Compressor driving system and air conditioning equipment

Abstract

The invention discloses a compressor driving system and air conditioning equipment, the compressor driving system comprises a frequency converter, the output end of the frequency converter is connected with a compressor; the first switching device is connected between the input end of the frequency converter and an alternating current power source, the controller is connected with the control end of the frequency converter and the control end of the first switching device, and the controller is configured to obtain frequency conversion parameters of the compressor in the frequency conversion operation process, adjust the state of the first switching device according to parameter value changes of the frequency conversion parameters and control the compressor to operate. The variable frequency parameter is a parameter influencing the operation frequency of the compressor, the target time period is a time period when the parameter value of the variable frequency parameter is smaller than a first parameter threshold value, and when the parameter value of the variable frequency parameter is smaller than the first parameter threshold value, the compressor is in a preset low-frequency state. The technical problem that the compressor is unstable during low-frequency operation is solved.

Description

Technical Field

[0001] The present invention belongs to the technical field of compressor driving, and in particular relates to a compressor driving system and air conditioning equipment. Background Art

[0002] Small rooms or rooms with good insulation have a smaller cooling capacity requirement at a set temperature of around 27°, while the minimum cooling capacity of many air conditioners is much greater than this requirement. The difference between cooling demand and cooling capacity causes the compressor to stop and restart intermittently, resulting in large temperature fluctuations, poor comfort and noise. One of the core factors that limit the minimum cooling capacity of an air conditioner is the minimum stable operating frequency of the compressor.

[0003] Due to the large temperature changes inside the air-conditioning compressor and the presence of refrigerant and lubricating oil in the cavity, the reliability of the mechanical position sensor is difficult to guarantee. Therefore, the compressor of the variable frequency air conditioner uses position sensorless control, and the rotor position of its permanent magnet motor is estimated based on the position sensorless algorithm. When the compressor runs at a low frequency, the back electromotive force is small, the signal-to-noise ratio of the position sensorless algorithm is low, and it is greatly affected by external interference, resulting in inaccurate estimation of the rotor position, which is easy to cause loss of control. The large load torque disturbance generated by the refrigerant compression of the single-rotor compressor is more prone to loss of control. Therefore, the compressor is unstable when running at a low frequency. Summary of the invention

[0004] The present invention provides a compressor driving system and air conditioning equipment, which are used to solve the technical problem of instability of the compressor during low-frequency operation.

[0005] In a first aspect of the present invention, a compressor drive system is provided, comprising: a frequency converter, wherein the output end of the frequency converter is connected to a compressor; a first switching device, connected between the input end of the frequency converter and an AC power supply; and a controller, connected to a control end of the frequency converter and a control end of the first switching device, wherein the controller is configured to: obtain a frequency conversion parameter of the compressor during frequency conversion operation, and adjust a state of the first switching device according to a change in a parameter value of the frequency conversion parameter so that the first switching device is in an intermittent conduction state during a target time period, wherein the frequency conversion parameter is a parameter that affects the operating frequency of the compressor, and the target time period is a time period in which the parameter value of the frequency conversion parameter is less than a first parameter threshold value, and the parameter value of the frequency conversion parameter being less than the first parameter threshold value indicates that the compressor is in a preset low-frequency state.

[0006] In some embodiments, the controller is configured to: when the parameter value of the frequency conversion parameter decreases to less than the first parameter threshold, control the first switching device to change from the continuous conduction state to the intermittent conduction state; when the parameter value of the frequency conversion parameter increases to greater than a second parameter threshold, control the first switching device to change from the intermittent conduction state to the continuous conduction state, and the second parameter threshold is greater than or equal to the first parameter threshold.

[0007] In some embodiments, a second switching device is further included which is arranged in parallel with the first switching device, and the second switching device has a current-bearing capacity greater than that of the first switching device; the controller is also configured to: change the state of the second switching device according to the change in the parameter value of the frequency conversion parameter, so that the second switching device is in an off state during the target time period and in a closed state during other time periods except the target time period.

[0008] In some embodiments, the first switch device is a unidirectionally controllable semiconductor switch or a bidirectionally controllable semiconductor switch, and the second switch device is a mechanical switch.

[0009] In some embodiments, the controller is further configured to: when the parameter value of the frequency conversion parameter decreases to less than the first parameter threshold, control the first switching device to change from the off state to the intermittent conduction state, and control the second switching device to change from the closed state to the off state; when the parameter value of the frequency conversion parameter increases to greater than the second parameter threshold, control the second switching device to change from the off state to the closed state, and control the first switching device to change from the intermittent conduction state to the off state, and the second parameter threshold is greater than or equal to the first parameter threshold.

[0010] In some embodiments, the controller is configured to: control the second switching device from a closed state to an off state after a first preset delay time of controlling the first switching device to change from an off state to the intermittent on state; and / or control the first switching device from the intermittent on state to an off state after a second preset delay time of controlling the second switching device to change from an off state to a closed state.

[0011] In some embodiments, the controller is configured to: continuously obtain the AC power supply voltage within the target time period; and adjust the state of the first switching device according to the change in the size relationship between the AC power supply voltage and the target voltage value, so that the first switching device is in the intermittent conduction state during the target time period.

[0012] In some embodiments, the controller is configured to: drive the first switching device to be intermittently turned on based on a first PWM signal during a time period when the voltage value of the AC power supply voltage is greater than the target voltage value, and / or drive the first switching device to be in a continuous conduction state during a time period when the voltage value of the AC power supply voltage is not greater than the target voltage value; wherein the target voltage value is determined based on the maximum effective duty cycle of the three-phase inverter circuit in the inverter.

[0013] In some embodiments, the controller is further configured to: obtain the AC power supply voltage and the DC bus voltage of the compressor drive system when the compressor drive system is powered on; when the voltage value of the AC power supply voltage is greater than the DC bus voltage, drive the first switching device to start operation based on the second PWM signal; when the DC bus voltage rises to a voltage difference with the maximum output voltage of the AC power supply that is not greater than a preset threshold, control the duty cycle of the second PWM signal to gradually increase to 100% so that the first switching device enters a continuously on state.

[0014] In some embodiments, the compressor drive system further includes a second switching device arranged in parallel with the first switching device, and the controller is further configured to control the second switching device to close after a third delay time when the duty cycle of the second PWM signal reaches 100%.

[0015] In some embodiments, the controller is further configured to: when driving the first switching device to start action based on a second PWM signal, determine the duty cycle of the second PWM signal according to the ratio between the AC power supply voltage and the DC bus voltage; or determine the duty cycle of the second PWM signal according to the difference between the current detection value and the current set value of the inverter.

[0016] In a second aspect of the present invention, an air conditioning device is provided, comprising a compressor and a compressor drive system connected to the compressor, wherein the compressor drive system is as described in any embodiment of the first aspect.

[0017] According to one or more embodiments provided by the present invention, at least the following technical effects or advantages are achieved:

[0018] A first switch device is added between the input end of the frequency converter and the AC power supply, the output end of the frequency converter is connected to the compressor, the controller is connected to the control end of the frequency converter and the control end of the first switch device, and the controller is used to obtain the frequency conversion parameters of the compressor during the frequency conversion operation process, and adjust the state of the first switch device according to the parameter value change of the frequency conversion parameter, so that the first switch device is in an intermittent conduction state during the time period when the parameter value of the frequency conversion parameter is less than the first parameter threshold. Since the three-phase modulation voltage required for the compressor to operate at a low frequency is small, the above technical solution allows the first switch device to be in an intermittent conduction state under the preset low frequency state of the compressor, which can reduce the DC bus voltage, thereby reducing the voltage difference between the DC bus voltage and the three-phase modulation voltage, so that the three-phase inverter circuit in the frequency converter can use a larger duty cycle to output the three-phase modulation voltage. That is, the effective signal is increased, and the signal-to-noise ratio of the position-free sensor algorithm is improved when the external interference remains unchanged, thereby improving the accuracy of the rotor position estimation of the position-free sensor control, which is conducive to improving the stability of the compressor when operating at a low frequency and avoiding the compressor from losing control when operating at a lower frequency. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings required for use in the description of the embodiments. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0020] Figure 1 A block diagram of a compressor drive system provided by an embodiment of the present invention;

[0021] Figure 2 A schematic diagram of the structure of a compressor drive system provided by some embodiments of the present invention;

[0022] Figure 3 Schematic diagram of the structure of the compressor drive system provided by other embodiments of the present invention

[0023] Figure 4 A schematic diagram of the structure of a compressor drive system provided in some other embodiments of the present invention;

[0024] Figure 5 is an execution timing diagram of the first switching device and the second switching device in some implementation modes of the present invention;

[0025] Figure 6 Schematic diagram of the states of the first switching device and the second switching device in the target time period in some embodiments of the present invention;

[0026] Figure 7Schematic diagram of the states of the first switch device and the second switch device in the target time period in some other embodiments of the present invention;

[0027] Figure 8 Schematic diagram of the states of the first switch device and the second switch device in the target time period in some other embodiments of the present invention;

[0028] Fig. 9 A connection diagram of a second switching power supply in some implementation modes of the present invention;

[0029] Fig.10 A connection diagram of a first switching power supply in some implementation modes of the present invention;

[0030] Fig.11 Schematic diagram of connection between the first switching power supply and the second switching power supply in some other embodiments of the present invention. DETAILED DESCRIPTION

[0031] In order to make the purpose, technical solution and advantages of the present invention clearer, the technical solution in the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings in the embodiment of the present invention. Obviously, the described embodiment is only a part of the embodiment of the present invention, not all the embodiments. Based on the embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0032] It should be noted that the terms "first", "second", etc. in the specification and claims of the present invention and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchanged where appropriate, so that the embodiments of the present invention described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any variations thereof are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0033] The present invention provides a compressor driving system. Figure 1 FIG. 1 is a block diagram of a compressor drive system provided by an embodiment of the present invention. Figure 1 As shown, the compressor driving system 100 includes: an inverter 110, a first switching device Q1 and a controller 120. The output end of the inverter 110 is connected to the compressor 200; the first switching device Q1 is connected between the input end of the inverter 110 and the AC power source 300; the controller 120 is connected to the control end of the inverter 110 and the control end of the first switching device Q1.

[0034] The controller 120 is configured to: obtain the frequency conversion parameters of the compressor 200 during the frequency conversion operation, change the state of the first switching device Q1 according to the change of the parameter value of the frequency conversion parameter, so that the first switching device Q1 is in an intermittent conduction state during the target time period, the frequency conversion parameter is a parameter that affects the operating frequency of the compressor 200, and the parameter value of the frequency conversion parameter is less than the first parameter threshold value, indicating that the compressor 200 is in a preset low-frequency state.

[0035] It should be noted that, since the accuracy of the rotor position estimation is related to the mechanical frequency of the compressor, the related technology is to control the permanent magnet synchronous motor of the compressor in the entire operation process of the compressor 200 in the Id=0 or MTPA control mode, resulting in the compressor 200 having a minimum stable operating frequency, and it is necessary to give the compressor 200 a minimum operating frequency that is not lower than the minimum stable operating frequency, that is, the compressor in the related technology does not operate at a frequency point below the minimum operating frequency. The preset low-frequency state in the embodiment of the present invention refers to the state when the target operating frequency of the compressor 200 is lower than the minimum stable operating frequency, for example: the permanent magnet synchronous motor of the compressor 200 is always controlled in the Id=0 or MTPA control mode, resulting in the minimum stable operating frequency of the compressor 200 being 10Hz. Then, the minimum operating frequency of the compressor 200 can be set to 10Hz or a frequency point slightly greater than 10Hz, and the preset low-frequency state is the state when the target operating frequency of the compressor is lower than 10Hz. However, the minimum stable operating frequency of different compressors when controlled in the Id=0 or MTPA control mode is different, and the preset low-frequency state is correspondingly different.

[0036] In some embodiments, the variable frequency parameter may be a target operating frequency of the compressor 200. The target operating frequency of the compressor 200 changes dynamically with the set temperature and the ambient temperature of the environment being acted upon. The target operating frequency is the mechanical frequency required by the compressor determined according to the temperature difference between the ambient temperature and the set temperature. The greater the temperature difference between the ambient temperature and the set temperature, the greater the target operating frequency. It is necessary to continuously detect the ambient temperature and the set temperature during the variable frequency operation of the compressor 200 to track the dynamic changes in the target operating frequency of the compressor 200.

[0037] In other embodiments, the frequency conversion parameter may be the maximum effective duty cycle of the three-phase inverter circuit 113. In order to obtain the maximum effective duty cycle of the three-phase inverter circuit 113, it may include: obtaining the switch duty cycle difference between each two-phase inverter circuit in the three-phase inverter circuit 113; determining the effective duty cycle of the corresponding phase inverter circuit based on the switch duty cycle difference between each two-phase inverter circuit in the three-phase inverter circuit 113, so as to obtain the three-phase effective duty cycle corresponding to the three-phase inverter circuit 113; and obtaining the maximum effective duty cycle from the three-phase effective duty cycles corresponding to the three-phase inverter circuit 113.

[0038] The difference in the switching duty cycle between each two-phase inverter circuit can be calculated by referring to the following formula: xy =D x -D y ,x,y=u,v,w, where D x , D y is the duty cycle of any two-phase inverter circuit. Duv, Dwu, and Dvw represent the difference in the switching duty cycle between two phases in the three phases UVW respectively. The effective duty cycle Du0, Dv0, Dw0 of each phase inverter circuit and the maximum effective duty cycle Dmax are calculated by referring to the following formula:

[0039]

[0040] Figure 2 The schematic diagram of the structure of the compressor drive system provided by some embodiments of the present invention. Figure 2 As shown, the frequency converter 110 includes a first rectifier circuit 111, a passive PFC (Power Factor Correction) and filter circuit 112, and a three-phase inverter circuit 113. Among them, the first switch device Q1 is connected between the output end of the AC power supply 300 and the input end of the first rectifier circuit 111. That is, one input end of the first rectifier circuit 111 is connected to one end of the first switch device Q1, the other end of the first switch device Q1 is connected to one output end of the AC power supply 300, and the other output end of the AC power supply 300 is connected to the other input end of the first rectifier circuit 111.

[0041] It should be noted that the first switch device Q1 is a semiconductor switch device with a switching frequency greater than 2kHz, which can quickly perform switching actions. In some embodiments, only the first switch device Q1 is provided between the output end of the AC power supply 300 and the input end of the first rectifier circuit 111. The first switch device Q1 can be used as follows: Figure 2The bidirectional controllable semiconductor switch shown in . If only the first switching device Q1 is provided between the input end of the frequency converter 110 and the AC power supply 300, in order to adjust the state of the first switching device Q1 according to the parameter value change of the frequency conversion parameter. The controller 120 is configured to: when the parameter value of the frequency conversion parameter is reduced to less than the first parameter threshold, it indicates that the compressor 200 enters the preset low-frequency state, and controls the first switching device Q1 to change from the continuous conduction state to the intermittent conduction state. After the parameter value of the frequency conversion parameter is reduced to less than the first parameter threshold for a period of time, the temperature difference between the ambient temperature and the set temperature will gradually increase due to the reduction in cooling capacity. When the parameter value of the frequency conversion parameter increases to greater than the second parameter threshold, it indicates that the compressor 200 exits the preset low-frequency state, and controls the first switching device Q1 to change from the intermittent conduction state to the continuous conduction state, wherein the second parameter threshold is greater than or equal to the first parameter threshold.

[0042] Through the above-mentioned multiple embodiments, the first switch device Q1 can be placed in an intermittent conduction state after the compressor 200 enters the preset low-frequency state, which can reduce the DC bus voltage compared to the continuous conduction state, that is, reduce the Figure 2 The bus voltage Udc of the electrolytic capacitor E between points a and b shown in the figure, because the three-phase modulation voltage required by the compressor 200 in the preset low-frequency state is relatively low, thereby reducing the voltage difference between the DC bus voltage and the required three-phase modulation voltage, making the signal duty cycle used by the three-phase inverter circuit 113 to modulate the voltage larger, thereby increasing the effective signal, and improving the signal-to-noise ratio of the position-free sensor algorithm when the external interference remains unchanged. After the compressor 200 exits the preset low-frequency state, because the required three-phase modulation is relatively high, the first switch device Q1 is in a continuous conduction state, which can increase the DC bus voltage, so that the required three-phase modulation voltage can be obtained through the three-phase inverter circuit 113.

[0043] like Figure 3 and Figure 4 As shown, in some embodiments, the compressor drive system 100 may further include a second switch device K1 arranged in parallel with the first switch device Q1, and the second switch device K1 has a current bearing capacity greater than the first switch device Q1. Among them, the on-resistance of the second switch device K1 is less than the on-resistance of the first switch device Q1, and the second switch device K1 has the ability to withstand a larger current. Therefore, the second switch device K1 can adopt a mechanical switch, that is, a mechanical relay. In the case where the compressor drive system 100 also includes a second switch device K1, the controller 120 is also configured to: change the state of the second switch device K1 according to the parameter value change of the frequency conversion parameter, so that the second switch device K1 is in an off state in the target time period and in a closed state in other time periods except the target time period.

[0044] In the case where the first switch device Q1 and the second switch device K1 are connected in parallel between the output end of the AC power supply 300 and the input end of the first rectifier circuit 111, the first switch device Q1 can be a unidirectional controllable semiconductor switch (such as Figure 3 As shown) or a bidirectionally controllable semiconductor switch (as Figure 4 shown) are all acceptable.

[0045] In the case where the first switch device Q1 and the second switch device K1 are connected in parallel between the output end of the AC power supply 300 and the input end of the first rectifier circuit 111, the controller 120 is configured to: when the parameter value of the variable frequency parameter decreases to less than the first parameter threshold, it indicates that the compressor 200 enters a preset low frequency state, controls the first switch device Q1 to change from the off state to the intermittent on state, and controls the second switch device K1 to change from the closed state to the off state. Figure 5 As shown, in some embodiments, in order to protect the first switch device Q1 and the second switch device K1, after controlling the first switch device Q1 to change from the off state to the intermittent conduction state for a first preset delay time (Tdelay1), the second switch device K1 is controlled to change from the closed state to the off state. When the parameter value of the variable frequency parameter increases to be greater than the second parameter threshold, it indicates that the compressor 200 exits the preset low frequency state, controls the second switch device K1 to change from the off state to the closed state, and controls the first switch device Q1 to change from the intermittent conduction state to the off state, wherein the second parameter threshold is greater than or equal to the first parameter threshold. Figure 5 As shown, in some embodiments, in order to protect the first switching device Q1 and the second switching device K1, after controlling the second switching device K1 to change from the off state to the closed state for a second preset delay time (Tdelay2), the first switching device Q1 is controlled to change from the intermittent conduction state to the off state.

[0046] It is understandable that the first preset delay time and the second preset delay time can be set to the same or different durations.

[0047] In some implementations, if the second parameter threshold is greater than the first parameter threshold, hysteresis control may be implemented to improve the state stability of the first switching device Q1.

[0048] In the embodiment of the present invention, the first parameter threshold and the second parameter threshold must be of the same type as the frequency conversion parameter:

[0049] If the variable frequency parameter is the target operating frequency of the compressor 200, the first parameter threshold is the first preset frequency, and the second parameter threshold is the second preset frequency greater than or equal to the first preset frequency. That is, when the target operating frequency of the compressor 200 decreases to less than the first preset frequency, it indicates that the compressor 200 enters the preset low frequency state; when the target operating frequency of the compressor 200 increases to greater than the second preset frequency, it indicates that the compressor 200 exits the preset low frequency state.

[0050] Among them, the first preset frequency and the second preset frequency are not less than the minimum stable operating frequency of the compressor 200. In order to improve the operating stability of the compressor 200, the first preset frequency can be a frequency point that is close to the minimum stable operating frequency and greater than the minimum stable operating frequency. The compressor 200 can be controlled in advance using Id=0 or MTPA control mode to run the full frequency range, and the minimum operating frequency that makes the compressor 200 run without losing control is measured, that is, the minimum stable operating frequency. For example: if the minimum stable operating frequency of the compressor 200 is measured at 10Kz, the first preset frequency and the second preset frequency can be set to two different frequency values ​​in the range of 10Hz to 20Hz. It should be noted that the minimum stable operating frequencies of different compressors 200 will vary, and the first preset frequency and the second preset frequency can be set according to the measured minimum stable operating frequency.

[0051] If the variable frequency parameter is the maximum effective duty cycle of the three-phase inverter circuit 113 used to drive the compressor 200, the first parameter threshold is the first preset duty cycle, and the second parameter threshold is the second preset duty cycle that is greater than or equal to the first preset duty cycle. That is, when the maximum effective duty cycle of the three-phase inverter circuit 113 decreases to the first preset duty cycle, it indicates that the compressor 200 enters the preset low-frequency state; when the maximum effective duty cycle of the three-phase inverter circuit 113 increases to the second preset duty cycle, it indicates that the compressor 200 exits the preset low-frequency state. The first preset duty cycle and the second preset duty cycle can be set according to the dead time T set by the three-phase inverter circuit 113. d And the switching period Tsw setting, such as: can be set to the dead zone duty cycle T d Compared with controlling the state of the first switching device Q1 according to the target operating frequency of the compressor 200, controlling the state of the first switching device Q1 using the maximum effective duty cycle is more accurate and objective.

[0052] In some embodiments, the controller 120 is configured to: continuously obtain the AC power supply voltage Uac within a target time period; adjust the state of the first switching device Q1 according to the change in the size relationship between the AC power supply voltage Uac and the target voltage value Uset, so that the first switching device Q1 is in an intermittent conduction state during the target time period, wherein the target voltage value Uset can be determined based on the maximum effective duty cycle of the three-phase inverter circuit 113 in the inverter 110.

[0053] The state of the first switch device Q1 is adjusted according to the change in the magnitude relationship between the AC power supply voltage Uac and the target voltage value Uset, so as to realize that the first switch device Q1 is in an intermittent conduction state in the target time period. The intermittent conduction state of the first switch device Q1 in the target time period has multiple forms, which can be realized by using the following two methods 1 and 2 separately or in combination: 1. In the time period when the voltage value of the AC power supply voltage Uac is greater than the target voltage value Uset, the first switch device Q1 is driven to be periodically intermittently turned on based on the first PWM signal; 2. In the time period when the voltage value of the AC power supply voltage Uac is not greater than the target voltage value Uset, the first switch device Q1 is driven to be continuously turned on. That is to say, there can be the following multiple different implementations to realize the intermittent conduction state of the first switch device Q1 in the target time period, which are described below respectively:

[0054] like Figure 6 As shown, in some embodiments, the controller 120 can be configured as follows: during the change of the AC power supply voltage, in the time period when the voltage value of the AC power supply voltage Uac is greater than the target voltage value Uset, the first switching device Q1 is driven to be periodically intermittently turned on based on a first PWM (pulsewidth modulation) signal; in the time period when the voltage value of the AC power supply voltage Uac is not greater than the target voltage value Uset, the first switching device Q1 is in the off state.

[0055] like Figure 7 As shown, in other embodiments, the controller 120 can be configured as follows: during the change process of the AC power supply voltage, in the time period when the voltage value of the AC power supply voltage Uac is greater than the target voltage value Uset, the first switching device Q1 is driven to be intermittently turned on based on the first PWM signal; in the time period when the voltage value of the AC power supply voltage Uac is not greater than the target voltage value Uset, the first switching device Q1 is driven to be in a continuous conduction state.

[0056] It should be understood that the duty cycle of the first PWM signal can be set to a fixed duty cycle according to actual needs, such as 50%.

[0057] like Figure 8As shown, in other embodiments, the controller 120 may also be configured as follows: during the change of the AC power supply voltage, in the time period when the voltage value of the AC power supply voltage Uac is greater than the target voltage value Uset, the first switch device Q1 is in the off state; in the time period when the voltage value of the AC power supply voltage Uac is not greater than the target voltage value Uset, the first switch device Q1 is driven to be in the continuous on state. This achieves that the first switch device Q1 is in the intermittent on state during the target time period.

[0058] like Figure 6 , Figure 7 and Figure 8 As shown, the voltage value of the AC power supply voltage Uac is greater than the target voltage value Uset, that is, abs(Uac)>Uset is satisfied, where abs(Uac) is the voltage value of the AC power supply voltage, and Uset is the target voltage value. That is, it is necessary to satisfy Uac>Usetp and Uac<Usetn, Uac is the AC power supply voltage with positive and negative polarities, Usetp=+Uset, Usetn=-Uset. The voltage value of the AC power supply voltage Uac is not greater than the target voltage value Uset, which means that Usetn≤Uac≤Usetp needs to be satisfied.

[0059] In some embodiments, the target voltage value Uset can be calculated based on the maximum effective duty cycle of the three-phase inverter circuit 113: after LPF (Low Pass Filter) filtering the duty cycle difference between the maximum effective duty cycle of the three-phase inverter circuit 113 and the first preset duty cycle, the filtering result is subjected to PI calculation by a PI regulator to obtain a candidate voltage value; determine whether the candidate voltage value is within the limit range; if so, use the candidate voltage value as the target voltage value; if it exceeds the limit range, use the upper limit value or lower limit value of the limit range as the target voltage value Uset.

[0060] In some embodiments, the controller 120 is further configured to: obtain the AC power supply voltage and the DC bus voltage of the compressor drive system 100 when the compressor drive system 100 is powered on; when the voltage value of the AC power supply voltage is greater than the DC bus voltage, that is, when abs(Uac)>Udc is satisfied, drive the first switch device Q1 to start action based on the second PWM signal; when the DC bus voltage rises to a voltage difference with the maximum output voltage of the AC power supply 300 that is not greater than a preset threshold, that is, when Udc=max(Uac)-△U is satisfied, control the duty cycle of the second PWM signal to gradually increase to 100%, so that the first switch device Q1 enters a continuous conduction state, wherein △U is a preset threshold, max(Uac) is the maximum input voltage, and Udc is the DC bus voltage. For example, the preset threshold △U can be set to 20V.

[0061] In some implementations, after the duty cycle of the second PWM signal reaches a third delay time of 100%, the second switch device K1 is controlled to close to protect the switch device.

[0062] Before the voltage difference between the DC bus voltage and the maximum output voltage of the AC power supply 300 is increased to be no greater than a preset threshold, the duty cycle of the second PWM signal can be controlled in the following ways:

[0063] In some implementations, the duty cycle of the second PWM signal may be determined according to a ratio between the AC power supply voltage and the DC bus voltage: D=abs(Uac) / Udc.

[0064] In other embodiments, the duty cycle of the current-controlled second PWM signal can also be constructed to ensure that the current does not exceed the limit value. In this way, the duty cycle of the second PWM signal can be determined according to the difference between the current detection value and the current setting value of the inverter 110. The current detection value can be a phase current or the current of the inductor L. That is, the duty cycle of the second PWM signal is obtained by performing PI calculation based on the difference between the phase current amplitude Is and the set current value IsSet: D=PI(IsSet-Is). Or according to the inductor current I of the inverter 110 L With the set current value I L The difference between Set is used to calculate the duty cycle of the second PWM signal: D = PI (I L Set-I L ).

[0065] In other embodiments, the duty cycle of the second PWM signal may be a fixed small duty cycle, such as a 1% duty cycle. When the DC bus voltage increases to a voltage difference with the maximum output voltage of the AC power supply 300 that is not greater than a preset threshold, the duty cycle of the second PWM signal gradually increases from the fixed small duty cycle to 100%.

[0066] If the compressor driving system 100 provided in the embodiment of the present invention is applied to a variable frequency air conditioner. Fig. 9 and Fig.11 As shown, the indoor unit of the variable frequency air conditioner is provided with a first switching power supply 140 for controlling the first switching device Q1 and the second switching device K1. Fig.10 As shown, the compressor drive system 100 further includes a second switching power supply 150 for controlling the three-phase inverter circuit 113 and the IGBT (Insulate-Gate Bipolar Transistor) device in the PFC circuit. Fig. 9 and Fig.10 As shown, the first switching power supply 140 and the second switching power supply 150 can be the same switching power supply. Fig.11 As shown, the first switching power supply 140 and the second switching power supply 150 may be two independently arranged switching power supplies.

[0067] like Fig. 9 As shown, in some embodiments, when the second switching power supply 150 for driving the three-phase inverter circuit 113 and the IGBT device in the PFC circuit is powered by the electrolytic capacitor E, the compressor drive system 100 further includes a buffer circuit connected in parallel with the first switching device Q1. The buffer circuit includes a PTC (Positive Temperature Coefficient, which refers to a semiconductor material or component with a large positive temperature coefficient) and a third switching device K2 connected in series, which is used to achieve power-on buffering.

[0068] It is understandable that if Fig.10 As shown, the first switching power supply 140 can be powered by the AC power supply 300. At this time, the first switching power supply 140 can be connected to the AC power supply 300 through the second rectifier circuit 160. It can be understood that Fig.10 As shown, the first switch device Q1 and the second switch device k1 form a composite switch S1. Fig. 9 or Fig.11 As shown, the first switch device Q1, the second switch device K1 and the third switch device K2 together form a composite switch S1. Fig.11 As shown, the output of the S1 compound switch of the indoor unit is connected to the rectifier bridge of the outdoor unit, that is, there is no relay (that is, K1 and K2 in the indoor unit) and PTC on the main power supply of the outdoor unit, which is the application feature of the air conditioner.

[0069] Although some embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they have learned the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiment and all changes and modifications that fall within the scope of the present invention.

[0070] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

Claims

1. A compressor drive system, characterized in that: include: A frequency converter, wherein an output end of the frequency converter is connected to the compressor; The first switch device is connected between the input terminal of the inverter and the AC power supply: A controller is connected to the control end of the frequency converter and the control end of the first switching device, and the controller is configured to: obtain the frequency conversion parameter of the compressor during the frequency conversion operation, and adjust the state of the first switching device according to the change of the parameter value of the frequency conversion parameter, so that the first switching device is in an intermittent conduction state during a target time period, the frequency conversion parameter is a parameter that affects the operating frequency of the compressor, and the target time period is a time period when the parameter value of the frequency conversion parameter is less than a first parameter threshold value. The parameter value of the frequency conversion parameter is less than the first parameter threshold value, which indicates that the compressor is in a preset low-frequency state.

2. The compressor drive system according to claim 1, characterized in that: The controller is configured to: When the parameter value of the frequency conversion parameter decreases to be less than the first parameter threshold, controlling the first switching device to change from the continuous conduction state to the intermittent conduction state; When the parameter value of the frequency conversion parameter increases to be greater than a second parameter threshold, the first switching device is controlled to change from the intermittent conduction state to the continuous conduction state, and the second parameter threshold is greater than or equal to the first parameter threshold.

3. The compressor drive system according to claim 1, characterized in that: Also comprising a second switch device arranged in parallel with the first switch device, the second switch device having a current bearing capacity greater than the current bearing capacity of the first switch device; The controller is further configured to change the state of the second switching device according to the change in the parameter value of the frequency conversion parameter, so that the second switching device is in an off state during the target time period and in a closed state during other time periods except the target time period.

4. The compressor drive system according to claim 3, characterized in that: The first switch device is a unidirectionally controllable semiconductor switch or a bidirectionally controllable semiconductor switch, and the second switch device is a mechanical switch.

5. The compressor drive system according to claim 4, characterized in that: The controller is also configured to: When the parameter value of the frequency conversion parameter decreases to be less than the first parameter threshold, the first switch device is controlled to change from the off state to the intermittent on state, and the second switch device is controlled to change from the closed state to the off state; When the parameter value of the frequency conversion parameter increases to be greater than a second parameter threshold, the second switching device is controlled to change from an off state to a closed state, and the first switching device is controlled to change from the intermittent conduction state to an off state, and the second parameter threshold is greater than or equal to the first parameter threshold.

6. The compressor drive system according to claim 5, characterized in that: The controller is configured to: After controlling the first switch device to change from the off state to the intermittent on state for a first preset delay time, controlling the second switch device to change from the on state to the off state; and / or After controlling the second switching device to change from the off state to the on state for a second preset delay time, controlling the first switching device to change from the intermittent on state to the off state.

7. The compressor drive system according to any one of claims 1 to 6, characterized in that: The controller is configured to: During the target time period, continuously obtaining the AC power supply voltage; According to the change in the magnitude relationship between the AC power supply voltage and the target voltage value, the state of the first switching device is adjusted so that the first switching device is in the intermittent conduction state during the target time period.

8. The compressor drive system according to claim 7, characterized in that: The controller is configured to: In a time period when the voltage value of the AC power supply voltage is greater than the target voltage value, the first switching device is driven to be intermittently turned on based on the first PWM signal, and / or During a time period when the voltage value of the AC power supply voltage is not greater than the target voltage value, driving the first switching device to be in a continuously conducting state; The target voltage value is determined based on the maximum effective duty cycle of the three-phase inverter circuit in the inverter.

9. The compressor drive system according to claim 8, characterized in that: The controller is also configured to: When the compressor drive system is powered on and started, obtaining an AC power supply voltage and a DC bus voltage of the compressor drive system; When the voltage value of the AC power supply voltage is greater than the DC bus voltage, driving the first switch device to start operation based on the second PWM signal; When the voltage difference between the DC bus voltage and the maximum output voltage of the AC power supply is not greater than a preset threshold, the duty cycle of the second PWM signal is controlled to gradually increase to 100% to enable the first switching device to enter a continuous conduction state.

10. The compressor drive system according to claim 9, wherein: The compressor driving system further includes a second switching device arranged in parallel with the first switching device, and the controller is further configured to control the second switching device to close after a third delay time when the duty cycle of the second PWM signal reaches 100%.

11. The compressor drive system according to claim 9, wherein: The controller is also configured to: When the first switching device is driven to start action based on the second PWM signal, the duty cycle of the second PWM signal is determined according to the ratio between the AC power supply voltage and the DC bus voltage; or the duty cycle of the second PWM signal is determined according to the difference between the current detection value and the current setting value of the inverter.

12. An air conditioning device, characterized in that: It comprises a compressor, and a compressor driving system connected to the compressor, wherein the compressor driving system is as described in any one of claims 1-11.

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