CN213817576U - Four-quadrant frequency converter pre-charging circuit and coal mining machine electrical control system - Google Patents
Four-quadrant frequency converter pre-charging circuit and coal mining machine electrical control system Download PDFInfo
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- CN213817576U CN213817576U CN202022817248.0U CN202022817248U CN213817576U CN 213817576 U CN213817576 U CN 213817576U CN 202022817248 U CN202022817248 U CN 202022817248U CN 213817576 U CN213817576 U CN 213817576U
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Abstract
The utility model relates to a four-quadrant converter is charging circuit and coal-winning machine electrical control system in advance belongs to converter technical field, a four-quadrant converter is charging circuit includes rectifier circuit, filter circuit and inverter circuit, rectifier circuit is the three-phase rectifier bridge that the IGBT constitutes, inverter circuit is the three-phase inverter bridge that the IGBT constitutes, filter circuit sets up in rectifier circuit with between the inverter circuit, filter circuit comprises two electric capacity group series connections, and two electric capacity group is parallelly connected with voltage-sharing resistance respectively; each capacitor bank comprises at least one capacitor; two phase input sides of the rectification circuit are respectively connected with a relay, and the relays are connected with a pre-charging resistor in parallel. The utility model discloses use direct current relay to replace the contactor, the contactor device is bulky, with high costs problem when solving big charging current.
Description
Technical Field
The utility model relates to a converter technical field, in particular to four-quadrant converter precharge circuit and coal-winning machine electrical control system.
Background
The pre-charging circuit is an essential link of the voltage type AC-DC-AC frequency converter. When a system is powered on, the initial voltage of the intermediate direct-current link supporting the energy storage bus capacitor is zero, and a large voltage difference between the high voltage output by the high-voltage alternating-current power supply and the zero voltage of the bus capacitor causes a huge inrush current at the moment of power-on, so that power devices such as an IGBT (insulated gate bipolar transistor), a power diode and the like and protection devices such as a fuse and the like in a frequency converter circuit are easily damaged, and the service life of the bus capacitor can also be reduced. Therefore, before the high-voltage ac power supply supplies power to the frequency converter, the support energy storage bus capacitor of the intermediate dc link needs to be pre-charged and protected to establish a bus voltage.
In a traditional pre-charging circuit, a charging contactor is generally connected in series in a main loop, and one or more charging resistors R are connected across two ends of the contactor to charge a bus capacitor of a frequency converter. As shown in fig. 1, a three-phase input power is connected to an input terminal (R/S/T) of the inverter, and is converted into a dc voltage through a charging diode D1, and the dc voltage is charged to a bus electrolytic capacitor C1 and C2 through a charging resistor R2, when the bus voltage reaches a certain value, an internal switching power supply (not shown in the figure) of the inverter starts to operate, and after an internal control circuit board of the inverter judges that charging is completed, a contactor is controlled to be closed, and the charging resistor R2 is short-circuited, thereby completing the charging process. In the charging process, the IGBT is not controlled to be conducted by depending on the anti-parallel diode in the IGBT to work. And after the charging process is finished, the control panel controls the IGBT to modulate. The prior publication CN206432915U provides a main circuit of an energy feedback frequency converter, and a charging circuit of the energy feedback frequency converter also adopts a contactor. The traditional pre-charging circuit is suitable for a small power section (30 kW-110 kW), and has the advantage of simple structure. Because the bus current in the high-power frequency converter (160-350 kW) is increased, a large-current pre-charging contactor needs to be selected, and the large-current contactor is large in size and heavy in weight, so that the type selection is difficult, the integral size of the frequency converter is large, the power density is low, and the high-power development trend of a coal mining machine cannot be met.
In addition, the prior publication CN107634658A provides a frequency converter control circuit, which adopts a diode for charging, has no contactor structure, and the rectifying unit is a thyristor, and belongs to two-quadrant application.
Disclosure of Invention
An object of the utility model is to the above-mentioned problem, provide a four-quadrant converter is charging circuit and coal-winning machine electrical control system in advance, small, power density is high.
The purpose of the utility model is realized like this:
a four-quadrant frequency converter pre-charging circuit comprises a rectifying circuit, a filter circuit and an inverter circuit, wherein the rectifying circuit is a three-phase rectifying bridge formed by IGBTs, the inverter circuit is a three-phase inverter bridge formed by IGBTs, the filter circuit is arranged between the rectifying circuit and the inverter circuit, the filter circuit is formed by connecting two capacitor sets in series, and the two capacitor sets are respectively connected with a voltage-sharing resistor in parallel; each capacitor bank comprises at least one capacitor;
two phase input sides of the rectification circuit are respectively connected with a relay, and the relays are connected with a pre-charging resistor in parallel.
Preferably, the charging system further includes:
the rectification control loop is connected with the rectification circuit and used for controlling the rectification circuit;
and the inversion control loop is connected with the inversion circuit and used for controlling the inversion circuit.
Preferably, the relay is a high-voltage direct-current relay, and the rated current of the high-voltage direct-current relay is not lower than 250A.
Preferably, the relay adopts a magnetic quenching mode, inert gas is filled in the relay, a control loop uses a 24V control power supply, an energy-saving device is arranged in the relay, and a main loop terminal does not distinguish a positive electrode from a negative electrode.
Preferably, the relay comprises two or more high voltage direct current relays connected in parallel.
Preferably, the capacitor is a thin film capacitor or an electrolytic capacitor.
Preferably, two of the relays on the two-phase input side of the rectifier circuit are simultaneously opened or closed.
The utility model also discloses a coal-winning machine electrical control system contains aforementioned arbitrary four-quadrant converter precharge circuit's technical scheme.
The utility model has the advantages that:
1) the four-quadrant frequency converter can be suitable for the four-quadrant frequency converter of the coal mining machine, the size is reduced, the failure rate is reduced, and the power density and the quality of the four-quadrant frequency converter of the frequency converter are obviously improved.
2) The high-voltage direct-current relay parallel connection structure can be applied to a high-power frequency converter, and the working condition adaptability of the coal mining machine traction speed regulating system is improved.
Drawings
FIG. 1 shows a block diagram of a conventional four quadrant inverter precharge circuit;
fig. 2 shows a block diagram of the precharge circuit of the four-quadrant converter of the present invention.
Fig. 3 shows a schematic diagram of a single relay embodiment.
Fig. 4 shows a schematic diagram of a dual relay embodiment.
Fig. 5 shows a flow chart of a control method for four-quadrant inverter precharging.
Detailed Description
Various embodiments of the present invention will be described with reference to the accompanying drawings. In the specification and drawings, elements having similar structures or functions will be denoted by the same reference numerals. It is to be understood that the drawings are designed solely for the purposes of illustration and description and not as a definition of the limits of the invention. The dimensions shown in the figures are for clarity of description only and are not intended to be limiting, nor are they intended to be exhaustive or to limit the scope of the invention.
In the description of the present invention, it is to be understood that the terms "upper", "lower", "front", "rear", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", "outer", and the like indicate orientations or positional relationships based on those shown in the drawings, and are only for convenience of description and simplification of description, and do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore, should not be construed as limiting the present invention.
The utility model provides a coal-winning machine contains a four-quadrant converter pre-charge circuit to satisfy the demand that the high-power converter of coal-winning machine needs the heavy current to charge.
Fig. 2 shows a block diagram of an embodiment of a four-quadrant frequency converter pre-charging circuit, which is particularly suitable for a coal mining machine.
As shown in fig. 2, the four-quadrant inverter precharge circuit includes a rectification circuit 9, a filter circuit, an inverter circuit 10, a rectification control circuit 11, an inverter control circuit 12, and two relays.
The rectifier circuit 9 is a three-phase rectifier bridge composed of six IGBTs, and converts three-phase ac voltage into dc voltage.
The inverter circuit 10 is a three-phase inverter bridge composed of six IGBTs, and is configured to invert the direct current obtained by the rectifier circuit 9 to obtain an alternating current.
The filter circuit is arranged between the rectification circuit 9 and the inverter circuit 10 and is formed by connecting two capacitor sets in series. Each capacitor group comprises at least one capacitor, and the capacitor can be selected from a thin film capacitor or an electrolytic capacitor. The voltage withstanding value of a common electrolytic capacitor is limited and is lower than the voltage peak value of a direct current loop (namely, a filter circuit), and in consideration of the capacity and the filter effect, the direct current loop filter circuit generally connects a plurality of electrolytic capacitors in parallel into one group, and then connects two groups of capacitors in series. The filter circuit shown in fig. 2 employs a dc circuit composed of a first dc capacitor 5 and a second dc capacitor 6, specifically a capacitor bank composed of an electrolytic capacitor or a thin film capacitor, and when a thin film capacitor is used, if the withstand voltage is sufficient, a series structure may not be used.
As shown in fig. 2, the first direct current capacitor 5 and the second direct current capacitor 6 are respectively and correspondingly connected in parallel with a first equalizing resistor 7 and a second equalizing resistor 8, and are used for balancing the voltage of the upper and lower bridge capacitors and discharging the capacitors when the power is stopped; because the resistance value of the resistor is generally accurate, the voltage distribution of the first direct current capacitor 5 and the second direct current capacitor 6 is balanced, the voltage-sharing effect is ensured, the service life of the capacitor is prolonged, and the service life of the frequency converter is prolonged.
The rectification control circuit 11 is connected with the rectification circuit 9 and used for monitoring three-phase input voltage, three-phase input current and direct current circuit voltage in real time to generate various control power supplies and meet the requirements of the rectification circuit 9 on the power supplies.
The inverter control circuit 12 is connected to the inverter circuit 10, and is configured to control the inverter circuit 10. The inverter circuit 10 obtains alternating current to supply to the motor, and the motor is in a dragging state; when the motor is in deceleration, energy generated by the motor is transmitted to a direct current bus through the inverter circuit 10, and at the moment, if the voltage of the direct current bus is higher than a preset value, the rectifying circuit 9 feeds the energy back to a power grid.
The two relays are connected to the two-phase input side of the rectifying circuit 9, are simultaneously turned on or off, and are connected in parallel to a precharge resistor. As shown in fig. 2, a first relay 1 and a second relay 2 are connected to two-phase input sides of the rectifying circuit 9, respectively, and the first relay 1 and the second relay 2 are connected in parallel with a first precharge resistor 3 and a second precharge resistor 4, respectively. The two relays are high-voltage direct-current relays with rated current of 250A, and have the basic functions of high voltage resistance, load resistance, impact resistance, strong arc extinguishing capability and strong breaking capability. The relay adopts a magnetic blow-out arc extinguishing mode, has the characteristics of simple structure and process, low cost and high arc extinguishing efficiency, and has the principle that two pieces of magnetic steel with opposite polarities are placed in parallel and are in axial symmetry with the center of a contact, a uniform magnetic field is formed in the center of the contact, when the magnetic field intensity at the center is higher, the arc blowing effect is better, the arc extinguishing capability is stronger, and the load-resisting capability of a product is also higher. The high-voltage relay is filled with inert gas, has the ability of cooling electric arcs, can quickly complete arc extinction, and is suitable for high-speed pre-charging. The high-voltage direct-current relay uses a 24V control power supply, is internally provided with an energy-saving device, and maintains the voltage to be less than the closing voltage. In addition, the main loop terminal of the relay does not distinguish between the positive and negative electrodes. The pre-charging circuit is arranged at the front section of the rectifier bridge, so that distributed inductance of positive and negative copper bars can be reduced and loss is reduced compared with the pre-charging circuit arranged on a direct current loop (namely a filter circuit).
The relay on the input side of each phase in the implementation is single, but when the high-power application is carried out, the relay can also be two or more high-voltage direct-current relays connected in parallel, the size of the relay is smaller than that of the contactor, and the relay is beneficial to being integrated in a frequency converter system of a coal mining machine.
Fig. 3 shows a schematic diagram of a single relay embodiment. The power supply of the frequency converter is input to the frequency converter through copper bars R1, S1 and T1. The copper bar R1 is connected to one end of the main loop terminal of the first relay 101, and the copper bar T1 is connected to one end of the main loop terminal of the second relay 102; the other end of the main loop terminal of the first relay 101 is connected to a copper bar R2, the other end of the main loop terminal of the second relay 102 is connected to a copper bar T2, and the copper bar S1 is directly connected with the copper bar S2. The control power terminals of the relay 101 and the relay 102 are A1 and A2, A1 is a positive electrode, A2 is a negative electrode, and the control power terminals are connected to a control loop. The first pre-charge resistor is connected to the copper bars R1 and R2, and the second pre-charge resistor is connected to the copper bars T1 and T2.
Fig. 4 shows a schematic diagram of a double relay embodiment, similar to the single relay embodiment, the relay is connected with a copper bar R1 and a copper bar R2, but in the application of the high-power frequency converter, in order to improve the current switching-on and switching-off capacity, a third relay 103 is connected in parallel with the first relay 101, and a fourth relay 104 is connected in parallel with the second relay 102, which are connected in parallel through the copper bars.
The utility model also provides a control method that four quadrant converter precharged is applicable to aforementioned four quadrant converter precharge circuit, as shown in fig. 5, after the electricity was gone up to the converter, the back that begins to charge promptly, and this control method specifically includes following flow:
s1, and the pre-charging resistor charges two capacitors in the dc loop (i.e., the filter circuit described above), and the operation mode is three-phase full-bridge uncontrolled rectification.
S2, the rectification control loop judges whether the DC voltage in the DC loop reaches a first preset range.
And S3, when the direct current voltage in the direct current loop reaches a first preset range, the rectification control loop starts to operate.
And S4, the rectification control loop judges whether the rising speed of the direct current voltage and the current reaches a second preset range.
And S5, when the rising speed of the direct current voltage and the current reaches a second preset range, the rectification control loop controls the power supply to the two relays so as to control the other relay to be electrified and close the charging loop.
And when the direct current voltage reaches 90% of the rated direct current voltage and the charging current change rate di/dt is less than 5% of the rated current, finishing charging.
Although specific embodiments of the present invention have been described above, it will be understood by those skilled in the art that this is by way of example only and that the scope of the invention is defined by the appended claims. Various changes and modifications to these embodiments may be made by those skilled in the art without departing from the spirit and the principles of the present invention, and these changes and modifications are all within the scope of the present invention.
Claims (8)
1. A four-quadrant frequency converter pre-charging circuit is characterized by comprising a rectifying circuit, a filtering circuit and an inverter circuit, wherein the rectifying circuit is a three-phase rectifying bridge formed by IGBT (insulated gate bipolar transistor), the inverter circuit is a three-phase inverter bridge formed by IGBT, the filtering circuit is arranged between the rectifying circuit and the inverter circuit, the filtering circuit is formed by connecting two capacitor sets in series, and the two capacitor sets are respectively connected with a voltage-sharing resistor in parallel; each capacitor bank comprises at least one capacitor;
two phase input sides of the rectification circuit are respectively connected with a relay, and the relays are connected with a pre-charging resistor in parallel.
2. The four-quadrant inverter precharge circuit of claim 1, further comprising:
the rectification control loop is connected with the rectification circuit and used for controlling the rectification circuit;
and the inversion control loop is connected with the inversion circuit and used for controlling the inversion circuit.
3. The four-quadrant inverter pre-charge circuit of claim 1, wherein the relay is a high voltage direct current relay and the rated current of the high voltage direct current relay is not less than 250A.
4. The pre-charging circuit of the four-quadrant frequency converter according to claim 3, wherein the relay adopts a magnetic quenching mode, inert gas is filled in the relay, a control circuit uses a 24V control power supply, an energy-saving device is arranged in the relay, and a main loop terminal does not distinguish a positive electrode from a negative electrode.
5. The four-quadrant inverter pre-charge circuit of claim 2, wherein the relay comprises two or more high voltage direct current relays connected in parallel.
6. The four-quadrant inverter pre-charge circuit of claim 1, wherein the capacitor is a thin film capacitor or an electrolytic capacitor.
7. The four-quadrant inverter precharge circuit according to claim 1, wherein two of said relays on the two-phase input side of said rectifier circuit are simultaneously turned on or off.
8. An electrical control system of a coal mining machine, characterized by comprising the four-quadrant frequency converter pre-charging circuit of any one of claims 1 to 7.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022817248.0U CN213817576U (en) | 2020-11-30 | 2020-11-30 | Four-quadrant frequency converter pre-charging circuit and coal mining machine electrical control system |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202022817248.0U CN213817576U (en) | 2020-11-30 | 2020-11-30 | Four-quadrant frequency converter pre-charging circuit and coal mining machine electrical control system |
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| Publication Number | Publication Date |
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| CN213817576U true CN213817576U (en) | 2021-07-27 |
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| CN202022817248.0U Active CN213817576U (en) | 2020-11-30 | 2020-11-30 | Four-quadrant frequency converter pre-charging circuit and coal mining machine electrical control system |
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