Power grid side filter circuit and device

Abstract

The utility model discloses a power grid side filter circuit and device, and relates to the technical field of power electronics. The power grid side filter circuit comprises a frequency converter, a first Y capacitor, a second Y capacitor and a third Y capacitor. The frequency converter is electrically connected with a three-phase power grid power supply input end of a power grid and is electrically connected with the motor to form a main loop; a first pole of the first Y capacitor is electrically connected with a first-phase power grid power supply input end in the three-phase power grid power supply input ends, and a second pole of the first Y capacitor is electrically connected with a grounding end; the first pole of the second Y capacitor is electrically connected with the power supply input end of the second-phase power grid, and the second pole of the second Y capacitor is electrically connected with the grounding end; the first pole of the third Y capacitor is electrically connected with the power input end of the third-phase power grid, and the second pole of the third Y capacitor is electrically connected with the grounding end. According to the embodiment of the invention, the problems of leakage voltage and leakage current can be effectively improved, so that the working stability of equipment and the safety of operators can be fully improved.

Description

Technical Field

[0001] This utility model belongs to the field of power electronics technology, and in particular relates to a power grid-side filter circuit and device. Background Technology

[0002] In the field of power electronics, frequency converters are widely used in industrial and commercial sectors to achieve energy savings, improve process control precision, and enhance motor starting performance. However, during actual frequency converter startup and operation, leakage voltage and leakage current are generated by the internal inverter structure. This leakage current is often transmitted to the controlled motor through the connection between the inverter and the motor, then through the distributed capacitance between the motor windings and the motor housing, and finally back to the frequency converter through the shielding layer. If there is an abnormality in the frequency converter's grounding at this time, the corresponding casing of the frequency converter will become energized, which can easily cause electric shock accidents to construction workers, posing a significant safety hazard to equipment and operators, affecting system stability, and resulting in economic losses.

[0003] In view of the above, how to effectively suppress the leakage current problem in the aforementioned frequency converters, so as to fully improve the working stability of the grid-side filter device and the safety of operators, is an urgent problem to be solved in the industry. Utility Model Content

[0004] This application provides a grid-side filtering circuit and device that can effectively improve leakage voltage and leakage current during inverter operation, thereby significantly enhancing equipment stability and operator safety.

[0005] In a first aspect, embodiments of this application provide a grid-side filter circuit, which includes a frequency converter, a first Y capacitor, a second Y capacitor, and a third Y capacitor; the frequency converter is electrically connected to the three-phase power input terminal of the grid and electrically connected to a motor to form a main circuit;

[0006] The first terminal of the first Y capacitor is electrically connected to the first phase power input terminal of the three-phase power grid, and the second terminal of the first Y capacitor is electrically connected to the ground terminal.

[0007] The first terminal of the second Y capacitor is electrically connected to the second phase power input terminal of the three-phase power grid, and the second terminal of the second Y capacitor is electrically connected to the ground terminal.

[0008] The first terminal of the third Y capacitor is electrically connected to the third phase power input terminal of the three-phase power grid, and the second terminal of the third Y capacitor is electrically connected to the ground terminal.

[0009] In some possible implementations, the grid-side filter circuit further includes:

[0010] The switch protection module has its first terminal electrically connected to the target node and its second terminal electrically connected to the grounding terminal.

[0011] The switch protection module is used to connect or disconnect the target node and the ground terminal;

[0012] The target node is the common connection point of the second pole of the first Y capacitor, the second pole of the second Y capacitor, and the second pole of the third Y capacitor.

[0013] In some possible implementations, the grid-side filter circuit further includes:

[0014] The power-on detection module has its first signal input terminal electrically connected to the positive terminal of the DC bus in the frequency converter, its second signal input terminal electrically connected to the negative terminal of the DC bus in the frequency converter, and its signal output terminal electrically connected to the switch protection module.

[0015] The power-on detection module is used to determine whether the inverter has completed power-on by collecting voltage signals from the first signal input terminal and the second signal input terminal; and, if the inverter has completed power-on, it sends a conduction signal to the switch protection module through the signal output terminal so that the switch protection module connects the target node and the ground terminal.

[0016] If the inverter is determined to be not fully powered on, a shutdown signal is sent to the switch protection module through the signal output terminal so that the switch protection module disconnects the target node and the ground terminal.

[0017] In some possible implementations, the grid-side filtering circuit further includes a filtering protection module; the switch protection module is a relay or contactor, and the switch protection module includes a main contact pair for implementing the switching function and an auxiliary contact pair for control; the signal output terminal of the power-on detection module includes a first signal output terminal and a second signal output terminal;

[0018] The first sub-contact in the main contact pair is electrically connected to the target node, and the second sub-contact in the main contact pair is electrically connected to the grounding terminal.

[0019] The third sub-contact in the auxiliary contact pair is electrically connected to the first signal output terminal, and the fourth sub-contact in the auxiliary contact pair is electrically connected to the second signal output terminal.

[0020] The first end of the filter protection module is electrically connected to the third sub-contact, and the second end of the filter protection module is electrically connected to the fourth sub-contact.

[0021] In some possible implementations, the grid-side filtering circuit further includes a filtering protection module; the switching protection module is a power switching device; the switching protection module also includes a control terminal, which is electrically connected to the signal output terminal of the power-on detection module.

[0022] The first terminal of the filter protection module is electrically connected to the control terminal, and the second terminal of the filter protection module is electrically connected to the ground terminal.

[0023] In some possible implementations, the filtering protection module is a filtering capacitor.

[0024] In some possible implementations, the frequency converter includes a three-phase rectifier bridge and a three-phase inverter bridge; the output terminals of the three-phase rectifier bridge and the input terminals of the three-phase inverter bridge are electrically connected via a DC bus.

[0025] The input terminal of the three-phase rectifier bridge is electrically connected to the three-phase power input terminal of the power grid, and the output terminal of the three-phase inverter bridge is connected to the motor.

[0026] A three-phase rectifier bridge consists of six diodes and is used to convert the three-phase AC voltage input from the power grid into DC voltage.

[0027] The three-phase inverter bridge consists of six power switching transistors, which are used to convert DC voltage into three-phase AC voltage and output three-phase AC voltage to the motor.

[0028] In some possible implementations, the frequency converter also includes a first bus capacitor and a second bus capacitor;

[0029] The first terminal of the first bus capacitor is electrically connected to the positive terminal of the DC bus, and the second terminal of the first bus capacitor is electrically connected to the first terminal of the second bus capacitor.

[0030] The second terminal of the second bus capacitor is electrically connected to the negative terminal of the DC bus.

[0031] The first and second bus capacitors are used to filter and regulate the DC voltage output from the three-phase rectifier bridge.

[0032] In some possible implementations, the first Y capacitor, the second Y capacitor, and the third Y capacitor are three safety capacitors of equal capacitance.

[0033] Secondly, embodiments of this application provide a grid-side filtering device, which includes a grid-side filtering circuit and a motor as provided in any of the embodiments of this application above.

[0034] As described above, the grid-side filtering circuit and device provided in this application embodiment reduces the impedance between the three-phase grid power input terminal and the ground terminal by setting a first Y capacitor, a second Y capacitor, and a third Y capacitor between them, thereby reducing voltage division and effectively suppressing inverter leakage voltage problems. This grid-side filtering circuit and device of this application embodiment can significantly reduce inverter leakage voltage to a safe voltage range, effectively improving leakage voltage and leakage current during inverter operation, thus significantly enhancing equipment stability and operator safety. Attached Figure Description

[0035] To more clearly illustrate the technical solutions of the embodiments of this application, the accompanying drawings used in the embodiments of this application will be briefly introduced below. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0036] Figure 1 This is a schematic diagram of the structure of a power grid-side filter circuit in a related technology provided in an embodiment of this application;

[0037] Figure 2 This is a schematic diagram of the structure of a power grid-side filter circuit provided in an embodiment of this application;

[0038] Figure 3 This is a schematic diagram of the grid-side filter circuit provided in another embodiment of this application;

[0039] Figure 4 This is a schematic diagram of the structure of a power grid-side filter circuit provided in another embodiment of this application;

[0040] Figure 5 This is a schematic diagram of the structure of a power grid-side filter circuit provided in another embodiment of this application;

[0041] Figure 6 This is a schematic diagram of the structure of a power grid-side filter circuit provided in another embodiment of this application;

[0042] Figure 7 This is a schematic diagram of the structure of a power grid-side filter circuit provided in another embodiment of this application;

[0043] Figure 8 This is a schematic diagram of the structure of a power grid-side filter circuit provided in another embodiment of this application;

[0044] Figure 9 This is a schematic diagram of the structure of a power grid-side filtering device provided in an embodiment of this application. Detailed Implementation

[0045] The features and exemplary embodiments of various aspects of this application will be described in detail below. To make the objectives, technical solutions, and advantages of this application clearer, the application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only intended to explain this application and not to limit it. For those skilled in the art, this application can be implemented without some of these specific details. The following description of the embodiments is merely to provide a better understanding of this application by illustrating examples.

[0046] It should be noted that, in this document, relational terms such as "first" and "second" are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising..." does not exclude the presence of additional identical elements in the process, method, article, or apparatus that includes said element.

[0047] It should be noted that, unless otherwise specified, the embodiments and features described in this application can be combined with each other. The embodiments will now be described in detail with reference to the accompanying drawings.

[0048] As described in the background section, if the inverter has poor grounding during actual startup and operation, the inverter casing will become electrified, which can easily cause electric shock accidents such as electric shock and paralysis of construction personnel, posing a huge safety hazard to equipment and operators.

[0049] To address the aforementioned leakage problem, traditional solutions employ a combination of X and Y capacitors to suppress inverter leakage. Please refer to the following for details. Figure 1 , Figure 1 This is a schematic diagram of the grid-side filter circuit in an embodiment of the related technology provided in this application. For example... Figure 1 As shown, the current method uses a structure where a Y capacitor (Y4) is connected in series with three parallel X capacitors (X1, X2, X3) between the three-phase input terminal of the power grid and the ground terminal to divide the leakage current. The capacitance values ​​of the three X capacitors (X1, X2, X3) are typically 1μF (microfarads), and the capacitance value of the Y capacitor (Y4) is 220nF (nanofarads). In this structure, the intersection of the X and Y capacitors can be defined as a virtual N-point with a potential of 0V. Therefore, the leakage voltage of the frequency converter can be equivalent to... Figure 1 The magnitude of the voltage across the Y capacitor. However, in the above structure, the capacitance value of the Y capacitor to ground is relatively small, resulting in a large impedance. Under poor grounding conditions, the leakage voltage is large, which can easily lead to electric shock accidents. Therefore, the leakage problem of the frequency converter still cannot be well solved.

[0050] In view of the above, how to effectively suppress the leakage current problem in the aforementioned frequency converters, so as to fully improve the working stability of the grid-side filter device and the safety of operators, is an urgent problem to be solved in the industry.

[0051] To address the aforementioned technical problems, embodiments of this application provide a grid-side filtering circuit and apparatus. The grid-side filtering circuit provided in this application embodiment will be described first below.

[0052] Figure 2 This is a schematic diagram of the structure of a power grid-side filter circuit 100 provided in an embodiment of this application.

[0053] like Figure 2 As shown, this application embodiment provides a grid-side filter circuit 100, which includes a frequency converter 10, a first Y capacitor Y1, a second Y capacitor Y2 and a third Y capacitor Y3; the frequency converter 10 is electrically connected to the three-phase grid power input terminals (R, S, T) of the grid and electrically connected to the motor (U, V, W terminals) to form a main circuit.

[0054] The first terminal of the first Y capacitor Y1 is electrically connected to the first phase power input terminal of the three-phase power grid, and the second terminal of the first Y capacitor Y1 is electrically connected to the ground terminal GND.

[0055] The first terminal of the second Y capacitor Y2 is electrically connected to the second phase power input terminal of the three-phase power grid, and the second terminal of the second Y capacitor Y2 is electrically connected to the ground terminal GND.

[0056] The first terminal of the third Y capacitor Y3 is electrically connected to the third phase power input terminal of the three-phase power grid, and the second terminal of the third Y capacitor Y3 is electrically connected to the ground terminal GND.

[0057] As described above, the grid-side filter circuit 100 provided in this application embodiment reduces the impedance between the three-phase grid power input terminals R, S, T and the ground terminal GND by setting a first Y capacitor Y1, a second Y capacitor Y2 and a third Y capacitor Y3 between the three-phase grid power input terminals and the ground terminal GND. This reduces the voltage division and effectively suppresses the leakage voltage problem of the frequency converter 10. The grid-side filter circuit 100 of this application embodiment can significantly reduce the leakage voltage of the frequency converter 10 to a safe voltage range, thus effectively improving leakage voltage and leakage current problems, and significantly enhancing the operational stability of the equipment and the safety of operators.

[0058] Compared to the prior art provided above, the embodiments of this application remove the original Y capacitor and replace the original three X capacitors with Y capacitors, thereby increasing the Y capacitance value to ground between the three-phase power input terminal and the grounding terminal GND of the power grid, which can reduce leakage voltage division and help reduce the leakage voltage of the inverter casing that can be accessed by personnel when the inverter 10 is running under poor grounding conditions.

[0059] Please see below. Figure 3 , Figure 3 This is a schematic diagram of the structure of a power grid-side filter circuit 100 provided in another embodiment of this application. For example... Figure 3 As shown, according to some embodiments of this application, optionally, in order to further improve the operational safety and stability of the frequency converter 10, the grid-side filter circuit 100 may further include:

[0060] The switch protection module 20 has its first terminal electrically connected to the target node N and its second terminal electrically connected to the ground terminal GND.

[0061] The aforementioned switch protection module 20 is used to connect or disconnect the target node N and the ground terminal GND.

[0062] The target node N is the common connection point of the second pole of the first Y capacitor Y1, the second pole of the second Y capacitor Y2, and the second pole of the third Y capacitor Y3.

[0063] The aforementioned switch protection module 20 can be implemented using relays, contactors, or power switching devices. Power switching devices include semiconductor switching devices such as IGBTs (Insulated Gate Bipolar Transistors) and MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistors), and there are no strict limitations on them here.

[0064] In this embodiment, assuming good grounding, considering that the three-phase switches connected to the three-phase power input terminals of the grid are often difficult to close simultaneously at the moment the inverter 10 is powered on, resulting in a very short time difference, the current generated at the moment of power-on will flow back to the grid through the common-mode loop from the Y capacitor to ground. At this time, the vector sum of the currents in the three-phase differential-mode loop is not zero, which can easily lead to tripping. The tripping probability is related to the size of the Y capacitor; the larger the Y capacitor and the larger the power-on current, the easier it is to trip.

[0065] Based on this, in order to effectively avoid the problem of power-on tripping, this embodiment of the application adds the above-mentioned switch protection module 20 at the target node N, which can determine the timing of the first Y capacitor Y1, the second Y capacitor Y2 and the third Y capacitor Y3 being connected to the circuit, thus helping to maintain the stable and reliable operation of the system.

[0066] For example, by keeping the switch protection module 20 disconnected before the three phases of the power grid are energized and stabilized, the connection between the target node N and the grounding terminal GND in the circuit is broken, thereby effectively solving the problem of tripping when the grounding is good.

[0067] Accordingly, by turning on the switch protection module 20 after the three phases of the power grid are stabilized, the target node N in the circuit is connected to the ground terminal GND, thereby effectively using the first Y capacitor Y1, the second Y capacitor Y2 and the third Y capacitor Y3 to suppress leakage current in the frequency converter 10.

[0068] Please see below. Figure 4 , Figure 4 This is a schematic diagram of the structure of a power grid-side filter circuit 100 provided in another embodiment of this application. For example... Figure 4 As shown, according to some embodiments of this application, optionally, in order to more reasonably realize the on / off control of the above-mentioned switch protection module 20, the grid-side filter circuit 100 may further include:

[0069] The power-on detection module 30 has its first signal input terminal IN+ electrically connected to the positive terminal of the DC bus in the inverter 10, its second signal input terminal IN- electrically connected to the negative terminal of the DC bus in the inverter 10, and its signal output terminal OUT electrically connected to the switch protection module 20.

[0070] The power-on detection module 30 is used to determine whether the inverter 10 has completed power-on by collecting voltage signals from the first signal input terminal IN+ and the second signal input terminal IN-. Furthermore, if the inverter 10 is determined to be powered on successfully, a conduction signal is sent to the switch protection module 20 through the signal output terminal OUT, so that the switch protection module 20 connects the target node N and the ground terminal GND.

[0071] If it is determined that the inverter 10 has not been powered on, a shutdown signal is sent to the switch protection module 20 through the signal output terminal OUT, so that the switch protection module 20 disconnects the target node N and the ground terminal GND.

[0072] In specific implementation, by setting up the aforementioned power-on detection module 30, this module collects the voltage difference between the positive and negative terminals of the DC bus of the inverter 10, thereby effectively determining whether the inverter 10 is currently powered on or whether its power-on is stable based on the magnitude of the voltage difference. For example, a voltage threshold can be preset, and by comparing the voltage values ​​across the positive and negative terminals of the DC bus with the voltage threshold, an accurate determination can be made as to whether the inverter 10 is currently powered on or whether its power-on is stable.

[0073] In this way, when the power-on detection module 30 determines that the inverter 10 has been powered on, it sends a conduction signal to the switch protection module 20 through the signal output terminal OUT, so that the switch protection module 20 connects the target node N and the ground terminal GND, thereby effectively using the first Y capacitor Y1, the second Y capacitor Y2 and the third Y capacitor Y3 to suppress leakage current in the inverter 10.

[0074] If the power-on detection module 30 determines that the inverter 10 has not completed power-on, it sends a shutdown signal to the switch protection module 20 through the signal output terminal OUT, so that the switch protection module 20 disconnects the target node N and the ground terminal GND, thereby effectively solving the problem of power-on tripping under good grounding conditions.

[0075] In this embodiment, by setting the power-on detection module 30, the switch protection module 20 in the circuit can be effectively turned on or off, thereby significantly improving the overall operational safety and stability.

[0076] It should be noted that the power-on detection module 30 mentioned above in this application can be implemented directly using an MCU (Microcontroller Unit) chip, or it can be implemented based on some detection circuit structure and voltage measurement equipment, etc., which will not be described in detail here.

[0077] Please see below. Figure 5 , Figure 5 This is a schematic diagram of the structure of a power grid-side filter circuit 100 provided in another embodiment of this application. For example... Figure 5 As shown, according to some embodiments of this application, optionally, considering that electrical signal interference is often unavoidable in the circuit, a large interference signal may cause the aforementioned switch protection module 20 to malfunction. Therefore, to avoid the interference signal adversely affecting the on / off control of the switch protection module 20, the grid-side filter circuit 100 may further include a filter protection module 40.

[0078] In one possible embodiment, the switch protection module 20 can be a relay or a contactor, and the switch protection module 20 can include a main contact pair for implementing the switching function and an auxiliary contact pair for control; the signal output terminal OUT of the power-on detection module 30 can include a first signal output terminal OUT1 and a second signal output terminal OUT2.

[0079] The first sub-contact K1 in the main contact pair is electrically connected to the target node N, and the second sub-contact K2 in the main contact pair is electrically connected to the ground terminal GND.

[0080] The third sub-contact K3 in the auxiliary contact pair is electrically connected to the first signal output terminal OUT1, and the fourth sub-contact K4 in the auxiliary contact pair is electrically connected to the second signal output terminal OUT2.

[0081] The first end of the filter protection module 40 is electrically connected to the third sub-contact K3, and the second end of the filter protection module 40 is electrically connected to the fourth sub-contact K4.

[0082] In specific implementation, depending on the different implementation scenarios of the switch protection module 20, when the switch protection module 20 is a relay or contactor, the first sub-contact K1 and the second sub-contact K2 in the above main contact pair work together to realize the switching function.

[0083] The power-on detection module 30 provides corresponding control signals to the third sub-contact K3 and the fourth sub-contact K4 in the switch protection module 20 through the first signal output terminal OUT1 and the second signal output terminal OUT2. The third sub-contact K3 and the fourth sub-contact K4 respond according to the different signals received, thereby controlling whether the first sub-contact K1 and the second sub-contact K2 are connected.

[0084] In this scenario, whether the switch protection module 20 connects the target node N and the ground terminal GND is actually determined by the signals received by the third sub-contact K3 and the fourth sub-contact K4. When the third sub-contact K3 and the fourth sub-contact K4 come into contact with some transient electromagnetic interference signals, the switch protection module 20 may send a false turn-on or false turn-off signal.

[0085] Therefore, in this embodiment, a filtering protection module 40 is provided between the third sub-contact K3 and the fourth sub-contact K4. This filtering protection module 40 can filter out interference noise that appears in a short period of time, which helps to maintain the reliable operation of the switch protection module 20 and thus fully improves the safety and stability of the overall system operation.

[0086] Please see below. Figure 6 , Figure 6 This is a schematic diagram of the structure of a power grid-side filter circuit 100 provided in another embodiment of this application. For example... Figure 6As shown, according to some embodiments of this application, optionally, for reasons similar to those in the foregoing embodiments, considering that electrical signal interference is often unavoidable in the circuit, a large interference signal may cause the switch protection module 20 to malfunction.

[0087] Therefore, in order to avoid interference signals from adversely affecting the on / off control of the switch protection module 20, the grid-side filter circuit 100 may also include a filter protection module 40.

[0088] In one possible embodiment, the switch protection module 20 is a power switch device; the switch protection module 20 may also include a control terminal, which is electrically connected to the signal output terminal OUT of the power-on detection module 30.

[0089] The first terminal of the filter protection module 40 is electrically connected to the control terminal, and the second terminal of the filter protection module 40 is electrically connected to the ground terminal GND.

[0090] In specific implementations, depending on the different implementation scenarios of the switch protection module 20, when the switch protection module 20 is a power switching device (e.g., IGBT), this switch protection module 20 includes a first terminal, a second terminal, and a control terminal. The first terminal of the switch protection module 20 is electrically connected to the target node N, the second terminal of the switch protection module 20 is electrically connected to the ground terminal GND, and the control terminal of the switch protection module 20 is electrically connected to the signal output terminal OUT of the power-on detection module 30. The switch protection module 20 performs on / off operations based on the signal received from the power-on detection module 30, which is either a conduction signal or a turn-off signal.

[0091] In other words, in this scenario, whether the switch protection module 20 connects the target node N and the ground terminal GND is actually determined by the signal received by the control terminal of the switch protection module 20. When the control terminal of the switch protection module 20 receives some transient electromagnetic interference signals, the switch protection module 20 may send a false turn-on or false turn-off signal.

[0092] Therefore, in this embodiment, a filter protection module 40 is set between the control terminal and the ground terminal GND of the switch protection module 20. This filter protection module 40 can filter out interference noise that appears in a short period of time, which helps to maintain the reliable operation of the switch protection module 20 and thus fully improves the safety and stability of the overall system operation.

[0093] To further ensure that the filtering and protection module 40 can fully perform its filtering function against interference signals, optionally, as follows: Figure 7 As shown, the aforementioned filter protection module 40 can specifically be a filter capacitor Cf.

[0094] Please see below. Figure 8 , Figure 8 This is a schematic diagram of the structure of a power grid-side filter circuit 100 provided in another embodiment of this application. For example... Figure 8 As shown, according to some embodiments of this application, the frequency converter 10 may optionally include a three-phase rectifier bridge and a three-phase inverter bridge. The output terminals of the three-phase rectifier bridge and the input terminals of the three-phase inverter bridge are electrically connected via a DC bus.

[0095] The input terminals of the three-phase rectifier bridge are electrically connected to the three-phase power input terminals of the power grid, and the output terminals of the three-phase inverter bridge are connected to the motor.

[0096] A three-phase rectifier bridge consists of six diodes and is used to convert the three-phase AC voltage input from the power grid into DC voltage.

[0097] The three-phase inverter bridge consists of six power switching devices used to convert DC voltage into three-phase AC voltage and output three-phase AC voltage to the motor.

[0098] The aforementioned three-phase rectifier bridge includes a first diode D1, a second diode D2, a third diode D3, a fourth diode D4, a fifth diode D5, and a sixth diode D6.

[0099] In actual operation, the six diodes in the three-phase rectifier bridge are divided into two groups of three diodes each. One group is used for the positive half-cycle, and the other group is used for the rectification of the negative half-cycle, so as to produce a smoother DC output.

[0100] The aforementioned three-phase inverter bridge includes a first power switch Q1, a second power switch Q2, a third power switch Q3, a fourth power switch Q4, a fifth power switch Q5, and a sixth power switch Q6. These power switches can be, for example, thyristors (SCRs), insulated-gate bipolar transistors (IGBTs), or metal-oxide-semiconductor field-effect transistors (MOSFETs), depending on the actual production requirements.

[0101] In actual operation, the three-phase inverter bridge receives DC voltage from the three-phase rectifier and converts it into three-phase AC voltage by turning on or off the corresponding power switching transistors among the six power switching transistors. The amplitude and frequency of the AC voltage can be adjusted as needed.

[0102] More specifically, the inverter 10 may also include a first bus capacitor C1 and a second bus capacitor C2.

[0103] The first terminal of the first bus capacitor C1 is electrically connected to the positive terminal of the DC bus, the second terminal of the first bus capacitor C1 is electrically connected to the first terminal of the second bus capacitor C2, and the second terminal of the second bus capacitor C2 is electrically connected to the negative terminal of the DC bus.

[0104] The first bus capacitor C1 and the second bus capacitor C2 mentioned above can be used to filter and stabilize the DC voltage output by the three-phase rectifier bridge, thereby effectively reducing or even eliminating the ripple in the rectified DC voltage and making it smoother.

[0105] According to some embodiments of this application, optionally, in order to more fully maintain the reliability and safety of system operation, the first Y capacitor Y1, the second Y capacitor Y2, and the third Y capacitor Y3 are three safety capacitors with equal capacitance.

[0106] For example, the capacitance values ​​of the first Y capacitor Y1, the second Y capacitor Y2, and the third Y capacitor Y3 are, for example, 1 μF, and are not strictly limited here.

[0107] Optionally, considering the leakage protection requirements in actual power scenarios, in order to effectively address leakage voltage phenomena, the capacitance values ​​of the first Y capacitor Y1, the second Y capacitor Y2, and the third Y capacitor Y3 in this embodiment are at least greater than 0.68μF.

[0108] For example, taking a leakage voltage of less than 5V as an example, the capacitance values ​​of the first Y capacitor Y1, the second Y capacitor Y2, and the third Y capacitor Y3 mentioned above should be at least greater than 680nF, so as to improve the leakage voltage and leakage current.

[0109] In this embodiment, the first Y capacitor Y1, the second Y capacitor Y2, and the third Y capacitor Y3, all with a capacitance value of 1μF, are used. The measured leakage voltage is 3.7V, which can effectively solve the problem of equipment leakage causing a tingling sensation when the equipment is running under poor grounding conditions.

[0110] The existing technology measures a leakage voltage of 38V in the casing of the inverter under poor grounding conditions. Compared with the existing technology, the embodiment of this application effectively reduces the leakage voltage of the controller casing under poor grounding conditions by removing the original 220nF Y capacitor (Y4) and replacing the original three 1μF X capacitors (X1, X2, X3) with three 1μF Y capacitors (Y1, Y2, Y3).

[0111] Additionally, please refer to [link / reference needed]. Figure 9 As shown, a distributed capacitance is formed between the motor windings and the motor housing. This distributed capacitance often has a significant impact on the performance of the motor, and its magnitude is closely related to the leakage current.

[0112] Specifically, during the actual startup and operation of the frequency converter, the three-phase inverter inside the frequency converter generates leakage voltage and thus leakage current. This leakage current is transmitted to the motor and then through... Figure 9The distributed capacitance between the motor windings and the motor housing is transmitted to the motor housing and finally returns to the frequency converter (usually the housing part corresponding to the frequency converter) through the shielding layer. Therefore, the magnitude of leakage current or leakage voltage is often related to the distributed capacitance.

[0113] Therefore, in order to more effectively solve the problem of equipment leakage and tingling sensation during operation under poor grounding conditions, based on the first Y capacitor Y1, the second Y capacitor Y2, and the third Y capacitor Y3, the actual distributed capacitance of the motor can be considered when selecting the actual capacitance value of the Y capacitors for a more reasonable capacitance value configuration.

[0114] It is understood that the above are all examples and do not serve as a substantial limitation on the power grid-side filter circuit 100 protected by this application.

[0115] Overall, this application provides a grid-side filter circuit 100. By setting a first Y capacitor Y1, a second Y capacitor Y2, and a third Y capacitor Y3 between the three-phase grid power input terminal and the ground terminal GND, the impedance between the three-phase grid power input terminal and the ground terminal GND is reduced, thereby reducing the voltage division and significantly reducing the leakage voltage of the inverter 10 to a safe voltage range. This effectively improves the leakage problem and significantly enhances the stability of equipment operation and the safety of operators.

[0116] Furthermore, this embodiment considers that when the inverter 10 is powered on under good grounding conditions, it is often difficult for the three-phase switches connected to the three-phase power input terminals of the grid to close simultaneously. At this time, the vector sum of the three-phase differential mode circuit currents is not zero, which can easily lead to tripping. Therefore, in order to effectively avoid the problem of power-on tripping, this embodiment adds the aforementioned switch protection module 20 and the corresponding power-on detection module 30, etc., so that the first Y capacitor Y1, the second Y capacitor Y2, and the third Y capacitor Y3 are connected to the circuit after the inverter 10 is stably powered on. This can effectively solve the problem of power-on tripping under good grounding conditions and help maintain stable and reliable operation of the equipment.

[0117] Based on the grid-side filter circuit 100 provided in the above embodiments, correspondingly, this application provides a grid-side filter device 1000, which will be described below. Figure 9 , Figure 9 This is a schematic diagram of the structure of a power grid-side filter device 1000 provided in one embodiment of this application. For example... Figure 9 As shown, the grid-side filter device 1000 includes a grid-side filter circuit 100 and a motor 200 as provided in any of the embodiments of this application described above.

[0118] Specifically, the grid-side filter device 1000 may include more than one grid-side filter circuit 100 as provided in the aforementioned embodiments; the motor 200 may specifically be an AC motor. The grid-side filter device 1000 provided in this application embodiment has the beneficial effects of the grid-side filter circuit 100 provided in this application embodiment. For details, please refer to the specific descriptions of the grid-side filter circuit 100 in the above embodiments, which will not be repeated here.

[0119] The functional blocks shown in the above-described structural diagram can be implemented as hardware, software, firmware, or a combination thereof. When implemented in hardware, they can be, for example, electronic circuits, application-specific integrated circuits (ASICs), appropriate firmware, plug-ins, function cards, etc. When implemented in software, the elements of this application are programs or code segments used to perform the required tasks. Programs or code segments can be stored on a machine-readable medium or transmitted over a transmission medium or communication link via data signals carried on a carrier wave. "Machine-readable medium" can include any medium capable of storing or transmitting information. Examples of machine-readable media include electronic circuits, semiconductor memory devices, ROM, flash memory, erasable ROM (EROM), floppy disks, CD-ROMs, optical disks, hard disks, fiber optic media, radio frequency (RF) links, etc. Code segments can be downloaded via computer networks such as the Internet, intranets, etc.

[0120] It should be noted that, in this document, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0121] It should be clarified that the various embodiments in this specification are described in a progressive manner. Similar or identical parts between embodiments can be referred to interchangeably. Each embodiment focuses on describing the differences from other embodiments. According to the embodiments described above, these embodiments do not exhaustively describe all details, nor do they limit this application to only the specific embodiments described. Obviously, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of this application, thereby enabling those skilled in the art to make good use of this application and modifications based on it. This application is limited only by the claims and their full scope and equivalents.

[0122] This document uses specific examples to illustrate the principles and implementation methods of this application. The examples are merely for the purpose of helping to understand the method and core ideas of this application. The above are only preferred embodiments of this application. It should be noted that due to the limitations of written expression, and the existence of an infinite number of specific structures, those skilled in the art can make several improvements, modifications, or changes without departing from the principles of this application, and can also combine the above technical features in an appropriate manner. These improvements, modifications, changes, or combinations, or the direct application of the concept and technical solution of this application to other situations without modification, should all be considered within the scope of protection of this application.

Claims

1. A power grid-side filter circuit, characterized in that, The circuit includes a frequency converter, a first Y capacitor, a second Y capacitor, and a third Y capacitor; the frequency converter is electrically connected to the three-phase power input terminal of the power grid and to the motor to form a main circuit. The first terminal of the first Y capacitor is electrically connected to the first phase power input terminal of the three-phase power grid, and the second terminal of the first Y capacitor is electrically connected to the ground terminal. The first terminal of the second Y capacitor is electrically connected to the second phase power input terminal of the three-phase power grid, and the second terminal of the second Y capacitor is electrically connected to the ground terminal. The first terminal of the third Y capacitor is electrically connected to the third phase power input terminal of the three-phase power grid, and the second terminal of the third Y capacitor is electrically connected to the ground terminal.

2. The circuit according to claim 1, characterized in that, The circuit also includes: A switch protection module, wherein a first terminal of the switch protection module is electrically connected to the target node, and a second terminal of the switch protection module is electrically connected to the grounding terminal; The switch protection module is used to connect or disconnect the target node and the grounding terminal; The target node is the common connection point of the second pole of the first Y capacitor, the second pole of the second Y capacitor, and the second pole of the third Y capacitor.

3. The circuit according to claim 2, characterized in that, The circuit also includes: The power-on detection module has a first signal input terminal electrically connected to the positive terminal of the DC bus in the frequency converter, a second signal input terminal electrically connected to the negative terminal of the DC bus in the frequency converter, and a signal output terminal electrically connected to the switch protection module. The power-on detection module is used to determine whether the inverter has completed power-on by collecting voltage signals from the first signal input terminal and the second signal input terminal; and, if it is determined that the inverter has completed power-on, it sends a conduction signal to the switch protection module through the signal output terminal so that the switch protection module connects the target node and the ground terminal. If it is determined that the inverter has not completed power-on, a shutdown signal is sent to the switch protection module through the signal output terminal so that the switch protection module disconnects the target node and the ground terminal.

4. The circuit according to claim 3, characterized in that, The circuit also includes a filtering and protection module; the switch protection module is a relay or a contactor, and the switch protection module includes a main contact pair for implementing the switching function and an auxiliary contact pair for control; the signal output terminal of the power-on detection module includes a first signal output terminal and a second signal output terminal; The first sub-contact of the main contact pair is electrically connected to the target node, and the second sub-contact of the main contact pair is electrically connected to the grounding terminal. The third sub-contact in the auxiliary contact pair is electrically connected to the first signal output terminal, and the fourth sub-contact in the auxiliary contact pair is electrically connected to the second signal output terminal. The first end of the filter protection module is electrically connected to the third sub-contact, and the second end of the filter protection module is electrically connected to the fourth sub-contact.

5. The circuit according to claim 3, characterized in that, The circuit also includes a filter protection module; the switch protection module is a power switch device; the switch protection module also includes a control terminal, which is electrically connected to the signal output terminal of the power-on detection module. The first end of the filter protection module is electrically connected to the control terminal, and the second end of the filter protection module is electrically connected to the grounding terminal.

6. The circuit according to claim 4 or 5, characterized in that, The filtering protection module is a filter capacitor.

7. The circuit according to claim 1, characterized in that, The frequency converter includes a three-phase rectifier bridge and a three-phase inverter bridge; the output terminals of the three-phase rectifier bridge and the input terminals of the three-phase inverter bridge are electrically connected through a DC bus. The input terminal of the three-phase rectifier bridge is electrically connected to the three-phase power input terminal of the power grid, and the output terminal of the three-phase inverter bridge is connected to the motor. The three-phase rectifier bridge consists of six diodes and is used to convert the three-phase AC voltage input from the power grid into DC voltage. The three-phase inverter bridge consists of six power switching transistors, which are used to convert the DC voltage into a three-phase AC voltage and output the three-phase AC voltage to the motor.

8. The circuit according to claim 7, characterized in that, The frequency converter also includes a first bus capacitor and a second bus capacitor. The first terminal of the first bus capacitor is electrically connected to the positive terminal of the DC bus, and the second terminal of the first bus capacitor is electrically connected to the first terminal of the second bus capacitor. The second terminal of the second bus capacitor is electrically connected to the negative terminal of the DC bus. The first bus capacitor and the second bus capacitor are used to filter and regulate the DC voltage output by the three-phase rectifier bridge.

9. The circuit according to claim 1, characterized in that, The first Y capacitor, the second Y capacitor, and the third Y capacitor are three safety capacitors with equal capacitance.

10. The circuit according to claim 1, characterized in that, The capacitance values ​​of the first Y capacitor, the second Y capacitor, and the third Y capacitor are at least greater than 0.68 μF.

11. A power grid-side filtering device, characterized in that, The grid-side filtering device includes a grid-side filtering circuit and a motor as described in any one of claims 1-10.

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