Preheating device and preheating method for compressor

Abstract

The present application provides a preheating device for a compressor, comprising an inverter circuit and a control unit. The inverter circuit includes first, second, and third switching devices. A PWM control module of the control unit outputs first, second, and third PWM output module control signals. The PWM output module of the control unit includes first, second, and third counters, and compares the first, second, and third PWM output module control signals with the first, second, and third count values ​​having triangular waves of the first, second, and third counters, respectively, to generate first, second, and third PWM control signals, respectively, which control the connection and disconnection of the first, second, and third switching devices, respectively, to control the power provided to the corresponding three-phase stator windings of the compressor's motor. At least two of the first, second, and third PWM output module control signals are constant values. The preheating device generates three-phase high-frequency alternating current and two-phase direct current for the motor to improve the preheating effect and reduce noise.

Description

Technical Field

[0001] The present application relates to compressors, and in particular to preheating of compressors. Background Art

[0002] In low ambient temperatures, the lubricating oil in the compressor of an inverter air conditioner will condense, causing the viscosity of the lubricating oil to increase. This increases the starting torque of the compressor when it starts, increases mechanical wear, and can easily cause the compressor to fail to start. Summary of the Invention

[0003] To address this issue, heating the lubricating oil is commonly used to reduce its viscosity. The inventors have observed that one heating method involves installing an electric heating tape on the compressor casing, which heats the compressor casing and then transfers the heat from the compressor casing to the compressor to heat the lubricating oil. This heating method increases the overall cost of the machine, has low heating efficiency, poor heating effect, and takes a long time to heat up.

[0004] The inventors also observed that another heating method involves supplying power to the compressor's permanent magnet motor stator via a variable frequency drive (VFD). One implementation of this heating method involves passing direct current (DC) through the motor's stator windings. This current flowing through the stator winding's resistance generates copper losses, generating heat. This heat is then transferred to the lubricating oil in the compressor. Copper losses are the power consumed by the stator winding's resistance when current passes through it. Since only the stator windings generate heat, the heating power is limited, making it ineffective for high-power compressors with low stator winding resistance. Another implementation of this heating method involves passing alternating current (AC) through the motor's stator windings, generating core losses and eddy current losses. Core losses are losses in the stator core caused by the alternating magnetic field generated by the alternating current in the stator windings. Eddy current losses are losses caused by eddy currents generated in the rotor core and permanent magnets by the stator's alternating magnetic field. The AC power is output using sinusoidal PWM modulation, which limits the AC frequency to a low enough frequency, requiring it to be several times lower than the PWM frequency. This results in suboptimal heating and a certain amount of motor noise.

[0005] In order to solve the above-mentioned problems in the closest prior art, the present application provides a preheating device for a compressor, which outputs a control signal through a control unit to control the connection and disconnection of a switching device, so that the power supply generates a superposition of three-phase high-frequency alternating current and two-phase direct current to the compressor motor, so as to improve the preheating effect of the compressor and reduce or suppress noise.

[0006] According to a first aspect of the present application, a preheating device for a compressor is provided. The compressor includes a motor having three-phase stator windings U, V, and W. The preheating device includes an inverter circuit and a control unit. The inverter circuit is connected to a power supply and includes a first switching device, a second switching device, and a third switching device. The first, second, and third switching devices are respectively connected to the three-phase stator windings U, V, and W and are configured to connect and disconnect to control the power provided by the power supply to the corresponding three-phase stator windings U, V, and W. The control unit is configured to control the connection and disconnection of the first, second, and third switching devices of the inverter circuit. The control unit includes a PWM control module and a PWM output module. The PWM control module is configured to output first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W. The PWM output module includes first, second, and third counters having first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W, respectively. The PWM output module is configured to compare first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W received from the PWM control module with corresponding first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W, respectively, to generate first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W, respectively, to control the connection and disconnection of the first, second, and third switching devices, respectively. The waveforms of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W are triangular waves. At least two of the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W are constant values.

[0007] According to the first aspect of the present application, two of the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W are constant first and second values, respectively, and the remaining one of the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W is one of the first and second values ​​in the rising phase of the triangular wave of the corresponding count value, and is the other of the first and second values ​​in the falling phase of the triangular wave of the corresponding count value.

[0008] According to the first aspect of the present application, two of the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W are alternately selected to be constant at a first value and a second value, respectively. This alternating selection allows DC power to be applied to the three phases U, V, and W in pairs during heating, thereby achieving uniform heating and extending the life of the switching device.

[0009] According to the first aspect of the present application, the triangular waves of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W have the same period and amplitude and are 120° out of phase. Therefore, this solution helps generate symmetrical three-phase alternating current for the motor, generating a rotating magnetic field, thereby improving the heating effect of the compressor.

[0010] According to the first aspect of the present application, the preheating device further comprises a power collection circuit. The power collection circuit is connected to the inverter circuit and is configured to collect the voltage U provided by the power supply to the three-phase stator windings U, V and W. dc and / or current I dc The PWM control module is based on the collected voltage U dc and / or current I dc To update the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W output by the PWM output module, so that the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W output by the PWM output module are updated accordingly. The present application uses a power collection circuit to feed back the voltage and / or current provided by the power supply to the three-phase stator windings U, V, and W to the control unit, so that the control unit can adjust the power provided by the power supply to the three-phase stator windings U, V, and W, thereby improving the preheating effect.

[0011] According to the first aspect of the present application, the PWM control module includes a sampling module, a current reconstruction module, a power calculation module, a regulation module and a comparison module. The sampling module is configured to collect the voltage U dc and / or current I dc Sampling is performed to output the sampled voltage U s and / or the sampled current I s The current reconstruction module is configured based on the sampled current I s Reconstruct the DC current I flowing through the three-phase stator windings U, V, and W u , I v , I w The power calculation module is configured to calculate the power according to the sampled voltage U s and the reconstructed DC current I u , I v , I w To obtain the power P of the three-phase stator windings U, V and W u 、P v 、P w The regulating module is configured to obtain first, second and third regulating values ​​δU, δV, δW respectively based on the received power of the three-phase stator windings U, V and W and the predetermined power. The power of the three-phase stator windings U, V and W includes the sampled voltage U s , reconstructed DC current I u , I v, I w And the power P obtained u 、P v 、P w The comparison module is configured to compare the first, second, and third adjustment values ​​δU, δV, and δW received from the adjustment module with predetermined comparison values ​​to output first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W, respectively. The PWM control module optionally includes a current reconstruction module and a power calculation module.

[0012] According to the first aspect of the present application, the current reconstruction module includes a reconstruction counter. The current reconstruction module is configured to reconstruct the sampled current I s The DC current flowing through one of the three-phase stator windings U, V, and W is obtained. When the DC current obtained by the current reconstruction module is the same as the corresponding DC current obtained by the detection device, the current count value of the reconstruction counter is determined to be a predetermined count value. The reconstruction counter begins counting synchronously with one of the first, second, and third counters corresponding to one of the three-phase stator windings U, V, and W. Through this reconstruction scheme, the present application can accurately obtain the DC current flowing through the three-phase stator winding.

[0013] According to the first aspect of the present application, the regulating module adopts PID regulation to obtain the first, second and third regulating values ​​δU, δV, δW.

[0014] According to the first aspect of the present application, the comparison predetermined value is the first, second and third counters in their 1 / 3 period T PWM The first, second and third PWM control signals PWM_U, PWM_V and PWM_W obtained based on the comparison predetermined value can control the on and off of the first, second and third switching devices to obtain a good compressor preheating effect.

[0015] According to a second aspect of the present application, a preheating method for a compressor is provided, the compressor including a motor having three-phase stator windings U, V, and W. The preheating method includes controlling power supplied by a power supply to the three-phase stator windings U, V, and W of the motor through the aforementioned preheating device. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The drawings are not drawn to scale. In the drawings, each identical or nearly identical component that is represented in different figures is represented by a like reference numeral. For clarity, not every component may be labeled in every figure. In the drawings:

[0017] Figure 1A shows a schematic block diagram of a preheating device according to a first embodiment of the present application;

[0018] Figure 1B shows a schematic block diagram of a preheating device according to a second embodiment of the present application;

[0019] Figure 2 Shown Figure 1A Detailed structural diagram of the preheating device in FIG.

[0020] Figure 3A Shown Figure 1B Detailed structural diagram of the first part of the preheating device (including the power collection circuit);

[0021] Figure 3B Shown Figure 1B Detailed structural diagram of the PWM control module of the preheating device;

[0022] Figure 4A A schematic diagram showing the PWM control waveform output by the PWM output module according to the first embodiment;

[0023] Figure 4B A schematic diagram showing the PWM control waveform output by the PWM output module according to the second embodiment;

[0024] Figure 4C A schematic diagram showing a current waveform generated in the motor;

[0025] Figure 5A A method for preheating a compressor according to an embodiment of the present application is shown;

[0026] Figure 5B A compressor preheating method according to another embodiment of the present application is shown.

[0027] Figure 6 A schematic block diagram of a control unit of a preheating device is shown. DETAILED DESCRIPTION

[0028] The specific embodiments of the present application will be described below with reference to the accompanying drawings of this specification. It should be understood that, where possible, the same or similar reference numerals used in this application refer to the same components.

[0029] Figure 1A : shows a schematic block diagram of a preheating device 100 according to a first embodiment of the present application, Figure 1B FIG2 shows a schematic block diagram of a preheating device 100 according to a second embodiment of the present application, to illustrate the structural components of the preheating device 100 and the relationship between these structures. Figure 1A and Figure 1BAs shown, the preheating device 100 is used to preheat the three-phase stator windings U, V, and W of the motor 103 of the compressor (not shown) to preheat the lubricating oil in the compressor, thereby preventing the compressor from failing to start.

[0030] like Figure 1A As shown, the preheating device 100 includes an inverter circuit 102 and a control unit 106. The inverter circuit 102 is connected to the power supply 101 and includes a first switching device 1021, a second switching device 1022, and a third switching device 1023. The first, second, and third switching devices 1021, 1022, 1023 are respectively connected to the three-phase stator windings U, V, and W of the motor 103. The control unit 106 is configured to control the connection and disconnection of the first, second, and third switching devices 1021, 1022, 1023 in the inverter circuit 102 to control the power provided by the power supply 101 to the corresponding three-phase stator windings U, V, and W. In other embodiments, the preheating device 100 includes the power supply 101.

[0031] The control unit 106 includes a PWM control module 104 and a PWM output module 105. The PWM control module 104 is configured to output first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W to control the operation of the PWM output module 105. The PWM output module 105 includes a first counter 1051, a second counter 1052, and a third counter 1053, each having a first count value Cnt_U, a second count value Cnt_V, and a third count value Cnt_W, respectively. The PWM output module 105 receives the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W from the PWM control module 104 and compares the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W with the corresponding first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W to generate first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W, respectively. The generated first, second and third PWM control signals PWM_U, PWM_V, PWM_W are output to the first, second and third switching devices 1021, 1022, 1023 through connecting lines 111, 112, 113, respectively, to control the connection and disconnection of the first, second and third switching devices 1021, 1022, 1023, respectively, thereby respectively controlling the power provided by the power supply 101 to the corresponding three-phase stator windings U, V and W.

[0032] The waveforms of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W of the first counter 1051, the second counter 1052, and the third counter 1053 are triangular waves. At least two of the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W are constant values. When the constant values ​​of the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W are compared with the triangular waves of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W, respectively, first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W having the same frequencies as the corresponding triangular waves are generated, respectively (see Figure 4A and Figure 4B When the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W are generated to control the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, the power supply 101 can generate three-phase alternating current (AC) of the same frequency as the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W for the three-phase stator windings U, V, and W, that is, generate three-phase high-frequency AC for the three-phase stator windings U, V, and W.

[0033] In the prior art, when using sinusoidal PWM modulation to output a PWM control waveform to a switching device to control the connection and disconnection of the switching device, the frequency of the three-phase alternating current generated for the three-phase stator winding is several times lower than the frequency of the PWM control waveform. The switching device typically operates at a switching frequency below a switching frequency threshold, that is, the switching frequency of the switching device is limited. Therefore, the frequency of the PWM control waveform used to control the connection and disconnection of the switching device is also limited. In other words, in the prior art, the frequency of the three-phase alternating current generated for the three-phase stator winding is several times lower than the frequency of the PWM control waveform, resulting in the generation of low-frequency three-phase alternating current, for example, a frequency of approximately 2-3 kHz. As a result, the preheating effect of the compressor is not ideal, and the motor generates noise.

[0034] Compared to the prior art, the present application enables the power supply 101 to generate three-phase AC power at the same frequency as the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W (which are used to control the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, respectively) for the three-phase stator windings U, V, and W. Therefore, when the switching frequencies of the first, second, and third switching devices 1021, 1022, and 1023 and the frequencies of the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W are limited, the present application can generate higher-frequency three-phase AC power for the three-phase stator windings U, V, and W, thereby improving the preheating effect of the compressor and reducing or suppressing motor noise.

[0035] When two of the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W are constant values, the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W output by the PWM output module 105 can control the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, so that the power supply 101 generates a superposition of three-phase AC power and two-phase DC power having the same frequency as the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W for the three-phase stator windings U, V, and W. The superposition of three-phase high-frequency AC power and two-phase DC power can further improve the preheating effect of the compressor.

[0036] The periods and amplitudes of the triangular waves of the first, second and third count values ​​Cnt_U, Cnt_V and Cnt_W of the present application are the same and have a phase difference of 120° (see Figure 4A and Figure 4B ), thus helping to generate symmetrical three-phase high-frequency alternating current for the three-phase stator windings U, V and W, generating a rotating magnetic field, thereby improving the preheating effect of the compressor.

[0037] Figure 1B The preheating device 100 and Figure 1A The difference is that, as Figure 1B As shown, the preheating device 100 further includes a power collection circuit 107, and the control unit 106 generates first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W based on feedback obtained by the power collection circuit 107 and the received predetermined power. The predetermined power is input by the user or pre-set in the control unit 106.

[0038] like Figure 1B As shown, the power collection circuit 107 is connected to the inverter circuit 102. The power collection circuit 107 collects the power provided by the power supply 101 to the three-phase stator windings U, V and W to output the collected power, for example, the collected voltage U dc and / or current I dc The PWM control module 104 of the control unit 106 receives the collected voltage U from the power collection circuit 107 dc and / or current I dc And receive the predetermined power (including voltage, current and power) input by the user, and based on the received collected U dc and / or I dc And the predetermined power is used to output the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W. When the collected voltage U dcand / or current I dc When updating, the PWM control module 104 updates the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W it outputs accordingly. The PWM output module 105 updates the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W it outputs accordingly based on the updated first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W received from the PWM control module 104 to adjust the control of the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, thereby adjusting the power provided by the power supply 101 to the three-phase stator windings U, V, and W.

[0039] The present application adjusts the first, second and third PWM control signals PWM_U, PWM_V, PWM_W accordingly based on the actual power generated on the three-phase stator winding, and then adjusts the control of the connection and disconnection of the first, second and third switching devices 1021, 1022, 1023, which can improve the preheating operation of the compressor in real time to meet the required preheating.

[0040] Figure 2 Shown Figure 1A Detailed structural diagram of the preheating device 100 is provided to clearly illustrate the various components of the preheating device 100 and the relationship between these components.

[0041] Power 101 (see Figure 1A and Figure 1B ) provides power to the three-phase stator windings U, V, and W of the motor 103 of the compressor (not shown) to achieve preheating of the compressor. In one embodiment, the power supply 101 is configured to output DC power. Figure 2 As shown, the power supply 101 of the preheating device 100 includes an AC power supply source 201 and a rectifier circuit 202. The AC power supply source 201 outputs AC power. The rectifier circuit 202 receives the AC power from the AC power supply source 201 and rectifies the AC power to output DC bus power to the DC bus terminals P and N. In other embodiments, the power supply 101 includes other suitable devices or circuits.

[0042] like Figure 2 As shown, the inverter circuit 102 includes a first capacitor C1 and a second capacitor C2. One end of the first capacitor C1 is connected to the DC bus terminal P, and the other end is connected to one end of the second capacitor C2. The other end of the second capacitor C2 is connected to the DC bus terminal N. The first capacitor C1 and the second capacitor C2 are used to smooth voltage fluctuations and can absorb and release charge to reduce current peaks in the circuit, reducing circuit losses and thereby improving circuit efficiency. In other embodiments, the inverter circuit 102 includes a single capacitor.

[0043] The inverter circuit 102 further includes a first switching device 1021, a second switching device 1022 and a third switching device 1023 (see Figure 1A and Figure 1B ), which constitute a three-phase bridge insulated gate bipolar transistor IGBT module. The first switching device 1021 includes an upper bridge IGBT1 and a lower bridge IGBT2, the second switching device 1022 includes an upper bridge IGBT3 and a lower bridge IGBT4, and the third switching device 1023 includes an upper bridge IGBT5 and a lower bridge IGBT6.

[0044] The collectors of the upper-bridge IGBT1, IGBT3, and IGBT5 are connected to the DC bus P terminal, and the emitters of the lower-bridge IGBT2, IGBT4, and IGBT6 are connected to the DC bus N terminal. The emitter of the upper-bridge IGBT1 is connected to the collector of the lower-bridge IGBT2, and at the junction, they are connected to the stator winding U of the motor 103. The emitter of the upper-bridge IGBT3 is connected to the collector of the lower-bridge IGBT4, and at the junction, they are connected to the stator winding V of the motor 103. The emitter of the upper-bridge IGBT5 is connected to the collector of the lower-bridge IGBT6, and at the junction, they are connected to the stator winding W of the motor 103.

[0045] The first PWM control signal PWM_U generated by the PWM output module 105 is output to the gates of the upper-bridge IGBT1 and the lower-bridge IGBT2 to control the connection and disconnection of the upper-bridge IGBT1 and the lower-bridge IGBT2, thereby controlling the connection and disconnection between the stator winding U of the motor 103 and the AC power supply source 201, thereby controlling the power provided by the AC power supply source 201 to the stator winding U of the motor 103. The second PWM control signal PWM_V generated by the PWM output module 105 is output to the gates of the upper-bridge IGBT3 and the lower-bridge IGBT4 to control the connection and disconnection of the upper-bridge IGBT3 and the lower-bridge IGBT4, thereby controlling the connection and disconnection of the stator winding V of the motor 103 and the AC power supply source 201, thereby controlling the power provided by the AC power supply source 201 to the stator winding V of the motor 103. The third PWM control signal PWM_W generated by the PWM output module 105 is output to the gates of the upper bridge IGBT5 and the lower bridge IGBT6 to control the connection and disconnection of the upper bridge IGBT5 and the lower bridge IGBT6, and control the connection and disconnection between the stator winding W of the motor 103 and the AC power supply source 201, thereby controlling the power provided by the AC power supply source 201 to the stator winding W of the motor 103.

[0046] Figure 3A Shown Figure 1B Detailed structural diagram of the first part of the preheating device 100 (including the power collection circuit 107), Figure 3B Shown Figure 1BDetailed structural diagram of the PWM control module 104 of the preheating device 100 is provided to illustrate in detail the specific structure of the preheating device 100 and the relationship between them.

[0047] Figure 3A Shown with Figure 2 The same AC power supply source 201, rectifier circuit 202, inverter circuit 102 and motor 103. Figure 3A As shown, the preheating device 100 also includes a power collection circuit 107 (see Figure 1B ), which includes a voltage acquisition circuit 301 and a current acquisition circuit 302. The voltage acquisition circuit 301 is configured to acquire the voltage of the three-phase stator windings U, V, and W provided by the power supply 101 (including the AC power supply source 201 and the rectifier circuit 202) to the motor 103, and to generate the acquired voltage U dc Output to PWM control module 104. Current acquisition circuit 302 is configured to acquire the current of three-phase stator windings U, V, W provided by power supply 101 (including AC power supply source 201 and rectifier circuit 202) to motor 103, and to generate the acquired current I dc Output to the PWM control module 104 .

[0048] like Figure 3A As shown, the voltage acquisition circuit 301 includes a first resistor R1 and a second resistor R2. One end of the first resistor R1 is connected to the DC bus terminal P, and the other end of the first resistor R1 is connected to one end of the second resistor R2. The other end of the second resistor R2 is connected to the DC bus terminal N. The first resistor R1 and the second resistor R2 are connected to the PWM control module 104 of the control unit 106 through a connecting line 311 at their connection point (see Figure 1B ), and outputs the collected voltage U to the PWM control module 104 via the connecting line 311 dc The voltage acquisition circuit 301 is a voltage divider circuit, which divides the voltage provided by the power supply 101 to the three-phase stator winding U, V, W of the motor 103 into a voltage suitable for input to the PWM control module 104, that is, the acquired voltage U dc .

[0049] The current acquisition circuit 302 includes a current sensor CT and an operational amplifier 3021. One end of the current sensor CT is connected to the DC bus N terminal, and the other end of the current sensor CT is connected to the emitters of the lower bridge IGBT2, IGBT4, and IGBT6. The current sensor CT detects the current flowing through the three-phase stator windings U, V, and W and outputs the detected current to the operational amplifier 3021. The operational amplifier 3021 amplifies the received current to obtain the collected current I dc , and the collected current I dc The signal is output to the PWM control module 104 via the connection line 311 .

[0050] like Figure 3A As shown, the detection device 308 is connected to the stator winding U to detect the DC current flowing through the stator winding U, so as to obtain the predetermined count value of the reconstruction counter 3041 of the current reconstruction module 304 (see Figure 3B ).

[0051] like Figure 3B As shown, the PWM control module 104 includes a sampling module 303, a current reconstruction module 304, a power calculation module 305, an adjustment module 306 and a comparison module 307. The PWM control module 104 is configured to receive the collected U from the power collection circuit 107. dc and / or I dc And the predetermined power is used to output the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W to control the PWM output module 105 to output the first, second and third PWM control signals PWM_U, PWM_V, PWM_W accordingly, thereby controlling the power provided by the power supply 101 to the three-phase stator windings U, V and W to achieve preheating of the compressor. dc and / or I dc When the PWM control module 104 is updated, the PWM control module 104 collects the updated U dc and / or I dc And predetermined power to update the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W outputted by it, so as to control the PWM output module 105 to update the outputted first, second and third PWM control signals PWM_U, PWM_V, PWM_W accordingly, thereby adjusting the power provided by the power supply 101 to the three-phase stator windings U, V and W, and improving the preheating effect on the compressor.

[0052] like Figure 3B As shown, the sampling module 303 collects power from the power collection circuit 107 (see Figure 3A ) Receive the collected voltage U dc and / or current I dc , and the received collected voltage U dc and / or current I dc Sampling is performed to output the sampled voltage U s and / or the sampled current I s .

[0053] The current reconstruction module 304 receives the sampled current I from the sampling module 303 s , and according to the received sampled current I s Reconstruct the DC current I flowing through the three-phase stator windings U, V and W u , I v, I w The current reconstruction module 304 is used to reconstruct the DC current flowing through one of the three-phase stator windings U, V and W when the DC current and the AC current are superimposed on the three-phase stator windings U, V and W. The current reconstruction module 304 includes a reconstruction counter 3041. At a predetermined count value of the reconstruction counter 3041, the current reconstruction module 304 converts the received sampled current I s The DC current flowing through one of the three-phase stator windings U, V and W is obtained. At the predetermined count value, the control unit 106 triggers its sampling module 303 to collect the DC current from the power collection circuit 107 (see Figure 3A ) The current I received dc Sampling is performed to output the current I s , and then the current reconstruction module 304 receives the current I s As the DC current flowing through one of the three-phase stator windings U, V, and W. The waveform of the reconstruction counter 3041 is the same as the waveform of one of the first, second, and third counters 1051, 1052, and 1053 of the PWM output module 105 corresponding to the one of the three-phase stator windings U, V, and W, and the two counters start counting synchronously. For example, when reconstructing the DC current flowing through the stator winding U, the waveform of the reconstruction counter 3041 is the same as the waveform of the first counter 1051, and the first counter 1051 starts counting synchronously.

[0054] The predetermined count value of the reconstruction counter 3041 is obtained by the detection device 308. When the DC current flowing through one of the three-phase stator windings U, V, and W obtained by the current reconstruction module 304 is the same as the DC current flowing through one of the three-phase stator windings U, V, and W obtained by the detection device 308, the current count value of the reconstruction counter 3041 is determined as the predetermined count value of the reconstruction counter 3041. When two-phase DC power is applied to the stator windings U and V, the detection device 308 is connected to the stator winding U to detect the DC current I flowing through the stator winding U, and the reconstruction counter 3041 obtains the sampled current I from the sampling module 303 at each count value of the reconstruction counter 3041. s When the reconstruction counter 3041 obtains the sampled current I at a count value of the reconstruction counter 3041 s If the count value of the reconstructed counter 3041 is the same as the DC current I obtained by the detection device 308, the count value of the reconstructed counter 3041 is used as the predetermined count value. Once the predetermined count value is determined, it does not need to be re-determined unless the control scheme for providing power to the motor 103 changes. For example, if the predetermined power changes, the control unit 106 changes its control scheme.

[0055] The power calculation module 305 receives the sampled voltage U from the sampling module 303 sand receives the reconstructed DC current I from the current reconstruction module 304 u , I v , I w , and according to the received sampled voltage U s and the reconstructed DC current I u , I v , I w To obtain the power P of the three-phase stator windings U, V and W u 、P v 、P w .

[0056] The adjustment module 306 obtains the first, second and third adjustment values ​​δU, δV and δW respectively based on the received power of the three-phase stator windings U, V and W and the predetermined power. The received power of the three-phase stator windings U, V and W includes the sampled voltage U received from the sampling module 303. s , the reconstructed DC current I received from the current reconstruction module 304 u , I v , I w and the acquired power P received from the regulation module 306 u 、P v 、P w The adjustment module 306 includes a PID adjustment module, which performs PID adjustment on the received power of the three-phase stator windings U, V and W and the predetermined power to obtain the first, second and third adjustment values ​​δU, δV and δW.

[0057] In one embodiment, the power of the three-phase stator windings U, V, and W is the sampled voltage U received from the sampling module 303. s , the predetermined power is a corresponding predetermined voltage. The PWM control module 104 of this embodiment may selectively not include the current reconstruction module 304 and the power calculation module 305. In another embodiment, the power of the three-phase stator windings U, V and W is the reconstructed DC current I received from the current reconstruction module 304. u , I v , I w , the predetermined power is the corresponding predetermined current. The PWM control module 104 of this embodiment may selectively not include the power calculation module 305. In another embodiment, the power of the three-phase stator windings U, V and W is the power P received from the power calculation module 305. u 、P v 、P w The predetermined power may be input to the control unit 106 by a user or may be set in advance in the control unit 106 .

[0058] The comparison module 307 receives the first, second and third adjustment values ​​δU, δV, δW from the adjustment module 306, and compares the received first, second and third adjustment values ​​δU, δV, δW with the comparison predetermined value to output the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W respectively.

[0059] In one embodiment, three-phase alternating current is output to the three-phase stator windings U, V, and W, and direct current is output to the two-phase stator windings U and V, with the direct current sequentially flowing through the stator windings U and V. In this embodiment, each module of the PWM control module 104 obtains parameters corresponding to the stator winding U (including the aforementioned voltage, current, power, adjustment value, and PWM output module control signal) during operation, and obtains parameters corresponding to the stator winding U based on the parameters corresponding to the stator winding U.

[0060] Specifically, the sampled voltage U output by the sampling module 303 is s is the voltage U on the stator winding U u The current reconstruction module 304 reconstructs the DC current I flowing through the stator winding U u The power calculation module 305 is based on the voltage U on the stator winding U u and the DC current I flowing through the stator winding U u Get the power P on the stator winding U u The regulating module 306 is based on the voltage U on the stator winding U u and a predetermined voltage, or based on the DC current I flowing through the stator winding U u and a predetermined current, or based on the power P on the stator winding U u and the predetermined power to obtain the first adjustment value δU. The adjustment module 306 also obtains the second and third adjustment values ​​δV and δW based on the first adjustment value δU. For example, δV = -δU, and in the rising phase of the waveform of the third count value Cnt_W of the third counter 1053 of the PWM output module 105, δW = δU, and in the falling phase of the waveform of the third count value Cnt_W, δW = δV (see Figure 1B and Figure 4B ).

[0061] The comparison module 307 obtains the first, second and third PWM output module control signals Cmp_U, Cmp_V and Cmp_W through the following formulas:

[0062] Cmp_U=Cmp_U0–δU,

[0063] Cmp_V=Cmp_V0–δV,

[0064] Cmp_W=Cmp_W0–δW,

[0065] Among them, Cmp_U0, Cmp_V0, Cmp_W0 are the predetermined comparison values, which are the same as the count values ​​of the first, second and third count values ​​Cnt_U, Cnt_V, Cnt_W of the first, second and third counters 1051, 1052, 1053 of the PWM output module 105 at the time TPWM / 3 of one cycle of the waveform (see Figure 1B and Figure 4B When the count values ​​are the same, the comparison predetermined values ​​Cmp_U0, Cmp_V0, and Cmp_W0 are also the same. Therefore, in the rising phase of the waveform of the third count value Cnt_W, Cmp_W=Cmp_U, and in the falling phase of the waveform of the third count value Cnt_W, Cmp_W=Cmp_V (see Figure 4B ).

[0066] Figure 4A FIG. 1 shows a schematic diagram of the PWM control waveform output by the PWM output module 105 according to the first embodiment. Figure 4B FIG. 1 shows a schematic diagram of the PWM control waveform output by the PWM output module 105 according to the second embodiment. Figure 4C FIG. 1 is a schematic diagram showing a current waveform generated by the motor 103 .

[0067] The PWM output module 105 is configured to compare the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W received from the PWM control module 104 with the corresponding first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W, respectively, to generate first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W, respectively, for controlling the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, respectively, thereby controlling the power supply 101 to output three-phase alternating current to the three-phase stator winding or to output a superposition of three-phase alternating current and two-phase direct current to the three-phase stator winding (see Figure 1A and Figure 1B ). Figure 4A The waveforms of the first, second and third PWM control signals PWM_U, PWM_V and PWM_W (ie, PWM control waveforms) of the first embodiment are shown, which are used to control the power supply 101 to output three-phase AC power to the three-phase stator winding. Figure 4B The waveforms of the first, second and third PWM control signals PWM_U, PWM_V, PWM_W (i.e., PWM control waveforms) of the second embodiment are shown, which are used to control the power supply 101 to output a superposition of three-phase AC power and two-phase (U, V) DC power to the three-phase stator winding.

[0068] like Figure 4AAs shown, the waveform of the first count value Cnt_U is shown in solid form, the waveform of the second count value Cnt_V is shown in dashed form, and the waveform of the third count value Cnt_W is shown in dotted form. The waveforms of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W are all triangular waves, and the periods and amplitudes of these triangular waves are the same and have a phase difference of 120°. The slopes of the rising phase and the falling phase of these triangular waves are the same. The period of the waveforms of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W is T PWM The first, second and third PWM output module control signals Cmp_U, Cmp_V and Cmp_W are constant values, which are consistent with the time T of one cycle of the waveform of the first, second and third count values ​​Cnt_U, Cnt_V and Cnt_W. PWM This solution ensures that the waveforms of the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W are symmetrical and have a phase difference of 120°, thereby generating symmetrical three-phase sinusoidal AC power for the three-phase stator windings and generating a rotating magnetic field, thereby improving the preheating effect of the compressor.

[0069] like Figure 4A As shown, for the first count value Cnt_U and the first PWM output module control signal Cmp_U, at time T0 to T PWM / 3 period (including T0 but excluding T PWM / 3), the first count value Cnt_U is less than the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 is at a low level. PWM / 3, the first count value Cnt_U is equal to the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 changes from low level to high level. PWM / 3~2T PWM / 3 period (excluding T PWM / 3 and 2T PWM / 3), the first count value Cnt_U is greater than the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 is at a high level. PWM / 3, the first count value Cnt_U is equal to the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 changes from a high level to a low level. PWM / 3~T PWM During (excluding 2T PWM / 3 but including TPWM ), the first count value Cnt_U is less than the first PWM output module control signal Cmp_U, and at this time, the first PWM control signal PWM_U generated by the PWM output module 105 is at a low level.

[0070] The waveform of the second count value Cnt_V is 120° out of phase with the waveform of the first count value Cnt_U. PWM / 3, the second count value Cnt_V starts its cycle at time T0 (starting time). Accordingly, the waveform of the second PWM control signal PWM_V is 120 degrees out of phase with the waveform of the first PWM control signal PWM_U. At the time T PWM / 3, the second PWM control signal PWM_V starts one cycle at time T0 (starting time).

[0071] The waveform of the third count value Cnt_W is 120° out of phase with the waveform of the second count value Cnt_V, and is also 120° out of phase with the waveform of the first count value Cnt_U. PWM / 3, the third count value Cnt_W starts its cycle at time T0 (starting time). Accordingly, the waveform of the third PWM control signal PWM_W is 120° out of phase with the waveform of the second PWM control signal PWM_V. At the time T PWM / 3, the third PWM control signal PWM_W starts its cycle at time T0 (starting time). PWM / 3, the third count value Cnt_W starts its cycle at time T0 (starting time). Accordingly, the waveform of the third PWM control signal PWM_W is 120° out of phase with the waveform of the first PWM control signal PWM_U. At time T before one cycle of the first PWM control signal PWM_U PWM / 3, time T0 (starting time) when the third PWM control signal PWM_W starts one cycle.

[0072] The waveforms of the first, second and third PWM control signals PWM_U, PWM_V and PWM_W are all pulse waveforms, and the periods and amplitudes of these pulse waveforms are the same and have a phase difference of 120°. The periods of the waveforms of the first, second and third PWM control signals PWM_U, PWM_V and PWM_W are the same as the periods of the waveforms of the first, second and third count values ​​Cnt_U, Cnt_V and Cnt_W, which are all T PWMThe first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W are used to control the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, respectively, so that the power supply 101 generates three-phase sinusoidal alternating current for the three-phase stator winding. The frequency of the generated three-phase sinusoidal alternating current is the same as the frequency of the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W. Therefore, the present application generates three-phase high-frequency alternating current for the motor 103, improving the preheating effect of the compressor and reducing or suppressing motor noise.

[0073] like Figure 4B As shown, the waveform of the first count value Cnt_U is shown in solid form, the waveform of the second count value Cnt_V is shown in dashed form, and the waveform of the third count value Cnt_W is shown in dotted form. The waveforms of the first count value Cnt_U, the second count value Cnt_V, and the third count value Cnt_W are all triangular waves with the same period and amplitude and a phase difference of 120°. The slope of the rising phase of these triangular waves is the same as the slope of the falling phase. The period of the waveforms of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W is T PWM The first PWM output module control signal Cmp_U is a constant first value, and the second PWM output module control signal Cmp_V is a constant second value. During the rising phase of the waveform of the third count value Cnt_W, Cmp_W = Cmp_U, and during the falling phase of the waveform of the third count value Cnt_W, Cmp_W = Cmp_V. This embodiment outputs three-phase alternating current to the three-phase stator windings U, V, and W and direct current to the two-phase stator windings U and V. For example, direct current flows through the stator windings U and V sequentially.

[0074] To achieve uniform heating and extend the life of the IGBT switches, the compressor is preheated by rotating the three-phase DC power output, U, V, and W, in pairs. For example, this rotation can be achieved in the following three ways: DC current flows sequentially through stator windings U and V, DC current flows sequentially through stator windings V and W, and DC current flows sequentially through stator windings W and U. In other embodiments, other suitable methods can be used to rotate DC power through the three-phase stator windings in pairs.

[0075] As mentioned above, the first, second and third PWM output module control signals Cmp_U, Cmp_V and Cmp_W are obtained by the following formulas:

[0076] Cmp_U=Cmp_U0–δU,

[0077] Cmp_V=Cmp_V0–δV,

[0078] Cmp_W=Cmp_W0–δW,

[0079] Cmp_U0, Cmp_V0, and Cmp_W0 are the count values ​​at time TPWM / 3 of one cycle of the waveforms of the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W, and these count values ​​are identical. When DC power is output to the two-phase stator windings U and V, for example, the DC current flows sequentially through the stator windings U and V, and δV = -δU. Therefore, the first and second PWM output module control signals Cmp_U and Cmp_V are symmetrical with respect to the count values ​​at time TPWM / 3. During the rising phase of the waveform of the third count value Cnt_W, δW = δU, and during the falling phase of the waveform of the third count value Cnt_W, δW = δV. Therefore, during the rising phase of the waveform of the third count value Cnt_W, δW = δU, and Cmp_W = Cmp_U, while during the falling phase of the waveform of the third count value Cnt_W, Cmp_W = Cmp_V. The first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W are compared with the first, second and third count values ​​Cnt_U, Cnt_V, Cnt_W with a waveform phase difference of 120° to obtain the first, second and third PWM control signals PWM_U, PWM_V, PWM_W, which can generate symmetrical three-phase alternating current for the three-phase stator winding and generate a rotating magnetic field, thereby improving the preheating effect of the compressor.

[0080] like Figure 4B As shown, for the first count value Cnt_U and the first PWM output module control signal Cmp_U, at time T U0 ~T U1 Period (including T U0 But not including T U1 ), the first count value Cnt_U is less than the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 is at a low level. U1 , the first count value Cnt_U is equal to the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 changes from a low level to a high level. U1 ~T U2 Period (excluding T U1 and T U2 ), the first count value Cnt_U is greater than the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 is at a high level. U2, the first count value Cnt_U is equal to the first PWM output module control signal Cmp_U, and the first PWM control signal PWM_U generated by the PWM output module 105 changes from a high level to a low level. U2 ~T UPWM Period (excluding T U2 But including T UPWM ), the first count value Cnt_U is less than the first PWM output module control signal Cmp_U, and at this time, the first PWM control signal PWM_U generated by the PWM output module 105 is at a low level.

[0081] The phase of the waveform of the second count value Cnt_V is 120° different from the phase of the waveform of the first count value Cnt_U. UPWM / 3, the second count value Cnt_V starts its T cycle V0 For the second count value Cnt_V and the second PWM output module control signal Cmp_V, at time T V0 ~T V1 Period (including T V0 But not including T V1 ), the second count value Cnt_V is less than the second PWM output module control signal Cmp_V, and the second PWM control signal PWM_V generated by the PWM output module 105 is at a low level. V1 , the second count value Cnt_V is equal to the second PWM output module control signal Cmp_V, and the second PWM control signal PWM_V generated by the PWM output module 105 changes from a low level to a high level. V1 ~T V2 Period (excluding T V1 and T V2 ), the second count value Cnt_V is greater than the second PWM output module control signal Cmp_V, and the second PWM control signal PWM_V generated by the PWM output module 105 is at a high level. V2 , the second count value Cnt_V is equal to the second PWM output module control signal Cmp_V, and the second PWM control signal PWM_V generated by the PWM output module 105 changes from a high level to a low level. V2 ~T VPWM Period (excluding T V2 But including T VPWM ), the second count value Cnt_V is less than the second PWM output module control signal Cmp_V, and the second PWM control signal PWM_V generated by the PWM output module 105 is at a low level. V1The time T of the first count value Cnt_U U2 same.

[0082] The phase of the waveform of the third count value Cnt_W is 120° different from the phase of the waveform of the second count value Cnt_V. VPWM / 3, the third count value Cnt_W starts its T cycle W0 For the third count value Cnt_W and the third PWM output module control signal Cmp_W, at time T W0 ~T W1 Period (including T W0 But not including T W1 ), the third count value Cnt_W is less than the third PWM output module control signal Cmp_W, and the third PWM control signal PWM_W generated by the PWM output module 105 is at a low level. W1 , the third count value Cnt_W is equal to the third PWM output module control signal Cmp_W, and the third PWM control signal PWM_W generated by the PWM output module 105 changes from a low level to a high level. W1 ~T W2 Period (excluding T W1 and T W2 ), the third count value Cnt_W is greater than the third PWM output module control signal Cmp_W, and the third PWM control signal PWM_W generated by the PWM output module 105 is at a high level. W2 , the third count value Cnt_W is equal to the third PWM output module control signal Cmp_W, and the third PWM control signal PWM_W generated by the PWM output module 105 changes from a high level to a low level. W2 ~T WPWM Period (excluding T W2 But including T WPWM ), the third count value Cnt_W is less than the third PWM output module control signal Cmp_W, and the third PWM control signal PWM_W generated by the PWM output module 105 is at a low level. The moment T of the third count value Cnt_W W1 The time T of the second count value Cnt_V V2 The same, and the time T of the third count value Cnt_W W2 The time T of the next cycle of the first count value Cnt_U U1 same.

[0083] In one embodiment, the PWM control module 104 is based on the collected U received from the power collection circuit 107. dc and / or I dcand predetermined power to output the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W (see Figure 1B ). When the collected U dc and / or I dc When the PWM control module 104 is updated, the PWM control module 104 collects the updated U dc and / or I dc and a predetermined power to update the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W outputted by the module. At this time, the first PWM output module control signal Cmp_U is updated to a new constant first value, and the second PWM output module control signal Cmp_V is updated to a new constant second value. Before the next update, the current first and second values ​​remain constant until the next update generates a new first and second value. In one embodiment, each update is separated by a period T PWM or 2T PWM The updated first, second and third PWM output module control signals Cmp_U, Cmp_V and Cmp_W are used to control the PWM output module 105 to update the output first, second and third PWM control signals PWM_U, PWM_V and PWM_W accordingly, thereby adjusting the power provided by the power supply 101 to the three-phase stator winding. Figure 4B As shown, when the first PWM output module control signal Cmp_U decreases, the duty cycle of the first PWM control signal PWM_U increases accordingly, as indicated by the arrow on the first PWM control signal PWM_U. When the first PWM output module control signal Cmp_U decreases, the second PWM output module control signal Cmp_V increases accordingly, and the duty cycle of the second PWM control signal PWM_V decreases accordingly, as indicated by the arrow on the second PWM control signal PWM_V. The duty cycle of the third PWM control signal PWM_W remains unchanged. In other embodiments, the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W and the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W may not be updated.

[0084] like Figure 4C As shown, the first, second and third PWM control signals PWM_U, PWM_V and PWM_W output by the PWM output module 105 control the connection and disconnection of the first, second and third switching devices 1021, 1022 and 1023 (see Figure 1A and Figure 1B), a superposition of DC current and AC current is generated in the stator windings U and V of the motor 103, generating an AC current in the stator winding W of the motor 103. The DC current in the stator winding U and the DC current generated in the stator winding V are of the same magnitude but opposite directions. That is, the power supply 101 generates two-phase DC current and three-phase AC current in the motor. Figure 4C The ordinate shows the amplitude of the current. The DC current on the stator windings U and V is approximately 9A. Figure 4C The horizontal axis shows time, and the current waveform shows a time length of 0 to 5x10 -3 s waveforms, where the period of these waveforms is approximately 1 / 16x10 -3 s, the frequency is about 16KHZ. This frequency is close to the upper limit of audible sound frequency, so it can reduce noise.

[0085] Figure 5A FIG. 5 shows a method 500 for preheating a compressor according to an embodiment of the present application. Figure 5B A compressor preheating method 500 according to another embodiment of the present application is shown. The preheating method 500 controls the power provided by the power supply 101 to the three-phase stator windings U, V and W of the motor through the preheating device 100 to achieve preheating of the compressor.

[0086] like Figure 5A As shown, the compressor preheating method 500 begins with step 501 and then proceeds to step 502. In step 502, the PWM control module 104 of the control unit 106 generates first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W. Then, the process proceeds from step 502 to step 503.

[0087] In step 503, the PWM output module 105 of the control unit 106 receives the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W from the PWM control module 104. The first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W are compared with the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W, respectively, to output the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W, respectively. The process then proceeds from step 503 to step 504.

[0088] In step 504, the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W are used to control the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, respectively, so that the power supply 101 generates the required power, for example, a superposition of DC and AC currents, for the three-phase stator windings U, V, and W of the motor 103. The process then proceeds from step 504 to step 505, terminating the execution of the preheating method 500.

[0089] like Figure 5B As shown, the compressor preheating method 500 starts from step 511 and then goes to step 512. In step 512, the voltage U provided by the power supply 101 to the three-phase stator windings U, V and W is collected by the power collection circuit 107. dc and / or current I dc Then, go from step 512 to step 513.

[0090] In step 513, the sampling module 303 receives the collected voltage U from the power collection circuit 107. dc and / or current I dc , and the received collected voltage U dc and / or current I dc Sampling is performed to output the sampled voltage U s and / or the sampled current I s Then, go from step 513 to step 514.

[0091] In step 514, the current reconstruction module 304 receives the sampled current I from the sampling module 303. s , and according to the received sampled current I s Reconstruct the DC current I flowing through the three-phase stator windings U, V and W u , I v , I w Then, go from step 514 to step 515.

[0092] In step 515, the power calculation module 305 receives the sampled voltage U from the sampling module 303. s and receives the reconstructed DC current I from the current reconstruction module 304 u , I v , I w , and according to the received sampled voltage U s and the reconstructed DC current I u , I v , I w To obtain the power P of the three-phase stator windings U, V and W u 、P v 、P wThen, the process proceeds from step 515 to step 516 . The preheating method 500 may optionally include steps 514 and 515 .

[0093] In step 516, the first, second and third adjustment values ​​δU, δV and δW are respectively obtained by the adjustment module 306 based on the received power of the three-phase stator windings U, V and W and the predetermined power. The received power of the three-phase stator windings U, V and W includes the sampled voltage U received from the sampling module 303. s , the reconstructed DC current I received from the current reconstruction module 304 u , I v , I w and the acquired power P received from the regulation module 306 u 、P v 、P w Then, go to step 517 from step 516.

[0094] In step 517, the first, second, and third adjustment values ​​δU, δV, and δW are received from the adjustment module 306 via the comparison module 307. The received first, second, and third adjustment values ​​δU, δV, and δW are compared with a predetermined comparison value to output the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W, respectively. Then, the process proceeds from step 517 to step 518.

[0095] In step 518, the PWM output module 105 receives the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W from the comparison module 307, and compares the first, second, and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W with the first, second, and third count values ​​Cnt_U, Cnt_V, and Cnt_W, respectively, to output the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W, respectively. The process then proceeds from step 518 to step 519.

[0096] In step 519, the first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W are used to control the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, respectively, so that the power supply 101 generates the required power, for example, a superposition of DC and AC currents, for the three-phase stator windings U, V, and W of the motor 103. The process then proceeds from step 519 to step 520, terminating the execution of the preheating method 500.

[0097] Figure 6 A schematic block diagram of the control unit 106 of the preheating device 100 is shown.

[0098] like Figure 6 As shown, the control device 106 includes a bus 601, a processor 602, a memory 603, an input interface 604, and an output interface 605. The processor 602, the memory 603, the input interface 604, and the output interface 605 are connected to the bus 601. The processor 602 can read a program (or instruction) from the memory 603 and execute the program (or instruction) to process data and perform operations on the inverter circuit 102 (see FIG. Figure 1A and Figure 1B ) control functions. The processor 602 may also write data or programs (or instructions) into the memory 603. The memory 603 may store programs (instructions) or data. By executing instructions in the memory 603, the processor 602 may control the memory 603, the input interface 604, and the output interface 605.

[0099] In one embodiment, the input interface 604 is configured to receive the voltage U from the power collection circuit 107 via the connection line 311. dc , receives the current I from the power collection circuit 107 through the connecting line 312 dc , and receives a predetermined power input from the user through the connection line 313. The input interface 604 is also configured to convert the received voltage U dc , current I dc and predetermined power into a signal recognizable by the processor 602, and output the signal to the processor 602. The processor 602 is configured to process (e.g., calculate) the received signal to output a control signal for the first switching device 1021, a control signal for the second switching device 1022, and a control signal for the third switching device 1023.

[0100] The output interface 605 is configured to receive the control signals for the first, second, and third switching devices 1021, 1022, and 1023 from the processor 602 and convert these control signals into a first PWM control signal PWM_U for the first switching device 1021, a second PWM control signal PWM_V for the second switching device 1022, and a third PWM control signal PWM_W for the third switching device 1023. The output interface 605 is further configured to send the first PWM control signal PWM_U to the first switching device 1021 via the connection line 111, send the second PWM control signal PWM_V to the second switching device 1022 via the connection line 112, and send the third PWM control signal PWM_W to the third switching device 1023 via the connection line 113. The first, second, and third PWM control signals PWM_U, PWM_V, and PWM_W respectively control the connection and disconnection of the first, second, and third switching devices 1021, 1022, and 1023, thereby controlling the power 101 provides to the motor 103 (see FIG. 1 ). Figure 1B) to preheat the compressor (not shown).

[0101] In another embodiment, the input interface 604 does not receive the voltage U from the power collection circuit 107. dc and current I dc The input interface 604 receives a predetermined power input from a user through the connection line 313, converts the received predetermined power into a signal recognizable by the processor 602, and outputs the signal to the processor 602. The processor 602 reads a program (or instruction) from the memory 603 and executes the program (or instruction) to process (e.g., calculate) the received signal, thereby outputting a control signal for the first switching device 1021, a control signal for the second switching device 1022, and a control signal for the third switching device 1023. Other operations in this other embodiment are the same as those in the aforementioned embodiment.

[0102] Although the present application has been described in conjunction with the examples of the embodiments outlined above, it is likely that various alternatives, modifications, variations, improvements and / or substantial equivalents, whether known or currently or soon foreseeable, will be apparent to those skilled in the art. In addition, the technical effects and / or technical problems described in this specification are exemplary and not restrictive; so the disclosures in this specification may be used to solve other technical problems and have other technical effects and / or may solve other technical problems. Therefore, the examples of the embodiments of the present application as stated above are intended to be illustrative and not restrictive. Various changes may be made without departing from the spirit or scope of the present application. Therefore, the present application is intended to include all known or earlier developed alternatives, modifications, variations, improvements and / or substantial equivalents.

Claims

1. A preheating device (100) for a compressor, the compressor comprising a motor (103) having three-phase stator windings U, V and W, characterized in that: The preheating device (100) comprises: an inverter circuit (102) connected to a power source (101) and comprising a first switching device, a second switching device, and a third switching device (1021, 1022, 1023), wherein the first, second, and third switching devices (1021, 1022, 1023) are respectively connected to three-phase stator windings U, V, and W, and are configured to be connected and disconnected to respectively control the power provided by the power source (101) to the corresponding three-phase stator windings U, V, and W; and A control unit (106) configured to control the connection and disconnection of the first, second and third switching devices (1021, 1022, 1023) of the inverter circuit (102), the control unit (106) comprising: A PWM control module (104) configured to output first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W; and A PWM output module (105) comprising first, second and third counters (1051, 1052, 1053) having first, second and third count values ​​Cnt_U, Cnt_V, Cnt_W, respectively, the PWM output module (105) being configured to compare the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W received from the PWM control module (104) with the corresponding first, second and third count values ​​Cnt_U, Cnt_V, Cnt_W, respectively, to generate first, second and third PWM control signals PWM_U, PWM_V, PWM_W, respectively, which control the connection and disconnection of the first, second and third switching devices (1021, 1022, 1023), respectively. The waveforms of the first, second and third count values ​​Cnt_U, Cnt_V and Cnt_W are triangular waves; and At least two of the first, second and third PWM output module control signals Cmp_U, Cmp_V and Cmp_W are constant values.

2. The preheating device (100) for a compressor according to claim 1, characterized in that: Two of the first, second and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W are constant first and second values, respectively; the remaining one of the first, second and third PWM output module control signals Cmp_U, Cmp_V, and Cmp_W is one of the first and second values ​​in the rising phase of the triangular wave of the corresponding count value, and is the other of the first and second values ​​in the falling phase of the triangular wave of the corresponding count value.

3. The preheating device (100) for a compressor according to claim 2, characterized in that: Two of the first, second and third PWM output module control signals Cmp_U, Cmp_V and Cmp_W are selected in turn to be constant first and second values, respectively.

4. The preheating device (100) for a compressor according to claim 1, characterized in that The triangular waves of the first, second and third count values ​​Cnt_U, Cnt_V and Cnt_W have the same period and amplitude and a phase difference of 120°.

5. The preheating device (100) for a compressor according to claim 1, characterized in that: The preheating device (100) further comprises: A power collection circuit (107; 301, 302) is connected to the inverter circuit (102) and is configured to collect the voltage U provided by the power supply (101) to the three-phase stator windings U, V and W. dc and / or current I dc , Wherein, the PWM control module (104) is based on the collected voltage U dc and / or current I dc To update the first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W outputted by it, so that the PWM output module (105) updates the first, second and third PWM control signals PWM_U, PWM_V, PWM_W outputted by it accordingly.

6. The preheating device (100) for a compressor according to claim 5, characterized in that: The PWM control module (104) includes: The sampling module (303) is configured to collect the voltage U dc and / or current I dc Sampling is performed to output the sampled voltage U s and / or the sampled current I s ; A current reconstruction module (304) is configured to reconstruct the current I s Reconstruct the DC current I flowing through the three-phase stator windings U, V, and W u , I v , I w ; The power calculation module (305) is configured to calculate the power of the sampled voltage U s and the reconstructed DC current I u , I v , I w To obtain the power P of the three-phase stator windings U, V and W u 、P v 、P w ; A regulating module (306) is configured to obtain first, second and third regulating values ​​δU, δV, δW respectively based on the received power of the three-phase stator windings U, V and W and the predetermined power, wherein the power of the three-phase stator windings U, V and W includes the sampled voltage U s , the reconstructed DC current I u , I v , I w and the obtained power P u 、P v 、P w ;as well as A comparison module (307) is configured to compare the first, second and third adjustment values ​​δU, δV, δW received from the adjustment module (306) with a predetermined comparison value to output first, second and third PWM output module control signals Cmp_U, Cmp_V, Cmp_W, respectively. Wherein, the PWM control module (104) selectively includes the current reconstruction module (304) and the power calculation module (305).

7. The preheating device (100) for a compressor according to claim 6, characterized in that: The current reconstruction module (304) includes a reconstruction counter (3041) and is configured to convert the sampled current I s is obtained as the DC current flowing through one of the three-phase stator windings U, V and W, wherein, when the DC current acquired by the current reconstruction module (304) is the same as the corresponding DC current acquired by the detection device (308), the current count value of the reconstruction counter (3041) is determined as the predetermined count value; and The reconstruction counter (3041) starts counting in synchronization with one of the first, second and third counters (1051, 1052, 1053) corresponding to one of the three-phase stator windings U, V and W.

8. The preheating device (100) for a compressor according to claim 6, characterized in that: The regulating module (306) adopts PID regulation to obtain the first, second and third regulating values ​​δU, δV, δW.

9. The preheating device (100) for a compressor according to claim 6, characterized in that: The comparison predetermined value is the first, second and third counters (1051, 1052, 1053) at their 1 / 3 period T PWM The count value at time / 3.

10. A preheating method for a compressor comprising a motor (103) having three-phase stator windings U, V and W, characterized in that The method comprises: The preheating device (100) according to any one of claims 1 to 9 controls the power supplied by the power supply (101) to the three-phase stator windings U, V and W of the motor (103).

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