A control device and method for an electric motor

Abstract

The present invention discloses a control device and method for a motor. The device includes: an acquisition unit configured to acquire the operating parameters of the motor during the operating stage of the motor; a torque compensation unit configured to perform torque compensation on the motor according to the operating parameters of the motor and the set parameters of the motor during the operating stage of the motor. With this solution, by compensating the electromagnetic torque during the low-frequency startup of the motor (such as the motor of a variable-frequency air conditioner), the startup performance of the motor (such as the motor of a variable-frequency air conditioner) can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of air conditioners, and particularly relates to a control device and method for a motor (such as a motor of a variable-frequency air conditioner), and more particularly to a device, method and variable-frequency air conditioner for improving the starting performance and COP of a variable-frequency air conditioner. Background Art

[0002] The motor (such as the motor of a variable-frequency air conditioner) needs to click the start button multiple times, resulting in a long start-up response time of the motor (such as the motor of a variable-frequency air conditioner), and there is a problem of poor starting performance of the motor (such as the motor of a variable-frequency air conditioner).

[0003] The above content is only used to assist in understanding the technical solution of the present invention, and does not represent an admission that the above content is prior art. Summary of the Invention

[0004] The purpose of the present invention is to provide a control device and method for a motor to solve the problem of poor starting performance of the motor (such as the motor of a variable-frequency air conditioner), and achieve the effect of improving the starting performance of the motor (such as the motor of a variable-frequency air conditioner) by compensating the electromagnetic torque during the low-frequency start of the motor (such as the motor of a variable-frequency air conditioner).

[0005] The present invention provides a control device for a motor, including: a collection unit and a torque compensation unit; wherein, the collection unit is configured to collect the working parameters of the motor during the working stage of the motor; the torque compensation unit is configured to perform torque compensation on the motor according to the working parameters of the motor and the set parameters of the motor; wherein, the working stage of the motor includes: a starting stage in which the motor starts at a first set frequency, and / or an operating stage in which the motor operates at a second set frequency; the first set frequency is a frequency lower than the set starting frequency; the second set frequency is a frequency lower than the set operating frequency; the working parameters of the motor include: the starting parameters of the motor collected during the starting stage in which the motor starts at the first set frequency; and / or, the operating parameters of the motor collected during the operating stage in which the motor operates at the second set frequency.

[0006] In some embodiments, the torque compensation unit performs torque compensation on the motor according to the working parameters of the motor and the set parameters of the motor, including: determining the given d-axis current of the motor and the given q-axis current of the motor according to the working parameters of the motor and the set parameters of the motor; and feeding back the given d-axis current of the motor and the given q-axis current of the motor to the drive unit of the inverter of the motor to achieve torque compensation for the motor.

[0007] In some embodiments, the parameters in the starting parameters and the operating parameters of the motor include the rotational speed of the motor and the rotor magnetic flux of the motor; the rotational speed of the motor includes the electrical angular velocity; the set parameters of the motor include the torque reference value of the motor; the torque compensation unit includes a field weakening unit, a multiplication unit, a first calculation unit, and a second calculation unit; the torque compensation unit determines the given d-axis current and the given q-axis current of the motor according to the operating parameters and the set parameters of the motor, including: the field weakening unit is configured to perform field weakening processing according to the electrical angular velocity of the motor to obtain the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor; the multiplication unit is configured to determine the electromagnetic torque of the motor according to the torque reference value of the motor and the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor; the first calculation unit is configured to perform calculations according to the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor and the magnetic flux reference value of the motor to obtain the given d-axis current of the motor; the second calculation unit is configured to perform calculations according to the electromagnetic torque of the motor, the rotor magnetic flux of the motor, and the given d-axis current of the motor to obtain the given q-axis current of the motor.

[0008] In some embodiments, the first calculation unit performs calculations according to the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor and the magnetic flux reference value of the motor to obtain the given d-axis current of the motor, including: if the electrical angular velocity of the motor is less than or equal to the rated speed, then in the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor, the torque value of the motor is 1 and the given d-axis current of the motor is 0; if the electrical angular velocity of the motor is higher than the rated speed, then in the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor, the torque value of the motor is the ratio of the rated speed of the motor to the electrical angular velocity of the motor, and the given d-axis current of the motor is:

[0009]

[0010] The second calculation unit performs calculations according to the electromagnetic torque of the motor, the rotor magnetic flux of the motor, and the given d-axis current of the motor to obtain the given q-axis current of the motor, including:

[0011]

[0012] where i d * is the given d-axis current, f(ω) is the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor, L d is the d-axis inductance, Lq is the q-axis inductance, p is the number of pole pairs of the rotor poles of the motor, λ af is the rotor magnetic flux of the motor, T e * is the torque reference value of the motor, T e is the electromagnetic torque of the motor.

[0013] In some embodiments, the parameters in the starting parameters and the operating parameters of the motor further include: the phase voltage and phase current of the motor; the torque compensation unit feeds the given d-axis current and the given q-axis current of the motor back to the drive unit of the inverter of the motor to achieve torque compensation for the motor, including: determining a compensation signal of the motor according to the phase voltage of the motor, the phase current of the motor, and the given d-axis current and the given q-axis current of the motor, so as to achieve torque compensation for the motor according to the compensation signal of the motor.

[0014] Matched with the above device, on the other hand, the present invention provides an air conditioner, including: the control device of the motor described above.

[0015] In some embodiments, for the air conditioner, in the starting stage when the motor starts at the first set frequency, torque compensation is performed on the motor according to the working parameters of the motor in the starting stage and the set parameters of the motor; and / or, when the indoor temperature of the air conditioner reaches the set temperature, the air conditioner makes the motor operate at the second set frequency, and in the operating stage when the motor operates at the second set frequency, torque compensation is performed on the motor according to the working parameters of the motor in the operating stage and the set parameters of the motor.

[0016] Matched with the above air conditioner, on the other hand, the present invention provides a method for controlling a motor, including: collecting the working parameters of the motor in the working stage of the motor; performing torque compensation on the motor according to the working parameters of the motor and the set parameters of the motor in the working stage of the motor; wherein, the working stage of the motor includes: the starting stage when the motor starts at the first set frequency, and / or the operating stage when the motor operates at the second set frequency; the first set frequency is a frequency lower than the set starting frequency; the second set frequency is a frequency lower than the set operating frequency; the working parameters of the motor include: the starting parameters of the motor collected in the starting stage when the motor starts at the first set frequency; and / or, the operating parameters of the motor collected in the operating stage when the motor operates at the second set frequency.

[0017] In some embodiments, torque compensation for the motor is performed according to the operating parameters of the motor and the set parameters of the motor, including: determining the given d-axis current of the motor and the given q-axis current of the motor according to the operating parameters of the motor and the set parameters of the motor; and feeding back the given d-axis current of the motor and the given q-axis current of the motor to the drive unit of the inverter of the motor to achieve torque compensation for the motor.

[0018] In some embodiments, the parameters in the starting parameters and the operating parameters of the motor include: the rotational speed of the motor and the rotor flux linkage of the motor; the rotational speed of the motor includes: the electrical angular velocity; the set parameters of the motor include: the torque reference value of the motor; determining the given d-axis current of the motor and the given q-axis current of the motor according to the operating parameters of the motor and the set parameters of the motor includes: performing field weakening processing according to the electrical angular velocity of the motor to obtain the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor; determining the electromagnetic torque of the motor according to the torque reference value of the motor and the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor; performing calculation according to the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor and the flux linkage reference value of the motor to obtain the given d-axis current of the motor; and performing calculation according to the electromagnetic torque of the motor, the rotor flux linkage of the motor, and the given d-axis current of the motor to obtain the given q-axis current of the motor.

[0019] In some embodiments, wherein performing calculation according to the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor and the flux linkage reference value of the motor to obtain the given d-axis current of the motor includes: if the electrical angular velocity of the motor is less than or equal to the rated speed, then in the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor, the torque value of the motor is 1 and the given d-axis current of the motor is 0; if the electrical angular velocity of the motor is higher than the rated speed, then in the variation relationship of the torque value of the motor with respect to the electrical angular velocity of the motor, the torque value of the motor is the ratio of the rated speed of the motor to the electrical angular velocity of the motor, and the given d-axis current of the motor is:

[0020]

[0021] Performing calculation according to the electromagnetic torque of the motor, the rotor flux linkage of the motor, and the given d-axis current of the motor to obtain the given q-axis current of the motor includes:

[0022]

[0023] wherein, i d* is the d-axis reference current, f(ω) is the relationship between the torque value of the motor and the electrical angular velocity of the motor, L d is the d-axis inductance, L q is the q-axis inductance, p is the number of pole pairs of the rotor poles of the motor, λ af is the rotor magnetic flux of the motor, T e * is the torque reference value of the motor, T e is the electromagnetic torque of the motor.

[0024] In some embodiments, the parameters in the starting parameters and the operating parameters of the motor further include: the phase voltage and phase current of the motor; feeding the given d-axis current and the given q-axis current of the motor back to the drive unit of the inverter of the motor to achieve torque compensation for the motor, including: determining a compensation signal of the motor according to the phase voltage of the motor, the phase current of the motor, and the given d-axis current and the given q-axis current of the motor, so as to achieve torque compensation for the motor according to the compensation signal of the motor.

[0025] Thus, the solution of the present invention compensates the electromagnetic torque in the case of low-frequency starting and low-speed operation of the motor (such as the permanent magnet synchronous motor of a variable frequency air conditioner) by setting an electromagnetic torque compensation device; thereby, by compensating the electromagnetic torque during low-frequency starting of the motor (such as the motor of a variable frequency air conditioner), the starting performance of the motor (such as the motor of a variable frequency air conditioner) can be improved, and the user experience can be enhanced.

[0026] At the same time, for a variable frequency air conditioner, in the case of low-frequency starting and low-speed operation of the permanent magnet synchronous motor of the variable frequency air conditioner, by setting an electromagnetic torque compensation device, the electromagnetic torque is compensated in the case of low-frequency starting and low-speed operation of the motor (such as the permanent magnet synchronous motor of a variable frequency air conditioner); thereby, by compensating the electromagnetic torque during low-frequency starting of the motor (such as the motor of a variable frequency air conditioner), the COP of the variable frequency air conditioner system can also be improved, and the energy-saving comfort of the variable frequency air conditioner can be enhanced.

[0027] Other features and advantages of the present invention will be described in the following specification, and, in part, will be obvious from the specification, or will be understood by implementing the present invention.

[0028] Next, through the drawings and embodiments, the technical solution of the present invention will be further described in detail. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 is a schematic structural diagram of an embodiment of the control device of the motor of the present invention;

[0030] Figure 2Schematic structural diagram of an embodiment of a motor (such as the motor of a variable-frequency air conditioner) system;

[0031] Figure 3 Schematic diagram of the working process of a variable-frequency air conditioner with a torque compensation device in an embodiment;

[0032] Figure 4 Schematic structural diagram of an embodiment of a PMSM variable-frequency drive system based on torque compensation;

[0033] Figure 5 Schematic structural diagram of an embodiment of a torque compensation device;

[0034] Figure 6 Schematic diagram of the current and voltage waveforms when the motor starts;

[0035] Figure 7 Schematic diagram of the curve of the COP of a variable-frequency air conditioner system changing with frequency;

[0036] Figure 8 Schematic flow diagram of an embodiment of the control method of the motor of the present invention;

[0037] Figure 9 Schematic flow diagram of an embodiment of torque compensation for the motor in the method of the present invention;

[0038] Figure 10 Schematic flow diagram of an embodiment of determining the given d-axis current and the given q-axis current of the motor in the method of the present invention. Detailed implementation manners

[0039] To make the objectives, technical solutions and advantages of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with specific embodiments of the present invention and the corresponding drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0040] The frequency converter of a motor such as the motor of a variable-frequency air conditioner can adjust the power supply frequency within a certain range, thereby changing the speed of the compressor and achieving the purpose of controlling the refrigerant flow in the two heat exchangers (evaporator, condenser) in the air conditioner system. By controlling the output power and output frequency of the frequency converter, the starting performance of the compressor can be improved and the COP (coefficient of performance) of the variable-frequency air conditioner system can be increased, enabling the variable-frequency air conditioner to operate within a very wide frequency range.

[0041] The starting performance of variable-frequency air conditioners is poor, which will lead to poor user experience, many complaint cases and high after-sales maintenance costs.

[0042] In some solutions, when a variable-frequency air conditioner starts to work, it refrigerates at the maximum power Pf. When the indoor temperature rapidly drops to the set temperature, the compressor then remains in a continuous running state to keep the room temperature basically unchanged. At this time, the air conditioner is in a low-speed operation state. The low-frequency torque compensation device is started again, and the current and voltage of the PMSM during low-speed operation detected by the sensor are calculated, and the obtained power is fed back to the drive circuit of the PMSM to achieve torque compensation during low-frequency operation, so that the output power of the frequency converter is large, and the motor torque is larger than that without the torque compensation device, and it can limit the output power of the frequency converter stably, quickly and effectively, but it does not improve the starting performance of the system nor can it improve the COP of the system.

[0043] In other solutions, the q-axis current given value and the d-axis current reference value are set through the frequency converter; the sliding mode observer is run to estimate and track the speed of the motor rotor; the real-time value of the d-axis current of the permanent magnet synchronous motor is collected; it is judged whether the sliding mode observer converges; when the sliding mode observer converges, the speed estimation and tracking are stopped, and the speed estimation value at the moment when the speed estimation and tracking are stopped is obtained. Based on the speed estimation value at the end of the speed estimation and tracking according to the preset acceleration, the motor rotor speed is adjusted to the target speed, so that the motor has a fast starting speed, a soft start and no impact on the motor in any state, but this method cannot improve the COP of the system.

[0044] In still other solutions, the instantaneous power on the load side of the synchronous motor is introduced into the rectifier side, so that the control system has a fast response. However, both the rectifier side and the inverter side need to be controlled at the same time, the control strategy is complex, and the requirements for the main chip are high.

[0045] According to an embodiment of the present invention, a control device for a motor is provided. Refer to Figure 1 the structural schematic diagram of an embodiment of the device of the present invention shown. The control device for the motor may include: a collection unit and a torque compensation unit. The collection unit, such as a sensor. The torque compensation unit, such as a torque compensator.

[0046] Among them, the collection unit is configured to collect the working parameters of the motor during the working stage of the motor.

[0047] The torque compensation unit is configured to perform torque compensation on the motor according to the working parameters of the motor and the set parameters of the motor during the working stage of the motor, so as to improve the corresponding performance of the working stage of the motor.

[0048] Among them, the working stage of the motor includes: a starting stage in which the motor starts at a first set frequency, and / or an operating stage in which the motor operates at a second set frequency. The first set frequency is a frequency lower than the set starting frequency. The second set frequency is a frequency lower than the set operating frequency.

[0049] The operating parameters of the motor include: the starting parameters of the motor collected during the starting stage when the motor starts at a first set frequency, and / or the operating parameters of the motor collected during the operating stage when the motor operates at a second set frequency.

[0050] Specifically, the acquisition unit is configured to collect the starting parameters of the motor during the starting stage when the motor starts at a first set frequency. The torque compensation unit is configured to perform torque compensation on the motor according to the starting parameters of the motor during the starting stage when the motor starts at a first set frequency, so as to improve the starting performance of the motor.

[0051] And / or, the acquisition unit is configured to collect the operating parameters of the motor during the operating stage when the motor operates at a second set frequency. The torque compensation unit is configured to perform torque compensation on the motor according to the operating parameters of the motor during the operating stage when the motor operates at a second set frequency, so as to improve the operating performance of the motor.

[0052] In order to reduce the starting noise of a motor (such as the motor of a variable-frequency air conditioner), the motor (such as the motor of a variable-frequency air conditioner) mostly adopts low-frequency starting, and when the room temperature drops, the motor (such as the motor of a variable-frequency air conditioner) does not stop and still maintains stable and continuous low-speed operation. When a permanent magnet synchronous motor (PMSM) of a variable-frequency air conditioner operates at a low speed, its rotor magnetic flux decreases accordingly. Thus, the solution of the present invention proposes a device for improving the starting performance of a motor (such as the motor of a variable-frequency air conditioner) and the COP of a variable-frequency air conditioning system, specifically an electromagnetic torque compensation device, which can compensate the electromagnetic torque, greatly reduce the probability of starting failure, improve the starting performance of the variable-frequency air conditioner, especially improve the low-speed starting performance of the motor (such as the motor of a variable-frequency air conditioner). At the same time, when the motor operates at a low speed, it can improve the COP of the variable-frequency air conditioning system, achieve the effects of energy saving and comfort, reduce the complaint rate, and improve customer satisfaction.

[0053] In some embodiments, the torque compensation unit performs torque compensation on the motor according to the operating parameters of the motor and the set parameters of the motor during the working stage of the motor, including:

[0054] The torque compensation unit is specifically further configured to determine the given d-axis current of the motor and the given q-axis current of the motor according to the operating parameters of the motor and the set parameters of the motor.

[0055] The torque compensation unit is specifically further configured to feed back the given d-axis current of the motor and the given q-axis current of the motor to the drive unit of the inverter of the motor, so as to achieve torque compensation for the motor.

[0056] Figure 2 It is a schematic structural diagram of an embodiment of a motor (such as the motor of a variable-frequency air conditioner) system. As Figure 2 shown, in a motor (such as the motor of a variable-frequency air conditioner) system, an inverter drives a compressor, the compressor outputs high-pressure and high-temperature gas to a condenser, the condenser outputs subcooled liquid to a throttling device (such as an expansion valve), the expansion valve outputs a low-pressure gas-liquid mixture to an evaporator, and the evaporator outputs low-pressure gas to the compressor. The inverter can adjust the speed change of the compressor, thereby achieving frequency conversion.

[0057] Two modes of frequency conversion startup: low-frequency startup and other startup methods. When starting at low frequency, it is further divided into two cases: with a torque compensation device and without a torque compensation device. The working process of a variable-frequency air conditioner with a torque compensation device includes:

[0058] Step 11: When the motor (such as the motor of a variable-frequency air conditioner) starts, the torque compensation device is started synchronously. At this time, the motor has good starting performance, and there is almost no situation of starting failure. The starting performance of the motor (such as the motor of a variable-frequency air conditioner) is improved.

[0059] Step 12: When the motor (such as the motor of a variable-frequency air conditioner) starts to work, it cools at the maximum power P f When the indoor temperature quickly drops to the set temperature, the compressor then operates continuously to keep the room temperature basically unchanged. At this time, the motor (such as the motor of a variable-frequency air conditioner) is in a low-speed operation state. The low-frequency torque compensation device is started again. The current and voltage of the PMSM during low-speed operation detected by the sensor are calculated, and the obtained electromagnetic power is fed back to the drive circuit of the PMSM to achieve torque compensation during low-frequency operation, so that the inverter outputs a large power, the motor torque is larger than that without a torque compensation device, the operation is more stable, the noise is smaller, thereby improving the COP of the variable-frequency air conditioner system, making the variable-frequency air conditioner more energy-efficient, and providing a better customer experience.

[0060] Figure 3 It is a schematic diagram of the working process of a variable-frequency air conditioner with a torque compensation device. The low-frequency torque compensator can make the motor (such as the motor of a variable-frequency air conditioner) start smoothly and operate smoothly when the motor (such as the motor of a variable-frequency air conditioner) starts and operates at low frequency, improve the COP of the variable-frequency air conditioner system, and improve the comfort of people in the air-conditioned room. As Figure 3 shown, the working process of a motor (such as the motor of a variable-frequency air conditioner) with a torque compensation device includes:

[0061] Step 21: The motor (such as the motor of a variable-frequency air conditioner) starts.

[0062] Step 22: Determine whether the motor (such as the motor of a variable-frequency air conditioner) starts at a low frequency. For example, based on the starting frequency of the motor (such as the motor of a variable-frequency air conditioner), determine whether the starting frequency is within the set low-frequency starting frequency range. If so, it is determined that the motor (such as the motor of a variable-frequency air conditioner) starts at a low frequency. If the motor (such as the motor of a variable-frequency air conditioner) starts at a low frequency, then execute Step 23. If the air conditioner does not start at a low frequency, it is determined that the starting noise of the motor (such as the motor of a variable-frequency air conditioner) is large and the user's comfort is poor, and then execute Step 24.

[0063] Step 23: Determine whether the motor (such as the motor of a variable-frequency air conditioner) is equipped with a torque compensator. If the motor (such as the motor of a variable-frequency air conditioner) is equipped with a torque compensator, it is determined that the starting performance of the motor (such as the motor of a variable-frequency air conditioner) is good and the noise is low. When the temperature in the room where the motor (such as the motor of a variable-frequency air conditioner) is located reaches the set temperature, control the motor (such as the motor of a variable-frequency air conditioner) to enter the low-frequency operation mode. In the low-frequency operation mode, perform low-frequency torque compensation to improve the COP of the variable-frequency air conditioner system and make the variable-frequency air conditioner operate stably until the air conditioner shuts down.

[0064] Step 24: Determine whether the motor (such as the motor of a variable-frequency air conditioner) starts successfully. If the motor (such as the motor of a variable-frequency air conditioner) starts successfully, when the temperature in the room where the motor (such as the motor of a variable-frequency air conditioner) is located reaches the set temperature, control the motor (such as the motor of a variable-frequency air conditioner) to enter the low-frequency operation mode. In this case, the COP of the variable-frequency air conditioner system is not high. The motor (such as the motor of a variable-frequency air conditioner) operates stably in the low-frequency operation mode until the air conditioner shuts down. If the motor (such as the motor of a variable-frequency air conditioner) fails to start, return to Step 1 to restart the variable-frequency air conditioner.

[0065] Figure 4 It is a schematic structural diagram of an embodiment of a PMSM variable-frequency drive system based on torque compensation. As Figure 4 shown, the PMSM drive system based on torque compensation includes: a main circuit, a detection circuit, and a control circuit. The main circuit includes: an input module of an AC power supply, a rectifier circuit, an inverter circuit, and a PMSM. The detection circuit includes: sensors, such as a current sensor, a speed sensor, and a position sensor. The control circuit includes: a torque compensator (such as a low-frequency torque compensator), and a drive circuit of the inverter. The input module of the AC power supply is output to the PMSM after passing through the rectifier circuit and the inverter circuit. The torque compensator performs torque compensation based on the torque reference value, the flux linkage reference value, and the detection values of the sensors, and then outputs a torque compensation value to the drive circuit. The drive circuit drives the inverter circuit based on the torque compensation value.

[0066] It should be noted that the rectifier circuit (uncontrolled diode) in the frequency converter can also be replaced with a controllable module adjusted by PWM (for example: IGBT), introducing torque compensation. Although the accuracy of low-frequency control is high, it can also improve the starting performance and the COP of the variable-frequency air-conditioning system. However, the control system is very complex, the calculation speed of the chip becomes slow, and the cost becomes high, so the cost performance is not high. That is to say, the solution of the present invention is implemented on an uncontrolled diode frequency converter, with a relatively simple topological structure and the implementation effect reaching an ideal level. If it is replaced with a four-quadrant frequency converter (fully controlled type), it can also be achieved, and even the accuracy may be higher, but the control is complex and the system cost is also high.

[0067] In some embodiments, the parameters in the starting parameters and the operating parameters of the motor include: the rotational speed of the motor and the rotor magnetic flux of the motor. The rotational speed of the motor includes: the electrical angular velocity, such as the electrical angular velocity ω. The set parameters of the motor include: the torque reference value of the motor. The torque reference value of the motor, such as the given torque reference value T e * 。

[0068] The torque compensation unit includes: a field-weakening unit, a multiplication unit, a first calculation unit, and a second calculation unit.

[0069] The torque compensation unit determines the given d-axis current and the given q-axis current of the motor according to the operating parameters and the set parameters of the motor, including:

[0070] The field-weakening unit is configured to perform field-weakening processing according to the electrical angular velocity of the motor to obtain the variation relationship between the torque value of the motor and the electrical angular velocity of the motor.

[0071] The multiplication unit is configured to determine the electromagnetic torque of the motor according to the torque reference value of the motor and the variation relationship between the torque value of the motor and the electrical angular velocity of the motor, the electromagnetic torque T e 。

[0072] The first calculation unit is configured to perform calculations according to the variation relationship between the torque value of the motor and the electrical angular velocity of the motor and the magnetic flux reference value of the motor to obtain the given d-axis current of the motor, such as the d-axis reference current i d * 。

[0073] In some embodiments, the first calculation unit performs calculations according to the variation relationship between the torque value of the motor and the electrical angular velocity of the motor and the magnetic flux reference value of the motor to obtain the given d-axis current of the motor, such as the d-axis reference current i d *, including any of the following cases:

[0074] The first case: The first calculation unit is specifically further configured that if the electrical angular velocity of the motor is less than or equal to the rated speed, then in the variation relationship of the torque value of the motor with the electrical angular velocity of the motor, the torque value of the motor is 1 and the given d-axis current of the motor is 0.

[0075] The second case: The first calculation unit is specifically further configured that if the electrical angular velocity of the motor is higher than the rated speed, then in the variation relationship of the torque value of the motor with the electrical angular velocity of the motor, the torque value of the motor is the ratio of the rated speed of the motor to the electrical angular velocity of the motor, and the given d-axis current of the motor is:

[0076]

[0077] The second calculation unit is configured to perform calculations based on the electromagnetic torque of the motor, the rotor magnetic flux of the motor, and the given d-axis current of the motor to obtain the given q-axis current of the motor, such as the q-axis reference current i q * .

[0078] In some embodiments, the second calculation unit performs calculations based on the electromagnetic torque of the motor, the rotor magnetic flux of the motor, and the given d-axis current of the motor to obtain the given q-axis current of the motor, including:

[0079]

[0080] where, i d * is the given d-axis current, f(ω) is the variation relationship of the torque value of the motor with the electrical angular velocity of the motor, L d is the d-axis inductance, L q is the q-axis inductance, p is the number of pole pairs of the rotor poles of the motor, λ af is the rotor magnetic flux of the motor, T e * is the torque reference value of the motor, T e is the electromagnetic torque of the motor.

[0081] Figure 5 is a schematic structural diagram of an embodiment of the torque compensation device. Figure 5 For the output function f(ω) of the field weakening unit in n , when the actually measured electrical angular velocity ω is less than or equal to the rated speed ω d * , f(ω) = 1, and at this time i nWhen the motor operates in field-weakening mode, The d-axis reference current i d * :

[0082]

[0083] When the motor operates in field-weakening mode, the electromagnetic torque T e can be expressed as:

[0084] T e = T e * ·f(ω) (6).

[0085] The q-axis reference current i q * :

[0086]

[0087] In formulas (5), (6) and (7), p is the number of pole pairs of the PMSM rotor magnetic poles, L d is the d-axis inductance, L q is the q-axis inductance, and f(ω) is a function related to ω, which can represent the variation relationship of a torque value with ω.

[0088] Among them, regarding the field-weakening unit: The maximum voltage that the inverter can provide to the motor is limited by the DC voltage that the rectifier may output, that is, the operating speed of the motor is restricted by the inverter voltage limit. When the motor operates at the intersection point A of the constant torque operating region and the constant power operating region, the current output by the inverter may swing to the left or to the right, that is, the control system loses the control ability of the stator current. As the direct-axis component i d increases and the quadrature-axis component i q gradually decreases, the speed range of the rotor is gradually expanded. The reason for this effect is mainly that the magnetomotive force generated by the reverse direct-axis current will demagnetize the permanent magnet, weakening the direct-axis magnetic field. Therefore, this process is called field weakening. During the field-weakening process, the control of i d and i q is called field-weakening control.

[0089] When the rotor flux linkage λ af decreases at a certain moment, in a system without a torque compensator, the stator current does not change, that is, the decrease of the rotor flux linkage λ af has no effect on the stator current. However, at this time, the electromagnetic torque T e decreases accordingly, and the output of the motor also decreases accordingly, which is not desirable.

[0090] In a system with a torque compensator, when the rotor flux linkage λ afWhen it decreases at a certain moment, the calculated power decreases, and thus the electromagnetic power also decreases, resulting in a compensation signal Δi q increases, and an increased q-axis current i q appears, causing the stator current value detected by the current sensor to also increase. The electromagnetic power P obtained by calculating from formula (1) and formula (2) a increases until it equals the reference electromagnetic power P a * . During this process, the electromagnetic torque T e will have a low value at the moment when the rotor flux linkage λ af decreases, and then immediately rises to match the reference value T e * . Thus, it can be known that the added power-torque compensator can compensate the electromagnetic torque T af when the rotor flux linkage λ e decreases, enabling the motor to operate stably. When the motor (such as the motor of a variable-frequency air conditioner) starts at low frequency, adding a torque compensator can improve the starting performance. When the motor (such as the motor of a variable-frequency air conditioner) operates at low speed, the COP of the variable-frequency air conditioner system can be increased by about 5.7%. It should be noted that the torque compensation device provided by the solution of the present invention can be applied in the air-conditioning field, and even in other fields that require low-speed operation of variable-frequency motors, such as the heat pump field, etc.

[0091] In some embodiments, the parameters in the starting parameters and the operating parameters of the motor further include: the phase voltage and phase current of the motor.

[0092] The torque compensation unit feeds the given d-axis current and the given q-axis current of the motor back to the drive unit of the inverter of the motor to achieve torque compensation for the motor, including: the torque compensation unit is specifically further configured to determine the compensation signal of the motor according to the phase voltage of the motor, the phase current of the motor, and the given d-axis current and the given q-axis current of the motor, so as to achieve torque compensation for the motor according to the compensation signal of the motor.

[0093] Specifically, by detecting the current and voltage of the PMSM during low-speed operation, the electromagnetic power of the motor is calculated according to the current and voltage of the PMSM during low-speed operation. The calculated electromagnetic power is fed back to the drive circuit of the PMSM to achieve torque compensation during low-frequency operation of the motor, improving the low-frequency starting performance of the motor (such as the motor of a variable-frequency air conditioner) and the COP of the variable-frequency air conditioner system by about 5.7%, making the air conditioner more energy-efficient and the customer more comfortable. Detecting the current and voltage of the PMSM during low-speed operation includes: determining the current of the PMSM during low-speed operation according to the rotational speed, torque reference value, and flux linkage reference value of the motor, and obtaining the voltage of the PMSM during low-speed operation to achieve the detection of the current and voltage of the PMSM during low-speed operation.

[0094] As Figure 5 shown, a torque compensation device, such as a torque compensator, calculates the current and voltage of a PMSM during low-speed operation detected by a sensor, and feeds back the obtained inverter output power (i.e., electromagnetic power) to the drive circuit of the PMSM to achieve torque compensation during low-frequency operation.

[0095] The working process of the torque compensation device will be exemplarily described below.

[0096] When the motor (such as the motor of a variable-frequency air conditioner) starts and operates at low frequency, the magnetic flux of the motor in the compressor decreases, and power needs to be added to compensate for the electromagnetic torque. The input power P of the motor f :

[0097]

[0098] In formula (1), v a , v b , v c are the three-phase voltages of the motor in the abc coordinate system, and i a , i b , i c are the three-phase currents of the motor in the abc coordinate system. v d , v q are the two-phase voltages of the motor in the dq coordinate system, and i d , i q are the two-phase currents of the motor in the dq coordinate system.

[0099] The electromagnetic power P a can be obtained by subtracting the stator winding loss from the input power P of the motor, so: f

[0100]

[0101] In formula (2), R s is the resistance value of the stator winding of the motor.

[0102] The reference value P a * of the electromagnetic power is obtained by multiplying the mechanical angular velocity ω m and the reference value T e * of the torque, that is:

[0103] P a * = ω m · T e * (3).

[0104] In formula (3), ωm is the mechanical angular velocity obtained by dividing the electrical angular velocity detected by the position sensor by the number of pole pairs p of the motor, T e * is the given torque reference value.

[0105] The compensation signal Δi q can be obtained by the following formula:

[0106] Δi q = K p (P a * - P a ) + K i ∫(P a * - P a ) (4).

[0107] In formula (4), K p and K i are the proportional gain and integral gain of the PI controller respectively.

[0108] Among them, according to the calculation of formula (4), the obtained is the compensation signal, and this compensation signal has a relationship with the reference electromagnetic power P a *. Combining formula (6) and formula (3), the reference electromagnetic torque T e * in the torque compensation device is obtained from P a *. That is, formula (4) and formula (6) are related through P a *. Thus, a close relationship can be established between the compensation signal and the torque compensation device through the substitution method.

[0109] Figure 6 is a schematic diagram of the current and voltage waveforms when the motor starts. Figure 6 In it, from top to bottom, the first waveform (such as the waveform in the first row) is the stator current when the motor starts. The second waveform (such as the waveform in the second row) is the given q-axis current, and the third waveform (such as the waveforms on both sides of the second row and in the middle of the third row) is the compensation current Δi q . The fourth waveform (such as the waveform in the fourth row) is the current i q * . The first vertical ellipse frame (such as the first vertical ellipse frame) indicates that the torque compensation device is turned on at this moment, and the second vertical ellipse frame (such as the second vertical ellipse frame) indicates that the torque compensation device is turned off at this moment. It can be seen that the amplitude fluctuation of the current i q * after adding the torque compensation device is smaller, so the accuracy of calculating the output power of the frequency converter is higher.

[0110] Figure 7 is a schematic diagram of the COP of the variable-frequency air conditioner changing with frequency. From Figure 7As can be seen, when the indoor temperature is constant, the motor (such as the motor of a variable-frequency air conditioner) operates continuously and stably at a low frequency. Adding a torque compensation device can increase the COP by about 5.7% compared to not adding a torque compensation device, proving that the torque compensation device is effective.

[0111] Through a large number of experimental verifications, adopting the technical solution of the present invention, by setting an electromagnetic torque compensation device, when the motor (such as the permanent magnet synchronous motor of a variable-frequency air conditioner) operates at a low speed, the electromagnetic torque is compensated. Thus, by compensating the electromagnetic torque when the motor (such as the motor of a variable-frequency air conditioner) starts at a low frequency, the starting performance of the motor (such as the motor of a variable-frequency air conditioner) can be improved, and the user experience can be enhanced. At the same time, when the motor (such as the permanent magnet synchronous motor of a variable-frequency air conditioner) operates at a low speed, the COP of the system where the variable-frequency air conditioner is located is increased, and the energy-saving comfort of the variable-frequency air conditioner is improved.

[0112] According to an embodiment of the present invention, there is also provided an air conditioner corresponding to a control device of a motor. The air conditioner may include: the control device of the motor described above.

[0113] In some embodiments, during the starting stage when the motor of the air conditioner starts at a first set frequency, according to the working parameters of the motor during the starting stage and the set parameters of the motor, torque compensation is performed on the motor to improve the starting performance of the motor; and / or, when the indoor temperature of the air conditioner reaches the set temperature, the motor operates at a second set frequency, and during the operating stage when the motor operates at the second set frequency, according to the working parameters of the motor during the operating stage and the set parameters of the motor, torque compensation is performed on the motor to improve the COP of the air conditioner during the operating stage.

[0114] Since the processing and functions implemented by the air conditioner in this embodiment are basically corresponding to the embodiments, principles, and examples of the foregoing device, for the details not described in the description of this embodiment, reference may be made to the relevant descriptions in the foregoing embodiments, and details will not be repeated here.

[0115] Through a large number of experimental verifications, adopting the technical solution of the present invention, by setting an electromagnetic torque compensation device, when the motor (such as the permanent magnet synchronous motor of a variable-frequency air conditioner) operates at a low speed, the electromagnetic torque is compensated, which can significantly reduce the probability of starting failure and improve the starting performance of the variable-frequency air conditioner.

[0116] According to an embodiment of the present invention, there is also provided a control method for a motor corresponding to an air conditioner, as Figure 8 shown in the flowchart of an embodiment of the method of the present invention. The control method for the motor may include: step S110 and step S120.

[0117] At step S110, during the operating phase of the motor, operating parameters of the motor are collected.

[0118] At step S120, during the operating phase of the motor, torque compensation is performed on the motor according to the operating parameters of the motor and the set parameters of the motor, so as to improve the corresponding performance of the operating phase of the motor.

[0119] Among them, the operating phase of the motor includes: a starting phase in which the motor starts at a first set frequency, and / or an operating phase in which the motor operates at a second set frequency. The first set frequency is a frequency lower than the set starting frequency. The second set frequency is a frequency lower than the set operating frequency.

[0120] The operating parameters of the motor include: starting parameters of the motor collected during the starting phase in which the motor starts at the first set frequency. And / or, operating parameters of the motor collected during the operating phase in which the motor operates at the second set frequency.

[0121] Specifically, the acquisition unit is configured to collect the starting parameters of the motor during the starting phase in which the motor starts at the first set frequency. The torque compensation unit is configured to perform torque compensation on the motor according to the starting parameters of the motor during the starting phase in which the motor starts at the first set frequency, so as to improve the starting performance of the motor.

[0122] And / or, the acquisition unit is configured to collect the operating parameters of the motor during the operating phase in which the motor operates at the second set frequency. The torque compensation unit is configured to perform torque compensation on the motor according to the operating parameters of the motor during the operating phase in which the motor operates at the second set frequency, so as to improve the operating performance of the motor.

[0123] In order to reduce the starting noise of a motor (such as the motor of a variable-frequency air conditioner), the motor (such as the motor of a variable-frequency air conditioner) mostly uses low-frequency starting, and when the room temperature drops, the motor (such as the motor of a variable-frequency air conditioner) does not stop running and still maintains stable and continuous low-speed operation. When a permanent magnet synchronous motor (PMSM) of a motor such as a variable-frequency air conditioner operates at a low speed, its rotor magnetic flux decreases accordingly. Thus, the solution of the present invention proposes a device for improving the starting performance of a motor (such as the motor of a variable-frequency air conditioner) and the COP of a variable-frequency air-conditioning system, specifically an electromagnetic torque compensation device, which can compensate electromagnetic torque, greatly reduce the probability of starting failure, improve the starting performance of a variable-frequency air conditioner, especially improve the low-speed starting performance of a motor (such as the motor of a variable-frequency air conditioner). At the same time, when the motor operates at a low speed, the COP of the variable-frequency air-conditioning system is improved, which can achieve the effects of energy saving and comfort, reduce the complaint rate, and improve customer satisfaction.

[0124] In some embodiments, during the working stage of the motor in step S120, the specific process of torque compensation for the motor according to the working parameters of the motor and the set parameters of the motor is as follows in the following exemplary description.

[0125] The following combines Figure 9 The schematic flowchart of an embodiment of the method for torque compensation for the motor in the present invention shown in the figure further illustrates the specific process of torque compensation for the motor in step S120, including: step S210 and step S220.

[0126] Step S210, determine the given d-axis current of the motor and the given q-axis current of the motor according to the working parameters of the motor and the set parameters of the motor.

[0127] Step S220, feedback the given d-axis current of the motor and the given q-axis current of the motor to the drive unit of the inverter of the motor to achieve torque compensation for the motor.

[0128] Figure 2 It is a schematic structural diagram of an embodiment of a motor (such as a motor of a variable-frequency air conditioner) system. As Figure 2 shown, in a motor (such as a motor of a variable-frequency air conditioner) system, an inverter drives a compressor, the compressor outputs high-pressure and high-temperature gas to a condenser, the condenser outputs subcooled liquid to a throttling device (such as an expansion valve), the expansion valve outputs a low-pressure gas-liquid mixture to an evaporator, and the evaporator outputs low-pressure gas to the compressor. The inverter can adjust the speed change of the compressor to achieve frequency conversion.

[0129] Two modes of frequency conversion startup: low-frequency startup and other startup methods. When starting at low frequency, it is divided into two cases: with a torque compensation device and without a torque compensation device. The working process of a variable-frequency air conditioner with a torque compensation device includes:

[0130] Step 11, when the motor (such as a motor of a variable-frequency air conditioner) starts, synchronously start the torque compensation device. At this time, the starting performance of the motor is good, and there is almost no situation of starting failure. The starting performance of the motor (such as a motor of a variable-frequency air conditioner) is improved.

[0131] Step 12, when the motor (such as a motor of a variable-frequency air conditioner) starts to work, with the maximum power P fRefrigeration: When the indoor temperature rapidly drops to the set temperature, the compressor then remains in a continuous running state to keep the room temperature basically unchanged. At this time, the motor (such as the motor of a variable-frequency air conditioner) operates at a low speed. The low-frequency torque compensation device is started again to calculate the current and voltage of the PMSM during low-speed operation detected by the sensor, and the obtained electromagnetic power is fed back to the drive circuit of the PMSM to achieve torque compensation during low-frequency operation, so that the output power of the frequency converter is large, the motor torque is larger than that without the torque compensation device, the operation is more stable, the noise is smaller, thereby improving the COP of the variable-frequency air conditioner system, making the variable-frequency air conditioner more energy-efficient and providing a better customer experience.

[0132] Figure 3 It is a schematic diagram of the working process of a variable-frequency air conditioner with a torque compensation device. The low-frequency torque compensator can make the motor (such as the motor of a variable-frequency air conditioner) start smoothly and operate smoothly when the motor (such as the motor of a variable-frequency air conditioner) starts and operates at low frequency, improve the COP of the variable-frequency air conditioner system, and improve the comfort of people in the air-conditioned room. As Figure 3 shown, the working process of the motor (such as the motor of a variable-frequency air conditioner) with a torque compensation device includes:

[0133] Step 21: The motor (such as the motor of a variable-frequency air conditioner) starts.

[0134] Step 22: Determine whether the motor (such as the motor of a variable-frequency air conditioner) starts at low frequency. For example, according to the starting frequency of the motor (such as the motor of a variable-frequency air conditioner), determine whether the starting frequency is within the set low-frequency starting frequency range. If so, it is determined that the motor (such as the motor of a variable-frequency air conditioner) starts at low frequency. If the motor (such as the motor of a variable-frequency air conditioner) starts at low frequency, then execute Step 23. If the air conditioner does not start at low frequency, it is determined that the starting noise of the motor (such as the motor of a variable-frequency air conditioner) is large and the comfort of the user is poor, and then execute Step 24.

[0135] Step 23: Determine whether the motor (such as the motor of a variable-frequency air conditioner) is equipped with a torque compensator. If the motor (such as the motor of a variable-frequency air conditioner) is equipped with a torque compensator, it is determined that the starting performance of the motor (such as the motor of a variable-frequency air conditioner) is good and the noise is low. When the temperature in the room where the motor (such as the motor of a variable-frequency air conditioner) is located reaches the set temperature, control the motor (such as the motor of a variable-frequency air conditioner) to enter the low-frequency operation mode. In the low-frequency operation mode, perform low-frequency torque compensation to improve the COP of the variable-frequency air conditioner system, make the variable-frequency air conditioner operate stably until the air conditioner shuts down.

[0136] Step 24: Determine whether the motor (such as the motor of a variable-frequency air conditioner) starts successfully. If the motor (such as the motor of a variable-frequency air conditioner) starts successfully, when the temperature in the room where the motor (such as the motor of a variable-frequency air conditioner) is located reaches the set temperature, control the motor (such as the motor of a variable-frequency air conditioner) to enter the low-frequency operation mode. In this case, the COP of the variable-frequency air conditioner system is not high. The motor (such as the motor of a variable-frequency air conditioner) operates stably in the low-frequency operation mode until the air conditioner shuts down. If the motor (such as the motor of a variable-frequency air conditioner) fails to start, return to Step 1 and restart the variable-frequency air conditioner again.

[0137] Figure 4 FIG. is a schematic structural diagram of an embodiment of a PMSM variable-frequency drive system based on torque compensation. As Figure 4 shown, the PMSM drive system based on torque compensation includes: a main circuit, a detection circuit, and a control circuit. The main circuit includes: an input module of an AC power supply, a rectifier circuit, an inverter circuit, and a PMSM. The detection circuit includes: sensors, such as a current sensor, a speed sensor, and a position sensor. The control circuit includes: a torque compensator (such as a low-frequency torque compensator), and a drive circuit of the inverter. The input module of the AC power supply is output to the PMSM after passing through the rectifier circuit and the inverter circuit. The torque compensator performs torque compensation according to the torque reference value, the flux linkage reference value, and the detection values of the sensors, and then outputs a torque compensation value to the drive circuit. The drive circuit drives the inverter circuit based on the torque compensation value.

[0138] In some embodiments, the parameters in the start parameters and the operation parameters of the motor include: the speed of the motor and the rotor flux linkage of the motor. The speed of the motor includes: the electrical angular velocity, such as the electrical angular velocity ω. The set parameters of the motor include: the torque reference value of the motor. The torque reference value of the motor, such as the given torque reference value T e * 。

[0139] For the specific process of determining the given d-axis current and the given q-axis current of the motor according to the working parameters and the set parameters of the motor in Step S210, refer to the following exemplary description.

[0140] The following combines Figure 10 FIG. shows a schematic flowchart of an embodiment for determining the given d-axis current and the given q-axis current of the motor in the method of the present invention, and further illustrates the specific process of determining the given d-axis current and the given q-axis current of the motor in Step S210, including: Step S310 to Step S340.

[0141] Step S310: Perform field weakening processing according to the electrical angular velocity of the motor to obtain the variation relationship between the torque value of the motor and the electrical angular velocity of the motor.

[0142] Step S320: Determine the electromagnetic torque T of the motor according to the torque reference value of the motor and the variation relationship between the torque value of the motor and the electrical angular velocity of the motor. e 。

[0143] Step S330: Calculate according to the variation relationship between the torque value of the motor and the electrical angular velocity of the motor and the magnetic flux reference value of the motor to obtain the d-axis reference current i of the motor, such as the d-axis reference current. d * 。

[0144] In some embodiments, in step S330, calculate according to the variation relationship between the torque value of the motor and the electrical angular velocity of the motor and the magnetic flux reference value of the motor to obtain the d-axis reference current i of the motor, such as the d-axis reference current. d * includes any of the following situations:

[0145] The first situation: If the electrical angular velocity of the motor is less than or equal to the rated speed, then in the variation relationship between the torque value of the motor and the electrical angular velocity of the motor, the torque value of the motor is 1 and the d-axis reference current of the motor is 0.

[0146] The second situation: If the electrical angular velocity of the motor is higher than the rated speed, then in the variation relationship between the torque value of the motor and the electrical angular velocity of the motor, the torque value of the motor is the ratio of the rated speed of the motor to the electrical angular velocity of the motor, and the d-axis reference current of the motor is:

[0147]

[0148] Step S340: Calculate according to the electromagnetic torque of the motor, the rotor magnetic flux of the motor, and the d-axis reference current of the motor to obtain the q-axis reference current i of the motor, such as the q-axis reference current. q * 。

[0149] In some embodiments, in step S340, calculate according to the electromagnetic torque of the motor, the rotor magnetic flux of the motor, and the d-axis reference current of the motor to obtain the q-axis reference current of the motor, including:

[0150]

[0151] Wherein, i d * is the d-axis reference current, f(ω) is the variation relationship between the torque value of the motor and the electrical angular velocity of the motor, Ld is the d-axis inductance, L q is the q-axis inductance, p is the number of pole pairs of the rotor poles of the motor, λ af is the rotor magnetic flux of the motor, T e * is the torque reference value of the motor, T e is the electromagnetic torque of the motor.

[0152] Figure 5 is a schematic structural diagram of an embodiment of the torque compensation device. Figure 5 The output function f(ω) of the field weakening unit in, when the actually measured electrical angular velocity ω is less than or equal to the rated speed ω n , f(ω) = 1, at this time i d * = 0. When the electrical angular velocity ω is higher than the rated speed ω n , the motor operates in field weakening, The d-axis reference current i d * :

[0153]

[0154] When the motor operates in field weakening, the electromagnetic torque T e can be expressed as:

[0155] T e = T e * ·f(ω) (6).

[0156] The q-axis reference current i q * :

[0157]

[0158] In formulas (5), (6) and (7), p is the number of pole pairs of the PMSM rotor poles, L d is the d-axis inductance, L q is the q-axis inductance, f(ω) is a function related to ω, and can represent the variation relationship of a torque value with ω.

[0159] When the rotor magnetic flux λ af decreases at a certain moment, in a system without a torque compensator, the stator current does not change, that is, the decrease of the rotor magnetic flux λ af has no influence on the stator current. But at this time the electromagnetic torque T e correspondingly decreases, and the output of the motor also decreases accordingly, which is not desirable.

[0160] In a system with a torque compensator, when the rotor magnetic flux λ afWhen it decreases at a certain moment, the calculated power decreases, so the electromagnetic power also decreases, resulting in a compensation signal Δi q increases, and the q-axis current i q increases, causing the stator current value detected by the current sensor to also increase. The electromagnetic power P a calculated from formulas (1) and (2) increases until it equals the reference electromagnetic power P a * . During this process, the electromagnetic torque T e will have a low value at the moment when the rotor magnetic flux λ af decreases, and then immediately rises to match the reference value T e * . Thus, it can be known that the added power-torque compensator can compensate the electromagnetic torque T af when the rotor magnetic flux λ e decreases, enabling the motor to operate stably. When the motor (such as the motor of a variable-frequency air conditioner) starts at low frequency, adding a torque compensator can improve the starting performance. When the motor (such as the motor of a variable-frequency air conditioner) operates at low speed, the COP of the variable-frequency air conditioner system can be increased by about 5.7%. It should be noted that the torque compensation device provided by the solution of the present invention can be applied in the air-conditioning field and even other fields that require low-speed operation of variable-frequency motors, such as the heat pump field, etc.

[0161] In some embodiments, the parameters in the starting parameters and the operating parameters of the motor further include: the phase voltage and phase current of the motor.

[0162] In step S220, feeding the given d-axis current and the given q-axis current of the motor back to the drive unit of the inverter of the motor to achieve torque compensation for the motor includes: determining the compensation signal of the motor according to the phase voltage of the motor, the phase current of the motor, and the given d-axis current and the given q-axis current of the motor, so as to achieve torque compensation for the motor according to the compensation signal of the motor.

[0163] Specifically, by detecting the current and voltage of the PMSM during low-speed operation, the electromagnetic power of the motor is calculated according to the current and voltage of the PMSM during low-speed operation. The calculated electromagnetic power is fed back to the drive circuit of the PMSM to achieve torque compensation during low-frequency operation of the motor, improving the low-frequency starting performance of the motor (such as the motor of a variable-frequency air conditioner) and the COP of the variable-frequency air conditioner system by about 5.7%, making the air conditioner more energy-efficient and the customer more comfortable. Detecting the current and voltage of the PMSM during low-speed operation includes: determining the current of the PMSM during low-speed operation according to the rotational speed, torque reference value, and magnetic flux reference value of the motor, and obtaining the voltage of the PMSM during low-speed operation to achieve detection of the current and voltage of the PMSM during low-speed operation.

[0164] As Figure 5 shown, a torque compensation device, such as a torque compensator, calculates the current and voltage of a PMSM during low-speed operation detected by a sensor, and feeds back the obtained inverter output power (i.e., electromagnetic power) to the drive circuit of the PMSM to achieve torque compensation during low-frequency operation.

[0165] The working process of the torque compensation device will be exemplarily described below.

[0166] When the motor (such as the motor of a variable-frequency air conditioner) starts and operates at low frequency, the magnetic flux of the motor in the compressor decreases, and power needs to be added to compensate for the electromagnetic torque. The input power P of the motor f :

[0167]

[0168] In formula (1), v a , v b , v c are the three-phase voltages of the motor in the abc coordinate system, and i a , i b , i c are the three-phase currents of the motor in the abc coordinate system. v d , v q are the two-phase voltages of the motor in the dq coordinate system, and i d , i q are the two-phase currents of the motor in the dq coordinate system.

[0169] The electromagnetic power P a can be obtained by subtracting the stator winding loss from the input power P of the motor. Therefore: f (2).

[0170]

[0171] In formula (2), R s is the stator winding resistance value of the motor.

[0172] The reference value P of the electromagnetic power a * is obtained by multiplying the mechanical angular velocity ω m and the reference value T of the torque e * , that is:

[0173] P a * = ω m ·T e * (3).

[0174] In formula (3), ω mis the mechanical angular velocity obtained by dividing the electrical angular velocity detected by the position sensor by the number of pole pairs p of the motor, T e * is the given torque reference value.

[0175] The compensation signal Δi q can be obtained by the following formula:

[0176] Δi q = K p (P a * - P a ) + K i ∫(P a * - P a ) (4).

[0177] In formula (4), K p , K i are the proportional gain and integral gain of the PI controller respectively.

[0178] Figure 6 is a schematic diagram of the current and voltage waveforms when the motor starts. Figure 6 In, from top to bottom, the first waveform (such as the waveform in the first row) is the stator current when the motor starts. The second waveform (such as the waveform in the second row) is the given q-axis current, and the third waveform (such as the waveforms on both sides of the second row and in the middle of the third row) is the compensation current Δi q . The fourth waveform (such as the waveform in the fourth row) is the current i q * . The first vertical ellipse frame (such as the first vertical ellipse frame) indicates that the torque compensation device is turned on at this moment, and the second vertical ellipse frame (such as the second vertical ellipse frame) indicates that the torque compensation device is turned off at this moment. It can be seen that the amplitude fluctuation of the current i q * is smaller after adding the torque compensation device, so the accuracy of calculating the output power of the frequency converter is higher.

[0179] Figure 7 is a schematic diagram of the curve of the COP of the variable-frequency air conditioner changing with frequency. From Figure 7 it can be seen that when the indoor temperature is constant, the motor (such as the motor of the variable-frequency air conditioner) runs stably at low frequency. After adding the torque compensation device, the COP is increased by about 5.7% compared with not adding the torque compensation device, which proves that the torque compensation device is effective.

[0180] Since the processing and functions implemented by the method of this embodiment are basically corresponding to the embodiments, principles and examples of the aforementioned air conditioner, for the details not described in the description of this embodiment, reference can be made to the relevant descriptions in the aforementioned embodiments and will not be elaborated here.

[0181] Verified by a large number of tests, by adopting the technical solution of this embodiment and setting an electromagnetic torque compensation device, when the motor (such as the permanent magnet synchronous motor of a variable frequency air conditioner) runs at a low speed, the electromagnetic torque can be compensated, the COP of the variable frequency air conditioner system can be improved when the motor runs at a low speed, and the effects of energy saving and comfort can be achieved.

[0182] In summary, it is easy for those skilled in the art to understand that on the premise of no conflict, the above-mentioned advantageous methods can be freely combined and superimposed.

[0183] The above are only the embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the scope of the claims of the present invention.

Claims

1. A control device for an electric motor, characterized in that, Including: A collection unit and a torque compensation unit; wherein, The collection unit is configured to collect the operating parameters of the motor during the operating stage of the motor; The torque compensation unit is configured to perform torque compensation on the motor according to the operating parameters of the motor and the set parameters of the motor during the operating stage of the motor; Wherein, the operating stage of the motor includes: a starting stage in which the motor starts at a first set frequency, and an operating stage in which the motor operates at a second set frequency; the first set frequency is a frequency lower than the set starting frequency; the second set frequency is a frequency lower than the set operating frequency; The operating parameters of the motor include: starting parameters of the motor collected during the starting stage in which the motor starts at the first set frequency; operating parameters of the motor collected during the operating stage in which the motor operates at the second set frequency; When the motor starts, the torque compensation unit is started synchronously, and at this time, the motor has good starting performance; when the motor starts to work, with the maximum power P f for refrigeration. When the indoor temperature rapidly drops to the set temperature, the compressor then operates continuously to keep the room temperature basically unchanged. At this time, the motor is in a low-speed operation state, and the torque compensation unit is started again.

2. The control device of the motor according to claim 1, characterized in that, The torque compensation unit performs torque compensation on the motor according to the operating parameters of the motor and the set parameters of the motor, including: Determining a given d-axis current of the motor and a given q-axis current of the motor according to the operating parameters of the motor and the set parameters of the motor; Feeding back the given d-axis current of the motor and the given q-axis current of the motor to the drive unit of the inverter of the motor to achieve torque compensation for the motor.

3. The control device of the motor according to claim 2, characterized in that, The parameters in the starting parameters of the motor and the operating parameters of the motor include: the speed of the motor and the rotor flux linkage of the motor; the speed of the motor includes: electrical angular velocity; the set parameters of the motor include: the torque reference value of the motor; The torque compensation unit includes: a field weakening unit, a multiplication unit, a first calculation unit and a second calculation unit; The torque compensation unit determines the given d-axis current of the motor and the given q-axis current of the motor according to the operating parameters of the motor and the set parameters of the motor, including: The field weakening unit is configured to perform field weakening processing according to the electrical angular velocity of the motor to obtain the variation relationship of the torque value of the motor with the electrical angular velocity of the motor; The multiplication unit is configured to determine the electromagnetic torque of the motor according to the torque reference value of the motor and the variation relationship of the torque value of the motor with the electrical angular velocity of the motor; The first calculation unit is configured to perform calculations according to the variation relationship of the torque value of the motor with the electrical angular velocity of the motor and the flux linkage reference value of the motor to obtain the given d-axis current of the motor; The second calculation unit is configured to perform calculations according to the electromagnetic torque of the motor, the rotor flux linkage of the motor, and the given d-axis current of the motor to obtain the given q-axis current of the motor.

4. The control device of the motor according to claim 3, characterized in that Wherein, The first calculation unit performs calculations according to the variation relationship of the torque value of the motor with the electrical angular velocity of the motor and the flux linkage reference value of the motor to obtain the given d-axis current of the motor, including: If the electrical angular velocity of the motor is less than or equal to the rated speed, in the relationship between the torque value of the motor and the electrical angular velocity of the motor, the torque value of the motor is 1, and the given d-axis current of the motor is 0; If the electrical angular velocity of the motor is higher than the rated speed, in the relationship between the torque value of the motor and the electrical angular velocity of the motor, the torque value of the motor is the ratio of the rated speed of the motor to the electrical angular velocity of the motor, and the given d-axis current of the motor is: The second calculation unit calculates the given q-axis current of the motor according to the electromagnetic torque of the motor, the rotor flux linkage of the motor, and the given d-axis current of the motor, including: where i d * is the d-axis given current, f(ω) is the relationship between the torque value of the motor and the electrical angular velocity of the motor, L d is the d-axis inductance, L q is the q-axis inductance, p is the number of pole pairs of the rotor poles of the motor, λ af is the rotor flux linkage of the motor, T e * is the torque reference value of the motor, T e is the electromagnetic torque of the motor.

5. The control device for an electric machine according to any one of claims 2 to 4, characterized in that The parameters in the starting parameters and operating parameters of the motor further include: the phase voltage and phase current of the motor; The torque compensation unit feeds back the given d-axis current and the given q-axis current of the motor to the drive unit of the inverter of the motor to achieve torque compensation for the motor, including: Determining a compensation signal of the motor according to the phase voltage of the motor, the phase current of the motor, the given d-axis current of the motor, and the given q-axis current of the motor, so as to achieve torque compensation for the motor according to the compensation signal of the motor.

6. A control method for a motor, characterized in that, Including: During the working stage of the motor, collect the working parameters of the motor; During the working stage of the motor, perform torque compensation on the motor according to the working parameters of the motor and the set parameters of the motor; Wherein, the working stage of the motor includes: a starting stage in which the motor starts at a first set frequency, and an operating stage in which the motor operates at a second set frequency; the first set frequency is a frequency lower than the set starting frequency; the second set frequency is a frequency lower than the set operating frequency; The working parameters of the motor include: the starting parameters of the motor collected during the starting stage in which the motor starts at the first set frequency; the operating parameters of the motor collected during the operating stage in which the motor operates at the second set frequency; When the motor starts, the torque compensation unit is started synchronously, and at this time, the motor has good starting performance; when the motor starts to work, with the maximum power P f Refrigerate. When the indoor temperature quickly drops to the set temperature, the compressor then runs continuously to keep the room temperature basically unchanged. At this time, the motor is in a low-speed operation state, and the torque compensation unit is started again.

7. The control method of the motor according to claim 6, wherein, Performing torque compensation on the motor according to the working parameters of the motor and the set parameters of the motor includes: Determining the given d-axis current and the given q-axis current of the motor according to the working parameters of the motor and the set parameters of the motor; Feeding back the given d-axis current and the given q-axis current of the motor to the drive unit of the inverter of the motor to achieve torque compensation for the motor.

8. The control method of the motor according to claim 7, characterized in that, The parameters in the starting parameters and operating parameters of the motor include: the speed of the motor and the rotor flux linkage of the motor; the speed of the motor includes: electrical angular velocity; the set parameters of the motor include: the torque reference value of the motor; Determining the given d-axis current and the given q-axis current of the motor according to the working parameters of the motor and the set parameters of the motor includes: Performing field weakening processing according to the electrical angular velocity of the motor to obtain the relationship between the torque value of the motor and the electrical angular velocity of the motor; Determine the electromagnetic torque of the motor according to the torque reference value of the motor and the variation relationship of the torque value of the motor with the electrical angular velocity of the motor; Perform calculations based on the variation relationship of the torque value of the motor with the electrical angular velocity of the motor and the flux linkage reference value of the motor to obtain the d-axis reference current of the motor; Perform calculations based on the electromagnetic torque of the motor, the rotor flux linkage of the motor, and the d-axis reference current of the motor to obtain the q-axis reference current of the motor.

9. The control method of the motor according to claim 8, characterized in that, Wherein, Performing calculations based on the variation relationship of the torque value of the motor with the electrical angular velocity of the motor and the flux linkage reference value of the motor to obtain the d-axis reference current of the motor includes: If the electrical angular velocity of the motor is less than or equal to the rated speed, then in the variation relationship of the torque value of the motor with the electrical angular velocity of the motor, the torque value of the motor is 1 and the d-axis reference current of the motor is 0; If the electrical angular velocity of the motor is higher than the rated speed, then in the variation relationship of the torque value of the motor with the electrical angular velocity of the motor, the torque value of the motor is the ratio of the rated speed of the motor to the electrical angular velocity of the motor, and the d-axis reference current of the motor is: Performing calculations based on the electromagnetic torque of the motor, the rotor flux linkage of the motor, and the d-axis reference current of the motor to obtain the q-axis reference current of the motor includes: where i d * is the d-axis reference current, f(ω) is the relationship between the torque value of the motor and the electrical angular velocity of the motor, L d is the d-axis inductance, L q is the q-axis inductance, p is the number of pole pairs of the rotor poles of the motor, λ af is the rotor flux linkage of the motor, T e * is the torque reference value of the motor, T e is the electromagnetic torque of the motor.

10. The control method of the motor according to any one of claims 7 to 9, characterized in that, The parameters in the starting parameters and operating parameters of the motor further include: the phase voltage and phase current of the motor; Feed the reference d-axis current and the reference q-axis current of the motor back to the drive unit of the inverter of the motor to achieve torque compensation for the motor, including: Determine the compensation signal of the motor according to the phase voltage of the motor, the phase current of the motor, and the reference d-axis current and the reference q-axis current of the motor, so as to achieve torque compensation for the motor according to the compensation signal of the motor.

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