Electric appliance and control method thereof

Abstract

The embodiment of the application belongs to the technical field of electrical equipment, and provides an electrical equipment and a control method thereof. The electrical equipment comprises: a motor configured to provide a power source; a frequency converter configured to drive the motor; and a control unit connected with the frequency converter, wherein the control unit is configured to: predict position information of a rotor of the motor according to three-phase currents of the motor driven by the frequency converter; determine a dead-time compensation time of the frequency converter according to the position information and the three-phase currents, wherein the dead-time compensation time is used to compensate current distortion of the three-phase currents; determine a target driving signal of the frequency converter according to the dead-time compensation time, and send the target driving signal to the frequency converter, so that the frequency converter drives the motor based on the target driving signal. The above scheme can effectively reduce low-frequency noise during motor operation, thereby improving the user experience.

Description

Technical Field

[0001] This application relates to the field of electrical technology. More specifically, it relates to an electrical device and its control method. Background Technology

[0002] Due to their advantages such as high power density, high efficiency, and ease of implementing variable frequency speed control, permanent magnet synchronous motors (PMSMs) are currently widely used as power sources in many electrical appliances (e.g., air conditioners, refrigerators). However, during operation, the motor current, as the excitation source, can experience current distortion due to the nonlinear characteristics of the frequency converter (e.g., dead time). This distortion leads to harmonic torque, causing torsional resonance in the motor shaft and fan blades, resulting in low-frequency noise. Summary of the Invention

[0003] The electrical equipment and control method provided in this application are used to reduce the low-frequency noise of the motor of the electrical equipment.

[0004] In a first aspect, embodiments of this application provide an electrical device, including: a motor configured to provide a power source;

[0005] A frequency converter is configured to drive the motor;

[0006] The control unit connected to the frequency converter is configured to:

[0007] Based on the three-phase current of the motor driven by the frequency converter, predict the position information of the motor rotor;

[0008] Based on the location information and the three-phase current, the dead-zone compensation time of the frequency converter is determined; the dead-zone compensation time is used to compensate for the current distortion of the three-phase current.

[0009] Based on the dead-time compensation time, the target drive signal of the frequency converter is determined and sent to the frequency converter so that the frequency converter drives the motor based on the target drive signal.

[0010] The above solution, by designing a dead-time compensation period, compensates the original asymmetrical drive signal caused by the dead time of the motor into a relatively symmetrical target drive signal. This can reduce the low-frequency noise during motor operation caused by the nonlinear output of the motor voltage due to the asymmetrical drive signal, thereby effectively improving the user experience.

[0011] In some embodiments, the position information includes the angular frequency ω of the motor rotor, and the control unit is configured to:

[0012] Obtain the highest and lowest speeds of the motor;

[0013] The initial dead zone compensation time is determined based on the highest speed, the lowest speed, and the rotor angular frequency ω.

[0014] The dead zone compensation time is determined based on the initial dead zone compensation time and the three-phase current.

[0015] In some embodiments, the control unit is configured to:

[0016] Obtain a first difference between the upper limit of dead zone compensation time corresponding to the highest speed and the upper limit of dead zone compensation time corresponding to the lowest speed, and a second difference between the highest speed and the lowest speed;

[0017] The initial dead zone compensation time is determined based on the first difference, the second difference, and the angular frequency ω.

[0018] In some embodiments, the control unit is configured to:

[0019] Based on the relationship between the magnitude of the three-phase current and the preset value, the compensation coefficient corresponding to the initial dead zone compensation time is determined;

[0020] The initial dead zone compensation time is processed according to the compensation coefficient to determine the dead zone compensation time.

[0021] In some embodiments, the control unit is configured to:

[0022] The initial drive signal of the frequency converter is corrected based on the dead-time compensation time to determine the target drive signal.

[0023] In some embodiments, the control unit is configured to:

[0024] The three-phase current is transformed to obtain the feedback current of the three-phase current in the rotating coordinate system;

[0025] Based on the feedback current and the reference voltage of the frequency converter, the shaft error Δθ of the motor is predicted;

[0026] Based on the shaft error Δθ, predict the rotor position θ and the angular frequency ω.

[0027] In some embodiments, the feedback current includes a d-axis feedback current and a q-axis feedback current, and the control unit is configured to:

[0028] The reference voltage of the d-axis is determined based on the feedback current of the d-axis and the reference current of the d-axis.

[0029] The reference voltage of the q-axis is determined based on the feedback current of the q-axis and the reference current of the q-axis, wherein the reference current of the q-axis is determined based on the angular frequency ω and the reference angular frequency.

[0030] In some embodiments, the control unit is configured to:

[0031] Based on the position θ, the reference voltage of the d-axis and the reference voltage of the q-axis are transformed to obtain the reference voltage of the α-axis and the reference voltage of the β-axis.

[0032] Space vector pulse width modulation is performed on the reference voltages of the α-axis and β-axis to obtain the initial drive signal of the frequency converter.

[0033] Secondly, embodiments of this application provide a method for controlling an electrical device, the electrical device comprising:

[0034] The electric motor is configured to provide a power source;

[0035] A frequency converter is configured to drive the motor;

[0036] The method includes:

[0037] Based on the three-phase current of the motor driven by the frequency converter, predict the position information of the motor rotor;

[0038] Based on the location information and the three-phase current, the dead-zone compensation time of the frequency converter is determined; the dead-zone compensation time is used to compensate for the current distortion of the three-phase current.

[0039] Based on the dead-time compensation time, the target drive signal of the frequency converter is determined and sent to the frequency converter so that the frequency converter drives the motor based on the target drive signal.

[0040] Optionally, the position information includes the angular frequency ω of the motor rotor, and determining the dead-time compensation time of the frequency converter based on the position information and the three-phase current includes:

[0041] Obtain the highest and lowest speeds of the motor;

[0042] The initial dead zone compensation time is determined based on the highest speed, the lowest speed, and the rotor angular frequency ω.

[0043] The dead zone compensation time is determined based on the initial dead zone compensation time and the three-phase current.

[0044] Thirdly, embodiments of this application provide a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, are used to implement the first aspect and / or various possible implementations of the first aspect.

[0045] Fourthly, embodiments of this application provide a computer program product, including a computer program that, when executed by a processor, implements the first aspect and / or various possible implementations of the first aspect.

[0046] The electrical equipment and control method provided in this application include: a motor configured to provide a power source; a frequency converter configured to drive the motor; and a control unit connected to the frequency converter. The control unit is configured to: predict the position information of the motor rotor based on the three-phase current of the motor driven by the frequency converter; determine the dead-zone compensation time of the frequency converter based on the position information and the three-phase current; the dead-zone compensation time is used to compensate for the current distortion of the three-phase current; determine the target drive signal of the frequency converter based on the dead-zone compensation time, and send the target drive signal to the frequency converter so that the frequency converter drives the motor based on the target drive signal. This solution, by designing a dead-zone compensation time, compensates the original asymmetrical drive signal caused by the dead zone of the motor into a relatively symmetrical target drive signal. This reduces the low-frequency noise during motor operation caused by the nonlinear output of the motor voltage due to the asymmetrical drive signal, thereby effectively improving the user experience. Attached Figure Description

[0047] To more clearly illustrate the implementation methods in the embodiments of this application or related technologies, the accompanying drawings used in the description of the embodiments or related technologies will be briefly introduced below. Obviously, the accompanying drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings.

[0048] Figure 1 A schematic diagram of the structure of an electrical device provided in this application;

[0049] Figure 2 A model diagram of the rotor magnetic pole position and shaft error of a motor provided for an embodiment of this application;

[0050] Figure 3 A schematic diagram of the principle of motor vector control provided in this application embodiment. Figure 1 ;

[0051] Figure 4 A schematic diagram of the principle of motor vector control provided in this application embodiment. Figure 2 ;

[0052] Figure 5 A flowchart illustrating a control method for an electrical device provided in an embodiment of this application;

[0053] Figure 6 This is a schematic diagram of a noise test result provided in this application.

[0054] The accompanying drawings illustrate specific embodiments of this application, which will be described in more detail below. These drawings and descriptions are not intended to limit the scope of the concept in any way, but rather to illustrate the concept of this application to those skilled in the art through reference to particular embodiments. Detailed Implementation

[0055] To make the objectives, implementation methods and advantages of this application clearer, the exemplary implementation methods of this application will be clearly and completely described below with reference to the accompanying drawings of the exemplary embodiments of this application. Obviously, the described exemplary embodiments are only some embodiments of this application, and not all embodiments.

[0056] It should be noted that the brief descriptions of terms in this application are only for the convenience of understanding the embodiments described below, and are not intended to limit the embodiments of this application. Unless otherwise stated, these terms should be understood in their ordinary and common meaning.

[0057] Furthermore, the terms “comprising” and “having”, and any variations thereof, are intended to cover but not exclusively include, for example, a product or device that includes a series of components is not necessarily limited to those that are explicitly listed, but may include other components that are not explicitly listed or that are inherent to such product or device.

[0058] The terms "first" and "second" are configured for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this application, unless otherwise stated, "a plurality of" means two or more.

[0059] In the description of this application, it should be noted that, unless otherwise expressly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection between two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0060] To facilitate understanding, we will first provide a brief introduction and explanation of some basic technical concepts involved in the embodiments of this invention.

[0061] Dead time occurs because IGBTs are not ideal switching devices; their turn-on and turn-off times are not strictly synchronized. If voltage is applied across their terminals, it can cause a short circuit in the DC power supply, damaging the bridge arm power devices—a phenomenon known as "bridge arm shoot-through." Therefore, to ensure reliable device operation, bridge arm shoot-through must be avoided, leading to the generation of dead time. This means that one IGBT must turn off first, and then the other IGBT must turn on at the end of the dead time. This avoids shoot-through caused by the asymmetry between turn-on and turn-off times.

[0062] The Park Transformation (Park) is a commonly used coordinate transformation for analyzing the operation of synchronous motors. The Park Transform projects the three-phase currents (a, b, c) of the stator onto the direct axis (d-axis), the quadrature axis (q-axis), and the zero axis perpendicular to the dq plane, which rotate with the rotor. This diagonalizes the stator inductance matrix, simplifying the analysis of synchronous motor operation. In other words, it transforms the abc coordinate system to the dq coordinate system.

[0063] The Clarke Transform (Clark) projects the three-phase coordinates (a, b, c) onto the α and β axes. For three-phase balanced electrical signals, the Clarke Transform is a proven method for dimensionality reduction. In fact, this transformation can project information from 3D space to 2D space without losing any information.

[0064] Space Vector Pulse Width Modulation (SVPWM) uses the ideal flux linkage circle of a three-phase symmetrical motor stator when powered by a three-phase symmetrical sinusoidal voltage as a reference standard. It generates a PWM wave by appropriately switching different switching modes of the three-phase inverter, and then uses the resulting actual flux linkage vector to track the accurate flux linkage circle. Traditional SPWM methods focus on generating a frequency- and voltage-adjustable sinusoidal power supply, while SVPWM considers the inverter system and asynchronous motor as a whole, resulting in a simpler model that is easier for real-time microprocessor control.

[0065] As mentioned earlier, current distortion exists due to the nonlinear characteristics of the frequency converter (e.g., dead time), which leads to harmonic torque, causing torsional resonance of the motor shaft and fan blades, resulting in low-frequency noise.

[0066] In view of this, embodiments of this application provide an electrical device that, by introducing dead-time compensation, compensates for current distortion, thereby reducing the proportion of nonlinear output of the frequency converter and suppressing noise.

[0067] The electrical equipment and control methods for the electrical equipment provided in this application are described below.

[0068] Figure 1 This is a schematic diagram of the structure of an electrical device 10 provided in an embodiment of this application, as shown below. Figure 1 As shown, the electrical equipment 10 includes: a control unit 101, a frequency converter 102, and a motor 103.

[0069] Among them, motor 103 is a three-phase permanent magnet synchronous motor, which has a device with permanent magnets and a stator with three-phase armature coils.

[0070] The inverter 102 provides a three-phase AC voltage consisting of phases a, b, and c to the motor 103 based on the rotor position of the motor 103. The control unit 101 provides a PWM signal to the inverter 102 circuit to achieve the required vector control based on the detected motor current.

[0071] Figure 2 A model diagram of the rotor magnetic pole position and shaft error of a motor provided in this application embodiment is shown below. Figure 2 As shown, 2 is a permanent magnet installed on the rotor of the motor. In a rotating coordinate system that rotates at the same speed as the rotational speed of the magnetic flux generated by the permanent magnet 2, the direction of the magnetic flux generated by the permanent magnet 2 is taken as the d-axis, and the rotational axis corresponding to the d-axis is taken as the dc-axis. The phase that leads the d-axis by 90 degrees electrically is taken as the q-axis, and the phase that leads the dc-axis by 90 degrees electrically is taken as the dq-axis.

[0072] The rotational coordinate system corresponding to the real axis is a coordinate system that selects the d-axis and q-axis as coordinate axes, and this coordinate system is called the dq-axis. The rotational coordinate system for control is a coordinate system that selects the dc-axis and dq-axis as coordinate axes, and this coordinate system is called the dcqc-axis.

[0073] In some embodiments of this application, the dcqc axis is the estimated position of the motor, representing the axis on the control side of the rotational coordinate in general torque control, and is denoted as the control axis; the dq axis is the actual position of the motor, representing the axis on the AC motor side of the rotational coordinate, and is denoted as the real axis.

[0074] The dq axis rotates, and its rotational speed is expressed by ω. ref The dcqc axis also rotates, and its rotational speed is denoted by ω. In the dq axis, θ... refThis represents the d-axis angle (phase) as viewed from the fixed axis direction of the armature coil in phase a. Similarly, in the dcqc axis, θ represents the dc-axis angle (phase) as viewed from the fixed axis direction of the armature coil in phase a. (The last two sentences are incomplete and require further context.) ref The angle represented is an electrical angle, also commonly referred to as rotor position or magnetic pole position. It is determined by ω and ωp. ref The rotational speed indicated is the angular velocity in electrical angles.

[0075] Wherein, the actual d-axis position of the rotor (i.e., θ) ref The angular difference between the estimated dc axis position (θ) and the estimated dc axis position (θ) is called the axis error Δθ. Control unit 101 performs vector control to make θ and θ... ref The control axis and the real axis are basically consistent (i.e., the control axis error Δθ is zero), and the d-axis and q-axis are aligned with the dc-axis and qc-axis respectively, thus realizing positionless observation of the permanent magnet synchronous motor rotor.

[0076] The voltage command values ​​(also known as reference voltages) representing the target values ​​of the DC-axis voltage and the QC-axis voltage are respectively determined by the DC voltage command value U. d_ref and qc axis voltage command value U d_ref This indicates the target current command values ​​for the DC-axis voltage and QC-axis, respectively, derived from the DC-axis current command value id. ref and qc axis current command value iq ref express.

[0077] The a-phase, b-phase, and c-phase components of the motor voltage are determined by the a-phase voltage command value Ua. ref Phase b voltage command value Ub ref and the command value of phase c voltage Uc ref The three-phase voltage command value is used to represent this.

[0078] See Figure 3 This describes the principle of motor vector control, which uses dual closed-loop control of speed and current, with the speed loop as the outer loop and the current loop as the inner loop.

[0079] First, the working principle of the current loop will be explained.

[0080] The phase a current ia and phase b current ib supplied to the motor (PMSM) by the inverter 102 are detected by a current detection unit (not shown). The phase c current ic is calculated using the formula "ic = -ia - ib". ia, ib, and ic are the currents of the armature coils of phase A, phase B, and phase C in the stator of the motor, respectively.

[0081] The control unit 101 can transform the coordinates of the A-phase current ia and the B-phase current ib to the dcqc axis based on the rotor position θ, and then calculate and output the dc axis current id and the qc axis current iq.

[0082] In the vector control of the motor, the three-phase currents ia / ib / ic are transformed by Clark to obtain iα and iβ, and then iα and iβ are transformed by Park to obtain iq(iq_fb) and id(id_fb).

[0083] Then, iq and id are respectively related to iq ref and ID ref Calculate the q-axis current error and d-axis current error. Perform a PI integral transformation on the q-axis and d-axis current error values ​​to obtain the DC voltage command value U. d_ref and qc axis voltage command value U q_ref .

[0084] In some embodiments of this application, current feedback control, such as proportional-integral control, is used to minimize the current error (id). ref -id) and (iq) ref -iq) converge to zero.

[0085] Control unit 101 can be based on U q_ref and U d_ref And the rotor position θ, will U q_ref and U d_ref The three-phase voltage command values ​​are calculated and output after being transformed to a fixed coordinate axis by the inverse Park transformation.

[0086] That is, for U q_ref and U d_ref Perform the inverse Park transform to obtain U α_ref and U β_ref Then, the PWM signal is obtained through SVPWM (Space Vector Pulse Width Modulation) operation. The PWM signal controls the state of the switching transistors in the inverter 102 and outputs the three-phase voltage command value to drive the motor 30 to rotate.

[0087] Secondly, the working principle of the speed loop will be explained.

[0088] Still referencing Figure 3 The control unit 101 can use the target speed command value ω based on the rotor speed ω. ref Subtract the rotational speed ω, and then use a PI controller to adjust the rotational speed to obtain iq. ref .

[0089] The position observer in control unit 101 estimates the motor rotor position based on the d / q axis feedback current i. d and i q and d / q axis command voltage U q_ref and U d_ref Determine Δθ (shaft error). Based on the shaft error Δθ output by the position observer, the phase-locked loop (PLL) obtains the rotor position θ and angular frequency ω, and then performs closed-loop control of the motor speed through the outer speed loop. Any existing method can be used to estimate the rotor position θ and rotor speed ω, which will not be elaborated here.

[0090] The motor equations in the rotating coordinate system are as follows:

[0091]

[0092] r is the motor winding resistance; Id is the d-axis current feedback value, Iq is the q-axis current value, Ke is the flux linkage of the permanent magnet synchronous motor nail, and ω is the motor angular frequency. Ld and Lq are the motor d-axis inductances, respectively.

[0093] The motor's operating modulation rate (KhV1) is defined as the output voltage modulation ratio, KhV1 = Vs / 0.5Vdc, where Vs is the actual total output voltage vector magnitude and Vdc is the DC bus voltage input to the frequency converter.

[0094] Within the linear modulation region of the motor, i.e., within the inscribed circle of the vector hexagon, Vs = sqrt(Ud*Ud + Uq*Uq) can be calculated in real-time using software. When the output voltage is low, the effective vector synthesis ratio may be small, resulting in a very small duty cycle output. Because motors often use three-phase six-transistor frequency converters for frequency conversion control, dead time settings are required to prevent simultaneous conduction of the upper and lower bridge arms. To optimize current zero-crossing distortion, dead time compensation for the switching transistors is increased. This increased dead time compensation leads to PWM output asymmetry, resulting in non-linear motor voltage output and thus noise.

[0095] The error voltage caused by the dead time is:

[0096] △V=sgn(i)*(Td+Toff_delay-Ton_dela+Tcmp) / Ts*Vdc

[0097] Wherein, ΔV is the output error voltage caused by the dead zone, Td is the fixed value of the dead time of the switching transistor, Ton_delay is the turn-on delay time of the switching transistor, Toff_delay is the turn-off delay time of the switching transistor, Tcmp is the dead zone compensation time, sgn(i) is the sign function of the phase current direction, Ts is the PWM carrier time, and Vdc is the DC bus voltage.

[0098] Ideally, controlling the error voltage to be zero can avoid the nonlinear output of the motor voltage due to dead time. The error voltage can be expressed as the PWM duty cycle output as follows:

[0099] Terr=sgn(i)*(Td+Toff_delay-Ton_delay+Tcmp);

[0100] Terr is proportional to the voltage error ΔV. Therefore, dead zone compensation can be considered from the minimum of the output voltage ΔV. That is, when the speed loop and current loop are working in a steady state, Us_ref (total output voltage vector) should be the same as the actual total output vector Us_fb.

[0101] The dead zone causes an error voltage ΔV = Us_ref - Us_fb, where Vs is the total vector synthesized in the dq-axis rotating coordinate system. This corresponds to Us_ref = sqrt(Ud_ref² + Uq_ref²) in the dq-axis coordinate system. From the motor's rotating voltage equation, we can obtain:

[0102] Ud_ref=r*Id_ref-ω*Lq*Iq_ref;

[0103] Uq_ref=Ke*ω+ω*Id_ref*Ld+r*Iq_ref;

[0104] Because in the linear modulation region (modulation ratio Khv1 < 1.15, within the inscribed circle of the vector hexagon), id is small and Ud accounts for a small proportion, which can be ignored. Therefore, voltage error control of Uq is sufficient.

[0105] △Uq=ω*(Id_ref-Id_fb)*Ld+Ld*(Iq_ref-Iq_fb);

[0106] Therefore, dynamic dead-zone compensation can be performed based on ω and Id / Iq. Because the dq-axis current is controlled in a dual closed-loop manner, the commanded and actual feedback values ​​for the dq-axis are adjusted within a certain error range, while the d-axis error is amplified by the speed ω factor. Therefore, ω is the main influencing factor of the error, and thus, dynamic compensation can be performed on the speed ω.

[0107] From the above formula, we can conclude that the error voltage is related to the difference between the dq current loop and the rotational speed ω. That is, the larger ω is, the larger ΔUq is, and the greater the voltage deviation caused by the ΔV dead zone. Therefore, the larger the error, the larger the dead zone compensation voltage is required. This can be simply equated to the higher ω is, the longer the Tcmp dead zone compensation time is. Therefore, the smaller Terr is, the closer the output voltage is to the ideal output voltage.

[0108] Therefore, in some embodiments of this application, the control unit 101, in addition to the above... Figure 3 In addition to the parts shown, a dead-time compensator (module) is added to eliminate current distortion caused by dead time, thereby reducing motor noise.

[0109] In some embodiments, such as Figure 4 As shown, after the control unit obtains the a-phase current ia, b-phase current ib, and c-phase current ic supplied to the motor (PMSM) by the frequency converter 102, the three-phase currents ia / ib / ic are transformed by Clark to obtain iα and iβ. Then, iα and iβ are transformed by Park to obtain the q-axis feedback current iq (iq_fb) and the d-axis feedback current id (id_fb). Then, iq and id are respectively compared with iq ref and ID ref Calculate the q-axis current error and d-axis current error. Perform a PI integral transformation on the q-axis and d-axis current error values ​​to obtain the DC voltage command value U. d_ref and qc axis voltage command value U q_ref .

[0110] On the one hand, the position observer in the control unit uses iq, id, and U... d_ref and U q_ref Rotor position estimation is performed to determine Δθ (shaft error). Based on the shaft error Δθ output by the position observer, the phase-locked loop obtains the rotor position information, which includes the rotor position θ and angular frequency ω.

[0111] On the other hand, the field weakening control generates the d-axis current increment Δi d After adjustment by a PI controller, it is compared with the given d-axis reference current id. ref Superimposed, and based on the d-axis feedback current i d Generate d-axis voltage command U d_ref q-axis reference current iq ref The rotor's angular frequency ω and ω ref The current is given by the PI controller, and further fed back by the PI controller based on the q-axis feedback current i. q Generate q-axis voltage command U d_ref U d_ref and U q_ref Converted to α / β axis voltage U in stationary coordinates via inverse Park transformation (based on rotor position θ) α_ref and U β_ref Then, the three-phase PWM wave (initial drive signal) driving the frequency converter is generated by SVPWM modulation. The three-phase PWM wave output in terms of PWM duty cycle can be expressed as Ta_ref (the on-time of phase a after SVPWM conversion), Tb_ref ​​(the on-time of phase b after SVPWM conversion), and Tc_ref (the on-time of phase c after SVPWM conversion).

[0112] Simultaneously, the control unit (dead-zone compensator) determines the rotational speed ω based on the set maximum modulation ratio in the linear region. max (Maximum motor speed) corresponds to the maximum dead zone compensation value T dcmp_max Minimum motor speed ω min Corresponding to T dcmp_min Once the rotational speed is ω (angular frequency ω), the dynamic dead zone compensation time (initial dead zone compensation time) can be calculated using the following formula:

[0113] Td cmp =(ω max -ω m i n )*ω / (Td cmp_max -Td cmp_m i n ).

[0114] Among them, Tdcmp is set according to the switching characteristics of IGBT. According to experience, the maximum value of Tdcmp is Td, and it is generally taken as Td / 2.

[0115] After determining the initial dead-zone compensation time, the control unit can determine the dead-zone compensation time based on the three-phase currents ia, ib, and ic of the motor.

[0116] For example, based on the relationship between the magnitude of the three-phase current and a preset value, a compensation coefficient corresponding to the initial dead zone compensation time is determined; the initial dead zone compensation time is processed according to the compensation coefficient to determine the dead zone compensation time.

[0117] For example, the dead time compensation can satisfy the following formula:

[0118] Ta = Ta_ref + Td cmp *sgn(ia);

[0119] Tb = Tb_ref ​​+ Td cmp *sgn(ib);

[0120] Tc = Tc_ref + T dcmp *sgn(ic);

[0121] Where Ta, Tb, and Tc are the on-time of the three phases a, b, and c after dead zone compensation (the dead zone compensation time of the three phases a, b, and c), respectively, and sgn(i) is the sign function of the direction of the phase current (i.e., the compensation coefficient). Taking phase a as an example, when ia>0, sgn(ia)=1, and when ia<0, sgn(ia)=-1.

[0122] When the control unit obtains the initial dead-zone compensation time, it can determine the compensation coefficient (sgn(i)) based on the magnitude relationship between the three-phase current and 0 (to determine the sign of the three-phase current), and obtain the corresponding dead-zone compensation time (T) based on the above formula and the calculated initial dead-zone compensation time. dcmp *sgn(i)).

[0123] The control unit determines the dead-time compensation time (T) dcmp When *sgn(i) is executed, the duty cycle outputs Ta_ref, Tb_ref, and Tc_ref of the three-phase PWM wave generated by SVPWM modulation to drive the frequency converter are compensated according to the above formula and dead-time compensation time, respectively. Finally, the duty cycle outputs Ta, Tb, and Tc of the three-phase PWM wave of the frequency converter are obtained, thereby generating the target drive signal for the frequency converter. The control unit determines the target drive signal of the frequency converter and sends the target drive signal to the frequency converter, so that the frequency converter drives the motor based on the target drive signal.

[0124] In summary, the air conditioner provided in this application embodiment can reduce the nonlinear output of the motor voltage by setting a dead zone compensation time, thereby reducing the noise during motor operation and improving the user experience.

[0125] Based on the above embodiments, this application also provides a method for controlling an air conditioner.

[0126] Figure 5 This is a flowchart illustrating the air conditioning control method provided in an embodiment of this application, as shown below. Figure 5 As shown, it includes:

[0127] S501. Based on the three-phase current of the motor driven by the frequency converter, predict the position information of the motor rotor.

[0128] Optionally, the rotor position information includes the rotor position θ and the angular frequency ω. The prediction of the motor rotor position information can be achieved based on the following method:

[0129] For example, the three-phase current is transformed into a coordinate system to obtain the feedback current of the three-phase current in a rotating coordinate system; based on the feedback current and the reference voltage of the frequency converter, the shaft error Δθ of the motor is predicted; based on the shaft error Δθ, the rotor position θ and the angular frequency ω are predicted.

[0130] S502. Determine the dead-zone compensation time of the frequency converter based on the location information and the three-phase current; the dead-zone compensation time is used to compensate for the current distortion of the three-phase current.

[0131] Optionally, the dead-time compensation time of the frequency converter can be determined in the following manner:

[0132] Obtain the maximum and minimum speeds of the motor; determine the initial dead zone compensation time based on the maximum and minimum speeds and the rotor angular frequency ω; determine the dead zone compensation time based on the initial dead zone compensation time and the three-phase current.

[0133] Optionally, the initial dead-time compensation time can be determined in the following manner:

[0134] Obtain a first difference between the upper limit of dead zone compensation time corresponding to the highest speed and the upper limit of dead zone compensation time corresponding to the lowest speed, and a second difference between the highest speed and the lowest speed; determine the initial dead zone compensation time based on the first difference, the second difference and the angular frequency ω.

[0135] Optionally, the dead-zone compensation time can be determined based on the initial dead-zone compensation time and the three-phase current in the following manner:

[0136] Based on the relationship between the magnitude of the three-phase current and the preset value, the compensation coefficient corresponding to the initial dead zone compensation time is determined; the initial dead zone compensation time is processed according to the compensation coefficient to determine the dead zone compensation time.

[0137] S503. Based on the dead-time compensation time, determine the target drive signal of the frequency converter and send the target drive signal to the frequency converter so that the frequency converter drives the motor based on the target drive signal.

[0138] Optionally, the target drive signal of the frequency converter can be determined in the following manner:

[0139] The initial drive signal of the frequency converter is corrected based on the dead-time compensation time to determine the target drive signal.

[0140] Optionally, the initial drive signal of the frequency converter can be determined based on the following method:

[0141] The reference voltage of the d-axis is determined based on the feedback current and the reference current of the d-axis; the reference voltage of the q-axis is determined based on the feedback current and the reference current of the q-axis, wherein the reference current of the q-axis is determined based on the angular frequency ω and the reference angular frequency.

[0142] Based on the position θ, coordinate transformation is performed on the reference voltage of the d-axis and the reference voltage of the q-axis to obtain the reference voltage of the α-axis and the reference voltage of the β-axis; space vector pulse width modulation is performed on the reference voltage of the α-axis and the reference voltage of the β-axis to obtain the initial drive signal of the frequency converter.

[0143] It should be understood that the specific implementation methods of the steps shown in S501-S503 above are different from those of the steps shown in ... Figure 3 and Figure 4 The specific implementation methods for the corresponding steps are similar, and will not be repeated here.

[0144] refer to Figure 6 The electrical equipment and control method provided in this application embodiment significantly reduce low-frequency noise during operation, with a significant reduction in amplitude from 100Hz to 1.5kHz.

[0145] This application also provides a computer program product, including a computer program that, when executed by a processor, implements the above-described method.

[0146] This application also provides a computer-readable storage medium storing computer-executable instructions, which, when executed by a processor, implement the above-described method.

[0147] The aforementioned readable storage medium can be implemented by any type of volatile or non-volatile storage device or a combination thereof, such as static random access memory (SRAM), electrically erasable programmable read-only memory (EEPROM), erasable programmable read-only memory (EPROM), programmable read-only memory (PROM), read-only memory (ROM), magnetic storage, flash memory, magnetic disk, or optical disk. The readable storage medium can be any available medium accessible to a general-purpose or special-purpose computer.

[0148] An exemplary readable storage medium is coupled to a processor, enabling the processor to read information from and write information to the readable storage medium. Of course, the readable storage medium can also be a component of the processor. The processor and the readable storage medium can reside in an Application Specific Integrated Circuit (ASIC). Alternatively, the processor and the readable storage medium can exist as discrete components in the device.

[0149] The division of units is merely a logical functional division; in actual implementation, there may be other division methods. For example, multiple units or components may be combined or integrated into another system, or some features may be ignored or not executed. Furthermore, the coupling or direct coupling or communication connection shown or discussed may be indirect coupling or communication connection through some interfaces, devices, or units, and may be electrical, mechanical, or other forms.

[0150] The units described as separate components may or may not be physically separate. The components shown as units may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the units can be selected to achieve the purpose of this embodiment according to actual needs.

[0151] In addition, the functional units in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit.

[0152] If a function is implemented as a software functional unit and sold or used as an independent product, it can be stored in a computer-readable storage medium. Based on this understanding, the technical solution of this invention, or the part that contributes to the prior art, or a part of the technical solution, can be embodied in the form of a software product. This computer software product is stored in a storage medium and includes several instructions to cause a computer device (which may be a personal computer, server, or network device, etc.) to execute all or part of the steps of the methods of the various embodiments of this invention. The aforementioned storage medium includes various media capable of storing program code, such as USB flash drives, portable hard drives, read-only memory (ROM), random access memory (RAM), magnetic disks, or optical disks.

[0153] Those skilled in the art will understand that all or part of the steps of the above-described method embodiments can be implemented by hardware related to program instructions. The aforementioned program can be stored in a computer-readable storage medium. When executed, the program performs the steps of the above-described method embodiments; and the aforementioned storage medium includes various media capable of storing program code, such as ROM, RAM, magnetic disks, or optical disks.

[0154] Finally, it should be noted that other embodiments of the invention will readily occur to those skilled in the art upon consideration of the specification and practice of the invention disclosed herein. This invention is intended to cover any variations, uses, or adaptations of the invention that follow the general principles of the invention and include common knowledge or customary techniques in the art not disclosed herein, and is not limited to the precise structures described above and shown in the accompanying drawings, and various modifications and changes can be made without departing from its scope. The scope of the invention is limited only by the appended claims.

Claims

1. An electrical appliance, characterized in that, include: The electric motor is configured to provide a power source; A frequency converter is configured to drive the motor; The control unit connected to the frequency converter is configured to: Based on the three-phase current of the motor driven by the frequency converter, predict the position information of the motor rotor; Based on the location information and the three-phase current, the dead-zone compensation time of the frequency converter is determined; the dead-zone compensation time is used to compensate for the current distortion of the three-phase current. Based on the dead-time compensation time, the target drive signal of the frequency converter is determined and sent to the frequency converter so that the frequency converter drives the motor based on the target drive signal.

2. The electrical equipment according to claim 1, characterized in that, The position information includes the angular frequency ω of the motor rotor, and the control unit is configured to: Obtain the highest and lowest speeds of the motor; The initial dead zone compensation time is determined based on the highest speed, the lowest speed, and the rotor angular frequency ω. The dead zone compensation time is determined based on the initial dead zone compensation time and the three-phase current.

3. The electrical equipment according to claim 2, characterized in that, The control unit is configured to: Obtain a first difference between the upper limit of dead zone compensation time corresponding to the highest speed and the upper limit of dead zone compensation time corresponding to the lowest speed, and a second difference between the highest speed and the lowest speed; The initial dead zone compensation time is determined based on the first difference, the second difference, and the angular frequency ω.

4. The electrical equipment according to claim 3, characterized in that, The control unit is configured to: Based on the relationship between the magnitude of the three-phase current and the preset value, the compensation coefficient corresponding to the initial dead zone compensation time is determined; The initial dead zone compensation time is processed according to the compensation coefficient to determine the dead zone compensation time.

5. The electrical equipment according to any one of claims 1-4, characterized in that, The control unit is configured to: The initial drive signal of the frequency converter is corrected based on the dead-time compensation time to determine the target drive signal.

6. The electrical equipment according to claim 4, characterized in that, The control unit is configured to: The three-phase current is transformed to obtain the feedback current of the three-phase current in the rotating coordinate system; Based on the feedback current and the reference voltage of the frequency converter, the shaft error Δθ of the motor is predicted; Based on the shaft error Δθ, predict the rotor position θ and the angular frequency ω.

7. The electrical equipment according to claim 6, characterized in that, The feedback current includes a d-axis feedback current and a q-axis feedback current, and the control unit is configured to: The reference voltage of the d-axis is determined based on the feedback current of the d-axis and the reference current of the d-axis. The reference voltage of the q-axis is determined based on the feedback current of the q-axis and the reference current of the q-axis, wherein the reference current of the q-axis is determined based on the angular frequency ω and the reference angular frequency.

8. The electrical equipment according to claim 7, characterized in that, The control unit is configured to: Based on the position θ, the reference voltage of the d-axis and the reference voltage of the q-axis are transformed to obtain the reference voltage of the α-axis and the reference voltage of the β-axis. Space vector pulse width modulation is performed on the reference voltages of the α-axis and β-axis to obtain the initial drive signal of the frequency converter.

9. A method for controlling an electrical device, characterized in that, The electrical equipment includes: The electric motor is configured to provide a power source; A frequency converter is configured to drive the motor; The method includes: Based on the three-phase current of the motor driven by the frequency converter, predict the position information of the motor rotor; Based on the location information and the three-phase current, the dead-zone compensation time of the frequency converter is determined; the dead-zone compensation time is used to compensate for the current distortion of the three-phase current. Based on the dead-time compensation time, the target drive signal of the frequency converter is determined and sent to the frequency converter so that the frequency converter drives the motor based on the target drive signal.

10. The control method according to claim 9, characterized in that, The position information includes the angular frequency ω of the motor rotor. Determining the dead-time compensation time of the frequency converter based on the position information and the three-phase current includes: Obtain the highest and lowest speeds of the motor; The initial dead zone compensation time is determined based on the highest speed, the lowest speed, and the rotor angular frequency ω. The dead zone compensation time is determined based on the initial dead zone compensation time and the three-phase current.

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