CN114322228B - Air conditioner - Google Patents
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- CN114322228B CN114322228B CN202210004658.4A CN202210004658A CN114322228B CN 114322228 B CN114322228 B CN 114322228B CN 202210004658 A CN202210004658 A CN 202210004658A CN 114322228 B CN114322228 B CN 114322228B
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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
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- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
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- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
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Abstract
The invention discloses an air conditioner, comprising: a processing unit configured to: when the number of the channels is switched, relative to the PWM1 waveform of the first channel, when the single channel and the double channels are switched, the phase between the channels is gradually increased and decreased, so that the phase difference of 180 degrees between the two channels is gradually completed, when the first channel and the second channel work and the first channel, the second channel and the third channel work, the phase between the channels is gradually increased and decreased, so that the phase conversion between 120 degrees and 180 degrees between the PWM1 waveform of the first channel and the PWM2 waveform of the second channel is gradually completed, and the phase conversion between 240 degrees and 360 degrees between the PWM1 waveform of the first channel and the PWM3 waveform of the third channel is gradually completed. The invention can avoid current overshoot generated when the multi-channel PFC circuit switches channels.
Description
Technical Field
The invention relates to the field of air conditioner control, in particular to an air conditioner.
Background
The variable frequency air conditioner adopts a PFC (Power Factor Correction) circuit to carry out Power Factor Correction on an AC-DC link. After the PFC circuit is adopted, the harmonic content injected into the power grid by the variable frequency air conditioner can be limited to the lowest level, and the power factor (the ratio of active power to apparent power) is close to 1, so that the harmonic interference of the air conditioner electronic control on the external power grid is reduced.
In order to effectively reduce harmonics and reduce the size, a multichannel interleaved PFC circuit is widely used, and the number of channels of the multichannel interleaved PFC circuit generally changes according to the magnitude of an input current in a fixed order.
For example, the three-channel PFC circuit starts only the first channel at a small current with the rise of the current; starting the second channel again at medium current to perform double-channel control; and the third channel is started to carry out three-channel control when the current is high.
When the ambient temperature of the PFC circuit changes, changing the number of channels according to a fixed input current may cause a part of the channels to bear a large thermal stress, which affects the service life of the PFC circuit.
In addition, when the channels of the multichannel staggered PFC circuit are switched, the phase among the channels needs to be redistributed, if the operation of the two channels is switched into the operation of three channels, the phase difference of 180 degrees between the two channels is adjusted to the phase difference of 120 degrees between the three channels, if direct phase jump causes larger current overshoot, faults such as overcurrent and the like can be caused, and the whole PFC circuit fails.
Disclosure of Invention
The invention aims to provide an air conditioner, which changes input current by considering the temperature of a power device in a multi-channel PFC circuit so as to control the number of switching channels, and gradually completes phase conversion among the channels by adopting a mode of gradually increasing and decreasing phases among the channels and simultaneously adjusting duty ratio when the number of the channels is switched, so that current overshoot generated during channel switching is avoided, and the use reliability of the multi-channel PFC circuit and the air conditioner is not influenced.
In order to realize the purpose of the invention, the invention adopts the following technical scheme to realize:
the application relates to an air conditioner, its characterized in that includes:
a refrigerant circulation circuit for circulating a refrigerant in a refrigerant line in which the compressor, the condenser, the throttle element, the evaporator and the four-way valve are communicated;
a multi-channel PFC circuit including a plurality of PFC channels connected in parallel;
the temperature sensor is used for detecting the temperature of a switching power device in the multi-channel PFC circuit;
a processing unit configured to:
acquiring the input current of the multichannel PFC circuit;
according to the input current and the number of the switching channels of the plurality of threshold currents, correcting the threshold currents through the temperature fed back by the temperature sensor;
when the number of the channels is switched, relative to the PWM1 waveform of the first channel, when the single channel and the double channels are switched, the phase between the channels is gradually increased and decreased, so that the phase difference of 180 degrees between the two channels is gradually completed, when the first channel and the second channel work and the first channel, the second channel and the third channel work, the phase between the channels is gradually increased and decreased, so that the phase conversion between 120 degrees and 180 degrees between the PWM1 waveform of the first channel and the PWM2 waveform of the second channel is gradually completed, and the phase conversion between 240 degrees and 360 degrees between the PWM1 waveform of the first channel and the PWM3 waveform of the third channel is gradually completed.
In some embodiments of the present application, switching the number of channels according to the input current and the plurality of threshold currents specifically includes:
when the input current is larger than a second threshold current, the multi-channel PFC circuit is switched from a single channel to a double channel;
when the input current is smaller than a first threshold current, the multi-channel PFC circuit is switched from a dual-channel mode to a single-channel mode;
when the input current is larger than a fourth threshold current, the multi-channel PFC circuit is switched from a double channel to a three channel;
when the input current is smaller than a third threshold current, the multi-channel PFC circuit is switched from three channels to two channels;
each threshold current includes a first threshold current, a second threshold current, a third threshold current, and a fourth threshold current that increase in sequence.
In some embodiments of the present application, each threshold current is corrected by a temperature fed back by the temperature sensor, specifically:
when the temperature is higher than or equal to a first high temperature, the first threshold current, the second threshold current, the third threshold current and the fourth threshold current are sequentially reduced by a first current difference value;
when the temperature is higher than or equal to a second high temperature, the first threshold current, the second threshold current, the third threshold current and the fourth threshold current are sequentially reduced by a second current difference value;
the first high temperature is less than the second high temperature, and the first current difference is less than the second current difference.
In some embodiments of the present application, the switching power devices on three channels in the multi-channel PFC circuit are all disposed on a heat sink;
the temperature sensor is arranged on the heat sink.
In some embodiments of the present application, the input current is calculated as follows:
the input current Iac = Vdc × Idc/Vac;
where Vdc is the dc bus voltage, idc is the dc bus current, and Vac is the input voltage.
In some embodiments of the present application, when switching between a single channel and a dual channel, the inter-channel phase is gradually increased or decreased, so that a mutual difference 180-degree phase angle is gradually completed between the two channels, specifically:
when the multi-channel PFC circuit is switched between a single channel and two channels, the PWM wave of the channel to be switched on or off is switched at the phase beta =180 degrees/n in the adjacent PWM period;
wherein T is a set time required for completing the switching, T pwm For PWM period, n = T/T pwm 。
In some embodiments of the present application, the PWM2 wave transitions phase β between adjacent PWM periods when the multi-channel PFC circuit switches from first channel operation to both first and second channel operation.
In some embodiments of the present application, when the multi-channel PFC circuit switches from the first channel and the second channel to the first channel, the PWM2 wave switches the phase β in the adjacent PWM period, and when the switching is completed, the duty ratio of the PWM2 waveform is adjusted to 0.
In some embodiments of the present application, when switching between the first channel and the second channel, and between the first channel, the second channel, and the third channel, the inter-channel phase is gradually increased or decreased, so that phase transition between 120 degrees and 180 degrees is gradually completed between the PWM1 waveform and the PWM2 waveform, and phase transition between 240 degrees and 360 degrees is gradually completed between the PWM1 waveform and the PWM3 waveform, specifically:
when the multi-channel PFC circuit is switched among the first channel, the second channel and the third channel, the PWM2 wave is switched in a phase delta =60 degrees/n in the adjacent PWM period, and the PWM3 wave is switched in a phase gamma =120 degrees/n in the adjacent PWM period;
wherein T is a set time required for completing the switching, T pwm For PWM period, n = T/T pwm 。
Compared with the prior art, the air conditioner provided by the application has the following advantages and beneficial effects:
(1) The input current for switching the channels is combined with the temperature of the switching power device, and each threshold current is corrected through the temperature, so that the thermal stress concentration of the multi-channel PFC circuit is avoided, and the service life and the reliability of the multi-channel PFC circuit are improved;
(2) When the number of the channels is switched, the phase between the channels is gradually increased and decreased without direct jump of the phase between the channels, so that the damage of a PFC circuit caused by current overshoot in the channels is avoided, and the use reliability of the air conditioner is improved.
Other features and advantages of the present invention will become more apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings.
Drawings
In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings required to be used in the embodiments are briefly described below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and it is obvious for those skilled in the art to obtain other drawings based on the drawings without creative efforts.
Fig. 1 is a schematic structural diagram of a dual-channel PFC circuit in an embodiment of an air conditioner according to the present invention;
fig. 2 is a schematic structural diagram of a three-channel PFC circuit in an embodiment of an air conditioner according to the present invention;
fig. 3 is a PWM1 waveform, a PWM2 waveform, an L1 upper inductor current iL1 waveform, and an L2 upper inductor current iL2 waveform when the multi-channel PFC circuit switches from a single channel to a dual channel in the embodiment of the air conditioner according to the present invention;
fig. 4 is a PWM1 waveform, a PWM2 waveform, an iL1 waveform of the inductor current on L1 and an iL2 waveform of the inductor current on L2 when the multi-channel PFC circuit switches from the dual channel to the single channel in the embodiment of the air conditioner according to the present invention;
fig. 5 shows a PWM1 waveform, a PWM2 waveform, a PWM3 waveform, an L1 inductor current iL1 waveform, an L2 inductor current iL2 waveform, and an L3 inductor current iL3 waveform when the multi-channel PFC circuit switches from two channels to three channels in the embodiment of the air conditioner according to the present invention;
fig. 6 shows a PWM1 waveform, a PWM2 waveform, a PWM3 waveform, an L1 inductor current iL1 waveform, an L2 inductor current iL2 waveform, and an L3 inductor current iL3 waveform of the multi-channel PFC circuit switched from three channels to two channels in the air conditioner according to the embodiment of the present invention.
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. In the description of the present invention, it is to be understood that the terms "center", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", etc. indicate orientations or positional relationships based on those shown in the drawings, and are merely for convenience of description and simplicity of description, and do not indicate or imply that the devices or elements referred to must have a particular orientation, be constructed in a particular orientation, and be operated, and thus, are not to be construed as limiting the present invention.
In the description of the present invention, it should be noted that the terms "mounted," "connected," and "connected" are to be construed broadly and may be, for example, fixedly connected, detachably connected, or integrally connected unless otherwise explicitly stated or limited. The specific meanings of the above terms in the present invention can be understood in a specific case to those of ordinary skill in the art. In the foregoing description of embodiments, the particular features, structures, materials, or characteristics may be combined in any suitable manner in any one or more embodiments or examples.
The terms "first", "second" and "first" are used for descriptive purposes only and are not to be construed as indicating or implying relative importance or to implicitly indicate the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of the present invention, "a plurality" means two or more unless otherwise specified.
Basic operation principle of air conditioner
The present embodiment provides an air conditioner that performs a cooling and heating cycle of the air conditioner by using a compressor, a condenser, an expansion valve, and an evaporator. The cooling and heating cycle includes a series of processes involving compression, condensation, expansion, and evaporation to cool or heat an indoor space.
The low-temperature and low-pressure refrigerant enters the compressor, the compressor compresses the refrigerant gas in a high-temperature and high-pressure state, and the compressed refrigerant gas is discharged. The discharged refrigerant gas flows into the condenser. The condenser condenses the compressed refrigerant into a liquid phase, and the heat is released to the surrounding environment through the condensation process.
The expansion valve expands the high-temperature and high-pressure liquid-phase refrigerant condensed in the condenser into a low-pressure liquid-phase refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the refrigerant gas in a low-temperature and low-pressure state to the compressor. The evaporator can achieve a refrigerating effect by heat exchange with a material to be cooled using latent heat of evaporation of a refrigerant. The air conditioner can adjust the temperature of the indoor space throughout the cycle.
The outdoor unit of the air conditioner refers to a portion of a refrigeration cycle including a compressor, an outdoor heat exchanger, and an outdoor fan, the indoor unit of the air conditioner includes a portion of an indoor heat exchanger and an indoor fan, and a throttling device (e.g., a capillary tube or an electronic expansion valve) may be provided in the indoor unit or the outdoor unit.
The indoor heat exchanger and the outdoor heat exchanger serve as a condenser or an evaporator. The air conditioner performs a heating mode when the indoor heat exchanger serves as a condenser, and performs a cooling mode when the indoor heat exchanger serves as an evaporator.
The indoor heat exchanger and the outdoor heat exchanger are switched to be used as a condenser or an evaporator, a four-way valve is generally adopted, and specific reference is made to the arrangement of a conventional air conditioner, which is not described herein again.
The refrigeration working principle of the air conditioner is as follows: the compressor works to enable the interior of the indoor heat exchanger (an evaporator at the moment in the indoor unit) to be in an ultralow-pressure state, liquid refrigerant in the indoor heat exchanger is rapidly evaporated to absorb heat, air blown out by the indoor fan is cooled through the coil pipe of the indoor heat exchanger to become cold air which is blown into a room, the evaporated and vaporized refrigerant is compressed by the compressor, is condensed into liquid in a high-pressure environment in the outdoor heat exchanger (a condenser at the moment in the outdoor unit) to release heat, and the heat is dissipated into the atmosphere through the outdoor fan, so that the refrigeration effect is achieved through circulation.
The heating working principle of the air conditioner is as follows: the gaseous refrigerant is pressurized by the compressor to become high-temperature and high-pressure gas, and the high-temperature and high-pressure gas enters the indoor heat exchanger (the condenser at the moment), is condensed, liquefied and released heat to become liquid, and simultaneously heats indoor air, so that the aim of increasing the indoor temperature is fulfilled. The liquid refrigerant is decompressed by the throttling device, enters the outdoor heat exchanger (an evaporator at the moment), is evaporated, gasified and absorbs heat to form gas, absorbs heat of outdoor air (the outdoor air becomes cooler) to form gaseous refrigerant, and enters the compressor again to start the next cycle.
Multi-channel PFC circuit
The multi-channel PFC circuit comprises a plurality of PFC channels connected in parallel and is used for carrying out power factor correction on an input current waveform.
Referring to fig. 1, a schematic diagram of a dual channel PFC circuit is shown.
The two-channel PFC circuit comprises two parallel PFC channels, wherein the first channel comprises a first inductor L1, a first switching power device Q1, a first diode D1 and a first resistor R1, and the second channel comprises a second inductor L2, a second switching power device Q2, a second diode D2 and a second resistor R2.
Referring to fig. 2, a schematic diagram of a three-channel PFC circuit is shown.
The three-channel PFC circuit comprises three parallel PFC channels, wherein the first channel comprises a first inductor L1, a first switching power device Q1, a first diode D1 and a first resistor R1, the second channel comprises a second inductor L2, a second switching power device Q2, a second diode D2 and a second resistor R2, and the third channel comprises a third inductor L3, a third switching power device Q3, a third diode D3 and a third resistor R3.
Referring to fig. 1 and 2, the front ends of the two-channel PFC circuit and the three-channel PFC circuit are both provided with a rectification circuit DM1, and the rear ends are both provided with an electrolytic capacitor C1.
The input terminal of the rectifier circuit DM1 is connected to the single-phase AC power supply AC, and the rectifier circuit DM1 is configured to rectify the single-phase AC power supplied from the single-phase AC power supply AC to obtain a rectified dc power.
The rectifying circuit DM1 may be a single-phase bridge rectifier bridge formed by four diodes.
The multi-channel PFC circuit is connected between the output end of the rectifying circuit DM1 and the electrolytic capacitor C1.
The electrolytic capacitor C1 is connected in parallel with a load, wherein the load can be an air conditioner outdoor unit compressor, and the outdoor unit compressor is subjected to frequency conversion control by adopting an IPM (Intelligent Power Module).
That is, the single-phase AC power AC is subjected to uncontrollable full-wave rectification by the rectification circuit DM1, and then is output to the large-capacity electrolytic capacitor C1 through the multi-channel PFC circuit, thereby supplying power to the load.
Each channel controls the switching power device through the PWM signal output by the processing unit 10 and the corresponding driving circuit, so as to drive and control the channel to be turned on.
In the prior art, the scheme for controlling each channel in the multi-channel PFC circuit by the processing unit 10 mainly adopts a double closed-loop control of a current-voltage control loop including an outer-loop voltage loop and an inner-loop current loop.
The effect of the current loop is to force the input current to follow the waveform of the input voltage, in a sinusoidal waveform.
The voltage loop functions to maintain the output voltage at a level higher than the peak value of the input voltage and may function to stabilize the output voltage.
In the application, a double closed loop control scheme of a current-voltage control loop is still adopted for the multi-channel PFC circuit, so that the power factor of the multi-channel PFC circuit is improved.
Input current hysteresis control
In some embodiments of the present application, an input current hysteresis window is introduced to control the number of channel switches based on switching between single, dual and triple channels.
This part is realized by the processing of the processing unit 10.
The first threshold current I1, the second threshold current I2, the third threshold current I3 and the fourth threshold current I4 are sequentially increased, namely I1 is larger than I2 and smaller than I3 and smaller than I4.
Wherein the first, second, third and fourth threshold currents I1, I2, I3, I4 are provided within the processing unit 10.
For convenience of description, a single channel refers to a first channel, a dual channel refers to a first channel and a second channel, and a triple channel refers to a first channel, a second channel, and a third channel.
When the input current Iac is greater than I2, the processing unit 10 is configured to switch the multi-channel PFC circuit from a single channel to a dual channel, i.e., the first channel is switched to the first channel and the second channel.
When the input current Iac is smaller than I1, the processing unit 10 is configured to switch the multi-channel PFC circuit from a dual channel to a single channel, i.e., the first channel and the second channel are switched to the first channel.
When the input current Iac is greater than I4, the processing unit 10 is configured to switch the multi-channel PFC circuit from two channels to three channels, i.e., a first channel and a second channel to a first channel, a second channel, and a third channel.
When the input current Iac is less than I3, the processing unit 10 is configured to switch the multi-channel PFC circuit from three channels to two channels, i.e., the first channel, the second channel, and the third channel are switched to the first channel and the second channel.
Wherein I2 is less than or equal to the maximum current I in single-channel operation Sheet And the maximum current I is not more than I4 during double-channel operation Double is 。
It should be noted that the input current Iac herein refers to a total input current, which is a sum of currents on the channels.
Referring to fig. 1 and 2, the current on the first channel is collected by a resistor R1 connected in series with the first switching power device Q1.
The current on the second channel is acquired through a resistor R2 connected in series with a second switching power device Q2.
And the current on the third channel is acquired through a resistor R3 connected with a third switching power device Q3 in series.
It should be noted that, when the multi-channel PFC circuit is restarted due to protection stop, since no channel is operated at this time, the input current Iac cannot be obtained, and it cannot be determined that several channels should be opened, therefore, the input current Iac is calculated by using the following formula (1).
Iac=Vdc×Idc/Vac （1）
Where Vdc is the dc bus voltage, idc is the dc bus current, and Vac is the input voltage.
Referring to fig. 1 and 2, the dc bus current Idc is sampled using a sampling resistor R4 on the bus.
The input ac voltage may be sampled by a sampling module, for example, an equal proportion of real-time sampling may be performed.
The sampling module can be selected as a voltage division circuit, and the equal proportionality coefficient during sampling is realized by setting the resistance value of the voltage division circuit.
Temperature sensor
In an embodiment of the present application, in order to avoid the thermal stress concentration of the multi-channel PFC circuit in each channel, referring to fig. 1 and 2, in the present application, a temperature sensor 20 is provided for detecting the temperature of the switching power device Q1/Q2/Q3 in the multi-channel PFC circuit.
The temperature sensor 20 is connected to the processing unit 10.
Temperature T here Temperature of It may refer to the average or any maximum temperature of the temperatures of the switching power devices Q1/Q2/Q3.
In some embodiments of the present application, a heat sink (not shown) for the power device may be provided in order to reliably obtain the temperature of the switching power device.
The switching power devices Q1/Q2/Q3 in the multi-channel PFC circuit are arranged on the heat radiating fin, and the temperature sensor is also arranged on the heat radiating fin to detect the temperature of the switching power devices Q1/Q2/Q3.
Temperature T fed back by temperature sensor 20 when the number of channels is switched Temperature of The threshold currents (i.e., I1 to I4) as described above are corrected, thereby controlling the switching of the number of channels.
This part is against the temperature T Temperature of the water Is also implemented by processing by the processing unit 10.
In some embodiments of the present application, at least one temperature threshold is also provided, each temperature threshold being provided in the processing unit 10.
(1) A temperature threshold is set, for example, denoted as a first high temperature T1.
At a temperature T Temperature of When the first high temperature T1 is greater than or equal to the first high temperature T1, the first threshold current I1, the second threshold current I2, the third threshold current I3, and the fourth threshold current I4 are sequentially decreased by a first current difference Δ I1.
Thus, the number of channels to be switched is controlled according to the corrected threshold current.
The corrected first threshold current is I1' = I1- Δ I1; the corrected second threshold current is I2'= I2-' Δ I1; the corrected third threshold current is I3' = I3- < I1; the corrected fourth threshold current is I4' = I4- Δ I1.
Then, the number of channels is switched by the input current hysteresis control method as described above based on the corrected threshold currents I1', I2', I3', and I4' and the input current Iac.
(2) Two temperature thresholds are set, for example, a first high temperature T1 and a second high temperature T2, where T1 < T2.
At a temperature T Temperature of the water When the first high temperature T1 is greater than or equal to the first high temperature T1, the first threshold current I1, the second threshold current I2, the third threshold current I3, and the fourth threshold current I4 are sequentially decreased by a first current difference Δ I1.
At a temperature T Temperature of the water When the first high temperature T2 is greater than or equal to the second high temperature T2, the first threshold current I1, the second threshold current I2, the third threshold current I3, and the fourth threshold current I4 are sequentially decreased by a second current difference Δ I2.
Wherein Δ I1 <. DELTA.I 2.
(3) Three temperature thresholds are set, for example, a first high temperature T1, a second high temperature T2, and a third high temperature T3, where T1 < T2 < T3.
At a temperature T Temperature of When the first high temperature T1 is greater than or equal to the first high temperature T1, the first threshold current I1, the second threshold current I2, the third threshold current I3, and the fourth threshold current I4 are sequentially decreased by a first current difference Δ I1.
At a temperature T Temperature of the water When the first high temperature T2 is greater than or equal to the second high temperature T2, the first threshold current I1, the second threshold current I2, the third threshold current I3, and the fourth threshold current I4 are sequentially decreased by a second current difference Δ I2.
At a temperature T Temperature of When the first high temperature T3 is greater than or equal to the second high temperature T3, the first threshold current I1, the second threshold current I2, the third threshold current I3, and the fourth threshold current I4 are sequentially decreased by a second current difference Δ I3.
Wherein, delta I1 <. DELTA.I 2 <. DELTA.I 3.
Similarly, more than three temperature thresholds may be provided.
The temperature T can be acquired at intervals in the working process of the multi-channel PFC circuit Temperature of the water The threshold current is corrected.
Passing through temperature T Temperature of the water The threshold current is corrected to control the number of channels, so that the concentrated thermal stress of a certain channel or certain channels is avoided, and the reliable operation of the multi-channel PFC circuit is ensured.
Phase conversion and duty cycle adjustment
As is well known, referring to fig. 1, when the multi-channel PFC circuit operates in dual channels, the PWM1 wave for controlling the switching power device Q1 on the first channel and the PWM2 wave for controlling the switching power device Q2 on the second channel are different from each other by a phase angle of 180 degrees.
The duty ratio of the PWM1 wave and the duty ratio of the PWM2 wave are determined by the control of the first channel and the second channel by the current-voltage control loop respectively.
Referring to fig. 2, in three-channel operation of the multi-channel PFC circuit, the PWM1 wave for controlling the switching power device Q1 on the first channel, the PWM2 wave for controlling the switching power device Q2 on the second channel, and the PWM3 wave for controlling the switching power device Q3 on the third channel are mutually different by a phase angle of 120 degrees.
And the duty ratio of the PWM1 wave, the duty ratio of the PWM2 wave and the duty ratio of the PWM3 wave are respectively determined by the control of the current-voltage control loop on the first channel, the second channel and the third channel.
In some embodiments of the present application, in order to avoid a large current surge when switching the number of channels (increasing or decreasing the number of channels), the processing unit 10 performs switching in a control manner of gradually increasing or decreasing the inter-channel phase while adjusting the duty ratio.
The setting completes the channel switching within a set time T, for example, single channel to dual channel switching, dual channel to three channel switching, dual channel to single channel switching, and three channel to dual channel switching.
The PWM periods Tpwm for the PWM1 wave, the PWM2 wave and the PWM3 wave on the switching power devices Q1, Q2 and Q3, respectively, are the same.
Therefore, in the process of gradually increasing or decreasing the inter-channel phase, n = T/Tpwm times are required to complete the inter-channel phase switching, that is, to complete the single-channel to dual-channel phase switching, the dual-channel to three-channel phase switching, the dual-channel to single-channel phase switching, and the three-channel to dual-channel phase switching.
< switching between Single channel and Dual channel >
As is well known, the PWM1 waveform and the PWM2 waveform are different from each other by a phase angle of 180 degrees when the dual-channel PFC circuit operates normally.
When the multi-channel PFC circuit is switched from a single channel to a double channel, the PWM2 wave is all low level at the beginning, and the phase between the channels is gradually converted, so that the phase angle between the PWM1 wave and the PWM2 wave is 180 degrees different.
When the multi-channel PFC circuit is switched from a double channel to a single channel, the duty ratio of the PWM2 wave is gradually adjusted to 0 by gradually converting the phase between the channels.
In the present application, when the multi-channel PFC circuit switches between a single channel and a dual channel, phase 180 degree conversion can be achieved only after n (i.e., n = T/Tpwm) phase conversions are required.
As such, the phase β =180 degrees/n that needs to be switched in two adjacent PWM periods.
The process of switching the phase is also the process of adjusting the duty cycle.
Assuming n =4, 4 phase 180 degree transitions need to be completed.
(1) When the multi-channel PFC circuit is switched from a single channel to a double channel, the phase difference is converted by 180 degrees, and meanwhile the PWM2 waveform is adjusted from the duty ratio of 0 to the normal duty ratio.
It should be noted that the normal duty cycle indicates a duty cycle of a PWM2 waveform controlled by a current-voltage control loop to a dual-channel PFC circuit.
Fig. 3 shows a PWM1 waveform, a PWM2 waveform, an inductor current iL1 waveform on L1, and an inductor current iL2 waveform on L2 when the multi-channel PFC circuit switches from single channel to dual channel at n = 4.
Referring to fig. 3, initially, the PWM2 waveform is low and the duty cycle is 0.
At n =4, β =180 degrees/4 =45 degrees.
For four consecutive PWM periods, at 180 degrees from the beginning of the rising edge of the PWM1 waveform in the first PWM period, the PWM2 waveform remains low 4 β for the PWM period,
at 180 degrees from the beginning of the rising edge of the PWM1 waveform in the second PWM period, the PWM2 waveform remains low 3 β for the PWM period.
At 180 degrees from the beginning of the rising edge of the PWM1 waveform in the third PWM period, the PWM2 waveform remains at the low level 2 β for the PWM period.
At 180 degrees from the start of the rising edge of the PWM1 waveform in the fourth PWM period, the PWM2 waveform remains at the low level β for the PWM period.
In this way, at 180 degrees from the start of the rising edge of the PWM1 waveform in the fifth PWM period, the PWM2 waveform assumes a high level rising edge, achieving a phase difference of 180 degrees from the PWM1 waveform, and at the same time adjusting the duty cycle of the PWM2 waveform from 0 to the normal duty cycle.
Thereafter, the PWM2 waveform is normally controlled by the current-voltage control loop, and the inductor current iL2 waveform on L2 also appears similar to the inductor current iL1 waveform.
In adjacent four PWM periods, the low level of the PWM2 waveform is gradually decreased, i.e., the high level is gradually increased, at 180 degrees from the start of the rising edge of the PWM1 waveform in the PWM period.
(2) When the multi-channel PFC circuit is switched from a double channel to a single channel, the phase difference is converted by 180 degrees, and meanwhile the PWM2 waveform is adjusted from a normal duty ratio to a 0 duty ratio.
It should be noted that the normal duty cycle indicates a duty cycle of a PWM2 waveform controlled by a current-voltage control loop to a dual-channel PFC circuit.
Fig. 4 shows a PWM1 waveform, a PWM2 waveform, an inductor current iL1 waveform on L1, and an inductor current iL2 waveform on L2 when the multi-channel PFC circuit switches from the dual channel to the single channel at n = 4.
Referring to fig. 4, initially, the PWM1 waveform and the PWM2 waveform are 180 degrees out of phase and are both normal duty cycle controls.
For four consecutive PWM periods, the PWM2 waveform is controlled to transition to the low level β during the PWM period, beginning 180 degrees from the rising edge of the PWM1 waveform during the first PWM period.
At 180 degrees from the beginning of the rising edge of the PWM1 waveform in the second PWM period, the PWM2 waveform is controlled to transition to the low level 2 β during the PWM period.
At 180 degrees from the beginning of the rising edge of the PWM1 waveform in the third PWM period, the PWM2 waveform is controlled to transition to a low level 3 β during the PWM period.
At 180 degrees from the start of the rising edge of the PWM1 waveform in the fourth PWM period, the PWM2 waveform is controlled to transition to the low level 4 β during the PWM period.
As such, at 180 degrees from the start of the rising edge of the PWM1 waveform in the fifth PWM period, the PWM2 waveform assumes a low level, and at the same time the duty cycle of the PWM2 waveform falls to 0.
Thereafter, the PWM1 waveform is still normally controlled by the current-voltage control loop, and the inductor current iL2 waveform on L2 is gradually decreased to 0.
In adjacent four PWM periods, the low level of the PWM2 waveform is gradually increased from the start of the rising edge of the PWM1 waveform in the PWM period to 180 degrees.
< switching between Dual channel and three channels >
As is well known, the PWM1 waveform and the PWM2 waveform are different from each other by 180 degrees in phase angle when the dual-channel PFC circuit normally operates, and the PWM1 waveform, the PWM2 waveform and the PWM3 waveform are different from each other by 120 degrees in phase angle when the three-channel PFC circuit normally operates.
Before the multi-channel PFC circuit is switched from the two channels to the three channels, the phase angle of 180 degrees is mutually differed between the PWM1 waveform and the PWM2 waveform, the PWM3 waveform is just at a low level, and after the switching is completed by gradually converting the phase between the channels, the phase angle of 120 degrees is mutually differed between the PWM1 waveform, the PWM2 waveform and the PWM3 waveform.
When the multi-channel PFC circuit is switched from three channels to two channels, the phase angle of 180 degrees is made to be different between the PWM1 waveform and the PWM2 waveform by gradually converting the phase between the channels, and the duty ratio of the PWM3 waveform is gradually reduced to 0.
In this application, when the multi-channel PFC circuit switches between the two channels and the three channels, the second channel can be switched between 120 degrees and 180 degrees of phase after n (i.e., n = T/Tpwm) phase conversions are required relative to the first channel, and the third channel is switched between 240 degrees and 360 degrees of phase.
As such, for the second channel, the phase δ = (180-120 degrees)/n that needs to be converted in two adjacent PWM periods; for the third channel, the phase γ = (360-240 degrees)/n that needs to be converted in two adjacent PWM periods.
The process of switching the phase is also the process of adjusting the duty cycle.
Assuming n =4, the second channel needs 4 times to complete the phase transition between 120 degrees and 180 degrees, and the third channel needs 4 times to complete the phase transition between 240 degrees and 360 degrees.
(1) When the multi-channel PFC circuit is switched from the two channels to the three channels, the second channel is switched between phases of 120 degrees and 180 degrees, the third channel is switched between phases of 240 degrees and 360 degrees, and adjustment of the PWM3 waveform from the duty ratio of 0 to the normal duty ratio is realized.
Note that the normal duty ratio indicates the duty ratio of the PWM3 waveform controlled by the current-voltage control loop to the two-channel PFC circuit.
Fig. 5 shows a PWM1 waveform, a PWM2 waveform, a PWM3 waveform, an inductor current iL1 waveform on L1, an inductor current iL2 waveform on L2, and an inductor current iL3 waveform on L3 when the multi-channel PFC circuit switches from dual channel to three channel when n = 4.
Referring to fig. 5, initially, the PWM3 waveform is low and the duty cycle is 0.
δ = (180-120 degrees)/4 =15 degrees when n = 4; γ = (360 degrees-240 degrees)/4 =30 degrees.
Referring to fig. 5, the PWM2 waveform is advanced by δ from the start of the rising edge of the PWM1 waveform in the first PWM period to the rising edge at 180 degrees for four consecutive PWM periods.
The PWM2 waveform is advanced by 2 δ from the start of the rising edge of the PWM1 waveform in the second PWM period to the rising edge at 180 degrees.
The PWM2 waveform is 3 δ advanced in advance of the rising edge at 180 degrees from the beginning of the rising edge of the PWM1 waveform in the third PWM period.
The PWM2 waveform is advanced by 4 δ from the start of the rising edge of the PWM1 waveform in the fourth PWM period to the rising edge at 180 degrees.
Thereafter, the phase difference between the PWM2 waveform and the PWM1 waveform is 120 degrees.
For four consecutive PWM periods, at 240 degrees from the rising edge of the PWM1 waveform in the first PWM period, the PWM3 waveform remains low for 4 γ during the PWM period.
At 240 degrees from the beginning of the rising edge of the PWM1 waveform in the second PWM period, the PWM3 waveform remains low 3 γ for the PWM period.
At 240 degrees from the rising edge of the PWM1 waveform in the third PWM period, the PWM3 waveform remains at the low level 2 γ for the PWM period.
At 240 degrees from the start of the rising edge of the PWM1 waveform in the fourth PWM period, the PWM3 waveform remains at the low level γ for the PWM period.
In this manner, at 2400 degrees from the rising edge of the PWM1 waveform in the fifth PWM period, the PWM3 waveform assumes a high level rising edge, achieves a phase difference of 120 degrees from the PWM1 waveform, and at the same time adjusts the duty ratio of the PWM3 waveform from 0 to the normal duty ratio.
Thereafter, the PWM3 waveform is normally controlled by the current-voltage control loop, and the inductor current iL3 waveform on L3 also appears similar to the inductor current iL1/iL2 waveform.
(2) When the multi-channel PFC circuit is switched from three channels to two channels, the second channel is switched between 120-degree and 180-degree phases, the third channel is switched between 240-degree and 360-degree phases, and meanwhile the PWM3 waveform is adjusted from a normal duty ratio to a 0 duty ratio.
It should be noted that the normal duty cycle indicates the duty cycle of the PWM3 waveform controlled by the current-voltage control loop to the dual-channel PFC circuit.
Fig. 6 shows a PWM1 waveform, a PWM2 waveform, a PWM3 waveform, an inductor current iL1 waveform on L1, an inductor current iL2 waveform on L2, and an inductor current iL3 waveform on L3 when the multi-channel PFC circuit switches from three channels to two channels at n = 4.
Referring to fig. 6, initially, the PWM1 waveform, the PWM2 waveform and the PWM2 waveform are different from each other by a phase angle of 120 degrees, and are all normal duty control.
Referring to fig. 6, for four consecutive PWM periods, the PWM2 waveform is shifted back by δ from the rising edge of the PWM1 waveform in the first PWM period to a rising edge at 120 degrees.
The PWM2 waveform is shifted back by 2 δ from the start of the rising edge of the PWM1 waveform in the second PWM period to the rising edge at 120 degrees.
The PWM2 waveform is shifted back by 3 δ from the start of the rising edge of the PWM1 waveform in the third PWM period to the rising edge at 120 degrees.
The PWM2 waveform is shifted back by 4 δ from the start of the rising edge of the PWM1 waveform in the fourth PWM period to the rising edge at 120 degrees.
Thereafter, the phase difference between the PWM2 waveform and the PWM1 waveform is 180 degrees.
Thereafter, the PWM2 waveform is still normally controlled by the current-voltage control loop.
For four consecutive PWM periods, the PWM3 waveform is controlled to transition to the low level γ during the PWM period at 240 degrees from the rising edge of the PWM1 waveform during the first PWM period.
The PWM3 waveform is controlled to transition to the low level 2 γ during the PWM period at 240 degrees from the beginning of the rising edge of the PWM1 waveform during the second PWM period.
At 240 degrees from the rising edge of the PWM1 waveform in the third PWM period, the PWM3 waveform is controlled to transition to the low level 3 γ in the PWM period.
At 240 degrees from the rising edge of the PWM1 waveform in the fourth PWM period, the PWM3 waveform is controlled to transition to the low level 4 γ in the PWM period.
As such, at 240 degrees from the start of the rising edge of the PWM1 waveform in the fifth PWM period, the PWM3 waveform assumes a low level, and at the same time the duty cycle of the PWM3 waveform falls to 0.
Thereafter, the PWM1 waveform and the PWM2 waveform are still normally controlled by the current-voltage control loop, and the inductor current iL3 waveform on L3 is gradually decreased to 0.
This application air conditioner when multichannel PFC circuit carries out the channel and switches, through increasing and decreasing phase place between the channel gradually, slows down the electric current that switches the passageway gradually, avoids producing the electric current impact on the passageway, burns out switching power device, shortens multichannel PFC circuit's life, reduces multichannel PFC circuit and air conditioner's use reliability.
It should be noted that if the time T required for completing the switching is relatively large, the number of times n indicating that the switching is required is also relatively large, and the power supply cycle may be divided into a plurality of power supply cycles T in order to softly increase or decrease the current generated when switching the channel Period of time To complete the handover.
Number of power supply cycles M = T/T Period of time . Each ofOne power supply period T Period of time The number of times n' = T of required switching Period of time /Tpwm。
The above examples are only intended to illustrate the technical solution of the present invention, but not to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, it will be apparent to those skilled in the art that modifications may be made to the embodiments described in the foregoing embodiments, or equivalents may be substituted for some of the features thereof; and such modifications or substitutions do not depart from the spirit and scope of the corresponding technical solutions.
Claims (9)
1. An air conditioner, comprising:
a refrigerant circulation circuit for circulating a refrigerant through a refrigerant line in which the compressor, the condenser, the throttle element, the evaporator and the four-way valve are communicated;
a multi-channel PFC circuit including a plurality of PFC channels connected in parallel;
the temperature sensor is used for detecting the temperature of a switching power device in the multi-channel PFC circuit;
a processing unit configured to:
acquiring the input current of the multichannel PFC circuit;
according to the input current and the number of the switching channels of the plurality of threshold currents, correcting the threshold currents through the temperature fed back by the temperature sensor;
when the number of channels is switched, relative to the PWM1 waveform of the first channel, when the single channel and the double channels are switched, the phase between the channels is gradually increased and decreased, so that a phase angle of 180 degrees is gradually different between the two channels, when the first channel and the second channel work and the first channel, the second channel and the third channel work, the phase between the channels is gradually increased and decreased, so that phase conversion between 120 degrees and 180 degrees is gradually completed between the PWM1 waveform of the first channel and the PWM2 waveform of the second channel, and phase conversion between 240 degrees and 360 degrees is gradually completed between the PWM1 waveform of the first channel and the PWM3 waveform of the third channel.
2. The air conditioner according to claim 1, wherein the number of channels is switched according to the input current and a plurality of threshold currents, specifically:
when the input current is larger than a second threshold current, the multi-channel PFC circuit is switched from a single channel to a double channel;
when the input current is smaller than a first threshold current, the multi-channel PFC circuit is switched from a dual-channel state to a single-channel state;
when the input current is larger than a fourth threshold current, the multi-channel PFC circuit is switched from a double channel to a three channel;
when the input current is smaller than a third threshold current, the multi-channel PFC circuit is switched from three channels to two channels;
each threshold current includes a first threshold current, a second threshold current, a third threshold current, and a fourth threshold current that increase in sequence.
3. The air conditioner according to claim 2, wherein each threshold current is corrected by the temperature fed back by the temperature sensor, specifically:
when the temperature is higher than or equal to a first high temperature, the first threshold current, the second threshold current, the third threshold current and the fourth threshold current are sequentially reduced by a first current difference value;
when the temperature is higher than or equal to a second high temperature, the first threshold current, the second threshold current, the third threshold current and the fourth threshold current are sequentially reduced by a second current difference value;
the first high temperature is less than the second high temperature, and the first current difference is less than the second current difference.
4. The air conditioner according to claim 1,
setting the switching power devices on three channels in the multi-channel PFC circuit on the heat dissipation sheet;
the temperature sensor is arranged on the heat sink.
5. The air conditioner according to any one of claims 1 to 4, wherein the input current is calculated as follows:
the input current Iac = Vdc × Idc/Vac;
where Vdc is the dc bus voltage, idc is the dc bus current, and Vac is the input voltage.
6. The air conditioner according to claim 1, wherein when switching between single channel and dual channel, the inter-channel phase is gradually increased or decreased to gradually complete a 180 degree phase difference between the two channels, specifically:
when the multi-channel PFC circuit is switched between a single channel and two channels, the PWM wave of the channel to be switched on or off is switched at the phase beta =180 degrees/n in the adjacent PWM period;
wherein T is a set time required for completing the switching, T pwm For PWM period, n = T/T pwm 。
7. The air conditioner of claim 6, wherein the PWM2 wave switches phase β between adjacent PWM cycles when the multi-channel PFC circuit switches from first channel operation to both first and second channel operation.
8. The air conditioner as claimed in claim 6, wherein when the multi-channel PFC circuit switches from the first channel and the second channel to the first channel, the PWM2 wave switches the phase β at the adjacent PWM period, and when the switching is completed, the duty ratio of the PWM2 wave is adjusted to 0.
9. The air conditioner according to claim 1, wherein when switching between the operation of the first channel and the second channel and the operation of the first channel, the operation of the second channel, and the operation of the third channel, the inter-channel phase is gradually increased or decreased, so that the phase transition between 120 degrees and 180 degrees is gradually completed between the PWM1 waveform and the PWM2 waveform, and the phase transition between 240 degrees and 360 degrees is gradually completed between the PWM1 waveform and the PWM3 waveform, specifically:
when the multi-channel PFC circuit is switched among the first channel, the second channel and the third channel, the PWM2 wave is switched in a phase delta =60 degrees/n in the adjacent PWM period, and the PWM3 wave is switched in a phase gamma =120 degrees/n in the adjacent PWM period;
wherein T is the set time required for completing the switching, T pwm For PWM period, n = T/T pwm 。
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| CN202210004658.4A CN114322228B (en) | 2022-01-05 | 2022-01-05 | Air conditioner |
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| CN202210004658.4A CN114322228B (en) | 2022-01-05 | 2022-01-05 | Air conditioner |
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| DE69013660T2 (en) * | 1989-12-25 | 1995-03-02 | Matsushita Electric Works Ltd | Inverter device. |
| KR101870719B1 (en) * | 2011-10-14 | 2018-06-25 | 엘지전자 주식회사 | Power converter apparatus and air conditioner having the apparatus |
| DE102014215312A1 (en) * | 2014-08-04 | 2016-02-04 | Robert Bosch Gmbh | Control device for an air conditioning device |
| CN104953854A (en) * | 2015-06-19 | 2015-09-30 | 广东美的制冷设备有限公司 | Variable-frequency air conditioner, power circuit of outdoor unit of variable-frequency air conditioner and PFC (power factor correction) control method |
| CN108768153A (en) * | 2018-05-25 | 2018-11-06 | 青岛海尔空调电子有限公司 | The management method and equipment of number of channels are run in multiphase interleaving PFC circuit |
| CN110677032A (en) * | 2019-10-21 | 2020-01-10 | 宁波奥克斯电气股份有限公司 | Current sharing control method and device for staggered parallel PFC circuit and air conditioner |
| CN111490684A (en) * | 2020-05-19 | 2020-08-04 | 湘潭大学 | Network side power factor and harmonic suppression strategy of isolated AC-DC matrix converter |
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