Fan control system and air conditioner

Abstract

The invention discloses a draught fan control system and an air conditioner. The draught fan control system comprises a draught fan, a controller and a controller, the processing unit is configured as follows: S1, a rotating speed instruction of the fan is obtained; s2, when the rotating speed corresponding to the rotating speed instruction reaches the upper limit value of a first rotating speed threshold value, the d-axis current id * is given to be 0; s3, when the rotating speed reaches the lower limit value of the first rotating speed threshold value and reaches the upper limit value of the second rotating speed threshold value, d-axis current id * is given as d-axis compensation current; the d-axis compensation current is the d-axis current corresponding to the relationship between the fitted rotating speed and the d-axis current at different rotating speeds; and S4, when the rotating speed reaches the lower limit value of the second rotating speed threshold value and reaches the upper limit value of the third rotating speed threshold value, inertia speed reduction control is executed. Through self-adaptive compensation of the d-axis current, the signal-to-noise ratio of the sampling current is improved, the precision of a current signal in a low-speed domain of the observer is ensured, and wide-wind-domain stable operation of the fan is ensured according to partition control of different rotating speeds.

Description

Technical Field

[0001] The present invention relates to the technical field of fan control, and in particular to a fan control system and an air conditioner. Background Art

[0002] The permanent magnet synchronous fan motor for air conditioners is an important component of air conditioners and is used in both indoor and outdoor units. The fan motor adopts a permanent magnet synchronous motor (PMSM).

[0003] Due to limitations of cost, volume, installation and other factors, PMSM control systems gradually eliminate position sensors and use a single current sensor or a single resistor to sample the inverter DC bus current. The motor phase current is then reconstructed through an algorithm to achieve PMSM control, i.e. PMSM position sensorless control based on single resistor (current sensor) sampling.

[0004] The mainstream control algorithm for PMSM is Field-Oriented Control (FOC), also known as vector control.

[0005] When the fan is running at low speed, the current sampling signal-to-noise ratio is small, resulting in inaccurate estimation of the fan position by the position observer in FOC control.

[0006] In extreme working conditions such as low-temperature cooling and high-temperature heating, the fan speed needs to be operated within the range of 1000 rpm to 44 rpm. Therefore, wide-range fan speed operation is a rigid requirement for the operation of multi-split air conditioners. Currently, the minimum speed of Midea's fans can only reach 70 rpm, and they are operated intermittently, resulting in large fluctuations in air volume.

[0007] Therefore, how to solve the low speed of the air-conditioning fan, meet the air volume demand in the low-speed range of the system, and realize the wide wind range operation of the fan is the problem that this application needs to solve.

[0008] The above information disclosed in the background technology is only used to increase the understanding of the background technology of the present application, and therefore, it may include information that does not constitute the prior art known to ordinary technicians in the field. Summary of the invention

[0009] In response to the problems pointed out in the background technology, the present application provides a fan control system, which improves the signal-to-noise ratio of the sampled current by adaptively compensating the d-axis current, ensures the accuracy of the current signal in the low-speed domain of the observer, and controls the partitions according to different speeds to ensure stable operation of the fan in a wide wind range.

[0010] In order to achieve the above-mentioned purpose, the present invention adopts the following technical solutions: The present application relates to a fan control system, comprising: The fan uses the given q-axis current iq* and d-axis current id* as current loop inputs to perform FOC control on the IPM module when it starts; A processing unit configured to: S1: Get the speed command of the fan; S2: when the speed corresponding to the speed command reaches the upper limit of the first speed threshold, the d-axis current id* is 0; S3: When the speed corresponding to the speed command reaches the lower limit of the first speed threshold and the upper limit of the second speed threshold, the d-axis current id* is the d-axis compensation current; The d-axis compensation current is the d-axis current corresponding to the relationship between the fitted speed and the d-axis current at different speeds, and the d-axis current used for fitting the curve is calculated based on the q-axis current obtained when the fan is stably running at different speeds and the total motor current is when the fan is stably running at the upper limit value of the first speed threshold; S4: When the speed corresponding to the speed command reaches the lower limit of the second speed threshold and the upper limit of the third speed threshold, inertia speed reduction control is performed, and the inertia speed reduction control is specifically as follows: Using a pre-established equal air volume model based on the upper limit value of the second speed threshold, the operation time and the stop time of the fan at the upper limit value of the second speed threshold within the first preset time period are obtained, the operation of the fan is intermittently controlled, and when the fan is running, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the second speed threshold; Among them, the equal wind volume model based on the upper limit value of the second speed threshold is a data model of wind volume and speed within a first preset time period, and the wind volume generated by the fan at the upper limit value of the second speed threshold within the first preset time period is equal to the wind volume generated by the speed within the first preset time period.

[0011] The fan control system involved in the present application compensates for different d-axis currents through different speed instructions. When the speed corresponding to the speed instruction reaches the upper limit value of the first speed threshold, it means that the fan set speed is relatively high. At this time, the d-axis current id* is 0. Traditional FOC control is adopted. Due to the high speed, the current sampling accuracy is also high.

[0012] When the speed corresponding to the speed command reaches the lower limit of the first speed threshold and the upper limit of the second speed threshold, it means that when the fan is set to run at a low speed, the current sampling accuracy is prone to low. At this time, by compensating the d-axis current, high current sampling accuracy at low speed can be achieved, which is equivalent to achieving the purpose of reducing the minimum stable speed of the fan and improving the stable operation of the fan in the low speed range.

[0013] When the speed corresponding to the speed command reaches the lower limit of the second speed threshold and the upper limit of the third speed threshold, it means that the speed is low. At this time, inertia speed reduction control is adopted. Through the equal wind volume model, the operation of the fan at low speed is equivalently converted into operation at a stable wind speed, so as to achieve stable operation of the fan in a lower speed range.

[0014] In this way, the fan control system involved in this application, combined with d-axis compensation current adaptive control and inertia speed reduction control, can achieve stable operation of the fan in a wide speed range, and improve the current sampling accuracy, ensuring that the observer accurately outputs the fan position information, thereby achieving reliable control of the fan; the fan using this fan control system has higher performance than existing competing fans.

[0015] In some embodiments of the present application, the relationship between the rotation speed and the d-axis current at different rotation speeds is fitted, specifically: controlling a d-axis current and a q-axis current of the fan when the fan is stably operated at an upper limit value of the first speed threshold; Using the d-axis current and the q-axis current, the total motor current is is calculated as a reference current threshold; Controlling the fan to operate stably at different speeds, and obtaining the q-axis current iq at different speeds; According to the d-axis current id=sqrt(is 2 -iq 2 ), calculate the d-axis current id; According to different rotation speeds and d-axis current id, the curves between different rotation speeds and d-axis currents are fitted, and the relationship between different rotation speeds and d-axis currents is established.

[0016] The present application selects a stable speed for stable operation of the fan, and based on the total motor current at the stable speed, determines the d-axis current that needs to be compensated at different speeds lower than the stable speed, thereby making the current at different speeds lower than the stable speed equivalent to the current at the stable speed, thereby improving the sampling signal-to-noise ratio and the current sampling accuracy.

[0017] In some embodiments of the present application, in order to avoid uncontrollable startup of the fan after shutdown during inertia speed reduction control, when executing the inertia speed reduction control, the speed of the fan is monitored and the speed is controlled for speed tolerance to control the fan to stop to meet the shutdown time, thereby achieving reliable restart of the fan after shutdown.

[0018] In some embodiments of the present application, when the monitored rotation speed reaches a minimum rotation speed, it indicates that the fan is shut down.

[0019] In order to facilitate the monitoring of the shutdown state of the fan speed, the present application designs a minimum speed, for example 30rmp. When controlling the fan to stop, if the monitored speed reaches the minimum speed, the fan is considered to be stopped.

[0020] In some embodiments of the present application, in order to achieve reliable startup of the fan after shutdown, the speed fault tolerance control is specifically: S11: when the time required for the fan to stop from running is less than the stop time, the fan is started at a higher speed when the required time is equal to the stop time; S12: When the time required for the fan to stop from running is equal to the stop time, the fan is started at a high speed; When the time required for the fan to stop from running is greater than the stop time, the pre-established equal air volume model based on the upper limit value of the fourth speed threshold is called to obtain the operation time and stop time of the fan within the second preset time period at the upper limit value of the fourth speed threshold, and return to S11; Wherein, during the calling of the equal air volume model based on the upper limit value of the fourth speed threshold, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the fourth speed threshold when the fan is running; The equal wind volume model based on the upper limit value of the fourth speed threshold is a data model of wind volume and speed within the second preset time period. The wind volume generated by the fan at the upper limit value of the fourth speed threshold within the second preset time period is equal to the wind volume generated by the speed within the second preset time period.

[0021] The present application also relates to an air conditioner, comprising IPM module; When the outdoor fan is started, the given q-axis current iq* and d-axis current id* are used as the current loop input to perform FOC control on the IPM module; A processing unit configured to: S1: Get the speed command of the outdoor fan; S2: when the speed corresponding to the speed command reaches the upper limit of the first speed threshold, the d-axis current id* is 0; S3: When the speed corresponding to the speed command reaches the lower limit of the first speed threshold and the upper limit of the second speed threshold, the d-axis current id* is the d-axis compensation current; The d-axis compensation current is the d-axis current corresponding to the relationship between the fitted speed and the d-axis current at different speeds, and the d-axis current used for fitting the curve is calculated based on the q-axis current obtained when the outdoor fan is stably running at different speeds and the total motor current is when the outdoor fan is stably running at the upper limit value of the first speed threshold; S4: When the speed corresponding to the speed command reaches the lower limit of the second speed threshold and the upper limit of the third speed threshold, inertia speed reduction control is performed, and the inertia speed reduction control is specifically as follows: Using a pre-established wind volume model based on the upper limit value of the second speed threshold, the operation time and stop time of the outdoor fan at the upper limit value of the second speed threshold within the first preset time period are obtained, the operation of the outdoor fan is intermittently controlled, and when the fan is running, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the second speed threshold; Among them, the equal wind volume model based on the upper limit value of the second speed threshold is a data model of wind volume and speed within a first preset time period, and the wind volume generated by the outdoor fan at the upper limit value of the second speed threshold within the first preset time period is equal to the wind volume generated by the speed within the first preset time period.

[0022] The outdoor fan of the air conditioner in the present application works under extreme working conditions. Combined with d-axis compensation current adaptive control and inertia speed reduction control, the fan can be operated stably in a wide speed range and used at low speeds under extreme working conditions. The current sampling accuracy is improved by compensating the d-axis current to ensure that the observer accurately outputs the motor position information, thereby achieving reliable control of the outdoor fan.

[0023] In some embodiments of the present application, the relationship between the rotation speed and the d-axis current at different rotation speeds is fitted, specifically: controlling the d-axis current and the q-axis current of the outdoor fan when the outdoor fan is stably operated at the upper limit value of the first speed threshold; Using the d-axis current and the q-axis current, the total motor current is is calculated as a reference current threshold; Controlling the outdoor fan to operate stably at different speeds, and obtaining the q-axis current iq at different speeds; According to the d-axis current id=sqrt(is 2 -iq 2 ), calculate the d-axis current id; According to different rotation speeds and d-axis current id, the curves between different rotation speeds and d-axis currents are fitted, and the relationship between different rotation speeds and d-axis currents is established.

[0024] In some embodiments of the present application, when the inertia speed reduction control is executed, the rotational speed of the outdoor fan is monitored and the rotational speed is controlled for speed tolerance to control the outdoor fan to stop to meet the stop time.

[0025] In some embodiments of the present application, when the monitored rotation speed reaches a minimum rotation speed, it indicates that the outdoor fan is shut down.

[0026] In some embodiments of the present application, the speed fault tolerance control is specifically: S11: when the time required for the fan to stop from running is less than the stop time, the fan is started at a higher speed when the required time is equal to the stop time; S12: When the time required for the fan to stop from running is equal to the stop time, the fan is started at a high speed; S13: When the time required for the fan to stop from running is greater than the stop time, a pre-established equal air volume model based on the upper limit value of the fourth speed threshold is called to obtain the operation time and stop time of the fan within the second preset time period at the upper limit value of the fourth speed threshold, and return to S11; Wherein, during the calling of the equal air volume model based on the upper limit value of the fourth speed threshold, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the fourth speed threshold when the fan is running; The equal wind volume model based on the upper limit value of the fourth speed threshold is a data model of wind volume and speed within the second preset time period. The wind volume generated by the outdoor fan at the upper limit value of the fourth speed threshold within the second preset time period is equal to the wind volume generated by the speed within the second preset time period.

[0027] After reading the specific embodiments of the present invention in conjunction with the accompanying drawings, other features and advantages of the present invention will become more clear. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.

[0029] Figure 1 It is the principle block diagram of the existing air conditioner; Figure 2 This is the circuit diagram of the IPM module involved in the outdoor fan of the air conditioner; Figure 3 A circuit diagram of an IPM module of a PMSM in the prior art; Figure 4 It is a principle block diagram of FOC control of PMSM in the prior art; Figure 5 A hardware motor driver sampling circuit involved in an IPM module of a PMSM in the prior art; Figure 6 It is a flow chart of d-axis current compensation in the fan control system proposed in this application; Figure 7 A flow chart showing the relationship between the rotation speed and the d-axis current at different rotation speeds in the fan control system proposed in the present application; Figure 8 A flow chart of speed fault tolerance control in a fan control system proposed in this application; Fig. 9 The principle of partition control based on the speed command of the fan control system proposed in this application Figure 1 ; Fig.10 The principle of partition control based on the speed command of the fan control system proposed in this application Figure 2 .

[0030] Reference numerals: 10. PMSM; 20. IPM module. DETAILED DESCRIPTION

[0031] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0032] In the description of the present application, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present application.

[0033] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of this application, unless otherwise specified, "plurality" means two or more.

[0034] In the description of this application, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0035] In the present invention, unless otherwise clearly specified and limited, a first feature being "above" or "below" a second feature may include that the first and second features are in direct contact, or may include that the first and second features are not in direct contact but are in contact through another feature between them. Moreover, a first feature being "above", "above" and "above" a second feature includes that the first feature is directly above and obliquely above the second feature, or simply indicates that the first feature is higher in level than the second feature. A first feature being "below", "below" and "below" a second feature includes that the first feature is directly below and obliquely below the second feature, or simply indicates that the first feature is lower in level than the second feature.

[0036] The disclosure below provides many different embodiments or examples to realize different structures of the present invention. In order to simplify the disclosure of the present invention, the parts and settings of specific examples are described below. Of course, they are only examples, and the purpose is not to limit the present invention. In addition, the present invention can repeat reference numbers and / or reference letters in different examples, and this repetition is for the purpose of simplicity and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed. In addition, the present invention provides various specific examples of processes and materials, but those of ordinary skill in the art can be aware of the application of other processes and / or the use of other materials.

[0037] [Basic working principle of air conditioner] The air conditioner performs the air conditioner's refrigeration cycle by using a compressor, condenser, expansion valve, and evaporator. The refrigeration cycle includes a series of processes involving compression, condensation, expansion, and evaporation to cool or heat the indoor space.

[0038] The low-temperature and low-pressure refrigerant enters the compressor, which compresses it into high-temperature and high-pressure refrigerant gas and discharges the compressed refrigerant gas. 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.

[0039] The expansion valve expands the high-temperature and high-pressure liquid refrigerant condensed in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the refrigerant expanded in the expansion valve and returns the low-temperature and low-pressure refrigerant gas to the compressor. The evaporator can achieve a cooling effect by utilizing the latent heat of evaporation of the refrigerant to exchange heat with the material to be cooled. In the entire cycle, the air conditioner can adjust the temperature of the indoor space.

[0040] See also Figure 1 , the outdoor unit of the air conditioner refers to a part of a refrigeration cycle including a compressor and an outdoor heat exchanger, the indoor unit of the air conditioner includes an indoor heat exchanger, and the expansion valve may be provided in the indoor unit or the outdoor unit.

[0041] The indoor heat exchanger and the outdoor heat exchanger function as a condenser or an evaporator. When the indoor heat exchanger functions as a condenser, the air conditioner functions as a heater in a heating mode, and when the indoor heat exchanger functions as an evaporator, the air conditioner functions as a cooler in a cooling mode.

[0042] The outdoor fan or indoor fan is generally realized by a permanent magnet synchronous motor (PMSM) driving the impeller.

[0043] The fans mentioned in this application generally refer to outdoor fans (see Figure 2 ), because the outdoor unit is installed outdoors, and the outdoor fan is easily affected by extreme working conditions (such as low-temperature cooling and high-temperature heating) and needs to operate within a wide speed range.

[0044] [IPM module] See also Figure 3 , which shows a circuit diagram of an IPM (Intelligent Power Module) module 20 of the PMSM 10 .

[0045] The IPM module 20 includes a three-phase power inverter for inverting the direct current Vdc on the bus to drive the PMSM 10 .

[0046] The three-phase power inverter is composed of six power switching elements, namely, the power switching element T1 of the U-phase upper bridge arm, the power switching element T3 of the V-phase upper bridge arm, the power switching element T5 of the W-phase upper bridge arm, the power switching element T2 of the U-phase lower bridge arm, the power switching element T4 of the V-phase lower bridge arm, and the power switching element T6 of the W-phase lower bridge arm.

[0047] The structure and working principle of the three-phase power inverter are well known and will not be described in detail here.

[0048] The three-phase voltages UA, UB, and UC output by the three-phase power inverter act on the PMSM 10.

[0049] [FOC control] The mainstream control algorithm for PMSM10 is Field-Oriented Control (FOC), also known as vector control.

[0050] The FOC control is to perform inverter control on the IPM module 20 , and the IPM module 20 inverts the direct current Vdc on the bus into alternating current to supply to the PMSM 10 .

[0051] See also Figure 4 , which shows a principle block diagram of FOC control of PMSM 10.

[0052] The FOC control adopts speed and current dual closed-loop control, with the speed loop as the outer loop and the current loop as the inner loop.

[0053] First, the working principle of the current loop is explained.

[0054] iq* is the given value of the q-axis current, id* is the given value of the d-axis current, iA and iB are the sampled currents of phase A and phase B respectively, and the C-phase current iC can be calculated using the formula iA+iB+iC=0.

[0055] The three-phase currents are transformed by Clark to obtain iα and iβ; then iα and iβ are transformed by Park to obtain iq and id.

[0056] Then, iq and id calculate the error values ​​with their given values ​​iq* and id* respectively.

[0057] Substitute the q-axis current error value into the PI control module of the current regulation of the q-axis current to obtain uq, and substitute the d-axis current error value into the PI control module of the current regulation of the d-axis current to obtain ud.

[0058] Performing an inverse Park transform (i.e., inverse Park transform) on uq and ud to obtain uα and uβ, and then performing SVPWM (Space Vector Pulse Width Modulation) operation to obtain six PWM signals. The PWM signals control the IPM module 20, and the IPM module 20 drives the PMSM 10 to rotate.

[0059] Secondly, the working principle of the speed loop is explained.

[0060] Still refer to Figure 4, an observer is used to observe the motor position and output the speed n, the speed n is subtracted from the given speed n*, and then the speed is adjusted (for example, using a PI controller) to obtain the given q-axis current iq*.

[0061] The FOC control as described above is a commonly used control method in the prior art.

[0062] When the fan is in normal operation, Figure 4 The FOC control shown performs conventional FOC control, generally setting the given d-axis current id* to 0, and the motor current mainly depends on the given q-axis current iq* output by the speed loop.

[0063] In some embodiments of the present application, when the motor is running at a low speed, the d-axis current is increased by compensation and the PWM modulation output pulse width is increased, so that the observer can filter out harmonic signals and improve the signal-to-noise ratio of the sampled current, which is beneficial to obtaining the real current signal and ensuring the sampling accuracy of the current signal in the low-speed domain of the observer, thereby improving the accuracy of the observer in estimating the motor position.

[0064] Moreover, at this time, only the radial excitation current of the motor is increased, the torque current is constant, the operating torque of the motor is constant, and the low-speed operation state of the fan is not affected.

[0065] The D-axis current compensation strategy is adopted to improve the accuracy of the sampling current at low speed, which is equivalent to reducing the minimum stable speed of the fan from, for example, 105 rpm to 70 rpm, thereby achieving stable operation at low speed.

[0066] See also Figure 5 , which shows a motor driver sampling circuit.

[0067] Among them, resistor R1, resistor R2, comparator V1 and comparator V2 form a sampling circuit, and then the analog signal output by the sampling circuit is converted into a digital signal through an A / D conversion unit, and the MCU reads the data signal and sends it to the observer.

[0068] The gain coefficient K of the sampling circuit, the sampling resistor R and the MCU equivalent AD reference voltage Vref are equivalently obtained.

[0069] See also Figure 4 It can be seen from the observer shown in that the observer sets the trigger sampling time, processes the sampling circuit current sampling, and estimates the fan rotor position through the control algorithm. As mentioned above, the hardware sampling accuracy of the current is crucial, especially when the fan is running in the low-speed domain, the fan current is small, the signal-to-noise ratio is low, and the hardware sampling accuracy is low, which may cause the motor to lose step.

[0070] After adopting the d-axis current compensation strategy, the d-axis compensation current is injected into the d-axis at low speed to increase the current detection threshold, improve the sampling signal-to-noise ratio, and improve the sampling accuracy of the effective signal.

[0071] For example, set the hardware sampling current deviation as Ierr, the uncompensated current at low speed as I1, the compensated current at low speed as Icomp, and the current I2 after compensation at low speed as I2 = I1 + Icomp.

[0072] The equivalent output voltage signal of the sampling circuit before compensating the current is Vout1, and the equivalent output voltage signal of the sampling circuit after compensating the current is Vout2.

[0073] Derive the equivalent output voltage signals Vout1 and Vout2 based on the sampling circuit design.

[0074] That is, Vout1 = (Ierr + I1) * R * K / Vref.

[0075] Vout2 = (Ierr + I2) * R * K / Vref = (Ierr + I1 + Icomp) * R * K / Vref.

[0076] Then Ierr introduces an output deviation voltage signal Vout_err: Vout_err = Ier * R * K / Vref.

[0077] Compare and analyze the proportion of Vout_errr in the equivalent output voltage signals Vout1 and Vout2 of the sampling circuit, so as to evaluate the hardware sampling current accuracy.

[0078] Since Vout1 < Vout2, therefore, Vout_err / Vout1 > Vout_err / Vout2.

[0079] Based on the above comparison, it can be seen that after compensating the current, the proportion of the output deviation voltage signal introduced by Ierr in the equivalent output voltage signal decreases, and the proportion of the effective signal increases, thereby improving the sampling accuracy of the effective signal.

[0080] In some embodiments of the present application, different d-axis compensation currents are compensated according to different speed commands to ensure stable operation of the fan at low speed.

[0081] As follows, the control of the fan will be divided into zones according to the speed corresponding to different speed commands.

[0082] See Figure 6 , describe the d-axis current that needs to be compensated correspondingly under different speed commands, and see Fig. 9 and Fig.10 , which shows different control methods corresponding to different speed commands.

[0083] As described above, the outdoor fan is controlled by FOC, wherein the given q-axis current iq* is obtained by speed regulation (eg, by using a PI controller), and the given d-axis current id* is set according to the speed corresponding to different speed instructions.

[0084] The air conditioning system includes a processing unit configured to perform the following process.

[0085] S1: Get the fan speed command.

[0086] In some embodiments of the present application, the fan is described by taking an outdoor fan in an air conditioner as an example.

[0087] The speed command is set, corresponding to Figure 4 The given speed n* is shown in .

[0088] S2: When the speed n* is greater than 105 rpm, set the d-axis current id* to 0.

[0089] In some embodiments of the present application, when the rotation speed n* reaches an upper limit value of the first rotation speed threshold, the given d-axis current id* is set to 0.

[0090] The outdoor fan uses a given q-axis current iq* and a given d-axis current id* for FOC control. This type of FOC control is no different from conventional FOC control. At this time, it can be considered as high-speed FOC closed-loop control.

[0091] In some embodiments of the present application, the first speed threshold may be a speed range or a specific speed setting value.

[0092] For example, the magnitude of the rotation speed and the first rotation speed is determined. If the rotation speed is greater than the first rotation speed, the given d-axis current id* is set to 0. Otherwise, the process proceeds to S3.

[0093] The above is only an example, and when the rotation speed reaches the upper limit value of the first rotation speed threshold, that is, when the rotation speed is greater than or equal to the first rotation speed, the given d-axis current id* may also be set to 0.

[0094] The first rotation speed may be set to 105 rpm.

[0095] Therefore, when n* is greater than 105 rpm, the d-axis current id* is set to 0, and when n* is equal to 105 rpm, the d-axis current id* is set to 0.

[0096] As mentioned above, the different rotation speeds n* involved in S2 are all within the rotation speed range of greater than 105 rpm.

[0097] S2 shows that when the speed n* is high, the current sampling accuracy is high, and the d-axis current is not compensated at this time.

[0098] S3: When the speed n* is less than or equal to 105 rpm and greater than or equal to 70 rpm, the given d-axis current id* is set as the d-axis compensation current.

[0099] When the rotation speed n* reaches the lower limit value of the first rotation speed threshold value and reaches the upper limit value of the second rotation speed threshold value, the given d-axis current id* is set as the d-axis compensation current.

[0100] The outdoor fan uses the given q-axis current iq* and d-axis compensation current for FOC control. At this time, the given d-axis current is not zero, but FOC control is still used.

[0101] In some embodiments of the present application, the second speed threshold may be a speed range or a specific speed setting value.

[0102] For example, the rotation speed and the magnitude of the first rotation speed and the second rotation speed are determined. If the rotation speed is less than the first rotation speed and greater than the second rotation speed, the given d-axis current id* is set as the d-axis compensation current. Otherwise, proceed to S4.

[0103] The above is just an example. When the speed reaches the lower limit value of the first speed threshold and the upper limit value of the second speed threshold, that is, the speed is greater than or equal to the second speed and less than the first speed, or the speed is greater than the second speed and less than or equal to the first speed, or the speed is greater than or equal to the second speed and less than or equal to the first speed, the given d-axis current id* can also be set as the d-axis compensation current.

[0104] The second rotation speed may be set to 70 rpm.

[0105] In some embodiments of the present application, when the rotation speed is greater than 70 rpm and less than 105 rpm, the given d-axis current id* is set as the d-axis compensation current.

[0106] In some embodiments of the present application, when the rotation speed is greater than or equal to 70 rpm and less than 105 rpm, the given d-axis current id* is set as the d-axis compensation current.

[0107] In some embodiments of the present application, when the rotation speed is greater than 70 rpm and less than or equal to 105 rpm, the given d-axis current id* is set as the d-axis compensation current.

[0108] In some embodiments of the present application, by increasing the current corresponding to a speed within the range of greater than or equal to 70 rpm and less than or equal to 105 rpm to the current corresponding to a speed of 105 rpm, the minimum stable speed of the fan can be equivalently reduced from 105 rpm to 70 rpm.

[0109] The specific value of the d-axis compensation current needs to be set according to different rotation speeds n*, which will be described in detail below.

[0110] The d-axis compensation current is the d-axis current corresponding to the relationship between the fitted speed n* and the d-axis current at different speeds n* within a speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm.

[0111] The d-axis current used for fitting the curve is calculated based on the q-axis current obtained when the fan is stably running at different speeds n* and the total motor current is when the fan is stably running at 105 rpm.

[0112] First, the relationship between different rotation speeds n* and the d-axis compensation current within a rotation speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm is established in advance.

[0113] Therefore, when the d-axis compensation current needs to be determined, it can be determined based on the relationship established above and the rotation speed n*.

[0114] As follows, it will be described how to establish the relationship between different rotation speeds n* and the d-axis compensation current within a rotation speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm.

[0115] (1) The d-axis current and the q-axis current of the outdoor fan are controlled when the outdoor fan is stably operating at the upper limit value of the first speed threshold.

[0116] When the outdoor fan runs at 105 rpm, the fan speed is relatively high and it is considered that the fan can run stably.

[0117] Based on this, the current at different speeds n* within the speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm is pulled up to the sampling current at a speed of 105 rpm through the d-axis compensation current, so that the equivalent minimum stable speed of the fan is reduced from 105 rpm to 70 rpm, ensuring that the lowest speed within the speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm is equivalent to the stable speed, and at the equivalent stable speed, the sampling current has high accuracy.

[0118] In some embodiments of the present application, when the outdoor fan runs at 105 rpm, the sampled current iA of phase A and the sampled current iB of phase B of the fan motor can be obtained, and the phase C current iC can be calculated using the formula iA+iB+iC=0.

[0119] The three-phase currents are transformed by Clark to obtain iα and iβ; then iα and iβ are transformed by Park to obtain the q-axis current iq and the d-axis current id.

[0120] (2) Using the d-axis current and the q-axis current, calculate the total motor current is as the reference current threshold.

[0121] Since the actual total motor current is satisfies the following: (is) 2 =(id) 2 +(iq) 2 .

[0122] Therefore, the total motor current is can be calculated using the d-axis current id and the q-axis current iq.

[0123] When the fan speed is lower than 105 rpm, the sampled current must be lower than the reference current threshold. Therefore, the sampled current is compensated to the reference current threshold by compensating the d-axis current.

[0124] That is, the current at different speeds n* within the speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm is pulled up to the sampling current at the speed of 105 rpm by the d-axis compensation current.

[0125] Therefore, the total motor current is calculated at a speed of 105 rpm is used as a reference current threshold to determine the d-axis current corresponding to different speeds n* within a speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm.

[0126] (3) Control the outdoor fan to operate stably at different speeds n* and obtain the q-axis current iq at different speeds n*.

[0127] When the fan operates at different speeds n* within the speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm, the MCU can calculate the q-axis current.

[0128] (4) According to the d-axis current id=sqrt(is 2 -iq 2 ), calculate the d-axis current id.

[0129] As mentioned above, the total motor current is at different speeds satisfies: (is) 2 =(id) 2 +(iq) 2 Therefore, if is (i.e., the reference current threshold) obtained in (2) and the q-axis current obtained in (3) are known, the d-axis current id can be easily obtained.

[0130] (5) According to different speeds n* and d-axis current id, a curve between the speed n* and the d-axis current is fitted to establish a relationship between the speed n* and the d-axis current id.

[0131] The d-axis current id at different speeds n* is obtained as above. Therefore, according to this information, a curve between the speed n* and the d-axis current can be fitted to establish a relationship between the speed n* and the d-axis current id.

[0132] In this way, when the speed n* is known, the corresponding d-axis current id can be determined according to the relationship to compensate the d-axis current, so as to increase the sampling current at the speed n* to the sampling current at 105 rpm, thereby improving the current sampling accuracy at low speed n*.

[0133] The different rotation speeds n* involved in S3 are all within a rotation speed range of greater than or equal to 70 rpm and less than or equal to 105 rpm.

[0134] S4: When the speed n* is greater than or equal to 44 rpm and less than 70 rpm, inertia speed reduction control is performed.

[0135] When the speed n* corresponding to the speed command reaches the lower limit value of the second speed threshold value and reaches the upper limit value of the third speed threshold value, the inertia speed reduction control is executed.

[0136] In some embodiments of the present application, the third speed threshold may be a speed range or a specific speed setting value.

[0137] For example, the speed and the third speed and the second speed are judged. If the speed is less than the second speed and greater than the third speed, inertia speed reduction control is performed; otherwise, the process returns to S1.

[0138] The above is just an example. When the speed n* reaches the lower limit value of the second speed threshold and reaches the upper limit value of the third speed threshold, that is, the speed n* is less than or equal to the second speed and greater than or equal to the third speed, or the speed n* is less than or equal to the second speed and greater than the first speed, or the speed n* is less than the second speed and greater than or equal to the third speed, inertia deceleration control can also be performed.

[0139] The third rotation speed may be set to 44 rpm to meet the wide speed range of 44 rpm to 105 rpm of the fan under extreme working conditions as mentioned in the background technology.

[0140] In some embodiments of the present application, when the speed n* is greater than 44 rpm and less than 70 rpm, inertia speed reduction control is performed, and a d-axis compensation current at a speed of 70 rpm is injected into the d-axis when the fan is running.

[0141] In some embodiments of the present application, when the speed n* is greater than or equal to 44 rpm and less than or equal to 70 rpm, inertia speed reduction control is performed, and a d-axis compensation current at a speed of 70 rpm is injected into the d-axis when the fan is running.

[0142] In some embodiments of the present application, when the speed n* is greater than 44 rpm and less than or equal to 70 rpm, inertia reduction control is performed, and a d-axis compensation current at a speed of 70 rpm is injected into the d-axis when the fan is running. At this time, FOC control is still used and the given d-axis current is not 0.

[0143] The determination of the d-axis compensation current when the speed n* is 70 rpm refers to the description in S3 above.

[0144] In order to perform inertia speed reduction control, in some embodiments of the present application, it is necessary to establish an equal air volume model based on 70 rpm in the range of speed n* greater than or equal to 44 rpm and less than 70 rpm, with the aim of increasing the speed in the range of speed n* greater than or equal to 44 rpm and less than 70 rpm to 70 rpm, and injecting a d-axis compensation current at a speed of 70 rpm into the d-axis when the fan is running.

[0145] The equal air volume model based on 70 rpm is a data model of air volume and rotation speed within a first preset time period (eg, 2 minutes).

[0146] Such wind volume models need to be established in advance and can be directly called when used.

[0147] According to such air volume model, the air volume Q1 generated by different speeds n* in the first preset time period within the speed range of greater than or equal to 44 rpm and less than 70 rpm can be used to determine the operation time R when the fan is running at 70 rpm and generating the air volume Q2 in the first preset time period. t and stop time S t .

[0148] Among them, the air volume Q1 and the air volume Q2 are equal.

[0149] That is, when the speed n* corresponding to the speed command is within the speed range of greater than or equal to 44 rpm and less than 70 rpm, the fan operates intermittently at 70 rpm.

[0150] Among them, when the speed n* corresponding to the speed command is different, the operation time Rt and the stop time St of the fan intermittently running at 70 rpm are different, which needs to be determined based on the equal air volume model.

[0151] For example, when the speed n* corresponding to the speed command is 50 rpm, the fan operates intermittently at 70 rpm for a running time of Rt1 and a stopping time of St1, wherein the air volume operating at 50 rpm in the first preset time period is equal to the air volume operating intermittently at 70 rpm in the first preset time period.

[0152] When the speed n* corresponding to the speed command is 60 rpm, the operation time of the fan intermittently running at 70 rpm is Rt2 and the stop time is St2, wherein the air volume operating at 60 rpm in the first preset time period is equal to the air volume operating intermittently at 70 rpm in the first preset time period.

[0153] In this way, by compensating for the D-axis current and inertia speed reduction control, the minimum stable speed of the fan can be reduced from 105 rpm to 44 rpm, enabling the fan to operate stably at a lower wind speed. Its performance is better than the minimum speed of 70 rpm of Midea's competitors.

[0154] As described above, the fan can be stably operated within a wide speed range of 44 rpm or more, and the sampling current can be increased to the sampling current at a stable speed of 105 rpm, thereby improving the sampling signal-to-noise ratio and thus improving the current sampling accuracy, ensuring that the observer accurately outputs the fan position information and ensuring the reliable operation of the fan.

[0155] As known from the background art, the minimum operating speed of the existing fan is 44 rpm, therefore, the present application only relates to the control of the fan whose speed command corresponds to a speed above 44 rpm.

[0156] During the inertia speed reduction control, in order to avoid the fan being uncontrollable and causing stalling, therefore, in some embodiments of the present application, see Figure 8 , during which speed fault-tolerant control is introduced.

[0157] The speed fault-tolerant control uses the observer in the MCU to observe the fan speed in real time, and determines the current operating state of the fan (including stationary and running) based on the fan speed.

[0158] During the inertia speed reduction control process, when the fan speed is reduced, the fan speed can be observed to know whether the fan has stopped, so as not to affect the restart.

[0159] At the same time, during the speed reduction process, external wind force can cause the fan speed to change. By introducing the speed tolerance control, the influence of external wind force on the fan speed can be avoided during the fan speed reduction process, ensuring that the fan operation state is controllable.

[0160] As mentioned above, speed tolerance control is to avoid the fan from affecting the restart of the fan (i.e., restarting after stopping) during intermittent operation of the fan.

[0161] In some embodiments of the present application, when the fan is intermittently operated at 70 rpm within a first preset time period, the fan status is determined by monitoring the fan speed.

[0162] The fan speed can be monitored by arranging a speed sensor, or by setting a carrier frequency timing cycle through the MCU to monitor the fan speed, or by using other technical means to monitor the fan speed.

[0163] In some embodiments of the present application, when the fan stops reducing speed and reduces speed to the minimum speed, it indicates that the fan is shut down.

[0164] The minimum speed is preset and can be set according to demand. In some embodiments of the present application, the minimum speed is less than the lower limit of the third speed threshold, for example, the minimum speed is set to 30 rpm.

[0165] Therefore, the fan status is determined by comparing the downtime St of the fan running at 70 rpm and the time t required for the fan to stop and slow down to 30 rpm, see Figure 8 The following description is given.

[0166] S11: When the time t required for the fan to go from running to stopping is less than the stopping time St, it means that the fan stopping time has not reached the stopping time St. Therefore, when the waiting time t is equal to the stopping time St, the fan starts to increase speed.

[0167] S12: When the time t required for the fan to go from running to stopping is equal to the stopping time St, it means that the fan stopping time just reaches the stopping time St, so the fan starts at high speed.

[0168] S13: When the time t required for the fan to go from running to stopping is greater than the stopping time St, it means that the fan needs to be started before it stops. This indicates that the stopping time St is too short. Therefore, it is necessary to call the equal air volume model based on the upper limit value of the fourth speed threshold to ensure that the fan can be started reliably again.

[0169] In some embodiments of the present application, the equal air volume model based on the upper limit value of the fourth speed threshold is an equal air volume model based on 80 rpm.

[0170] The equal air volume model based on 80 rpm is also pre-established, and the establishment method is the same as the equal air volume model based on 70 rpm as described above.

[0171] That is, an equal air volume model based on 80 rpm is established in the range of speed n* greater than or equal to 44 rpm and less than 80 rpm. The purpose is to increase the speed in the range of speed n* greater than or equal to 44 rpm and less than 80 rpm to 80 rpm, and inject the d-axis compensation current at a speed of 80 rpm into the d-axis when the fan is running.

[0172] The equal air volume model based on 80 rpm is a data model of air volume and rotation speed within a second preset time period (eg, 2 minutes).

[0173] According to such air volume model, the air volume Q1' generated by different speeds n* in the second preset time period within the speed range of greater than or equal to 44 rpm and less than 80 rpm can be used to determine the operation time R when the fan is running at 80 rpm and generating the air volume Q2' in the second preset time period. t ' and stop time S t '.

[0174] Among them, the air volume Q1' and the air volume Q2' are equal.

[0175] When the time t required for the fan to stop from running is greater than the stop time St, the equal air volume model based on 80rmp is called according to the speed n* corresponding to the speed command.

[0176] In this way, the stop time St' corresponding to the equal air volume model based on 80 rpm is obtained.

[0177] The stop time St' is compared with the time t required for the fan to stop from running to stopping to judge the state of the fan, that is, stationary or running, and then the process returns to S11.

[0178] The above speed fault-tolerant control can make the fan controllable during inertia speed reduction control. In this way, the inertia speed reduction control and d-axis current compensation are combined to improve the current sampling accuracy, ensure that the observer accurately outputs the fan position information, and ensure stable operation of the fan in a wide speed range.

[0179] See also Fig. 9 and Fig.10 , which schematically shows the control method of the fan at different speeds, among which the hysteresis control needs to be explained.

[0180] The hysteresis control here refers to the control strategy when the speed is between 70 rpm and 80 rpm.

[0181] When the speed corresponding to the speed command is greater than or equal to 70 rpm, the fan continues to operate in a closed loop.

[0182] Since the operation is continuous, there is no downtime, therefore, there is no inertia deceleration control during this phase.

[0183] When the speed corresponding to the speed command is greater than or equal to 44 rpm and less than 70 rpm, inertia speed reduction control is performed. If the fan is not uncontrollable as described above, inertia speed reduction control is continued during the period when the speed is greater than or equal to 44 rpm and less than 70 rpm.

[0184] Once the fan becomes uncontrollable and speed tolerance control needs to be introduced, the equal air volume model based on 80 rpm is called to perform inertia speed reduction measurement within the speed range of greater than or equal to 44 rpm and less than 70 rpm.

[0185] Therefore, the hysteresis control described above only describes the switching between the FOC closed-loop control and the inertia speed reduction control.

[0186] In the description of the above embodiments, specific features, structures, materials or characteristics may be combined in a suitable manner in any one or more embodiments or examples.

[0187] The above are only specific embodiments of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A fan control system, It is characterized in that include: The fan uses the given q-axis current iq* and the given d-axis current id* as the current loop input to perform FOC control on the IPM module when it starts; A processing unit configured to: S1: Get the speed command of the fan; S2: when the speed corresponding to the speed command reaches the upper limit of the first speed threshold, the given d-axis current id* is 0; S3: When the speed corresponding to the speed command reaches the lower limit of the first speed threshold and the upper limit of the second speed threshold, the given d-axis current id* is the d-axis compensation current; The d-axis compensation current is the d-axis current corresponding to the relationship between the fitted speed and the d-axis current at different speeds, and the d-axis current used for fitting the curve is calculated based on the q-axis current obtained when the fan is stably running at different speeds and the total motor current is when the fan is stably running at the upper limit value of the first speed threshold; S4: When the speed corresponding to the speed command reaches the lower limit of the second speed threshold and the upper limit of the third speed threshold, inertia speed reduction control is performed, and the inertia speed reduction control is specifically as follows: Using a pre-established equal air volume model based on the upper limit value of the second speed threshold, the operation time and the stop time of the fan at the upper limit value of the second speed threshold within a first preset time period are obtained, the operation of the fan is intermittently controlled, and when the fan is running, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the second speed threshold; Among them, the equal wind volume model based on the upper limit value of the second speed threshold is a data model of wind volume and speed within the first preset time period, and the wind volume generated by the fan at the upper limit value of the second speed threshold within the first preset time period is equal to the wind volume generated by the speed within the first preset time period.

2. The fan control system according to claim 1, It is characterized in that Fit the relationship between different speeds and d-axis current, specifically: controlling a d-axis current and a q-axis current of the fan when the fan is stably operated at an upper limit value of the first speed threshold; Using the d-axis current and the q-axis current, the total motor current is is calculated as a reference current threshold; Controlling the fan to operate stably at different speeds, and obtaining the q-axis current iq at different speeds; According to the d-axis current id=sqrt(is2-iq2), calculate the d-axis current id; According to different rotation speeds and d-axis current id, a curve between the rotation speed and the d-axis current is fitted, and a relationship between different rotation speeds and the d-axis current is established.

3. The fan control system according to claim 1, It is characterized in that When the inertia speed reduction control is executed, the rotation speed of the fan is monitored and the rotation speed is controlled for speed tolerance so as to control the fan to stop to meet the stop time.

4. The fan control system according to claim 3, It is characterized in that When the monitored rotation speed reaches the minimum rotation speed, it indicates that the fan is shut down.

5. The fan control system according to claim 4, It is characterized in that The speed fault tolerance control is specifically as follows: S11: when the time required for the fan to stop from running is less than the stop time, the fan is started at a higher speed when the required time is equal to the stop time; S12: When the time required for the fan to stop from running is equal to the stop time, the fan is started at a high speed; S13: When the time required for the fan to stop from running is greater than the stop time, a pre-established equal air volume model based on the upper limit value of the fourth speed threshold is called to obtain the operation time and stop time of the fan within the second preset time period at the upper limit value of the fourth speed threshold, and return to S11; Wherein, during the calling of the equal air volume model based on the upper limit value of the fourth speed threshold, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the fourth speed threshold when the fan is running; The equal wind volume model based on the upper limit value of the fourth speed threshold is a data model of wind volume and speed within the second preset time period. The wind volume generated by the fan at the upper limit value of the fourth speed threshold within the second preset time period is equal to the wind volume generated by the speed within the second preset time period.

6. An air conditioner, It is characterized in that include IPM module; The outdoor fan uses the given q-axis current iq* and the given d-axis current id* as the current loop input to perform FOC control on the IPM module when it starts; A processing unit configured to: S1: Get the speed command of the outdoor fan; S2: when the speed corresponding to the speed command reaches the upper limit of the first speed threshold, the given d-axis current id* is 0; S3: When the speed corresponding to the speed command reaches the lower limit of the first speed threshold and the upper limit of the second speed threshold, the given d-axis current id* is the d-axis compensation current; The d-axis compensation current is the d-axis current corresponding to the relationship between the fitted speed and the d-axis current at different speeds, and the d-axis current used for fitting the curve is calculated based on the q-axis current obtained when the outdoor fan is stably running at different speeds and the total motor current is when the outdoor fan is stably running at the upper limit value of the first speed threshold; S4: When the speed corresponding to the speed command reaches the lower limit of the second speed threshold and the upper limit of the third speed threshold, inertia speed reduction control is performed, and the inertia speed reduction control is specifically as follows: Using a pre-established wind volume model based on the upper limit value of the second speed threshold, the operation time and stop time of the outdoor fan at the upper limit value of the second speed threshold within a first preset time period are obtained, the operation of the outdoor fan is intermittently controlled, and when the fan is running, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the second speed threshold; Among them, the equal wind volume model based on the upper limit value of the second speed threshold is a data model of wind volume and speed within the first preset time period, and the wind volume generated by the outdoor fan at the upper limit value of the second speed threshold within the first preset time period is equal to the wind volume generated by the speed within the first preset time period.

7. The air conditioner according to claim 6, It is characterized in that Fit the relationship between different speeds and d-axis current, specifically: controlling the d-axis current and the q-axis current of the outdoor fan when the outdoor fan is stably operated at the upper limit value of the first speed threshold; Using the d-axis current and the q-axis current, the total motor current is is calculated as a reference current threshold; Controlling the outdoor fan to operate stably at different speeds, and obtaining the q-axis current iq at different speeds; According to the d-axis current id=sqrt(is2-iq2), calculate the d-axis current id; According to different rotation speeds and d-axis current id, the curves between different rotation speeds and d-axis currents are fitted, and the relationship between different rotation speeds and d-axis currents is established.

8. The air conditioner according to claim 6, It is characterized in that When the inertia speed reduction control is executed, the rotation speed of the outdoor fan is monitored and the rotation speed is controlled for speed tolerance so as to control the outdoor fan to stop to meet the stop time.

9. The air conditioner according to claim 8, It is characterized in that When the monitored rotation speed reaches the minimum rotation speed, it indicates that the outdoor fan is shut down.

10. The air conditioner according to claim 9, It is characterized in that The speed fault tolerance control is specifically as follows: S11: when the time required for the fan to stop from running is less than the stop time, the fan is started at a higher speed when the required time is equal to the stop time; S12: When the time required for the fan to stop from running is equal to the stop time, the fan is started at a high speed; S13: When the time required for the outdoor fan to stop from running is greater than the stop time, a pre-established equal air volume model based on the upper limit value of the fourth speed threshold is called to obtain the running time and the stopping time of the outdoor fan in the second preset time period at the upper limit value of the fourth speed threshold, and return to S11; Wherein, during the calling of the equal air volume model based on the upper limit value of the fourth speed threshold, a d-axis compensation current is injected into the d-axis when the speed is the upper limit value of the fourth speed threshold when the fan is running; The equal wind volume model based on the upper limit value of the fourth speed threshold is a data model of wind volume and speed within the second preset time period. The wind volume generated by the outdoor fan at the upper limit value of the fourth speed threshold within the second preset time period is equal to the wind volume generated by the speed within the second preset time period.

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