuit, and coupled capacitor parameter very little in motor, the two can not possibly reach
It is completely the same, it is susceptible to that compensation electric current is excessive to be caused leakage the case where instead increasing, to need according to compressor leakage electric current
Size selects appropriate compensation circuit current-limiting resistance Z1, limitation compensation current amplitude.
Because leaking and compensating current amplitude very little, compensation circuit is not limited to use forceful electric power that power supply occurs as compensation electric current.
When use forceful electric power PFC-DC as compensation circuit in compensation electric current occur power supply when, switch element use IGBT switching tubes；When making
When using the light current such as ± 15V that power supply occurs as compensation circuit compensation electric current, triode can be used in switch element.No matter forceful electric power is used
Or as compensation electric current power supply occurs for light current, and the control program of compensation circuit is consistent with following control methods.
Software is to the control flow of the compensation circuit of the present embodiment as shown in figure 4, detailed process is as follows：
1) voltage Us of the software chip detection sampling inverter IPM output UVW with respect to AGNDug、Uvg、Uwg, continuous sampling i+1
Group, wherein i=0,1,2 ...；
2) common-mode voltage U is calculatedcom, the on off state being presently in is determined according to value, wherein the calculating of common-mode voltage is public
Formula is：
UNgFor motor stator winding neutral point voltage-to-ground, i.e. common-mode voltage；
3) judgment step 2) calculated common-mode voltage UcomIn error range whether close to 0, Udc/3,2Udc/3,
Udc, if it is by UcomEqual to the theoretical value of corresponding on off state, it is stored in temporary register and obtains Ucomi、Ucomi+1, no
Then, step 1) and 2) is re-started；
The theoretical value of the corresponding on off state is 0, in Udc/3,2Udc/3, Udc with calculated common-mode voltage Ucom
That most similar value；
4) rising edge or failing edge detection are carried out：If Ucomi<Ucomi+1, then G9 switching tubes are connected, disconnect G8 switches
Pipe；If Ucomi>Ucomi+1, then G8 switching tubes are connected, disconnect G9 switching tubes；If not occurring level change, G9 is remained open
With G8 switching tubes；
5) temporary register is emptied.
Embodiment 2
The present embodiment and the variable-frequency motor dragging system A and compensation circuit C of the PWM modulation of embodiment 1 are just the same but soft
Part control method is different.
According to seven segmentation drive signal rules of SVPWM, in general, no matter being in which sector in six sectors, drive signal
The sum of (by taking G2, G4, G6 open 1, shutdown 0 as an example) conducting state is always according to the rule of (0,1,2,3,3,2,1,0,0,1 ...)
Variation.Get eve on off state and on off state this moment, you can prediction next time state change when UcomRising edge
Or failing edge situation, in state transformation next time, punctual output compensating circuit switching tube drive signal, compensates.Software
Control flow to the compensation circuit of the present embodiment is as shown in figure 5, detailed process is as follows：
1) the drive signal level height for obtaining SVPWM algorithms control inverter switching device pipe G2, G4, G6 represents high electricity with 1
It is flat, represent low level with 0；
2) three on off states are added summation；
3) tabled look-up according to previous next state and current state and confirm current state present position, predict that next state is on
Rise edge or failing edge；
4) it provides moment output compensating circuit switch element in next group of inverter switching device signal and controls signal, if next
Three on off state sums of a state are more than three on off state sums of current state, as rising edge, then
G9 switching tubes are connected, disconnect G8 switching tubes；If three on off state sums of next state are less than current state
G8 switching tubes are then connected in three on off state sums, i.e. failing edge, disconnect G9 switching tubes；If the three of next state
A on off state sum is identical as three on off state sums of current state, then disconnects the switch of AGND and busbar
Element, i.e. uncompensation.
Claims (9)
1. a kind of frequency-changeable compressor reduces the compensation circuit of leakage current, which is characterized in that the compensating electric capacity of the compensation circuit
One end is grounded, and the other end is connected to by a switch element respectively with AGND and busbar, and the switch element is controlled using software
It opens and disconnects；PWM variable-frequency motor dragging system medium-high frequency common-mode voltage variation rate dv/dt are calculated, when dv/dt is positive value,
The compensating electric capacity of compensation circuit is connected to AGND, is disconnected with busbar, and compensating electric capacity absorbs compressor leakage electric current；When dv/dt is negative
When value, the compensating electric capacity of compensation circuit connects busbar, is disconnected with AGND, generates external compensation electric current, when dv/dt is 0, mends
The compensating electric capacity for repaying circuit is disconnected with AGND and busbar simultaneously.
2. compensation circuit according to claim 1, which is characterized in that the ground terminal connection current limliting electricity of the compensating electric capacity
Resistance.
3. compensation circuit according to claim 2, which is characterized in that the size of the current-limiting resistance is according to actually detected
Leakage Current size determines.
4. compensation circuit according to claim 1, which is characterized in that mended in using forceful electric power PFC-DC as compensation circuit
When repaying electric current generation power supply, switch element uses IGBT switching tubes；Electricity occurs as compensation circuit compensation electric current when using light current
When source, triode can be used in switch element.
5. a kind of frequency-changeable compressor suitable for described in any one of claim 1-4 reduces the control of the compensation circuit of leakage current
Method processed, which is characterized in that described method includes following steps：
1) continuous acquisition i+1 groups inverter IPM outputs voltages of the UVW with respect to AGND, wherein i=0,1,2 ...；
2) common-mode voltage U is calculatedcom, the on off state being presently in is determined according to value；
If 3) Ucomi<Ucomi+1, then the switch element of connection AGND is opened, the switch element of connection busbar is disconnected；If Ucomi>
Ucomi+1, then the switch element of connection busbar is opened, the switch element of connection AGND is disconnected；If not occurring level change, protect
Hold the switch element for disconnecting AGND and busbar, wherein Ucomi、Ucomi+1For i-th group or the calculated common-mode voltage of i+1 group.
6. control method according to claim 5, which is characterized in that the calculation formula of common-mode voltage is in step 2)：
Wherein, Uug、Uvg、UwgRespectively inverter output end voltage-to-ground, UNgFor motor stator winding neutral point voltage-to-ground,
That is common-mode voltage.
7. control method according to claim 5, which is characterized in that increase examination step after step 2), that is, judge step
Rapid 2) calculated common-mode voltage UcomIn error range whether close to 0, Udc/3,2Udc/3, Udc, if it is by Ucom
Equal to the theoretical value of corresponding on off state, it is stored in temporary register and obtains Ucomi、Ucomi+1, otherwise, re-start step 1)
With 2)；The theoretical value of the corresponding on off state is 0, in Udc/3,2Udc/3, Udc with calculated common-mode voltage UcomMost phase
That close value.
8. a kind of frequency-changeable compressor suitable for described in any one of claim 1-4 reduces the control of the compensation circuit of leakage current
Method processed, which is characterized in that described method includes following steps：
1) the drive signal level height for obtaining three switching tubes of SVPWM algorithms control inverter, represents high level, with 0 with 1
Represent low level；
2) three on off states are added summation；
3) it is tabled look-up according to previous next state and current state and confirms current state present position, predict next state and next
The size of state dv/dt；
4) it provides moment output compensating circuit switch element in next group of inverter switching device signal and controls signal, when dv/dt is just
When value, then the switch element for opening connection AGND is controlled, disconnects the switch element of connection busbar；When dv/dt is negative value, then control
System opens the switch element of connection busbar, disconnects the switch element of connection AGND, when dv/dt is 0, then disconnects AGND and busbar
Switch element.
9. control method according to claim 8, which is characterized in that if the changing rule of the sum of inverter switching states
For：0,1,2,3,3,2,1,0,0,1 ..., then in step 4), if three on off state sums of next state are big
In three on off state sums of current state, then the switch element for opening connection AGND is controlled, disconnects connection busbar
Switch element；If three on off state sums of next state are less than three on off states phase of current state in addition
With, then control open connection busbar switch element, disconnect connection AGND switch element；If three of next state are opened
Off status sum is identical as three on off state sums of current state, then disconnects the switch member of AGND and busbar
Part.
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