Current-limiting protection method and current-limiting protection circuit

Abstract

The invention provides a current-limiting protection method and a current-limiting protection circuit. The current-limiting protection method comprises the steps of generating a preset wave-by-wave current value when an inverter is started and loaded, so as to carry out wave-by-wave current limiting on the inverter. And in the process of wave-by-wave current limiting, the phase difference between the phase current and the phase voltage of the inverter is obtained. And judging the load type of the inverter based on the phase difference between the phase current and the phase voltage. And adjusting the preset wave-by-wave current value according to the load type so as to match the load type. According to the invention, the load type of the inverter can be judged according to the phase difference between the phase current and the phase voltage, such as inductive, capacitive or resistive load. And then the preset wave-by-wave current value is adjusted according to different load types, so that the inverter can better adapt to loads with different characteristics. Namely, the wave-by-wave current value can be dynamically adjusted according to the type of the load, so that the inverter can adapt to the change of the load in time, and the operation stability of the inverter is improved.

Description

Technical Field

[0001] This application relates to the field of electronic circuit technology, and in particular to a current limiting protection method and a current limiting protection circuit. Background Technology

[0002] There are two main types of existing wave-by-wave current limiting protection technologies.

[0003] One approach is to utilize overcurrent detection circuits and zero-crossing voltage detection circuits, along with software identification of the hardware logic control unit to distinguish between rectification and inversion states, thereby achieving wave-by-wave current limiting protection. However, this method suffers from drawbacks such as cumbersome implementation of wave-by-wave current limiting, fixed hardware current limiting values ​​that cannot adapt to different loads, high cost of hardware logic circuit construction, and reduced software application capabilities.

[0004] Another method is to achieve wave-by-wave current limiting protection by using voltage and current sampling circuits, hardware current limiting comparison circuits, and hardware wave-by-wave current limiting circuits to block the power transistor drive. The drawback of this method is that the hardware settings for the upper and lower values ​​of wave-by-wave current limiting are inflexible, and the hardware implementation of the wave-by-wave blocking circuit is complex and costly. Summary of the Invention

[0005] This application provides a current limiting protection method and a current limiting protection circuit that can dynamically adjust the wave-by-wave current value according to the load type, enabling the inverter to adapt to load changes in a timely manner and improving the stability of inverter operation.

[0006] In a first aspect, embodiments of this application provide a current limiting protection method, the current limiting protection method comprising: generating a preset wave-by-wave current value when the inverter is powered on and loaded, so as to perform wave-by-wave current limiting on the inverter; during the wave-by-wave current limiting process, obtaining the phase difference between the phase current and the phase voltage of the inverter; determining the load type of the inverter based on the phase difference between the phase current and the phase voltage; and adjusting the preset wave-by-wave current value according to the load type to match the load type.

[0007] In some embodiments, during wave-by-wave current limiting, before performing the step of acquiring the phase difference between the phase current and the phase voltage of the inverter, the current limiting protection method further includes: determining whether the overcurrent protection condition is met based on the acquired sampling signal; if the overcurrent protection condition is met, then performing overcurrent protection on the inverter.

[0008] In some embodiments, determining whether the overcurrent protection condition is met based on the acquired sampling signal includes: if the sampling signal is greater than the overcurrent protection threshold, then outputting an overcurrent protection signal; counting the received overcurrent protection threshold to obtain the number of overcurrent events; if the number of overcurrent events is within a preset overcurrent range, then the overcurrent protection condition is not met; if the number of overcurrent events exceeds the preset overcurrent range, then the overcurrent protection condition is met.

[0009] In some embodiments, determining the load type of the inverter based on the phase difference between the phase current and the phase voltage includes: if the phase current lags behind the phase voltage, the load type is determined to be an inductive load; if the phase current leads the phase voltage, the load type is determined to be a capacitive load; if the phase current is in phase with the phase voltage, the load type is determined to be a resistive load.

[0010] In some embodiments, adjusting the preset wave-by-wave current value according to the load type includes: when the load type is an inductive load or a capacitive load, reducing the preset wave-by-wave current value based on the power value of the load and the phase difference; when the load type is a resistive load, increasing the preset wave-by-wave current value based on the load-carrying capacity of the inverter.

[0011] Secondly, this application embodiment also provides a current limiting protection circuit, the current limiting protection circuit comprising: a sampling module connected to the inverter for sampling; a phase detection module connected to the inverter for detecting the phase current and phase voltage of the inverter; and a main control module connected to the sampling module, the phase detection module and the inverter respectively, for executing the current limiting protection method as described above.

[0012] In some embodiments, the phase detection module includes: a current phase detection unit connected to the inverter for detecting the phase current of the inverter; and a voltage phase detection unit connected to the inverter for detecting the phase voltage of the inverter.

[0013] In some embodiments, the current phase detection unit includes: a first operational amplifier subunit connected to the inverter, used to amplify the phase current of the inverter to obtain a preprocessed phase current signal; a first comparison subunit connected to the first operational amplifier subunit, used to convert the preprocessed phase current signal into a phase current square wave signal, and the main control module is further used to obtain the phase of the phase current based on the phase current square wave signal.

[0014] In some embodiments, the voltage phase detection unit includes: a second operational amplifier subunit connected to the inverter, used to amplify the phase voltage of the inverter to obtain a preprocessed phase voltage signal; a second comparison subunit connected to the second operational amplifier subunit, used to convert the preprocessed phase voltage signal into a phase voltage square wave signal, and the main control module is further used to obtain the phase of the phase voltage based on the phase voltage square wave signal.

[0015] In some embodiments, the sampling module includes an operational amplifier U2A, resistors R26, R27, R28, R31, R32, and R35; the first end of resistor R31 is connected to the inverter, the first end of resistor R32 is used to receive the preset wave-by-wave current value, the second end of resistor R31 is connected to both the first end of resistor R26 and the non-inverting input of operational amplifier U2A, the second end of resistor R26 is grounded, the second end of resistor R32 is connected to both the first end of resistor R35 and the inverting input of operational amplifier U2A, the output of operational amplifier U2A is connected to both the second end of resistor R35 and the first end of resistor R28, the second end of resistor R28 is connected to the second end of resistor R27, and the first end of resistor R27 is connected to the power supply; wherein, the second end of resistor R28 serves as the output of the sampling module.

[0016] Unlike existing technologies, this application provides a current-limiting protection method and circuit. The current-limiting protection method includes: generating a preset wave-by-wave current value when the inverter is powered on and under load, to perform wave-by-wave current limiting on the inverter. During the wave-by-wave current limiting process, the phase difference between the phase current and phase voltage of the inverter is acquired. The load type of the inverter is determined based on the phase difference between the phase current and phase voltage. The preset wave-by-wave current value is adjusted according to the load type to match the load type. This application can determine the load type of the inverter, such as inductive, capacitive, or resistive loads, based on the phase difference between the phase current and phase voltage. Then, the preset wave-by-wave current value is adjusted according to different load types, allowing the inverter to better adapt to loads with different characteristics. That is, the wave-by-wave current value can be dynamically adjusted according to the load type, enabling the inverter to adapt to load changes in a timely manner and improving the stability of inverter operation. Attached Figure Description

[0017] One or more embodiments are illustrated by way of example with reference to the accompanying drawings. These illustrations do not constitute a limitation on the embodiments. Elements having the same reference numerals in the drawings are denoted as similar elements. Unless otherwise stated, the figures in the drawings are not to be limited by scale.

[0018] Figure 1 This is a structural block diagram of a current limiting protection circuit provided in an embodiment of this application; Figure 2 This is a schematic diagram of the circuit structure of the sampling module provided in the embodiments of this application; Figure 3 This is a structural block diagram of the phase detection module provided in the embodiments of this application; Figure 4 This is a schematic diagram of the circuit structure of the current phase detection unit provided in the embodiments of this application; Figure 5 This is a schematic diagram of the circuit structure of the voltage phase detection unit provided in the embodiments of this application; Figure 6 This is a flowchart illustrating a current limiting protection method provided in an embodiment of this application. Detailed Implementation

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and thoroughly described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. It should be understood that the specific embodiments described herein are only used to explain this application and are not intended to limit this application.

[0020] The technical features involved in the various embodiments of this application described below do not conflict with each other and can be combined with each other.

[0021] When an element is described as "connected" to another element, it can be directly connected to the other element, or there may be one or more intervening elements between them.

[0022] The terms "first," "second," etc., used in the specification and claims of this application are used to distinguish similar objects and are not used to describe a specific order or sequence. It should be understood that such data can be interchanged where appropriate so that embodiments of this application can be implemented in orders other than those illustrated or described herein, and the objects distinguished by "first," "second," etc., are generally of the same class and are not limited in number; for example, a first object can be one or more.

[0023] Please see Figure 1 , Figure 1 This is a structural block diagram of a current limiting protection circuit 200 provided in an embodiment of this application.

[0024] This application provides a current-limiting protection circuit 200, which includes a sampling module 40, a phase detection module 50, and a main control module 60. The sampling module 40 is connected to an inverter 300, the phase detection module 50 is connected to the inverter 300, and the main control module 60 is connected to the sampling module 40, the phase detection module 50, and the inverter 300. Specifically, the sampling module 40 is used for sampling. The phase detection module 50 is used for detecting the phase current and phase voltage of the inverter 300. The main control module 60, connected to the sampling module 40, the phase detection module 50, and the inverter 300, is used to execute the current-limiting protection method described in the following embodiments.

[0025] In practical applications, the sampling module 40 is connected to the inverter 300 and samples the output current of the inverter; the phase detection module 50 detects the phase current and phase voltage of the inverter in real time; the main control module 60 receives the phase current and phase voltage from the phase detection module 50 and adjusts the preset wave-by-wave current value by executing the current limiting protection method in the following embodiments to match the load type and realize dynamic current limiting protection for the inverter 300.

[0026] In some embodiments, the main control module 60 includes a DSP (Digital Signal Processor) chip or other equivalent MCU (Microcontroller Unit).

[0027] Please see Figure 2 , Figure 2 This is a schematic diagram of the circuit structure of the sampling module 40 provided in the embodiment of this application.

[0028] In some embodiments, the sampling module 40 includes an operational amplifier U2A, resistors R26, R27, R28, R31, R32, and R35. The first terminals of resistors R31 and R32 can be connected to the sampled values ​​at both ends of a shunt, or to the current signal voltage value output by a Hall effect sensor. The second terminal of resistor R31 is simultaneously connected to the first terminal of resistor R26 and the non-inverting input terminal of operational amplifier U2A, and the second terminal of resistor R26 is grounded. The second terminal of resistor R32 is simultaneously connected to the first terminal of resistor R35 and the inverting input terminal of operational amplifier U2A. The output terminal of operational amplifier U2A is simultaneously connected to the second terminal of resistor R35 and the first terminal of resistor R28. The second terminal of resistor R28 is connected to the second terminal of resistor R27, and the first terminal of resistor R27 is connected to the power supply. The second terminal of resistor R28 (ADC.I) serves as the output terminal of the sampling module 40. Specifically, the sampling module 40 performs signal conditioning, converting the input signal into a signal that can be processed by subsequent circuits (ADC port, comparator, etc.).

[0029] Please see Figure 3 , Figure 3 This is a structural block diagram of the phase detection module 50 provided in the embodiments of this application.

[0030] In some embodiments, such as Figure 3 As shown, the phase detection module 50 includes a current phase detection unit 51 and a voltage phase detection unit 52. The current phase detection unit 51 is connected to the inverter 300 and the main control module 60, and is used to detect the phase current of the inverter 300; the voltage phase detection unit 52 is connected to the inverter 300 and the main control module 60, and is used to detect the phase voltage of the inverter 300.

[0031] In some embodiments, such as Figure 4 As shown, the current phase detection unit 51 includes a first operational amplifier subunit 511 and a first comparator subunit 512. The first operational amplifier subunit 511 is connected to the inverter 300 and is used to amplify the phase current of the inverter 300 to obtain a pre-processed phase current signal. The first comparator subunit 512 is connected to the first operational amplifier subunit 511 and is used to convert the pre-processed phase current signal into a phase current square wave signal. The main control module 60 is also used to obtain the phase of the phase current based on the phase current square wave signal.

[0032] Specifically, such as Figure 4 As shown, the first operational amplifier subunit 511 includes operational amplifier U1A, resistors R20, R21, R22, R23, R24, and R25. The first terminals of resistors R23 and R24 can be connected to either the sampled values ​​at both ends of a shunt or the current signal voltage value output by a Hall effect sensor. The second terminal of resistor R23 is simultaneously connected to the first terminal of resistor R20 and the non-inverting input terminal of operational amplifier U1A. The second terminal of resistor R20 is grounded. The second terminal of resistor R24 ​​is simultaneously connected to the first terminal of resistor R25 and the inverting input terminal of operational amplifier U1A. The output terminal of operational amplifier U1A is simultaneously connected to the second terminal of resistor R25 and the first terminal of resistor R22. The second terminal of resistor R22 is connected to the second terminal of resistor R21. The first terminal of resistor R21 is connected to the power supply (VRE3V). The second terminal of resistor R22 (ADC.I2) serves as the output terminal of the first operational amplifier subunit 511.

[0033] Specifically, the first comparator subunit 512 includes a comparator U3A, resistors R29, R34, R37, R36, R30, R33, and a Zener diode D5. The first terminal of resistor R29 is connected to the output of the first operational amplifier subunit 511, and the second terminal of resistor R29 is connected to the inverting input of comparator U3A. The first terminal of resistor R34 is connected to the power supply (VRE3V), and the second terminal of resistor R34 is simultaneously connected to the non-inverting input of comparator U3A, the first terminal of resistor R37, and the positive terminal of Zener diode D5. The second terminal of resistor R37 is grounded. The output of comparator U3A is simultaneously connected to the second terminals of resistors R30, R33, and R36. The first terminal of resistor R36 is connected to the negative terminal of Zener diode D5. The first terminal of resistor R30 is connected to the power supply (+3.3V), and the second terminal of resistor R33 (CAP.I) serves as the output of the first comparator subunit 512.

[0034] In practical applications, such as Figure 4As shown, the phase current output by the inverter 300 passes through the first operational amplifier subunit 511 and then through the first comparator subunit 512 to obtain the phase current square wave signal. This phase current square wave signal can be identified by the capture CAP (or other equivalent MCU) of the DSP (main control module 60) to determine the zero-crossing falling edge time T1 (i.e. the phase of the phase current).

[0035] Please see Figure 5 , Figure 5 This is a schematic diagram of the circuit structure of the voltage phase detection unit 52 provided in the embodiment of this application.

[0036] In some embodiments, such as Figure 5 As shown, the voltage phase detection unit 52 includes a second operational amplifier subunit 521 and a second comparator subunit 522. The second operational amplifier subunit 521 is connected to the inverter 300 and is used to amplify the phase voltage of the inverter 300 to obtain a preprocessed phase voltage signal. The second comparator subunit 522 is connected to the second operational amplifier subunit 521 and is used to convert the preprocessed phase voltage signal into a phase voltage square wave signal. The main control module 60 is also used to obtain the phase of the phase voltage based on the phase voltage square wave signal.

[0037] Specifically, such as Figure 5 As shown, the second operational amplifier subunit 521 includes operational amplifier U1B, resistors R39, R43, R46, R47, R38 and R42. In this configuration, the first terminal of resistor R39 (V+_smp) is connected to the positive terminal of inverter 300, the first terminal of resistor R43 (V-_smp) is connected to the negative terminal of inverter 300 to receive the phase voltage of inverter 300, the second terminal of resistor R43 is connected to both the first terminal of resistor R39 and the non-inverting input terminal of operational amplifier U1B, the second terminal of resistor R39 is grounded, the second terminal of resistor R46 is connected to both the first terminal of resistor R47 and the inverting input terminal of operational amplifier U1B, the output terminal of operational amplifier U1B is connected to both the second terminal of resistor R47 and the first terminal of resistor R42, the first terminal of resistor R47 is connected to the second terminal of resistor R46, the second terminal of resistor R42 is connected to the second terminal of resistor R38, and the first terminal of resistor R38 is connected to the power supply (VRE3V); the second terminal of resistor R42 (ADC.V) serves as the output terminal of the second operational amplifier subunit 521.

[0038] Specifically, the second comparator subunit 522 includes a comparator U4A, resistors R41, R45, R49, R48, R40, R44, and a Zener diode D6. The first terminal of resistor R41 is connected to the output of the second operational amplifier subunit 521, and the second terminal of resistor R41 is connected to the inverting input of comparator U4A. The first terminal of resistor R45 is connected to the power supply (VRE3V), and the second terminal of resistor R45 is simultaneously connected to the non-inverting input of comparator U4A, the first terminal of resistor R49, and the positive terminal of Zener diode D6. The second terminal of resistor R49 is grounded. The output of comparator U4A is simultaneously connected to the second terminals of resistors R40, R44, and R48. The first terminal of resistor R48 is connected to the negative terminal of Zener diode D6. The first terminal of resistor R40 is connected to the power supply (+3.3V), and the second terminal of resistor R44 (CAP.U) serves as the output of the second comparator subunit 522.

[0039] In practical applications, such as Figure 5 As shown, the phase voltage output by the inverter 300 passes through the second operational amplifier subunit 521 and then through the second comparator subunit 522 to obtain the phase voltage square wave signal. The phase voltage square wave signal can be adjusted by the capture device CAP (or other equivalent MCU) of the DSP (main control module 60) to identify the zero-crossing falling edge time T2 (that is, the phase of the phase voltage) of the phase voltage square wave signal.

[0040] Specifically, the main control module 60 receives the phase current and phase voltage from the phase detection module 50, and adjusts the preset wave-by-wave current value by executing the current limiting protection method in the following embodiments to match the load type, thereby realizing dynamic current limiting protection for the inverter 300.

[0041] Please see Figure 6 , Figure 6 This is a flowchart illustrating a current limiting protection method provided in an embodiment of this application.

[0042] This application provides a current limiting protection method, such as... Figure 6 As shown, the current limiting protection methods include: Step S1: When the inverter is powered on, a preset wave-by-wave current value is generated to limit the inverter current wave by wave.

[0043] The preset wave-by-wave current value is a pre-set current threshold used to limit the current waveform in real time during inverter operation. When the current exceeds this threshold, a current-limiting action is immediately triggered to prevent overcurrent damage to the devices. The preset wave-by-wave current value is a signal generated and output by the main control module 60.

[0044] At the moment the inverter is powered on, the system first generates a preset wave-by-wave current value. This value serves as the initial current threshold and is used to monitor the inverter output current in real time during each PWM cycle. The sampling module 40 compares the real-time current of the inverter 300 with the preset wave-by-wave current value through a comparator circuit. Once the current exceeds the preset wave-by-wave current value, the main control module 60 is immediately triggered to perform protection actions (such as shortening the on-time of the switching transistor) to suppress current peaks and prevent overcurrent damage to power devices.

[0045] Step S2: During the wave-by-wave current limiting process, obtain the phase difference between the phase current and phase voltage of the inverter.

[0046] During continuous current-limiting operation, the phase detection module synchronously acquires the phase current and phase voltage signals of the inverter. The analog signals are converted into digital quantities using the ADC sampling unit built into the DSP or MCU, and the phase difference between them is calculated using zero-crossing detection. For example, the phase angle difference is calculated by detecting the time difference between the zero-crossing points of the phase voltage and phase current, combined with the sampling frequency.

[0047] Specifically, the current square wave signal output by the phase current phase detection unit 51 has its corresponding zero-crossing falling edge time T1 (that is, the phase of the phase current). The phase voltage square wave signal output by the voltage phase detection unit 52 has its corresponding zero-crossing falling edge time T2 (that is, the phase of the phase voltage).

[0048] The main control module 60 (e.g., DSP) calculates the comparison times T1 and T2 using an internal timer. When T1 > T2, it indicates that the phase current lags behind the phase voltage; when T2 > T1, it indicates that the phase voltage lags behind the phase current; when T1 = T2, it indicates that the phase voltage and phase current are in phase.

[0049] Step S3: Determine the load type of the inverter based on the phase difference between the phase current and the phase voltage. The load type includes inductive load, capacitive load, and resistive load.

[0050] In some embodiments, determining the load type of the inverter based on the phase difference between the phase current and the phase voltage includes: if the phase current lags behind the phase voltage, the load type is determined to be an inductive load; if the phase current leads the phase voltage, the load type is determined to be a capacitive load; if the phase current and the phase voltage are in phase, the load type is determined to be a resistive load.

[0051] Specifically, when T1 > T2, it indicates that the phase current lags behind the phase voltage, thus determining the load type as an inductive load (such as a motor, transformer, etc.). When T2 > T1, it indicates that the phase voltage lags behind the phase current, thus determining the load type as a capacitive load, such as a capacitor filter circuit. When T1=T2, it means that the phase voltage and phase current are in phase, thus determining that the load type is a resistive load (such as a heater).

[0052] Step S4: Adjust the preset wave-by-wave current value according to the load type to match the load type.

[0053] In some embodiments, adjusting the preset wave-by-wave current value according to the load type includes: when the load type is an inductive load or a capacitive load, reducing the preset wave-by-wave current value based on the load power value and phase difference; when the load type is a resistive load, increasing the preset wave-by-wave current value based on the inverter's load-carrying capacity.

[0054] Specifically, for inductive / capacitive loads, the reactive component is calculated based on the power value and phase difference. By reducing the preset current threshold (e.g., to 70%–90% of the original value), the additional heat generated by reactive current is limited. For resistive loads, since their power factor is close to 1, and provided that the inverter's load-carrying capacity is confirmed to be sufficient (not exceeding the overload capacity range), the threshold is appropriately increased (e.g., to 110%–120%) to fully utilize the equipment's efficiency.

[0055] In some embodiments, during wave-by-wave current limiting, before performing the step of obtaining the phase difference between the phase current and phase voltage of the inverter, the current limiting protection method further includes: Step S6: Determine whether the overcurrent protection conditions are met based on the acquired sampling signal. Specifically, determining whether the overcurrent protection conditions are met based on the acquired sampling signal includes: if the sampling signal is greater than the overcurrent protection threshold, output an overcurrent protection signal; count the received overcurrent protection signals to obtain the number of overcurrent events; if the number of overcurrent events is within a preset overcurrent range, the overcurrent protection conditions are not met; if the number of overcurrent events exceeds the preset overcurrent range, the overcurrent protection conditions are met.

[0056] The overcurrent protection threshold is a standard current value used to determine whether an overcurrent has occurred.

[0057] Specifically, the main control module 60 receives overcurrent protection signals in real time, and counts the acquired overcurrent protection signals (such as edge counting) to accumulate the number of overcurrent events.

[0058] For example, a sliding time window mechanism can be used for counting and statistics, such as setting a time window of 1 second. When the number of overcurrents within the time window is within the preset overcurrent range (such as 5 to 10 times), it is considered a normal load fluctuation, that is, the overcurrent protection condition is not met; if it exceeds the upper limit (such as 15 times), it is determined to be an abnormal overcurrent, that is, the overcurrent protection condition is met.

[0059] Step S7: If the overcurrent protection conditions are met, the inverter is protected against overcurrent. Overcurrent protection methods include reducing the preset wave-by-wave current value and forcibly shutting down the inverter 300, avoiding system instability caused by frequent protection while ensuring rapid response in the event of a genuine overcurrent fault, thus achieving a balance between protection reliability and system availability.

[0060] The current-limiting protection method provided in this embodiment determines the inverter's load type, such as inductive, capacitive, or resistive load, based on the phase difference between the phase current and phase voltage. Then, it adjusts the preset wave-by-wave current value according to different load types, enabling the inverter to better adapt to loads with different characteristics. In other words, it can dynamically adjust the wave-by-wave current value according to the load type, allowing the inverter to adapt to load changes in a timely manner and improving the stability of inverter operation.

[0061] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them; under the concept of this application, the technical features of the above embodiments or different embodiments can also be combined, and there are many other variations of different aspects of this application as described above. For the sake of brevity, they are not provided in detail; although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or make equivalent substitutions for some of the technical features; and these modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of this application.

Claims

1. A current limiting protection method, characterized in that, The current limiting protection method includes: When the inverter is powered on, a preset wave-by-wave current value is generated to limit the current of the inverter wave by wave. During the wave-by-wave current limiting process, the phase difference between the phase current and phase voltage of the inverter is obtained; The load type of the inverter is determined based on the phase difference between the phase current and the phase voltage; The preset wave-by-wave current value is adjusted according to the load type to match the load type.

2. The current limiting protection method according to claim 1, characterized in that, During wave-by-wave current limiting, before performing the step of obtaining the phase difference between the phase current and phase voltage of the inverter, the current limiting protection method further includes: Determine whether the overcurrent protection conditions are met based on the obtained sampled current; If the overcurrent protection conditions are met, then the inverter is protected against overcurrent.

3. The current limiting protection method according to claim 2, characterized in that, The determination of whether the overcurrent protection conditions are met based on the acquired sampled signal includes: If the sampled signal is greater than the overcurrent protection threshold, an overcurrent protection signal is output. The received overcurrent protection signals are counted to obtain the number of overcurrent events; If the number of overcurrent cycles is within the preset overcurrent range, then the overcurrent protection condition is not met. If the number of overcurrent cycles exceeds the preset overcurrent range, then the overcurrent protection condition is met.

4. The current limiting protection method according to claim 1, characterized in that, The method of determining the load type of the inverter based on the phase difference between the phase current and the phase voltage includes: If the phase current lags behind the phase voltage, then the load type is determined to be an inductive load; If the phase current leads the phase voltage, then the load type is determined to be a capacitive load; If the phase current and the phase voltage are in phase, then the load type is determined to be a resistive load.

5. The current limiting protection method according to claim 1, characterized in that, The step of adjusting the preset wave-by-wave current value according to the load type includes: When the load type is an inductive load or a capacitive load, the preset wave-by-wave current value is reduced based on the power value of the load and the phase difference; When the load type is resistive load, the preset wave-by-wave current value is increased based on the inverter's load-carrying capacity.

6. A current-limiting protection circuit, characterized in that, The current limiting protection circuit includes: The sampling module is connected to the inverter to perform sampling. A phase detection module, connected to the inverter, is used to detect the phase current and phase voltage of the inverter; The main control module is connected to the sampling module, the phase detection module and the inverter respectively, and is used to execute the current limiting protection method as described in any one of claims 1 to 5.

7. The current limiting protection circuit according to claim 6, characterized in that, The phase detection module includes: A current phase detection unit, connected to the inverter, is used to detect the phase current of the inverter; A voltage phase detection unit, connected to the inverter, is used to detect the phase voltage of the inverter.

8. The current limiting protection circuit according to claim 7, characterized in that, The current phase detection unit includes: The first operational amplifier subunit is connected to the inverter and is used to amplify the phase current of the inverter to obtain a preprocessed phase current signal. The first comparator subunit, connected to the first operational amplifier subunit, is used to convert the preprocessed phase current signal into a phase current square wave signal. The main control module is also used to obtain the phase of the phase current based on the phase current square wave signal.

9. The current limiting protection circuit according to claim 7, characterized in that, The voltage phase detection unit includes: The second operational amplifier subunit is connected to the inverter and is used to amplify the phase voltage of the inverter to obtain a preprocessed phase voltage signal. The second comparator subunit, connected to the second operational amplifier subunit, is used to convert the preprocessed phase voltage signal into a phase voltage square wave signal. The main control module is also used to obtain the phase of the phase voltage based on the phase voltage square wave signal.

10. The current limiting protection circuit according to claim 6, characterized in that, The sampling module includes operational amplifier U2A, resistors R26, R27, R28, R31, R32 and R35; The first end of resistor R31 is connected to the inverter. The first end of resistor R32 is used to receive the preset wave-by-wave current value. The second end of resistor R31 is simultaneously connected to the first end of resistor R26 and the non-inverting input of operational amplifier U2A. The second end of resistor R26 is grounded. The second end of resistor R32 is simultaneously connected to the first end of resistor R35 and the inverting input of operational amplifier U2A. The output of operational amplifier U2A is simultaneously connected to the second end of resistor R35 and the first end of resistor R28. The second end of resistor R28 is connected to the second end of resistor R27. The first end of resistor R27 is connected to the power supply. The second end of resistor R28 serves as the output of the sampling module.

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