Air conditioning system and permanent magnet synchronous motor starting method

Abstract

This invention discloses an air conditioning system and a starting method for a permanent magnet synchronous motor (PMSM). The air conditioning system includes a processing unit configured to: send drive pulses to the switches in three lower bridge arms according to a PWM cycle, and determine the minimum back electromotive force (EMF) based on the bus current; continuously send drive pulses to the switch in the lower bridge arm corresponding to the minimum back EMF during a first time period, and determine the first phase based on the bus current during a second time period; continuously send drive pulses to the switch in the lower bridge arm corresponding to the back EMF that lags the minimum back EMF by 120° during a second time period, and determine the second phase based on the bus current during a third time period; continuously send drive pulses to the switch in the remaining lower bridge arm during a third time period, and determine the third phase based on the bus current during a third time period; and repeat the above steps to obtain the phase information of the outdoor fan. This invention determines the phase information and speed of the PMSM during startup through software, exhibiting low parameter dependence.

Description

Technical Field

[0001] This invention relates to the field of air conditioning system control technology, and in particular to an air conditioning system for starting control of a permanent magnet synchronous motor in an air conditioning system, and a method for starting the permanent magnet synchronous motor. Background Technology

[0002] The outdoor unit fan of a variable frequency air conditioner uses a permanent magnet synchronous motor (PMSM), which is easily affected by natural wind and may rotate with or against the wind. Therefore, starting with or against the wind is a basic function that most outdoor fans must meet.

[0003] Due to limitations in cost, size, and installation, PMSM control systems are gradually eliminating position sensors and instead using a single current sensor or a single resistor to sample the inverter's DC bus current. The motor phase current is then reconstructed using an algorithm to achieve PMSM control. In other words, PMSM sensorless control is based on sampling by a single resistor (current sensor).

[0004] Under both tailwind and headwind conditions, permanent magnet synchronous motors will rotate. For permanent magnet synchronous motors with sensors, the rotor position can be measured in real time, so the fan can be directly pulled back to forward rotation and started normally through closed-loop FOC (Field-Oriented Control). However, for permanent magnet synchronous motors without sensors, it is difficult to obtain rotor position information and speed during startup.

[0005] If a permanent magnet synchronous motor starts without estimating its position and speed when it has an initial velocity, it will inevitably cause a large current surge, leading to start-up failure.

[0006] Therefore, reliably obtaining the position and speed of the permanent magnet synchronous motor at startup is an important means to reliably start the permanent magnet synchronous motor. Summary of the Invention

[0007] To address the aforementioned technical problems, embodiments of the present invention provide an air conditioning system that determines the phase information and speed of a permanent magnet synchronous motor during startup by controlling the switching transistors in the IPM module and sampling the bus current, thereby ensuring reliable startup control of the permanent magnet synchronous motor.

[0008] To achieve the above-mentioned objectives, the present invention employs the following technical solution:

[0009] In some embodiments of this application, this application relates to an air conditioning system, including: an outdoor fan, an IPM module, and a processing unit.

[0010] To address the difficulty of starting outdoor fans when rotating with or against the wind, this method analyzes the three-phase back electromotive force and combines the switching on / off state of the switching transistors in the three lower arms of the IPM module with the DC bus current to determine the phase information and speed of the outdoor fan. This method does not require additional hardware, has low parameter dependence, and can meet the practicality, reliability, and operability requirements of actual engineering projects.

[0011] In some embodiments of this application, the processing unit is configured to: (1) send drive pulses to the switching transistors in the three lower bridge arms of the IPM module in a time-division manner according to the PWM cycle, and determine the minimum back electromotive force of the PMSM based on the bus current during the sending period;

[0012] (2) During the first time period, drive pulses are continuously sent to the switch in the lower bridge arm L1 corresponding to the minimum back EMF, and the first phase is determined according to the bus current;

[0013] (3) During the second time period, drive pulses are continuously sent to the switch in the lower bridge arm corresponding to the back EMF with a lag of 120°, and the second phase is determined according to the bus current.

[0014] (4) During the third time period, drive pulses are continuously sent to the switch in the remaining lower bridge arm, and the third phase is determined according to the bus current;

[0015] (5) Repeat (2) to (4) to obtain the phase information of the outdoor fan.

[0016] In some embodiments of this application, the processing unit is further configured to determine the rotational speed based on the time difference between the 120° phase difference and the adjacent phases in the first, second, and third phases.

[0017] By analyzing the relationship between the three back electromotive forces, for the control of the switching transistors in the three lower arms of the IPM module, if the bus current is not detected, it indicates that the corresponding back electromotive force is the minimum back electromotive force during the current signal transmission period.

[0018] In some embodiments of this application, when the wind speeds in the headwind and headwind are low, resulting in low rotation speeds of the outdoor fan in the headwind and headwind, or when the pulse width of the drive pulse is small, even if the back electromotive force is not at its minimum, the bus current may not be detected. Therefore, when the rotation speeds of the outdoor fan in the headwind and headwind are lower than the first preset value, or when the pulse width of the drive pulse is lower than the second preset value, the pulse width of the drive pulse is gradually increased until the relationship between the three back electromotive forces can be confirmed.

[0019] In some embodiments of this application, the IPM module is used to invert the bus voltage into three-phase AC power for the outdoor fan. When the outdoor fan starts, the IPM module is subjected to FOC control, and the FOC control outputs a PWM wave.

[0020] The frequency of the drive pulse is equal to the frequency of the PWM wave.

[0021] In some embodiments of this application, in order to accurately obtain the phase information of the outdoor fan, it is necessary to compensate the obtained phase information.

[0022] The air conditioning system also includes a compensation unit, which is used to compensate for phase information.

[0023] In some embodiments of this application, after obtaining the rotational speed of the outdoor fan, the compensation phase is obtained by calculating the product of the rotational speed and the pulse width of the pulse signal, and then the first phase is updated to be the sum of the first phase and the compensation phase.

[0024] In some embodiments of this application, this application also relates to a method for starting a permanent magnet synchronous motor, which determines the phase information and speed of the permanent magnet synchronous motor in the manner described above, and starts the permanent magnet synchronous motor with the phase information and speed.

[0025] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 This is the circuit diagram of the IPM module of the PMSM.

[0028] Figure 2 The diagram shows the waveforms of the three back electromotive forces of the PMSM and the schematic of the drive pulses applied to the three switching transistors in the three lower arms of the IPM module. Figure 1 ;

[0029] Figure 3 The circuit diagram is for the IPM module of the PMSM, showing the current path when the switch V2 in the lower bridge arm of the IPM module is turned on at or near point A.

[0030] Figure 4 The circuit diagram is for the IPM module of the PMSM, showing the current path when the switch V2 in the lower bridge arm of the IPM module is off at or near point A.

[0031] Figure 5 The circuit diagram is for the IPM module of the PMSM, showing the current path when the switch V6 in the lower bridge arm of the IPM module is turned on at or near point A.

[0032] Figure 6 The circuit diagram is for the IPM module of the PMSM, showing the current path when the switch V6 in the lower bridge arm of the IPM module is off at or near point A.

[0033] Figure 7 This is a circuit diagram of the IPM module of the PMSM, showing the current path when the switch V4 in the lower bridge arm of the IPM module is turned on to determine the 90-degree phase.

[0034] Figure 8 This is a circuit diagram of the IPM module of the PMSM, showing the current path when the switch V4 in the lower bridge arm of the IPM module is off, used to determine the 90-degree phase.

[0035] Figure 9 This is a circuit diagram of the IPM module of the PMSM, showing the current path when the switch V6 in the lower bridge arm of the IPM module is turned on, used to determine the 210-degree phase.

[0036] Figure 10 This is a circuit diagram of the IPM module of the PMSM, showing the current path when the switch V6 in the lower bridge arm of the IPM module is off, used to determine the 210-degree phase.

[0037] Figure 11 This is a circuit diagram of the IPM module of the PMSM, showing the current path when the switch V2 in the lower bridge arm of the IPM module is turned on, which is used to determine the phase of 330 degrees.

[0038] Figure 12 The circuit diagram is for the IPM module of the PMSM, showing the current path when the switch V2 in the lower bridge arm of the IPM module is off, which is used to determine the phase of 330 degrees.

[0039] Figure 13 The diagram shows the waveforms of the three back electromotive forces of the PMSM and the schematic of the drive pulses applied to the three switching transistors in the three lower arms of the IPM module. Figure 2 . Detailed Implementation

[0040] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments.

[0041] Based on the embodiments of this invention, all other embodiments obtained by those skilled in the art without inventive effort are within the scope of protection of this invention. In the description of this invention, it should be understood that the terms "center," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," 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 this invention and simplifying the description, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of this invention.

[0042] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection. Those skilled in the art can understand the specific meaning of the above terms in this invention based on the specific circumstances. In the description of the above embodiments, specific features, structures, materials, or characteristics can be combined in any suitable manner in one or more embodiments or examples.

[0043] The terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0044] [Basic Operating Principles of Air Conditioners]

[0045] Air conditioners execute a cooling and heating cycle using a compressor, condenser, expansion valve, and evaporator. This cycle involves a series of processes—compression, condensation, expansion, and evaporation—to cool or heat an indoor space.

[0046] Low-temperature, low-pressure refrigerant enters the compressor, which compresses it into a high-temperature, 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 heat is released to the surrounding environment through the condensation process.

[0047] The expansion valve expands the high-temperature, high-pressure liquid refrigerant that condenses in the condenser into a low-pressure liquid refrigerant. The evaporator evaporates the expanded refrigerant in the expansion valve and returns the low-temperature, low-pressure refrigerant gas to the compressor. The evaporator achieves its cooling effect by utilizing the latent heat of refrigerant evaporation to exchange heat with the material being cooled. Throughout the cycle, the air conditioner regulates the temperature of the indoor space.

[0048] The outdoor unit of an air conditioner refers to the part of the refrigeration cycle that includes the compressor, outdoor heat exchanger, and outdoor fan. The indoor unit of an air conditioner includes the indoor heat exchanger and indoor fan, and a throttling device (such as a capillary tube or electronic expansion valve) can be provided in either the indoor or outdoor unit.

[0049] The indoor and outdoor heat exchangers function as either condensers or evaporators. When the indoor heat exchanger is used as a condenser, the air conditioner operates in heating mode; when it is used as an evaporator, the air conditioner operates in cooling mode.

[0050] The indoor and outdoor heat exchangers are converted into condensers or evaporators, which is generally done using a four-way valve. For details, please refer to the settings of conventional air conditioners, which will not be elaborated here.

[0051] The working principle of an air conditioner is as follows: the compressor operates to bring the indoor heat exchanger (which is the evaporator in the indoor unit) to an ultra-low pressure state. The liquid refrigerant in the indoor heat exchanger evaporates rapidly and absorbs heat. The air blown out by the indoor fan is cooled by the indoor heat exchanger coil and then blown into the room as cold air. The vaporized refrigerant is pressurized by the compressor and condenses into a liquid state in the high-pressure environment of the outdoor heat exchanger (which is the condenser in the outdoor unit), releasing heat. The heat is then dissipated into the atmosphere by the outdoor fan. This cycle achieves the cooling effect.

[0052] The working principle of an air conditioner for heating is as follows: Gaseous refrigerant is pressurized by the compressor, becoming a high-temperature, high-pressure gas. This gas enters the indoor heat exchanger (which acts as a condenser), where it condenses and liquefies, releasing heat and becoming a liquid. Simultaneously, it heats the indoor air, thus raising the indoor temperature. The liquid refrigerant is then depressurized by a throttling device and enters the outdoor heat exchanger (which acts as an evaporator). There, it evaporates and absorbs heat, becoming a gas again. Simultaneously, it absorbs heat from the outdoor air (making the outdoor air cooler), becoming a gaseous refrigerant once more, and then re-enters the compressor to begin the next cycle.

[0053] Outdoor or indoor fans are generally permanent magnet synchronous fans, and the motor in a permanent magnet synchronous fan is a permanent magnet synchronous motor (PMSM).

[0054] The fans mentioned in this article generally refer to outdoor fans, because outdoor units are installed outdoors and are affected by natural winds, resulting in forward and reverse rotation.

[0055] [IPM Module]

[0056] See Figure 1 It shows the circuit diagram of the IPM (Intelligent Power Module) module 20 of PMSM 10.

[0057] The IPM module 20 includes a three-phase power inverter that converts the DC bus voltage into three-phase AC power U. A U B U C It is used to drive PMSM 10.

[0058] The three-phase power inverter consists of six switching transistors: transistor V1 for the first upper bridge arm (i.e., the U-phase upper bridge arm), transistor V3 for the second upper bridge arm (i.e., the V-phase upper bridge arm), transistor V5 for the third upper bridge arm (i.e., the W-phase upper bridge arm), transistor V2 for the first lower bridge arm (i.e., the U-phase lower bridge arm), transistor V4 for the second lower bridge arm (i.e., the V-phase lower bridge arm), and transistor V6 for the third lower bridge arm (i.e., the W-phase lower bridge arm).

[0059] The connection point between switch V1 in the upper U-phase bridge arm and switch V2 in the lower U-phase bridge arm is connected to the U-phase winding of the permanent magnet synchronous motor. The connection point between switch V3 in the upper V-phase bridge arm and switch V4 in the lower V-phase bridge arm is connected to the V-phase winding of the permanent magnet synchronous motor. The connection point between switch V5 in the upper W-phase bridge arm and switch V6 in the lower W-phase bridge arm is connected to the W-phase winding of the permanent magnet synchronous motor.

[0060] In each bridge arm, a freewheeling diode is connected in reverse parallel to the switching transistor, namely, a freewheeling diode D1 is connected in parallel to switching transistor V1, a freewheeling diode D2 is connected in parallel to switching transistor V2, a freewheeling diode D3 is connected in parallel to switching transistor V3, a freewheeling diode D4 is connected in parallel to switching transistor V4, a freewheeling diode D5 is connected in parallel to switching transistor V5, and a freewheeling diode D6 is connected in parallel to switching transistor V6.

[0061] In some embodiments of this application, a processing unit (not shown) is used to perform the process of acquiring phase information and speed information of the permanent magnet synchronous motor PMSM10.

[0062] The process of the processing unit acquiring the phase information of the permanent magnet synchronous motor PMSM 10 is described below.

[0063] To facilitate the description of the relationship between the three phases Eu, Ev and Ew of the PMSM 10 permanent magnet synchronous motor, the PMSM 10 under natural wind conditions is divided into two cases: running with the wind and running against the wind.

[0064] The methods for obtaining phase information and rotational speed are the same in both cases of turning with the wind and turning against the wind.

[0065] The following explanation uses the example of turning with the wind.

[0066] As is well known, the mainstream control algorithm for PMSM 10 is Field-Oriented Control (FOC), also known as vector control.

[0067] The FOC control performs inverter control on the IPM module 20. The FOC control outputs a PWM signal, which controls the IPM module 20, and the IPM module 20 drives the PMSM 10 to rotate.

[0068] When the PMSM 10 permanent magnet synchronous wind turbine rotates under natural wind conditions, the three back electromotive forces Eu, Ev, and Ew generated during its rotation are described in [reference needed]. Figure 2 The back electromotive forces Eu, Ev and Ew are 120° out of phase with each other, and their magnitudes change according to a sinusoidal law.

[0069] See Figure 1 and Figure 2 When any one of the switching transistors V2, V4, and V6 in the first, second, and third lower bridge arms is turned on, whether there is a motor induced current in the motor winding depends on the magnitude and phase of the electromotive force of the corresponding phase of that lower bridge arm.

[0070] See Figure 2 At point A or near it, the back electromotive force of U, Eu, and the back electromotive force of W, Ew, are both positive and greater than the back electromotive force of V, Ev, where the back electromotive force of V, Ev, is negative.

[0071] See again Figure 1 If the drive pulse is sent to the switch V4 in the lower arm of phase V at this time, the switch V4 will not be turned on because its Ev is at its minimum.

[0072] Furthermore, since Eu is positive and greater than Ev, and Ew is positive and greater than Ev, the freewheeling diodes D2 and D6 are turned off due to reverse voltage.

[0073] Therefore, when only the switch V4 in the lower arm of phase V is turned on at or near point A, no motor induced current will be generated.

[0074] If only switch V2 in the lower arm of phase U or switch V6 in the lower arm of phase W is turned on at or near point A, a motor induced current will be generated, as explained below.

[0075] refer to Figure 2 When a drive pulse is sent to switch V2 in the lower arm of phase U at or near point A, since Eu is positive and at its maximum, when switch V2 is turned on, the induced current of the motor forms a loop through switch V2, freewheeling diode D4, and freewheeling diode D6. Figure 3 As shown.

[0076] When the drive pulse turns off the switch V2, the induced current of the motor forms a loop through the freewheeling diodes D1, D4, and D6 in the upper bridge arm of phase U. Figure 4 As shown.

[0077] At this time, the single-resistor sampling module can collect the bus current idc.

[0078] The single-resistor sampling module specifically includes a single resistor R, which is connected to the negative terminal of the DC bus. The single resistor R detects the induced current of the motor through the freewheeling mode. The bus current sampled by the single resistor R is called idc.

[0079] Similarly, at or near point A, when a drive pulse is sent to the switch V6 in the lower arm of phase W, since Ew is greater than Ev, when switch V6 is turned on, the induced current of the motor forms a loop through switch V6 and freewheeling diode D4, such as... Figure 5 As shown.

[0080] When the drive pulse turns off V6, the induced current of the motor flows through the freewheeling diode D5 in the upper arm of phase V, forming a loop with the freewheeling diode D4. Figure 6 As shown.

[0081] At this time, the single-resistor sampling module can collect the bus current idc.

[0082] Thus, at or near point A, only when the switch V4 in the lower arm of phase V is turned on / off can the bus current IDC be undetectable (i.e., the bus current IDC is zero), and see [reference needed]. Figure 2 At or near point A, the back electromotive force Ev is exactly at its minimum. Therefore, the minimum back electromotive force can be detected based on this detection principle.

[0083] Therefore, at or near point A, drive pulses are sent time-divisionally to switch V2 in the lower arm of phase U, switch V4 in the lower arm of phase V, and switch V6 in the lower arm of phase W, and the minimum back electromotive force is determined based on the magnitude of the detected bus current IDC.

[0084] See Figure 2 At or near point A, drive pulses are sent to switching transistors V2, V4, and V6 in a time-division manner according to the PWM cycle. If the bus current IDC cannot be detected only when a drive pulse is sent to switching transistor V4, it indicates that the back electromotive force Ev of V is the minimum back electromotive force and the phase is within 90 degrees.

[0085] See Figure 2 First, a drive pulse ① is sent to the switching transistor V2, and the switching transistor V2 is turned on (see...). Figure 3 After energy storage, the switching transistor V2 is turned off (see...). Figure 4When this occurs, the bus current IDC will be detected.

[0086] Secondly, a drive pulse ② is sent to the switch V4. After the switch V4 is turned on to store energy, when the switch V4 is turned off, the back electromotive force Ev of V is at its minimum. Therefore, the bus current idc will not be detected at this time.

[0087] Finally, a drive pulse ③ is sent to the switching transistor V6, and the switching transistor V6 is turned on (see...). Figure 5 After energy storage, the switching transistor V6 is disconnected (see...). Figure 6 When this happens, the bus current IDC will be detected.

[0088] It should be noted that when determining the minimum back electromotive force, it is not necessary to send drive pulses to switch V2, switch V4 and switch V6 in the order of switch V2 in the lower bridge arm of phase U, switch V4 in the lower bridge arm of phase V and switch V6 in the lower bridge arm of phase W in sequence. It is sufficient to send drive pulses to switch V2, switch V4 and switch V6 in a time-division manner within the time period.

[0089] Point A is a randomly selected control point for input control, meaning that the phase and speed information of the PMSM 10 permanent magnet synchronous motor are acquired starting from point A.

[0090] In some embodiments of this application, the control points can be arbitrarily selected.

[0091] Control points can be selected Figure 2 Point A' in the diagram.

[0092] The difference between point A' and point A is that when driving pulses are sent to switching transistors V2, V4, and V6 in a time-division manner, the bus current IDC cannot be detected only when driving pulses are sent to switching transistor V6. This indicates that the back electromotive force Ew of W is the minimum back electromotive force and the phase is between 90 degrees and 210 degrees.

[0093] Control points can be selected Figure 2 Point A'' in the middle.

[0094] The difference between point A'' and point A is that when driving pulses are sent to switching transistors V2, V4, and V6 in a time-division manner, the bus current IDC cannot be detected only when driving pulses are sent to switching transistor V2. This indicates that the back electromotive force Eu of U is the minimum back electromotive force and the phase is between 210 degrees and 330 degrees.

[0095] In some embodiments of this application, after the processing unit determines the minimum back electromotive force, it needs to determine the phase information.

[0096] See Figure 2 We will still use point A as the control point for description.

[0097] As shown above, the back electromotive force Ev of phase V has been determined to be the minimum back electromotive force. Then, drive pulses are sent to the switch V4 in the lower arm of phase V, the switch V6 in the lower arm of phase W, and the switch V2 in the lower arm of phase U to obtain phase information. The specific description is as follows.

[0098] (1) During the first time period, according to the PWM cycle, drive pulses are continuously sent only to the switch V4 in the lower arm of phase V until drive pulse ④ is sent. The induced current of the motor then forms a loop through the switch V4 and the freewheeling diode D6, such as Figure 7 As shown, it is used for energy storage.

[0099] When the drive pulse turns off the switching transistor V4, the induced current in the motor will form a loop through the freewheeling diodes D3 and D6, such as... Figure 8 As shown.

[0100] At this point, the single-resistor sampling module can sample the bus current IDC, and the phase at this moment is 90 degrees, which is recorded as the first phase.

[0101] It should be noted that the drive pulse is a pulse with both high and low levels. A high level of the drive pulse can turn on the switching transistor, and a low level of the drive pulse can turn off the switching transistor.

[0102] (2) After a 90-degree phase change, during the second time period, according to the PWM cycle, drive pulses are continuously sent only to the switch V6 in the lower bridge arm of phase W until drive pulse ⑤ is sent. At this time, the induced current of the motor forms a circuit through the switch V6 and the freewheeling diode D2, such as Figure 9 As shown, it is used for energy storage.

[0103] When the drive pulse turns off the switching transistor V6, the induced current in the motor will flow through the freewheeling diodes D5 and D2, forming a loop, such as... Figure 10 As shown.

[0104] At this point, the single-resistor sampling module can sample the bus current IDC, and the phase at this moment is 210 degrees, which is denoted as the second phase.

[0105] (3) After the 210-degree phase, during the third time period, according to the PWM cycle, only the switching transistor V2 in the lower bridge arm of phase U is continuously driven by a drive pulse until drive pulse ⑥ is issued. At this time, the induced current of the motor forms a circuit through the switching transistor V2 and the freewheeling diode D4, such as Figure 11 As shown, it is used for energy storage.

[0106] When the drive pulse turns off the switching transistor V2, the induced current in the motor will flow through the freewheeling diodes D1 and D4, forming a loop, such as... Figure 12 As shown.

[0107] At this point, the single-resistor sampling module can sample the bus current IDC, and the phase at this moment is 330 degrees, which is recorded as the third phase.

[0108] The above (1), (2) and (3) have a sequential relationship.

[0109] (4) Repeat the above operations from (1) to (3) to obtain the phase information of the outdoor fan.

[0110] In some embodiments of this application, if the control point is selected as point A', and the back electromotive force Ew of phase W is the minimum back electromotive force, then drive pulses are continuously sent to the switch V6 in the lower arm of phase W during the first time period, to the switch V2 in the lower arm of phase U during the second time period, and to the switch V4 in the lower arm of phase V during the third time period.

[0111] In some embodiments of this application, if the control point is selected as point A'', the back electromotive force Eu of phase U is the minimum back electromotive force, and then, driving pulses are continuously sent to the switch V2 in the lower arm of phase U during the first time period, to the switch V4 in the lower arm of phase V during the second time period, and to the switch V6 in the lower arm of phase W during the third time period.

[0112] The frequency of the drive pulses described above is the frequency of the PWM wave, which is the PWM wave output to the IPM module after being controlled by the FOC.

[0113] The PWM period is the period of the PWM wave.

[0114] The outdoor fan speed is calculated based on the 120-degree phase difference and the time difference Δt between two adjacent phases in the first, second, and third phases.

[0115] That is, the rotational speed n = (2π / 3) / Δt.

[0116] The phase information calculated above has phase deviations at 90 degrees, 210 degrees and 330 degrees due to the presence of the driving pulse. Therefore, the phase information can be compensated by a compensation unit (not shown).

[0117] Specifically, the compensation unit can calculate the product Δθ of the pulse width d of the driving pulse and the rotational speed n, and use the calculated product Δθ to compensate for the phase information.

[0118] Update the previous 90-degree phase using 90 degrees + Δθ, update the previous 210-degree phase using 210 degrees + Δθ, and update the previous 330-degree phase using 330 degrees + Δθ.

[0119] Without adding additional hardware, the phase information and speed of the PMSM 10 permanent magnet synchronous motor are obtained through software control. The parameters are low-dependent, which can ensure the reliable start-up of the PMSM 10 permanent magnet synchronous motor.

[0120] When the speed of the tailwind is low or the pulse width of the drive pulse is small, the current of each phase is very small. Therefore, even if the back electromotive force is not at its minimum, the bus current IDC may not be detected.

[0121] Therefore, the pulse width of the driving pulse is started from the minimum pulse width and gradually increased. The above process is repeated until the three back electromotive forces relationship can be confirmed.

[0122] For reference: Figure 13 It shows the phases of the three back electromotive forces Eu, Ev and Ew under the condition of reverse rotation and the application of the drive pulse to the switching transistors V2 / V4 / V6 in the three lower bridge arms.

[0123] When rotating against the wind, the method for obtaining phase information and rotation speed is the same as when rotating with the wind, only the phase is reversed.

[0124] refer to Figure 13 As mentioned above, the phase angles of the U phase, W phase, and V phase differ from each other by 120°.

[0125] See Figure 13 The drive pulse ① is sent to switch V2, the drive pulse ② is sent to switch V4, and the drive pulse ③ is sent to switch V6 in turn. Only when the drive pulse is sent to switch V6 in the lower arm of phase W, the bus current IDC cannot be collected. This indicates that the back electromotive force Ew of phase W is the smallest and the phase is above 270 degrees.

[0126] As shown above, the back electromotive force Ew of phase W has been determined to be the minimum back electromotive force. Then, drive pulses are sent to switch V6 in phase W, switch V4 in phase V, and switch V2 in phase U to obtain phase information. The specific description is as follows.

[0127] (1') During the first time period, according to the PWM cycle, drive pulses are continuously sent only to the switch V6 in the lower bridge arm of phase W until drive pulse ④ is sent. The induced current of the motor then forms a loop through the switch V6 and the freewheeling diode D4, such as Figure 5 As shown, it is used for energy storage.

[0128] When the drive pulse turns off the switching transistor V6, the induced current in the motor will form a loop through the freewheeling diodes D5 and D4, such as... Figure 6 As shown.

[0129] At this point, the single-resistor sampling module can sample the bus current IDC, and the phase at this moment is 270 degrees, which is recorded as the fourth phase.

[0130] (2') After the 270-degree phase, during the second time period, only the switch V4 in the lower bridge arm of phase V is continuously driven by a drive pulse until the drive pulse ⑤ is issued. The motor induced current forms a circuit (not shown) through the switch V4 and the freewheeling diode D2 for energy storage.

[0131] When the drive pulse turns off the switching transistor V4, the induced current of the motor will form a loop through the freewheeling diodes D3 and D2 (not shown).

[0132] At this point, the single-resistor sampling module can sample the bus current IDC, and the phase at this moment is 150 degrees, which is recorded as the fifth phase.

[0133] (3') After 150 degrees of phase, during the third time period, only the switch V2 in the lower bridge arm of phase U is continuously driven by a driving pulse until the driving pulse ⑥ is issued. The motor induced current forms a circuit (not shown) through the switch V2 and the freewheeling diode D6 for energy storage.

[0134] When the drive pulse turns off the switching transistor V2, the induced current of the motor will form a loop through the freewheeling diodes D1 and D6 (not shown).

[0135] At this point, the single-resistor sampling module can sample the bus current IDC, and the phase at this moment is 30 degrees, which is recorded as the sixth phase.

[0136] The above (1'), (2') and (3') have a sequential relationship.

[0137] (4) Repeat the above operations from (1) to (3) to obtain the phase information of the outdoor fan.

[0138] The outdoor fan speed is calculated based on the 120-degree phase difference and the time difference Δt between two adjacent phases in the fourth, fifth, and sixth phases.

[0139] That is, the rotational speed n = (2π / 3) / Δt.

[0140] When the speed of the reverse wind is low or the pulse width of the drive pulse is small, even if the reverse electromotive force is not at its minimum, the bus current IDC may not be detected, and the current of each phase is very small.

[0141] Therefore, the pulse width of the driving pulse is started from the minimum pulse width and gradually increased. The above process is repeated until the three back electromotive forces relationship can be confirmed.

[0142] Similarly, if the rotation is with the wind, the phase information also needs to be compensated when rotating against the wind. The compensation method is the same as that for the case of rotation with the wind, and will not be elaborated here.

[0143] This application also relates to a starting method for a permanent magnet synchronous motor (PMSM 10), which realizes the starting of the PMSM 10 by determining the phase information and speed information of the PMSM 10.

[0144] The methods for determining phase and speed information are as described above and will not be repeated here. This starting method also has the advantages described above.

[0145] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions claimed by the present invention.

Claims

1. An air conditioning system, characterized in that, include: Outdoor fan; IPM module; The processing unit is configured as follows: (1) Drive pulses are sent to the switching transistors in the three lower arms of the IPM module in a time-sharing manner according to the PWM cycle. During the sending period, the minimum back EMF of the outdoor fan is determined according to the bus current. Specifically, drive pulses are sent to the three switching transistors in the three lower arms of the IPM module in a time-sharing manner. If the bus current can be detected during the time period of sending drive pulses to the switching transistors in two of the lower arms, and the bus current cannot be detected during the time period of sending drive pulses to the switching transistors in the remaining lower arm, then the minimum back EMF is the back EMF of a certain phase corresponding to the remaining lower arm. (2) During the first time period, drive pulses are continuously sent to the switch in the lower arm corresponding to the minimum back EMF, and the first phase is determined according to the bus current; (3) During the second time period, drive pulses are continuously sent to the switch in the lower bridge arm corresponding to the back EMF with a lag of 120°, and the second phase is determined according to the bus current. (4) During the third time period, drive pulses are continuously sent to the switch in the remaining lower bridge arm, and the third phase is determined according to the bus current; (5) Repeat (2) to (4) to obtain the phase information of the outdoor fan; It is configured to determine the rotational speed based on the time difference between the 120° phase difference and the adjacent phases in the first, second and third phases, specifically the rotational speed n = (2π / 3) / Δt.

2. The air conditioning system according to claim 1, characterized in that, When the outdoor fan speed is lower than the first preset value in both the windward and reverse directions, or when the pulse width of the drive pulse is lower than the second preset value, the pulse width of the drive pulse is gradually increased until the minimum back electromotive force of the outdoor fan can be determined based on the bus current during the signal transmission period when the drive pulse is sent to the three switching transistors in the three lower bridge arms of the IPM module in a time-sharing manner.

3. The air conditioning system according to claim 1, characterized in that, The IPM module is used to invert the bus voltage into three-phase AC power for the outdoor fan. When the outdoor fan starts, the IPM module is subjected to FOC control, and the FOC control outputs a PWM wave.

4. The air conditioning system according to claim 1, characterized in that, The air conditioning system also includes: The compensation unit is used to compensate for phase information.

5. A starting method for a permanent magnet synchronous motor, characterized in that, include: S1: According to the PWM cycle, drive pulses are sent to the switching transistors in the three lower bridge arms of the IPM module in a time-sharing manner. During the sending period, the minimum back EMF of the PMSM is determined according to the bus current. Specifically, drive pulses are continuously sent to the three switching transistors in the three lower bridge arms of the IPM module in a time-sharing manner. If the bus current can be detected during the time period of sending drive pulses to the switching transistors in two of the lower bridge arms, and the bus current cannot be detected during the time period of sending drive pulses to the switching transistors in the remaining lower bridge arm, then the minimum back EMF is the back EMF of a certain phase corresponding to the remaining lower bridge arm. S2: During the first time period, drive pulses are continuously sent to the switch in the lower bridge arm corresponding to the minimum back EMF, and the first phase is determined according to the bus current. S3: During the second time period, drive pulses are continuously sent to the switch in the lower bridge arm corresponding to the back EMF with a lag of 120° minimum back EMF, and the second phase is determined according to the bus current. S4: During the third time period, drive pulses are continuously sent to the switch in the remaining lower bridge arm to determine the third phase based on the bus current; S5: Return to S2 until the phase information of the outdoor fan is obtained; S6: Determine the rotational speed based on the 120° phase difference and the time difference between adjacent phases in the first, second, and third phases, specifically the rotational speed n = (2π / 3) / Δt; S7: Controls the permanent magnet synchronous motor to start based on phase information and speed.

6. The starting method for a permanent magnet synchronous motor according to claim 5, characterized in that, According to the PWM cycle, drive pulses are sent to the three switches in the three lower bridge arms of the IPM module in a time-sharing manner. During the signal transmission period, the minimum back electromotive force of the PMSM is determined based on the bus current, specifically: If, during the time-sharing process, drive pulses are continuously sent to three switches in the three lower arms of the IPM module, and bus current can be detected during the time period when drive pulses are sent to the switches in two of the lower arms, but bus current cannot be detected during the time period when drive pulses are sent to the switches in the remaining lower arm, then the minimum back electromotive force is the back electromotive force of a certain phase corresponding to the remaining lower arm.

7. The starting method for a permanent magnet synchronous motor according to claim 5, characterized in that, The IPM module is used to invert the bus voltage into three-phase AC power for the permanent magnet synchronous motor. When the permanent magnet synchronous motor starts, the IPM module is subjected to FOC control, and the FOC control outputs a PWM wave.

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