CN219436873U - Frequency converter circuit structure adopting low-voltage input and high-voltage output - Google Patents
Frequency converter circuit structure adopting low-voltage input and high-voltage output Download PDFInfo
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Abstract
The utility model provides a frequency converter circuit structure adopting low-voltage input and high-voltage output, which relates to the technical field of low-voltage distribution systems and comprises a low-voltage power grid bus, a low-voltage switch cabinet, a high-voltage frequency converter and a low-voltage precharge circuit, wherein the low-voltage precharge circuit consists of a current-limiting resistor and a resistor bypass breaker; the low-voltage network bus is connected with a low-voltage switch cabinet, the low-voltage switch cabinet is connected with a current-limiting resistor in series, the current-limiting resistor is connected with the primary side input side of a phase-shifting transformer in the high-voltage frequency converter in series, and a resistor bypass breaker is connected with two ends of the current-limiting resistor in parallel; the high-voltage frequency converter also comprises a power unit and a control cabinet, the secondary side output side of the phase-shifting transformer is connected with the power unit to supply power to the power unit, the output phase voltage of the power unit is supplied to the high-voltage motor, and the control cabinet is used for controlling the high-voltage motor to perform frequency conversion and speed regulation. The utility model can realize low-voltage input and high-voltage output in a power unit cascading mode, is easy to realize, and is mature and reliable.
Description
Technical Field
The utility model relates to the technical field of low-voltage power distribution systems, in particular to a frequency converter circuit structure adopting low-voltage input and high-voltage output.
Background
With the high-speed development of national economy, the capacity and scale of industries such as domestic petroleum pipelines, refining, metallurgy, air separation and the like are continuously expanded, and under the influence of national energy-saving, consumption-reducing and environment-friendly policies, the application range of energy-saving speed regulation products such as high-low voltage frequency converters and the like in the industry is wider and wider, and the frequency converters generally comprise power units, control cabinets and phase-shifting transformers in structure. The rated power section of the low-voltage motor is generally within 400kW, and actually, when the rated power section exceeds 200kW, the high-voltage motor is generally considered to be in the form of a high-voltage motor and matched with a frequency converter of corresponding voltage level.
With the expansion of production scale, the test platforms of some low-voltage distribution systems also need to expand capacity, when the power of a load motor is large, if a low-voltage motor is selected, rated current of the load motor can be very large, even if a low-voltage frequency converter is configured, larger impact can be generated on a power grid during starting, larger current harmonic can be generated on the power grid, and power grid pollution is caused. After the high-voltage motor scheme is selected, a high-voltage power supply is required to be introduced, and a high-voltage power distribution station is expanded, so that the high-voltage power distribution station is high in cost and long in construction period, and is not preferable. The other scheme is that the original low-voltage power supply is directly utilized, the high-voltage power supply is boosted through a boosting transformer and then provided for a high-voltage frequency converter to drive a high-voltage motor, as shown in fig. 1, a 380V power grid bus is conveyed through a low-voltage switch cabinet QF1, the high-voltage power supply is boosted through the boosting transformer and then conveyed through a high-voltage switch cabinet QF2, and the high-voltage power supply is provided for the high-voltage frequency converter to drive the high-voltage motor under the cooperation of a high-voltage pre-charging circuit.
The prior art has the following problems: 1. the system is complex, various protections are complex, and the overall cost of the system is high; 2. the system loss after the step-up transformer is added is increased; 3. the boost excitation surge current is large at the moment of starting, and the impact on the low-voltage side power grid is large; 4. besides the phase-shifting transformer of the high-voltage frequency converter, the system also comprises an intermediate step-up transformer, so that the overall system efficiency is relatively low, and unnecessary electric energy waste is caused by the self-loss of the step-up transformer.
Therefore, there is a need for improvement, and the present utility model provides a circuit structure of a frequency converter with low-voltage input and high-voltage output.
Disclosure of Invention
Aiming at the defects existing in the prior art, the utility model aims to provide a frequency converter circuit structure adopting low-voltage input and high-voltage output, and the specific scheme is as follows:
the frequency converter circuit structure adopts low-voltage input and high-voltage output, is used for outputting high voltage to a high-voltage motor, and comprises a low-voltage power grid bus, a low-voltage switch cabinet, a high-voltage frequency converter and a low-voltage precharge circuit, wherein the low-voltage precharge circuit consists of a current-limiting resistor and a resistor bypass breaker;
the low-voltage network bus is connected with a low-voltage switch cabinet, the low-voltage switch cabinet is connected with a current-limiting resistor in series, the current-limiting resistor is connected with the primary side input side of a phase-shifting transformer in the high-voltage frequency converter in series, and a resistor bypass breaker is connected with two ends of the current-limiting resistor in parallel;
the high-voltage frequency converter also comprises a power unit and a control cabinet, the secondary side output side of the phase-shifting transformer is connected with the power unit to supply power to the power unit, the output phase voltage of the power unit is supplied to the high-voltage motor, and the control cabinet is used for controlling the high-voltage motor to perform frequency conversion and speed regulation.
Further, a low-voltage incoming line breaker is arranged in the low-voltage switch cabinet.
Furthermore, the power unit is an AC-DC-AC PWM power supply line inverter structure with three-phase input and single-phase output, and comprises an A-phase power unit, a B-phase power unit and a C-phase power unit, wherein each phase is formed by connecting n power modules in series.
Further, when the low voltage is 380V, the frequency converter circuit structure can be suitable for a high-voltage motor with the rated voltage within 3-10 kV.
Compared with the prior art, the utility model has the following beneficial effects:
(1) In the utility model, the input side of the high-voltage frequency converter, namely the primary side input side of the phase-shifting transformer, is not required to be provided with a step-up transformer, exciting inrush current generated when step-up transformer is put into operation is avoided, low voltage is directly input, a bus power supply of a high-voltage power grid is directly conveyed through a low-voltage switch cabinet, and is directly supplied to the primary side input side of the phase-shifting transformer of the high-voltage frequency converter after passing through a low-voltage precharge circuit, and the secondary side output side of the phase-shifting transformer supplies power to the power unit, so that the high-voltage frequency converter directly outputs voltage to drive the high-voltage motor to perform variable-frequency speed regulation operation. In the process, the series current limiting resistor limits the switching-on current, the current limiting resistor is cut off through the resistor bypass breaker when the switching-on current is attenuated to be within a set threshold value, and the functions of pre-excitation of the dry phase-shifting transformer of the frequency converter and pre-charging of the direct current capacitor in the power unit are achieved.
(2) Compared with the existing low-voltage distribution system, the utility model only needs to make corresponding changes to the primary winding of the phase-shifting transformer in the system, namely: the primary winding of the phase-shifting transformer is manufactured into a low-voltage winding with corresponding turns according to the transformation ratio of corresponding voltage levels, the voltage level of the secondary winding of the transformer is kept unchanged from that of an original system, the control unit and the power unit of the high-voltage frequency converter are almost unchanged from those of a conventional high-voltage frequency converter, the engineering quantity of design change is small, the stability of the design of the conventional high-voltage frequency converter is inherited, the efficiency loss of an intermediate step-up transformer is saved by 1-3%, the efficiency of the whole power distribution system is improved, the stability of the frequency converter system is improved, and the fault probability is reduced.
(3) The input side of the phase-shifting transformer adopts 380V direct input, the secondary side of the phase-shifting transformer is kept unchanged from the original design, the circuit structure of the high-voltage frequency converter can output 10kV high voltage in a cascading mode of the power unit, and the application range is wide.
Drawings
Fig. 1 is an overall schematic diagram of a low voltage power distribution system in the background;
FIG. 2 is a schematic diagram illustrating a frequency converter circuit structure according to the present utility model;
fig. 3 is a schematic topology diagram of a frequency converter circuit structure.
Reference numerals: 1. a low-voltage power grid bus; 2. a low voltage precharge circuit; 21. a current limiting resistor; 22. a resistor bypass breaker; 3. a high voltage frequency converter; 31. a phase-shifting transformer; 32. a power unit; 4. a low voltage switchgear; 41. a low voltage inlet circuit breaker; 5. a high voltage motor.
Detailed Description
The present utility model will be described in further detail with reference to examples and drawings, but embodiments of the present utility model are not limited thereto.
In the prior art, the mode of boosting by using a low-voltage power supply and providing the boosted power supply to the high-voltage frequency converter 3 to drive the high-voltage motor 5 has the defect that a power grid with low voltage level can directly drive the high-voltage motor 5. The complexity of the system is reduced, the reliability of the system is improved, and the manufacturing cost is reduced.
For better explanation, this embodiment is described by taking a test bed technical modification as an example, specifically, the power grid voltage is 380V, and the test bed load process requirement is to load a motor with rated power of 630 kW. A set of high-voltage three-phase asynchronous motor and a corresponding variable-frequency speed regulating system are required to be configured to finish starting and perform variable-frequency speed regulating operation according to process requirements.
In order to meet the requirements of a test bed, the above-mentioned frequency converter circuit structure is used for realizing the output voltage of the high-voltage motor 5, as shown in the following figure 2, the frequency converter circuit structure comprises a low-voltage network bus 1, a low-voltage switch cabinet 4, a low-voltage pre-charging loop 2 and a high-voltage frequency converter 3, wherein the low-voltage network bus 1 is used for providing low voltage, a power supply of the low-voltage network bus 1 with 380V is directly conveyed through the low-voltage switch cabinet 4, and then is directly provided for the high-voltage frequency converter 3 after passing through the low-voltage pre-charging loop 2, and the high voltage is directly output through the high-voltage frequency converter 3 to drive the high-voltage motor 5 to perform frequency conversion speed regulation. Compared with the prior art, a step-up transformer and a high-voltage switch cabinet QF2 are not needed, and the high-voltage pre-charging circuit is replaced by the low-voltage pre-charging circuit 2.
Specifically, a low-voltage wire-feeding breaker 41 is provided in the low-voltage switch cabinet 4, the low-voltage grid bus 1 is connected to the low-voltage switch cabinet 4, and the low-voltage wire-feeding breaker 41 controls opening and closing to control input of low voltage. The high-voltage frequency converter 3 is composed of a phase-shifting transformer 31, a power unit 32 and a control cabinet, the low-voltage pre-charging loop 2 is composed of a current-limiting resistor 21 and a resistor bypass breaker 22, and the connection relationship among the low-voltage switch cabinet 4, the low-voltage pre-charging loop 2 and the high-voltage frequency converter 3 is that the low-voltage wire-feeding breaker 41 is connected with the current-limiting resistor 21 in series, the current-limiting resistor 21 is connected with the primary side input side of the phase-shifting transformer 31 in the high-voltage frequency converter 3 in series, and the resistor bypass breaker 22 is connected with two ends of the current-limiting resistor 21 in parallel.
In the high-voltage inverter 3, the phase-shifting transformer 31 supplies power to the power unit 32 through voltage division, the power unit 32 is a component of the high-voltage inverter 3 which uses power electronic devices to rectify, filter and invert, in this embodiment, the power unit 32 is an ac-dc-ac PWM voltage source type inverter structure with three-phase input and single-phase output, and includes an a-phase power unit 32, a B-phase power unit 32 and a C-phase power unit 32, each phase is formed by connecting n power modules in series. The control cabinet is used for controlling variable frequency speed regulation, transmitting command signals to the motor and controlling the rotating speed of the high-voltage motor 5.
In the low-voltage pre-charging circuit 2, the current limiting resistor 21 is actually arranged by connecting a resistor in series with the main circuit, and connecting a proper resistor in series between the low-voltage network bus 1 and the high-voltage frequency converter 3, so that the switching-on current can be limited, the current to be switched on is attenuated to be within a set threshold value, the current limiting resistor 21 is cut off through the resistor bypass breaker 22, and the functions of pre-exciting the dry-type phase-shifting transformer 31 of the high-voltage frequency converter 3 and pre-charging the direct current capacitor in the power unit 32 are realized.
In accordance with the above disclosure, a detailed system principle topology of the present utility model is shown in fig. 3, including a low voltage incoming circuit breaker 41, a current limiting resistor 21, a resistor bypass circuit breaker 22, a phase shifting transformer 31, a power unit 32, and a control unit. QF1 in fig. 3 is a low voltage incoming circuit breaker 41; r is a current limiting resistor 21 of the low voltage precharge circuit 2, QF-R is a resistor bypass breaker 22 of the low voltage precharge circuit 2; A1-An are A phase power units 32, B1-Bn are B phase power units 32, and C1-Cn are C phase power units 32 (n represents the number of stages of the power units 32, and the number is not limited); m is a high-voltage three-phase asynchronous motor.
In a high voltage inverter system, the number of power modules in the power unit 32 of the high voltage inverter 3 is related to the voltage class of the high voltage motor 5, and the conventional configuration is detailed in the following table:
for a better description, the utility model is illustrated with a 380V grid input, 10kV output as an example.
The input side of the phase-shifting transformer 31 adopts 380V voltage to directly input, the multiple secondary windings of the phase-shifting transformer 31 adopt 720V voltage to output, namely the transformation ratio of the phase-shifting transformer 31 is designed to be 380V/720V multiplied by 24, three-phase 380V alternating current sent by the bus 1 of the power grid is connected into one-time wiring copper bars of the phase-shifting transformer 31, and the phase-shifting transformer 31 comprises 24 720V secondary windings to form a 48-pulse rectification structure.
Because each phase of the three power units 32 with different phases is formed by connecting n power modules in series, in the embodiment, each phase is formed by connecting 8 power units 32 with rated voltage 720V in series, after the voltage of a 380V power grid bus 1 is transformed by a phase-shifting transformer 31 with multiple secondary sides, the power units 32 are supplied with power, and the voltage of each output phase reaches 5774V, in general, the voltage reaches 10kV, so that the high voltage with variable voltage and variable frequency can be directly output, and can be supplied to the high-voltage motor 5. The above description is only a preferred embodiment of the present utility model, and the protection scope of the present utility model is not limited to the above examples, and all technical solutions belonging to the concept of the present utility model belong to the protection scope of the present utility model. It should be noted that modifications and adaptations to the present utility model may occur to one skilled in the art without departing from the principles of the present utility model and are intended to be within the scope of the present utility model.
Claims (4)
1. The frequency converter circuit structure adopting low-voltage input and high-voltage output is used for outputting high voltage to a high-voltage motor (5), and comprises a low-voltage network bus (1), a low-voltage switch cabinet (4) and a high-voltage frequency converter (3), and is characterized by further comprising a low-voltage pre-charging loop (2), wherein the low-voltage pre-charging loop (2) consists of a current-limiting resistor (21) and a resistor bypass breaker (22);
the low-voltage network bus (1) is connected with the low-voltage switch cabinet (4), the low-voltage switch cabinet (4) is connected in series with the current-limiting resistor (21), the current-limiting resistor (21) is connected in series with the primary side input side of the phase-shifting transformer (31) in the high-voltage frequency converter (3), and the resistor bypass breaker (22) is connected in parallel with two ends of the current-limiting resistor (21);
the high-voltage frequency converter (3) further comprises a power unit (32) and a control cabinet, the secondary side output side of the phase-shifting transformer (31) is connected with the power unit (32) to supply power to the power unit (32), the output phase voltage of the power unit (32) is supplied to the high-voltage motor (5), and the control cabinet is used for controlling the high-voltage motor (5) to perform frequency conversion and speed regulation.
2. The frequency converter circuit arrangement with low voltage input and high voltage output according to claim 1, characterized in that a low voltage incoming circuit breaker (41) is arranged in the low voltage switchgear (4).
3. The frequency converter circuit structure adopting low-voltage input and high-voltage output according to claim 2, wherein the power unit (32) is an ac-dc-ac PWM power line inverter structure with three-phase input and single-phase output, and comprises an A-phase power unit (32), a B-phase power unit (32) and a C-phase power unit (32), and each phase is formed by connecting n power modules in series.
4. A frequency converter circuit arrangement with low voltage input and high voltage output according to claim 3, characterized in that it is applicable to high voltage motors (5) with rated voltages in the range of 3-10kV when the low voltage is 380V.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320754939.1U CN219436873U (en) | 2023-04-07 | 2023-04-07 | Frequency converter circuit structure adopting low-voltage input and high-voltage output |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202320754939.1U CN219436873U (en) | 2023-04-07 | 2023-04-07 | Frequency converter circuit structure adopting low-voltage input and high-voltage output |
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| Publication Number | Publication Date |
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| CN219436873U true CN219436873U (en) | 2023-07-28 |
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| Application Number | Title | Priority Date | Filing Date |
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| CN202320754939.1U Active CN219436873U (en) | 2023-04-07 | 2023-04-07 | Frequency converter circuit structure adopting low-voltage input and high-voltage output |
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| CN (1) | CN219436873U (en) |
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- 2023-04-07 CN CN202320754939.1U patent/CN219436873U/en active Active
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