Frequency converter and protection method thereof

Abstract

The invention discloses a frequency converter and a protection method thereof. The frequency converter comprises a plurality of copper bars, a temperature measurement circuit, a current measurement circuit and an MCU. The temperature measuring circuit is connected with the MCU and sends the sampled temperature of each copper bar to the MCU; the current measuring circuit is connected with the MCU and sends the sampled current of each copper bar to the MCU; the MCU diagnoses the running state of the copper bars based on the temperature of each copper bar, including the following steps: if the temperature of a single copper bar is out of limit or the temperature difference between the copper bars in the same type of copper bars is out of limit, determining that the copper bars are connected abnormally, and executing a first protection action; and the MCU diagnoses the running state of the copper bar based on the current of each copper bar: if the range of the current of a single copper bar in the sampling period is out of limit and the current change rate is out of limit, determining that the connection of the copper bar is abnormal, and executing a first protection action. By monitoring the temperature and current data during operation of the copper bars, the connection condition of the copper plates is judged, and safe operation of the frequency converter is ensured.

Description

Technical Field

[0001] This invention belongs to the field of frequency converter technology, and more specifically, relates to a frequency converter and its protection method. Background Technology

[0002] Variable frequency drives (VFDs) are widely used in industrial automation. They can regulate motor speed, adjust equipment operating status, and adjust motor power according to load conditions. They also reduce current surges during equipment startup and provide various protection functions to ensure normal equipment operation. VFDs offer advantages such as energy saving, extended equipment lifespan, and enhanced protection.

[0003] Inside a frequency converter, there are typically many power electronic circuits, and there is significant energy exchange between the various modules. The copper busbar, as the medium for current transfer and exchange, is crucial; any abnormalities in its connection can affect the normal operation of the system. When there are safety hazards in the copper busbar connection, such as, but not limited to, insufficient current-carrying capacity or loose fixing screws, the temperature of the copper busbar at the abnormal connection will rise rapidly as the power level of the frequency converter gradually increases, even exceeding its permissible operating temperature limit. This can range from affecting the normal operation of the frequency converter to, in severe cases, causing arcing, copper busbar explosion, and equipment damage. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides a frequency converter and a frequency converter protection method based on copper busbar abnormal connection detection. By monitoring the temperature and current data of copper busbars during operation, the method can determine the connection status of the copper busbars, ensuring the safe operation of the frequency converter. Based on this, the method enables real-time monitoring of the copper busbar temperature, providing a relatively simple criterion for whether an electric arc has occurred. Furthermore, based on the collected information, the method can perform protection functions for the frequency converter system under abnormal conditions.

[0005] The present invention adopts the following technical solution.

[0006] A first aspect of the present invention provides a frequency converter, comprising: multiple copper busbars, a temperature measurement circuit, a current measurement circuit, and an MCU;

[0007] The temperature measurement circuit is connected to the MCU and sends the sampled temperature of each copper busbar to the MCU;

[0008] The current measurement circuit is connected to the MCU and sends the sampled current of each copper busbar to the MCU;

[0009] The MCU diagnoses the operating status of the copper busbars based on the temperature of each copper busbar, including: if the temperature of a single copper busbar exceeds the limit or the temperature difference between copper busbars of the same type exceeds the limit, the copper busbar connection is determined to be abnormal and the first protection action is executed.

[0010] The MCU diagnoses the operating status of the copper busbars based on the current of each copper busbar, including: if the current of a single copper busbar exceeds the limit in the sampling period and the current change rate exceeds the limit, then the copper busbar connection is determined to be abnormal and the first protection action is executed.

[0011] Preferably, the temperature measurement circuit includes a thermistor and a sampling circuit, wherein the thermistor is disposed at each copper busbar;

[0012] The voltage of the thermistor is obtained by sampling circuit, and the temperature of each copper busbar is obtained by conversion.

[0013] Preferably, the temperature measurement circuit includes: a first operational amplifier OPA1, a second operational amplifier OPA2, a transistor VT1, an ADC, and a load thermistor PT1.

[0014] The non-inverting input terminal of the first operational amplifier OPA1 is connected to the first reference voltage V1 and grounded through capacitor C1; the inverting input terminal is connected to the second reference voltage V2 through current limiting resistor R1; the emitter of the transistor VT1 is connected to the inverting input terminal; the base is connected to the output terminal of the first operational amplifier OPA1; and the collector is grounded through the load thermistor PT1.

[0015] One input terminal of the second operational amplifier OPA2 is connected to the collector of the transistor VT1, and the other input terminal is connected to the grounding resistor R3 and the feedback resistor R2. The other end of the feedback resistor R2 is connected to the output terminal of the second operational amplifier OPA2 and then to the ADC.

[0016] Preferably, the frequency converter further includes: a photoelectric sensor, which is connected to the MCU, and sends the acquired light signal of the electric arc to the MCU. If the light signal of the electric arc exceeds the limit, it is determined that the copper busbar connection is abnormal and a second protection action is executed.

[0017] A second aspect of the present invention provides a protection method for a frequency converter, based on the frequency converter as described in the first aspect, comprising the following steps:

[0018] Start the sampling period, sample the current of each copper busbar, and diagnose the operating status of the copper busbar based on the current of each copper busbar, including: if the current of a single copper busbar exceeds the range limit and the current change rate exceeds the limit within the sampling period, it is determined that the copper busbar connection is abnormal and the first protection action is executed.

[0019] The temperature of each copper busbar is obtained by sampling, and the operating status of the copper busbar is diagnosed based on the temperature of each copper busbar, including: if the temperature of a single copper busbar exceeds the limit or the temperature difference between copper busbars of the same type exceeds the limit, the copper busbar connection is determined to be abnormal and the first protection action is executed.

[0020] Preferably, the step of activating the sampling period, sampling the current of each copper busbar, and diagnosing the operating status of the copper busbars based on the current of each copper busbar includes:

[0021] The current of each copper busbar is collected, the data of each sampling point is buffered within the sampling period, and then sent to the inverter MCU for diagnosis.

[0022] For any copper busbar, if the current range is greater than the set current threshold and the current change rate is greater than the set change rate threshold, then the copper busbar is determined to be in an abnormal state.

[0023] If either the current range is greater than the set current threshold or the current change rate is greater than the set change rate threshold, then after the current sampling period ends, the next sampling period will begin immediately for repeated detection.

[0024] If the current range is less than or equal to the set current threshold and the current change rate is less than or equal to the set change rate threshold, then the copper busbar is determined to be operating normally within the sampling period, and the next sampling period will be waited for.

[0025] Preferably, the step of determining that the copper busbar connection is abnormal and executing the first protection action if the temperature of a single copper busbar exceeds the limit includes:

[0026] For the AC side copper busbars, if the temperature of any one of the three phase copper busbars (A, B, and C) is greater than the second threshold T... th2 If so, there is an abnormal connection in the three-phase copper busbar;

[0027] For the DC-side copper busbar, if the temperature of either the positive DC+ or negative DC- busbar is greater than the second threshold T... th2 If the DC positive (DC+) and negative (DC-) copper busbars are not connected correctly, then there is a connection abnormality. For the midpoint O copper busbar, if its temperature is greater than the second threshold T... th2 If the copper busbar at midpoint O has a connection anomaly, then there is an anomaly.

[0028] Preferably, the step of determining an abnormal copper busbar connection and executing a first protection action if the temperature difference between copper busbars of the same type exceeds the limit includes:

[0029] For the AC side copper busbar, if the temperature difference between any two phases of the three-phase copper busbars A, B, and C is greater than the first threshold T... th1 If so, there is an abnormal connection in the three-phase copper busbar;

[0030] For the DC-side copper busbar, if the temperature difference between the DC positive (DC+) and negative (DC-) copper busbars is greater than the first threshold T... th1 If so, there is an abnormal connection between the DC positive (DC+) and negative (DC-) copper busbars.

[0031] Preferably, after the first protection action is executed, the photoelectric signal at the copper busbar is collected. If the arc light signal exceeds the limit, the second protection action is executed.

[0032] A third aspect of the present invention provides an electronic device including a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that the computer program, when loaded onto the processor, implements the protection method for the frequency converter according to the second aspect.

[0033] Compared with the prior art, the beneficial effects of the present invention include at least the following:

[0034] A temperature acquisition circuit is employed to collect temperature data from multiple copper busbars in the main circuit, while simultaneously acquiring current data from the copper busbars. Both data are sent to the MCU for processing. Analysis of the collected temperature and current data determines whether the copper busbar connections in each circuit are normal and whether they are in a safe operating state. If the temperature is normal and no electric arc is detected, the inverter operates normally. If the temperature is abnormal or an electric arc is detected, power limiting or even shutdown operations are implemented. This invention enhances the inverter's inspection and protection mechanisms to a certain extent. Attached Figure Description

[0035] Figure 1 A circuit diagram of a temperature measurement circuit provided for an embodiment of the present invention;

[0036] Figure 2 This is a current anomaly detection process provided in an embodiment of the present invention;

[0037] Figure 3 This is a copper busbar temperature anomaly detection process provided in an embodiment of the present invention;

[0038] Figure 4 The arc detection process provided in this embodiment of the invention. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of this invention. The described embodiments are merely some embodiments of this invention, and not all embodiments. Based on the spirit of this invention, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this invention.

[0040] Embodiment 1 of the present invention provides a frequency converter, including: AC side A, B, C three-phase copper busbars, DC side positive DC+ copper busbar, negative DC- copper busbar and midpoint O copper busbar, temperature measurement circuit, current measurement circuit and MCU.

[0041] The temperature measurement circuit is connected to the MCU and sends the sampled temperatures of each copper busbar to the MCU; specifically, as follows: Figure 1 The diagram shows a temperature measurement circuit using operational amplifiers provided in Embodiment 1 of the present invention. The temperature measurement circuit includes: a first operational amplifier OPA1, a second operational amplifier OPA2, a transistor VT1, and a load thermistor PT1.

[0042] In this circuit, the first operational amplifier OPA1 forms a constant current source circuit. It provides a stable first reference voltage V1 at the non-inverting input terminal of the first operational amplifier OPA1 and grounds it through capacitor C1. The inverting terminal is connected to the second reference voltage V2 through the current limiting resistor R1. The emitter of the transistor VT1 is connected to the inverting terminal, the base is connected to the output terminal of the first operational amplifier OPA1, and the collector is grounded through the load thermistor PT1.

[0043] One input terminal of the second operational amplifier OPA2 is connected to the collector of transistor VT1, and the other input terminal is connected to grounding resistor R3 and feedback resistor R2. The other end of feedback resistor R2 is connected to the output terminal of the second operational amplifier OPA2 and then to the ADC (Analog-to-Digital Converter).

[0044] It is understandable that the output of the first operational amplifier, OPA1, ensures that the operational amplifier operates in a normal state. The current flowing through the load thermistor PT1 can be expressed by the following formula:

[0045]

[0046] In the formula:

[0047] I is the current flowing through the load thermistor PT1;

[0048] R1 is the resistance value of the current-limiting resistor;

[0049] V1 and V2 are the first and second reference voltages, respectively.

[0050] The current-limiting resistor R1 and the load thermistor PT1 are connected via transistor VT1. The resistance of the load thermistor PT1 changes according to the temperature of the copper busbar during operation. The second operational amplifier OPA2 is used to amplify the voltage signal obtained by the constant current source current flowing through the load thermistor PT1, as expressed by the following formula:

[0051]

[0052] In the formula:

[0053] R PT1 The resistance value of the load thermistor PT1;

[0054] VD is the voltage across the load thermistor PT1.

[0055] Therefore, the voltage signal input to the ADC can be expressed by the following formula:

[0056]

[0057] In the formula:

[0058] V sa This is the voltage signal input to the ADC;

[0059] R2 is the resistance value of the feedback resistor.

[0060] In other words, after being amplified by the first operational amplifier OPA1 and the second operational amplifier OPA2, the signal is fed into the ADC and processed by the DSP chip to obtain the temperature value. Simultaneously, by adjusting the second reference voltage V2, the first reference voltage V1, and the current-limiting resistor R1, the current of the constant current source can be adjusted, changing the output current I, which in turn affects the input of the first operational amplifier OPA1 and the second operational amplifier OPA2, allowing for the adjustment of appropriate parameters according to actual needs.

[0061] The current measurement circuit includes, but is not limited to, various current sensors or current transformers, which can be either electromagnetic or electronic acquisition devices. During the sampling period, multiple sampling points are buffered and substituted into current criteria to diagnose the connection status of the copper busbar.

[0062] The frequency converter also includes a photoelectric sensor, which is connected to the MCU and sends the acquired light signal of the electric arc to the MCU. If the light signal of the electric arc exceeds the limit, it is determined that the copper busbar connection is abnormal and a second protection action is executed.

[0063] Preferably, but not limitingly, the first protection action is to reduce the operating power of the frequency converter, and the second protection action is to shut down the frequency converter. After the first protection action is implemented, the photoelectric sensor sampling action is activated. That is, the first protection action and the second protection action are implemented in sequence to reduce the false action of direct shutdown caused by disturbance.

[0064] The process by which the temperature measurement circuit, the current measurement circuit, and the photoelectric sensor transmit data back to the MCU for processing and calculation, and generate corresponding control actions, can be found in the following embodiments. More preferably, but not limitingly, the frequency converter can display data acquisition messages on the host computer interface through the 485 communication protocol, capture data according to the transmitted messages, and make corresponding judgments and controls based on the data information.

[0065] Embodiment 2 of the present invention provides a frequency converter protection method based on copper busbar abnormal connection detection, comprising the following steps:

[0066] Step 1: Start the sampling period, sample the current of each copper busbar, and send it to the MCU. The MCU diagnoses the operating status of the copper busbars based on the current of each copper busbar, including: if the current of a single copper busbar exceeds the limit of the range or the current change rate exceeds the limit within the sampling period, the copper busbar connection is determined to be abnormal, and an abnormal state 1 is considered to exist, and the first protection action is executed.

[0067] Preferred, but not limiting, such as Figure 2 The diagram illustrates the current anomaly detection method provided by this invention. Specifically, the current of each copper busbar is collected, the data of each sampling point is buffered within the sampling period, and then sent to the inverter MCU. For any copper busbar, if the current range is greater than a set current threshold and the current change rate is greater than a set change rate threshold, the copper busbar is determined to be in an abnormal state, possibly indicating an electric arc. If either the current range is greater than the set current threshold or the current change rate is greater than the set change rate threshold, the next sampling period begins immediately after the current sampling period ends, and the detection is repeated. If the current range is less than or equal to the set current threshold and the current change rate is less than or equal to the set change rate threshold, the copper busbar is determined to be operating normally within the current sampling period, and the system waits for the next sampling period.

[0068] The current range criterion and the current rate of change criterion are expressed by the following formulas (4) and (5):

[0069] I max -I min >I th (4)

[0070]

[0071] In the formula:

[0072] I max I min These represent the maximum and minimum values ​​of the copper busbar current during the sampling period, respectively.

[0073] I th The current threshold;

[0074] ΔI is the current difference between two adjacent current sampling points;

[0075] Δt is the time interval between two adjacent current sampling points.

[0076] Preferably, but not limitingly, the time interval between sampling periods can be 0 or a set value. Those skilled in the art can strike a balance between security needs and resource consumption. In scenarios with high security levels, the interval between sampling periods can be shortened until it is reduced to 0, i.e., real-time monitoring of the copper busbar. Alternatively, in scenarios with good equipment health, the sampling period interval can be appropriately extended. More preferably, the sampling period interval can be dynamically set, and a criterion can be set to adjust the sampling period interval.

[0077] Step 2: During the sampling period, the temperature of each copper busbar is obtained by sampling and sent to the MCU. The MCU diagnoses the operating status of the copper busbar based on the temperature of each copper busbar, including: if the temperature of a single copper busbar exceeds the limit or the temperature difference between copper busbars of the same type exceeds the limit, the copper busbar connection is determined to be abnormal, and an abnormal state 2 is considered to exist, and the first protection action is executed.

[0078] Preferably, but not limitingly, the first protection action is for the MCU to issue a control command to reduce the operating power of the frequency converter.

[0079] Preferably, but not limitingly, the abnormal copper busbar connection includes, but is not limited to, loose fixing screws, defects in the copper busbar manufacturing process, and incorrect selection, all of which can cause a significant increase in the copper busbar temperature during operation.

[0080] Preferred, but not limiting, such as Figure 3 As shown, this embodiment of the invention provides a copper busbar temperature anomaly detection process. By placing thermistors near the AC A, B, and C three-phase copper busbars, the DC positive (DC+) copper busbar, the DC negative (DC-) copper busbar, and the midpoint O copper busbar, the temperature and voltage values ​​T are obtained through a temperature measurement circuit. A T B T C T + , - T O The data is then sent to the MCU for judgment and processing.

[0081] Under normal operating conditions, the currents in the three-phase copper busbars (A, B, and C) should be consistent, and their temperatures should be relatively similar. For the AC side copper busbars, if the temperature difference between any two phases exceeds the first threshold value T... th1 If this is detected, it can be determined that there is an abnormal connection in the three-phase copper busbar. Abnormal conditions also include temperatures exceeding the second threshold T. th2If the temperature deviation is small, it is in a normal state. For abnormal situations, reduce power as needed, i.e., the first protection action. The same logic applies to the positive DC+ copper busbar, negative DC- copper busbar, and midpoint O copper busbar. It is worth noting that under normal circumstances, the current flowing through the positive DC+ and negative DC- copper busbars is the same, and a similar judgment can be made based on the AC side. However, the midpoint O copper busbar requires separate judgment.

[0082] More specifically, the statement that if the temperature of a single copper busbar exceeds the limit, the copper busbar connection is determined to be abnormal, and the first protection action is executed specifically includes: for the AC side copper busbars, if the temperature of any one of the three phases A, B, and C copper busbars exceeds the second threshold T... th2 If any one of the following formulas (6), (7), or (8) is true, then there is a connection abnormality in the three-phase copper busbar.

[0083] T A >T th2 (6)

[0084] T B >T th2 (7)

[0085] T C >T th2 (8)

[0086] In the formula:

[0087] T A T B T C These represent the temperatures of the three-phase copper busbars, A, B, and C, respectively.

[0088] T th2 This is the second threshold.

[0089] For the DC-side copper busbar, if the temperature of either the positive DC+ or negative DC- busbar is greater than the second threshold T... th2 If the DC positive (DC+) and negative (DC-) copper busbars are not connected correctly, then there is a connection abnormality. Specifically, if the following formula (9) or (10) holds true, then there is a connection abnormality between the DC positive (DC+) and negative (DC-) copper busbars.

[0090] T + >T th2 (9)

[0091] T - >T th2 (10)

[0092] In the formula:

[0093] T + T -These are the temperatures of the DC positive (DC+) and negative (DC-) copper busbars, respectively.

[0094] T th2 This is the second threshold.

[0095] For the copper busbar at midpoint O, if its temperature is greater than the second threshold T th2 If the following formula holds true, then the copper busbar at midpoint O has a connection anomaly.

[0096] T O >T th2 (11)

[0097] In the formula:

[0098] T O The temperature of the copper busbar at the midpoint O is given.

[0099] More specifically, the statement that if the temperature difference between copper busbars of the same type exceeds the limit, the copper busbar connection is determined to be abnormal, and the first protection action is executed specifically includes: for AC side copper busbars, if the temperature difference between any two phases of the three-phase copper busbars A, B, and C is greater than the first threshold T th1 If any one of the following formulas (12), (13), or (14) is true, then there is a connection abnormality in the three-phase copper busbar.

[0100] |T A -T B |>T th1 (12)

[0101] |T B -T C |>T th1 (13)

[0102] |T C -T C |>T th1 (14)

[0103] In the formula:

[0104] T A T B T C These represent the temperatures of the three-phase copper busbars, A, B, and C, respectively.

[0105] T th1 This is the first threshold.

[0106] For the DC-side copper busbar, if the temperature difference between the DC positive (DC+) and negative (DC-) copper busbars is greater than the first threshold T... th1If the DC positive (DC+) and negative (DC-) copper busbars are not connected correctly, then there is a connection abnormality. Specifically, if the following formula (15) holds true, then there is a connection abnormality between the DC positive (DC+) and negative (DC-) copper busbars.

[0107] |T + -T - |>T th1 (15)

[0108] In the formula:

[0109] T + T - These are the temperatures of the DC positive (DC+) and negative (DC-) copper busbars, respectively.

[0110] T th1 This is the first threshold.

[0111] Step 3: If the first protection action has been performed, it indicates that the risk of electric arc has increased. Initiate photoelectric signal sampling. If the electric arc light signal exceeds the limit, then execute the second protection action.

[0112] Specifically, such as Figure 4 As shown, changes in current can trigger an electric arc, which in turn alters the circuit's resistance, further affecting the current. Simultaneously, higher current generates more heat and higher temperatures, reducing the insulation performance of materials and increasing the probability of an electric arc. Therefore, when the current exceeds a threshold, monitoring the temperature change of the copper busbar is crucial. If the current and temperature of the copper busbar rise rapidly, it indicates an increased risk of an electric arc. Thus, current and temperature changes can serve as auxiliary criteria for arc detection, and their coordinated use can improve the effectiveness of detection and prevention. In other words, by configuring a photoelectric sensor at a preset location, based on the spectral characteristics of the electric arc, when abnormal temperature and current signals are detected, the system determines whether to trigger a shutdown action based on whether the effectively captured arc light signal exceeds the corresponding threshold. If the threshold is exceeded, an abnormal state is considered to exist.

[0113] Overall, the system first executes relevant actions based on the detected current and temperature status, then confirms whether an electric arc has occurred based on the photoelectric signal status. If an abnormal state 1 or 2 is detected, the MCU immediately issues a power-limiting command; if an abnormal state 3 is detected, the system should be shut down immediately to ensure safety. If the system is in a normal state, the MCU does not perform any operation, and the system continues to run.

[0114] Embodiment 3 of the present invention provides an electronic device, including a memory, a processor, and a computer program stored in the memory and executable on the processor. When the computer program is loaded onto the processor, it implements the protection method for the frequency converter according to Embodiment 2.

[0115] Embodiment 4 of the present invention provides a computer-readable storage medium storing a computer program that, when executed by a processor, implements the inverter protection method according to Embodiment 2.

[0116] It is worth noting that, as a prominent and substantial feature of this invention, during inverter operation, the temperature of the copper busbars in the main circuit and the presence of electric arcs are detected to determine whether the copper busbar connections are normal, thereby ensuring the normal operation of the inverter. Specifically, this invention obtains temperature data from multiple copper busbars in the main circuit through a temperature acquisition circuit designed for verification, and collects current data through a current sensor. The collected data are then sent to the MCU for analysis and judgment. This dual mechanism determines whether the copper busbar connections in each circuit are normal and whether they are in a safe operating state, thereby increasing the inverter's inspection and protection mechanism and ensuring the safe operation of the inverter.

[0117] It is worth noting that in the embodiments of the present invention, "steps + numbers" is only an expression for clearly describing the specific implementation of the protection method of the frequency converter, and not an absolute restriction on the order of the steps. Under the guidance of the core concept of the present invention, changing the order of these steps to obtain the same or similar technical effects all fall within the scope of the present invention.

[0118] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and not to limit it. Although the present invention has been described in detail with reference to the above embodiments, those skilled in the art should understand that modifications or equivalent substitutions can still be made to the specific implementation of the present invention. Any modifications or equivalent substitutions that do not depart from the spirit and scope of the present invention should be covered within the protection scope of the claims of the present invention.

Claims

1. A frequency converter, characterized in that, include: Multiple copper busbars, temperature measurement circuit, current measurement circuit, and MCU; The temperature measurement circuit is connected to the MCU and sends the sampled temperature of each copper busbar to the MCU; The current measurement circuit is connected to the MCU and sends the sampled current of each copper busbar to the MCU; The MCU diagnoses the operating status of the copper busbars based on the temperature of each copper busbar, including: if the temperature of a single copper busbar exceeds the limit or the temperature difference between copper busbars of the same type exceeds the limit, the copper busbar connection is determined to be abnormal and the first protection action is executed. The MCU diagnoses the operating status of the copper busbars based on the current of each copper busbar, including: if the current of a single copper busbar exceeds the limit in the sampling period and the current change rate exceeds the limit, then the copper busbar connection is determined to be abnormal and the first protection action is executed.

2. The frequency converter according to claim 1, characterized in that: The temperature measurement circuit includes a thermistor and a sampling circuit, with the thermistor located at each copper busbar. The voltage of the thermistor is obtained by sampling circuit, and the temperature of each copper busbar is obtained by conversion.

3. The frequency converter according to claim 1, characterized in that: The temperature measurement circuit includes: a first operational amplifier OPA1, a second operational amplifier OPA2, a transistor VT1, an ADC, and a load thermistor PT1. The non-inverting input terminal of the first operational amplifier OPA1 is connected to the first reference voltage V1 and grounded through capacitor C1; the inverting input terminal is connected to the second reference voltage V2 through current limiting resistor R1; the emitter of the transistor VT1 is connected to the inverting input terminal; the base is connected to the output terminal of the first operational amplifier OPA1; and the collector is grounded through the load thermistor PT1. One input terminal of the second operational amplifier OPA2 is connected to the collector of the transistor VT1, and the other input terminal is connected to the grounding resistor R3 and the feedback resistor R2. The other end of the feedback resistor R2 is connected to the output terminal of the second operational amplifier OPA2 and then to the ADC.

4. A frequency converter according to any one of claims 1 to 3, characterized in that: The frequency converter also includes a photoelectric sensor, which is connected to the MCU and sends the acquired light signal of the electric arc to the MCU. If the light signal of the electric arc exceeds the limit, it is determined that the copper busbar connection is abnormal and a second protection action is executed.

5. A protection method for a frequency converter, based on the frequency converter as described in any one of claims 1 to 4, characterized in that, Includes the following steps: Start the sampling period, sample the current of each copper busbar, and diagnose the operating status of the copper busbar based on the current of each copper busbar, including: if the current of a single copper busbar exceeds the range limit and the current change rate exceeds the limit within the sampling period, it is determined that the copper busbar connection is abnormal and the first protection action is executed. The temperature of each copper busbar is obtained by sampling, and the operating status of the copper busbar is diagnosed based on the temperature of each copper busbar, including: if the temperature of a single copper busbar exceeds the limit or the temperature difference between copper busbars of the same type exceeds the limit, the copper busbar connection is determined to be abnormal and the first protection action is executed.

6. The protection method for a frequency converter according to claim 5, characterized in that: The sampling period is initiated to sample the current of each copper busbar. Based on the current of each copper busbar, the operating status of the copper busbars is diagnosed, including: The current of each copper busbar is collected, the data of each sampling point is buffered within the sampling period, and then sent to the inverter MCU for diagnosis. For any copper busbar, if the current range is greater than the set current threshold and the current change rate is greater than the set change rate threshold, then the copper busbar is determined to be in an abnormal state. If either the current range is greater than the set current threshold or the current change rate is greater than the set change rate threshold, then after the current sampling period ends, the next sampling period will begin immediately for repeated detection. If the current range is less than or equal to the set current threshold and the current change rate is less than or equal to the set change rate threshold, then the copper busbar is determined to be operating normally within the sampling period, and the next sampling period will be waited for.

7. The protection method for a frequency converter according to claim 5, characterized in that: If the temperature of a single copper busbar exceeds the limit, the copper busbar connection is determined to be abnormal, and the first protection action is executed, including: For the AC side copper busbars, if the temperature of any one of the three phase copper busbars (A, B, and C) is greater than the second threshold T... th2 If so, there is an abnormal connection in the three-phase copper busbar; For the DC-side copper busbar, if the temperature of either the positive DC+ or negative DC- busbar is greater than the second threshold T... th2 If the DC positive (DC+) and negative (DC-) copper busbars are not connected correctly, then there is a connection abnormality. For the midpoint O copper busbar, if its temperature is greater than the second threshold T... th2 If the copper busbar at midpoint O has a connection anomaly, then there is an anomaly.

8. The protection method for a frequency converter according to claim 5, characterized in that: If the temperature difference between copper busbars of the same type exceeds the limit, the copper busbar connection is determined to be abnormal, and the first protection action is executed, including: For the AC side copper busbar, if the temperature difference between any two phases of the three-phase copper busbars A, B, and C is greater than the first threshold T... th1 If so, there is an abnormal connection in the three-phase copper busbar; For the DC-side copper busbar, if the temperature difference between the DC positive (DC+) and negative (DC-) copper busbars is greater than the first threshold T... th1 If so, there is an abnormal connection between the DC positive (DC+) and negative (DC-) copper busbars.

9. A protection method for a frequency converter according to claim 5, characterized in that: After the first protection action is executed, the photoelectric signal at the copper busbar is collected. If the arc light signal exceeds the limit, the second protection action is executed.

10. An electronic device comprising a memory, a processor, and a computer program stored in the memory and executable on the processor, characterized in that, When the computer program is loaded into the processor, it implements the protection method for the frequency converter according to any one of claims 5 to 9.

Images