A method for correcting the bus voltage of a mine - used modular four - quadrant frequency converter

Abstract

The present invention relates to the technical field of frequency converters, and specifically discloses a method for correcting the bus voltage of a mine-used modular four-quadrant frequency converter. The method includes the following steps: obtaining the actual value of the AC incoming line voltage, the actual value of the rectifier-side bus voltage, and the actual value of the inverter-side bus voltage; correcting the bus voltage value of the frequency converter according to the actual value of the AC incoming line voltage, the actual value of the rectifier-side bus voltage, and the actual value of the inverter-side bus voltage. By adding a bus voltage detection circuit inside the modular frequency converter and correcting the bus voltage detection value by taking the average of two detection values, the present invention can further accurately determine the fault problems of the AC incoming line voltage detection circuit and the two bus detection circuits, solve the problems of misoperation and misprotection of the four-quadrant frequency converter caused by inaccurate bus voltage detection, improve the reliability of the equipment, and at the same time can accurately determine the fault problems of the voltage detection circuit, improving the work efficiency of after-sales and maintenance personnel.

Description

Technical Field

[0001] The present invention specifically relates to the technical field of frequency converters, and more specifically to a method for correcting the bus voltage of a mine-used modular four-quadrant frequency converter. Background Art

[0002] In the coal mine field, frequency converters are mainly applied to the traveling drive systems of electric haulage equipment, transportation systems such as belts and scraper conveyors, and speed regulation systems such as fans and water pumps, mainly for the purposes of speed regulation and energy saving. Among them, the frequency converters used for loads such as fans and water pumps are basically two-quadrant frequency converters. Both two-quadrant and four-quadrant frequency converters are used in transportation systems such as belts and scraper conveyors. Considering the dynamic response speed during the walking of the equipment, the frequency converters used for mine electric haulage equipment basically adopt mine-used four-quadrant frequency converters for driving. Due to the strict restrictions on the volume of the electric control box for mine vehicle-mounted equipment, most mine-used four-quadrant frequency converters are installed inside the explosion-proof box shell in a modular form, which reduces the volume of the frequency converter while increasing the protection ability of the frequency converter, improves the reliability of the frequency converter and facilitates maintenance personnel to diagnose the faults of the frequency converter. Due to the harsh working conditions of mine-used modular four-quadrant frequency converters, affected by factors such as device quality, welding process, installation process, dust, humidity, vibration, and heat dissipation, the bus voltage detection circuit of the frequency converter may have inaccurate detection, resulting in the four-quadrant frequency converter delaying to enter the energy feedback state or entering the energy feedback state in advance, and misoperation of the over- and under-voltage protection of the DC bus. In severe cases, it may cause damage to the main circuit devices and pose a danger.

[0003] In the prior art with the authorization announcement number CN112798997B, the DC voltage detection value at the rear end is corrected based on the detected AC incoming line voltage value at the front end, and the voltage calculation coefficient is adjusted. The DC voltage detection can only basically conform to the actual value, enabling the frequency converter to operate within a certain range of deviation of the detected voltage of the DC bus.

[0004] The prior art with the authorization announcement number CN109582071B is for a distributed variable current system, rather than a modular frequency converter system. At the same time, this method calibrates the bus voltage values of each subsystem by sending bus voltage calibration coefficients to each subsystem, rather than the actual detected values, which is still not accurate enough for mine-used modular four-quadrants. Summary of the Invention

[0005] The object of the present invention is to provide a method for correcting the bus voltage of a mine - used modular four - quadrant frequency converter, so as to solve the problem proposed in the above - mentioned background technology. Due to the harsh operating conditions of the mine - used modular four - quadrant frequency converter, affected by factors such as device quality, welding process, installation process, dust, humidity, vibration, and heat dissipation, the bus voltage detection circuit of the frequency converter will have inaccurate detection, resulting in the four - quadrant frequency converter delaying or advancing into the energy feedback state, misoperation of the DC bus over - under voltage protection, and in severe cases, damage to the main circuit devices and occurrence of danger.

[0006] To achieve the above object, the present invention provides the following technical solutions:

[0007] A method for correcting the bus voltage of a mine - used modular four - quadrant frequency converter, which is applied to a mine - used modular four - quadrant frequency converter. The mine - used modular four - quadrant frequency converter includes a rectifier circuit, a DC pre - charge circuit, a DC support capacitor C1, a discharge resistor R2, an inverter circuit, an incoming - line voltage detection circuit, a rectifier - side bus detection circuit, and an inverter - side bus detection circuit. The detection point of the incoming - line voltage detection circuit is set at the front end of the rectifier circuit, the detection point of the rectifier - side bus detection circuit is set between the rectifier circuit and the DC pre - charge circuit; the detection point of the inverter - side bus detection circuit is set between the DC pre - charge circuit and the inverter circuit. The method for correcting the bus voltage of the mine - used modular four - quadrant frequency converter includes the following steps:

[0008] S101. After the frequency converter is powered on, obtain the actual value VIn of the AC incoming - line voltage, the actual value VDCLink1 of the rectifier - side bus voltage, and the actual value VDCLink2 of the inverter - side bus voltage;

[0009] S102. According to the actual value V In of the AC incoming - line voltage, the actual value V DCLink1 of the rectifier - side bus voltage, and the actual value V DCLink2 of the inverter - side bus voltage, calculate the correction value of the bus voltage of the frequency converter, and correct the bus voltage value of the frequency converter through the correction value of the bus voltage of the frequency converter.

[0010] As a further solution of the present invention: The rectifier circuit is connected to the three - phase power supply line of the power grid. The rectifier circuit includes three rectifier branches arranged in parallel. Each rectifier branch includes two series - connected switching tubes, and each switching tube is anti - paralleled with a diode. The connection node between the two switching tubes in each rectifier branch is connected with a wire, and the three rectifier branches are respectively connected to the three - phase power supply line through the wire.

[0011] As a further solution of the present invention: the inverter circuit includes three parallel-connected inverter branches, each inverter branch includes two series-connected switching tubes, each switching tube is anti-parallel connected with a diode, a wire is connected to the connection node between the two switching tubes in each inverter branch, and the three inverter branches are respectively connected to the three-phase power supply lines of the motor through wires.

[0012] As a further solution of the present invention: the DC pre-charge circuit includes a resistor R1 and a switch S1 connected in parallel with the resistor R1. One end of the resistor R1 is connected to the negative electrode of the diode in the three rectifier branches, and the other end of the resistor R1 is connected to the negative electrode of the diode in the three inverter branches.

[0013] As a further solution of the present invention: the DC support capacitor C1 is arranged between the rectifier circuit and the inverter circuit, the DC support capacitor C1 is connected in parallel with the rectifier circuit and the inverter circuit, and a discharge resistor R2 is connected in parallel with the DC support capacitor C1.

[0014] As a further solution of the present invention: in S101, the actual value V of the AC incoming line voltage In is calculated through the incoming line voltage detection circuit, and the actual value V of the rectifier side bus voltage DCLink1 is calculated through the rectifier side bus detection circuit, and the actual value V of the inverter side bus voltage DCLink2 is calculated through the inverter side bus detection circuit.

[0015] As a further solution of the present invention: in S102, the method for correcting the bus voltage value of the frequency converter includes the following steps:

[0016] S201. Calculate the estimated value V of the bus voltage DCLink3 = k * V In , where k > 0. It should be noted that k is the rectification coefficient. According to the calculation formula of the three-phase full-bridge rectifier circuit in the prior art, k generally takes values in the range of 1.35 to 1.414; V In is the actual value of the AC incoming line voltage;

[0017] S202. Judge whether the value ranges of the actual value V of the rectifier side bus voltage DCLink1 , the actual value V of the inverter side bus voltage DCLink2 and the calculated estimated value V of the bus voltage DCLink3 meet the conditional formula. When the judgment result is yes, calculate the correction value of the bus voltage of the frequency converter, otherwise, perform S203. Among them: the conditional formula is:

[0018] x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 holds, x 1* VDCLink3 <V DCLink2 <x 2* V DCLink3 also holds, where 0 < x1 < 1 and 1 < x2 < 2;

[0019] The calculation formula for the corrected value of the converter bus voltage is: V DCLink =(V DCLink1 + V DCLink2 ) / 2.

[0020] S203. Determine the type of converter fault. The types of converter faults include: inverter-side bus voltage detection fault, rectifier-side bus voltage detection fault, and incoming-line voltage detection fault, where:

[0021] If x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 holds, x 1* V DCLink3 < V DCLink2 < x 2* V DCLink3 does not hold, where 0 < x1 < 1 and 1 < x2 < 2, the fault type is inverter-side bus voltage detection fault, and the converter stops;

[0022] If x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 does not hold, x 1* V DCLink3 < V DCLink2 < x 2* V DCLink3 holds, where 0 < x1 < 1 and 1 < x2 < 2, the fault type is rectifier-side bus voltage detection fault, and the converter stops;

[0023] If x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 does not hold, x 1* V DCLink3 < V DCLink2 < x 2* V DCLink3 does not hold, where 0 < x1 < 1 and 1 < x2 < 2, the fault type is incoming-line voltage detection fault reported, and the converter stops.

[0024] In steps S202 and S203, x1 and x2 are allowable deviation coefficients.

[0025] As a further solution of the present invention: there is also a method for judging the energy feedback action according to the corrected value of the inverter bus voltage, including the following steps: judging whether the corrected value V of the inverter bus voltage DCLink <V R holds. If so, the inverter is in the normal running electric state; otherwise, the controllable power device acts and the inverter is in the energy feedback state, where V R is the energy feedback bus voltage threshold.

[0026] As a further solution of the present invention: there is also a method for judging over-voltage and under-voltage protection of the bus voltage according to the corrected value of the inverter bus voltage, including the following steps:

[0027] S301. Judge whether the corrected value V of the inverter bus voltage DCLink is greater than or equal to V min and less than or equal to V max . If so, the inverter runs normally; otherwise, proceed to S302;

[0028] S302. Judge whether the corrected value V of the inverter bus voltage DCLink is greater than V max . If so, the inverter stops, and there is an over-voltage protection fault in the DC bus; otherwise, the inverter stops, and there is an under-voltage protection fault in the DC bus.

[0029] Compared with the prior art, the beneficial effects of the present invention are as follows: by adding a bus voltage detection circuit inside the modular inverter, the detected value of the bus voltage is corrected by taking the average value of two detected values, and the detection points of the two bus voltage detection circuits are different. One bus voltage detection circuit has a detection point close to the rectifier circuit, after the rectifier circuit and before the DC pre-charge circuit, and the other bus voltage detection circuit has a detection point close to the inverter circuit, after the DC pre-charge circuit and before the inverter circuit. In addition, by estimating the bus voltage through the real-time monitored value of the AC incoming line voltage and comparing it with the detected values of the two bus voltage detection circuits, it is possible to further accurately judge the fault problems of the AC incoming line voltage detection circuit and the two bus detection circuits, solve the problem of misoperation and misprotection of the four-quadrant inverter caused by inaccurate bus voltage detection, improve the reliability of the equipment, and at the same time accurately judge the fault problems of the voltage detection circuit, improving the work efficiency of after-sales and maintenance personnel. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is the circuit diagram of the mine-used modular four-quadrant inverter in the mine-used modular four-quadrant inverter bus voltage correction method.

[0031] Figure 2 is the flow chart of the mine-used modular four-quadrant inverter bus voltage correction method.

[0032] Figure 3 It is a flowchart of a method for correcting the bus voltage value of a mine - used modular four - quadrant frequency converter in the bus voltage correction method of the mine - used modular four - quadrant frequency converter.

[0033] Figure 4 It is a flowchart of a method for determining the energy feedback action according to the bus voltage correction value of a mine - used modular four - quadrant frequency converter in the bus voltage correction method of the mine - used modular four - quadrant frequency converter.

[0034] Figure 5 It is a flowchart of a method for judging over - voltage and under - voltage protection of the bus voltage according to the bus voltage correction value of a mine - used modular four - quadrant frequency converter in the bus voltage correction method of the mine - used modular four - quadrant frequency converter. Specific embodiments

[0035] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present invention.

[0036] Due to the harsh operating conditions of the mine - used modular four - quadrant frequency converter, affected by factors such as device quality, welding process, installation process, dust, humidity, vibration, and heat dissipation, the bus voltage detection circuit of the frequency converter may have inaccurate detection, resulting in the four - quadrant frequency converter delaying or advancing into the energy feedback state, and misoperation of the over - voltage and under - voltage protection of the DC bus. In severe cases, it may cause damage to the main circuit devices and pose a danger.

[0037] Based on this, please refer to Figure 1 In an embodiment of the present invention, a method for correcting the bus voltage of a mine - used modular four - quadrant frequency converter is applied to a mine - used modular four - quadrant frequency converter. The mine - used modular four - quadrant frequency converter includes a rectifier circuit, a DC pre - charge circuit, a DC support capacitor C1, a discharge resistor R2, and an inverter circuit.

[0038] In an embodiment of the present application, the rectifier circuit is connected to the three - phase power supply lines (R / S / T) of the power grid. The rectifier circuit includes three rectifier branches connected in parallel ( Figure 1 two rectifier branches are omitted), and each rectifier branch includes two series - connected switching tubes. Each switching tube is anti - paralleled with a diode. The connection node between the two switching tubes in each rectifier branch is connected by a wire, and the three rectifier branches are respectively connected to the three - phase power supply lines through the wires;

[0039] The inverter circuit includes three inverter branches connected in parallel ( Figure 1In the figure, two inverter branches are omitted. Each inverter branch includes two series-connected switching tubes, and each switching tube is anti-parallel connected with a diode. A wire is connected to the connection node between the two switching tubes in each inverter branch. The three inverter branches are respectively connected to the three-phase power supply lines of the motor through wires.

[0040] The DC pre-charge circuit includes a resistor R1 and a switch S1 connected in parallel with the resistor R1. One end of the resistor R1 is connected to the negative electrodes of the diodes in the three rectifier branches, and the other end of the resistor R1 is connected to the negative electrodes of the diodes in the three inverter branches. The DC support capacitor C1 is arranged between the rectifier circuit and the inverter circuit, and the DC support capacitor C1 is connected in parallel with the rectifier circuit and the inverter circuit. A discharge resistor R2 is connected in parallel with the DC support capacitor C1.

[0041] When the motor is in the motoring state in the four-quadrant frequency converter, the three-phase alternating current of the power grid flows into the rectifier circuit. The three-phase alternating current of the power grid is converted into direct current through the diodes anti-parallel connected with the switching tubes in the three rectifier branches of the rectifier circuit. The direct current reaches the inverter circuit after passing through the DC support capacitor C1, and the inverter circuit converts the direct current into three-phase alternating current for driving the motor to work.

[0042] Please refer here Figure 1 In the embodiment of the present application, the mine-used modular four-quadrant frequency converter further includes an incoming line voltage detection circuit, a rectifier side bus detection circuit, and an inverter side bus detection circuit. The detection point of the incoming line voltage detection circuit is arranged at the front end of the rectifier circuit. The detection point of the rectifier side bus detection circuit is arranged between the rectifier circuit and the DC pre-charge circuit. Specifically, the detection point of the rectifier side bus detection circuit is arranged at the rear end of the rectifier circuit and the front end of the DC pre-charge circuit. The detection point of the inverter side bus detection circuit is arranged between the DC pre-charge circuit and the inverter circuit. Specifically, the detection point of the inverter side bus detection circuit is arranged at the rear end of the DC pre-charge circuit and the front end of the inverter circuit.

[0043] Please refer to Figure 2 The bus voltage correction method of the mine-used modular four-quadrant frequency converter includes the following steps:

[0044] S101. After the frequency converter is powered on, obtain the actual value V In of the AC incoming line voltage, the actual value V DCLink1 of the rectifier side bus voltage, and the actual value V DCLink2 of the inverter side bus voltage;

[0045] In step S101 of the embodiment of the present application, the actual value V In of the AC incoming line voltage is calculated through the incoming line voltage detection circuit, the actual value V DCLink1 of the rectifier side bus voltage is calculated through the rectifier side bus detection circuit, and the actual value V DCLink2Calculated by the bus detection circuit on the inverter side;

[0046] S102. According to the actual value V of the AC incoming line voltage In , the actual value V of the rectifier side bus voltage DCLink1 and the actual value V of the inverter side bus voltage DCLink2 calculate the correction value of the converter bus voltage, and correct the converter bus voltage value through the correction value of the converter bus voltage;

[0047] Please refer to Figure 3 , in step S102 of the embodiment of the present application, the method for correcting the converter bus voltage value includes the following steps:

[0048] S201. Calculate the estimated value V of the bus voltage DCLink3 = k * V In , where k > 0. It should be noted that k is the rectification coefficient. According to the three-phase full-bridge rectifier circuit calculation formula in the prior art, k generally takes values in the range of 1.35 to 1.414; V In is the actual value of the AC incoming line voltage;

[0049] S202. Judge whether the value ranges of the actual value V of the rectifier side bus voltage DCLink1 , the actual value V of the inverter side bus voltage DCLink2 and the calculated estimated value V of the bus voltage DCLink3 satisfy the conditional formula. When the judgment result is yes, calculate the correction value of the converter bus voltage; otherwise, perform S203. Among them: the conditional formula is:

[0050] x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 holds, and x 1* V DCLink3 < V DCLink2 < x 2* V DCLink3 also holds, where 0 < x1 < 1 and 1 < x2 < 2;

[0051] The calculation formula for the correction value of the converter bus voltage is: V DCLink = (V DCLink1 + V DCLink2 ) / 2.

[0052] S203. Judge the type of converter fault. The types of converter faults include: inverter side bus voltage detection fault, rectifier side bus voltage detection fault, and incoming line side voltage detection fault. Among them:

[0053] If x 1* V DCLink3 < V DCLink1<x 2* V DCLink3 is established, x 1* V DCLink3 <V DCLink2 <x 2* V DCLink3 is not established, where 0 < x1 < 1 and 1 < x2 < 2, the fault type is the inverter-side bus voltage detection fault, and the frequency converter stops;

[0054] If x 1* V DCLink3 <V DCLink1 <x 2* V DCLink3 is not established, x 1* V DCLink3 <V DCLink2 <x 2* V DCLink3 is established, where 0 < x1 < 1 and 1 < x2 < 2, the fault type is the rectifier-side bus voltage detection fault, and the frequency converter stops;

[0055] If x 1* V DCLink3 <V DCLink1 <x 2* V DCLink3 is not established, x 1* V DCLink3 <V DCLink2 <x 2* V DCLink3 is not established, where 0 < x1 < 1 and 1 < x2 < 2, the fault type is the incoming line voltage detection fault, and the frequency converter stops.

[0056] It should be noted that in steps S202 and S203 of this application, x1 and x2 are the allowable deviation coefficients, and the values of x1 and x2 are selected by those skilled in the art according to the actual situation. For example, it is considered that the bus voltage estimated value V DCLink3 with a positive deviation of 106% to a negative deviation of 95% belongs to the normal range, then x1 takes the value of 0.95 and x2 takes the value of 1.06.

[0057] Please refer to Figure 4 , in the embodiment of this application, there is also a method for determining the energy feedback action according to the bus voltage correction value of the frequency converter, including the following steps:

[0058] Judge whether the bus voltage correction value V of the frequency converter DCLink <V R is established. If so, the frequency converter is in the normal running electric state; otherwise, the controllable power device operates, and the frequency converter is in the energy feedback state, where V R is the energy feedback bus voltage threshold.

[0059] In addition, please refer to Figure 5 , in the embodiment of the present application, there is also a method for judging over-voltage and under-voltage protection of the bus voltage according to the corrected value of the inverter bus voltage, including the following steps:

[0060] S301. Judge whether the corrected value V of the inverter bus voltage DCLink is greater than or equal to V min and less than or equal to V max . If so, the inverter operates normally; otherwise, perform S302.

[0061] S302. Judge whether the corrected value V of the inverter bus voltage DCLink is greater than V max . If so, the inverter stops, and there is an over-voltage protection fault in the DC bus; otherwise, the inverter stops, and there is an under-voltage protection fault in the DC bus.

[0062] In summary, the present invention adds a bus voltage detection circuit inside the modular inverter, corrects the bus voltage detection value by taking the average of two detection values, and the detection points of the two bus voltage detection circuits are different. One bus voltage detection circuit has a detection point close to the rectifier circuit, after the rectifier circuit and before the DC pre-charge circuit, and the other bus voltage detection circuit has a detection point close to the inverter circuit, after the DC pre-charge circuit and before the inverter circuit. In addition, by estimating the bus voltage through the real-time monitoring value of the AC incoming line voltage and comparing it with the two bus voltage detection values, it is possible to further accurately judge the fault problems of the AC incoming line voltage detection circuit and the two bus detection circuits, solve the problem of misoperation and misprotection of the four-quadrant inverter caused by inaccurate bus voltage detection, improve the reliability of the equipment, and at the same time accurately judge the fault problems of the voltage detection circuit, improving the work efficiency of after-sales and maintenance personnel.

[0063] For those skilled in the art, it is obvious that the present invention is not limited to the details of the above exemplary embodiments, and can be implemented in other specific forms without departing from the spirit or basic characteristics of the present invention. Therefore, from any point of view, the embodiments should be regarded as exemplary and non-limiting. The scope of the present invention is defined by the appended claims rather than the above description. Therefore, it is intended to embrace all changes falling within the meaning and scope of the equivalent elements of the claims in the present invention. Any reference signs in the claims should not be regarded as limiting the claimed rights.

[0064] In addition, it should be understood that although this specification is described according to embodiments, not every embodiment only contains an independent technical solution. This narrative way of the specification is only for clarity. Those skilled in the art should regard the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A method for correcting the bus voltage of a mine - used modular four - quadrant frequency converter, which is applied to a mine - used modular four - quadrant frequency converter, is characterized in that, The mine-used modular four-quadrant frequency converter includes a rectifier circuit, a DC pre-charge circuit, a DC support capacitor C1, a discharge resistor R2, an inverter circuit, an incoming line voltage detection circuit, a rectifier-side bus detection circuit, and an inverter-side bus detection circuit. The detection point of the incoming line voltage detection circuit is set at the front end of the rectifier circuit. The detection point of the rectifier-side bus detection circuit is set between the rectifier circuit and the DC pre-charge circuit. The detection point of the inverter-side bus detection circuit is set between the DC pre-charge circuit and the inverter circuit. The bus voltage correction method of the mine-used modular four-quadrant frequency converter includes the following steps: S101. After the frequency converter is powered on, obtain the actual value V of the AC incoming line voltage In , the actual value V of the rectifier side bus voltage DCLink1 and the actual value V of the inverter side bus voltage DCLink2 ; S102. Calculate the correction value of the converter bus voltage according to the actual value V of the AC incoming line voltage In , the actual value V of the rectifier side bus voltage DCLink1 and the actual value V of the inverter side bus voltage DCLink2 . Correct the converter bus voltage value by the correction value of the converter bus voltage. The correction method includes the following steps: S201. Calculate the estimated value V of the bus voltage DCLink3 = k * V In , where k > 0, k is the rectification coefficient, and V In is the actual value of the AC line voltage; S202. Determine whether the actual value V of the rectifier side bus voltage DCLink1 , the actual value V of the inverter side bus voltage DCLink2 and the calculated value range of the estimated bus voltage V DCLink3 meet the conditional formula. When the judgment result is yes, calculate the correction value of the converter bus voltage; otherwise, perform S203. Wherein, the conditional formula is: x 1* V DCLink3 <V DCLink1 <x 2* V DCLink3 holds, x 1* V DCLink3 <V DCLink2 <x 2* V DCLink3 also holds, where 0 < x1 < 1, 1 < x2 < 2, and x1 and x2 are allowable deviation coefficients; The calculation formula for the correction value of the inverter bus voltage is: V DCLink =(V DCLink1 +V DCLink2 ) / 2; S203. Determine the type of frequency converter fault. The types of frequency converter faults include: inverter-side bus voltage detection fault, rectifier-side bus voltage detection fault, and incoming line side voltage detection fault, where: If x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 holds, x 1* V DCLink3 < V DCLink2 < x 2* V DCLink3 does not hold, where 0 < x1 < 1, 1 < x2 < 2, the fault type is the inverter-side bus voltage detection fault, and the frequency converter stops; If x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 does not hold, x 1* V DCLink3 < V DCLink2 < x 2* V DCLink3 holds, where 0 < x1 < 1, 1 < x2 < 2, the fault type is the rectifier side bus voltage detection fault, and the frequency converter stops; If x 1* V DCLink3 < V DCLink1 < x 2* V DCLink3 does not hold, x 1* V DCLink3 < V DCLink2 < x 2* V DCLink3 does not hold, where 0 < x1 < 1, 1 < x2 < 2, the fault type is reported as line-side voltage detection fault, and the frequency converter stops.

2. The method for correcting the bus voltage of the mine-used modular four-quadrant frequency converter according to claim 1, characterized in that, The rectifier circuit is connected to the three-phase power supply line of the power grid. The rectifier circuit includes three rectifier branches connected in parallel. Each rectifier branch includes two switch tubes connected in series. Each switch tube is anti-parallel with a diode. A wire is connected to the connection node between the two switch tubes in each rectifier branch. The three rectifier branches are respectively connected to the three-phase power supply line through the wires.

3. The method for correcting the bus voltage of the mine-used modular four-quadrant frequency converter according to claim 2, characterized in that, The inverter circuit includes three inverter branches connected in parallel. Each inverter branch includes two switch tubes connected in series. Each switch tube is anti-parallel with a diode. A wire is connected to the connection node between the two switch tubes in each inverter branch. The three inverter branches are respectively connected to the three-phase power supply line of the motor through the wires.

4. The method for correcting the bus voltage of the mine-used modular four-quadrant frequency converter according to claim 1, wherein, The DC pre-charge circuit includes a resistor R1 and a switch S1 connected in parallel with the resistor R1. One end of the resistor R1 is connected to the negative electrode of the diode in the three rectifier branches, and the other end of the resistor R1 is connected to the negative electrode of the diode in the three inverter branches.

5. The method for correcting the bus voltage of the mine-used modular four-quadrant frequency converter according to claim 3, characterized in that, The DC support capacitor C1 is set between the rectifier circuit and the inverter circuit. The DC support capacitor C1 is connected in parallel with the rectifier circuit and the inverter circuit. The discharge resistor R2 is connected in parallel with the DC support capacitor C1.

6. The method for correcting the bus voltage of the mine-used modular four-quadrant frequency converter according to claim 1, wherein In S101, the actual value V of the AC incoming line voltage In is calculated by the incoming line voltage detection circuit, and the actual value V of the rectifier side bus voltage DCLink1 is calculated by the rectifier side bus detection circuit, and the actual value V of the inverter side bus voltage DCLink2 is calculated by the inverter side bus detection circuit.

7. The method for correcting the bus voltage of the mine-used modular four-quadrant frequency converter according to claim 1, characterized in that, It also includes a method for judging the energy feedback operation according to the corrected value of the inverter bus voltage, which comprises the following steps: judging whether the corrected value V of the inverter bus voltage DCLink <V R holds. If so, the inverter is in the normal operation electric state; otherwise, the controllable power device operates and the inverter is in the energy feedback state, where V R is the energy feedback bus voltage threshold value.

8. The method for correcting the bus voltage of the mine-used modular four-quadrant frequency converter according to claim 1, wherein, It also includes a method for judging over-voltage and under-voltage protection of the bus voltage according to the bus voltage correction value of the frequency converter, including the following steps: S301. Determine whether the corrected value V of the inverter bus voltage DCLink is greater than or equal to V min and less than or equal to V max . If so, the inverter operates normally; otherwise, perform S301. S302. Determine whether the corrected value V of the inverter bus voltage DCLink is greater than V max . If so, stop the inverter, with a DC bus overvoltage protection fault; otherwise, stop the inverter, with a DC bus undervoltage protection fault.

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