CN111525787B - PFC control method and device, air conditioner and storage medium - Google Patents

PFC control method and device, air conditioner and storage medium Download PDF

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CN111525787B
CN111525787B CN202010493868.5A CN202010493868A CN111525787B CN 111525787 B CN111525787 B CN 111525787B CN 202010493868 A CN202010493868 A CN 202010493868A CN 111525787 B CN111525787 B CN 111525787B
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duration
turn
time length
output voltage
pfc
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CN111525787A (en
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韩亚
李超
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Ningbo Aux Electric Co Ltd
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Ningbo Aux Electric Co Ltd
Zhuhai Tuoxin Technology Co Ltd
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M1/00—Details of apparatus for conversion
    • H02M1/42—Circuits or arrangements for compensating for or adjusting power factor in converters or inverters
    • H02M1/4208—Arrangements for improving power factor of AC input
    • H02M1/4225—Arrangements for improving power factor of AC input using a non-isolated boost converter
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/62—Control or safety arrangements characterised by the type of control or by internal processing, e.g. using fuzzy logic, adaptive control or estimation of values
    • F24F11/63—Electronic processing
    • F24F11/64—Electronic processing using pre-stored data
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F24—HEATING; RANGES; VENTILATING
    • F24F—AIR-CONDITIONING; AIR-HUMIDIFICATION; VENTILATION; USE OF AIR CURRENTS FOR SCREENING
    • F24F11/00—Control or safety arrangements
    • F24F11/88—Electrical aspects, e.g. circuits
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Signal Processing (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Fuzzy Systems (AREA)
  • Mathematical Physics (AREA)
  • Power Engineering (AREA)
  • Rectifiers (AREA)

Abstract

The invention provides a PFC control method, a PFC control device, an air conditioner and a storage medium, and relates to the technical field of air conditioners, wherein zero crossing point detection is carried out on output voltage of a rectifier bridge, when the zero crossing point of the output voltage is detected, the current compressor frequency of the air conditioner is obtained, and then a target turn-off duration corresponding to the current compressor frequency is obtained; then, in each output voltage period of the rectifier bridge, an average current control strategy is adopted in a first time length and a second time length, a passive PFC control strategy is adopted in a target turn-off time length to naturally rectify the rectifier bridge, and the power device is always in a turn-off state, wherein the first time length, the target turn-off time length and the second time length are sequentially continuous and occupy one output voltage period, and meanwhile the first time length and the second time length are equal. Therefore, the switching frequency of the power device is reduced, the loss of the power device is reduced, and the service life of the air conditioner is prolonged while the high power factor is ensured.

Description

PFC control method and device, air conditioner and storage medium
Technical Field
The invention relates to the technical field of air conditioners, in particular to a PFC control method and device, an air conditioner and a storage medium.
Background
Currently, active PFC (Power Factor Correction) is widely used due to its advantages of high Power Factor, small harmonic current, stable output voltage, and the like.
The control strategies commonly used for active PFC include peak, hysteresis, average current, and single cycle control. Taking average current control as an example, the current loop has a higher gain bandwidth, which can cause tracking error to generate small distortion, so that a higher power factor (the power factor is close to 1) can be obtained, and meanwhile, the current loop also has the advantages of high stability, insensitivity to noise and the like, so that the current loop is widely applied to an external unit controller of an air conditioner.
The Boost type average current method realizes power factor correction by controlling average current to be in phase with input voltage, and the fluctuation of the input voltage is usually large, so that power devices in a PFC circuit are frequently switched, the loss of the power devices is greatly increased, and the service life of an air conditioner is influenced.
Disclosure of Invention
The invention solves the technical problems that the loss of a power device is increased and the service life of an air conditioner is influenced because the power device is frequently switched on and switched off by the conventional Boost type average current method.
In order to solve the above problems, the present invention provides a PFC control method applied to an external unit controller of an air conditioner, the external unit controller including a power supply device including a rectifier bridge and a power factor correction PFC circuit; the PFC control method comprises the following steps: when the zero crossing point of the output voltage of the rectifier bridge is detected, acquiring the current compressor frequency of the air conditioner; obtaining a target turn-off duration corresponding to the current compressor frequency; calculating a first time length and a second time length according to the target turn-off time length and the output voltage period of the rectifier bridge, wherein the first time length, the target turn-off time length and the second time length are sequentially continuous and occupy one output voltage period, and the first time length and the second time length are equal; controlling the on-off of a power device of the PFC circuit by adopting an average current control strategy in the first time period and the second time period; and naturally rectifying the rectifier bridge by adopting a passive PFC control strategy within the target turn-off duration to control the turn-off of a power device of the PFC circuit.
Compared with the prior art, the PFC control method provided by the invention has the following advantages: detecting the zero crossing point of the output voltage of the rectifier bridge, and acquiring the current compressor frequency of the air conditioner when the zero crossing point of the output voltage is detected, so as to acquire a target turn-off duration corresponding to the current compressor frequency; then, in an output voltage period of the rectifier bridge, an average current control strategy is adopted in a first time period and a second time period, a passive PFC control strategy is adopted in a target turn-off time period to naturally rectify the rectifier bridge, and the power device is always in a turn-off state, wherein the first time period, the target turn-off time period and the second time period are sequentially continuous and occupy one output voltage period, and meanwhile the first time period is equal to the second time period. That is, the present invention improves the control strategy of PFC driving based on the existing Boost type average current method, and because the current distortion is small in the middle time period of the output voltage of the rectifier bridge, the power device is always turned off in the middle time period. Therefore, the switching frequency of the power device is reduced, the loss of the power device is reduced, and the service life of the air conditioner is prolonged while the high power factor is ensured.
Further, the external machine controller stores a data table in advance, wherein the data table comprises a plurality of compressor frequencies and a turn-off duration corresponding to each compressor frequency; the step of obtaining the target turn-off duration corresponding to the current compressor frequency includes: and determining the target turn-off duration corresponding to the current compressor frequency from the data table according to the current compressor frequency.
Further, the data table is generated as follows:
when the frequency of the compressor is a first preset frequency, controlling the on-off of a power device of the PFC circuit by adopting the average current control strategy, and measuring the first driving efficiency of the PFC circuit;
setting an initial value of the turn-off duration;
calculating the first time length and the second time length according to the initial value of the turn-off time length and the output voltage period;
controlling the on-off of a power device of the PFC circuit by adopting the average current control strategy in the first time period and the second time period;
naturally rectifying the rectifier bridge by adopting the passive PFC control strategy within the turn-off duration to control the power device of the PFC circuit to be turned off;
measuring the harmonic content of the outer machine controller and the second driving efficiency of the PFC circuit;
adjusting the initial value of the turn-off duration until the harmonic content meets a preset standard, the second driving efficiency is highest and is lower than the first driving efficiency, and taking the current value of the turn-off duration as the turn-off duration corresponding to the current compressor frequency;
judging whether the frequency of the compressor reaches a second preset frequency or not;
if not, increasing the compressor frequency according to a preset frequency interval, and repeatedly executing the steps until the compressor frequency reaches the second preset frequency, so as to obtain the turn-off duration corresponding to each compressor frequency.
Further, the first preset frequency is 45 Hz-50 Hz, the second preset frequency is 120 Hz-125 Hz, and the preset frequency interval is 10 Hz-15 Hz.
Further, the step of calculating the first duration and the second duration according to the target turn-off duration and the output voltage period of the rectifier bridge includes: according to the target turn-off duration and the output voltage period of the rectifier bridge, according to a preset formula:
T1＝(T-T0)/2
calculating the first time length and the second time length; wherein T1 represents the first and second time periods, T represents the output voltage period, and T0 represents the target OFF time period.
The invention also provides a PFC control device, which is applied to an external machine controller of an air conditioner, wherein the external machine controller comprises a power supply device, and the power supply device comprises a rectifier bridge and a power factor correction PFC circuit; the PFC control device includes: the obtaining module is used for obtaining the current compressor frequency of the air conditioner when the output voltage zero crossing point of the rectifier bridge is detected; the obtaining module is used for obtaining a target turn-off duration corresponding to the current compressor frequency; the calculation module is used for calculating a first time length and a second time length according to the target turn-off time length and the output voltage period of the rectifier bridge, wherein the first time length, the target turn-off time length and the second time length occupy one output voltage period and are sequentially continuous, and the first time length and the second time length are equal; the first execution module is used for controlling the on-off of a power device of the PFC circuit by adopting an average current control strategy in the first time length and the second time length; and the second execution module is used for naturally rectifying the rectifier bridge by adopting a passive PFC control strategy within the target turn-off duration to control the turn-off of a power device of the PFC circuit.
Further, the external machine controller stores a data table in advance, wherein the data table comprises a plurality of compressor frequencies and a turn-off duration corresponding to each compressor frequency; the obtaining module is specifically configured to: and determining the target turn-off duration corresponding to the current compressor frequency from the data table according to the current compressor frequency.
Further, the calculation module is specifically configured to: according to the target turn-off duration and the output voltage period of the rectifier bridge, according to a preset formula:
T1＝(T-T0)/2
calculating the first time length and the second time length; wherein T1 represents the first and second time periods, T represents the output voltage period, and T0 represents the target OFF time period.
The present invention also provides an air conditioner, comprising: an outdoor unit controller; and the memory is used for storing one or more programs, and when the one or more programs are executed by the external unit controller, the external unit controller realizes the PFC control method.
The present invention also provides a computer-readable storage medium having stored thereon a computer program which, when executed by an external unit controller, implements the PFC control method described above.
Drawings
Fig. 1 is a block diagram of an air conditioner according to the present invention.
Fig. 2 is a block diagram illustrating a power supply device in an external unit controller according to the present invention.
Fig. 3 is a control schematic diagram of the Boost type average current method.
Fig. 4 is a waveform diagram of an input voltage and an input current of the PFC circuit in the case of the passive PFC.
Fig. 5 is a schematic flow chart of a PFC control method according to the present invention.
Fig. 6 is a control schematic diagram of the PFC control method according to the present invention.
Fig. 7 is a schematic flow chart of a data table generation method provided by the present invention.
Fig. 8 is a block diagram of a PFC control apparatus according to the present invention.
Description of reference numerals:
10-an air conditioner; 11-an external machine controller; 12-a memory; 13-a bus; 111-a rectifier bridge; 112-a PFC circuit; 100-PFC control means; 110-an obtaining module; 120-an obtaining module; 130-a calculation module; 140-a first execution module; 150-a second execution module.
Detailed Description
In order to make the aforementioned objects, features and advantages of the present invention comprehensible, embodiments accompanied with figures are described in detail below.
Referring to fig. 1, fig. 1 is a block schematic diagram of an air conditioner 10 according to the present invention, in which the air conditioner 10 includes an external unit controller 11, a memory 12 and a bus 13, and the external unit controller 11 is connected to the memory 12 through the bus 13.
The memory 12 is used to store a program, such as the PFC control device 100 shown in fig. 8. The PFC control means 100 comprises at least one software functional block which may be stored in the form of software or firmware in the memory 12. After receiving the execution instruction, the external unit controller 11 executes the program to implement the PFC control method disclosed in the present invention.
The external unit controller 11 may be an integrated circuit chip having signal processing capability. In the implementation process, the steps of the PFC control method may be implemented by an integrated logic circuit of hardware in the external unit controller 11 or by instructions in the form of software. The external Unit controller 11 may be a general-purpose Processor, and includes a Central Processing Unit (CPU), a Network Processor (NP), and the like; but may also be a Digital Signal Processor (DSP), an Application Specific Integrated Circuit (ASIC), an off-the-shelf programmable gate array (FPGA) or other programmable logic device, discrete gate or transistor logic, discrete hardware components.
The outdoor unit controller 11 includes a power supply deviceReferring to fig. 2, the power supply apparatus includes a rectifier bridge 111 and a PFC circuit 112, and a voltage output from the AC power supply is rectified by the rectifier bridge 111 to obtain a rectified output voltage UdI.e. the input voltage U of the PFC circuit 112dThe value is generally obtained by sampling the input voltage sampling circuit. The output voltage Ud of the rectifier bridge 111 is converted into a DC voltage U by a PFC circuit 1120I.e. the output voltage U of the PFC circuit 1120The value is generally obtained by sampling by an output voltage sampling circuit.
The Boost type average current method is applied to the power supply device, and realizes power factor correction by controlling average current to be in phase with input voltage.
The basic principle of the Boost type average current method can be summarized as follows:
first, a reference voltage U is appliedrefAnd the output voltage U of PFC circuit 1120Comparing, and outputting the difference value through a voltage PI regulator;
in the second step, the output of the PI regulator in the previous step and the input voltage U of the PFC circuit 112 are converted by a multiplication simulatordMultiplying to obtain a reference value I of the input currentref；
Thirdly, the inductive current i is measuredLComparing with reference current Iref, sending the comparison value to PWM generator after passing through current PI regulator to generate PWM signal, controlling on-off of switch tube S by PWM signal to make inductive current iLCan well track the output voltage U of the rectifier bridge 111dThe waveform change of the power factor correction circuit greatly reduces current harmonic waves so as to achieve the purpose of improving the power factor.
The carrier frequency of the Boost type average current method is constant all the time, the control principle is shown in fig. 3, and the dotted line in the figure is the average current iAverageThe solid line is the inductor current iL. As can be seen from FIG. 3, when the inductor current iLWhen rising, the duty ratio of the output voltage Ug of the PWM generator is reduced, and the inductive current i is further reducedLDecrease; when the inductor current iLWhen the current drops, the Ug duty ratio output by the PWM generator rises, and the inductive current i is further enabled toLAnd is increased.
In addition, the first and second substrates are,as can be seen from FIG. 2, when the output voltage U of PFC circuit 112 is asserted0When the voltage is reduced, the output of the voltage PI regulator is increased, so that the reference current I is increasedrefIncrease the inductor current iLThe output voltage Ug of the PWM generator is increased; when the output voltage U of the PFC circuit 1120When the output of the voltage PI regulator is increased, the output of the voltage PI regulator is reduced, so that the reference current I is increasedrefReduction of the inductor current iLDecreases, which in turn results in a decrease of the output voltage Ug of the PWM generator.
It is apparent that the output voltage U of PFC circuit 1120Will influence the inductor current iLInductor current iLThe PWM signal is influenced, and the on-off of the switching tube S is further influenced. Output voltage U of PFC circuit 1120The fluctuation of the input voltage is usually large relative to the input voltage (the voltage output by the AC power supply), which causes frequent switching of the power devices inside the PFC circuit, resulting in greatly increased loss of the power devices and affecting the service life of the air conditioner.
When the passive PFC is employed for the power supply apparatus shown in fig. 2, waveforms of an input voltage and an input current of the PFC circuit 112 are shown in fig. 4. As can be seen from fig. 4, the input current of the PFC circuit 112 is a spike wave, since only the input voltage (voltage of the AC power output) of the rectifier bridge 111 is greater than the dc output voltage UdOnly current flows through rectifier bridge 111, which causes a problem that the input voltage and the input current of PFC circuit 112 are out of phase. Therefore, if passive PFC is used, the rectifier bridge 111 is naturally rectified, and the switching tube S is turned off.
In summary, in order to solve the above technical problems in the prior art, the present invention improves a control strategy of PFC driving based on the existing Boost type average current method, combines a passive PFC and the Boost type average current method, and adopts the passive PFC in the middle time period of the output voltage of the rectifier bridge, so that the power device (i.e., the switching tube S) is always turned off, thereby reducing the switching frequency of the power device, reducing the loss of the power device, and increasing the service life of the air conditioner 10, which is described in detail below.
On the basis of the air conditioner 10 shown in fig. 1, a possible implementation manner of a PFC control method is given below, the PFC control method is applied to an external unit controller 11, fig. 5 is a flow chart of the PFC control method provided by the present invention, and referring to fig. 5, the PFC control method may include the following steps:
s101, when the zero crossing point of the output voltage of the rectifier bridge is detected, the current compressor frequency of the air conditioner is obtained.
As can be seen from fig. 4, in the middle period of the output voltage of the rectifier bridge, the current distortion is small, and the influence on the power factor is small, so that the rectifier bridge can be naturally rectified by adopting the passive PFC control strategy in the middle period. That is, the average current control strategy is adopted before and after the input voltage of the PFC circuit 112 crosses zero, and the passive PFC control strategy is adopted at the top of the input voltage, so as to reduce the switching frequency of the power device, reduce the loss of the power device, and increase the service life of the air conditioner 10 while ensuring a high power factor.
Therefore, zero-crossing detection needs to be performed on the input voltage of PFC circuit 112 (i.e., the output voltage of rectifier bridge 111), and taking fig. 6 as an example, time t1 and time t4 are zero-crossing points. In fig. 6, (a) represents the output voltage of the rectifier bridge 111, and is one output voltage period; (b) which represents the output current of the rectifier bridge 111, acquires the current compressor frequency of the air conditioner 10 when the zero-crossing of the output voltage of the rectifier bridge 111 is detected, that is, at time t 1.
And S102, obtaining a target turn-off duration corresponding to the current compressor frequency.
Because the outer machine controller 11 of the air conditioner 10 does not turn on the PFC when the compressor operates at a low frequency, the PFC is usually turned on when the frequency of the compressor reaches 45Hz or more; meanwhile, the load of the air conditioner 10 is periodically changed, which causes the output current of the rectifier bridge 111 to be changed. Therefore, for different compressor frequencies, the active duration of the passive PFC control strategy is different within one output voltage cycle of the rectifier bridge 111, and it is required to make the input current of the PFC circuit 112 have a better sine degree and minimize the switching frequency of the power device.
Therefore, for the compressor frequency of 45Hz and above, different compressor frequencies have different turn-off durations corresponding to the compressor frequency, and the turn-off durations are the durations between t2 and t3 in fig. 6. Accordingly, the target turn-off period is a turn-off period corresponding to the frequency of the compressor of the air conditioner 10 when the output voltage of the rectifier bridge 111 crosses zero (e.g., at time t 1).
In one embodiment, the external unit controller 11 may store a data table in advance, where the data table includes a plurality of compressor frequencies and a shutdown duration corresponding to each compressor frequency, and the data table is obtained by measuring the air conditioner 10 by an operator;
accordingly, the manner of obtaining the target turn-off duration corresponding to the current compressor frequency may include:
and determining the target turn-off duration corresponding to the current compressor frequency from the data table according to the current compressor frequency.
S103, calculating a first time length and a second time length according to the target turn-off time length and the output voltage period of the rectifier bridge, wherein the first time length, the target turn-off time length and the second time length are sequentially continuous and occupy one output voltage period, and the first time length and the second time length are equal.
For an output voltage period of the rectifier bridge 111, under the condition that the target turn-off duration is known, the first duration and the second duration in the period can be determined according to the output voltage period and the target turn-off duration. That is, in conjunction with fig. 6, one output voltage period is T, the target turn-off time period is T2-T3, the first time period is T1-T2, the second time period is T3-T4, T1-T2 and T3-T4 are equal in length.
In one embodiment, the calculating the first duration and the second duration according to the target turn-off duration and the output voltage period of the rectifier bridge may include:
according to the target turn-off duration and the output voltage period of the rectifier bridge, according to a preset formula:
T1＝(T-T0)/2
calculating a first time length and the second time length;
where T1 denotes a first period and a second period, T denotes an output voltage period, and T0 denotes a target off period.
And S104, controlling the on-off of a power device of the PFC circuit by adopting an average current control strategy in the first time period and the second time period.
And S105, naturally rectifying the rectifier bridge by adopting a passive PFC control strategy within the target turn-off duration, and controlling the power device of the PFC circuit to be turned off.
Taking fig. 6 as an example, for one output voltage period T of the rectifier bridge 111, the average current control strategy is adopted from T1 to T2; naturally rectifying the rectifier bridge 111 by adopting a passive PFC control strategy at t 2-t 3 to enable the power device to be in an off state all the time; and (3) adopting an average current control strategy at t 3-t 4, wherein the time lengths of t 1-t 2 and t 3-t 4 are equal.
Referring to fig. 7, a method for generating a data table, that is, a method for measuring a turn-off duration corresponding to each compressor frequency in the data table, may include the following steps:
and S1, when the frequency of the compressor is a first preset frequency, controlling the on-off of a power device of the PFC circuit by adopting an average current control strategy, and measuring the first driving efficiency of the PFC circuit.
Normally, the external machine controller 11 turns on the PFC only when the compressor frequency reaches 45Hz or more, and therefore, it is necessary to measure the turn-off time periods corresponding to the compressor frequencies of 45Hz or more. In the measurement process, the average current method is completely adopted to control the on-off of the power device in the PFC circuit 112 for the same compressor frequency, and then the driving efficiency of the PFC circuit 112 is measured after the air conditioner 10 is stably operated for a period of time (for example, 30 min).
The first driving efficiency refers to the driving efficiency of the PFC circuit 112 when the average current method is used to control the on/off of the power device in the PFC circuit 112.
Alternatively, the first predetermined frequency may be 45Hz to 50Hz, typically 45 Hz.
S2, setting the initial value of the off-period.
The initial value of the off-duration is an empirically chosen value, e.g., 1ms, etc., incorporated in fig. 6, i.e., setting t 2-t 3 to 1 ms.
And S3, calculating the first time length and the second time length according to the initial value of the turn-off time length and the output voltage period.
For one output voltage period (e.g., 10ms) of the rectifier bridge 111, when the turn-off time period (t 2-t 3, e.g., 1ms) is known, the first time period (t 1-t 2) and the second time period (t 3-t 4) can be calculated, and the calculation manner is synchronized to step S103, which is not described herein again.
And S4, controlling the on-off of the power device of the PFC circuit by adopting an average current control strategy in the first time period and the second time period.
And S5, naturally rectifying the rectifier bridge by adopting a passive PFC control strategy within the turn-off duration, and controlling the turn-off of a power device of the PFC circuit.
And S6, measuring the harmonic content of the outer machine controller and the second driving efficiency of the PFC circuit.
Under the same condition of step S1, that is, when the compressor frequency is the first preset frequency, the PFC control method provided in this embodiment is adopted, the average current control strategy is adopted at t1 to t2, the passive PFC control strategy is adopted at t2 to t3, and the average current control strategy is adopted at t3 to t 4; meanwhile, after the air conditioner 10 is stably operated for a certain period of time (e.g., 30min), the harmonic content of the external unit controller and the driving efficiency of the PFC circuit 112 are measured.
The second driving efficiency refers to the driving efficiency of the PFC circuit 112 when the PFC control method provided by this embodiment is used to control the on/off of the power device in the PFC circuit 112.
And S7, adjusting the initial value of the turn-off duration until the harmonic content meets the preset standard, the second driving efficiency is the highest and is lower than the first driving efficiency, and taking the current value of the turn-off duration as the turn-off duration corresponding to the current compressor frequency.
In general, the driving efficiency of the PFC circuit 112 in the manner of step S1 is necessarily higher than that in the manner of steps S4 to S5, that is, the first driving efficiency is necessarily higher than the second driving efficiency. Therefore, when the highest second driving efficiency is found, it is necessary to determine whether the highest second driving efficiency is lower than the first driving efficiency, and if the highest second driving efficiency is higher than the first driving efficiency, it indicates that the measurement process is problematic and needs to be measured again.
With reference to fig. 6, the time duration from t2 to t3 is repeatedly adjusted, so that the harmonic content of the external machine controller 11 meets the industry standard, the driving efficiency of the PFC circuit 112 is the highest and is higher than the driving efficiency of the PFC circuit 112 when the average current method is used to control the on/off of the power device in the PFC circuit 112, and the time duration from t2 to t3 at this time is the corresponding off time duration when the compressor frequency is the first preset frequency.
And S8, judging whether the frequency of the compressor reaches a second preset frequency.
Alternatively, the second predetermined frequency may be 120Hz to 125Hz, typically 120 Hz.
If the compressor frequency does not reach the second preset frequency, executing the step S9, and after the step S9 is executed, repeatedly executing the steps S1 to S7 until the compressor frequency reaches the second preset frequency, and obtaining a turn-off duration corresponding to each compressor frequency.
And S9, increasing the frequency of the compressor according to the preset frequency interval.
For example, the compressor frequency is measured between 45Hz and 120Hz, and the corresponding off-time of each compressor frequency is measured for each 10Hz increase. Therefore, if the frequency of the compressor does not reach 120Hz, 1010Hz is increased, and then steps S1-S8 are executed to repeatedly test until the turn-off duration corresponding to each compressor frequency between 45 Hz-120 Hz is obtained.
Alternatively, the predetermined frequency interval may be 10Hz to 15Hz, typically 10 Hz.
Compared with the prior art, the embodiment has the following beneficial effects:
firstly, in the embodiment, on the basis of the existing Boost type average current method, a control strategy of PFC drive is improved, in an output voltage period of a rectifier bridge, an average current control strategy is adopted in a first time length and a second time length, and a passive PFC control strategy is adopted in a target turn-off time length to naturally rectify the rectifier bridge, so that a power device is always in a turn-off state, and therefore, while a higher power factor is ensured, the switching frequency of the power device is reduced, the loss of the power device is reduced, and the service life of an air conditioner is prolonged;
secondly, the external machine controller 11 starts the PFC when the compressor frequency reaches 45Hz or more, so that the measurement is performed in advance to obtain the turn-off duration corresponding to each compressor frequency of 45Hz or more, so that the input current of the PFC circuit 112 has better sine degree and the switching frequency of the power device is minimum, and the loss of the power device is further reduced;
thirdly, the hardware topology structure of the power supply device in the external unit controller 11 is not changed, but the control strategy of the PFC drive is improved, and the hardware cost is not increased.
In order to execute the corresponding steps in the above embodiments and various possible embodiments, an implementation manner of the PFC control device is given below. Fig. 8 is a schematic diagram of functional modules of the PFC control apparatus 100 according to the present invention. It should be noted that the fundamental principle and the generated technical effect of the PFC control apparatus 100 described in this embodiment are the same as those of the foregoing method embodiment, and for a brief description, reference may be made to corresponding contents of the foregoing method embodiment for a part not mentioned in this embodiment. The PFC control device 100 is applied to an external machine controller 11, and the PFC control device 100 is described below with reference to fig. 8, where the PFC control device 100 includes: the system comprises an acquisition module 110, an acquisition module 120, a calculation module 130, a first execution module 140, and a second execution module 150.
The obtaining module 110 is configured to obtain a current compressor frequency of the air conditioner when a zero crossing point of an output voltage of the rectifier bridge is detected.
An obtaining module 120 is configured to obtain a target turn-off duration corresponding to a current compressor frequency.
The calculating module 130 is configured to calculate a first duration and a second duration according to the target turn-off duration and the output voltage period of the rectifier bridge, where the first duration, the target turn-off duration, and the second duration are consecutive and occupy one output voltage period, and the first duration and the second duration are equal to each other.
And the first execution module 140 is configured to control on/off of a power device of the PFC circuit by using an average current control strategy in the first time period and the second time period.
And the second execution module 150 is configured to naturally rectify the rectifier bridge by using a passive PFC control strategy within the target turn-off duration, and control the power device of the PFC circuit to turn off.
Optionally, the external machine controller 11 stores a data table in advance, where the data table includes a plurality of compressor frequencies and a turn-off duration corresponding to each compressor frequency;
the obtaining module 120 is specifically configured to: and determining the target turn-off duration corresponding to the current compressor frequency from the data table according to the current compressor frequency.
Optionally, the calculation module 130 is specifically configured to: according to the target turn-off duration and the output voltage period of the rectifier bridge, according to a preset formula:
T1＝(T-T0)/2
calculating a first time length and the second time length; where T1 denotes a first period and a second period, T denotes an output voltage period, and T0 denotes a target off period.
In summary, according to the PFC control method, apparatus, air conditioner and storage medium provided by the present invention, based on the existing Boost type average current method, a control strategy of PFC driving is improved, and since the current distortion is small in the middle time period of the output voltage of the rectifier bridge, the power device is always turned off in the middle time period, thereby ensuring a high power factor, reducing the switching frequency of the power device, reducing the loss of the power device, and increasing the service life of the air conditioner.
Although the present invention is disclosed above, the present invention is not limited thereto. Various changes and modifications may be effected therein by one skilled in the art without departing from the spirit and scope of the invention as defined in the appended claims.

Claims (10)

1. A PFC control method characterized by being applied to an outdoor unit controller (11) of an air conditioner (10), the outdoor unit controller (11) including a power supply device including a rectifier bridge (111) and a power factor correction PFC circuit (112);
the PFC control method comprises the following steps:
when the zero crossing point of the output voltage of the rectifier bridge (111) is detected, acquiring the current compressor frequency of the air conditioner (10);
obtaining a target turn-off duration corresponding to the current compressor frequency;
calculating a first time length and a second time length according to the target turn-off time length and the output voltage period of the rectifier bridge (111), wherein the first time length, the target turn-off time length and the second time length are sequentially continuous and occupy one output voltage period, and the first time length and the second time length are equal;
controlling the on-off of a power device of the PFC circuit (112) by adopting an average current control strategy in the first time period and the second time period;
and naturally rectifying the rectifier bridge (111) by adopting a passive PFC control strategy within the target turn-off duration, and controlling the power device of the PFC circuit (112) to be turned off.
2. The PFC control method according to claim 1, wherein the external unit controller (11) is pre-stored with a data table, wherein the data table comprises a plurality of compressor frequencies and a turn-off duration corresponding to each compressor frequency;
the step of obtaining the target turn-off duration corresponding to the current compressor frequency includes:
and determining the target turn-off duration corresponding to the current compressor frequency from the data table according to the current compressor frequency.
3. The PFC control method of claim 2, wherein the data table is generated as follows:
when the compressor frequency is a first preset frequency, controlling the on-off of a power device of the PFC circuit (112) by adopting the average current control strategy, and measuring the first driving efficiency of the PFC circuit (112); setting an initial value of the turn-off duration;
calculating the first time length and the second time length according to the initial value of the turn-off time length and the output voltage period;
controlling the on-off of a power device of the PFC circuit (112) by adopting the average current control strategy in the first time period and the second time period;
naturally rectifying the rectifier bridge (111) by adopting the passive PFC control strategy within the turn-off duration to control the turn-off of a power device of the PFC circuit (112);
measuring the harmonic content of the outer machine controller (11) and the second driving efficiency of the PFC circuit (112);
adjusting the initial value of the turn-off duration until the harmonic content meets a preset standard, the second driving efficiency is highest and is lower than the first driving efficiency, and taking the current value of the turn-off duration as the turn-off duration corresponding to the current compressor frequency;
judging whether the frequency of the compressor reaches a second preset frequency or not;
if not, increasing the compressor frequency according to a preset frequency interval, and repeatedly executing the steps until the compressor frequency reaches the second preset frequency, so as to obtain the turn-off duration corresponding to each compressor frequency.
4. The PFC control method according to claim 3, wherein the first preset frequency is 45 Hz-50 Hz, the second preset frequency is 120 Hz-125 Hz, and the preset frequency interval is 10 Hz-15 Hz.
5. The PFC control method according to claim 1, wherein the step of calculating a first duration and a second duration depending on the target turn-off duration and the period of the output voltage of the rectifier bridge (111) comprises:
according to the target turn-off duration and the output voltage period of the rectifier bridge (111), according to a preset formula:
T1＝(T-T0)/2
calculating the first time length and the second time length;
wherein T1 represents the first and second time periods, T represents the output voltage period, and T0 represents the target OFF time period.
6. A PFC control device, characterized by being applied to an external unit controller (11) of an air conditioner (10), the external unit controller (11) including a power supply device including a rectifier bridge (111) and a power factor correction PFC circuit (112);
the PFC control device (100) includes:
an obtaining module (110) for obtaining a current compressor frequency of the air conditioner (10) when a zero crossing of an output voltage of the rectifier bridge (111) is detected;
an obtaining module (120) for obtaining a target turn-off duration corresponding to the current compressor frequency;
a calculating module (130) configured to calculate a first time duration and a second time duration according to the target turn-off time duration and an output voltage period of the rectifier bridge (111), where the first time duration, the target turn-off time duration and the second time duration are consecutive and occupy one output voltage period, and the first time duration and the second time duration are equal to each other;
a first execution module (140) for controlling the on/off of the power device of the PFC circuit (112) in the first time period and the second time period by adopting an average current control strategy;
and the second execution module (150) is used for naturally rectifying the rectifier bridge (111) by adopting a passive PFC control strategy within the target turn-off duration and controlling the power device of the PFC circuit (112) to be turned off.
7. The PFC control device according to claim 6, wherein the external unit controller (11) is pre-stored with a data table, wherein the data table comprises a plurality of compressor frequencies and a turn-off duration corresponding to each compressor frequency;
the obtaining module is specifically configured to:
and determining the target turn-off duration corresponding to the current compressor frequency from the data table according to the current compressor frequency.
8. The PFC control device according to claim 6, wherein the calculation module (130) is specifically configured to:
according to the target turn-off duration and the output voltage period of the rectifier bridge (111), according to a preset formula:
T1＝(T-T0)/2
calculating the first time length and the second time length;
wherein T1 represents the first and second time periods, T represents the output voltage period, and T0 represents the target OFF time period.
9. An air conditioner, characterized in that the air conditioner (10) comprises:
an outdoor unit controller (11);
a memory (12) for storing one or more programs that, when executed by the outer unit controller (11), cause the outer unit controller (11) to implement the PFC control method according to any one of claims 1-5.
10. A computer-readable storage medium, on which a computer program is stored, characterized in that the computer program, when executed by an external unit controller (11), implements the PFC control method according to any one of claims 1 to 5.
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