Voltage sag treatment device applied to alternating current contactor

Abstract

The voltage sag treatment device is connected between an alternating-current power grid and an alternating-current contactor coil and comprises an alternating-current power supply circuit connected with the alternating-current power grid, and the input end and the output end of an alternating-current input filter circuit are connected with the alternating-current power supply circuit and a rectification filter circuit respectively. The output end of the alternating current power supply circuit is connected with the alternating current contactor coil and the alternating current input filter circuit; the alternating current power supply circuit provides alternating current for the alternating current contactor coil or sends electric energy to the alternating current input filter circuit when voltage sag occurs in the alternating current; the rectification filter circuit converts alternating current output by the alternating current input filter circuit into direct current and stores the direct current, and when alternating current voltage sags, the direct current power supply circuit provides the direct current for an alternating current contactor coil. According to the invention, direct current can be provided for the alternating-current contactor coil when the alternating-current voltage sags, and alternating current can be provided for the alternating-current contactor coil again when the alternating-current voltage returns to normal, so that the alternating-current contactor is ensured to be in a normal working state all the time.

Description

Technical Field

[0001] The present invention relates to the technical field of contactor control, and in particular to a voltage sag control device applied to an AC contactor. Background Art

[0002] In the power system, AC contactors can be used to connect or disconnect motors. When the AC power grid experiences a voltage sag, the coil of the AC contactor will trip due to undervoltage, which will further cause the main contacts of the AC contactor to be released. At present, the voltage sag control measures for the contactor coil include: using a protective device in series with the contactor coil, using an energy storage delay element, or using a UPS for system protection. However, the above measures have the disadvantages of low reliability, high cost, and control delay. Specifically, the UPS provides backup power for the equipment after the voltage sag, so that the equipment continues to operate. However, the UPS is expensive and has low power, and cannot be used on a large scale. It is only suitable for monitoring or some very important and low-power equipment. When the line voltage sags, the permanent magnet AC contactor can ensure that the contactor is still in the energized state, and can work normally when the line voltage returns to the normal value. However, the price of the permanent magnet AC contactor is relatively high, and the line voltage is in an unstable state when the voltage sag occurs. At this time, the contactor is in the energized state, which will cause the voltage applied to the motor to be unstable, and the motor may burn out due to the low voltage. Summary of the invention

[0003] Purpose of the invention: The purpose of the present invention is to provide a voltage sag management device for AC contactors with high reliability and fast response. When the AC voltage sags temporarily, it can provide stable DC power to the AC contactor coil to keep the AC contactor closed.

[0004] Technical solution: To achieve the above-mentioned purpose, a voltage sag control device for an AC contactor according to the present invention is connected between an AC power grid and an AC contactor coil. The device includes an AC power supply circuit connected to the AC power grid, an output end of the AC power supply circuit is connected to the AC contactor coil and an AC input filter circuit, an output end of the AC input filter circuit is connected to a rectifier filter circuit, the AC power supply circuit provides AC power to the AC contactor coil or sends electric energy to the AC input filter circuit when a voltage sag occurs in the AC power; the rectifier filter circuit converts the AC power output by the AC input filter circuit into DC power and stores it, and when the AC voltage sags, the DC power supply circuit provides DC power to the AC contactor coil.

[0005] Among them, the device also includes a single-chip microcomputer control circuit and a switch drive circuit. The input end of the single-chip microcomputer control circuit is connected to the AC power supply circuit and the DC power supply circuit, the output end of the single-chip microcomputer control circuit is connected to the switch drive circuit, and the output end of the switch drive circuit is connected to the AC power supply circuit and the DC power supply circuit; the single-chip microcomputer control circuit collects the AC voltage and DC voltage of the input AC power supply circuit and the DC power supply circuit, and outputs a drive signal to the switch drive circuit to control the state of the AC power supply circuit and the DC power supply circuit.

[0006] The AC input filter circuit includes a common mode inductor L arranged at the live terminal L1 and the neutral terminal N1 of the AC input of the AC power grid, capacitors CX1 and CX2 connected in parallel at both ends of the common mode inductor L, and a fuse FU1 connected in series at the live terminal L1.

[0007] The AC power supply circuit includes electronic switches K1 and K2 respectively connected in series to the AC output terminals L2 and N2 of the AC input filter circuit. The electronic switches K1 and K2 are controlled to open and close by driving signals output by the single chip control circuit.

[0008] Among them, the rectification and filtering circuit includes a single-phase rectifier bridge and a filter capacitor C1, wherein the output ends L2 and N2 of the AC input filter circuit are connected in parallel to the single-phase rectifier bridge circuit composed of rectifier diodes D1, D2, D3, and D4, and the filter capacitor C1 is connected in parallel to the single-phase rectifier bridge circuit to store direct current converted by the single-phase rectifier bridge.

[0009] The DC power supply circuit includes a step-down circuit, electronic switches K3 and K4, a fuse FU2, and an input filter capacitor C2. The capacitor C2 is connected in parallel to the output capacitor C1 of the rectifier filter circuit. The step-down circuit is composed of a MOS tube Q1, a diode D5, an inductor L3 and a capacitor C3. The electronic switches K3 and K4 are respectively connected in series at both ends of the AC contactor coil, and FU2 is connected in series to one end of the electronic switch K3.

[0010] Among them, the single-chip microcomputer control circuit includes an ARM single-chip microcomputer STM32F103RB, a crystal oscillator Y, and capacitors C4 and C5 for storing charge in the crystal oscillator bypass. The collected AC voltage is sent to the AN0 port of the single-chip microcomputer through a voltage divider filter circuit composed of resistors R1, R2 and capacitor C6, and the collected DC voltage is sent to the AN1 port of the single-chip microcomputer through a voltage divider filter circuit composed of R3, R4 and C7. DR1, DR2, DR3, and DR4 on the single-chip microcomputer are respectively drive signal ports of electronic switches K1, K2, K3, and K4, and PWM1 is the drive signal port of the MOS tube Q1 on the DC power supply circuit.

[0011] The switch driving circuit includes an isolation optocoupler, resistors R5, R6, a capacitor C8 and a voltage regulator VD1, wherein R5 is a current limiting resistor connected to the diode end of the isolation optocoupler, a power supply VCC is added to the secondary side of the isolation optocoupler to provide a high voltage, capacitor C8 is a filter capacitor, resistor R6 is a driving resistor of the electronic switches K1, K2, K3, K4 and the MOS tube Q1, and generates a driving voltage for the electronic switches K1, K2, K3, K4 and the MOS tube Q1, and the voltage regulator VD1 is used to limit the voltage spike of the driving voltage.

[0012] Wherein, the device is a method for supplying power to an AC contactor coil, comprising:

[0013] When the single-chip microcomputer control circuit detects that the AC voltage of the AC power supply circuit is within the set required range, the AC power supply circuit provides AC power to the AC contactor coil, and the rectifier and filter circuit stores energy;

[0014] When the single-chip control circuit detects that the AC voltage of the AC power supply circuit has a voltage drop, the rectifier filter circuit provides DC power to the AC contactor coil through the DC power supply circuit;

[0015] When the voltage sag is restored, the AC power supply circuit is switched to provide AC power to the AC contactor coil, and the rectifier and filter circuit stores energy.

[0016] Beneficial effects: The present invention has the following advantages: 1. The device is connected in parallel to the AC contactor coil loop. When the AC voltage is normal, the AC contactor coil is powered by the AC power supply circuit. Even if a fault occurs in the DC power supply circuit of the device, the AC power supply circuit will not be affected, thereby ensuring that the AC contactor continues to operate normally and improving the power supply reliability of the AC contactor;

[0017] 2. This device can provide direct current to the AC contactor coil when the AC voltage drops temporarily, ensuring that the AC contactor coil continues to maintain without releasing. When the AC voltage returns to normal, it can supply AC power to the AC contactor coil again, ensuring that the AC contactor is always in normal working condition;

[0018] 3. The switching time between AC power supply and DC power supply of this device is less than 2ms, which is short, so as to ensure that the contactor coil will not lose power when switching from AC power supply to DC power supply when the voltage drops temporarily, or when switching from DC power supply to AC power supply when the voltage drops temporarily.

[0019] 4. This device can further distinguish whether the power supply system is under normal control of power outage or a voltage sag event occurs, and will not affect the normal start and stop control of the AC contactor. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1This is a schematic diagram of the principle of the voltage sag control device of the present invention;

[0021] Figure 2 This is the AC input filter circuit diagram;

[0022] Figure 3 This is the AC power supply circuit diagram;

[0023] Figure 4 This is the rectifier filter circuit diagram;

[0024] Figure 5 This is a DC power supply circuit diagram;

[0025] Figure 6 This is the single chip microcomputer control circuit diagram;

[0026] Figure 7 This is the switch driving circuit diagram. DETAILED DESCRIPTION

[0027] The technical solution of the present invention is described in detail below in conjunction with the embodiments and drawings.

[0028] like Figure 1 As shown, the voltage sag control device of the present invention includes an AC input filter circuit, a rectifier filter circuit, an AC power supply circuit, a DC power supply circuit, a drive circuit, and a single-chip microcomputer control circuit; wherein the AC input filter circuit is connected to the rectifier filter circuit and the AC power supply circuit, the rectifier filter circuit is connected to the DC power supply circuit, the AC power supply circuit is connected to the AC contactor coil, the DC power supply circuit is connected to the AC contactor coil, the drive circuit is connected to the AC power supply circuit, the DC power supply circuit, and the single-chip microcomputer control circuit, and the single-chip microcomputer control circuit is also connected to the AC power supply circuit and the DC power supply circuit.

[0029] like Figure 2 As shown in FIG. 1 , the AC input filter circuit includes a fuse FU1, X capacitors CX1 and CX2, and a common-mode inductor L. The fuse FU1 is set at the live wire end L1. The two coils of the common-mode inductor L are wound in the same direction. When current flows through, the magnetic fields generated can cancel each other out and will not cause saturation of the magnetic core. The common-mode inductor L is equivalent to an inductor with a large inductance for common-mode noise, which can effectively suppress common-mode conducted noise. The capacitors CX1 and CX2 connected in parallel at both ends of the common-mode inductor L suppress differential-mode noise. Among them, L1 (live wire end) and N1 (neutral wire end) are AC input ends, and FU1 is a fuse to realize the input overcurrent protection function. L2 (live wire end) and N2 (neutral wire end) are the AC output ends of the AC input filter circuit. This circuit can realize the input EMC anti-interference protection function.

[0030] like Figure 3As shown, the AC power supply circuit includes electronic switches K1 and K2 for AC power supply. The electronic switches K1 and K2 are respectively connected in series on the line where the L2 and N2 terminals are located. The other end of the line is connected to the AC contactor coil. When K1 and K2 are connected at the same time and the AC output voltage reaches the rated voltage of the AC contactor coil, the contactor is closed. After the switch is closed, the circuit can provide stable AC power to the AC contactor coil to ensure that the contactor is normally closed.

[0031] like Figure 4 As shown, the rectifier filter circuit includes a single-phase rectifier bridge and a filter capacitor, which converts AC power into DC power and stores energy through capacitors. Among them, D1, D2, D3, and D4 are rectifier diodes, C1 is a filter capacitor, the output end L2 of the AC input filter circuit is connected in parallel with the input end of the rectifier filter circuit N2, and then DC power is obtained through the rectifier bridge. The filter capacitor C1 filters the obtained DC power and then sends the electric energy to the DC power supply circuit. This circuit can output and store stable DC power, and supply power to the DC power supply circuit during normal AC voltage and voltage sag.

[0032] like Figure 5 As shown, the DC power supply circuit includes a step-down circuit (which steps down the DC power obtained from the rectifier and filter circuit), electronic switches K3 and K4, fuse FU2, and filter capacitors C2 and C3. The input filter capacitor C2 is connected in parallel with the output capacitor C1 of the rectifier and filter circuit, and the MOS tube Q1 is set to set the switching frequency so as to achieve that the output voltage of the DC power supply circuit meets the power supply requirements of the AC contactor coil. Q1 is connected to the diode D5 and the filter inductor L3 respectively. Q1, the diode D5, the inductor L3 and the capacitor C3 together form a buck step-down circuit. The electronic switches K3 and K4 are respectively connected in series to the line connected to the AC contactor coil. After the switch is closed, a stable DC power is provided to the contactor coil to ensure that the contactor continues to be attracted when the AC voltage temporarily drops. FU2 is connected in series to one end of the electronic switch K3 to achieve the overcurrent protection function of the DC power supply circuit.

[0033] like Figure 6 As shown in the figure, the microcontroller control circuit includes an ARM microcontroller STM32F103RB, a crystal oscillator Y, and crystal oscillator bypass capacitors C4 and C5. Among them, the crystal oscillator Y provides a basic clock signal for the circuit; the crystal oscillator bypass capacitors C4 and C5 are used to store charge. When the input signal source of the crystal oscillator is disturbed, the capacitor can provide a stable DC bias to help stabilize the frequency of the crystal oscillator. At the same time, the capacitor can also absorb transient energy in the circuit to prevent the noise in the circuit from interfering with the frequency of the crystal oscillator.

[0034] The AC voltage sampled from the AC power supply circuit is sent to the AN0 port of the single-chip microcomputer through the voltage divider filter circuit composed of resistors R1, R2 and capacitor C6. The DC voltage sampled from the DC power supply circuit is sent to the AN1 port of the single-chip microcomputer through the voltage divider filter circuit composed of R3, R4 and C7. DR1, DR2, DR3, and DR4 on the single-chip microcomputer are the drive signal ports of the electronic switches K1, K2, K3, and K4 respectively, and PWM1 is the drive signal port of the MOS tube Q1 on the DC power supply circuit.

[0035] like Figure 7 As shown, the switch driving circuit includes an isolation optocoupler, resistors R5, R6, a capacitor C8 and a voltage regulator VD1, which are used to receive driving signals from the single-chip control circuit DR1, DR2, DR3, DR4, and PWM1 (the DR1, DR2, DR3, DR4, and PWM1 ends are connected to different signal input interfaces of the driving circuit. Since the output signals of DR1, DR2, DR3, DR4, and PWM1 are small signals, a large signal will be obtained after being amplified by the isolation optocoupler, thereby driving the opening and closing of the electronic switches K1-K4 and the MOS tube Q1. Among them, R5 is a current limiting resistor, which is connected to the diode end of the isolation optocoupler, and a power supply VCC is added to the secondary side of the isolation optocoupler to provide a high voltage. The capacitor C8 is a filter capacitor, the resistor R6 is the driving resistor of the electronic switches K1-K4 and the MOS tube Q1, and the voltage regulator VD1 is used to limit the voltage spike of the driving voltage.

[0036] The voltage sag control device described in the present invention is connected between an AC power grid and an AC contactor coil. The AC power grid supplies power to the AC contactor coil through an AC power supply circuit, and the coil obtains stable AC power. At the same time, the AC input filter circuit also supplies power to the DC power supply circuit through a rectifier filter circuit to obtain stable DC power. Both the AC power supply circuit and the DC power supply circuit are connected to the AC contactor coil to provide stable AC power or DC power to the AC contactor coil.

[0037] After the single-chip microcomputer control circuit detects that the AC voltage of the AC power supply circuit is normal (according to the rated voltage regulations of the coils of different AC contactors, it is generally stipulated that the contactor should be reliably attracted when the pull-in voltage is greater than 85% of the rated voltage of the coil, which is normal at this time), the electronic switches K1 and K2 of the AC power supply circuit are controlled by the drive circuit to close, the AC contactor coil is energized, the contactor is attracted, and the contactor works normally. After the single-chip microcomputer control circuit detects that the DC voltage is normal, it controls the DC power supply circuit to work normally, but the electronic switches K3 and K4 of the DC power supply circuit are not closed at this time, and the DC power supply circuit is in hot standby state.

[0038] When a voltage sag occurs in the AC power grid, the single-chip control circuit quickly detects the AC voltage sag in the AC power supply circuit, and controls the electronic switches K1 and K2 of the AC power supply circuit through the drive circuit, and the electronic switches K3 and K4 of the DC power supply circuit are closed. The switching time in this process is less than 2ms, and the AC contactor coil (the electric energy is rectified and filtered, and then stepped down through the DC power supply circuit to power the AC contactor coil) obtains DC power, so that the contactor continues to stay closed and work normally.

[0039] When the single-chip control circuit detects that the AC voltage has returned to normal, the electronic switches K3 and K4 of the DC power supply circuit are disconnected through the drive circuit, and the electronic switches K1 and K2 of the AC power supply circuit are closed. The switching time is less than 2ms, and the AC contactor coil will continue to be attracted and work normally through the AC power supply. After the AC voltage returns to normal, the AC contactor continues to be powered by the AC power supply circuit, the rectifier filter capacitor continues to store energy normally, and the DC power supply circuit is in hot standby state, preparing for the next voltage sag event.

Claims

1. A voltage sag control device for an AC contactor, connected between an AC power grid and an AC contactor coil, characterized in that: The device comprises an AC power supply circuit connected to an AC power grid, an output end of the AC power supply circuit is connected to an AC contactor coil and an AC input filter circuit, an output end of the AC input filter circuit is connected to a rectifier filter circuit, and the AC power supply circuit provides AC power to the AC contactor coil or sends electric energy to the AC input filter circuit when a voltage drop occurs in the AC power; The rectifier filter circuit converts the AC power output by the AC input filter circuit into DC power and stores it. When the AC voltage temporarily drops, the DC power supply circuit provides DC power to the AC contactor coil.

2. The voltage sag control device for AC contactor according to claim 1 is characterized in that: The device also includes a single-chip microcomputer control circuit and a switch drive circuit. The input end of the single-chip microcomputer control circuit is connected to the AC power supply circuit and the DC power supply circuit, the output end of the single-chip microcomputer control circuit is connected to the switch drive circuit, and the output end of the switch drive circuit is connected to the AC power supply circuit and the DC power supply circuit. The single-chip microcomputer control circuit collects the AC voltage and the DC voltage input to the AC power supply circuit and the DC power supply circuit, and outputs a drive signal to the switch drive circuit for controlling the state of the AC power supply circuit and the DC power supply circuit.

3. The voltage sag control device for AC contactor according to claim 2 is characterized in that: The AC input filter circuit includes a common mode inductor L arranged at the live wire terminal L1 and the neutral wire terminal N1 of the AC power grid, capacitors CX1 and CX2 connected in parallel at both ends of the common mode inductor L, and a fuse FU1 connected in series at the live wire terminal L1.

4. The voltage sag control device for AC contactor according to claim 2 is characterized in that: The AC power supply circuit includes electronic switches K1 and K2 which are respectively connected in series to the AC output terminals L2 and N2 of the AC input filter circuit. The electronic switches K1 and K2 are controlled to open and close by driving signals output by the single chip control circuit.

5. The voltage sag control device for AC contactor according to claim 2, characterized in that: The rectifier and filter circuit includes a single-phase rectifier bridge and a filter capacitor C1, wherein the output terminals L2 and N2 of the AC input filter circuit are connected in parallel to a single-phase rectifier bridge circuit composed of rectifier diodes D1, D2, D3, and D4, and the filter capacitor C1 is connected in parallel to the single-phase rectifier bridge circuit to store direct current converted by the single-phase rectifier bridge.

6. The voltage sag control device for AC contactor according to claim 2, characterized in that: The DC power supply circuit includes a step-down circuit, electronic switches K3 and K4, a fuse FU2, and an input filter capacitor C2. The capacitor C2 is connected in parallel to the output capacitor C1 side of the rectifier filter circuit. The step-down circuit is composed of a MOS tube Q1, a diode D5, an inductor L3 and a capacitor C3. The electronic switches K3 and K4 are respectively connected in series at both ends of the AC contactor coil, and FU2 is connected in series to one end of the electronic switch K3.

7. The voltage sag control device for AC contactor according to claim 2, characterized in that: The single-chip control circuit includes an ARM single-chip computer STM32F103RB, a crystal oscillator Y, and capacitors C4 and C5 for storing charge in a crystal bypass. The collected AC voltage is sent to the AN0 port of the single-chip computer through a voltage-dividing filter circuit composed of resistors R1, R2 and capacitor C6. The collected DC voltage is sent to the AN1 port of the single-chip computer through a voltage-dividing filter circuit composed of R3, R4 and C7. DR1, DR2, DR3 and DR4 on the single-chip computer are respectively drive signal ports of electronic switches K1, K2, K3 and K4, and PWM1 is a drive signal port of a MOS tube Q1 on a DC power supply circuit.

8. The voltage sag control device for AC contactor according to claim 2, characterized in that: The switch driving circuit includes an isolation optocoupler, resistors R5, R6, a capacitor C8 and a voltage regulator VD1, wherein R5 is a current limiting resistor connected to the diode end of the isolation optocoupler, a power supply VCC is added to the secondary side of the isolation optocoupler to provide a high voltage, the capacitor C8 is a filter capacitor, the resistor R6 is a driving resistor of the electronic switches K1, K2, K3, K4 and the MOS tube Q1, and generates a driving voltage for the electronic switches K1, K2, K3, K4 and the MOS tube Q1, and the voltage regulator VD1 is used to limit the voltage spike of the driving voltage.

9. The voltage sag control device for AC contactor according to claim 2, characterized in that: The method for supplying power to the AC contactor coil by the device comprises: When the single-chip control circuit detects that the AC voltage of the AC power supply circuit is within the set requirement range, the AC power supply circuit provides AC power to the AC contactor coil, and the rectifier and filter circuit stores energy; When the single-chip control circuit detects that the AC voltage of the AC power supply circuit has a voltage drop, the rectifier filter circuit provides DC power to the AC contactor coil through the DC power supply circuit; When the voltage sag is restored, the AC power supply circuit is switched to provide AC power to the AC contactor coil, and the rectifier and filter circuit stores energy.

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