Compressor starting method, control system, compressor and air conditioner

Abstract

According to the compressor starting method, the control system, the compressor and the air conditioner, before the compressor enters closed-loop starting, whether inertia rotation exists in a rotor or not is judged, a control signal is generated under the condition that inertia rotation exists, and an inversion module is controlled to achieve short circuit of a three-phase winding of the compressor; the rotating speed of the rotor is effectively reduced; and then, when the rotating speed is lower than a preset threshold value, a closed-loop starting strategy is executed to complete starting. According to the method, by adding the braking step in the inertia rotation state, the problem of inaccurate rotor position estimation caused by the high rotation speed is avoided, it is ensured that the compressor can be reliably switched to closed-loop operation in the low-speed state, the technical problem of starting failure in the inertia low-speed rotation scene of the rotor is effectively solved, and the reliability of the compressor is improved. And the starting success rate and the overall operation reliability of the compressor are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of compressors, and in particular to a compressor starting method, a control system, a compressor and an air conditioner. Background Art

[0002] A compressor is a device that increases the pressure of gas from low to high pressure. It is widely used in refrigeration, air conditioning, industrial gas compression and pneumatic equipment. Its working principle is to drive the internal moving parts (piston, screw or blade) to compress the gas through the input of mechanical energy, thereby increasing the pressure and temperature of the gas.

[0003] In the prior art, when the compressor is started, there is a technical problem of startup failure when the rotor rotates at a low speed due to inertia. Summary of the invention

[0004] The purpose of the present invention is to overcome the above-mentioned technical deficiencies and provide a compressor starting method, a control system, a compressor and an air conditioner to solve the technical problem of starting failure in the related art when the rotor inertia rotates at a low speed during compressor starting.

[0005] In order to achieve the above technical objectives, the present invention adopts the following technical solutions:

[0006] In a first aspect, the present invention provides a method for starting a compressor, the method comprising:

[0007] Before the compressor enters the closed-loop startup, determine whether the compressor rotor currently has inertial rotation;

[0008] When it is determined that there is inertial rotation, a control signal is generated and sent to a preset inverter module; wherein the inverter module is an inverter module for driving the compressor, and the control signal is used to control the on and off of the inverter module so that the three-phase winding of the compressor is short-circuited to reduce the speed of the compressor rotor;

[0009] When it is detected that the rotation speed of the compressor rotor is lower than a preset threshold, a preset closed-loop starting strategy is executed to complete the closed-loop starting of the compressor.

[0010] In a second aspect, the present invention provides a control system for a compressor, comprising:

[0011] An inverter module, used for driving the compressor;

[0012] A controller is used to determine whether the current compressor rotor has inertial rotation before the compressor enters closed-loop startup, and when it is determined that inertial rotation exists, generate a control signal and send it to the inverter module; wherein the inverter module is an inverter module for driving the compressor, and the control signal is used to control the on and off of the inverter module so that the three-phase winding of the compressor is short-circuited to reduce the speed of the compressor rotor, and when it is detected that the speed of the compressor rotor is lower than a preset threshold, execute a preset closed-loop startup strategy to complete the closed-loop startup of the compressor.

[0013] In a third aspect, the present invention provides a compressor, comprising a controller, wherein the controller is used to execute the above method or comprises the above control system.

[0014] In a fourth aspect, the present invention provides an air conditioner, comprising a controller, wherein the controller is used to execute the above method or comprises the above control system.

[0015] Beneficial effects:

[0016] The compressor starting method provided by the present invention determines whether the rotor has inertial rotation before the compressor enters the closed-loop starting, and generates a control signal in the case of inertial rotation, controls the inverter module to achieve the short circuit of the three-phase winding of the compressor, thereby effectively reducing the speed of the rotor; then, when the speed is lower than the preset threshold, executes the closed-loop starting strategy to complete the startup. This method avoids the problem of inaccurate rotor position estimation due to high speed by adding a braking step in the inertial rotation state, ensures that the compressor can reliably switch to closed-loop operation in a low-speed state, effectively solves the technical problem of startup failure in the scenario of rotor inertial low-speed rotation, and improves the startup success rate and overall operation reliability of the compressor. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 is a flow chart of a compressor starting method provided by an embodiment of the present invention;

[0018] Figure 2 is a flow chart of a compressor starting method provided by an embodiment of the present invention;

[0019] Figure 3 is a schematic diagram of a compressor driving inverter provided by an embodiment of the present invention;

[0020] Figure 4 is a schematic diagram of an inverter provided by an embodiment of the present invention;

[0021] Figure 5 It is a flow chart of a compressor starting method provided by an embodiment of the present invention. DETAILED DESCRIPTION

[0022] In order to enable those skilled in the art to better understand the solution of the present application, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work should fall within the scope of protection of the present application.

[0023] In the relevant technology, in the refrigeration system, the compressor is a device that realizes heat transfer, and its performance directly affects the reliability and efficiency of the entire system. The compressor is usually driven by a three-phase motor, and the inverter module converts direct current into three-phase alternating current with controllable frequency to drive the compressor.

[0024] The basic process of current compressor startup technology is to adjust the rotor speed through the closed-loop startup mode to achieve smooth operation. However, in actual applications, when the compressor is turned off, the rotor will be in a low-speed rotation state due to inertia. If the closed-loop startup mode is directly entered at this time, it is easy to cause startup failure due to inaccurate position estimation or speed control deviation. This problem is particularly prominent under harsh working conditions such as low-temperature liquid accumulation, high pressure and high temperature.

[0025] The closed-loop startup mode in the related art relies on accurate rotor position estimation and initial speed control. However, when the rotor is in an inertial low-speed rotation state, the instability of the three-phase current and speed will cause the control signal of the inverter module to fail or deviate, and it will not be able to switch to the closed-loop control mode correctly. In addition, the related art does not consider the impact of inertial speed on the startup process, lacks effective braking and initial state adjustment means, and the probability of startup failure increases significantly.

[0026] In order to solve this technical problem, the present embodiment provides a method for starting a compressor. This method adds the judgment of the inertial rotation state of the rotor and the control of the braking process before closed-loop startup. The controller generates and sends a control signal to the inverter module to short-circuit the three-phase winding of the compressor, thereby generating a braking current to reduce the speed. After the speed is reduced to a preset threshold, it switches to the closed-loop startup mode to complete the startup of the compressor. This method can effectively solve the startup failure problem caused by the inertial low-speed rotation of the rotor, ensure that the compressor can be successfully started once under various working conditions, and improve the reliability and life of the system.

[0027] like Figure 1 As shown, this embodiment provides a method for starting a compressor, the execution subject of the method may be a controller, and the method may include:

[0028] Step S12: Before the compressor enters the closed-loop startup, determine whether the compressor rotor currently has inertial rotation.

[0029] In this embodiment, the controller can collect relevant electrical parameters of the rotor motion to infer the inertial rotation state of the rotor. For example, the controller can sample the current signal of the three-phase winding (U phase, V phase and W phase) of the compressor in real time through a preset current sensor module. Since the three-phase current signal reflects the current electromagnetic state of the rotor, the motion state of the rotor can be judged by its fluctuation characteristics. The controller can use the three-phase winding current of the compressor to meet the current balance condition. The controller only needs to collect the U phase and V phase current values ​​to obtain the W phase current value by calculation. This step reduces the hardware requirements and ensures the integrity of the signal. Finally, through the fast Fourier transform (FFT), the controller extracts the frequency component related to the speed from the sampled three-phase current signal, and then estimates the actual speed of the rotor. For example, when the rotor rotates inertially, the winding will generate back electromotive force due to cutting the magnetic field. The controller can determine whether the rotor is rotating by analyzing the back electromotive force component in the three-phase winding voltage signal, and further determine the direction and magnitude of the speed in combination with the frequency and amplitude information.

[0030] The controller may preset an inertial rotation determination threshold (for example, the speed is greater than a certain minimum value, such as 5RPM). If the estimated speed is greater than this threshold, it is considered that the rotor is in inertial rotation; if the speed is lower than the threshold or zero, it is considered that the rotor is stationary.

[0031] In this embodiment, the closed-loop startup can be represented by real-time monitoring and feedback regulation of the operating state of the compressor by the controller, and dynamically adjusting the frequency, duty cycle or amplitude of the control signal, so that the compressor can gradually enter a stable operating state during the startup process. Specifically, the controller first monitors the operating state of the compressor in real time by sampling key parameters such as current, voltage, and speed, and obtains feedback information on the rotor position, speed, and motor load. Then, based on the feedback data monitored in real time, the controller calculates the target control parameter (target current or target speed) and generates a corresponding PWM signal to control the inverter module and adjust the three-phase winding current or voltage of the compressor. During the startup process, the controller dynamically adjusts the duty cycle, frequency, or amplitude of the PWM signal according to the deviation between the feedback information and the target value, thereby gradually accelerating the rotor and finally reaching a stable operating point. This closed-loop regulation mechanism ensures the smoothness and reliability of the startup.

[0032] In some embodiments, the controller can determine whether the compressor rotor is currently rotating inertially through a preset Hall sensor. It is understandable that if the compressor is equipped with a Hall sensor, the controller can directly read the output signal of the Hall sensor, which will change as the rotor rotates. By monitoring the frequency and direction of the change of the Hall sensor signal, the controller can directly determine the speed and rotation direction of the rotor.

[0033] In some embodiments, the controller can determine whether the current compressor rotor has inertial rotation through a preset rotary encoder. It is understandable that the pulse signal output by the rotary encoder can directly reflect the angle and speed of the rotor. The controller can quickly and accurately determine the inertial rotation state of the rotor by counting the frequency or phase changes of the rotary encoder pulses.

[0034] In some embodiments, the controller can determine whether the compressor rotor is currently rotating inertially through a preset flux estimation module. It is understandable that when the rotor rotates, the flux change will induce a flux feedback signal in the winding. The controller can calculate the real-time flux value based on the sampled winding current and voltage signals through the built-in flux estimation module. If the flux value changes frequently or periodically, it means that the rotor is in a rotating state.

[0035] Step S14: When it is determined that inertial rotation exists, a control signal is generated and sent to a preset inverter module; wherein the inverter module is an inverter module for driving the compressor, and the control signal is used to control the on and off of the inverter module, so that the three-phase winding of the compressor is short-circuited to reduce the speed of the compressor rotor.

[0036] In this embodiment, after detecting the inertial rotation of the compressor rotor, the controller may generate a control signal for braking according to a preset logic.

[0037] Specifically, Figure 4 As shown, when the inverter module is a three-phase full-bridge inverter, the three-phase full-bridge inverter is composed of three groups of upper and lower bridge arms, and each phase contains an upper bridge arm switch (such as Q1, Q3, Q5) and a lower bridge arm switch (such as Q2, Q4, Q6). The controller can generate a PWM signal and send it to the lower bridge arm switch drive channel of the inverter to turn on the lower bridge arm (Q2, Q4, Q6). At the same time, a shutdown signal is sent to the upper bridge arm switch (Q1, Q3, Q5) drive channel to ensure that the upper bridge arm is completely disconnected. The duty cycle of the PWM signal can be a fixed value (such as 50%) to ensure that the braking current is stable. In this case, the three-phase winding is short-circuited to form a braking current, and the speed of the compressor rotor is gradually reduced.

[0038] More specifically, the controller (e.g., DSP) can first use a fixed value (e.g., 50%) as a duty cycle parameter to avoid current shocks caused by excessively high duty cycles. Then, the operating frequency of the PWM signal is determined according to the design requirements of the three-phase full-bridge inverter (e.g., 8kHz or 10kHz). Finally, the PWM control module or timer module inside the DSP is used to generate a waveform that meets the set frequency and duty cycle. The DSP outputs corresponding PWM signals to the drive ports of Q2, Q4, and Q6 through the PWM channel, so that the lower bridge arm switch is periodically turned on and off. The DSP sends a constant low-level signal to Q1, Q3, and Q5 through the PWM output channel to ensure that the upper bridge arm is completely closed. When the three-phase lower bridge arms are turned on at the same time, the three-phase windings are short-circuited, generating a braking current and gradually reducing the rotor speed.

[0039] In the case where the inverter module is a three-phase half-bridge inverter, the three-phase half-bridge inverter has only three pairs of bridge arm switches, and each phase is controlled by a single switch. Therefore, the controller can generate a PWM signal adapted to the three-phase half-bridge inverter, so that a single switch of each phase is turned on and the three-phase winding is short-circuited. The PWM signal can continuously maintain a high level to ensure that the single switch is stably turned on.

[0040] When the inverter module is a multi-phase inverter (such as five-phase or six-phase), the controller can generate multiple PWM signals to control the switching state of each phase winding one by one, ensuring that the lower bridge arm of all phases is turned on and the upper bridge arm is turned off. Each phase signal can be generated independently to ensure phase synchronization. Secondly, the signal frequency matches the multi-phase winding design to avoid inter-phase interference.

[0041] In this embodiment, the controller can also calculate the effective value of the current three-phase braking current in real time by sampling the three-phase current signal of the winding, and determine the duty cycle of the PWM signal according to the current size to optimize the braking effect.

[0042] Specifically, when the current is large, a PWM signal with a low duty cycle is generated to reduce the risk of current overshoot. When the current is small, a PWM signal with a high duty cycle is generated to enhance the braking ability.

[0043] Step S16: When it is detected that the rotation speed of the compressor rotor is lower than a preset threshold, a preset closed-loop starting strategy is executed to complete the closed-loop starting of the compressor.

[0044] In this embodiment, when the controller detects that the rotation speed of the compressor rotor is lower than a preset threshold, the controller executes a preset closed-loop startup strategy to complete the closed-loop startup of the compressor.

[0045] In this embodiment, the controller can detect whether the rotation speed of the compressor rotor is lower than a preset threshold value in the following manner: the controller can detect whether the rotation speed of the compressor rotor is lower than a preset threshold value based on the frequency analysis of the current signal. Specifically, it can be understood that the rotation of the rotor will cause periodic current fluctuations in the winding, and the frequency of the current is proportional to the rotation speed. Therefore, the controller can sample the current signal of the three-phase winding (U phase, V phase, W phase), and can use the fast Fourier transform (FFT) or zero crossing detection algorithm to extract the frequency component of the signal, and then combined with the number of motor pole pairs, the controller can calculate the actual speed of the rotor. Finally, the controller can compare the calculated speed with the preset threshold. If it is less than the threshold, the speed is determined to meet the closed-loop startup condition.

[0046] In this embodiment, the controller can detect whether the rotation speed of the compressor rotor is lower than a preset threshold value in the following manner: the controller can detect whether the rotation speed of the compressor rotor is lower than a preset threshold value based on a back electromotive force (Back EMF) signal. Specifically, it can be understood that when the rotor rotates, the winding cuts the magnetic field to generate a back electromotive force, and its amplitude is proportional to the rotation speed. The controller can collect the three-phase winding voltage signal, calculate the amplitude of the back electromotive force, and then compare it with the back electromotive force threshold corresponding to the rotation speed threshold to determine whether the rotation speed meets the requirements.

[0047] In this embodiment, the controller can also detect whether the rotation speed of the compressor rotor is lower than a preset threshold value in the following manner: the controller can detect whether the rotation speed of the compressor rotor is lower than a preset threshold value based on an encoder or a Hall sensor. Specifically, the compressor can be equipped with an encoder or a Hall sensor, and the controller can directly read the rotation speed feedback signal and compare it with the preset threshold value.

[0048] In this embodiment, after detecting that the rotation speed is lower than a preset threshold, the controller switches to a closed-loop startup mode to gradually increase the rotation speed and ensure startup stability.

[0049] In this embodiment, the preset closed-loop startup strategy can be a vector control strategy based on speed feedback. Specifically, the controller can use the speed feedback signal (encoder or estimated signal) to adjust the amplitude and phase of the drive current in real time. More specifically, the controller can collect the real-time speed feedback value, compare it with the target speed, and calculate the deviation. The controller then uses the PI (proportional integral) control algorithm to adjust the current size and gradually increase the motor output torque. The controller finally adjusts the PWM signal frequency and duty cycle output by the inverter module to gradually accelerate the compressor to the target speed.

[0050] In this embodiment, the preset closed-loop startup strategy can be a startup control strategy based on a current closed loop. Specifically, the controller first monitors the winding current feedback signal in real time to ensure that the current amplitude is consistent with the set value. The controller then controls the current amplitude output by the inverter module by adjusting the PWM signal duty cycle. Finally, after the current reaches stability, the controller gradually increases the PWM frequency to accelerate the rotor.

[0051] In this embodiment, the preset closed-loop startup strategy may also be a direct startup strategy based on soft start, that is, by gradually increasing the duty cycle and frequency of the PWM signal, the voltage and current are controlled to gradually increase, thereby achieving smooth startup.

[0052] In this embodiment, the preset threshold is a critical value of the compressor rotor speed. When the speed is lower than this value, the controller determines that the rotor is slow enough to enter the closed-loop start-up mode, thereby avoiding the start-up failure problem caused by inertial rotation.

[0053] In this embodiment, the preset threshold value may be 1RPM, 2RPM or 3RPM, etc. Specifically, a compressor with a large rotor inertia may be set with a lower preset threshold value (such as 1RPM) to ensure that the rotor enters a closed-loop start after being fully decelerated. In a low temperature environment, the preset threshold value may also be set lower (such as 1RPM) to reduce the impact of liquid hammer on the start-up. Under high pressure conditions, the rotor braking efficiency may be reduced, so a high threshold value (such as 15RPM) may be set.

[0054] In this embodiment, the controller can also dynamically adjust the preset threshold value according to the real-time working conditions (such as temperature and pressure). For example, the threshold value is lowered when the ambient temperature is low, and the threshold value is appropriately increased when the ambient temperature is high.

[0055] In this embodiment, if the device fails to start up multiple times during the startup process, the controller can also optimize and dynamically adjust the threshold value through a learning mechanism (such as machine learning or heuristic rules).

[0056] The compressor starting method provided in this embodiment determines whether the rotor has inertial rotation before the compressor enters closed-loop starting, and generates a control signal in the case of inertial rotation, controls the inverter module to achieve short-circuiting of the three-phase winding of the compressor, thereby effectively reducing the speed of the rotor; then, when the speed is lower than the preset threshold, executes the closed-loop starting strategy to complete the startup. This method avoids the problem of inaccurate rotor position estimation due to high speed by adding a braking step in the inertial rotation state, ensures that the compressor can reliably switch to closed-loop operation in a low-speed state, effectively solves the technical problem of startup failure in the scenario of rotor inertial low-speed rotation, and improves the startup success rate and overall operation reliability of the compressor.

[0057] like Figure 2As shown, in some embodiments, the control signal is a PWM signal, and the step of generating the control signal and sending it to a preset inverter module includes:

[0058] Step S142: Determine the current effective value of the three-phase braking current.

[0059] In this embodiment, two current sensors may be pre-arranged in the inverter module of the compressor to respectively collect the current signals of the U phase and the V phase in the three-phase winding. The controller (DSP) may collect the current values ​​of the U phase and the V phase in real time through the ADC (analog-to-digital converter) module. The sampling frequency may be higher than the highest frequency of the current signal to satisfy the Nyquist sampling theorem.

[0060] The controller can be based on the current balance relationship, that is, the characteristic that the sum of the three-phase current is zero:

[0061] I U +I V +I W =0

[0062] In the formula, I U Expressed as the instantaneous current value of phase U, I V Expressed as the instantaneous current value of phase V, I W Indicated as the instantaneous current value of W phase.

[0063] Therefore, the instantaneous current value of phase W is calculated by the following formula:

[0064] I W =-(I U +I V )

[0065] Therefore, it is avoided to configure a current sensor separately for the W phase, thereby reducing the hardware cost.

[0066] Therefore, the three-phase instantaneous current value I U , I V and I W , calculate the instantaneous effective value I of the three-phase braking current eff The effective value of the three-phase current can be defined as the root mean square value of the three-phase current:

[0067]

[0068] In this embodiment, the controller uses the above calculation result as the current three-phase braking current effective value and stores it in the memory for use in subsequent steps.

[0069] In this embodiment, in order to improve the calculation accuracy, the controller can also filter the sampled current data (low-pass filter) to eliminate high-frequency noise or instantaneous spike interference. Similarly, the controller can also perform moving average processing on multiple sampling results to smooth the instantaneous current value and obtain a stable effective value.

[0070] In this embodiment, three current sensors can be pre-arranged in the inverter module of the compressor to collect the instantaneous current values ​​of the U phase, V phase, and W phase respectively. The three-phase current data is directly obtained through hardware, without the need to derive the W phase current through calculation. The controller then calculates the instantaneous effective value I of the three-phase braking current based on the instantaneous current values ​​of the U phase, V phase, and W phase obtained by sampling. eff .

[0071] In this embodiment, the controller can also estimate the effective value of the braking current based on the back electromotive force. Specifically, it can be understood that the braking current is closely related to the back electromotive force, and the controller can estimate the effective value of the braking current by collecting the back electromotive force signal of the winding and combining the motor model parameters (winding inductance, resistance).

[0072] More specifically, the three-phase winding voltage is firstly acquired and the back electromotive force value is calculated.

[0073] The controller can then calculate the current effective value using the following formula:

[0074]

[0075] In the formula, E emf is the back electromotive force, R is the winding resistance, L is the winding inductance, and ω is the rotational speed angular frequency.

[0076] In this embodiment, the controller can also calculate the effective value of the braking current based on the power and voltage. Specifically, the braking power is closely related to the current and voltage, and the controller can indirectly calculate the effective value of the braking current by measuring the instantaneous voltage and power of the winding.

[0077] Step S144: Based on the effective value of the three-phase braking current, generate a PWM signal for controlling the inverter module; wherein, the larger the effective value of the three-phase braking current, the smaller the duty cycle of the generated PWM signal, so as to reduce the risk of current overshoot; the smaller the effective value of the three-phase braking current, the larger the duty cycle of the generated PWM signal, so as to enhance the braking effect.

[0078] In this embodiment, the effective value of the three-phase braking current can be analyzed in real time to dynamically adjust the duty cycle of the generated PWM signal to achieve precise control of the inverter module, thereby optimizing the braking effect.

[0079] In this embodiment, the controller can dynamically adjust the duty cycle of the PWM signal according to the size of the effective value of the three-phase braking current. For example, when the effective value of the three-phase braking current is large, the duty cycle of the PWM signal is reduced to reduce the overshoot of the braking current and protect the inverter module and the winding from damage. When the effective value of the three-phase braking current is small, the duty cycle of the PWM signal is increased to enhance the intensity of the braking current to improve the braking efficiency.

[0080] In this embodiment, the controller can dynamically adjust the duty cycle of the PWM signal according to the following formula:

[0081]

[0082] In the formula, D max is the maximum duty cycle (e.g. 50%), I max is the maximum safe braking current, I eff It is the effective value of three-phase braking current.

[0083] In this embodiment, in order to simplify the calculation, several fixed duty cycles corresponding to the current ranges can be preset. For example, when the effective value of the three-phase braking current is greater than 10A, the duty cycle is 5%. When the effective value of the three-phase braking current is between 5A and 10A, the duty cycle is 20%. When the effective value of the three-phase braking current is between 1A and 5A, the duty cycle is 50%.

[0084] Step S146: sending the PWM signal to the inverter module.

[0085] In this embodiment, when the inverter module is a three-phase full-bridge inverter, the three-phase full-bridge inverter is usually composed of three groups of bridge arms, each of which includes an upper bridge arm switch (such as Figure 4 As shown in , Q1, Q3, Q5) and a lower arm switch (such as Figure 4 Therefore, sending the PWM signal to the inverter module can be represented as the controller outputting the generated PWM signal through the PWM channel to the driving port of the lower bridge arm switch, so that it is turned on and off according to the set duty cycle. Accordingly, the controller can output the PWM signal to the upper bridge arm switch (such as Figure 4 As shown in , Q1, Q3, Q5) send a constant low-level signal to ensure that they are in the off state. Therefore, when the lower bridge arm is turned on at the same time, the three-phase winding is short-circuited to form a braking current, while the upper bridge arm is turned off to avoid the risk of short circuit.

[0086] In this embodiment, when the inverter module is a three-phase half-bridge inverter, each phase of the three-phase half-bridge inverter includes only a single switch, which controls the states of the U-phase, V-phase and W-phase windings respectively. Therefore, the controller can output signals to the driving port of the single switch through three PWM channels. For example:

[0087] PWM1: controls the U-phase switch.

[0088] PWM2: controls the V phase switch.

[0089] PWM3: Controls the W-phase switch.

[0090] Since the short circuit needs to be continuously turned on, the duty cycle of the generated PWM signal can be 100% (high level).

[0091] In this embodiment, when the inverter module is a multi-phase inverter. The multi-phase inverter is composed of multiple bridge arms (such as 10 bridge arms for five phases), and each phase includes an upper bridge arm switch and a lower bridge arm switch. Therefore, the controller can send a duty cycle control signal to each lower bridge arm switch through multiple PWM channels. For example:

[0092] PWM1-PWM5: control the lower arm switches of the five-phase windings respectively.

[0093] The frequency and duty cycle of each PWM signal remain consistent (eg, a fixed duty cycle of 50%).

[0094] Accordingly, the controller can send a low level signal to all upper bridge arm switches through the PWM channel.

[0095] This embodiment determines the effective value of the current three-phase braking current in real time, dynamically adjusts the duty cycle of the generated PWM signal according to the current size, and sends the signal to the inverter module to achieve precise control of the conduction state of the inverter module. Specifically, when the effective value of the three-phase braking current is large, the duty cycle of the PWM signal is reduced to limit the peak value of the braking current, thereby reducing the risk of current overshoot and protecting the safety of the inverter module and related components; when the effective value of the three-phase braking current is small, the duty cycle of the PWM signal is increased to increase the intensity of the braking current and enhance the braking effect. This method can dynamically adjust the control signal according to the braking state to ensure that the compressor speed is steadily reduced, which not only improves the braking efficiency, but also effectively reduces the risk of system failure, and significantly improves the safety and reliability of the compressor startup process.

[0096] In some implementations, the step of determining the current effective value of the three-phase braking current includes:

[0097] Step S1422: respectively sampling the U-phase current value and the V-phase current value of the compressor through a preset current sensor module.

[0098] In this embodiment, the current sensor module may be a Hall effect sensor, a shunt resistor sensor, a mutual inductor, and the like.

[0099] In this embodiment, the current sensor module may further include a U-phase current sensor and a V-phase current sensor. The U-phase current sensor is arranged on the circuit path connecting the U-phase winding and the inverter module. The V-phase current sensor is arranged on the circuit path connecting the V-phase winding and the inverter module.

[0100] Each sensor is connected to the ADC channel of the controller (DSP) and the analog signal is converted into a digital signal through the analog-to-digital conversion module.

[0101] In this embodiment, the controller can collect instantaneous current signals from the current sensors of phases U and V at regular intervals according to a preset sampling period. The instantaneous current signals obtained by each sampling can be stored in a memory of the controller in a digital form.

[0102] In some cases, the sampled raw current signal may be interfered by noise, so the controller can perform digital filtering on the sampled data, such as moving average filtering or Kalman filtering, to further smooth the signal.

[0103] Step S1424: Based on the current balance condition that the sum of the three-phase currents is zero, the W-phase current value is calculated using the U-phase current value and the V-phase current value.

[0104] In this embodiment, the controller can be based on the current balance relationship, that is, the characteristic that the sum of the three-phase currents is zero:

[0105] I U +I V +I W =0

[0106] In the formula, I U Expressed as the instantaneous current value of phase U, I V Expressed as the instantaneous current value of phase V, I W Indicated as the instantaneous current value of W phase.

[0107] Therefore, the instantaneous current value of phase W is calculated by the following formula:

[0108] I W =-(I U +I V )

[0109] Step S1426: Based on the U-phase current value, the V-phase current value and the W-phase current value, the current three-phase braking current effective value is calculated.

[0110] In this embodiment, the three-phase instantaneous current value I U , I V and I W , calculate the instantaneous effective value of the three-phase braking current I eff The effective value of the three-phase braking current can be defined as the root mean square value of the three-phase current:

[0111]

[0112] This implementation method calculates the W-phase current value by sampling the U-phase and V-phase current values ​​of the compressor and using the current balance condition that the sum of the three-phase currents is zero, thereby avoiding the need for direct sampling of the W-phase current and reducing hardware cost and complexity. On this basis, the effective value of the current three-phase braking current is obtained based on the root mean square calculation of the three-phase current, providing an accurate basis for subsequent PWM signal generation. This method combines the current balance principle to ensure the accuracy of the current effective value calculation, while reducing the need for the use of additional sensors and improving the economy and reliability of the system.

[0113] In some implementations, the step of generating a PWM signal for controlling the inverter module based on the three-phase braking current effective value includes:

[0114] Step S14262: When the effective value of the three-phase braking current is greater than the first current threshold, a PWM signal is generated for controlling the conduction of the lower bridge arm of the inverter module and the duty cycle is a first preset value to reduce the strength of the PWM signal, thereby forming a three-phase short-circuit state of the compressor.

[0115] In this implementation, the first current threshold may be 10A, 12A or 15A, etc., which may be a relatively large current value.

[0116] In this embodiment, the first preset value may be a relatively low value, such as a relatively low duty cycle, such as 5%, 6% or 7%.

[0117] In this embodiment, when the controller determines that the effective value of the three-phase braking current is greater than the first current threshold, the controller may first determine the duty cycle to be a first preset value (e.g., 5%). Next, the controller sets the frequency of the PWM signal, for example, 10kHz or higher, to ensure that the compressor runs smoothly and reduces noise. Finally, the controller (DSP) generates a PWM waveform according to the set frequency and duty cycle using its built-in PWM module. The controller may send the generated PWM signal to the lower arm switch drive port (Q2, Q4, Q6) of the inverter module. Accordingly, at the same time, the controller sends a constant low-level signal to the upper arm switch (Q1, Q3, Q5) of the inverter module to ensure that the upper arm is completely closed to avoid the risk of short circuit. When the lower arm switch is periodically turned on, the three-phase winding of the compressor is short-circuited to form a closed loop. In the short-circuited state, the back electromotive force drives the braking current to flow through the winding, and the braking current and the rotor inertia act to generate a reverse electromagnetic torque, gradually reducing the speed.

[0118] Step S14264: When the effective value of the three-phase braking current is between the first current threshold and the second current threshold, a PWM signal is generated for controlling the conduction of the lower bridge arm of the inverter module and the duty cycle is a second preset value to balance the braking effect and current stability; wherein the second current threshold is less than the first current threshold; and the second preset value is greater than the first preset value.

[0119] In this embodiment, the second current threshold may be a value between zero and the first current threshold, for distinguishing a lower current range from a higher current range. If the first current threshold is 10A, the second current threshold may be 5A, 6A or 5.5A, etc.

[0120] In this embodiment, when the effective value of the three-phase braking current is between the first current threshold and the second current threshold, the controller can appropriately increase the duty cycle of the PWM signal so that the braking current is neither too large to avoid system overshoot nor too small to maintain the speed deceleration effect.

[0121] In this embodiment, the second preset value may be a value higher than the first preset value, and may be a moderate duty cycle, such as 10%, 12% or 15%.

[0122] Step S14266: When the effective value of the three-phase braking current is between the second current threshold and the third current threshold, a PWM signal is generated for controlling the conduction of the lower bridge arm of the inverter module and the duty cycle is a third preset value to enhance the braking effect; wherein the third current threshold is less than the second current threshold; and the third preset value is greater than the second preset value.

[0123] In this implementation, the third current threshold may be a value lower than the second current threshold.

[0124] Specifically, it can be:

[0125] I3 <I2<I1

[0126] In the formula, I3 may be the third current threshold, I2 may be the second current threshold, and I1 may be the first current threshold.

[0127] For example, if I1 is 10A, I2 can be 5A, and I3 can be 1A.

[0128] In this embodiment, the third current threshold value may reflect the critical value of the system entering the braking completion stage, ensuring that the braking effect can smoothly transition to a stop state.

[0129] In this implementation, the third current threshold may correspond to a lower rotation speed range (a current value when the rotation speed is close to zero but not completely stopped).

[0130] In this embodiment, the third preset value may be a larger duty cycle, for example, 50%, etc. It is understandable that a higher duty cycle increases the on-time, increases the intensity of the braking current, and thus accelerates the reduction of the rotation speed.

[0131] This embodiment realizes precise control of the lower bridge arm of the inverter module by dynamically adjusting the duty cycle of the generated PWM signal based on the effective value of the three-phase braking current, and optimizes the current and speed regulation effect during the braking process. Specifically, when the effective value of the braking current is large, a PWM signal with a duty cycle of the first preset value is generated to reduce the strength of the PWM signal, thereby limiting current overshoot and protecting system components; when the effective value of the braking current is between the first current threshold and the second current threshold, a PWM signal with a duty cycle of the second preset value is generated to balance the braking effect and current stability; when the effective value of the braking current is small, a PWM signal with a duty cycle of the third preset value is generated to enhance the braking effect and accelerate the speed reduction. By adjusting the duty cycle in sections, this embodiment achieves a dynamic balance between the braking effect and the system safety within different current ranges, which not only improves the braking efficiency, but also reduces the loss risk of the inverter module, providing a stable foundation for the subsequent successful start-up of the compressor.

[0132] In some implementations, before the step of determining the current effective value of the three-phase braking current, the method further includes:

[0133] A first initial PWM signal is generated and sent to a preset inverter module; wherein the first initial PWM signal is a signal that turns off the upper bridge arm in the inverter module.

[0134] In this embodiment, the first initial PWM signal may be a control signal for controlling the upper bridge arm switches (Q1, Q3, Q5) in the inverter module to be turned off. The purpose is to ensure that the upper bridge arm is in a completely closed state to prevent the upper bridge arm from being turned on at the same time as the lower bridge arm and causing a short circuit risk, and to establish safe electrical conditions for the conduction of the lower bridge arm and the short circuit of the winding.

[0135] In this embodiment, the first initial PWM signal may be a low-level signal. Specifically, if GPIO control is adopted, a constant low-level signal may be directly output. If PWM control is adopted, the duty cycle is set to 0%, which is equivalent to completely shutting down the upper bridge arm.

[0136] In this implementation, the controller (DSP) generates a first initial PWM signal through a PWM module or a GPIO port, and directly outputs the first initial PWM signal to the control end of the upper bridge arm of the inverter module during the initialization phase.

[0137] In this embodiment, the inverter module may be a three-phase full-bridge inverter. It is understandable that each upper bridge arm (Q1, Q3, Q5) of the three-phase full-bridge inverter corresponds to a control channel:

[0138] PWM1: controls the U-phase upper bridge arm (Q1);

[0139] PWM2: controls the upper bridge arm of V phase (Q3);

[0140] PWM3: controls the W-phase upper bridge arm (Q5).

[0141] The controller sends the first initial PWM signal to the driving circuit of the upper bridge arm of the inverter module through the above-mentioned control channel to ensure stable signal transmission.

[0142] A second initial PWM signal is generated and sent to a preset inverter module; wherein the second initial PWM signal is a PWM signal that turns on the lower bridge arm of the inverter module and has a duty cycle of the first preset value.

[0143] In this implementation, the second initial PWM signal may be a periodic pulse signal, a high level of which is used to control the lower bridge arm switch to be turned on, and a low level of which is used to control the lower bridge arm switch to be turned off.

[0144] In this embodiment, the duty cycle of the second initial PWM signal can be directly the first preset value. From the above, it can be known that the first preset value can be a lower duty cycle (such as 5% to 10%) to limit the risk of braking current overshoot.

[0145] This embodiment initializes the working state of the inverter module in advance by sequentially generating the first initial PWM signal and the second initial PWM signal before the step of determining the current three-phase braking current effective value. The first initial PWM signal turns off the upper bridge arm of the inverter module to avoid the risk of short circuit and create a safe condition for the conduction of the lower bridge arm; the second initial PWM signal controls the conduction of the lower bridge arm with a duty cycle of the first preset value to form the initial short-circuit state of the three-phase winding of the compressor and establish a stable braking current foundation. Through this method, the braking working state can be quickly established before entering the current effective value detection step, reducing system delays, ensuring the accuracy and reliability of subsequent current sampling and control, thereby improving the stability and efficiency of the entire braking and starting process.

[0146] In some embodiments, when the effective value of the three-phase braking current is greater than the first current threshold, the step of generating a PWM signal for controlling the lower bridge arm of the inverter module to be turned on and having a duty cycle of a first preset value includes:

[0147] When the effective value of the three-phase braking current is greater than the first current threshold, a preset time is first delayed, and then a PWM signal for controlling the lower bridge arm of the inverter module to be turned on and having a duty cycle of a first preset value is generated.

[0148] In this embodiment, the preset time can be expressed as a fixed time that the controller actively delays before generating a PWM signal for controlling the conduction of the lower bridge arm of the inverter module and having a duty cycle of the first preset value after detecting that the effective value of the three-phase braking current is greater than the first current threshold.

[0149] For example, the preset time may be 1 second. It is understandable that the inverter module needs a certain amount of time to complete the state switching, especially to ensure that the upper bridge arm is completely closed to prevent short circuit. 1 second can fully cover most hardware response requirements.

[0150] This embodiment effectively avoids the current shock and component damage that may be caused by too fast state switching in the early stage of braking by first delaying a preset time and then generating a PWM signal for controlling the conduction of the lower bridge arm of the inverter module with a duty cycle of the first preset value when the effective value of the three-phase braking current is greater than the first current threshold. The delay mechanism allows the inverter module to have sufficient time to complete the state stabilization after receiving the control signal, and ensures that the upper bridge arm is completely closed, thereby preventing the risk of short circuit caused by the simultaneous conduction of the upper and lower bridge arms. In addition, the delay operation provides sufficient dissipation time for the residual current and electromagnetic oscillation in the compressor winding, reduces the impact of interference on the accuracy of subsequent PWM signals, further improves the stability and safety of the braking process, and ensures the reliable operation of the system.

[0151] This embodiment provides a control system for a compressor, which may include:

[0152] An inverter module is used to drive the compressor.

[0153] In this embodiment, the inverter module may be a three-phase full-bridge inverter module. The three-phase full-bridge inverter module may be composed of three groups of upper and lower bridge arms, each group of bridge arms including an upper bridge arm switch (such as Q1, Q3, Q5) and a lower bridge arm switch (such as Q2, Q4, Q6). Accordingly, IGBT or MOSFET may be used as a switching device.

[0154] In this implementation, the inverter module may also be a three-phase half-bridge inverter module.

[0155] In this embodiment, the inverter module may also be a multi-phase inverter module.

[0156] In this implementation, the inverter module may also be a single-phase inverter module.

[0157] A controller is used to determine whether the current compressor rotor has inertial rotation before the compressor enters closed-loop startup, and when it is determined that inertial rotation exists, generate a control signal and send it to the inverter module; wherein the inverter module is an inverter module for driving the compressor, and the control signal is used to control the on and off of the inverter module so that the three-phase winding of the compressor is short-circuited to reduce the speed of the compressor rotor, and when it is detected that the speed of the compressor rotor is lower than a preset threshold, execute a preset closed-loop startup strategy to complete the closed-loop startup of the compressor.

[0158] In this embodiment, the controller may be a digital signal processor (DSP).

[0159] In this embodiment, the controller may be a microcontroller unit (MCU).

[0160] In this embodiment, the controller may be a programmable logic controller (PLC).

[0161] In this embodiment, the controller may be a field programmable gate array (FPGA).

[0162] In this embodiment, the controller may be an embedded controller.

[0163] The compressor control system provided in this embodiment realizes efficient control of the compressor startup process through the coordinated work of the controller and the inverter module. Before entering the closed-loop startup, the controller first determines whether the rotor has inertial rotation, and when inertial rotation is detected, it generates a control signal to control the inverter module to short-circuit the three-phase winding to slow down the rotor speed. Through this process, the problem of closed-loop startup failure caused by inertial rotation is effectively solved. At the same time, when the speed drops below the preset threshold, the closed-loop startup strategy is executed to ensure smooth and reliable startup. The system can dynamically adapt to the initial state of the rotor, reduce the risk of current overshoot and startup failure, improve the startup efficiency of the compressor and the overall reliability of the system, and provide a safe and efficient control solution for compressor operation under complex working conditions.

[0164] In some embodiments, the control system further comprises:

[0165] A current sensor module is used to sample the U-phase current value and the V-phase current value of the compressor; wherein the U-phase current value and the V-phase current value are input into the controller, so that the controller determines the current three-phase braking current effective value based on the U-phase current value and the V-phase current value, and the three-phase braking current effective value can instruct the controller to generate a PWM signal for controlling the inverter module; wherein, the larger the effective value of the three-phase braking current, the smaller the duty cycle of the generated PWM signal, so as to reduce the risk of current overshoot; the smaller the effective value of the three-phase braking current, the larger the duty cycle of the generated PWM signal, so as to enhance the braking effect.

[0166] In this embodiment, the current sensor module may be a Hall effect current sensor.

[0167] In this embodiment, the current sensor module may be a shunt resistor current sensor.

[0168] In this implementation, the current sensor module may be a current transformer.

[0169] In this embodiment, the current sensor module may be an integrated current sensor.

[0170] This implementation introduces a current sensor module to sample the U-phase current value and V-phase current value of the compressor in real time, and inputs it into the controller, and uses the current balance relationship to calculate the effective value of the current three-phase braking current. The controller dynamically generates a PWM signal based on the effective value and adjusts its duty cycle to adapt to the actual braking demand. When the effective value of the three-phase braking current is large, the duty cycle of the PWM signal is reduced to reduce the risk of current overshoot and protect the inverter module and system components; when the effective value of the three-phase braking current is small, the duty cycle of the PWM signal is increased to enhance the braking effect and accelerate the rotor inertia deceleration process. This method realizes the closed-loop linkage of current sampling, calculation and control, effectively improves the safety, stability and adaptability of the braking process, and provides reliable guarantee for the efficient startup and operation of the compressor under complex working conditions.

[0171] In one possible and specific embodiment, a method for starting a compressor is provided. Figure 3 , Figure 4 and Figure 5 As shown, the method can be applied to a compressor drive inverter. The compressor drive inverter may include: a three-phase AC input, which is used to provide the electric energy required to drive the compressor motor to operate. A rectifier circuit, which is located between the three-phase AC input and the inverter circuit, is responsible for converting the input three-phase AC power into DC power. It is used to rectify the AC power into DC power for use by the subsequent inverter module. The inverter circuit receives the DC input of the rectifier circuit and converts it into a three-phase AC output to drive the compressor. And it uses PWM signal modulation to convert the DC power into three-phase AC power with controllable frequency and amplitude. A DSP chip module, which generates a PWM signal and outputs it to the inverter circuit, which is used to control the operating state of the inverter module (the lower bridge arm is turned on or the upper bridge arm is turned off). And it can collect the compressor operating state (current, speed) in real time, and adjust the duty cycle and frequency of the PWM signal to achieve accurate speed and current control. The compressor is the load part, which receives the three-phase AC power output by the inverter circuit.

[0172] like Figure 4 As described, the method can be applied to the compressor inverter shown in the figure, and the inverter may include: six switching tubes Q1, Q2, Q3, Q4, Q5, and Q6, which may be IGBTs.

[0173] The six switch tubes form three groups of upper and lower bridge arms:

[0174] U-phase bridge arm: Q1 (upper bridge), Q2 (lower bridge);

[0175] V-phase bridge arm: Q3 (upper bridge), Q4 (lower bridge);

[0176] W phase bridge arm: Q5 (upper bridge), Q6 (lower bridge).

[0177] The power switch tube converts DC power into three-phase AC power with adjustable frequency and amplitude by turning it on and off according to the PWM control signal to drive the compressor.

[0178] The inverter may also include: six freewheeling diodes D1, D2, D3, D4, D5, and D6 connected in parallel with each switch tube for freewheeling protection. When the switch tube is turned off, the diode provides a freewheeling path for the load, protects the circuit from current shock, and ensures stable operation of the system.

[0179] The inverter may also include: two current sensors, respectively sampling the current signals of the U phase and the V phase. The two current sensors can monitor the output current in real time, provide feedback signals to the DSP module, and calculate the effective value of the three-phase current (calculate the W phase current through the current balance condition) to achieve closed-loop control.

[0180] The inverter can be connected to a DSP control module. The DSP control module is used to generate six PWM signals: DSP_PWM1, DSP_PWM2, DSP_PWM3, DSP_PWM4, DSP_PWM5 and DSP_PWM6.

[0181] The inverter can also be connected to a compressor motor.

[0182] like Figure 5 As shown, the compressor starting method may include:

[0183] The conventional startup method of the compressor is closed-loop startup and closed-loop operation. This startup method is generally compatible with low-load and high-load startup. However, when the compressor is shut down at the previous level, due to inertia, it still has a certain speed. When it is restarted before it stops completely, the speed estimation is inaccurate, and the compressor cannot start normally and switches to closed-loop operation, resulting in startup failure.

[0184] Since the three-phase output line of the three-phase compressor is short-circuited, the compressor braking effect can be achieved. The three-phase winding of the compressor will generate braking current, which will reduce the compressor speed and achieve the braking effect. Therefore, the software can add a braking and current detection stage before the compressor enters the closed-loop startup stage. Figure 4 As shown: by controlling the on and off of the three bridge arms Q2, Q4, and Q6 of the IGBT lower circuit, the three phases of the compressor are short-circuited, the compressor is braked, and the speed is reduced.

[0185] Since the compressor rotor itself is heavy and has large inertia, low-speed rotation will also generate a large braking current, so the three-way lower bridge drive signal with too large a duty cycle cannot be output, otherwise it will cause a large braking current overshoot and damage the components. Therefore, in this stage, it is necessary to add a current detection stage to calculate the effective value of the three-phase braking current through the two-phase current sampled by current sensor 1 and current sensor 2 and the three-phase current sum is 0.

[0186] like Figure 5 As shown in the figure, when the current is greater than 10A, a 5% drive signal is output, when it is 5A to 10A, a 20% drive signal is output, and when it is 1A to 5A, a 50% duty cycle drive signal is output. However, when the current is less than 1A, the speed is low, and the compressor closed-loop start can be started directly. The current sensor monitors the current generated by the compressor due to braking in real time, and a control closed loop is formed by controlling the IGBT conduction time, and finally the entire compressor speed start process is completed.

[0187] According to an embodiment of the present invention, a computer-readable storage medium is provided, on which a computer program is stored. When the computer program is executed by a computer, the computer executes the method described in any of the above embodiments.

[0188] According to an embodiment of the present invention, a computer program product including instructions is also provided. When the instructions are executed by a computer, the computer executes a method in any one of the above embodiments.

[0189] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application 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 interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device comprising a series of steps or units is not necessarily limited to those steps or units clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0190] Optionally, the specific examples in this embodiment may refer to the examples described in the above embodiments, and this embodiment will not be described in detail here.

[0191] The serial numbers of the above-mentioned embodiments of the present application are for description only and do not represent the advantages or disadvantages of the embodiments.

[0192] In the above embodiments of the present application, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant description of other embodiments.

[0193] The above is only a preferred implementation of the present application. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present application. These improvements and modifications should also be regarded as the scope of protection of the present application.

Claims

1. A method for starting a compressor, characterized in that: The method comprises: Before the compressor enters the closed-loop startup, determine whether the compressor rotor currently has inertial rotation; When it is determined that there is inertial rotation, a control signal is generated and sent to a preset inverter module; wherein the inverter module is an inverter module for driving the compressor, and the control signal is used to control the on and off of the inverter module so that the three-phase winding of the compressor is short-circuited to reduce the speed of the compressor rotor; When it is detected that the rotation speed of the compressor rotor is lower than a preset threshold, a preset closed-loop starting strategy is executed to complete the closed-loop starting of the compressor.

2. The method according to claim 1, characterized in that The control signal is a PWM signal, and the step of generating the control signal and sending it to a preset inverter module includes: Determine the current effective value of the three-phase braking current; Based on the effective value of the three-phase braking current, a PWM signal for controlling the inverter module is generated; wherein, the greater the effective value of the three-phase braking current, the smaller the duty cycle of the generated PWM signal is, so as to reduce the risk of current overshoot; the smaller the effective value of the three-phase braking current, the greater the duty cycle of the generated PWM signal is, so as to enhance the braking effect; The PWM signal is sent to the inverter module.

3. The method according to claim 2, characterized in that The step of determining the current three-phase braking current effective value comprises: The U-phase current value and the V-phase current value of the compressor are sampled respectively by a preset current sensor module; According to the current balance condition that the sum of the three-phase currents is zero, the W-phase current value is calculated using the U-phase current value and the V-phase current value; The current three-phase braking current effective value is calculated based on the U-phase current value, the V-phase current value and the W-phase current value.

4. The method according to claim 2, characterized in that: The step of generating a PWM signal for controlling the inverter module based on the three-phase braking current effective value comprises: When the effective value of the three-phase braking current is greater than the first current threshold, a PWM signal is generated for controlling the lower bridge arm of the inverter module to be turned on and the duty cycle is a first preset value, so as to reduce the strength of the PWM signal, thereby forming a three-phase short-circuited state of the compressor; When the effective value of the three-phase braking current is between the first current threshold and the second current threshold, a PWM signal for controlling the lower bridge arm of the inverter module to be turned on and having a duty cycle of a second preset value is generated to balance the braking effect and the current stability; wherein the second current threshold is less than the first current threshold; and the second preset value is greater than the first preset value; When the effective value of the three-phase braking current is between the second current threshold and the third current threshold, a PWM signal is generated for controlling the conduction of the lower bridge arm of the inverter module and having a duty cycle of a third preset value to enhance the braking effect; wherein the third current threshold is less than the second current threshold; and the third preset value is greater than the second preset value.

5. The method according to claim 4, characterized in that Before the step of determining the current three-phase braking current effective value, the method further includes: Generate a first initial PWM signal and send it to a preset inverter module; wherein the first initial PWM signal is a signal that turns off the upper bridge arm in the inverter module; A second initial PWM signal is generated and sent to a preset inverter module; wherein the second initial PWM signal is a PWM signal that turns on the lower bridge arm of the inverter module and has a duty cycle of the first preset value.

6. The method according to claim 5, characterized in that The step of generating a PWM signal for controlling the lower bridge arm of the inverter module to be turned on and having a duty cycle of a first preset value when the effective value of the three-phase braking current is greater than the first current threshold comprises: When the effective value of the three-phase braking current is greater than the first current threshold, a preset time is first delayed, and then a PWM signal for controlling the lower bridge arm of the inverter module to be turned on and having a duty cycle of a first preset value is generated.

7. A control system for a compressor, characterized in that: include: An inverter module, used for driving the compressor; A controller is used to determine whether the current compressor rotor has inertial rotation before the compressor enters closed-loop startup, and when it is determined that inertial rotation exists, generate a control signal and send it to the inverter module; wherein the inverter module is an inverter module for driving the compressor, and the control signal is used to control the on and off of the inverter module so that the three-phase winding of the compressor is short-circuited to reduce the speed of the compressor rotor, and when it is detected that the speed of the compressor rotor is lower than a preset threshold, execute a preset closed-loop startup strategy to complete the closed-loop startup of the compressor.

8. The control system according to claim 7, characterized in that: Also includes: A current sensor module is used to sample the U-phase current value and the V-phase current value of the compressor; wherein the U-phase current value and the V-phase current value are input into the controller, so that the controller determines the current three-phase braking current effective value based on the U-phase current value and the V-phase current value, and the three-phase braking current effective value can instruct the controller to generate a PWM signal for controlling the inverter module; wherein, the larger the effective value of the three-phase braking current, the smaller the duty cycle of the generated PWM signal, so as to reduce the risk of current overshoot; the smaller the effective value of the three-phase braking current, the larger the duty cycle of the generated PWM signal, so as to enhance the braking effect.

9. A compressor, characterized in that: The compressor comprises a controller, and the controller is used to execute the method described in any one of claims 1-6 or the control system described in any one of claims 7-8.

10. An air conditioner, characterized in that: The air conditioner comprises a controller, and the controller is used to execute the method described in any one of claims 1-6 or the control system described in any one of claims 7-8.

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