Electromagnetic heating control system and air conditioner

Abstract

The invention discloses an electromagnetic heating control system and an air conditioner, and the electromagnetic heating control system comprises a frequency conversion topology circuit structure which comprises an inversion unit, a triangular carrier wave and a PWM comparison value, and outputs a three-phase PWM used for controlling a switching tube in the inversion unit, the phase angle corresponding to the interval of the PWM count of the triangular carrier between zero and a PWM period set value is 60 degrees; the control adjusting module is used for simultaneously adjusting the duty ratio of each phase of PWM in the three phases of PWM when the AC motor driven by the inversion unit needs to be heated, so that the adjusted duty ratios of each phase of PWM are the same, and the phase difference of each phase of PWM is still 120 degrees; wherein the period of the PWM of each phase is three times of that of the PWM before adjustment. According to the invention, accurate control of electromagnetic heating is realized by adjusting the PWM comparison value of each phase and adjusting the alternating current component.

Description

Technical Field

[0001] This invention relates to the field of electromagnetic heating technology, and in particular to an electromagnetic heating control system and an air conditioner. Background Technology

[0002] In recent years, the demand for air conditioners has been expanding across various regions, especially in northern areas where air conditioners are used for heating in low winter temperatures. In an air conditioning system, the compressor acts as the power unit, and the viscosity of the refrigerant oil inside the compressor plays a crucial role in its reliability. When the outdoor unit is powered off and left stagnant for an extended period in low outdoor temperatures, due to the miscibility of the lubricating oil and refrigerant, a large amount of refrigerant will accumulate in the compressor crankcase. This leads to a decrease in lubricating oil concentration, failing to meet the compressor's lubrication requirements. Insufficient lubrication hinders the air conditioning system's startup, and the extremely low temperature of motor components at low temperatures can also cause unreliable starting.

[0003] To avoid damaging the compressor, it is necessary to preheat the compressor before starting it to ensure that the lubricating oil meets reliability requirements after the compressor starts.

[0004] Currently, most industries use auxiliary heating, which involves installing an electric heating element inside the compressor or placing it on the outer wall of the compressor cylinder. Before the air conditioner compressor is turned on, the oil sump is preheated by the electric heating element. The compressor is then turned on after the control conditions are met. This increases the overall cost of the machine, results in high heat loss, high energy consumption, low heating efficiency, and a long preheating cycle.

[0005] The information disclosed in this background section is only intended to enhance the understanding of the background technology of this application, and therefore may include prior art that is not known to those skilled in the art. Summary of the Invention

[0006] In response to the problems pointed out in the background art, the present invention provides an electromagnetic heating control system that improves the control accuracy of heating effect by applying an adjustable AC current component to the motor, and meets different heating requirements of the motor by adjusting different AC current components.

[0007] To achieve the above-mentioned objectives, the present invention employs the following technical solution: In some embodiments of this application, an electromagnetic heating control system is provided, comprising: The variable frequency topology circuit structure includes an inverter unit, a triangular carrier wave and a PWM comparison value are compared and output to control the switching transistors in the inverter unit, and the phase angle corresponding to the PWM count of the triangular carrier wave between zero and the PWM period set value is 60 degrees. The control adjustment module is configured to simultaneously adjust the duty cycle of each phase of the three-phase PWM when heating of the AC motor driven by the inverter unit is required, so that the duty cycle of each phase PWM is the same after adjustment, and the phase difference between each phase PWM is still 120 degrees. Before the adjustment, the period of each phase of the PWM was three times the PWM period.

[0008] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: By adjusting the PWM comparison values ​​corresponding to the three-phase PWMs respectively, the duty cycle of each phase of the three-phase PWMs is adjusted to be the same, but the phase difference between each phase of the PWMs is still 120 degrees. At this time, the magnitude of the AC current component can be controlled by adjusting the PWM duty cycle of the three-phase PWMs simultaneously, thereby realizing the control of the AC current component and improving the control accuracy of the electromagnetic heating effect of the motor. It is especially suitable for electromagnetic heating of AC motors with large AC current components, with good heating effect and high control accuracy.

[0009] Furthermore, by adjusting the duty cycle of the three-phase PWM, the magnitude of the AC current component can be changed to meet the different heating requirements of various types of AC motors.

[0010] In some embodiments of this application, the control adjustment module simultaneously adjusts the duty cycle of each phase of the three-phase PWM, specifically: For the triangular carrier corresponding to the high level of each of the three phase PWMs, the comparison value of each phase PWM is adjusted from zero to a non-zero value, so that the output position of the high level rising edge of each phase PWM is shifted backward by angle α1 or forward by angle α2, or the output position of the high level falling edge of each phase PWM is shifted forward by angle α3 or backward by angle α4.

[0011] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: Based on the waveforms of each phase PWM, consider increasing or decreasing the duty cycle of each phase PWM to adjust the AC current component.

[0012] When the output position of each phase PWM is shifted backward by α1 from the rising edge of the high level, the duty cycle of each phase PWM is reduced, thus reducing the AC current component; when the output position of each phase PWM is shifted forward by α3 from the falling edge of the high level, the duty cycle of each phase PWM is reduced, thus also reducing the AC current component.

[0013] When the output position of each phase PWM is shifted forward by α2 from the rising edge of the high level, the duty cycle of each phase PWM is increased, thus increasing the AC current component; when the output position of each phase PWM is shifted backward by α4 from the falling edge of the high level, the duty cycle of each phase PWM is increased, thus also increasing the AC current component.

[0014] In some embodiments of this application, the control adjustment module is further configured to: Obtain the actual alternating current components; Based on the command value corresponding to the AC current component command and the actual AC current component, increase or decrease the duty cycle of each phase PWM so that the actual AC current component is equal to the command value.

[0015] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: Based on the command value corresponding to the AC current component command, the duty cycle of each phase PWM is adjusted to increase or decrease, thereby adjusting the AC current component to meet the different heating requirements of different AC motors using electromagnetic heating.

[0016] In some embodiments of this application, the minimum value of a certain phase AC current component of the corresponding phase PWM is collected by selecting a first position in the triangular carrier that is located before and close to the rising edge of the high level of each phase PWM after adjustment. Select the second position in the triangular carrier that is before and close to the falling edge of the high level of each phase PWM after adjustment, and collect the maximum value of the AC current component of a certain phase of the corresponding phase PWM. The minimum and maximum values ​​of the collected AC current components are used to perform closed-loop control on the AC current components.

[0017] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: To control the AC current component, it is necessary to sample the peak value of the AC current component. Since the motor winding is an inductive load, when the PWM level of a certain phase changes, the winding current of that phase reaches its peak value and changes direction. The winding current reaches its minimum value and starts to increase from small to large at the rising edge of the PWM, and reaches its maximum value and starts to decrease from large to small at the falling edge of the PWM. Therefore, the sampling points of the AC current component should be set at the rising and falling edges of the PWM.

[0018] However, considering that changes in PWM level can cause current ringing and sampling distortion, sampling is performed near the rising and falling edges to ensure accurate sampling of the current signal and improve the control accuracy of the AC current component.

[0019] In some embodiments of this application, the control adjustment module is further configured to: Then adjust the duty cycle of a certain phase PWM to be different from the duty cycles of the remaining two phase PWMs, so that the phase difference between the remaining two phase PWMs is 120 degrees. The phase difference between one phase PWM and the certain phase PWM is greater than 120 degrees, while the phase difference between the other phase PWM and the certain phase PWM is less than 120 degrees.

[0020] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The electromagnetic heating control system involved in this application, after adjusting the AC current component, further adjusts the duty cycle of a certain phase PWM so that the duty cycle of that phase PWM is different from the duty cycles of the other two phase PWMs. In this way, the three-phase voltage is unbalanced, resulting in voltage bias. Then, a DC bias current is superimposed on the adjustable three-phase current, and electromagnetic heating is performed on the motor winding to improve the heating effect.

[0021] In some embodiments of this application, the control adjustment module simultaneously adjusts the duty cycle of each phase of the three-phase PWM, specifically: For the triangular carrier corresponding to the high level of each of the three phase PWMs, the comparison value of each phase PWM is adjusted from zero to a non-zero value, so that the output position of the high level rising edge of each phase PWM is shifted backward by angle α1 or forward by angle α2, or the output position of the high level falling edge of each phase PWM is shifted forward by angle α3 or backward by angle α4.

[0022] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: Based on the waveforms of each phase of the PWM, the adjustment of the AC current component is related to the adjustment of the DC current component. Therefore, the direction of duty cycle adjustment when adjusting the AC current component is explained first, and then the direction of duty cycle adjustment when adjusting the DC current component is determined.

[0023] In some embodiments of this application, after the output position of the high-level rising edge of each phase PWM is shifted backward by an angle α1, the control adjustment module adjusts the duty cycle of a certain phase PWM to be different from the duty cycle of the remaining two phase PWMs, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted backward by an angle γ1. After the output position of each phase PWM is shifted forward by angle α3 on the falling edge of the high level, the control adjustment module adjusts the duty cycle of a certain phase PWM to be different from the duty cycle of the remaining two phase PWMs, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted forward by an angle γ3.

[0024] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: After shifting the output position of each phase PWM by α1 backward from the rising edge of the high level, the output position of a certain phase PWM is then shifted backward by an angle γ1 to further reduce the duty cycle of that phase PWM. As a result, the three-phase voltages are asymmetrical, resulting in voltage bias. This leads to the superposition of a DC bias current on the adjustable three-phase current, which then electromagnetically heats the motor windings.

[0025] After shifting the output position of each phase PWM from the high-level falling edge forward by α3, the output position of a certain phase PWM is then shifted backward by an angle γ3 to further reduce the duty cycle of that phase PWM. As a result, the three-phase voltages are asymmetrical, resulting in voltage bias. This leads to the superposition of a DC bias current on the adjustable three-phase current, which then electromagnetically heats the motor windings.

[0026] In some embodiments of this application, after the output position of the high-level rising edge of each phase PWM is shifted forward by an angle α2, the control adjustment module adjusts the duty cycle of a certain phase PWM to be different from the duty cycle of the remaining two phase PWMs, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted backward by an angle γ2. After the output position of each PWM phase's high-level falling edge is shifted backward by an angle α4, the control adjustment module then adjusts the duty cycle of a certain PWM phase to be different from the duty cycles of the remaining two PWM phases, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted backward by an angle γ4.

[0027] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: After shifting the output position of each phase PWM forward by α2 from the rising edge of the high level, the output position of a certain phase PWM is then shifted forward by an angle γ2 to further increase the duty cycle of that phase PWM. In this way, the three-phase voltage is asymmetrical, resulting in voltage bias. Then, a DC bias current is superimposed on the adjustable three-phase current, which then electromagnetically heats the motor windings.

[0028] After shifting the output position of each phase PWM by α4 from the high-level falling edge, the output position of a certain phase PWM is then shifted backward by an angle γ4 to further increase the duty cycle of that phase PWM. In this way, the three-phase voltage is asymmetrical, resulting in voltage bias. Then, a DC bias current is superimposed on the adjustable three-phase current, which then electromagnetically heats the motor windings.

[0029] In some embodiments of this application, the control adjustment module is further configured to: Obtain the actual DC current component; Based on the instruction value corresponding to the DC current component instruction and the actual DC current component, the duty cycle of the PWM of a certain phase is increased or decreased to make the actual DC-AC current component equal to the instruction value.

[0030] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: In some embodiments of this application, the electromagnetic heating control system generates more heat when the offset angle is greater when adjusting the duty cycle of a certain phase PWM. This allows for closed-loop control of the DC bias current to meet the heating requirements of different motor windings.

[0031] The DC current component command is preset, so the preheating heat can be controlled according to the needs, with flexible control methods and high electromagnetic heating efficiency.

[0032] In some embodiments of this application, the control adjustment module is further configured to: Then, adjust the duty cycle of two of the PWM phases to be different from the duty cycle of the remaining PWM phase, so that the phase difference between the two PWM phases is 120 degrees. The phase difference between one of the two PWM phases and the remaining PWM phase is greater than 120 degrees, while the phase difference between the other PWM phase and the remaining PWM phase is less than 120 degrees.

[0033] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The electromagnetic heating control system involved in this application, after adjusting the AC current component, further adjusts the duty cycle of two phase PWMs. In this way, the rising edge of the high level of the three-phase PWMs no longer maintains a 120-degree relationship, thereby forming a DC current bias, and then electromagnetically heating the motor windings to improve the heating effect.

[0034] Some embodiments of this application also relate to an electromagnetic heating control system, comprising: The variable frequency topology circuit structure includes an inverter unit, a triangular carrier wave and a PWM comparison value are compared and output to control the switching transistors in the inverter unit, and the phase angle corresponding to the PWM count of the triangular carrier wave between zero and the PWM period set value is 60 degrees. The control adjustment module is configured to simultaneously adjust the duty cycle of each phase of the three-phase PWM when heating of the AC motor driven by the inverter unit is required, so that the duty cycle of each phase PWM is the same after adjustment, and the phase difference between each phase PWM is still 120 degrees. Wherein, before adjustment, the period of each phase PWM is three times the PWM period, and the control adjustment module is also configured to execute the first DC bias mode and the second DC bias mode. In the first DC bias mode, the duty cycle of a certain phase PWM is adjusted to be different from the duty cycles of the remaining two phase PWMs, so that the phase difference between the remaining two phase PWMs is 120 degrees. The phase difference between one phase PWM and the certain phase PWM is greater than 120 degrees, while the phase difference between the other phase PWM and the certain phase PWM is less than 120 degrees. In the second DC bias mode, the duty cycle of two of the PWM phases is adjusted to be different from the duty cycle of the remaining PWM phase, so that the phase difference between the two PWM phases is 120 degrees, the phase difference between one of the two PWM phases and the remaining PWM phase is greater than 120 degrees, and the phase difference between the other PWM phase and the remaining PWM phase is less than 120 degrees. The control adjustment module is also configured to: The phase sequence of the three-phase PWM with duty cycle adjustment in the first DC bias mode and the combined phase sequence of the two adjacent phase PWMs with duty cycle adjustment in the second DC bias mode are cyclically switched.

[0035] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: The electromagnetic heating control system disclosed in this application, based on the adjustment of the AC current component, can add a DC bias, and adopts a dual current adjustment method of AC and DC current components to achieve electromagnetic heating, improve the electromagnetic heating effect, and meet the heating needs of various types of motors. Furthermore, the path of the total DC bias current flowing through the switching transistors in the inverter unit under the first DC bias mode is different from the path of the total DC bias current flowing through the switches under the second DC bias mode. By cyclically switching and adjusting the PWM phase sequence of each phase with the duty cycle, the path of the total DC bias current flowing through the switching transistors is changed, ensuring uniform stress and balanced heating on the switching transistors in the inverter unit, and extending the service life of the inverter unit.

[0036] Some embodiments of this application also relate to an air conditioner, comprising: The refrigerant circulation loop allows the refrigerant to circulate in the compressor, condenser, expansion valve, and evaporator. The compressor is driven by an electric motor and is used to compress low-temperature, low-pressure refrigerant gas into high-temperature, high-pressure refrigerant gas and discharge it to the condenser. The variable frequency topology circuit structure includes an inverter unit, a triangular carrier wave and a PWM comparison value are compared and output to control the switching transistors in the inverter unit, and the phase angle corresponding to the PWM count of the triangular carrier wave between zero and the PWM period set value is 60 degrees. The control module is configured to preheat the compressor as follows: At the same time, the duty cycle of each phase PWM in the three-phase PWM is adjusted so that the duty cycle of each phase PWM is the same after adjustment, and the phase difference between each phase PWM is still 120 degrees. Before the adjustment, the period of each phase of the PWM was three times the PWM period.

[0037] The technical solutions involved in the above embodiments have the following advantages or beneficial effects: Some embodiments of this application relate to an air conditioner that adjusts the duty cycle of each phase PWM in the three-phase PWM by adjusting the PWM comparison value corresponding to each phase PWM, thereby controlling the magnitude of the AC current component and improving the control accuracy of the electromagnetic heating effect of the motor.

[0038] An electromagnetic heating control system is used to preheat the compressor electromagnetically before it starts, thereby heating the oil sump and ensuring that the compressor starts normally after the preheating stage is completed.

[0039] Other features and advantages of the present invention will become clearer after reading the detailed embodiments of the invention in conjunction with the accompanying drawings. Attached Figure Description

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0041] Figure 1 A circuit diagram of an existing frequency converter topology; Figure 2 Generate a schematic diagram for PWM; Figure 3 The waveform diagram of the original three-phase PWM generated according to the embodiment; Figure 4The waveform of the three-phase PWM generated according to the embodiment. Figure 1 ; Figure 5 The waveform of the three-phase PWM generated according to the embodiment. Figure 2 ; Figure 6 The waveform of the three-phase PWM generated according to the embodiment. Figure 3 ; Figure 7 The waveform of the three-phase PWM generated according to the embodiment. Figure 4 ; Figure 8 The waveforms of the U-phase current before and after adjusting the AC current component, generated according to the embodiment; Figure 9 This is a schematic diagram illustrating the principle of duty cycle adjustment for V-phase PWM according to an embodiment. Figure 10 for Figure 9 A schematic diagram of the DC bias current path in the inverter topology circuit structure when adjusting the duty cycle of V-phase PWM. Figure 11 This is a schematic diagram of the duty cycle adjustment of V-phase PWM and W-phase PWM according to an embodiment, wherein the AC current component is adjusted. Figure 12 This is a schematic diagram of the DC bias current path in the inverter topology circuit structure when the duty cycle of the V-phase PWM and W-phase PWM is adjusted according to the embodiment. Figure 13 This is a schematic diagram of the electromagnetic control system controlling the inverter unit according to an embodiment. Figure label: 10. AC motor; 20. Inverter unit. Detailed Implementation

[0042] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0043] Variable frequency control of motors (such as permanent magnet synchronous motors and AC motors) is achieved by using a variable frequency topology circuit structure.

[0044] The compressor motor in an air conditioner is generally an AC motor 10. Therefore, the variable frequency topology circuit structure is widely used in air conditioners to adjust the frequency of the compressor motor in the air conditioner.

[0045] See Figure 1 It shows the structure of the frequency conversion topology circuit.

[0046] In some embodiments of this application, the frequency conversion topology circuit structure includes a rectifier unit (not shown) and an inverter unit 20.

[0047] The input terminal of the rectifier unit is connected to the AC power supply. The rectifier unit is used to rectify the AC power supplied by the AC power supply to obtain rectified DC power.

[0048] Inverter unit 20 receives rectified DC power and inverts it into three-phase AC power for use by AC motor 10.

[0049] The rectifier unit can be a single-phase rectifier bridge, which is formed by connecting four rectifier diodes in series.

[0050] Inverter unit 20 is a three-phase power inverter used to invert DC power to drive AC motor 10.

[0051] The three-phase power inverter consists of six switching transistors: T1 for the upper arm of phase U, T3 for the upper arm of phase V, T5 for the upper arm of phase W, T2 for the lower arm of phase U, T4 for the lower arm of phase V, and T6 for the lower arm of phase W.

[0052] The triangular carrier wave is compared with the PWM comparison value and the PWM is output to control the switching transistors in the inverter unit 20.

[0053] The above-described frequency converter topology is merely an example, and the frequency converter topology involved in this application is not limited to the above.

[0054] Variable frequency topology circuits are mostly used in air conditioner outdoor units. The mainstream control algorithm for the compressor motor in the air conditioner outdoor unit is field-oriented control (FOC), also known as vector control.

[0055] FOC control is a conventional technique in motor control, and will not be elaborated upon here.

[0056] This application is concerned with the preheating control of the motor before it is started using FOC control.

[0057] Electromagnetic heating control system Electromagnetic heating, as a highly efficient heating method, is not only widely used in the field of kitchen appliances, but also for starting the compressor in the outdoor unit of an air conditioner under low ambient temperature.

[0058] First, see Figure 2 It illustrates the principle of PWM generation.

[0059] The PWM counting method of the triangular carrier uses an up-down counting mode. That is, it starts counting from the zero value at the trough of the triangular carrier and increases the count until the peak reaches the PWM period set value N. Then it starts counting from the peak back to the zero value at the trough, and so on.

[0060] The time period during which the PWM count increases from zero to the PWM period set value and then decreases back to zero is the carrier period Ts (i.e., the PWM period).

[0061] When the PWM count value is less than the PWM comparison value, the PWM output is low; when the PWM count value is greater than the PWM comparison value, the PWM output is high.

[0062] When the PWM comparison value is the PWM period setting value, the PWM output is always low.

[0063] When the PWM compare value is zero, the PWM output remains high.

[0064] In some embodiments of this application, the period of the three-phase PWM (i.e., U-phase, V-phase, and W-phase) of the motor is first set to three times the PWM period (i.e., the carrier period of the triangular carrier wave), see [link to relevant documentation]. Figure 3 .

[0065] Divide each half-cycle of the PWM into an interval. Thus, the cycle of the three-phase PWM corresponds to six intervals: S1, S2, S3, S4, S5, and S6. Therefore, each interval is 1 / 6 of the cycle of the three-phase PWM (360 degrees), which is 60 degrees.

[0066] That is, when the PWM count value increases from zero to the PWM period set value, it is a range, and the corresponding phase angle is 60 degrees. When the PWM count value decreases from the PWM period set value to zero, it is also a range, and the corresponding phase angle is also 60 degrees.

[0067] See Figure 3 Before the three-phase PWM was adjusted, the rising phase of the high level of the three-phase PWM was 120 degrees apart, the duty cycle of each phase PWM was 50%, and the phase difference between the PWM comparison values ​​of each phase used for modulation was also 120 degrees.

[0068] Adopting such Figure 3 The aforementioned three-phase PWM control Figure 1 The inverter unit 20 generates a three-phase voltage for the motor, which is then applied to the motor windings to form a three-phase AC current. This three-phase AC current is an AC current without added DC bias and without adjustment of the AC current component.

[0069] Pure AC heating belongs to electromagnetic heating. For compressors with small winding inductance and resistance, the AC current component is relatively large, but in the prior art, the magnitude of the AC current component cannot be adjusted, resulting in poor control accuracy of the heating effect.

[0070] In some embodiments of the present application, it is necessary to simultaneously adjust the PWM comparison values of each phase PWM to simultaneously adjust the duty cycles of the three-phase PWM, so that the duty cycles of each phase PWM change equally (increase equally or decrease equally), and keep the rising edge phases of the high levels of the three-phase PWM differ by 120 degrees from each other, to achieve the control of the AC current component, improve the electromagnetic heating effect, and achieve electromagnetic heating control of the motor before the motor starts, thereby ensuring preheating the motor at a low ambient temperature for reliable starting of the motor.

[0071] In some embodiments of the present application, the electromagnetic heating involved belongs to AC heating and aims at controlling the AC current component, and can flexibly control the AC current component to ensure the electromagnetic heating effect.

[0072] In some embodiments of the present application, the electromagnetic control system further involves a control adjustment module (not shown), which is used to simultaneously adjust the duty cycles of each phase PWM in the three-phase PWM.

[0073] Among them, adjusting the duty cycle of each phase PWM includes adjusting to increase the duty cycle of each phase PWM and adjusting to decrease the duty cycle of each phase PWM.

[0074] The control adjustment module adjusts the PWM comparison value corresponding to the high level of each phase PWM, adjusts the PWM comparison value from zero to a non-zero value, so that the high level of the corresponding phase PWM generates a bias angle.

[0075] In some embodiments of the present application, when the rising edge of the high level of the corresponding phase PWM shifts backward by an angle α1 or the falling edge of the high level of the corresponding phase PWM shifts forward by an angle α3, the duty cycle of each phase PWM is reduced.

[0076] In some embodiments of the present application, when the rising edge of the high level of the corresponding phase PWM shifts forward by an angle α3 or the falling edge of the high level of the corresponding phase PWM shifts backward by an angle α4, the duty cycle of each phase PWM is increased.

[0077] In some embodiments of the present application, refer to Figure 4 and Figure 5 , which shows the schematic diagram of reducing the duty cycle of each phase PWM.

[0078] In some embodiments of the present application, in combination with Figure 3 and Figure 4 , in the S1 interval, the PWM comparison value of the U phase is no longer zero, but offsets a certain value △n (0 < △n < PWM period setting value), then the output position of the rising edge of the high level of the U phase PWM is compared with Figure 3Shift backward by an angle α1 from the shown position.

[0079] Similarly, in the S3 interval, the V-phase PWM comparison value is no longer zero and is also offset by a certain value △n. Then, the output position on the rising edge of the V-phase PWM high level is Figure 3 shifted backward by an angle α1 from the shown position; in the S5 interval, the W-phase PWM comparison value is no longer zero and is also offset by a certain value △n. Then, the output position on the rising edge of the W-phase PWM high level is Figure 3 shifted backward by an angle α from the shown position.

[0080] As described above, the phase difference between the rising edges of the three-phase PWM high levels is still 120 degrees and there is no DC offset component. However, the duty cycle of each phase PWM becomes smaller. That is, this adjustment method reduces the AC current component.

[0081] In some embodiments of the present application, still referring to Figure 4 , taking the U-phase PWM as an example, as the U-phase PWM comparison value increases to the PWM period setting value or is no longer zero in the S2 interval, at this time, the output position on the rising edge of the U-phase PWM high level is Figure 3 shifted backward by an angle greater than α1 from the shown position, that is, the AC current component is further reduced.

[0082] Similarly, the V-phase PWM and the W-phase PWM also perform the same corresponding PWM comparison value setting as above.

[0083] In some embodiments of the present application, combining Figure 3 and Figure 5 , taking the adjustment of the U-phase PWM duty cycle as an example, in the S3 interval, the U-phase PWM comparison value is no longer zero but is offset by a certain value PWM period setting value - △n (0 < △n < PWM period setting value). Then, the output position on the falling edge of the U-phase PWM high level is Figure 3 shifted forward by an angle α3 from the shown position.

[0084] Similarly, in the S5 interval, the V-phase PWM comparison value is no longer zero and is also offset by a certain value PWM period setting value - △n. Then, the output position on the falling edge of the V-phase PWM high level is Figure 3 shifted forward by an angle α3 from the shown position; in the S1 interval of the next three-phase PWM period, the W-phase PWM comparison value is no longer zero and is also offset by a certain value PWM period setting value - △n. Then, the output position on the falling edge of the W-phase PWM high level is Figure 3 shifted forward by an angle α3 from the shown position.

[0085] As described above, the phase differences of the falling edges of the high levels of the three-phase PWM are still 120 degrees, without a DC offset component. However, the duty cycle of each phase of the PWM also becomes smaller. That is, this adjustment method also reduces the AC current component.

[0086] It should be noted that when adjusting the duty cycle of each phase of the PWM, the offset angle of each phase of the PWM is the same. That is, the duty cycle of the corresponding phase of the PWM after adjustment is the same.

[0087] In some embodiments of the present application, refer to Figure 6 and Figure 7 , which shows the schematic diagram of increasing the duty cycle of each phase of the PWM.

[0088] In some embodiments of the present application, in combination with Figure 3 and Figure 6 , taking the adjustment of the duty cycle of the U-phase PWM as an example, in the S6 interval of the previous three-phase PWM cycle, the comparison value of the U-phase PWM is no longer zero, but is offset by a certain value △n (0 < △n < PWM cycle setting value). Then, the output position of the rising edge of the high level of the U-phase PWM is shifted forward by an angle α2 compared to the position shown in Figure 3 .

[0089] Similarly, in the S2 interval, the comparison value of the V-phase PWM is also no longer zero, and is also offset by a certain value △n. Then, the output position of the rising edge of the high level of the V-phase PWM is shifted forward by an angle α2 compared to the position shown in Figure 3 ; in the S4 interval, the comparison value of the W-phase PWM is also no longer zero, and is also offset by a certain value △n. Then, the output position of the rising edge of the high level of the W-phase PWM is shifted forward by an angle α2 compared to the position shown in Figure 3 .

[0090] As described above, the phase differences of the rising edges of the high levels of the three-phase PWM are still 120 degrees, without a DC offset component. However, the duty cycle of each phase of the PWM increases. That is, this adjustment method also increases the AC current component.

[0091] In some embodiments of the present application, in combination with Figure 3 and Figure 7 , taking the adjustment of the duty cycle of the U-phase PWM as an example, in the S4 interval, the comparison value of the U-phase PWM is no longer zero, but is offset by a value PWM cycle setting value - △n (0 < △n < PWM cycle setting value). Then, the output position of the falling edge of the high level of the U-phase PWM is shifted backward by an angle α4 compared to the position shown in Figure 3 .

[0092] Similarly, in the S6 interval, the comparison value of the V-phase PWM is also no longer zero, and is also offset by a value PWM cycle setting value - △n. Then, the output position of the falling edge of the high level of the V-phase PWM is shifted backward by an angle compared to the position shown in Figure 3The position shown is shifted backward by an angle α4; in the S2 interval of the next three-phase PWM cycle, the W-phase PWM comparison value is no longer zero, and is also shifted by a certain value, the PWM cycle setting value - Δn. Therefore, the output position of the W-phase PWM high-level falling edge is compared to... Figure 3 The position shown is offset backward by an angle of α4.

[0093] In the above, the phase difference between the rising edges of the high-level three-phase PWM is still 120 degrees, and there is no DC bias component. However, the duty cycle of each phase PWM is also increased, which means that this adjustment method also increases the AC current component.

[0094] As shown above, the AC current component can be adjusted by controlling and adjusting the duty cycle of each phase PWM.

[0095] See Figure 8 It shows a schematic diagram comparing the current before and after the AC current component adjustment.

[0096] The dashed line i1 represents the U-phase AC current obtained by increasing the AC current component, and the solid line i2 represents the U-phase AC current obtained by decreasing the AC current component.

[0097] In some embodiments of this application, in order to achieve closed-loop control of the AC current component, it is necessary to sample the peak value of the AC current.

[0098] See Figures 4 to 7 It shows the sampling locations of the minimum and maximum U-phase currents.

[0099] In some embodiments of this application, since the motor winding is an inductive load, when the PWM level of a certain phase changes, the winding current of that phase reaches its peak value and changes direction. The winding current reaches its minimum value and begins to increase from small to large at the rising edge of the PWM, and the winding current reaches its maximum value and begins to decrease from large to small at the falling edge of the PWM. Therefore, the sampling points should be set at the rising edge and falling edge of the PWM.

[0100] However, since the level changes of PWM can cause current ringing, resulting in distortion when sampling the current at the rising and falling edges of the PWM, the sampling point should be placed before and close to the rising and falling edges of the PWM.

[0101] In some embodiments of this application, taking the U-phase current as an example, the minimum value sampling point is located at the position of the difference between the PWM count corresponding to the rising edge of the U-phase PWM high level and the first time period on the triangular carrier wave. The first time period can be set and should be as small as possible. The maximum value sampling point is located at the position of the difference between the PWM count corresponding to the falling edge of the U-phase PWM high level and the second time period on the triangular carrier wave. The second time period can be set and should be as small as possible.

[0102] In some embodiments of this application, considering the dead time Td and the AD sampling time Tad, the U-phase current is taken as an example, see [link to relevant documentation]. Figure 4 The minimum sampling point is set at Δn-β1, where β1=Td+Tad, and the maximum sampling point is set at the PWM period setting value-β2, where β2=Tad.

[0103] Figures 5 to 7 The minimum and maximum sampling points in the data are also based on Figure 4 The methods provided are similar and will not be repeated here.

[0104] In some embodiments of this application, since pure AC heating has no DC component, the AC current component is small for compressors with large winding inductance and resistance, resulting in poor heating effect. Therefore, in some embodiments of this application, a DC bias current is superimposed on the AC current component to improve the electromagnetic heating effect.

[0105] In some embodiments of this application, the control adjustment module may be configured to execute a first DC bias mode to superimpose a DC bias current onto the AC current component.

[0106] In some embodiments of this application, in the first DC bias mode, the control adjustment module is also used to adjust the duty cycle of a certain phase PWM to be different from the duty cycles of the remaining two phase PWMs, and to adjust the high-level duty cycle of the certain phase PWM so that the phase difference between the three phase PWMs no longer remains at 120 degrees, thereby generating a DC bias current and realizing electromagnetic heating control of the motor windings.

[0107] Adjusting the duty cycle of a certain phase PWM includes increasing the duty cycle of a certain phase PWM and decreasing the duty cycle of a certain phase PWM.

[0108] The control adjustment module adjusts the PWM comparison value corresponding to the high level of a certain phase PWM, changing the PWM comparison value from zero to a non-zero value, thereby causing the high level of that phase PWM to have an offset angle.

[0109] The larger the offset angle γ, the greater the preheating heat.

[0110] In some embodiments of this application, see Figure 9 The following explanation will be based on the example of generating a V-phase DC bias current.

[0111] Combined Figure 4When the rising edge of the high level of each phase PWM is offset backward by an angle α1, the PWM comparison value corresponding to the V phase PWM can be adjusted so that the output position of the rising edge of the high level of the V phase PWM is offset backward by an angle γ1. This results in the phase difference between the rising edge of the high level of the V phase PWM and the rising edge of the high level of the U phase PWM being 120 degrees + γ1, the phase difference between the rising edge of the high level of the W phase PWM and the rising edge of the high level of the V phase PWM being 120 degrees - γ1, and the phase difference between the rising edge of the high level of the W phase PWM and the rising edge of the high level of the U phase PWM remaining at 120 degrees.

[0112] Since the phase difference of the three-phase PWM is no longer maintained at 120 degrees, a DC bias current is generated.

[0113] See Figure 10 The DC bias current passes through the switch T3 of the upper arm of phase V and flows into the switch T2 of the lower arm of phase U and the switch T6 of the lower arm of phase W in inverter unit 20, respectively, and then flows out. That is, the total DC bias current flows through the switch T3 of the upper arm of phase V.

[0114] Similarly, the phase sequence of the three-phase PWM can be changed to generate a U-phase DC bias current or a W-phase DC bias current.

[0115] When the U-phase DC bias current is generated, the DC bias current passes through the switch T1 of the upper bridge arm of the U-phase and flows into the switch T4 of the lower bridge arm of the V-phase and the switch T6 of the lower bridge arm of the W-phase in the inverter unit 20, and then flows out. That is, the total DC bias current flows through the switch T1 of the upper bridge arm of the U-phase.

[0116] When the DC bias current of phase W is generated, the DC bias current passes through the switch T5 of the upper bridge arm of phase W and flows into the switch T2 of the lower bridge arm of phase U and the switch T6 of the lower bridge arm of phase V in inverter unit 20, and then flows out. That is, the total DC bias current flows through the switch T5 of the upper bridge arm of phase W.

[0117] In some embodiments of this application, the generation of V-phase DC bias current is still used as an example for illustration.

[0118] Combination Figure 5 When the output position of the high-level falling edge of each phase PWM is shifted forward by an angle α3, the PWM comparison value corresponding to the V-phase PWM can be adjusted to shift the output position of the high-level falling edge of the V-phase PWM forward by an angle γ3. This results in a phase difference of 120 degrees + γ3 between the high-level falling edge of the V-phase PWM and the high-level falling edge of the W-phase PWM, a phase difference of 120 degrees between the high-level falling edge of the W-phase PWM and the high-level falling edge of the U-phase PWM, and a phase difference of 120 degrees - γ3 between the high-level falling edge of the U-phase PWM and the high-level falling edge of the V-phase PWM, thus generating a DC bias.

[0119] Similarly, the phase sequence of the three-phase PWM can be changed to generate a U-phase DC bias current or a W-phase DC bias current.

[0120] In some embodiments of this application, when the output position of the rising edge of the high level of each phase PWM is shifted forward by an angle α2, the PWM comparison value corresponding to the V phase PWM can be adjusted so that the output position of the rising edge of the high level of the V phase PWM is shifted forward by an angle γ2.

[0121] At this time, the rising edge of the high level of the V-phase PWM is 120 degrees + γ2 out of phase with the rising edge of the high level of the W-phase PWM, the rising edge of the high level of the W-phase PWM is 120 degrees out of phase with the rising edge of the high level of the U-phase PWM, and the falling edge of the high level of the U-phase PWM is 120 degrees - γ2 out of phase with the rising edge of the high level of the V-phase PWM, thus generating DC bias.

[0122] Similarly, the phase sequence of the three-phase PWM can be changed to generate a U-phase DC bias current or a W-phase DC bias current.

[0123] In some embodiments of this application, when the output position of each phase PWM high level falling edge is shifted backward by angle α4, the PWM comparison value corresponding to the V phase PWM can be adjusted so that the output position of the V phase PWM high level falling edge is shifted backward by angle γ4.

[0124] At this time, the falling edge of the high level of the V-phase PWM is 120 degrees - γ4 out of phase with the falling edge of the high level of the W-phase PWM, the falling edge of the high level of the W-phase PWM is 120 degrees out of phase with the falling edge of the high level of the U-phase PWM, and the falling edge of the high level of the U-phase PWM is 120 degrees + γ4 out of phase with the falling edge of the high level of the V-phase PWM, thus generating DC bias.

[0125] Similarly, the phase sequence of the three-phase PWM can be changed to generate a U-phase DC bias current or a W-phase DC bias current.

[0126] The current sampling point method applicable to the control of the AC current component as described above is still suitable for using dual closed-loop control of the current sampling points of both the AC and DC current components.

[0127] Therefore, the actual DC current component is iu+(-iu)≠0.

[0128] In some embodiments of this application, a direct current component command can be given, and the preheating control can be achieved by controlling the magnitude of the direct current component.

[0129] The actual collected DC current component is compared with the command value of the DC current component command.

[0130] If the actual DC current component is less than the command value of the DC current component command, a larger offset angle γ is formed, generating a larger actual DC current component; conversely, it is reduced until the command value requirement of the DC current component command is met.

[0131] The electromagnetic heating control system described above, see [link / reference]. Figure 13 It includes a first single closed loop that controls the AC current component and a second single closed loop that controls the DC current component generated using a first DC bias mode. The outputs of the first and second single closed loops can be superimposed by an adder to drive the switching transistors of the inverter unit 20.

[0132] in, Figure 13 In the second single-loop closed loop, the duty cycle of a certain phase of the biased three-phase PWM is referred to.

[0133] When in use, you can choose to use an independent first single closed loop, a second single closed loop, or a dual closed loop system with a first single closed loop and a second single closed loop to control the AC current component and the DC current component, depending on the actual needs, so as to meet various electromagnetic control requirements and ensure heating effect.

[0134] In the first DC bias mode as described above, the total DC bias current flows through the upper bridge switch of a certain phase.

[0135] As described above, when using dual closed-loop control of AC and DC current components, in order to ensure uniform heating of each phase winding during preheating, the control adjustment module can be configured to perform cyclic switching of the three-phase PWM phase sequence for duty cycle adjustment in the first DC bias.

[0136] For example, when superimposed with DC bias, see Figure 9 First, the rising edge of the high level of the V-phase PWM is shifted backward by an angle γ1. After a period of time, the rising edge of the high level of the W-phase PWM is shifted backward by an angle γ1. After a period of time, the rising edge of the high level of the U-phase PWM is shifted backward by an angle γ1. This cycle is repeated so that the total DC bias current flows sequentially through the switching transistor T3 of the upper bridge arm of the V-phase, the switching transistor T5 of the upper bridge arm of the W-phase, and the switching transistor T1 of the upper bridge arm of the U-phase, thereby achieving uniform thermal stress on the switching transistors of the inverter unit 20.

[0137] In some embodiments of this application, when switching to adjust the duty cycle of a certain phase PWM, the phase sequence can be switched by determining whether the heat generation exceeds the set heat generation.

[0138] The heat generation of the three-phase motor windings is calculated during the adjustment of the duty cycle of the U-phase PWM.

[0139] When the heat generated by the three-phase motor windings exceeds the set heat generation, the phase sequence of the three-phase PWM is switched to adjust the duty cycle of the V-phase PWM.

[0140] The heat generation of the three-phase motor windings is calculated during the adjustment of the duty cycle of the V-phase PWM signal.

[0141] When the heat generated by the three-phase motor windings exceeds the set heat generation, the phase sequence of the three-phase PWM is switched to adjust the duty cycle of the W-phase PWM.

[0142] The heat generation of the three-phase motor windings is calculated during the adjustment of the duty cycle of the W-phase PWM.

[0143] When the heat generated by the three-phase motor windings exceeds the set heat generation, the phase sequence of the three-phase PWM is switched to adjust the duty cycle of the U-phase PWM.

[0144] During the adjustment of the duty cycle of one phase PWM, when the heat generated by the winding exceeds the set heat generation, the phase sequence of the three phase PWM is switched to avoid uneven heating of the three-phase motor windings and ensure the safety of the three-phase motor.

[0145] In some embodiments of this application, the phase sequence can also be switched by setting a duration.

[0146] In some embodiments of this application, the control adjustment module may be configured to execute a second DC bias mode to superimpose a DC bias current onto the AC current component.

[0147] In some embodiments of this application, in the second DC bias mode, the control adjustment module is also used to adjust the duty cycle of two phase PWMs to be different from the duty cycle of the remaining phase PWM, and to adjust the high-level duty cycle of two phase PWMs so that the phase difference between the three phase PWMs no longer remains at 120 degrees, thereby generating a DC bias current and realizing electromagnetic heating control of the motor windings.

[0148] Adjusting the duty cycle of a two-phase PWM includes both increasing the duty cycle of the two-phase PWM and decreasing the duty cycle of the two-phase PWM.

[0149] The control adjustment module adjusts the two-phase PWM comparison value corresponding to the two-phase PWM high level, changing the PWM comparison value from zero to a non-zero value, so that the two-phase PWM high level will generate an offset angle γ.

[0150] The larger the offset angle γ, the greater the preheating heat.

[0151] In some embodiments of this application, see Figure 11 The following explanation will be based on the example of generating DC bias currents for phase V and phase W.

[0152] Combination Figure 4 and Figure 11When the rising edge of the high level of each phase PWM is offset backward by an angle α1, the PWM comparison values ​​corresponding to the V phase PWM and W phase PWM can be adjusted so that the output position of the rising edge of the high level of the V phase PWM is offset backward by an angle γ11 and the output position of the rising edge of the high level of the W phase PWM is offset backward by an angle γ11.

[0153] At this time, the rising edge of the high level of the V-phase PWM is 120 degrees + γ11 out of phase with the rising edge of the high level of the U-phase PWM, the rising edge of the high level of the W-phase PWM is 120 degrees out of phase with the rising edge of the high level of the V-phase PWM, and the rising edge of the high level of the W-phase PWM is 120 degrees - γ11 out of phase with the rising edge of the high level of the U-phase PWM, thus generating a DC bias current.

[0154] See Figure 12 It shows the DC bias current flow path when DC bias current is generated in phases V and W (indicated by arrows). The DC bias current flows out in parallel through the switch T3 of the upper bridge arm of phase V and the switch T5 of the upper bridge arm of phase W, and then flows into the switch T2 of the lower bridge arm of phase U in inverter unit 20, and then flows out. That is, the total DC bias current flows through the switch T2 of the lower bridge arm of phase U.

[0155] The phase sequence of two phases in a three-phase PWM can be changed to generate DC bias currents for the W and U phases, or DC bias currents for the U and V phases.

[0156] The control generates DC bias currents for phase W and phase U. The DC bias current flows out in parallel through the switch T5 of the upper bridge arm of phase W and the switch T1 of the upper bridge arm of phase U, and then flows into the switch T4 of the lower bridge arm of phase V in inverter unit 20, and then flows out. That is, the total DC bias current flows through the switch T4 of the lower bridge arm of phase V.

[0157] The control generates DC bias currents for phase U and phase V. The DC bias current flows out in parallel through the switch T1 of the upper bridge arm of phase U and the switch T5 of the upper bridge arm of phase V, and then flows into the switch T6 of the lower bridge arm of phase W in inverter unit 20, and then flows out. That is, the total DC bias current flows through the switch T6 of the lower bridge arm of phase W.

[0158] In some embodiments of this application, when the output position of the high-level falling edge of each phase PWM is shifted forward by an angle α3, the PWM comparison values ​​corresponding to the V-phase PWM and the W-phase PWM can be adjusted so that the output position of the high-level falling edge of the V-phase PWM is shifted forward by an angle γ13, and the output position of the high-level falling edge of the W-phase PWM is shifted forward by an angle γ13.

[0159] At this time, the falling edge of the high level of the V-phase PWM and the falling edge of the high level of the W-phase PWM are 120 degrees apart in phase, the falling edge of the high level of the W-phase PWM and the falling edge of the high level of the U-phase PWM are 120 degrees + γ13 apart in phase, and the falling edge of the high level of the U-phase PWM and the falling edge of the high level of the V-phase PWM are 120 degrees - γ3 apart in phase, thus generating DC bias.

[0160] The phase sequence of two phases in a three-phase PWM can be changed to generate DC bias currents for the W and U phases, or DC bias currents for the U and V phases.

[0161] In some embodiments of this application, when the output position of the rising edge of the high level of each phase PWM is shifted forward by an angle α2, the PWM comparison values ​​corresponding to the V-phase PWM and the W-phase PWM can be adjusted so that the output position of the rising edge of the high level of the V-phase PWM is shifted forward by an angle γ12, and the output position of the rising edge of the high level of the W-phase PWM is shifted forward by an angle γ12.

[0162] At this time, the rising edge of the high level of the V-phase PWM and the falling edge of the high level of the W-phase PWM are 120 degrees apart in phase, the rising edge of the high level of the W-phase PWM and the falling edge of the high level of the U-phase PWM are 120 degrees + γ12 apart in phase, and the falling edge of the high level of the U-phase PWM and the falling edge of the high level of the V-phase PWM are 120 degrees - γ12 apart in phase, thus generating DC bias.

[0163] The phase sequence of two phases in a three-phase PWM can be changed to generate DC bias currents for the W and U phases, or DC bias currents for the U and V phases.

[0164] In some embodiments of this application, when the output position of the high-level falling edge of each phase PWM is shifted backward by an angle α4, the PWM comparison values ​​corresponding to the V-phase PWM and the W-phase PWM can be adjusted so that the output position of the high-level falling edge of the V-phase PWM is shifted backward by an angle γ14, and the output position of the high-level falling edge of the W-phase PWM is shifted backward by an angle γ14.

[0165] At this time, the falling edge of the high level of the V-phase PWM and the falling edge of the high level of the W-phase PWM are 120 degrees apart in phase, the falling edge of the high level of the W-phase PWM and the falling edge of the high level of the U-phase PWM are 120 degrees - γ4 apart in phase, and the falling edge of the high level of the U-phase PWM and the falling edge of the high level of the V-phase PWM are 120 degrees + γ4 apart in phase, thus generating DC bias.

[0166] The phase sequence of two phases in a three-phase PWM can be changed to generate DC bias currents for the W and U phases, or DC bias currents for the U and V phases.

[0167] The current sampling point method applicable to the control of the AC current component as described above is still suitable for using dual closed-loop control of the current sampling points of both the AC and DC current components.

[0168] Therefore, the actual DC current component is iu+(-iu)≠0.

[0169] The electromagnetic heating control system described above, see also Figure 13 It includes a first single closed loop that controls the AC current component and a third single closed loop that controls the DC current component generated using a second DC bias mode. The outputs of the first and third single closed loops can be superimposed by an adder to drive the inverter unit switching transistors.

[0170] in, Figure 13 In the third single-loop closed loop, the duty cycle of two phases of the biased three-phase PWM is referred to.

[0171] When in use, you can choose to use an independent first single closed loop, a third single closed loop, or a dual closed loop control of the first and third closed loops to control the AC current component and the DC current component, depending on the actual needs, so as to meet a variety of electromagnetic control requirements and ensure the heating effect.

[0172] Compared to the first DC bias mode described above, in the second DC bias mode, the total DC bias current flows through a certain phase lower bridge switch.

[0173] As described above, when using the first and third closed-loop dual-loop control of the AC current component and the DC current component, in order to ensure uniform heating of each phase winding during preheating, the control adjustment module can be configured to execute a combination phase sequence of two adjacent phase PWMs that perform duty cycle adjustment in the second DC bias mode.

[0174] For example, when superimposed with DC bias, see Figure 11 First, the rising edge of the high level of the V-phase PWM and W-phase PWM is shifted backward by an angle γ11. After a period of time, the rising edge of the high level of the W-phase PWM and U-phase PWM is shifted backward by an angle γ11 again. After a period of time, the rising edge of the high level of the U-phase PWM and V-phase PWM is shifted backward by an angle γ11 again. This cycle is repeated so that the total DC bias current flows sequentially through the switch T2 of the lower bridge arm of the U-phase, the switch T4 of the lower bridge arm of the V-phase, and the switch T6 of the upper bridge arm of the W-phase, thereby achieving uniform thermal stress on the switches of the inverter unit.

[0175] In some embodiments of this application, when switching to adjust the duty cycle of a two-phase PWM, the phase sequence can be switched by determining whether the heat generation exceeds the set heat generation.

[0176] The heat generation of the three-phase motor windings is calculated during the adjustment of the duty cycles of the U-phase PWM and V-phase PWM.

[0177] When the heat generated by the three-phase motor windings exceeds the set heat generation, the phase sequence of two adjacent phase PWMs in the three-phase PWM is switched to change the phase sequence, and the duty cycle of the V-phase PWM and W-phase PWM is adjusted.

[0178] The heat generation of the three-phase motor windings is calculated during the adjustment of the duty cycle of the V-phase PWM and W-phase PWM signals.

[0179] When the heat generated by the three-phase motor windings exceeds the set heat generation, the phase sequence of two adjacent phase PWMs in the three-phase PWM is switched to change the phase sequence, and the duty cycle of the W-phase PWM and U-phase PWM is adjusted.

[0180] The heat generation of the three-phase motor windings is calculated during the adjustment of the duty cycle of the W-phase PWM and U-phase PWM.

[0181] When the heat generated by the three-phase motor windings exceeds the set heat generation, the phase sequence of two adjacent phase PWMs in the three-phase PWM is switched to change the phase sequence, and the duty cycle of the U-phase PWM and V-phase PWM is adjusted.

[0182] During the adjustment of the duty cycle of two phase PWMs, when the heat generated by the winding exceeds the set heat generated, the combination phase sequence of two adjacent phase PWMs in the three-phase PWM is switched to avoid uneven heating of the three-phase motor windings and ensure the safety of the three-phase motor.

[0183] In some embodiments of this application, the combined phase sequence can also be switched by setting a duration.

[0184] In some embodiments of this application, the original alternating current component (see...) can be... Figure 3 Based on this, the control adjustment module is configured to execute the second DC bias mode to generate DC bias current and improve the electromagnetic heating effect.

[0185] This method of generating DC bias current is similar to Figure 12 The difference in the method of generating DC bias current shown is that this method does not adjust the AC current component, but only generates DC bias current by executing the second DC bias mode. Figure 12 It involves superimposing a DC bias current on top of the adjustment of the AC current component.

[0186] As described above, the electromagnetic heating control system superimposes a DC bias current onto the original AC current component to improve the electromagnetic heating effect. It is suitable for compressors with large winding inductance and resistance and small AC current components.

[0187] In some embodiments of this application, when in use, the electromagnetic heating control system can be selected according to actual needs, including a first single closed loop for controlling the AC current component as described above, a second single closed loop for controlling the DC current component generated using a first DC bias mode, and a third single closed loop for controlling the DC current component generated using a second DC bias mode.

[0188] In this way, a first single closed loop and a switching execution of the second and third single closed loops can be used. The AC current component is adjusted through the first single closed loop, and the phase sequence of the three-phase PWM with duty cycle adjustment in the second single closed loop and the combined phase sequence of the two adjacent phase PWMs with duty cycle adjustment in the third single closed loop are cyclically switched. This achieves the switching of the total DC bias current flowing through the six switching transistors in the inverter unit 20 on the basis of adjusting the AC current component.

[0189] That is, when the second single closed-loop superimposed DC bias current is used, the total DC bias current circulates through the switch transistor T1 of the upper bridge arm of phase U, the switch transistor T3 of the upper bridge arm of phase V, and the switch transistor T5 of the upper bridge arm of phase W; when the third single closed-loop superimposed DC bias current is used, the total DC bias current circulates through the switch transistor T2 of the lower bridge arm of phase U, the switch transistor T4 of the lower bridge arm of phase V, and the switch transistor T6 of the lower bridge arm of phase W, so that the switches in the inverter unit 20 are heated evenly and the service life of the switches is improved.

[0190] air conditioner This application also relates to an air conditioner that uses the electromagnetic heating control system described above for preheating, and the compressor starts normally after preheating is completed.

[0191] The air conditioner described above includes a refrigerant circulation loop (not shown), a compressor (not shown), an outdoor heat exchanger (not shown), an indoor heat exchanger (not shown), a four-way valve (not shown), and an electromagnetic heating control system as described above.

[0192] The refrigerant circulation loop allows the refrigerant to circulate in the compressor, condenser, expansion valve, and evaporator.

[0193] In the outdoor heat exchanger and the indoor heat exchanger, one functions as a condenser and the other as an evaporator.

[0194] A four-way valve is used to control the refrigerant flow in the refrigerant circulation loop so that the outdoor heat exchanger and the indoor heat exchanger can switch between condenser and evaporator.

[0195] The compressor is driven by an electric motor and is used to compress low-temperature, low-pressure refrigerant gas into high-temperature, high-pressure refrigerant gas and discharge it to the condenser.

[0196] The AC power generated by the frequency converter topology circuit is used to drive the AC motor of the compressor.

[0197] A preheating time (e.g., time T) can be set, and the period within the preheating time is called the preheating stage.

[0198] When the air conditioner needs to be preheated, the electromagnetic heating control system described above is used to preheat it for the specified time, at which point the preheating stage is complete.

[0199] After the preheating phase is completed, the motor is started using the conventional FOC control method.

[0200] An ambient temperature sensor (not shown) can be installed to detect the ambient temperature of the compressor.

[0201] When the ambient temperature is below the preset temperature threshold, the outdoor unit of the air conditioner is considered to be in a low ambient temperature condition.

[0202] Under low ambient temperature conditions, the compressor needs to be preheated before starting to ensure reliable startup; otherwise, compressor preheating is not required.

[0203] Thus, at low ambient temperatures, the compressor is preheated by the electromagnetic heating control system, which can regulate the current component by controlling the DC current component and / or the AC current component, thereby ensuring the efficiency of electromagnetic heating.

[0204] Furthermore, it can set different DC current component commands and / or AC current components based on different ambient temperatures and different motors, and reasonably set the preheating time, thus adapting to different degrees of motor body preheating, and is highly flexible in use.

[0205] Furthermore, this electromagnetic heating control scheme is simple and reliable, and is suitable for applications such as air conditioners.

[0206] In the description of the above embodiments, specific features, structures, materials, or characteristics may be combined in any suitable manner in one or more embodiments or examples.

[0207] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. An electromagnetic heating control system, characterized in that, include: The variable frequency topology circuit structure includes an inverter unit, a triangular carrier wave and a PWM comparison value are compared and output to control the switching transistors in the inverter unit, and the phase angle corresponding to the PWM count of the triangular carrier wave between zero and the PWM period set value is 60 degrees. The control adjustment module is configured to, when heating of the AC motor driven by the inverter unit is required: At the same time, the duty cycle of each phase PWM in the three-phase PWM is adjusted so that the duty cycle of each phase PWM is the same after adjustment, and the phase difference between each phase PWM is still 120 degrees. Before the adjustment, the period of each phase of the PWM was three times the PWM period.

2. The electromagnetic heating control system according to claim 1, characterized in that, The control adjustment module simultaneously adjusts the duty cycle of each phase of the three-phase PWM, specifically: For the triangular carrier corresponding to the high level of each of the three phase PWMs, the comparison value of each phase PWM is adjusted from zero to a non-zero value, so that the output position of the high level rising edge of each phase PWM is shifted backward by angle α1 or forward by angle α2, or the output position of the high level falling edge of each phase PWM is shifted forward by angle α3 or backward by angle α4.

3. The electromagnetic heating control system according to claim 1, characterized in that, The control adjustment module is also configured to: Obtain the actual alternating current components; Based on the command value corresponding to the AC current component command and the actual AC current component, increase or decrease the duty cycle of each phase PWM so that the actual AC current component is equal to the command value.

4. The electromagnetic heating control system according to claim 2, characterized in that, Select the first position in the triangular carrier that is before and close to the rising edge of the high level of each phase PWM after adjustment, and collect the minimum value of a certain phase AC current component of the corresponding phase PWM. Select the second position in the triangular carrier that is before and close to the falling edge of the high level of each phase PWM after adjustment, and collect the maximum value of the AC current component of a certain phase of the corresponding phase PWM. The minimum and maximum values ​​of the collected AC current components are used to perform closed-loop control on the AC current components.

5. The electromagnetic heating control system according to claim 1, characterized in that, The control adjustment module is also configured to: Then adjust the duty cycle of a certain phase PWM to be different from the duty cycles of the remaining two phase PWMs, so that the phase difference between the remaining two phase PWMs is 120 degrees. The phase difference between one phase PWM and the certain phase PWM is greater than 120 degrees, while the phase difference between the other phase PWM and the certain phase PWM is less than 120 degrees.

6. The electromagnetic heating control system according to claim 5, characterized in that, The control adjustment module simultaneously adjusts the duty cycle of each phase of the three-phase PWM, specifically: For the triangular carrier corresponding to the high level of each of the three phase PWMs, the comparison value of each phase PWM is adjusted from zero to a non-zero value, so that the output position of the high level rising edge of each phase PWM is shifted backward by angle α1 or forward by angle α2, or the output position of the high level falling edge of each phase PWM is shifted forward by angle α3 or backward by angle α4.

7. The electromagnetic heating control system according to claim 6, characterized in that, After the output position of the high-level rising edge of each PWM phase is shifted backward by an angle α1, the control adjustment module then adjusts the duty cycle of a certain PWM phase to be different from the duty cycle of the remaining two PWM phases, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted backward by an angle γ1. After the output position of each phase PWM is shifted forward by angle α3 on the falling edge of the high level, the control adjustment module adjusts the duty cycle of a certain phase PWM to be different from the duty cycle of the remaining two phase PWMs, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted forward by an angle γ3. After the output position of the high-level rising edge of each phase PWM is shifted forward by angle α2, the control adjustment module then adjusts the duty cycle of a certain phase PWM to be different from the duty cycle of the remaining two phase PWMs, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted backward by an angle γ2. After the output position of each phase PWM is shifted backward by an angle α4 on the falling edge of the high level, the control adjustment module adjusts the duty cycle of a certain phase PWM to be different from the duty cycle of the remaining two phase PWMs, specifically as follows: For the triangular carrier corresponding to the high level of a certain phase PWM, adjust the PWM comparison value corresponding to the certain phase PWM, so that the output position of the high level rising edge of the certain phase PWM is shifted backward by an angle γ4.

8. The electromagnetic heating control system according to claim 1, characterized in that, The control adjustment module is also configured to: Then, adjust the duty cycle of two of the PWM phases to be different from the duty cycle of the remaining PWM phase, so that the phase difference between the two PWM phases is 120 degrees. The phase difference between one of the two PWM phases and the remaining PWM phase is greater than 120 degrees, while the phase difference between the other PWM phase and the remaining PWM phase is less than 120 degrees.

9. An electromagnetic heating control system, characterized in that, include: The variable frequency topology circuit structure includes an inverter unit, a triangular carrier wave and a PWM comparison value are compared and output to control the switching transistors in the inverter unit, and the phase angle corresponding to the PWM count of the triangular carrier wave between zero and the PWM period set value is 60 degrees. The control adjustment module is configured to simultaneously adjust the duty cycle of each phase of the three-phase PWM when heating of the AC motor driven by the inverter unit is required, so that the duty cycle of each phase PWM is the same after adjustment, and the phase difference between each phase PWM is still 120 degrees. The control adjustment module is also configured to execute a first DC bias mode and a second DC bias mode; In the first DC bias mode, the duty cycle of a certain phase PWM is adjusted to be different from the duty cycles of the remaining two phase PWMs, so that the phase difference between the remaining two phase PWMs is 120 degrees. The phase difference between one phase PWM and the certain phase PWM is greater than 120 degrees, while the phase difference between the other phase PWM and the certain phase PWM is less than 120 degrees. In the second DC bias mode, the duty cycle of two of the PWM phases is adjusted to be different from the duty cycle of the remaining PWM phase, so that the phase difference between the two PWM phases is 120 degrees, the phase difference between one of the two PWM phases and the remaining PWM phase is greater than 120 degrees, and the phase difference between the other PWM phase and the remaining PWM phase is less than 120 degrees. The control adjustment module is further configured to: cyclically switch the phase sequence of the three-phase PWM for duty cycle adjustment in the first DC bias mode and the combined phase sequence of the two adjacent phase PWMs for duty cycle adjustment in the second DC bias mode; Before the adjustment, the period of each phase of the PWM was three times the PWM period.

10. An air conditioner, characterized in that, include: The refrigerant circulation loop allows the refrigerant to circulate in the compressor, condenser, expansion valve, and evaporator. The compressor is driven by an electric motor and is used to compress low-temperature, low-pressure refrigerant gas into high-temperature, high-pressure refrigerant gas and discharge it to the condenser. The variable frequency topology circuit structure includes an inverter unit, a triangular carrier wave and a PWM comparison value are compared and output to control the switching transistors in the inverter unit, and the phase angle corresponding to the PWM count of the triangular carrier wave between zero and the PWM period set value is 60 degrees. The control module is configured to preheat the compressor as follows: At the same time, the duty cycle of each phase PWM in the three-phase PWM is adjusted so that the duty cycle of each phase PWM is the same after adjustment, and the phase difference between each phase PWM is still 120 degrees. Before the adjustment, the period of each phase of the PWM was three times the PWM period.

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