Household appliance and control method thereof

Abstract

The invention provides a household appliance and a control method thereof.The household appliance comprises a shell, a permanent magnet synchronous motor and a controller, and the permanent magnet synchronous motor is arranged in the shell and used for operating according to direct-current input voltage; the controller is configured to determine that the permanent magnet synchronous motor is in a field weakening control stage, and obtain the rotating speed of the permanent magnet synchronous motor every preset sampling time; and determining whether to limit a flux weakening current value output by the flux weakening control at the current sampling moment or not according to the corresponding rotating speeds of the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, so as to adjust the flux weakening depth of the permanent magnet synchronous motor. Therefore, when the output torque of the permanent magnet synchronous motor is reduced to be equal to the load torque, the weak magnetic current is limited to be continuously reduced, the rotating speed of the permanent magnet synchronous motor is prevented from being reduced due to continuous reduction of the output torque, and the rotating speed of the permanent magnet synchronous motor is kept at the maximum rotating speed value.

Description

Technical Field

[0001] The present invention relates to the technical field of household electrical appliances, and in particular to a household electrical appliance and a control method thereof. Background Art

[0002] In household appliances, the speed of permanent magnet synchronous motors needs to run at high speed, for example, reaching more than 16000rpm to meet the operation requirements of household appliances. Under normal bus voltage, when the speed of permanent magnet synchronous motors runs at high speed, the voltage requirement of permanent magnet synchronous motors cannot be met, so weak magnetic control is performed on them to make the permanent magnet synchronous motors reach the required speed.

[0003] In the prior art, weak magnetic control is to negatively increase the d-axis current of the permanent magnet synchronous motor. As the speed of the permanent magnet synchronous motor increases, the d-axis current will continue to increase negatively until it reaches the limit of the d-axis current. The negatively increasing d-axis current will reduce the output torque of the permanent magnet synchronous motor. When the output torque of the permanent magnet synchronous motor is less than the load torque, the permanent magnet synchronous motor cannot continue to increase its speed. At this time, if the d-axis current continues to increase negatively, the speed of the permanent magnet synchronous motor will decrease instead of increase and cannot be maintained at the maximum speed value. Summary of the invention

[0004] The present invention aims to solve at least one of the technical problems existing in the prior art. To this end, the purpose of the present invention is to provide a household appliance and a control method thereof.

[0005] The present invention proposes a household appliance, which includes: a shell; a permanent magnet synchronous motor, which is arranged in the shell and is used to operate according to a DC input voltage; and a controller, which is configured to: determine that the permanent magnet synchronous motor is in a weak magnetic field control stage, and obtain the rotation speed of the permanent magnet synchronous motor at every preset sampling time; determine whether to limit the weak magnetic field current value output by the weak magnetic field control at the current sampling moment according to the rotation speed corresponding to the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, so as to adjust the weak magnetic field depth of the permanent magnet synchronous motor.

[0006] In addition, the household appliance according to the embodiment of the present invention may also have the following additional technical features:

[0007] Furthermore, when determining whether to limit the weak magnetic current value output by the weak magnetic control at the current sampling moment according to the speeds corresponding to the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, the controller is specifically configured to: determine whether the speed of the permanent magnet synchronous motor at the current sampling moment is greater than the speed at the previous sampling moment; when it is determined that the speed of the permanent magnet synchronous motor at the current sampling moment is greater than the speed at the previous sampling moment, not limit the weak magnetic current value output by the weak magnetic control at the current sampling moment; when it is determined that the speed of the permanent magnet synchronous motor at the current sampling moment is not greater than the speed at the previous sampling moment, limit the weak magnetic current value output by the weak magnetic control at the current sampling moment.

[0008] Furthermore, when the weak magnetic current value output by the weak magnetic control at the current sampling moment is not limited, the controller is specifically configured to: store the rotational speed of the permanent magnet synchronous motor at the current sampling moment and the weak magnetic current of the weak magnetic control at the current sampling moment, and output the weak magnetic current value of the weak magnetic control at the current sampling moment.

[0009] Furthermore, the weak magnetic current value output by the weak magnetic control at the current sampling moment is limited, and the controller is specifically configured to: limit the weak magnetic current value output by the weak magnetic control at the current sampling moment according to the weak magnetic current value stored by the weak magnetic control at the previous sampling moment.

[0010] Furthermore, when it is determined that the permanent magnet synchronous motor is in the field weakening control stage, the controller is specifically configured to: obtain the voltage vector amplitude of the permanent magnet synchronous motor; and when the voltage vector amplitude exceeds the target voltage value, determine that the permanent magnet synchronous motor is in the field weakening control stage.

[0011] Furthermore, the magnetic field weakening control includes: voltage loop magnetic field weakening control, leading angle magnetic field weakening control or single current loop magnetic field weakening control.

[0012] Furthermore, when the magnetic weakening control is the voltage loop magnetic weakening control, the controller is specifically configured to: calculate the voltage difference between the voltage vector amplitude and the target voltage value; and output the magnetic weakening current value through a PI controller or an integral controller based on the voltage difference.

[0013] Furthermore, before determining that the permanent magnet synchronous motor is in the weak magnetic field control stage, the controller is also configured to: obtain the weak magnetic field control parameters and the bus voltage value; calculate the product of the bus voltage value and the weak magnetic field control parameter, and use half of the product as the target voltage value to determine the modulation limit range that the bus voltage can withstand.

[0014] Furthermore, when the magnetic field weakening control is the single current loop magnetic field weakening control, the controller is specifically configured to: calculate the speed difference between the speed of the permanent magnet synchronous motor at the current sampling moment and the target speed; and output the magnetic field weakening current value according to the speed difference.

[0015] According to an embodiment of the present invention, the household appliance comprises: a housing, a permanent magnet synchronous motor and a controller. The permanent magnet synchronous motor is arranged in the housing and is used to operate according to a DC input voltage; the controller is configured to: determine that the permanent magnet synchronous motor is in a weak magnetic control stage, and obtain the speed of the permanent magnet synchronous motor at every preset sampling time, and determine whether to limit the weak magnetic current value output by the weak magnetic control at the current sampling time according to the speed corresponding to the permanent magnet synchronous motor at the current sampling time and the previous sampling time, so as to adjust the weak magnetic depth of the permanent magnet synchronous motor, so as to limit the weak magnetic current from continuing to decrease when the output torque of the permanent magnet synchronous motor decreases to be equal to the load torque, so as to avoid the speed of the permanent magnet synchronous motor from decreasing due to the continuous decrease of the output torque, so that the speed of the permanent magnet synchronous motor is maintained at the maximum speed value; further, when limiting the weak magnetic current value output by the weak magnetic control at the current sampling time, if the load torque decreases, the weak magnetic current value output by the weak magnetic control is no longer limited, and the weak magnetic depth is continued to be deepened, so that the speed of the permanent magnet synchronous motor continues to increase, thereby automatically adjusting the maximum weak magnetic depth according to the load condition to obtain a higher weak magnetic speed.

[0016] In response to the above-mentioned problems, the present invention also proposes a control method for household appliances, including: determining that a permanent magnet synchronous motor is in a weak magnetic field control stage; obtaining the rotational speed of the permanent magnet synchronous motor at preset sampling time intervals; determining whether to limit the weak magnetic field current value output by the weak magnetic field control at the current sampling moment according to the rotational speeds corresponding to the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, so as to adjust the weak magnetic field depth of the permanent magnet synchronous motor.

[0017] According to the control method of the household appliance of the embodiment of the present invention, by determining that the permanent magnet synchronous motor is in the field weakening control stage, the rotation speed of the permanent magnet synchronous motor is obtained at every preset sampling time, and it is determined whether to limit the field weakening current value output by the field weakening control at the current sampling time according to the rotation speed corresponding to the permanent magnet synchronous motor at the current sampling time and the previous sampling time, so as to adjust the field weakening depth of the permanent magnet synchronous motor, so as to limit the field weakening current from continuing to decrease when the output torque of the permanent magnet synchronous motor decreases to be equal to the load torque, so as to avoid the speed of the permanent magnet synchronous motor from decreasing due to the continuous decrease in the output torque, so that the speed of the permanent magnet synchronous motor is maintained at the maximum speed value; further, when the field weakening current value output by the field weakening control at the current sampling time is limited, if the load torque decreases, the field weakening current value output by the field weakening control is no longer limited, and the field weakening depth is continued to be deepened, so that the speed of the permanent magnet synchronous motor continues to increase, thereby automatically adjusting the maximum field weakening depth according to the load condition to obtain a higher field weakening speed.

[0018] Additional aspects and advantages of the present invention will be given in part in the following description and in part will be obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0020] Figure 1 is a schematic structural diagram of a household appliance according to an embodiment of the present invention;

[0021] Figure 2 is a schematic diagram of the relationship between the weak magnetic current, the permanent magnet synchronous motor speed, the output torque and the load torque according to an embodiment of the present invention;

[0022] Figure 3 is a structural block diagram of a permanent magnet synchronous motor field weakening depth control according to an embodiment of the present invention;

[0023] Figure 4 is a flow chart for determining whether to limit a field weakening current value according to an embodiment of the present invention;

[0024] Figure 5 is a schematic diagram of the relationship between the weak magnetic current, the permanent magnet synchronous motor speed, the output torque and the load torque according to another embodiment of the present invention;

[0025] Figure 6 is a structural block diagram of voltage loop magnetic weakening control according to an embodiment of the present invention;

[0026] Figure 7 is a structural block diagram of single current loop magnetic weakening control according to an embodiment of the present invention;

[0027] Figure 8 is a flow chart of a method for controlling a household appliance according to an embodiment of the present invention. DETAILED DESCRIPTION

[0028] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0029] In the description of the present invention, it should be understood that the terms "center", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0030] The terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "plurality" means two or more.

[0031] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0032] Reference below Figure 1-Figure 8 A home appliance and a control method thereof according to an embodiment of the present invention are described.

[0033] Figure 1 FIG. 1 is a schematic diagram of the structure of a household appliance according to an embodiment of the present invention. Figure 1As shown, the household appliance 1 includes: a shell 11, a permanent magnet synchronous motor 12 and a controller 13; wherein the permanent magnet synchronous motor 12 is arranged in the shell 11, and is used to operate according to the DC input voltage; the controller 13 is configured to: determine that the permanent magnet synchronous motor 12 is in the weak magnetic control stage, and obtain the rotation speed of the permanent magnet synchronous motor 12 at every preset sampling time; determine whether to limit the weak magnetic current value output by the weak magnetic control at the current sampling time according to the rotation speed corresponding to the permanent magnet synchronous motor 12 at the current sampling time and the previous sampling time, so as to adjust the weak magnetic depth of the permanent magnet synchronous motor 12.

[0034] Specifically, when the permanent magnet synchronous motor 12 is running at high speed, under normal bus voltage, the voltage requirement of the permanent magnet synchronous motor 12 cannot be met, and it is necessary to reduce the voltage requirement through magnetic field weakening control so that the permanent magnet synchronous motor 12 can reach the required speed. That is, when the permanent magnet synchronous motor 12 is driven at high speed, when the driving output voltage exceeds the bus voltage limit, it is necessary to increase the magnetic field weakening current through magnetic field weakening control to increase the magnetic resistance torque, so as to reduce the output voltage, so that the speed of the permanent magnet synchronous motor 12 can be further improved. However, in the process of magnetic field weakening control, when the load torque is constant, the relationship between the speed of the permanent magnet synchronous motor 12 and the magnetic field weakening current output by the magnetic field weakening control is not monotonic, such as Figure 2 As shown, the speed of the permanent magnet synchronous motor 12 will increase to the maximum speed value first as the weak magnetic current increases, and then the speed begins to decrease, that is, when the load torque is constant, there is a weak magnetic current point corresponding to the maximum speed value, and at this time the output torque of the permanent magnet synchronous motor 12 is equal to the load torque. Therefore, when the permanent magnet synchronous motor 12 is in the weak magnetic control stage, it is necessary to adjust the weak magnetic depth of the permanent magnet synchronous motor 12, so as to limit the weak magnetic current from continuing to decrease when the output torque of the permanent magnet synchronous motor 12 decreases to be equal to the load torque, so as to avoid the speed of the permanent magnet synchronous motor 12 from decreasing due to the continuous decrease in the output torque, so that the speed of the permanent magnet synchronous motor 12 is maintained at the maximum speed value, so that the permanent magnet synchronous motor 12 reaches and remains at the highest speed during the weak magnetic control process.

[0035] Specifically, when the load torque is constant, in order to make the speed of the permanent magnet synchronous motor 12 reach and maintain at the highest speed, the embodiment of the present invention obtains the speed of the permanent magnet synchronous motor 12 once every preset sampling time, and determines whether to limit the weak magnetic current value output by the weak magnetic control at the current sampling time according to the speed of the permanent magnet synchronous motor 12 corresponding to the current sampling time and the previous sampling time, that is, to determine whether the current weak magnetic control is excessively weak magnetic, if it is excessively weak magnetic, then limit the weak magnetic current, if it is not excessively weak magnetic, then deepen the weak magnetic depth, so that when the output torque of the permanent magnet synchronous motor 12 drops to be equal to the load torque, the weak magnetic current is limited to continue to drop, so as to avoid the speed of the permanent magnet synchronous motor 12 dropping due to the continuous drop in the output torque, so that the speed of the permanent magnet synchronous motor 12 is maintained at the maximum speed value. It can be understood that the preset sampling time can be preset in advance and stored in the controller 13, and the smaller the preset sampling time, the more accurate the adjustment of the weak magnetic depth.

[0036] In a specific embodiment, Figure 3 As shown, during the process of magnetic weakening control, the deep magnetic weakening module determines whether to limit the magnetic weakening current according to the speed of the permanent magnet synchronous motor 12 corresponding to the current sampling moment and the previous sampling moment, and controls the d-axis command current I by limiting the magnetic weakening current. d * The size of the PI (proportional-integral) controller is based on the d-axis command current I d * and d-axis current I d Adjust the d-axis command voltage V of the permanent magnet synchronous motor 12 d * , and then adjust the speed of the permanent magnet synchronous motor 12 so that the permanent magnet synchronous motor 12 reaches and remains at the maximum speed.

[0037] In one embodiment of the present invention, Figure 4 As shown, when determining whether to limit the weak magnetic current value output by the weak magnetic control at the current sampling moment according to the speed corresponding to the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, the controller is specifically configured as follows: judging whether the speed of the permanent magnet synchronous motor at the current sampling moment is greater than the speed at the previous sampling moment; when judging that the speed of the permanent magnet synchronous motor at the current sampling moment is greater than the speed at the previous sampling moment, not limiting the weak magnetic current value output by the weak magnetic control at the current sampling moment; when judging that the speed of the permanent magnet synchronous motor at the current sampling moment is not greater than the speed at the previous sampling moment, limiting the weak magnetic current value output by the weak magnetic control at the current sampling moment.

[0038] Specifically, if it is judged that the speed of the permanent magnet synchronous motor at the current sampling moment is greater than the speed at the previous sampling moment, it is considered that the speed of the permanent magnet synchronous motor has not reached the maximum speed value, and the current weak magnetic control is not excessive weak magnetic, then the weak magnetic current value output by the weak magnetic control at the current sampling moment is not restricted, and the weak magnetic depth is continued to be deepened to increase the speed of the permanent magnet synchronous motor; if it is judged that the speed of the permanent magnet synchronous motor at the current sampling moment is not greater than the speed at the previous sampling moment, it is considered that the speed of the permanent magnet synchronous motor has reached the maximum speed value, and the current weak magnetic control is excessive weak magnetic, then the weak magnetic current value output by the weak magnetic control at the current sampling moment is restricted to maintain the speed of the permanent magnet synchronous motor at the maximum speed value.

[0039] Furthermore, when the weak magnetic current value output by the weak magnetic control at the current sampling moment is limited, if the load torque decreases, the weak magnetic current corresponding to the maximum speed value of the permanent magnet synchronous motor will increase, and the speed of the permanent magnet synchronous motor at the next sampling moment will increase and be greater than the speed at the current sampling moment. Then, at the next sampling moment, the weak magnetic current value output by the weak magnetic control will no longer be limited, and the weak magnetic depth will continue to be deepened, so that the speed of the permanent magnet synchronous motor will continue to increase. In this way, the embodiment of the present invention can make the speed of the permanent magnet synchronous motor reach the maximum speed value matching the current load torque, that is, when the load torque changes, the permanent magnet synchronous motor can still reach and maintain the highest speed.

[0040] In a specific embodiment, Figure 5 As shown in the figure, when the load torque becomes smaller, the maximum speed value of the permanent magnet synchronous motor increases from the maximum speed point 1 to the maximum speed point 2, and the corresponding weak magnetic current will also increase. The speed of the permanent magnet synchronous motor at the next sampling moment (for example, a certain moment between the maximum speed point 1 and the maximum speed point 2) will increase, which is greater than the speed at the current sampling moment (for example, the moment corresponding to the maximum speed point 1). At the next sampling moment, the weak magnetic current value output by the weak magnetic control is no longer restricted, and the weak magnetic depth continues to be deepened, so that the speed of the permanent magnet synchronous motor continues to increase until it reaches the maximum speed point 2. In this way, the speed of the permanent magnet synchronous motor can change with the change of the load torque, so that the permanent magnet synchronous motor can automatically adjust the maximum weak magnetic depth according to the load conditions during the weak magnetic process, thereby obtaining a higher weak magnetic speed.

[0041] In one embodiment of the present invention, when the weak magnetic current value output by the weak magnetic control at the current sampling moment is not limited, the controller is specifically configured to: store the rotational speed of the permanent magnet synchronous motor at the current sampling moment and the weak magnetic current of the weak magnetic control at the current sampling moment, and output the weak magnetic current value of the weak magnetic control at the current sampling moment.

[0042] In a specific embodiment, Figure 3As shown, when the speed of the permanent magnet synchronous motor at the current sampling moment is greater than the speed at the previous sampling moment, for example, the speed at the current moment is 5000rpm, the speed at the previous sampling moment is 4500rpm, and the time interval between the current sampling moment and the previous sampling moment is, for example, 0.1 second, the weak magnetic current value output by the weak magnetic control at the current sampling moment is not restricted, that is, the speed of the permanent magnet synchronous motor at the current sampling moment is 5000rpm and the weak magnetic current value of the weak magnetic control at the current sampling moment are stored, and the weak magnetic current value at the current sampling moment is used as the d-axis command current I d * Sent to the PI controller so that the PI controller can generate the current I according to the d-axis command current I d * and d-axis current I d Adjust the d-axis command voltage V of the permanent magnet synchronous motor d * , so that the speed of the permanent magnet synchronous motor continues to increase.

[0043] In one embodiment of the present invention, the weak magnetic current value output by the weak magnetic control at the current sampling moment is limited, and the controller is specifically configured to: limit the weak magnetic current value output by the weak magnetic control at the current sampling moment according to the weak magnetic current value stored by the weak magnetic control at the previous sampling moment.

[0044] In a specific embodiment, Figure 3 As shown in FIG. 1 , when the speed of the permanent magnet synchronous motor at the current sampling moment is not greater than the speed at the previous sampling moment, for example, the speed at the current moment is 5500 rpm, the speed at the previous sampling moment is 6000 rpm, and the time interval between the current sampling moment and the previous sampling moment is, for example, 0.1 second, it is necessary to limit the weak magnetic current value output by the weak magnetic control at the current sampling moment, that is, the weak magnetic current value stored by the permanent magnet synchronous motor at the previous sampling moment is used as the d-axis command current I d * Sent to the PI controller so that the PI controller can generate the current I according to the d-axis command current I d * and d-axis current I d Adjust the d-axis command voltage V of the permanent magnet synchronous motor d * , so that the speed of the permanent magnet synchronous motor is maintained at the speed of the previous sampling moment.

[0045] In one embodiment of the present invention, when it is determined that the permanent magnet synchronous motor is in the field weakening control stage, the controller is specifically configured to: obtain the voltage vector amplitude of the permanent magnet synchronous motor; when the voltage vector amplitude exceeds the target voltage value, determine that the permanent magnet synchronous motor is in the field weakening control stage.

[0046] In a specific embodiment, whether the permanent magnet synchronous motor is in the field weakening control stage is determined according to the magnitude relationship between the voltage vector amplitude of the permanent magnet synchronous motor and the target voltage value. The direct axis voltage of the permanent magnet synchronous motor is, for example, denoted as V d * , the quadrature axis voltage is denoted as V q * , calculate the direct axis voltage V d * and the quadrature axis voltage V q * The root mean square of the voltage vector is recorded as V s , that is, the voltage vector amplitude V s The calculation formula is as follows:

[0047]

[0048] The controller obtains the voltage vector amplitude V of the permanent magnet synchronous motor s , determine the voltage vector amplitude V s The relationship between the voltage vector amplitude V s When the target voltage value is exceeded, the voltage vector amplitude V of the permanent magnet synchronous motor is considered to be s When the bus voltage value is exceeded, that is, the bus voltage is exceeded in the limit range of modulation that can be tolerated, it is determined that the permanent magnet synchronous motor is in the weak magnetic field control stage.

[0049] In one embodiment of the present invention, the flux weakening control includes: voltage loop flux weakening control, lead angle flux weakening control or single current loop flux weakening control.

[0050] Specifically, the weak magnetic field control in the embodiment of the present invention includes: voltage loop weak magnetic field control, lead angle weak magnetic field control or single current loop weak magnetic field control. Among them, the voltage loop weak magnetic field control reduces the magnetic field strength by reducing the voltage, calculates the target voltage according to the required motor performance parameters speed and torque, limits the actual voltage to a lower level, and reduces the voltage vector amplitude to achieve weak magnetic field control; the lead angle weak magnetic field control achieves weak magnetic field control by adjusting the current phase angle. Under the magnetic field of a normal permanent magnet synchronous motor, the current phase angle and the voltage phase angle remain consistent, while in the lead angle weak magnetic field control, the current phase angle is advanced, resulting in the magnetic field of the permanent magnet synchronous motor being offset relative to the current, thereby reducing the magnetic field strength of the permanent magnet synchronous motor; the single current loop weak magnetic field control only controls one current component, usually the d-axis current, and reduces the magnetic field strength of the permanent magnet synchronous motor by reducing the amplitude of the d-axis current.

[0051] In one embodiment of the present invention, when the magnetic field weakening control is voltage loop magnetic field weakening control, the controller is specifically configured to: calculate the voltage difference between the voltage vector amplitude and the target voltage value; and output the magnetic field weakening current value through a PI controller or an integral controller according to the voltage difference.

[0052] Specifically, if Figure 6 As shown, determine the voltage vector magnitude V s Then, calculate the voltage vector magnitude V s The voltage difference with the target voltage value is used to output the weak magnetic current value through the PI controller or the integral controller according to the voltage difference to adjust the d-axis command current I of the permanent magnet synchronous motor. d * , thereby controlling the voltage vector amplitude V s The normal operation of the permanent magnet synchronous motor is guaranteed within the tolerable limit of the bus voltage.

[0053] In one embodiment of the present invention, before determining that the permanent magnet synchronous motor is in the weak magnetic field control stage, the controller is also configured to: obtain the weak magnetic field control parameters and the bus voltage value; calculate the product of the bus voltage value and the weak magnetic field control parameter, and use half of the product as the target voltage value to determine the modulation limit range that the bus voltage can withstand.

[0054] In a specific embodiment, Figure 6 As shown, before the controller determines that the permanent magnet synchronous motor meets the weak magnetic control condition, it obtains the weak magnetic control parameter, for example, K fw , the bus voltage value is recorded as V dc , calculate the bus voltage value V dc and the field weakening control parameter K fw The target voltage is calculated by multiplying the product by half of the product. The target voltage is then calculated as follows: In order to determine the bus voltage can withstand modulation limit range.

[0055] In one embodiment of the present invention, when the magnetic field weakening control is single current loop magnetic field weakening control, the controller is specifically configured to: calculate the speed difference between the permanent magnet synchronous motor at the current sampling moment and the target speed; and output the magnetic field weakening current value according to the speed difference.

[0056] Specifically, if Figure 7 As shown, in single current loop weak magnetic control, calculate the actual speed ω ^ and the target speed ω * The speed difference is calculated by outputting the field weakening current value according to the speed difference to adjust the d-axis command current I of the permanent magnet synchronous motor. d * , that is, the current command of the speed loop after torque conversion is used as the d-axis command current I of the permanent magnet synchronous motor d * .

[0057] According to an embodiment of the present invention, the household appliance comprises: a housing, a permanent magnet synchronous motor and a controller. The permanent magnet synchronous motor is arranged in the housing and is used to operate according to a DC input voltage; the controller is configured to: determine that the permanent magnet synchronous motor is in a weak magnetic control stage, and obtain the speed of the permanent magnet synchronous motor at every preset sampling time, and determine whether to limit the weak magnetic current value output by the weak magnetic control at the current sampling time according to the speed corresponding to the permanent magnet synchronous motor at the current sampling time and the previous sampling time, so as to adjust the weak magnetic depth of the permanent magnet synchronous motor, so as to limit the weak magnetic current from continuing to decrease when the output torque of the permanent magnet synchronous motor decreases to be equal to the load torque, so as to avoid the speed of the permanent magnet synchronous motor from decreasing due to the continuous decrease of the output torque, so that the speed of the permanent magnet synchronous motor is maintained at the maximum speed value; further, when limiting the weak magnetic current value output by the weak magnetic control at the current sampling time, if the load torque decreases, the weak magnetic current value output by the weak magnetic control is no longer limited, and the weak magnetic depth is continued to be deepened, so that the speed of the permanent magnet synchronous motor continues to increase, thereby automatically adjusting the maximum weak magnetic depth according to the load condition to obtain a higher weak magnetic speed.

[0058] A further embodiment of the present invention also discloses a control method for household electrical appliances, such as Figure 8 As shown, the method comprises the following steps:

[0059] Step S1: Determine whether the permanent magnet synchronous motor is in a flux weakening control stage.

[0060] Step S2: Obtain the rotation speed of the permanent magnet synchronous motor at every preset sampling time.

[0061] Step S3: determining whether to limit the field weakening current value output by the field weakening control at the current sampling moment according to the speed of the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, so as to adjust the field weakening depth of the permanent magnet synchronous motor.

[0062] In one embodiment of the present invention, determining whether to limit the weak magnetic current value output by the weak magnetic control at the current sampling moment according to the rotational speed corresponding to the current sampling moment and the previous sampling moment of the permanent magnet synchronous motor includes: judging whether the rotational speed of the permanent magnet synchronous motor at the current sampling moment is greater than the rotational speed at the previous sampling moment; when judging that the rotational speed of the permanent magnet synchronous motor at the current sampling moment is greater than the rotational speed at the previous sampling moment, not limiting the weak magnetic current value output by the weak magnetic control at the current sampling moment; when judging that the rotational speed of the permanent magnet synchronous motor at the current sampling moment is not greater than the rotational speed at the previous sampling moment, limiting the weak magnetic current value output by the weak magnetic control at the current sampling moment.

[0063] In one embodiment of the present invention, when the weak magnetic current value output by the weak magnetic control at the current sampling moment is not limited, it includes: storing the rotation speed of the permanent magnet synchronous motor at the current sampling moment and the weak magnetic current of the weak magnetic control at the current sampling moment, and outputting the weak magnetic current value of the weak magnetic control at the current sampling moment.

[0064] In one embodiment of the present invention, limiting the field weakening current value output by the field weakening control at the current sampling moment includes: limiting the field weakening current value output by the field weakening control at the current sampling moment according to the field weakening current value stored by the field weakening control at the previous sampling moment.

[0065] In one embodiment of the present invention, determining that the permanent magnet synchronous motor is in the field weakening control stage includes: obtaining the voltage vector amplitude of the permanent magnet synchronous motor; and determining that the permanent magnet synchronous motor is in the field weakening control stage when the voltage vector amplitude exceeds the target voltage value.

[0066] In one embodiment of the present invention, the flux weakening control includes: voltage loop flux weakening control, lead angle flux weakening control or single current loop flux weakening control.

[0067] In one embodiment of the present invention, when the magnetic field weakening control is voltage loop magnetic field weakening control, it includes: calculating the voltage difference between the voltage vector amplitude and the target voltage value; and outputting the magnetic field weakening current value through a PI controller or an integral controller according to the voltage difference.

[0068] In one embodiment of the present invention, before determining that the permanent magnet synchronous motor is in the weak magnetic field control stage, it includes: obtaining the weak magnetic field control parameters and the bus voltage value; calculating the product of the bus voltage value and the weak magnetic field control parameters, and taking half of the product as the target voltage value to determine the modulation limit range that the bus voltage can withstand.

[0069] In one embodiment of the present invention, when the magnetic field weakening control is single current loop magnetic field weakening control, the controller is specifically configured to: calculate the speed difference between the permanent magnet synchronous motor at the current sampling moment and the target speed; and output the magnetic field weakening current value according to the speed difference.

[0070] It should be noted that when the control method of the household appliance in the embodiment of the present invention controls the household appliance, its specific implementation method is similar to the specific implementation method of the household appliance in the embodiment of the present invention. Please refer to the description of the device part for details. In order to reduce redundancy, it will not be repeated here.

[0071] According to the control method of the household appliance of the embodiment of the present invention, by determining that the permanent magnet synchronous motor is in the field weakening control stage, the rotation speed of the permanent magnet synchronous motor is obtained at every preset sampling time, and it is determined whether to limit the field weakening current value output by the field weakening control at the current sampling time according to the rotation speed corresponding to the permanent magnet synchronous motor at the current sampling time and the previous sampling time, so as to adjust the field weakening depth of the permanent magnet synchronous motor, so as to limit the field weakening current from continuing to decrease when the output torque of the permanent magnet synchronous motor decreases to be equal to the load torque, so as to avoid the speed of the permanent magnet synchronous motor from decreasing due to the continuous decrease in the output torque, so that the speed of the permanent magnet synchronous motor is maintained at the maximum speed value; further, when the field weakening current value output by the field weakening control at the current sampling time is limited, if the load torque decreases, the field weakening current value output by the field weakening control is no longer limited, and the field weakening depth is continued to be deepened, so that the speed of the permanent magnet synchronous motor continues to increase, thereby automatically adjusting the maximum field weakening depth according to the load condition to obtain a higher field weakening speed.

[0072] In the description of this specification, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials, or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example.

[0073] Although the embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the claims and their equivalents.

Claims

1. A household appliance, characterized in that: include: case; a permanent magnet synchronous motor, disposed in the housing and configured to operate according to a DC input voltage; The controller is configured to: determine that the permanent magnet synchronous motor is in a field weakening control stage, and obtain the rotation speed of the permanent magnet synchronous motor at every preset sampling time; Determine whether to limit the weakening current value output by the weakening control at the current sampling moment according to the rotation speed of the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, so as to adjust the weakening depth of the permanent magnet synchronous motor.

2. The household appliance according to claim 1, characterized in that: When determining whether to limit the weakening current value output by the weakening magnetic control at the current sampling moment according to the speed of the permanent magnet synchronous motor corresponding to the current sampling moment and the previous sampling moment, the controller is specifically configured as follows: Determine whether the rotation speed of the permanent magnet synchronous motor at the current sampling time is greater than the rotation speed at the previous sampling time; When it is determined that the rotation speed of the permanent magnet synchronous motor at the current sampling moment is greater than the rotation speed at the previous sampling moment, the weakening current value output by the weakening magnetic control at the current sampling moment is not limited; When it is determined that the rotation speed of the permanent magnet synchronous motor at the current sampling moment is not greater than the rotation speed at the previous sampling moment, the weakening current value output by the weakening control at the current sampling moment is limited.

3. The household appliance according to claim 2, characterized in that: When the field weakening current value output by the field weakening control at the current sampling time is not limited, the controller is specifically configured as follows: The rotation speed of the permanent magnet synchronous motor at the current sampling moment and the weak magnetic current of the weak magnetic control at the current sampling moment are stored, and the weak magnetic current value of the weak magnetic control at the current sampling moment is output.

4. The household appliance according to claim 3, characterized in that: The weak magnetic current value output by the weak magnetic control at the current sampling time is limited, and the controller is specifically configured as follows: The field weakening current value output by the field weakening control at the current sampling moment is limited according to the field weakening current value stored by the field weakening control at the previous sampling moment.

5. The household appliance according to claim 1, characterized in that: When it is determined that the permanent magnet synchronous motor is in the field weakening control stage, the controller is specifically configured as follows: Obtaining a voltage vector amplitude of the permanent magnet synchronous motor; When the voltage vector amplitude exceeds the target voltage value, it is determined that the permanent magnet synchronous motor is in the magnetic field weakening control stage.

6. The household appliance according to claim 5, characterized in that: The magnetic field weakening control includes: voltage loop magnetic field weakening control, leading angle magnetic field weakening control or single current loop magnetic field weakening control.

7. The household appliance according to claim 6, characterized in that: When the magnetic field weakening control is the voltage loop magnetic field weakening control, the controller is specifically configured as follows: Calculating a voltage difference between the voltage vector amplitude and the target voltage value; According to the voltage difference, the field weakening current value is outputted through a PI controller or an integral controller.

8. The household appliance according to claim 5, characterized in that: Before determining that the permanent magnet synchronous motor is in the field weakening control stage, the controller is further configured to: Obtain weak magnetic control parameters and bus voltage values; The product of the bus voltage value and the weak magnetic control parameter is calculated, and half of the product is used as the target voltage value to determine the modulation limit range that the bus voltage can withstand.

9. The household appliance according to claim 6, characterized in that: When the magnetic field weakening control is the single current loop magnetic field weakening control, the controller is specifically configured as follows: Calculating the speed difference between the speed of the permanent magnet synchronous motor at the current sampling moment and the target speed; The field weakening current value is output according to the rotation speed difference.

10. A method for controlling a household appliance, characterized in that: include: Determine that the permanent magnet synchronous motor is in the field weakening control stage; Obtaining the rotation speed of the permanent magnet synchronous motor at every preset sampling time; Determine whether to limit the weakening current value output by the weakening control at the current sampling moment according to the rotation speed of the permanent magnet synchronous motor at the current sampling moment and the previous sampling moment, so as to adjust the weakening depth of the permanent magnet synchronous motor.

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