Overcurrent protection control method and device for PFC circuit of air conditioner and storage medium

Abstract

The invention relates to the air conditioning technology, discloses an air conditioner PFC circuit overcurrent protection control method and device and a storage medium, solves the problem of overcurrent fault false alarm in the prior art, reduces the hardware cost, and improves the reliability and economical efficiency of a system. The method comprises the following steps: S1, acquiring the running frequency of a compressor, a bus voltage value and a PFC current value in real time; s2, the moment compensation state is controlled according to the collected compressor operation frequency; s3, controlling the on-off state of the PFC circuit according to the acquired bus voltage value; and S4, judging according to the collected PFC current value, and when the PFC current value reaches or exceeds a preset threshold value, judging whether to trigger PFC overcurrent protection or not by combining the current torque compensation state and the PFC circuit switch state. The invention is suitable for variable-frequency air conditioners.

Description

Technical Field

[0001] The present invention relates to air conditioning technology, and more particularly to an overcurrent protection control method, device and storage medium for an air conditioner PFC circuit. Background Art

[0002] PFC (Power Factor Correction) is an important technology used in power electronic devices such as air conditioners to improve the power factor and reduce harmonic pollution. The power factor is the ratio of the active power to the apparent power in an AC circuit. Improving the power factor helps reduce the flow of reactive power in the power grid, thereby improving the power grid transmission efficiency and reducing power losses. Inductive loads such as compressors and fan motors in air conditioners will cause the current and voltage to be out of sync during operation, resulting in a decrease in the power factor. The PFC circuit adjusts the current waveform to make it closer to the voltage waveform, thus effectively improving this problem.

[0003] In high-load operation scenarios of air conditioners, such as high-load heating scenarios, due to large indoor-outdoor temperature differences, large differences between the set target temperature and the actual indoor temperature, large room areas, or poor insulation performance, the compressor needs to operate for a long time and at high power to meet the heating requirements. At this time, if the input voltage is high, the following problems may occur:

[0004] (1) Abnormal working state of the PFC circuit: Since PFC has a boosting effect on rectifying the input voltage to the bus voltage, at high input voltages, in order to prevent the bus voltage from being too high, the control strategy will cause the PFC circuit to be intermittently turned off. During the PFC off period, due to the circuit characteristics, the input current may generate spikes.

[0005] (2) Ripple current amplification effect: If the user adjusts the indoor unit air volume to the low wind gear, the compressor will enter the high-load low-frequency operation area. Under this working condition, in order to maintain the stable operation of the compressor, the control needs to inject a large torque compensation current, and the input power also shows discontinuous pulsation. This pulsation of the output power will cause the ripple current of the DC voltage to increase, which will exacerbate the fluctuation of the power input current.

[0006] (3) False alarm fault problem: Due to the combined action of two factors, namely, the generation of spikes in the input current during the PFC off period and the increase in ripple current caused by torque compensation under low-frequency operation of the compressor, beat frequency oscillation is likely to occur, resulting in an increase in the instantaneous input current. This will be sampled by the PFC sampling resistor, and traditional air conditioner control strategies often do not fully consider the physical correlation between the PFC working state and the current spike, resulting in the current spike generated during the normal shutdown of the PFC circuit being misjudged as an overcurrent fault, thereby triggering unnecessary alarms or protection actions.

[0007] In addition, in terms of overcurrent protection, the existing technology (such as the invention with the application number CN201810564709.2) mainly improves the protection response speed by cutting off the circuit through hardware, but it has the defects of high hardware cost and inability to dynamically adapt to complex working conditions, and it cannot solve the above false alarm fault problem. Summary of the Invention

[0008] The technical problem to be solved by the present invention is: to propose an overcurrent protection control method, device and storage medium for an air conditioner PFC circuit, to solve the problem of false alarms of overcurrent faults in the existing technology, while reducing the hardware cost and improving the reliability and economy of the system.

[0009] The technical solution adopted by the present invention to solve the above technical problems is:

[0010] On the one hand, the present invention provides an overcurrent protection control method for an air conditioner PFC circuit, including the following steps:

[0011] S1. Real-time collect the compressor operating frequency, bus voltage value and PFC current value;

[0012] S2. Control the torque compensation state according to the collected compressor operating frequency;

[0013] S3. Control the PFC circuit switch state according to the collected bus voltage value;

[0014] S4. Make a judgment according to the collected PFC current value. When the PFC current value reaches or exceeds the preset threshold, combine the current torque compensation state and the PFC circuit switch state to determine whether to trigger the PFC overcurrent protection.

[0015] Further, in step S2, controlling the torque compensation state according to the collected compressor operating frequency includes:

[0016] When the compressor frequency ≤ the first frequency threshold, turn on the torque compensation;

[0017] When the compressor frequency > the second frequency threshold, turn off the torque compensation;

[0018] When the first frequency threshold < compressor frequency ≤ the second frequency threshold, keep the original torque compensation state.

[0019] Further, in step S3, controlling the PFC circuit switch state according to the collected bus voltage value includes:

[0020] When the bus voltage value < the first voltage threshold, turn on the PFC circuit;

[0021] When the bus voltage value ≥ the second voltage threshold, turn off the PFC circuit;

[0022] When the first voltage threshold ≤ bus voltage value < the second voltage threshold, maintain the original state of the PFC circuit.

[0023] Further, in step S4, the determining whether to trigger PFC overcurrent protection by combining the current torque compensation state and the PFC circuit switch state includes:

[0024] If the current torque compensation state is to turn off torque compensation and the current PFC circuit switch state is to turn on the PFC circuit, then trigger PFC overcurrent protection;

[0025] If the current torque compensation state is to turn off torque compensation and the current PFC circuit switch state is to turn off the PFC circuit, then trigger PFC overcurrent protection;

[0026] If the current torque compensation state is to turn on torque compensation and the current PFC circuit switch state is to turn on the PFC circuit, then trigger PFC overcurrent protection;

[0027] If the current torque compensation state is to turn on torque compensation and the current PFC circuit switch state is to turn off the PFC circuit, then do not trigger PFC overcurrent protection.

[0028] In a second aspect, the present invention also provides an air conditioner PFC circuit overcurrent protection control device, including:

[0029] An operating state monitoring module, configured to collect the compressor operating frequency, bus voltage value, and PFC current value in real time;

[0030] A torque compensation control module, configured to control the torque compensation state according to the collected compressor operating frequency;

[0031] A PFC circuit control module, configured to control the PFC circuit switch state according to the collected bus voltage value;

[0032] An overcurrent protection determination module, configured to make a judgment according to the collected PFC current value. When the PFC current value reaches or exceeds a preset threshold, combine the current torque compensation state and the PFC circuit switch state to determine whether to trigger PFC overcurrent protection.

[0033] In a third aspect, the present invention also provides a storage medium storing a computer program, which, when executed by a processor, implements the above-mentioned air conditioner PFC circuit overcurrent protection control method.

[0034] The beneficial effects of the present invention are:

[0035] (1) Accurate judgment to prevent false alarms of overcurrent faults:

[0036] The present invention makes a comprehensive judgment by combining multiple state parameters, so as to accurately distinguish real overcurrent from current spikes caused by specific working conditions. For real overcurrent, overcurrent protection is triggered; for current spikes caused by specific working conditions, overcurrent protection is not triggered and no fault is reported, thus avoiding false alarms of overcurrent faults.

[0037] (2) Reduce hardware costs:

[0038] The control scheme of the present invention realizes the detection and identification of overcurrent faults through software algorithms, does not rely on hardware implementation, and improves the economy of the system.

[0039] (3) Improve system reliability and flexibility:

[0040] The present invention dynamically adjusts the control strategy by comprehensively considering various parameters and working conditions, avoids the problem of low reliability of overcurrent protection control based on a single parameter, thereby improving the reliability of the system, and this scheme can adapt to different operating environments and working condition changes, improving the flexibility and applicability of the system. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 It is the working principle diagram of the PFC circuit in the air conditioner;

[0042] Figure 2 It is the flowchart of the overcurrent protection control method for the PFC circuit of the air conditioner in the present invention;

[0043] Figure 3 It is the schematic diagram of the PFC current waveform in the high-load heating scenario in the embodiment. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0044] The present invention aims to provide an overcurrent protection control method, device and storage medium for the PFC circuit of an air conditioner, to solve the problem of false alarms of overcurrent faults in the prior art, while reducing hardware costs and improving the reliability and economy of the system. Its core idea is: by real-time collecting key parameters such as the running frequency of the compressor, the bus voltage value and the PFC current value, controlling the torque compensation state according to the collected running frequency of the compressor, and controlling the switch state of the PFC circuit according to the collected bus voltage value; when the PFC current value reaches or exceeds the preset threshold, comprehensively considering the torque compensation state and the switch state of the PFC circuit, so as to accurately distinguish real overcurrent and spike current caused by specific working conditions. If it is real overcurrent, overcurrent protection is triggered; if it is spike current caused by specific working conditions, no fault is reported.

[0045] For easy understanding, first, the working principle of the PFC circuit in the air conditioner is introduced.

[0046] See Figure 1, the PFC circuit in the air conditioner includes a rectifier circuit 1, a power supply voltage detection circuit 2, a PFC inductor 3, a PFC drive circuit 4, an IGBT tube 5, a rectifier diode 6, a bus capacitor 7, a bus voltage detection circuit 8, a load such as a compressor 9, a microprocessor 10, and a current detection circuit 11. The working process is described as follows:

[0047] (1) PFC inductor charging process:

[0048] Control signal triggering: The microprocessor 10 sends a control signal to the PFC drive circuit 4.

[0049] IGBT tube conduction: After receiving the signal, the PFC drive circuit 4 controls the IGBT tube 5 to conduct.

[0050] Current path formation:

[0051] The current flows in from the power supply live wire L, and is preliminarily rectified by the rectifier circuit 1;

[0052] The current continues to flow through the PFC inductor 3, passes through the conducting IGBT 5, and then returns to the power supply neutral wire N through the rectifier circuit.

[0053] Electric energy storage: During this process, the PFC inductor 3 stores electric energy to prepare for the subsequent discharge process.

[0054] (2) PFC inductor discharge process:

[0055] Control signal change: The microprocessor 10 sends a signal to the PFC drive circuit 4 again.

[0056] IGBT disconnection: The PFC drive circuit 4 controls the IGBT tube 5 to disconnect, cutting off the current path.

[0057] Reverse electromotive force effect: The PFC inductor 3 generates a reverse electromotive force due to the current mutation, which is superimposed on the power supply voltage.

[0058] Bus capacitor charging:

[0059] The power supply voltage and the reverse electromotive force of the PFC inductor 3 act together to charge the bus capacitor 7 through the rectifier diode 6.

[0060] The bus capacitor 7 stores electric energy to provide a stable DC voltage for the load.

[0061] (3) Bus capacitor discharge process:

[0062] Control signal triggering again: The microprocessor 10 sends a signal to control the IGBT tube 5 to conduct again.

[0063] Dual current path:

[0064] Path 1: The power supply continues to charge the PFC inductor 3 to maintain the energy storage state of the inductor.

[0065] Path 2: The bus capacitor 7 releases the stored electrical energy to supply power to loads 9 such as compressors through an inverter or a DC bus.

[0066] Energy transfer: The discharge process of the bus capacitor 7 provides a stable working voltage and current for loads 9 such as compressors, ensuring the normal operation of the air-conditioning system.

[0067] Based on the above PFC circuit, the traditional air-conditioning control strategy is that if the current detection circuit 11 detects that the current exceeds the threshold and reaches a certain time, the microprocessor 10 will immediately trigger the PFC over-current protection. However, the traditional control strategy often does not fully consider the physical correlation between the PFC operating state and the current spike. As a result, for current spikes generated under certain special working conditions that do not damage the PFC circuit, they are misjudged as over-current faults, leading to unnecessary alarms or protection actions.

[0068] To solve this problem, the present invention accurately distinguishes between real over-current and current spikes caused by specific working conditions by combining multiple state parameters for comprehensive judgment. For real over-current, over-current protection is triggered; for current spikes caused by specific working conditions, over-current protection is not triggered and no fault is reported, thus avoiding false alarms of over-current faults.

[0069] In specific implementation, the over-current protection control method for the air-conditioning PFC circuit provided by the present invention is implemented by software logic, as can be seen in Figure 2 , and it includes the following implementation steps:

[0070] S1. Parameter initialization:

[0071] When the system starts, the thresholds of key parameters are initialized, including the on / off threshold of torque compensation, the on / off threshold of the PFC circuit, and the current threshold of PFC over-current protection, etc.

[0072] S2. Real-time monitoring of PFC current:

[0073] By collecting the PFC current value in real time and comparing it with the preset current threshold of PFC over-current protection. In an exemplary implementation, the current threshold of PFC over-current protection is set to 25A, then there is:

[0074] When the collected PFC current Ipfc < 25A, the air conditioner maintains its original state and operates normally, and continuously detects the PFC current.

[0075] When the collected PFC current Ipfc ≥ 25A, go to step S4.

[0076] S3. Real-time monitoring of compressor frequency and bus voltage:

[0077] By collecting the compressor frequency in real time and comparing it with the on / off threshold of torque compensation, the torque compensation state is controlled. In an exemplary embodiment, the on / off threshold of torque compensation includes a first frequency threshold and a second frequency threshold, where the first frequency threshold is set to 40 Hz and the second frequency threshold is set to 50 Hz; then:

[0078] When the collected compressor frequency f ≤ 40 Hz, torque compensation is turned on;

[0079] When the collected compressor frequency f > 50 Hz, torque compensation is turned off;

[0080] When 40 Hz < the collected compressor frequency f ≤ 50 Hz, maintain the original on / off mode of torque compensation.

[0081] By collecting the bus voltage value in real time and comparing it with the on / off threshold of the preset PFC circuit, the switch state of the PFC circuit is controlled. In an exemplary embodiment, the on / off threshold of the PFC circuit includes a first voltage threshold and a second voltage threshold, where the first voltage threshold is set to 360 V and the second voltage threshold is set to 370 V; then:

[0082] When the collected bus voltage V < 360 V, turn on the PFC;

[0083] When the collected bus voltage V ≥ 370 V, turn off the PFC;

[0084] When 360 V ≤ the collected bus voltage V < 370 V, keep the original on / off state of the PFC unchanged.

[0085] S4. Overcurrent protection determination:

[0086] When the collected PFC current Ipfc ≥ 25 A, in combination with the current torque compensation state and the PFC circuit switch state, determine whether to trigger PFC overcurrent protection, which is divided into the following four cases:

[0087] Case a: If the current torque compensation state is torque compensation off and the PFC circuit switch state is PFC on, in this case, the protection threshold should not be reached, but the current PFC current Ipfc ≥ 25 A, so PFC overcurrent protection is triggered.

[0088] Case b: If the current torque compensation state is torque compensation off and the PFC circuit switch state is PFC off, in this case, the protection threshold should not be reached, but the current PFC current Ipfc ≥ 25 A, so PFC overcurrent protection is triggered.

[0089] Case c: If the current torque compensation state is torque compensation enabled and the PFC circuit switch state is PFC enabled, under this condition, it should not reach the protection threshold. However, since the current PFC current Ipfc ≥ 25A, PFC overcurrent protection is triggered.

[0090] Case d: If the current torque compensation state is torque compensation enabled and the PFC circuit switch state is PFC disabled, this situation will occur in the operation scenario when the air conditioner is in high heating load, the compressor is running at low frequency, and the input voltage is relatively high, resulting in a relatively high bus voltage. At this time, the PFC is in the off state, and the current spike does not pass through the IGBT of the PFC, which is a normal phenomenon. Therefore, PFC overcurrent protection is not reported to prevent false alarms.

[0091] Embodiment

[0092] As Figure 3 shown, it is a schematic diagram of the PFC current waveform of a variable-frequency air conditioner in the heating scenario with high heating load, low-frequency operation of the compressor (f ≤ 40Hz), and high input voltage (254V).

[0093] In the time period from 0 to T1, at this time, the bus voltage V < 360V, and the PFC is enabled; the compressor frequency ≤ 40Hz, and the torque compensation is enabled. At this time, although the ripple current caused by the torque compensation under low-frequency operation increases, but Ipfc < 25A, the air conditioner maintains the original state and operates normally, and continuously detects the PFC current.

[0094] In the time period from T1 to T2, at this time, the bus voltage rises to V ≥ 370V, and the control will turn off the PFC to prevent damage to the system caused by further increase in the bus voltage. During the period when the PFC is turned off, due to the circuit characteristics, the input current will generate a spike, which, combined with the increase in the ripple current caused by the torque compensation under low-frequency operation of the compressor, will produce beat frequency oscillation, and the input instantaneous current reaches 35A, exceeding the protection threshold. However, at this time, the PFC is in the off state, and the current spike does not pass through the IGBT of the PFC, which is a normal phenomenon. Therefore, PFC overcurrent protection is not reported to prevent false alarms.

[0095] Finally, it should be noted that the above embodiments are only preferred embodiments and are not intended to limit the present invention. It should be pointed out that for those of ordinary skill in the art in this technical field, without departing from the spirit of the present invention and the scope protected by the claims, several modifications, equivalent replacements, improvements, etc. should all be included within the protection scope of the present invention.

Claims

1. The overcurrent protection control method for the air conditioner PFC circuit is characterized in that It includes the following steps: S1. Collect the compressor operating frequency, bus voltage value, and PFC current value in real time; S2. Control the torque compensation state according to the collected compressor operating frequency; S3. Control the PFC circuit switch state according to the collected bus voltage value; S4. Make a judgment based on the collected PFC current value. When the PFC current value reaches or exceeds the preset threshold, combine the current torque compensation state and the PFC circuit switch state to determine whether to trigger the PFC overcurrent protection.

2. The air conditioner PFC circuit overcurrent protection control method according to claim 1, wherein in step S2, controlling the torque compensation state according to the collected compressor operating frequency includes: When the compressor frequency ≤ the first frequency threshold, turn on the torque compensation; When the compressor frequency > the second frequency threshold, turn off the torque compensation; When the first frequency threshold < the compressor frequency ≤ the second frequency threshold, maintain the original torque compensation state.

3. The air conditioner PFC circuit overcurrent protection control method according to claim 1, wherein in step S3, controlling the PFC circuit switch state according to the collected bus voltage value includes: When the bus voltage value < the first voltage threshold, turn on the PFC circuit; When the bus voltage value ≥ the second voltage threshold, turn off the PFC circuit; When the first voltage threshold ≤ the bus voltage value < the second voltage threshold, maintain the original PFC circuit state.

4. The air conditioner PFC circuit overcurrent protection control method according to any one of claims 1-3, wherein in step S4, the combination of the current torque compensation state and the PFC circuit switch state to determine whether to trigger the PFC overcurrent protection includes: If the current torque compensation state is to turn off the torque compensation and the current PFC circuit switch state is to turn on the PFC circuit, trigger the PFC overcurrent protection; If the current torque compensation state is to turn off the torque compensation and the current PFC circuit switch state is to turn off the PFC circuit, trigger the PFC overcurrent protection; If the current torque compensation state is to turn on the torque compensation and the current PFC circuit switch state is to turn on the PFC circuit, trigger the PFC overcurrent protection; If the current torque compensation state is to turn on the torque compensation and the current PFC circuit switch state is to turn off the PFC circuit, do not trigger the PFC overcurrent protection.

5. The overcurrent protection control device for the air conditioner PFC circuit is characterized in that It includes: An operating state monitoring module for collecting the compressor operating frequency, bus voltage value, and PFC current value in real time; A torque compensation control module for controlling the torque compensation state according to the collected compressor operating frequency; A PFC circuit control module for controlling the PFC circuit switch state according to the collected bus voltage value; An overcurrent protection determination module for making a judgment based on the collected PFC current value. When the PFC current value reaches or exceeds the preset threshold, combine the current torque compensation state and the PFC circuit switch state to determine whether to trigger the PFC overcurrent protection.

6. The air conditioner PFC circuit overcurrent protection control device according to claim 5, wherein the control of the torque compensation state according to the collected compressor operating frequency includes: When the compressor frequency ≤ the first frequency threshold, turn on the torque compensation; When the compressor frequency > the second frequency threshold, turn off the torque compensation; When the first frequency threshold < the compressor frequency ≤ the second frequency threshold, maintain the original state of the torque compensation.

7. The air conditioner PFC circuit overcurrent protection control device according to claim 5, characterized in that The control of the PFC circuit switch state according to the collected bus voltage value includes: When the bus voltage value < the first voltage threshold, turn on the PFC circuit; When the bus voltage value ≥ the second voltage threshold, turn off the PFC circuit; When the first voltage threshold ≤ the bus voltage value < the second voltage threshold, maintain the original state of the PFC circuit.

8. The air conditioner PFC circuit overcurrent protection control device according to any one of claims 5-7, characterized in that The determination of whether to trigger PFC overcurrent protection by combining the current torque compensation state and the PFC circuit switch state includes: If the current torque compensation state is to turn off the torque compensation and the current PFC circuit switch state is to turn on the PFC circuit, then trigger PFC overcurrent protection; If the current torque compensation state is to turn off the torque compensation and the current PFC circuit switch state is to turn off the PFC circuit, then trigger PFC overcurrent protection; If the current torque compensation state is to turn on the torque compensation and the current PFC circuit switch state is to turn on the PFC circuit, then trigger PFC overcurrent protection; If the current torque compensation state is to turn on the torque compensation and the current PFC circuit switch state is to turn off the PFC circuit, then do not trigger PFC overcurrent protection.

9. A storage medium storing a computer program, characterized in that When the computer program is executed by a processor, it implements the air conditioner PFC circuit overcurrent protection control method according to any one of claims 1-4.

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