Power supply control system and compressor

Abstract

The application discloses a power supply control system and a compressor, and relates to the technical field of power supply control systems, in particular to a power supply control system and a compressor. The power supply control system comprises a first power supply circuit connected with a three-phase power supply and used for supplying power to a three-phase motor, and a second power supply circuit used for supplying power to an electronic expansion valve. The second power supply circuit adjusts its on-off state according to the voltage change rate in the first power supply circuit, and the off time of the second power supply circuit is later than the off time of the first power supply circuit. Compared with the prior art, the application can still provide air pressure for the compressor rotor through an air pump for a period of time after the frequency converter stops working, so that friction accidents can be avoided during the speed reduction process, and the stability and reliability of the system are ensured.

Description

Technical Field

[0001] This invention relates to frequency conversion technology and microelectronics technology, and in particular to a power supply control system and a compressor. Background Technology

[0002] A frequency converter is a power control device that uses frequency conversion technology and microelectronics technology to control an AC motor by changing the frequency of the motor's power supply.

[0003] Air suspension compressors are a mature product on the market that is energy-saving, efficient, and inexpensive. They are divided into two types: static pressure air suspension compressors and dynamic pressure air suspension compressors. In dynamic pressure air suspension compressors, the bearings are suspended by the air pressure generated by the high-speed rotation of the rotor bearings. In static pressure air suspension compressors, the bearings are suspended by the air pressure provided by an external air pump.

[0004] Integrating the frequency converter and compressor into one unit can significantly save costs and reduce product size. However, since the static pressure air suspension compressor still needs to provide air pressure before starting and after stopping to suspend the compressor rotor bearing and prevent it from rubbing against the wall during rotation and causing damage, the power supply system needs to be designed to ensure that it can still supply power to the air pump even in emergency shutdown.

[0005] Therefore, how to design a power supply control system and compressor to prevent friction damage to the compressor rotor shaft during rotation is a technical problem that the industry urgently needs to solve. Summary of the Invention

[0006] In view of the problem of friction damage to the rotor shaft of compressors in the prior art, the present invention proposes a power supply control system and a compressor.

[0007] The technical solution of the present invention is to propose a power supply control system, including a first power supply circuit connected to a three-phase power supply and supplying power to a three-phase motor, and a second power supply circuit supplying power to an electronic expansion valve. The second power supply circuit adjusts its on / off state according to the voltage change rate in the first power supply circuit, and the off time of the second power supply circuit is later than the off time of the first power supply circuit.

[0008] Furthermore, the first power supply circuit includes:

[0009] A three-phase full-bridge circuit has a first bridge arm, a second bridge arm, and a third bridge arm, wherein the first bridge arm, the second bridge arm, and the third bridge arm are respectively connected to the three-phase output of the three-phase power supply, for converting the AC power output of the three-phase power supply into DC power.

[0010] A bus capacitor is connected to the output terminal of the three-phase full-bridge circuit to store the DC output of the three-phase full-bridge circuit.

[0011] An inverter is connected to both ends of the bus capacitor to convert the DC power output from the bus capacitor into three-phase AC power and supply power to the three-phase motor.

[0012] Furthermore, the second power supply circuit includes:

[0013] A flyback switching power supply is connected to the three-phase power supply and the electronic expansion valve respectively, for drawing power from the three-phase power grid and supplying power to the electronic expansion valve;

[0014] A backup power supply is provided, which is connected to the three-phase power supply and the flyback switching power supply respectively, and is used to supply power to the flyback switching power supply when the three-phase power supply is de-energized.

[0015] Furthermore, it also includes a circuit breaker connected in series between the first power supply circuit and the three-phase power supply, a first sampling resistor connected between the circuit breaker and the first power supply circuit, and a second sampling resistor and a third sampling resistor connected between the circuit breaker and the three-phase power supply. The second power supply circuit adjusts its on / off state by the voltage change rate on the first sampling resistor.

[0016] Furthermore, when the rate of change of voltage across the first sampling resistor is greater than a preset slope, the backup power supply is activated and supplies power to the flyback switching power supply.

[0017] When the rate of change of voltage across the first sampling resistor is less than a preset slope, the backup power supply stops supplying power to the flyback switching power supply.

[0018] Furthermore, it also includes a DSP controller connected to the inverter. The DSP controller is connected in the second power supply circuit and is used to control the on / off state of the inverter to adjust the power supply state of the three-phase motor.

[0019] The DSP controller is also connected to an emergency stop switch, which disconnects the circuit breaker when the emergency stop switch is triggered.

[0020] Furthermore, when the rate of change of voltage across the first sampling resistor fluctuates, the backup power supply adjusts the output voltage based on the voltages across the second and third sampling resistors.

[0021] Furthermore, when the voltage difference between the second sampling resistor and the third sampling resistor is greater than a preset voltage, the backup power supply outputs AC power with the same waveform as the three-phase power supply.

[0022] When the voltage difference between the second sampling resistor and the third sampling resistor is zero, the backup power supply outputs 380V AC power at 50Hz.

[0023] Furthermore, the first sampling resistor, the second sampling resistor, and the third sampling resistor are connected in different phases of the three-phase power supply.

[0024] The present invention also proposes a compressor having the above-described power supply control system.

[0025] Compared with the prior art, the present invention has at least the following beneficial effects:

[0026] 1. This invention can ensure uninterrupted normal operation of the power load in the event of an emergency shutdown of a three-phase motor due to a fault or a power outage of the three-phase power supply. It has high reliability and strong anti-interference ability.

[0027] 2. In this invention, even when the frequency converter stops working for a period of time, the compressor rotor can still be supplied with air pressure by an air pump, thus avoiding shaft friction accidents during the deceleration process.

[0028] 3. In the event of voltage fluctuations such as lightning surges, this invention can adjust the output voltage of the backup power supply to synchronize with the voltage of the three-phase power supply, effectively preventing the occurrence of circulating current and improving the safety of the system. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of the present invention, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0030] Figure 1 This is a schematic diagram of the overall circuit principle of the present invention;

[0031] Figure 2 This is a schematic diagram of the overall control principle of the present invention. Detailed Implementation

[0032] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the present invention and are not intended to limit the present invention.

[0033] Therefore, a feature pointed out in this specification is used to describe one feature of one embodiment of the invention, and does not imply that every embodiment of the invention must have the described feature. Furthermore, it should be noted that this specification describes many features. Although certain features may be combined to illustrate possible system designs, these features may also be used in other combinations not explicitly stated. Therefore, unless otherwise stated, the described combinations are not intended to be limiting.

[0034] The principles and structure of the present invention will be described in detail below with reference to the accompanying drawings and embodiments.

[0035] Air-suspension compressors are a mature, energy-efficient, and low-cost product currently on the market. They are divided into static pressure air-suspension compressors and dynamic pressure air-suspension compressors. Static pressure air-suspension compressors use an external air pump to supply air pressure, suspending the bearings. However, in an emergency shutdown, if the air pump stops supplying air pressure, friction will occur between the compressor's rotor shaft and the wall, leading to damage. The idea behind this invention is to design two power supply circuits: one for a three-phase motor and the other for an electronic expansion valve. The electronic expansion valve is used for air pressure supply. By ensuring that the power supply circuit for the electronic expansion valve is turned off later than the power supply circuit for the three-phase motor, the friction problem between the rotor shaft and the wall is avoided.

[0036] Specifically, the power supply control system proposed in this invention includes:

[0037] The first power supply circuit is connected between the three-phase power supply and the three-phase motor. It is used to draw power from the three-phase power supply and supply power to the three-phase motor to ensure the operation of the compressor.

[0038] The second power supply circuit is connected between the three-phase power supply and the electronic expansion valve. It is used to draw power from the three-phase power supply and supply power to the electronic expansion valve to ensure the suspension of the rotor shaft.

[0039] Among them, the electronic expansion valve is a control valve connected between the various pipes of the compressor. Only when the electronic expansion valve is powered on can the air pump control the rotor shaft to levitate normally, thereby avoiding friction between the rotor shaft and the wall.

[0040] In this invention, the second power supply circuit adjusts its on / off state according to the voltage change rate in the first power supply circuit, and the off time of the second power supply circuit is later than the off time of the first power supply circuit. Under this control method, after the first power supply circuit is de-energized, the three-phase motor stops working. At this time, the second power supply circuit is still in the power supply state, and the rotor shaft is in a suspended state, avoiding friction between the rotor shaft rotation and the wall.

[0041] Please see Figure 1 The first power supply circuit proposed in this invention includes:

[0042] A three-phase full-bridge circuit has a first bridge arm, a second bridge arm, and a third bridge arm, and the first bridge arm, the second bridge arm, and the third bridge arm are respectively connected to the three-phase output of a three-phase power supply, for converting the AC power output of the three-phase power supply into DC power.

[0043] A bus capacitor is connected to the output terminal of the three-phase full-bridge circuit to store the DC output of the three-phase full-bridge circuit.

[0044] An inverter, connected to both ends of the bus capacitor, is used to convert the DC power output from the bus capacitor into three-phase AC power to supply power to the three-phase motor.

[0045] The first bridge arm consists of diodes D1 and D2, the second bridge arm consists of diodes D3 and D4, and the third bridge arm consists of diodes D5 and D6. The three phases of the three-phase power supply are connected to the midpoints of the first, second, and third bridge arms, respectively. During operation, diodes D1, D2, D3, D4, D5, and D6 form a three-phase full-bridge circuit that acts as a rectifier, converting the AC power output from the three-phase power supply into DC power.

[0046] Bus capacitor is Figure 1 The capacitor C in the circuit is connected to the output of the three-phase full-bridge circuit. It is used to obtain the DC power output from the three-phase full-bridge circuit and store energy, which can avoid energy waste to a certain extent. The other side of the bus capacitor is connected to the two ends of the inverter. The inverter is used to convert the DC power into three-phase AC power and supply power to the three phases of the three-phase motor, thereby ensuring the normal operation of the three-phase motor. In this invention, the inverter can also be a three-phase full-bridge circuit, in which each bridge arm uses a power switch, and the on / off state of each power switch is controlled by a DSP controller. By adjusting the on / off state of each power switch, the voltage output to the three-phase motor is adjusted, thereby regulating the operating state of the three-phase motor.

[0047] Furthermore, the second power supply circuit includes:

[0048] A flyback switching power supply is connected to a three-phase power supply and an electronic expansion valve respectively. It is used to draw power from the three-phase power grid and supply power to the electronic expansion valve.

[0049] A backup power supply is connected to both the three-phase power supply and the flyback switching power supply, and is used to supply power to the flyback switching power supply when the three-phase power supply fails.

[0050] like Figure 1 In this invention, the flyback power supply, also known as a single-ended flyback DC-DC converter, stores energy but does not transfer it during the main switch's on-time. Energy is only transferred to the load during the main switch's off-time. In this invention, the three-phase power supply powers the electronic expansion valve via the flyback power supply, ensuring the air pump's operation. Furthermore, the flyback power supply is also connected to the DSP controller to power it, ensuring the inverter's operation.

[0051] The backup power supply is a UPS (Uninterruptible Power Supply), which is a constant voltage and frequency uninterruptible power supply containing an energy storage device and with an inverter as its main component. When the three-phase power supply is interrupted (power outage), it can immediately supply the internally stored electrical energy to the load through inversion, enabling the load to maintain normal operation and protecting the load's hardware and software from damage. It provides protection for equipment subjected to both overvoltage and undervoltage.

[0052] In this invention, a backup power supply powers the flyback switching power supply when the three-phase power supply fails, preventing the second power supply circuit from immediately shutting off and delaying the closing time of the electronic expansion valve. Furthermore, the backup power supply duration can be designed based on the compressor rotor shaft's stop rotation time, ensuring it is slightly longer than the rotor shaft's rotation time. This means the air pump's start-up time is slightly longer than the rotor shaft's rotation time, preventing rotor shaft friction issues and minimizing voltage fluctuations, thus ensuring no high-voltage current flows within the system.

[0053] Please see Figure 1 The present invention also includes a circuit breaker connected in series between the first power supply circuit and the three-phase power supply, a first sampling resistor connected between the circuit breaker and the first power supply circuit, and a second sampling resistor and a third sampling resistor connected between the circuit breaker and the three-phase power supply.

[0054] In this invention, the on / off state of the second power supply circuit is adjusted by the voltage change rate on the first sampling resistor. Since the first sampling resistor and the first power supply circuit are connected in series, the voltage change rate on the first sampling resistor can also reflect the voltage change rate on the first power supply circuit to a certain extent.

[0055] like Figure 1 In this circuit, the first sampling resistor is resistor Z1, the second sampling resistor is resistor Z2, and the third sampling resistor is resistor Z3. They are connected to different phases of the three-phase power supply, and the voltage in the first power supply circuit and the voltage difference between each phase of the three-phase power supply can be represented by the three sampling resistors respectively.

[0056] The control logic of this invention based on the voltage change rate across the first sampling resistor is as follows:

[0057] When the rate of change of voltage across the first sampling resistor is greater than the preset slope, the backup power supply starts and supplies power to the flyback switching power supply.

[0058] When the rate of change of voltage across the first sampling resistor is less than the preset slope, the backup power supply stops supplying power to the flyback switching power supply.

[0059] The preset slope only considers the frequency of voltage drop across the first sampling resistor, and the comparison only considers the magnitude of the slope, not its sign. In this invention, there are two situations that cause the static pressure air suspension compressor to stop suddenly: compressor malfunction and three-phase power failure.

[0060] In the first case, the three-phase power supply is normal, but the compressor stops and cannot operate. The present invention has an emergency stop switch connected to the DSP controller, which is used to trigger when the compressor fails, to remind the DSP controller of the compressor failure. At this time, the DSP controller will control the circuit breaker to open. Since the first sampling resistor is connected between the circuit breaker and the first power supply circuit, the voltage on it will drop rapidly to zero after the circuit breaker is opened. In this case, the voltage change rate on the first sampling resistor is greater than the preset slope.

[0061] In the second scenario, the three-phase power supply fails and cannot provide voltage output. At this time, the voltage on the first sampling resistor will also drop rapidly to zero. In this case, since the compressor has not triggered a fault, the circuit breaker is in the conducting state. Due to the lack of power supply voltage, the rate of change of voltage on the first sampling resistor will also be greater than the preset slope.

[0062] In this invention, when the voltage change rate on the first sampling resistor is greater than the preset slope, the backup power supply is activated and the flyback switching power supply is powered to ensure the normal operation of the electronic expansion valve. This ensures that the electronic expansion valve will be delayed in the event of compressor failure or three-phase power failure, so that the air pump will shut down after the compressor rotor shaft stops rotating, thus avoiding friction problems.

[0063] Furthermore, when voltage fluctuations such as lightning surges occur on the L1 line of the three-phase power supply, the output voltage of the three-phase power supply becomes unstable, causing voltage fluctuations. If the backup power supply is in operation at this time, its voltage will differ from the three-phase power supply voltage, resulting in a voltage difference between the backup power supply and the three-phase voltage. This can lead to circulating current, which may damage the backup power supply in severe cases. In this situation, the voltage across the first sampling resistor will fluctuate. The DSP controller uses this voltage fluctuation to determine if a lightning surge has occurred and adjusts the output voltage of the backup power supply based on the voltages across the second and third sampling resistors.

[0064] The method by which it adjusts the output voltage of the backup power supply based on the voltage across the second and third sampling resistors is as follows:

[0065] When the voltage difference between the second and third sampling resistors is not zero, the backup power supply outputs AC power with the same waveform as the three-phase power supply.

[0066] When the voltage difference between the second and third sampling resistors is zero, the backup power supply outputs 380V AC power at 50Hz.

[0067] When the voltage difference between the second and third sampling resistors is not zero, it indicates that there is a large voltage fluctuation in the three-phase power supply. Therefore, it is necessary to control the voltage of the backup power supply to be consistent with the waveform of the three-phase power supply. That is, the output voltage of the backup power supply should be the same as the output voltage of the three-phase power supply in terms of amplitude, frequency, and phase. Under this output voltage, the voltage difference between the three-phase power supply and the backup power supply is zero, and no circulating current will be generated, which can ensure the safety and reliability of the system.

[0068] When the voltage difference between the second and third sampling resistors is zero, it indicates that the three-phase power supply has no output voltage, meaning the three-phase power supply is interrupted. If the backup power supply maintains the same output as the three-phase power supply in this case, the flyback switching power supply will have no voltage input, causing the electronic expansion valve to de-energize. Therefore, in this situation, the backup power supply needs to output 50Hz 380V AC (the output voltage of the three-phase power supply under normal operating conditions) to ensure the normal operation of the electronic expansion valve. It should be noted that determining whether the three-phase power supply has no output voltage requires ensuring that the voltage difference between the second and third sampling resistors remains zero for a sustained period to avoid misjudgments caused by voltage fluctuations.

[0069] Please see Figure 2 The overall control flowchart of this invention is as follows: It determines whether the standby power supply (UPS) should supply power by checking whether the voltage change rate (dV / dT) on the sampling resistor Z1 (the first sampling resistor) is greater than a preset slope (X). Simultaneously, when the standby power supply is supplying power, it checks whether the voltage difference (Uz2-Uz3) between the second and third sampling resistors is zero, and adopts different power supply strategies based on the voltage difference between the second and third sampling resistors until the power supply time reaches a preset time (t1). It should be noted that this preset time is set based on the rotor shaft rotation time during the compressor's emergency stop state, and is generally set to be slightly longer than the rotor shaft rotation time.

[0070] The present invention also proposes a compressor that employs the aforementioned power supply control system.

[0071] Preferably, the compressor is a static pressure air suspension compressor.

[0072] Compared with existing technologies, this invention can ensure uninterrupted normal operation of the power load even when the three-phase motor shuts down due to a fault or when the three-phase power supply fails, exhibiting high reliability and strong anti-interference capability. Furthermore, this invention can still provide air pressure to the compressor rotor via an air pump even when the frequency converter is not operating for a period of time, preventing shaft friction accidents during speed reduction. In the event of voltage fluctuations such as lightning surges, this invention can adjust the output voltage of the backup power supply to synchronize with the three-phase power supply voltage, effectively preventing circulating current phenomena and improving system safety.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A power supply control system, characterized in that, It includes a first power supply circuit connected to a three-phase power supply and supplying power to a three-phase motor, and a second power supply circuit supplying power to an electronic expansion valve. The second power supply circuit adjusts its on / off state according to the voltage change rate in the first power supply circuit, and the off time of the second power supply circuit is later than the off time of the first power supply circuit. The second power supply circuit includes: A flyback switching power supply is connected to the three-phase power supply and the electronic expansion valve respectively, for drawing power from the three-phase power supply and supplying power to the electronic expansion valve; A backup power supply is connected to the three-phase power supply and the flyback switching power supply respectively, and is used to supply power to the flyback switching power supply when the three-phase power supply is de-energized. The power supply control system further includes a circuit breaker connected in series between the first power supply circuit and the three-phase power supply, a first sampling resistor connected between the circuit breaker and the first power supply circuit, and a second sampling resistor and a third sampling resistor connected between the circuit breaker and the three-phase power supply. The second power supply circuit adjusts its on / off state by the voltage change rate on the first sampling resistor. When the rate of change of voltage across the first sampling resistor is greater than the preset slope, the backup power supply is activated and supplies power to the flyback switching power supply. When the rate of change of voltage across the first sampling resistor is less than a preset slope, the backup power supply stops. Power is supplied to the flyback switching power supply.

2. The power supply control system according to claim 1, characterized in that, The first power supply circuit includes: A three-phase full-bridge circuit has a first bridge arm, a second bridge arm, and a third bridge arm, wherein the first bridge arm, the second bridge arm, and the third bridge arm are respectively connected to the three-phase output of the three-phase power supply, for converting the AC power output of the three-phase power supply into DC power. A bus capacitor is connected to the output terminal of the three-phase full-bridge circuit to store the DC output of the three-phase full-bridge circuit. An inverter is connected to both ends of the bus capacitor to convert the DC power output from the bus capacitor into three-phase AC power and supply power to the three-phase motor.

3. The power supply control system according to claim 1, characterized in that, It also includes a DSP controller connected to the inverter, the DSP controller being connected in the second power supply circuit and used to control the on / off state of the inverter to adjust the power supply state of the three-phase motor; The DSP controller is also connected to an emergency stop switch. When the emergency stop switch is triggered, the circuit breaker... disconnect.

4. The power supply control system according to claim 1, characterized in that, When the rate of change of voltage across the first sampling resistor fluctuates, the backup power supply adjusts the output voltage based on the voltage across the second and third sampling resistors.

5. The power supply control system according to claim 4, characterized in that, When the voltage difference between the second sampling resistor and the third sampling resistor is greater than the preset voltage, the backup power supply outputs AC power with the same waveform as the three-phase power supply. When the voltage difference across the second sampling resistor and the third sampling resistor is zero, the backup type The power supply outputs 380V AC power at 50Hz.

6. The power supply control system according to claim 1, characterized in that, The first sampling resistor, the second sampling resistor, and the third sampling resistor are connected in different phases of the three-phase power supply.

7. A compressor, characterized in that, The compressor has a power supply control system as described in any one of claims 1 to 6.

Images