Frequency converter system

Abstract

The utility model provides a frequency converter system, comprising a first frequency converter with an input end connected with a first transformer and an output end connected with a motor; the input end of the second frequency converter is connected with the second transformer; the first current acquisition module is connected with the input end of the first transformer and can acquire the input current of the first transformer; the second current acquisition module is connected with the second transformer and can acquire the input current of the second transformer; one end of the switch is connected with the first current acquisition module and the second current acquisition module and the other end is connected with a power grid; and the protection module is connected with the first current acquisition module, the second current acquisition module and the switch, and can control the on-off of the switch according to the input current of the first transformer and the input current of the second transformer. According to the frequency converter system, when the output currents of the two frequency converters are unbalanced, the frequency converter system can be timely and effectively cut off from a power grid, so that the damage of devices is avoided, and the safety, stability and reliability of the frequency converter system are guaranteed.

Description

TECHNICAL FIELD

[0001] The utility model relates to frequency converter technical field especially relates to a frequency converter system. BACKGROUND

[0002] With the stable maturity of high voltage frequency converter technology, its application field is also continuously widened, and is widely used in various fan, water pump, compressor, rolling mill and the like of large mining production plant, petroleum chemical industry, municipal water supply, metallurgical steel, electric power energy and the like, to save energy and improve the process.

[0003] In some scenarios, the frequency converter needs to be used for super large power load such as compressor and the like working condition.When dragging super large power load, due to the current limitation of power device of single frequency converter, some existing schemes adopt two frequency converters in parallel to output super large current.When two frequency converters are connected in parallel, there may be output current imbalance, which is easy to cause device damage, and is not conducive to the safe, stable and reliable operation of the frequency converter system.Therefore, how to guarantee the safety, stability and reliability of the frequency converter system when the output current of the two frequency converter parallel connection circuit is unbalanced is a technical problem to be solved by the utility model.

[0004] The content of the background section merely represents the best of the inventor's knowledge and is not necessarily indicative of the state of the art in the field. CONTENT OF THE UTILITY MODEL

[0005] In view of one or more of the problems existing in the prior art, the utility model provides a frequency converter system, which comprises: a first frequency converter, an input end of which is connected with a first transformer, and an output end of which is connectable with a motor; a second frequency converter, an input end of which is connected with a second transformer, and an output end of which is connectable with the motor; a first current acquisition module, which is connected with the input end of the first transformer and can acquire the input current of the first transformer; a second current acquisition module, which is connected with the second transformer and can acquire the input current of the second transformer; a switch, one end of which is connected with the first current acquisition module and the second current acquisition module, and the other end of which is connected with a power grid; and a protection module, which is connected with the first current acquisition module, the second current acquisition module and the switch, and can control the on-off of the switch according to the input current of the first transformer and the input current of the second transformer.

[0006] Optionally, the first current acquisition module comprises a plurality of first sub-modules, the plurality of first sub-modules are connected with three-phase input ends of the first transformer respectively, and can acquire currents of the three-phase input ends of the first transformer respectively.

[0007] Optionally, the second current acquisition module comprises a plurality of second sub-modules, the plurality of second sub-modules are connected with three-phase input ends of the second transformer respectively, and can acquire currents of the three-phase input ends of the second transformer respectively.

[0008] Optionally, the protection module is connected to the first and second sub-modules, and controls the on-off of the switch according to the currents of the corresponding input terminals of the first and second transformers collected by the first and second sub-modules respectively.

[0009] Optionally, when the difference between the currents of the corresponding input terminals is greater than or equal to a threshold value, the protection module controls the switch to be turned off; and when the difference between the currents of the corresponding input terminals is less than the threshold value, the protection module controls the switch to be kept on or not to be operated.

[0010] Optionally, the protection module can determine the positive and / or negative sequence components of the currents of the corresponding input terminals, and when the difference between the positive and / or negative sequence components of the currents of the corresponding input terminals is greater than or equal to a threshold value, the protection module controls the switch to be turned off; and when the difference between the positive and / or negative sequence components of the currents of the corresponding input terminals is less than the threshold value, the protection module controls the switch to be kept on or not to be operated.

[0011] Optionally, the protection module comprises a subtractor and a comparator, the subtractor is connected to the first and second current collection modules and can determine the difference between the currents of the corresponding input terminals of the first and second transformers, and the comparator is connected to the subtractor and the switch and can control the on-off of the switch according to the difference between the currents of the corresponding input terminals.

[0012] Optionally, the first and second sub-modules comprise current transformers, and the switch comprises a circuit breaker.

[0013] Optionally, the frequency converter system further comprises a first and a second reactor, the first reactor is connected to the output terminal of the first frequency converter, the second reactor is connected to the output terminal of the second frequency converter, and the first and second reactors can be connected to the motor.

[0014] The frequency converter system of the utility model can realize large-current output through the parallel connection of two frequency converters, and meet the use scene of large power. When the output currents of the two frequency converters are unbalanced, the frequency converter system and the power grid can be effectively cut off in time, the safety, stability and reliability of the frequency converter system are ensured, and the damage of the device is avoided. The reactors arranged at the output terminals of the two frequency converters can suppress the circulating current caused by the output voltage difference of the two frequency converters, thereby improving the safety, stability and reliability of the entire frequency converter system. BRIEF DESCRIPTION OF DRAWINGS

[0015] The accompanying drawings are used to provide further understanding of the present application, and constitute a part of the specification, and are used to explain the present application together with embodiments of the present application, and do not constitute a limitation to the present application. In the drawings:

[0016] Figure 1 A schematic view of a frequency converter system according to some embodiments of the present application is shown.

[0017] Figure 2 A partial schematic view of a frequency converter system according to some embodiments of the present application is shown.

[0018] Figure 3 A partial schematic view of a frequency converter system according to some embodiments of the present application is shown.

[0019] Figure 4 A schematic view of a frequency converter system according to some embodiments of the present application is shown. DETAILED DESCRIPTION

[0020] In the following, only certain exemplary embodiments are simply described. As those skilled in the art can recognize, the described embodiments can be modified in various different ways without departing from the spirit or scope of the present application. Therefore, the drawings and the description are considered to be essentially exemplary rather than limiting.

[0021] In the description of the present application, it is to be understood that the terms "center", "longitudinal", "transverse", "length", "width", "thickness", "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", "clockwise", "counterclockwise", and the like indicate the orientation or positional relationship based on the orientation or positional relationship shown in the drawings, and are only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as indicating or implying that the indicated device or element must have a particular orientation, be constructed and operated in a particular orientation, and therefore cannot be understood as a limitation to the present application. In addition, the terms "first", "second" are only for the purpose of description, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the present application, the meaning of "multiple" is two or more, unless otherwise specifically limited.

[0022] In the description of the utility model, it needs to explain, unless another explicit provision and limitation, the term "installation", "link", "connection", "coupling" should do the broad sense understanding, for example, can be fixed connection, also can be detachable connection, or integrally connected;Can be mechanical connection, also can be electrical connection or can communicate with each other;It can be directly connected, also can be indirectly connected through intermediate medium, can be the communication of two elements or the interaction relationship of two elements.For ordinary skilled in the art, the above-mentioned terms can be understood according to the specific meaning of the utility model.

[0023] In the utility model, unless another explicit provision and limitation, the first feature is "on" or "under" the second feature can include the direct contact of the first and second features, also can include that the first and second features are not in direct contact but contact through another feature between them.Moreover, the first feature is "on", "above" and "on" the second feature includes that the first feature is directly above and obliquely above the second feature, or only indicates that the horizontal height of the first feature is higher than the second feature.The first feature is "under", "below" and "under" the second feature includes that the first feature is directly below and obliquely below the second feature, or only indicates that the horizontal height of the first feature is less than the second feature.

[0024] Many different embodiments or examples are provided below to realize the different structures of the utility model.For the purpose of simplifying the utility model, the components and settings of specific examples are described below.Of course, they are only examples, and the purpose is not to limit the utility model.In addition, the utility model can repeatedly refer to numbers and / or reference letters in different examples, and such repetition is for the purpose of simplification and clarity, which itself does not indicate the relationship between the various embodiments and / or settings discussed.In addition, the utility model provides various specific examples of processes and materials, but those skilled in the art can realize the application of other processes and / or the use of other materials.

[0025] The preferred embodiments of the utility model are described below in conjunction with the drawings, and it should be understood that the preferred embodiments described herein are only used to illustrate and explain the utility model, and are not used to limit the utility model.

[0026] The utility model provides a kind of frequency converter system. Figure 1 The schematic diagram of frequency converter system 10 according to some embodiments of the utility model is shown.As shown in FIG. Figure 1As shown, the frequency converter system 10 comprises a first frequency converter VF1, a second frequency converter VF2, a first transformer T1, a second transformer T2, a first current acquisition module CT1, a second current acquisition module CT2, a switch K and a protection module P. The input end of the first frequency converter VF1 is connected with the first transformer T1. The output end of the first frequency converter VF1 is connectable with a motor M. The input end of the second frequency converter VF2 is connected with the second transformer T2. The output end of the second frequency converter VF2 is connectable with the motor M. The first current acquisition module CT1 is connected with the input end of the first transformer T1 and can acquire the input current of the first transformer T1. The second current acquisition module CT2 is connected with the second transformer T2 and can acquire the input current of the second transformer T2. One end of the switch K is connected with the first current acquisition module CT1 and the second current acquisition module CT2, and the other end of the switch K is connected with a power grid E. The protection module P is connected with the first current acquisition module CT1, the second current acquisition module CT2 and the switch K, and can control the on-off of the switch K according to the input current of the first transformer T1 and the input current of the second transformer T2. The frequency converter system of the utility model can cut off the power grid through the control of the switch when the output currents of the two frequency converters are unbalanced, so as to avoid the damage of the device and improve the safety, stability and reliability of the frequency converter system.

[0027] In some embodiments, the first current acquisition module comprises a plurality of first sub-modules, which are respectively connected with three-phase input ends of the first transformer and can respectively acquire currents of the three-phase input ends of the first transformer. Figure 2 A partial schematic view of a frequency converter system 10 according to some embodiments of the utility model is shown. As shown in FIG. 1, the frequency converter system 10 comprises a first frequency converter VF1, a second frequency converter VF2, a first transformer T1, a second transformer T2, a first current acquisition module CT1, a second current acquisition module CT2, a switch K and a protection module P. Figure 2 As shown, the first current acquisition module CT1 comprises first sub-modules CT11, CT12 and CT13. The first sub-modules CT11, CT12 and CT13 are respectively connected with three-phase input ends u1, v1 and w1 of the first transformer T1 and can respectively acquire currents i11, i12 and i13 of the three-phase input ends u1, v1 and w1 of the first transformer T1. That is, the first sub-module CT11 can acquire the current i11 of the input end u1. The first sub-module CT12 can acquire the current i12 of the input end v1. The first sub-module CT13 can acquire the current i13 of the input end w1.

[0028] In some embodiments, the second current acquisition module comprises a plurality of second sub-modules, which are respectively connected with three-phase input ends of the second transformer and can respectively acquire currents of the three-phase input ends of the second transformer. As shown in FIG. 2, the second current acquisition module CT2 comprises second sub-modules CT21, CT22 and CT23. Figure 2As shown, the second current collection module CT2 includes second sub-modules CT21, CT22, and CT23. The second sub-modules CT21, CT22, and CT23 are respectively connected to the three-phase input terminals u2, v2, and w2 of the second transformer T2, and can respectively collect the currents i21, i22, and i23 of the three-phase input terminals u2, v2, and w2 of the second transformer T2. The second sub-module CT21 can collect the current i21 of the input terminal u2. The second sub-module CT22 can collect the current i22 of the input terminal v2. The second sub-module CT23 can collect the current i23 of the input terminal w2.

[0029] In some embodiments, the protection module is connected to the plurality of first sub-modules and the plurality of second sub-modules, and can control the on-off of the switch according to the currents of the corresponding input terminals of the first transformer and the second transformer collected by the first sub-modules and the second sub-modules respectively. For example, the protection module P can control the on-off of the switch K according to the current i11 of the input terminal u1 collected by the first sub-module CT11 and the current i21 of the input terminal u2 collected by the second sub-module CT21. Figure 2 As shown, the protection module P is connected to the first sub-modules CT11, CT12, and CT13 and the second sub-modules CT21, CT22, and CT23. The input terminals u1 and u2 are corresponding input terminals. The input terminals v1 and v2 are corresponding input terminals. The input terminals w1 and w2 are corresponding input terminals. For example, the protection module P can control the on-off of the switch K according to the current i11 of the input terminal u1 collected by the first sub-module CT11 and the current i21 of the input terminal u2 collected by the second sub-module CT21. For another example, the protection module P can control the on-off of the switch K according to the current i12 of the input terminal v1 collected by the first sub-module CT12 and the current i22 of the input terminal v2 collected by the second sub-module CT22. For another example, the protection module P can control the on-off of the switch K according to the current i13 of the input terminal w1 collected by the first sub-module CT13 and the current i23 of the input terminal w2 collected by the second sub-module CT23. The protection module P can control the on-off of the switch according to the current of any corresponding input terminal (the currents i11, i21, or i12, i22, or i13, i23). Alternatively, the protection module can control the on-off of the switch according to the currents of the three input terminals (the currents i11, i21, i12, i22, i13, and i23).

[0030] In some embodiments, when the difference between the currents of the corresponding input terminals of the first transformer and the second transformer respectively acquired by the first sub-module and the second sub-module is greater than or equal to a threshold value, the protection module can control the switch to be turned off. Conversely, when the difference between the currents of the corresponding input terminals of the first transformer and the second transformer respectively acquired by the first sub-module and the second sub-module is less than the threshold value, the protection module controls the switch to be maintained in conduction or not to be operated. For example, the protection module P can compare the current i11 of the input terminal u1 with the current i21 of the input terminal u2, and when the difference between the two is greater than or equal to the threshold value TH, the protection module P controls the switch K to be turned off. When the difference between the two is less than the threshold value TH, the protection module P can control the switch K to be maintained in conduction or not to be operated. For another example, the protection module P can compare the current i12 of the input terminal v1 with the current i22 of the input terminal v2, and when the difference between the two is greater than or equal to the threshold value TH, the protection module P controls the switch K to be turned off. When the difference between the two is less than the threshold value TH, the protection module P can control the switch K to be maintained in conduction or not to be operated. For yet another example, the protection module P can compare the current i13 of the input terminal w1 with the current i23 of the input terminal w2, and when the difference between the two is greater than or equal to the threshold value TH, the protection module P controls the switch K to be turned off. When the difference between the two is less than the threshold value TH, the protection module P can control the switch K to be maintained in conduction or not to be operated. The frequency converter system of the utility model, when the difference between the currents of any corresponding input terminals of the first transformer and the second transformer is greater than or equal to the threshold value, the protection module can control the on-off of the switch, so as to cut off the power grid E in time and effectively, thereby protecting the safety of the device and improving the safety, stability and reliability of the frequency converter system.

[0031] In some embodiments, the protection module P can compare the difference between the currents i11 and i21, the difference between the currents i12 and i22, and the difference between the currents i13 and i23 respectively, and when any of the differences is greater than or equal to the threshold value TH, the protection module P controls the switch K to be turned off. When all the three differences are less than the threshold value TH, the protection module P controls the switch K to be maintained in conduction or not to be operated. In this way, when the currents of any corresponding input terminals of the first transformer and the second transformer are unbalanced, the maximum protection of the entire system can be achieved.

[0032] In some embodiments, the protection module can determine the positive sequence component and / or the negative sequence component of the current of the corresponding input end of the first transformer and the second transformer collected by the first sub-module and the second sub-module respectively, when the difference between the positive sequence component and the negative sequence component of the current of the corresponding input end is greater than or equal to a threshold value, the protection module controls the switch to be turned off. Conversely, when the difference between the positive sequence component and the negative sequence component of the current of the corresponding input end is less than the threshold value, the protection module controls the switch to be maintained to be turned on or not to be operated. The frequency converter system of the utility model, the protection module can control the on-off of the switch when the difference between the positive sequence component and the negative sequence component of the current of any corresponding input end of the first transformer and the second transformer is greater than or equal to a threshold value, so as to timely, effectively and accurately cut off the power grid E, thereby protecting the safety of the device and improving the safety, stability and reliability of the frequency converter system.

[0033] Taking the input end u1 of the first transformer and the input end u2 of the second transformer as an example, the protection module P can determine the positive sequence component i11+ and / or the negative sequence component i11- of the current of the input end u1. The protection module P can determine the positive sequence component i21+ and / or the negative sequence component i21- of the current of the input end u2.

[0034] For example, the protection module P can compare the positive sequence component i11+ of the current of the input end u1 with the positive sequence component i21+ of the current of the input end u2, and when the difference between the two is greater than or equal to a threshold value TH, the protection module P controls the switch K to be turned off. When the difference between the two is less than the threshold value TH, the protection module P can control the switch K to be maintained to be turned on or not to be operated.

[0035] For another example, the protection module P can compare the negative sequence component i11- of the current of the input end u1 with the negative sequence component i21- of the current of the input end u2, and when the difference between the two is greater than or equal to a threshold value TH, the protection module P controls the switch K to be turned off. When the difference between the two is less than the threshold value TH, the protection module P can control the switch K to be maintained to be turned on or not to be operated.

[0036] For another example, the protection module P can compare the positive sequence component i11+ of the current of the input end u1 with the positive sequence component i21+ of the current of the input end u2, and compare the negative sequence component i11- of the current of the input end u1 with the negative sequence component i21- of the current of the input end u2, and when one of the difference between the positive sequence component i11+ and i21+ or the difference between the negative sequence component i11- and i21- is greater than or equal to a threshold value TH, the protection module P controls the switch K to be turned off. When the difference between the positive sequence component i11+ and i21+ and the difference between the negative sequence component i11- and i21- are both less than the threshold value TH, the protection module P can control the switch K to be maintained to be turned on or not to be operated.

[0037] It should be noted that, here, only the input end u1 of the first transformer and the input end u2 of the second transformer are taken as examples for illustration, and the examples of the input end v1 of the first transformer and the input end v2 of the second transformer, and the input end w1 of the first transformer and the input end w2 of the second transformer are similar to the above, and thus will not be described herein again.

[0038] In some embodiments, the protection module can compare the positive sequence components and / or the negative sequence components of the currents of the corresponding input ends of the first transformer and the second transformer respectively, and control the switch to be turned off when the difference of the positive sequence components and / or the negative sequence components of the currents of any corresponding input end is greater than or equal to a threshold value. When the differences of the positive sequence components and the negative sequence components of the currents of all corresponding input ends are all less than the threshold value, the protection module controls the switch to be maintained in conduction or not to be operated. In this way, the maximum precision and effective protection of the entire system can be achieved when the positive sequence components and / or the negative sequence components of the currents of any corresponding input end of the first transformer and the second transformer are imbalanced.

[0039] The specific implementation of the protection module is not limited in the utility model. In some embodiments, the protection module comprises a subtracter and a comparator. The subtracter is connected with the first current acquisition module and the second current acquisition module, and can determine the difference of the currents of the corresponding input ends of the first transformer and the second transformer. The comparator is connected with the subtracter and the switch, and can control the on-off of the switch according to the difference of the currents of the corresponding input ends. When the difference of the currents of the corresponding input ends of the first transformer and the second transformer is greater than or equal to a threshold value, the output end of the comparator outputs a high level, and the switch is turned off. When the difference of the currents of the corresponding input ends of the first transformer and the second transformer is less than the threshold value, the output end of the comparator outputs a low level, and the switch is maintained in conduction or not to be operated.

[0040] Figure 3 A partial schematic diagram of a frequency converter system according to some embodiments of the utility model is shown. As shown in FIG. 1, the frequency converter system comprises a first transformer 1, a second transformer 2, a first current acquisition module 3, a second current acquisition module 4, a protection module 5, and a switch 6. Figure 2 and Figure 3As shown, the protection module P includes a subtractor P11 and a comparator P12. The subtractor P11 is connected to the first current collection module CT1 and the second current collection module CT2, and can determine the difference Δi of the currents of the corresponding input terminals of the first transformer T1 and the second transformer T2. The positive input terminal of the comparator P12 is connected to the subtractor P11. The negative input terminal of the comparator P12 is connected to a reference voltage (the reference voltage can be determined according to the threshold TH, or the threshold TH can be determined according to the reference voltage, and the two can have a preset relationship). The output terminal of the comparator P12 is connected to the switch K. The comparator P12 can control the on-off of the switch K according to the difference Δi of the currents of the corresponding input terminals of the first transformer T1 and the second transformer T2. When the difference Δi of the currents of the corresponding input terminals of the first transformer T1 and the second transformer T2 is greater than or equal to the threshold TH, the comparator P12 outputs a high level (1), and the switch K is turned off. When the difference Δi of the currents of the corresponding input terminals of the first transformer T1 and the second transformer T2 is less than the threshold, the comparator P12 outputs a low level (0), and the switch K is maintained on or not operated.

[0041] It should be noted that the utility model does not limit the number of subtractors and comparators, and the first sub-module in the first current collection module and the second sub-module in the second current collection module can share one subtractor and comparator. Alternatively, the first sub-module and the second sub-module connected to the corresponding input terminals can use corresponding subtractors and comparators respectively. In actual application, it can be determined according to requirements.

[0042] In some preferred embodiments, the switch K can adopt a circuit breaker, so that when the difference of the currents of the corresponding input terminals of the first transformer T1 and the second transformer T2 is greater than or equal to the threshold, it can be turned off in time, and the high-voltage power supply of the power grid can be cut off in time, providing safe and timely protection for the frequency converter system.

[0043] In some embodiments, the switch K may be a field-effect transistor (FET), a bipolar junction transistor (BJT), a relay, a silicon controlled rectifier (SCR), a contactor, a potentiometer, a mechanical switch, or any other switching device that can perform an equivalent or similar function. The FET may be a metal-oxide-semiconductor field-effect transistor (MOSFET). The MOSFET may be a p-channel metal-oxide-semiconductor field-effect transistor (PMOS). Alternatively, the FET may be an n-channel metal-oxide-semiconductor field-effect transistor (NMOS). The present invention does not limit the specific implementation of the switch K. In practical applications, it can be determined based on actual needs. All of these are within the scope of protection of the present invention.

[0044] The present invention is not limited to the specific implementation of the first current acquisition module CT1 and the second current acquisition module CT2. In some preferred embodiments, the first submodule and the second submodule may utilize current transformers. Current transformers can provide current conversion (e.g., current reduction) and electrical isolation, helping to improve the safety, stability, and reliability of the inverter system. In some embodiments, the first submodule and the second submodule may also utilize Hall current sensors. In practical applications, this can be determined based on actual needs.

[0045] Figure 4 FIG. 1 is a schematic diagram of a frequency converter system 10 according to some embodiments of the present invention. Figure 4 As shown, the inverter system 10 also includes a first reactor L1 and a second reactor L2. The first reactor L1 is connected to the output of the first inverter VF1. The second reactor L2 is connected to the output of the second inverter VF2. The first and second reactors L1 and L2 can be connected to the motor M. The first and second reactors suppress circulating currents caused by the output voltage difference between the two inverters, thereby improving the safety, stability, reliability, and operating efficiency of the inverters.

[0046] In some preferred embodiments, the first frequency converter VF1 and the second frequency converter VF2 can be high voltage frequency converters. Although not shown in the figures, the first frequency converter VF1 and the second frequency converter VF2 can each include a plurality of power cells cascaded. The power cells can include power tubes and diodes. The power tubes can include Insulate Gate Bipolar Transistor (IGBT), Integrated Gate Commutated Thyristor (IGCT), or Injection Enhanced Gate Transistor (IEGT), etc. The diodes can include Fast recovery diode (FRD), etc.

[0047] Although not shown in the figures, the first frequency converter VF1 and the second frequency converter VF2 can each include a memory. The memory can store operating data and other information of the first frequency converter VF1 / second frequency converter VF2. The memory can include random access memory (RAM), and can also include non-volatile memory. Further, the memory can include at least one of phase-change random access memory (PRAM), static random access memory (SRAM), dynamic random access memory (DRAM), read-only memory (ROM), electrically erasable programmable read only memory (EEPROM).

[0048] Although not shown in the figure, the first frequency converter VF1 and the second frequency converter VF2 can respectively include a controller. The controller can control the operation of the first / second frequency converter. The controller can include components and circuitry such as a control circuit, a central processing unit (CPU), a micro control unit (MCU), a digital signal processor (DSP), other general purpose processors, an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA), a complex programmable logic device (CPLD) or other programmable logic device, discrete gate or transistor logic, discrete hardware components, etc.

[0049] In some embodiments, the frequency converter system of the utility model, the first frequency converter and the second frequency converter are of the same specification. The first transformer and the second transformer are of the same specification. The first current acquisition module and the second current acquisition module are of the same specification. The first electric reactor and the second electric reactor are of the same specification. This helps to improve the circulation caused by the output voltage difference of the two frequency converters, and guarantees the safety, stability and reliability of the frequency converter system.

[0050] The frequency converter system of the utility model can realize large-current output through the parallel connection of the two frequency converters, and meets the high-power use scene. By setting two current acquisition modules and protection modules at the input ends of the two transformers, and setting a switch between the two transformers and the power grid, when the output currents of the two frequency converters are unbalanced, the frequency converter system can be effectively cut off from the power grid in time, so as to avoid the damage of the device and guarantee the safety, stability and reliability of the frequency converter system. By setting an electric reactor at the output ends of the two frequency converters, the circulation caused by the output voltage difference of the two frequency converters can be inhibited, so as to improve the safety, stability and reliability of the entire frequency converter system.

[0051] It should be noted that the utility model can only include Figures 1-4 any one or more features of any one or more embodiments. In other words, not all the features shown must be implemented in the frequency converter system of the utility model at the same time.

[0052] It should be noted that, although several modules of the frequency converter system are mentioned in the above detailed description, such a division is merely not mandatory. Indeed, according to the embodiments of the present application, the features and functions of two or more modules described above can be implemented in one module. Conversely, the features and functions of one module described above can be further divided into specific embodiments by a plurality of modules.

[0053] Finally, it should be noted that: the above is only the preferred embodiment of the present application, and is not intended to limit the present application, although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it still can be modified to the technical solutions recorded in the foregoing embodiments, or equivalent replacement of some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A frequency converter system, characterized by The application relates to a power supply system for a motor, comprising: a first frequency converter, the input end of which is connected to a first transformer, and the output end of which is connectable to the motor; a second frequency converter, the input end of which is connected to a second transformer, and the output end of which is connectable to the motor; a first current acquisition module, which is connected to the input end of the first transformer and can acquire the input current of the first transformer; a second current acquisition module, which is connected to the second transformer and can acquire the input current of the second transformer; a switch, one end of which is connected to the first current acquisition module and the second current acquisition module, and the other end of which is connected to a power grid; and a protection module, which is connected to the first current acquisition module, the second current acquisition module and the switch, and can control the on-off of the switch according to the input current of the first transformer and the input current of the second transformer. The first current acquisition module comprises a plurality of first sub-modules, which are respectively connected to the three-phase input ends of the first transformer and can respectively acquire the currents of the three-phase input ends of the first transformer.

2. The frequency converter system of claim 1, wherein, The second current acquisition module comprises a plurality of second sub-modules, which are respectively connected to the three-phase input ends of the second transformer and can respectively acquire the currents of the three-phase input ends of the second transformer.

3. The frequency inverter system of claim 2, wherein, The protection module is connected to the plurality of first sub-modules and the plurality of second sub-modules, and can control the on-off of the switch according to the currents of the corresponding input ends of the first transformer and the second transformer respectively acquired by the first sub-modules and the second sub-modules.

4. The frequency converter system of claim 3, wherein, When the difference between the currents of the corresponding input ends is greater than or equal to a threshold value, the protection module controls the switch to be turned off; and when the difference between the currents of the corresponding input ends is less than the threshold value, the protection module controls the switch to be kept on or not to be operated.

5. The frequency inverter system of claim 4, wherein, The protection module can determine the positive sequence component and / or the negative sequence component of the currents of the corresponding input ends, and when the difference between the positive sequence component and / or the negative sequence component of the currents of the corresponding input ends is greater than or equal to a threshold value, the protection module controls the switch to be turned off; and when the difference between the positive sequence component and the negative sequence component of the currents of the corresponding input ends is less than the threshold value, the protection module controls the switch to be kept on or not to be operated.

6. The frequency inverter system of claim 4, wherein, The protection module comprises a subtractor and a comparator, the subtractor is connected to the first current acquisition module and the second current acquisition module, and can determine the difference between the currents of the corresponding input ends of the first transformer and the second transformer; and the comparator is connected to the subtractor and the switch, and can control the on-off of the switch according to the difference between the currents of the corresponding input ends. The first sub-modules and the second sub-modules comprise current transformers, and the switch comprises a circuit breaker.

7. The frequency inverter system of claim 4, wherein, The application further relates to a power supply system for a motor, comprising: a first reactor and a second reactor, the first reactor is connected to the output end of the first frequency converter, the second reactor is connected to the output end of the second frequency converter, and the first reactor and the second reactor are connectable to the motor.

8. The frequency converter system of claim 4, wherein, ​ 9. The frequency converter system of any of claims 1-8, wherein, ​ ​

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