CN111049413A - Inverter circuit and open-phase detection method - Google Patents
Inverter circuit and open-phase detection method Download PDFInfo
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- CN111049413A CN111049413A CN201911321012.3A CN201911321012A CN111049413A CN 111049413 A CN111049413 A CN 111049413A CN 201911321012 A CN201911321012 A CN 201911321012A CN 111049413 A CN111049413 A CN 111049413A
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/539—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency
- H02M7/5395—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters with automatic control of output wave form or frequency by pulse-width modulation
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R29/00—Arrangements for measuring or indicating electric quantities not covered by groups G01R19/00 - G01R27/00
- G01R29/16—Measuring asymmetry of polyphase networks
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- G—PHYSICS
- G01—MEASURING; TESTING
- G01R—MEASURING ELECTRIC VARIABLES; MEASURING MAGNETIC VARIABLES
- G01R31/00—Arrangements for testing electric properties; Arrangements for locating electric faults; Arrangements for electrical testing characterised by what is being tested not provided for elsewhere
- G01R31/40—Testing power supplies
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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
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/53—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
- H02M7/537—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters
- H02M7/5387—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration
- H02M7/53871—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only, e.g. single switched pulse inverters in a bridge configuration with automatic control of output voltage or current
Abstract
The embodiment of the application provides an inverter circuit and a phase-lack detection method, relates to the technical field of electric appliances, and can judge the phase-lack condition of a three-phase alternating-current power supply according to the period of a ripple electric signal of a direct-current bus and expand the application range of the phase-lack detection method. The inverter circuit includes: the rectifying branch is used for converting alternating current signals input by the three-phase alternating current power supply into direct current signals. The filtering branch circuit is used for filtering the direct current signal to obtain a ripple electric signal and a filtered direct current signal. The sampling control branch is used for: determining a first period of the ripple electrical signal; determining a second period of the alternating current signal; if the first period and the second period meet the preset condition, determining that the alternating current signal is in a phase failure; and sending a control signal to the inversion branch. And the inversion branch circuit is used for receiving the control signal sent by the sampling control branch circuit and sending the control signal to the compressor. The embodiment of the application is applied to detecting the phase-lack condition of the three-phase alternating-current power supply.
Description
Technical Field
The application relates to the technical field of electric appliances, in particular to an inverter circuit and a phase loss detection method.
Background
Three-phase inverter systems for converting a dc signal into an ac signal are generally included in electrical products. When a three-phase alternating current power supply supplying power to a three-phase inverter system is in phase failure, the input current of the three-phase inverter system is too high, and the service life of a power device is influenced. Therefore, it is important to detect whether the three-phase ac power supply is out of phase.
In the prior art, a three-phase inverter system with electrolytic capacitor filtering can be used for detecting whether a three-phase alternating current power supply is deficient or not. Specifically, the three-phase inverter system detects a ripple electrical signal on the dc bus. And if the ripple electric signal exceeds a preset threshold value, the three-phase inverter system determines that the three-phase alternating current power supply is in phase failure. However, this method can only be used in a three-phase inverter system with electrolytic capacitor filtering to detect the defect of the three-phase ac power supply, and has a narrow application range.
Disclosure of Invention
The embodiment of the application provides an inverter circuit and a phase-lack detection method, which can judge the phase-lack condition of a three-phase alternating-current power supply according to the period of a ripple electric signal of a direct-current bus and expand the application range of the phase-lack detection method.
In order to achieve the above purpose, the embodiment of the present application adopts the following technical solutions:
in a first aspect, an embodiment of the present application provides an inverter circuit, including: the circuit comprises a rectifying branch, a filtering branch, a sampling control branch and an inversion branch. The input of rectification branch road is connected three-phase alternating current power supply, and the input of filtering branch road is connected to the output of rectification branch road, and the first input of sampling control branch road is connected to the output of filtering branch road, and the compressor is connected to the second input of sampling control branch road, and the input of contravariant branch road is connected to the output of sampling control branch road, and the compressor is connected to the output of contravariant branch road.
The rectifying branch converts an alternating current signal input by a three-phase alternating current power supply into a direct current signal. And then, the filtering branch circuit filters the direct current signal to obtain a ripple electric signal and a filtered direct current signal.
The sampling control branch determines a first period of the ripple electrical signal. A second period of the alternating current signal. And if the first period and the second period meet the preset condition, determining that the alternating current signal is in a phase failure. And sending a control signal to the inversion branch, wherein the control signal is used for indicating to reduce the running frequency of the compressor.
And the inversion branch circuit receives the control signal sent by the sampling control branch circuit and sends the control signal to the compressor.
In practical applications, when an ac signal input from a three-phase ac power supply does not lack a phase, the ac signal is 120 degrees of phase difference with the same three-phase frequency, wherein the period of each phase of the ac signal is 360 degrees. Therefore, according to the rectification characteristic, the phase difference of the direct current signal after the alternating current signal passes through the rectification branch circuit is 60 degrees, and the direct current signal is still an electric signal with the magnitude changing along with time. Therefore, when the direct current signal passes through the filtering branch circuit, the charging and discharging process of the capacitor in the filtering branch circuit is completed every 60 degrees. And because the filtering branch circuit can not completely filter out the components (namely ripple electric signals) with the time-varying sizes in the direct current electric signals when filtering the direct current electric signals, the period of the ripple electric signals is the same as the charging and discharging period of the capacitors in the filtering branch circuit, and is 1/6 of the period of the alternating current electric signals.
In summary, the present application obtains a first period of the ripple electrical signal and a second period of the ac electrical signal. Then, the phase failure of the alternating current signal can be judged according to the relation between the first period and the second period. Therefore, the application range of the phase-defect detection method is expanded.
In a second aspect, an embodiment of the present application provides a phase-loss detection method applied to the inverter circuit according to the first aspect, the method including:
the inverter circuit determines a first period of the ripple electrical signal. The ripple electric signal is a filtering branch in the inverter circuit and is obtained by filtering a direct current electric signal. The direct current signal is obtained by converting an alternating current signal through a rectifying branch in an inverter circuit. The ac signal is an ac signal input from a three-phase ac power supply for supplying power to the inverter circuit.
The inverter circuit determines a second period of the alternating current signal. And then, if the first period and the second period meet the preset condition, determining that the alternating current signal is in a phase failure state. A control signal is sent to the compressor indicating a reduced operating frequency of the compressor.
It is to be understood that the above-described provided open-phase detection method is used to detect whether the three-phase alternating-current power supply of the inverter circuit of the first aspect is open-phase. Therefore, the inverter circuit of the first aspect and the corresponding solutions in the following embodiments may be referred to for the advantageous effects that can be achieved by the inverter circuit, and details are not repeated here.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the description of the embodiments or the prior art will be briefly described below, and it is obvious that the drawings in the following description are only some embodiments of the present invention, and it is obvious for those skilled in the art that other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a three-phase inverter system in the prior art;
fig. 2 is a schematic structural diagram of an inverter circuit provided in an embodiment of the present application;
fig. 3 is a schematic structural diagram of an inverter circuit according to another embodiment of the present application;
fig. 4 is a schematic structural diagram of a filtering branch circuit according to an embodiment of the present application;
FIG. 5 is a waveform diagram of an electrical signal provided by an embodiment of the present application;
FIG. 6 is a schematic diagram of a waveform of an electrical signal according to another embodiment of the present application;
fig. 7 is a schematic flowchart of a phase loss detection method according to an embodiment of the present application.
Detailed Description
The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terms "first," "second," and the like in the description and claims of the present invention and in the above-described drawings are used for distinguishing between different objects and not for limiting a particular order.
In the embodiments of the present invention, words such as "exemplary" or "for example" are used to mean serving as examples, illustrations or descriptions. Any embodiment or design described as "exemplary" or "e.g.," an embodiment of the present invention is not necessarily to be construed as preferred or advantageous over other embodiments or designs. Rather, use of the word "exemplary" or "such as" is intended to present concepts related in a concrete fashion.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity. Further, where considered appropriate, reference numerals may be repeated among the figures to indicate corresponding or analogous elements to the problem.
Fig. 1 shows a prior art three-phase inverter system. As shown in fig. 1, the conventional three-phase inverter system includes: a three-phase ac power supply 11, an inverter circuit 12, and a compressor 13. The inverter circuit 12 includes a rectifying circuit 121, a filter circuit 122, an inverter circuit 123, a switching power supply 124, and a Micro Controller Unit (MCU) 125. The three-phase alternating current power supply 11 is connected with an input end of a rectifying circuit 121 in the inverter circuit 12, a first output end of the rectifying circuit 121 is connected with an input end of a filter circuit 122, a first output end of the rectifying circuit 121 is connected with an input end of a switching power supply 124, an output end of the filter circuit 122 is connected with a first input end of an inverter circuit 123, an output end of the switching power supply 124 is connected with an input end of an MCU 125, an output end of the MCU 125 is connected with a second input end of the inverter circuit 123, and an output end of the inverter circuit 123 is. Wherein the compressor 13 is an inverter compressor.
The three-phase ac power supply 11 supplies power to the inverter circuit 12, and the inverter circuit 12 operates the compressor 13 by controlling the operating frequency of the compressor 13. The rectifier circuit 121 converts an ac signal input from the three-phase ac power supply 11 into a dc signal, which is also referred to as a pulsating dc signal. The filter circuit 122 filters the direct current signal to obtain a ripple electric signal and a filtered direct current signal. Meanwhile, the inverter circuit 12 supplies power to the MCU 125 through the switching power supply 124 by using a dc signal, so that the MCU 125 controls the inverter circuit 123 to invert the filtered dc signal into an ac signal to control the operation of the compressor.
When a three-phase alternating current power supply supplying power to the three-phase inverter system is in phase failure, the input current of the three-phase inverter system is too high, and the service life of a power device is influenced. Therefore, it is proposed in the prior art to detect whether a three-phase ac power supply is defective by using a three-phase inverter system with electrolytic capacitor filtering. However, this method can only be used in a three-phase inverter system with electrolytic capacitor filtering to detect the defect of the three-phase ac power supply, and has a narrow application range.
Of course, there is a method for detecting a fault of a three-phase ac power source in a three-phase inverter system without electrolytic capacitor filtering in the prior art, that is, a photocoupler is connected to an input end of the three-phase ac power source of the three-phase inverter system to detect the fault of the three-phase ac power source. However, this method requires an additional photocoupler to be added to the three-phase inverter system, and has a complicated circuit and high design cost.
In view of the above problems, embodiments of the present application provide an inverter circuit that can be used to detect whether a three-phase ac power supply is defective.
Fig. 2 shows a structure of an inverter circuit provided in an embodiment of the present application. As shown in fig. 2, the inverter circuit 22 includes a rectifying branch 221, a filtering branch 222, a sampling control branch 224, and an inverting branch 223.
The input end of the rectifying branch 221 is connected to the three-phase ac power supply 21, the output end of the rectifying branch 221 is connected to the input end of the filtering branch 222, the output end of the filtering branch 222 is connected to the first input end of the sampling control branch 224, the second input end of the sampling control branch 224 is connected to the compressor 23, the output end of the sampling control branch 224 is connected to the input end of the inverting branch 223, and the output end of the inverting branch 223 is connected to the compressor 23. The compressor 23 is an inverter compressor in the present application.
Illustratively, as shown in fig. 3, the rectifying branch 221 is a three-phase full-wave rectifying bridge. Referring to fig. 3, the rectifying branch 31 includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6. The output terminals of D1, D2 and D3 are connected. The inputs of D4, D5 and D6 are connected. The output end of the D4 is connected with the input end of the D1 and is also connected with the R-phase output end of the three-phase alternating current power supply 21. The output end of the D5 is connected with the input end of the D2 and is also connected with the S-phase output end of the three-phase alternating current power supply 21. The output end of the D6 is connected with the input end of the D3 and is also connected with the T-phase output end of the three-phase alternating current power supply 21. The input end of the diode is a conducting end capable of conducting voltage, and the output end of the diode is a non-conducting end. The output terminals of the three-phase ac power supply 21 include an R-phase output terminal, an S-phase output terminal, and a T-phase output terminal.
Optionally, the filtering branch 222 includes at least one thin film capacitor. For example, referring to fig. 4 in conjunction with fig. 3, the filter branch 222 includes a first thin film capacitor C1 and a second thin film capacitor C2. The connection line after the output terminals of D1, D2 and D3 in the rectifying branch 221 are connected is line 1, and the connection line after the input terminals of D4, D5 and D6 are connected is line 1. The first terminal of C1 is connected to line 1 and the second terminal is connected to line 2. The first end of C2 is connected with wire 1 and the second end is connected with wire 2. I.e., C1 and 2 are connected in parallel between line 1 and line 2.
Illustratively, the inverting branch 223 is an Intelligent Power Module (IPM) inverting circuit. Referring to the inverting branch 223 in fig. 3, the inverting branch 223 includes a first transistor IGBT1, a second transistor IGBT2, a third transistor IGBT3, a fourth transistor IGBT4, a fifth transistor IGBT5, and a sixth transistor IGBT 6; a seventh diode D7, an eighth diode D8, a ninth diode D9, a twelfth diode D10, an eleventh diode D11, a twelfth diode D12, and a Driver circuit. The first end of the IGBT1 is connected with Driver, the second end is connected with the output end of the D7, and the third end is connected with the input end of the D7. The first end of the IGBT2 is connected with Driver, the second end is connected with the output end of the D8, and the third end is connected with the input end of the D8. The first end of the IGBT3 is connected with Driver, the second end is connected with the output end of the D9, and the third end is connected with the input end of the D9. The first end of the IGBT4 is connected with Driver, the second end is connected with the output end of the D10, and the third end is connected with the input end of the D10. The first end of the IGBT5 is connected with Driver, the second end is connected with the output end of the D11, and the third end is connected with the input end of the D11. The first end of the IGBT6 is connected with Driver, the second end is connected with the output end of the D12, and the third end is connected with the input end of the D12. The second terminals of the IGBT1, IGBT2, and IGBT3 are connected. The third terminals of the IGBT4, IGBT5, and IGBT6 are connected. And the third end of the IGBT1 is connected with the second end of the IGBT4 and is also connected with the W-phase input end of the compressor. And the third end of the IGBT2 is connected with the second end of the IGBT5 and is also connected with the U-phase input end of the compressor. And the third end of the IGBT3 is connected with the second end of the IGBT6 and is also connected with the V-phase input end of the compressor. Optionally, the transistor IGBT in the inverting branch 223 is an insulated gate bipolar transistor. The first end of the transistor IGBT is a grid electrode, the second end of the transistor IGBT is a collector electrode, and the third end of the transistor IGBT is an emitter electrode.
Optionally, referring to fig. 3 in combination with fig. 2, a third input end of the sampling control branch 33 is connected to a Driver in the inverting branch 34 as a protection loop of the sampling control branch 33. The sampling control branch 33 is connected to Vcc through series connected resistors R1 and R2 and to the common voltage terminal Vdd of the circuit through a ground resistor (not shown in the figure).
Optionally, the inverter circuit 22 further includes a switching power supply, and referring to fig. 3, the first terminal of the switching power supply 35 is connected to the line 1, and the first terminal of the switching power supply is connected to the line 2, so as to provide an optional input voltage for the sampling control branch 224. The optional input voltage may be a voltage value of 5V, 12V, or the like.
Optionally, the inverter circuit 22 further includes a resistor RY connected in series between the rectifying branch 31 and the filtering branch 32, and a switch connected in parallel with the resistor RY.
Specifically, the operation principle of the inverter circuit 22 is as follows:
in the first step, the rectifying branch 221 converts an ac signal input from the three-phase ac power supply 21 into a dc signal, which is also referred to as a pulsating dc signal. The filtering branch 222 then filters the dc signal to obtain a ripple electrical signal and a filtered dc signal.
Second, first, the sampling control branch 224 determines a first period, which is the period of the ripple electrical signal.
Specifically, the sampling control branch 224 collects the ripple electrical signal in each preset collection period. More specifically, the sampling control branch 224 obtains a carrier frequency period of Pulse Width Modulation (PWM), and collects the ripple electrical signal by taking the carrier frequency period of the PWM as a preset collection period.
The sampling control branch 224 determines the median of the values of the ripple electrical signal during the i-1 th preset acquisition period. Specifically, the sampling control branch 224 determines the maximum value and the minimum value of the ripple electric signal in the i-1 th preset acquisition period. And determining the intermediate value of the ripple electric signal value according to the maximum value and the minimum value. More specifically, the sampling control branch 224 records the maximum value and the minimum value of the ripple electric signal in the i-1 th preset acquisition period, and uses the formula VIn＝VMinimum size+(VMaximum of-VMinimum size) And/2 calculating the intermediate value of the ripple electric signal value. Wherein, VInIntermediate value, V, representing the value of the ripple electric signalMinimum sizeRepresenting the minimum value, V, of the ripple electric signalMaximum ofRepresenting the maximum value of the ripple electrical signal.
The sampling control branch 224 determines a first time at which the value of the first ripple electrical signal is smaller than the intermediate value in the ith acquisition period. See, for example, point a in fig. 5. And determining a second moment when the first value is smaller than the intermediate value in the (i + 1) th acquisition period. See, for example, point b in fig. 5.
The sampling control branch 224 determines the duration of the first period as the difference between the second time and the first time.
Next, the sampling control branch 224 determines a second period, which is the period of the ac electric signal.
Specifically, the sampling control branch 224 obtains the frequency of the ac electrical signal output by the three-phase ac power supply 21, and calculates the second period of the ac electrical signal according to the frequency, for example, when the frequency of the ac electrical signal output by the three-phase ac power supply 21 is 50Hz, the second period is 1/50Hz — 20 ms.
And thirdly, if the sampling control branch 224 determines that the first period and the second period meet the preset condition, it determines that the alternating current signal is in a phase failure.
Specifically, referring to fig. 5 in conjunction with fig. 2, the present application provides an electrical signal waveform including an ac signal waveform a with a phase difference of 120 degrees in a three-phase ac power supply 21. The alternating current signal passes through the rectifying branch 221 to form a direct current signal waveform B. And a ripple electrical signal waveform C after the dc electrical signal passes through the filtering branch 222. The alternating current signal waveform A comprises a first phase electric signal waveform, a second phase electric signal waveform and a third phase electric signal waveform.
The ac signal input from the three-phase ac power supply 21 for supplying power to the inverter circuit 22 is not out of phase, and the waveform of the ac signal is a three-phase signal waveform having the same frequency and a phase difference of 120 degrees, wherein the period of each phase of the ac signal is 360 degrees. Therefore, according to the rectification characteristic (in this case, the rectification characteristic of the three-phase full-wave rectifier bridge), the phase difference of the dc signal waveform B after the ac signal waveform a passes through the rectification branch 221 is 60 degrees, and is still an electrical signal whose magnitude changes with time. Therefore, when the dc signal passes through the filtering branch 222, the charging and discharging process of the capacitor in the filtering branch 222 is completed every 60 degrees. And because the filtering branch 222 can not completely filter out the time-varying component (i.e., the ripple electrical signal C) in the dc electrical signal waveform B. Therefore, the period of the ripple electric signal is 1/6 times the period of the ac electric signal, which is the same as the charging and discharging periods of the capacitors in the filter branches. For example, the period of the ripple electric signal is 60 degrees from the point a to the point b shown in fig. 5. For another example, when the frequency of the ac electric signal output from the three-phase ac power supply 21 is calculated to be 50Hz, the period of the ripple electric signal should be 3.33 ms.
Further, referring to fig. 6 in conjunction with fig. 2, the present application provides an electrical signal waveform comprising a phase-lacking alternating current electrical signal waveform a. The alternating current signal passes through the rectifying branch 221 to form a direct current signal waveform B. And a ripple electrical signal waveform C after the dc electrical signal passes through the filtering branch 222. The alternating current signal waveform A comprises a first phase electric signal waveform and a second phase electric signal waveform.
The three-phase ac power supply 21 for supplying power to the inverter circuit 22 inputs an ac signal lacking one-phase electrical signal, wherein the phase difference between the second-phase electrical signal and the first-phase electrical signal is 120 degrees, and the period of each phase electrical signal is 360 degrees. Therefore, in the two-phase dc signal of the dc signal waveform B after the ac signal waveform a passes through the rectifying branch 221, the second-phase dc signal is 60 degrees out of phase with the first-phase dc signal in the same cycle (the cycle of the rectified dc signal is 180 degrees), but 120 degrees out of phase with the first-phase dc signal in the next cycle. Therefore, when the dc signal passes through the filtering branch 222, the charging and discharging process of the capacitor in the filtering branch 222 is completed every 180 degrees. And because the filtering branch 222 can not completely filter out the time-varying component (i.e., the ripple electrical signal C) in the dc electrical signal waveform B. Therefore, the period of the ripple electric signal is 1/2 times the period of the ac electric signal, which is the same as the charging and discharging periods of the capacitors in the filter branches. For example, see fig. 6, where the period of the ripple electrical signal is 180 degrees from point a to point b. For another example, when the frequency of the ac electric signal output from the three-phase ac power supply 21 is calculated to be 50Hz, the period of the ripple electric signal should be 10 ms.
Since the ac signals of different frequencies output by the three-phase ac power supply 21 may be disturbed during actual operation, the value of the first period is allowed to fluctuate within a certain range after 1/6 of the period of the ac signal. For example, ± 25% of the period 1/6 of the ac electrical signal may be taken as the preset numerical range for the first period.
In summary, when the first period is within the preset value range, the sampling control branch 224 determines that the ac signal input by the three-phase ac power supply 21 is not out of phase. When the first period is not within the preset value range and continues for a predetermined period of time, for example, 200ms, the sampling control branch 224 determines that the ac signal input from the three-phase ac power supply 21 is out of phase.
Alternatively, the preset condition may be a value range calculated according to the frequency of the ac signal output from the three-phase ac power supply 21, in order to be compatible with the ac signals of different frequencies output from the three-phase ac power supply 21. For example, the output ac signal of the three-phase ac power supply 21 may be a 50Hz or 60Hz input. Then the sum of 1/6 for a 50Hz period of 3.33ms and 25% of 3.33ms and 3.33ms is taken as the upper limit of the range, i.e., the value
The lower limit of this range is defined as the sum of 1/6 ms for a 60Hz period of 2.78ms and 25% of 2.78ms and 2.78ms, i.e. the lower limit of the range
The value range is therefore [2.08ms, 4.16ms]。
Finally, when the sampling control branch 224 determines that the ac signal is out of phase, it sends a control signal to the inverting branch 223, where the control signal is used to instruct to decrease the operating frequency of the compressor 23, for example, to instruct to decrease the operating frequency of the compressor 23 to 70% of the original operating frequency.
In the third step, the inverting branch 223 receives the control signal sent by the sampling control branch 224 and sends the control signal to the compressor 23.
Optionally, within a preset time period after the control signal is sent to the compressor 23, if it is determined that the current of the compressor 23 is not reduced to the preset current, the sampling control branch 224 sends an alarm. And sends a stop signal to the inverting branch 223, the stop signal being used to instruct the compressor 23 to stop operating.
In practical applications, when an ac signal input from a three-phase ac power supply does not lack a phase, the ac signal is 120 degrees of phase difference with the same three-phase frequency, wherein the period of each phase of the ac signal is 360 degrees. Therefore, according to the rectification characteristic, the phase difference of the direct current signal after the alternating current signal passes through the rectification branch circuit is 60 degrees, and the direct current signal is still an electric signal with the magnitude changing along with time. Therefore, when the direct current signal passes through the filtering branch circuit, the charging and discharging process of the capacitor in the filtering branch circuit is completed every 60 degrees. And because the filtering branch circuit can not completely filter out the components (namely ripple electric signals) with the time-varying sizes in the direct current electric signals when filtering the direct current electric signals, the period of the ripple electric signals is the same as the charging and discharging period of the capacitors in the filtering branch circuit, and is 1/6 of the period of the alternating current electric signals. To sum up, first, the present application obtains a first period of the ripple electrical signal and a second period of the ac electrical signal. The phase-lack condition of the alternating current signal can be judged according to the relation between the first period and the second period, and the application range of the phase-lack detection method is expanded. Secondly, this application directly utilizes the sampling control branch road to carry out the sampling calculation to the first cycle of ripple signal of telecommunication, acquires the frequency of three-phase alternating current power, has avoided increasing complicated circuit design, has saved the design cost.
Based on the inverter circuit described above, the present application provides a phase loss detection method, as shown in fig. 7, including:
701. the inverter circuit determines a first period.
The first period is the period of the ripple electrical signal. The ripple electric signal is a filtering branch in the inverter circuit and is obtained by filtering a direct current electric signal. The direct current signal is obtained by converting an alternating current signal through a rectifying branch in an inverter circuit. The ac signal is an ac signal input from a three-phase ac power supply for supplying power to the inverter circuit.
Specifically, the inverter circuit collects the ripple electric signal in each preset collection period. And the inverter circuit determines the intermediate value of the ripple electric signal value in the (i-1) th preset acquisition period. More specifically, the inverter circuit determines the maximum value and the minimum value of the ripple electric signal in the (i-1) th preset acquisition period. And determining the intermediate value of the ripple electric signal value according to the maximum value and the minimum value. The inverter circuit determines a first moment, wherein the first moment is a moment when the numerical value of the first ripple electric signal is smaller than the intermediate value in the ith acquisition period. And the inverter circuit determines a second moment, wherein the second moment is a moment when the first numerical value is smaller than the intermediate value in the (i + 1) th acquisition period. The inverter circuit determines a duration of the first period as a difference between the second time and the first time.
702. The inverter circuit determines a second period.
Wherein the second period is a period of the alternating current signal.
703. And if the first period and the second period of the inverter circuit meet the preset condition, determining that the alternating current signal is in a phase failure state.
704. The inverter circuit sends a control signal to the compressor, the control signal being indicative of a reduced operating frequency of the compressor.
Optionally, within a preset time period after the control signal is sent to the compressor, if it is determined that the current of the compressor is not reduced to the preset current, an alarm is sent. And sends a stop signal to the inverting branch 223, the stop signal being used to instruct the compressor 23 to stop operating.
It should be understood that, in the various embodiments of the present application, the sequence numbers of the above-mentioned processes do not mean the execution sequence, and the execution sequence of each process should be determined by its function and inherent logic, and should not constitute any limitation to the implementation process of the embodiments of the present application.
In the several embodiments provided in the present application, it should be understood that the disclosed system, apparatus, and method may be implemented in other ways. For example, the above-described device embodiments are merely illustrative, and for example, the division of the units is only one logical functional division, and other divisions may be realized in practice, for example, a plurality of units or components may be combined or integrated into another system, or some features may be omitted, or not executed. In addition, the shown or discussed mutual coupling or direct coupling or communication connection may be an indirect coupling or communication connection through some interfaces, devices or units, and may be in an electrical, mechanical or other form.
Units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one place, or may be distributed on a plurality of network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiment.
In addition, functional units in the embodiments of the present application may be integrated into one processing unit, or each unit may exist alone physically, or two or more units are integrated into one unit.
The above description is only for the specific embodiments of the present invention, but the scope of the present invention is not limited thereto, and any person skilled in the art can easily conceive of the changes or substitutions within the technical scope of the present invention, and all the changes or substitutions should be covered within the scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the appended claims.
Claims (9)
1. An inverter circuit comprises a rectifying branch, a filtering branch, a sampling control branch and an inverting branch;
the input end of the rectification branch circuit is connected with a three-phase alternating current power supply, the output end of the rectification branch circuit is connected with the input end of the filtering branch circuit, the output end of the filtering branch circuit is connected with the first input end of the sampling control branch circuit, the second input end of the sampling control branch circuit is connected with a compressor, the output end of the sampling control branch circuit is connected with the input end of the inversion branch circuit, and the output end of the inversion branch circuit is connected with the compressor;
the rectification branch circuit is used for converting an alternating current signal input by the three-phase alternating current power supply into a direct current signal; the filtering branch is used for filtering the direct current signal to obtain a ripple electric signal and a filtered direct current signal; it is characterized in that the preparation method is characterized in that,
the sampling control branch is used for:
determining a first period, wherein the first period is the period of the ripple electric signal; determining a second period, wherein the second period is the period of the alternating current signal; if the first period and the second period meet a preset condition, determining that the alternating current signal is in a phase failure; sending a control signal to the inversion branch, wherein the control signal is used for indicating to reduce the running frequency of the compressor;
and the inversion branch circuit is used for receiving the control signal sent by the sampling control branch circuit and sending the control signal to the compressor.
2. The inverter circuit according to claim 1, wherein the sampling control branch is specifically configured to:
collecting the ripple electric signal in each preset collection period;
determining the intermediate value of the ripple electric signal value in the i-1 th preset acquisition period;
determining a first moment, wherein the first moment is a moment when the numerical value of the first ripple electric signal is smaller than the intermediate value in the ith acquisition period;
determining a second moment, wherein the second moment is a moment when a first numerical value is smaller than the intermediate value in the (i + 1) th acquisition cycle;
and determining the duration of the first period as the difference between the second moment and the first moment.
3. The inverter circuit according to claim 2, wherein the sampling control branch is specifically configured to:
determining the maximum value and the minimum value of the ripple electric signal in the (i-1) th preset acquisition period;
and determining the intermediate value of the ripple electric signal value according to the maximum value and the minimum value.
4. The inverter circuit according to any one of claims 1 to 3, wherein the sampling control branch is further configured to:
and within a preset time after the control signal is sent to the inversion branch, if the current of the compressor is determined not to be reduced to the preset current, an alarm is sent.
5. The inverter circuit according to claim 4,
the filtering branch circuit comprises at least one thin film capacitor.
6. A phase loss detection method for an inverter circuit,
determining a first period, wherein the first period is a period of a ripple electric signal, the ripple electric signal is a filtering branch in the inverter circuit, and the ripple electric signal is obtained by filtering a direct-current electric signal; the direct current signal is a rectifying branch in the inverter circuit and is obtained after alternating current signals are converted; the alternating current signal is an alternating current signal input by a three-phase alternating current power supply for supplying power to the inverter circuit;
determining a second period, wherein the second period is the period of the alternating current signal;
if the first period and the second period meet a preset condition, determining that the alternating current signal is in a phase failure;
sending a control signal to a compressor, the control signal for indicating a reduced operating frequency of the compressor.
7. The method according to claim 6, wherein the determining a first period comprises:
collecting the ripple electric signal in each preset collection period;
determining the intermediate value of the ripple electric signal value in the i-1 th preset acquisition period;
determining a first moment, wherein the first moment is a moment when the numerical value of the first ripple electric signal is smaller than the intermediate value in the ith acquisition period;
determining a second moment, wherein the second moment is a moment when a first numerical value is smaller than the intermediate value in the (i + 1) th acquisition cycle;
and determining the duration of the first period as the difference between the second moment and the first moment.
8. The method according to claim 7, wherein the determining the median of the values of the ripple electric signal in the i-1 th preset acquisition period comprises:
determining the maximum value and the minimum value of the ripple electric signal in the (i-1) th preset acquisition period;
and determining the intermediate value of the ripple electric signal value according to the maximum value and the minimum value.
9. The method according to any one of claims 6 to 8, characterized in that the method further comprises:
and within a preset time after the control signal is sent to the compressor, if the current of the compressor is determined not to be reduced to the preset current, an alarm is sent.
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