Power distribution network line ice melting device and method based on low-discreteness electromagnetic switch

Abstract

The invention provides a power distribution network line ice melting device and method based on a low-discreteness electromagnetic switch. The power distribution network line ice melting device is characterized in that the electromagnetic switch is used for controlling switch-in and switch-out of a capacitor bank in a power distribution line; the resistance-capacitance oscillation circuit is used for interacting with residual magnetism in an electromagnet in the electromagnetic switch body so as to generate oscillation current, and consuming the oscillation current so as to reduce the discreteness of closing of the electromagnetic switch; the super capacitor is used for discharging the magnet exciting coil so as to realize the closing or opening action of the electromagnetic switch; and the first control switch is used for switching-on control and switching-off control of the electromagnetic switch respectively. According to the control strategy, the first electromagnetic switch and the second electromagnetic switch are controlled to be switched on at the same time at the intersection point of A-phase and B-phase sinusoidal alternating currents, and the third electromagnetic switch is controlled to be switched on at the first zero crossing point of the C-phase. According to the invention, the inrush current-free input control of the capacitor bank is realized through the low-discreteness electromagnetic switch, and the effects of simple structure, small size, low cost, high reliability and capability of avoiding large closing current are achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of power line ice melting, and in particular to a distribution network line ice melting device and method based on a low-discreteness electromagnetic switch. Background Art

[0002] In recent years, due to the spread of extreme weather around the world, problems such as increased weight, sagging, and even breakage of power lines due to icing are more likely to occur in winter. It is necessary to melt the ice on the power lines to ensure the safe and stable operation of the power grid and avoid power outages.

[0003] At present, in the line de-icing technology, SVG de-icing uses static VAR compensator (SVG) to output controllable DC voltage to make the ice-covered line heat up and melt. Figure 1 In the SVG ice-melting line, the H-bridge three-phase inverter is connected in parallel with the system through the inductor L, and the magnitude and direction of the preset current are used as the closed-loop control conditions. The magnitude and phase of the inverter terminal voltage U1 are controlled by the pulse width modulation wave. The working state of SVG ice-melting includes: (1) When the inverter terminal voltage U1 and the system voltage U2 are equal, the current output of SVG is 0; when the inverter terminal voltage U1 is greater than the system voltage U2, SVG outputs capacitive reactive current; when the inverter terminal voltage U1 is less than the system voltage U2, SVG outputs inductive reactive current. It can be seen that the reactive current output by SVG increases the total current of the line, causing the line to heat up and thus achieve the effect of melting the ice on the line. However, the existing SVG type DC ice-melting device is mainly composed of power electronic devices, and its control structure is complex and expensive. The initial investment and maintenance costs are relatively high, so it is not suitable for full promotion; secondly, the existing SVG ice-melting equipment is large in size and occupies a large area, which is not conducive to deployment in remote mountainous areas where freezing rain and ice cover are common; in addition, due to the large number of power electronic devices, the long-distance transportation process may lead to reduced device reliability.

[0004] See also Figure 2 If a relatively simple and low-cost reactive compensation device FC is used to melt ice on the line, it is only necessary to control the capacitor C and the reactor L to be connected in parallel to the system through the circuit breaker QF to generate capacitive reactive current, so as to increase the total current of the line and achieve the effect of melting ice through line heating. However, further analysis: According to the capacitor charging current formula:

[0005]

[0006] Where I is the peak value of the capacitor current, C is the capacitance of the capacitor, dU is the difference between the system voltage and the initial voltage of the capacitor when the switch is closed, and dt is the time required for the capacitor to reach the system voltage from the initial voltage.

[0007] From the above formula, it can be seen that if the initial closing phase angle of the circuit breaker QF is at the peak value of the voltage, it will cause a huge closing inrush current. At the end of the distribution network, since the overcurrent setting of the relay protection is usually small, if a large-capacity capacitor is suddenly put into use, it may cause the relay protection to malfunction and cut off the line. In addition, the sudden large closing inrush current will also cause a voltage drop on the user side of the transmission line, which may damage the normally working power equipment and electronic equipment, resulting in serious economic losses.

[0008] Therefore, it is necessary to design a distribution network line de-icing device and method which has a simple structure, small size, low cost, high reliability and can avoid large closing current. Summary of the invention

[0009] The present invention provides a distribution network line ice melting device and method based on a low-discreteness electromagnetic switch, which is mainly used to solve the problems of the existing ice melting equipment, such as complex structure, high cost, poor reliability, and large closing current when connected to the line, so as to achieve the effect of simple structure, small size, low cost, high reliability and avoidance of large closing current.

[0010] The present invention achieves the above-mentioned purpose through the following technical solutions:

[0011] A distribution network line ice melting device based on low discreteness electromagnetic switches, comprising a first electromagnetic switch, a second electromagnetic switch, a third electromagnetic switch and three groups of capacitor groups, wherein the three groups of capacitor groups are respectively connected to the A phase, the B phase and the C phase of the distribution line through the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch; the above-mentioned electromagnetic switches all include an electromagnetic switch body and an electromagnetic control circuit, which are respectively used to control the switching in and out of each of the capacitor groups in the distribution line; the electromagnetic control circuit includes a resistor-capacitor oscillation circuit, a super capacitor and a control circuit, wherein the resistor-capacitor oscillation circuit is used to interact with the residual magnetism in the electromagnet in the electromagnetic switch body to generate an oscillating current, and consume the oscillating current to reduce the discreteness of the electromagnetic switch closing; the super capacitor is connected in parallel with the excitation coil of the electromagnet through the control circuit, and is used to discharge the excitation coil to realize the closing or opening action of the electromagnetic switch; the control circuit includes a first control switch and a second control switch, wherein the two ends of the super capacitor are respectively connected to the excitation coil through the first control switch and the second control switch, and the first control switch and the second control switch are respectively used for the closing control and the opening control of the electromagnetic switch.

[0012] Among them, the control strategy of the first control switch in the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch is: at the intersection of the A-phase and B-phase sinusoidal alternating currents, the first electromagnetic switch and the second electromagnetic switch are controlled to be closed at the same time, and at the first zero crossing point of the C-phase thereafter, the third electromagnetic switch is controlled to be closed to achieve inrush-free closing control.

[0013] A further solution is that the electromagnetic control circuit also includes a DC-DC boost circuit, the input end of the DC-DC boost circuit is connected to the battery output end in the switch cabinet, for inputting 48V DC power and converting the 48V DC power into 690V DC power and outputting it to the supercapacitor.

[0014] A further solution is that the DC-DC boost circuit charges the supercapacitor in a floating charge manner.

[0015] A further solution is that the DC-DC boost circuit adopts an isolated boost circuit, and its output voltage accuracy is 0.1%.

[0016] A further solution is that the RC oscillation circuit includes a relay, a resistor and a capacitor, one end of the resistor is connected to the first output end of the DC-DC boost circuit through the normally open contact of the relay, and the other end is connected to the second output end of the DC-DC boost circuit through the capacitor.

[0017] After the electromagnetic switch is opened, the relay is used to connect to the RC oscillation circuit by controlling its normally open contact to close, the capacitor is used to exchange energy with the residual magnetism in the electromagnet to generate the oscillating current, and the resistor is used to convert the oscillating current flowing through it into heat energy for consumption, thereby eliminating the residual magnetism in the electromagnet and reducing the discreteness of the closing of the electromagnetic switch.

[0018] A further solution is that both the first control switch and the second control switch use IGBT transistors, whose gates are respectively connected to the first control signal and the second control signal, and the first control switch controls the transistor to turn on according to the first control signal to achieve the closing of the electromagnetic switch; the second control switch controls the transistor to turn on according to the second control signal to achieve the opening of the electromagnetic switch.

[0019] A further solution is that the inherent closing time of the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch are A and B, respectively. S , B S , C S , the first closing signal and the second closing signal of the first electromagnetic switch and the second electromagnetic switch are respectively advanced by A S , B SThe third closing signal of the third electromagnetic switch is issued in advance by C S The time is issued, so that when the circuit breaker is closed, the phase voltage between phase C and phase B satisfies: V cb =V c -V b =0.5*V ab .

[0020] A method for melting ice in a distribution network line based on a low-discrete electromagnetic switch, applied to a distribution network line melting ice device based on a low-discrete electromagnetic switch, comprising:

[0021] S1: Detect the inherent closing time A of the first electromagnetic switch, the second electromagnetic switch, and the third electromagnetic switch respectively S , B S , C S .

[0022] S2: Start the ice-melting operation and detect the three-phase sinusoidal alternating current in the distribution line.

[0023] S3: At the next intersection of the A-phase and B-phase sinusoidal alternating currents, advance A S , B S The first closing signal and the second closing signal are sent to the first electromagnetic switch and the second electromagnetic switch at the same time.

[0024] S4: Advance C at the next zero crossing point of the C phase sinusoidal alternating current S The third closing signal is sent out at this time.

[0025] S5: The first electromagnetic switch and the second electromagnetic switch are closed at the intersection, and the A phase and the B phase are respectively connected to the capacitor bank. The third electromagnetic switch is closed at the zero crossing point, and the C phase is connected to the capacitor bank.

[0026] S6: The above three capacitor groups send capacitive reactive current to the line, causing the line to heat up and melt ice.

[0027] It can be seen that the present invention has the following beneficial effects:

[0028] 1. The present invention uses a resistor-capacitor oscillation circuit to return the residual magnetism of the iron core to zero after each electromagnetic switch is opened, thereby minimizing the discreteness of the speed of each closing action of the switch. Compared with the traditional reactive power compensation device FC using a circuit breaker or the existing electromagnetic switch, the present invention avoids the problem of too many transmission links leading to energy loss and the influence of the mechanism movement speed leading to large discreteness. And by utilizing the accuracy of the electromagnetic switch with low opening and closing discreteness, the capacitor bank is switched in phase at the favorable initial phase angle of the equipotential, and the control of the capacitor bank without inrush current is realized, thereby completely avoiding the problem of false operation of the relay protection and the voltage drop on the user side caused by the large closing inrush current.

[0029] 2. The present invention adopts a low-opening and closing discrete electromagnetic switch to realize phase-by-phase switching of the capacitor group, thereby performing ice-melting operations. Compared with the traditional SVG ice-melting solution with complex equipment structure, high cost and poor reliability, the ice-melting device of this solution has a simple structure, small size and low cost, and the circuit design is relatively simple, which improves the reliability of the device and can realize the popularization of distribution network line ice-melting devices in different application environments.

[0030] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of the prior art SVG ice melting solution.

[0032] Figure 2 It is a schematic diagram of the FC ice melting scheme of the reactive power compensation device in the prior art.

[0033] Figure 3 It is a schematic diagram of an existing electromagnetic switch circuit.

[0034] Figure 4 This is a schematic diagram of the relationship between the magnetic field strength and switching speed of the electromagnetic switch.

[0035] Figure 5 The electromagnetic switch circuit of the embodiment of the present invention is schematically shown in FIG. Figure 1 .

[0036] Figure 6 The electromagnetic switch circuit of the embodiment of the present invention is schematically shown in FIG. Figure 2 .

[0037] Figure 7 It is a flow chart of a method for melting ice in a distribution network line based on a low-discreteness electromagnetic switch according to an embodiment of the present invention. DETAILED DESCRIPTION

[0038] In order to make the purpose, technical solution and advantages of the embodiment of the present invention clearer, the technical solution of the embodiment of the present invention will be clearly and completely described below in conjunction with the drawings of the embodiment of the present invention. Obviously, the described embodiment is a part of the embodiment of the present invention, not all of the embodiments. Based on the described embodiment of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0039] An embodiment of a distribution network line de-icing device based on a low discreteness electromagnetic switch

[0040] The present invention relates to a distribution network line de-icing device based on a low-discreteness electromagnetic switch, comprising a first electromagnetic switch, a second electromagnetic switch, a third electromagnetic switch and three groups of capacitor groups, wherein the three groups of capacitor groups are respectively connected to the A phase, the B phase and the C phase of the distribution line through the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch; the above-mentioned electromagnetic switches all include an electromagnetic switch body and an electromagnetic control circuit 40, which are respectively used to control the switching in and out of each of the capacitor groups in the distribution line; the electromagnetic control circuit 40 includes a resistor-capacitor oscillation circuit 20, a super capacitor 30 and a control circuit 40, and the resistor-capacitor oscillation circuit 20 is used to It interacts with the residual magnetism in the electromagnet in the electromagnetic switch body to generate an oscillating current, and consumes the oscillating current to reduce the discreteness of the closing of the electromagnetic switch; the supercapacitor 30 is connected in parallel with the excitation coil 50 of the electromagnet through the control circuit 40, and is used to discharge the excitation coil 50 to achieve the closing or opening action of the electromagnetic switch; the control circuit 40 includes a first control switch and a second control switch, and the two ends of the supercapacitor 30 are connected to the excitation coil 50 through the first control switch and the second control switch respectively, and the first control switch and the second control switch are used for the closing control and opening control of the electromagnetic switch respectively.

[0041] Among them, the control strategy of the first control switch in the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch is: at the intersection of the A-phase and B-phase sinusoidal alternating currents, the first electromagnetic switch and the second electromagnetic switch are controlled to be closed at the same time, and at the first zero crossing point of the C-phase thereafter, the third electromagnetic switch is controlled to be closed to achieve inrush-free closing control.

[0042] Specifically, the electromagnetic switch body described in this embodiment includes a switch body, an electromagnet, a spring mechanism and a contact. The switch body includes a static contact, a moving contact and an insulating base, etc., which are used to perform opening and closing actions. The electromagnet includes an iron core, a coil and a moving iron sheet, etc., which are used to control the action of the switch body through the electromagnetic control circuit 40. The spring mechanism is used to control the closing and disengagement of the moving contact when the electromagnet is attracted. The contact is placed in the switch body and is used to control the switch as a conductive contact. The working process of the electromagnetic switch body is as follows: after the electromagnet is excited by the current output by the electromagnetic control circuit 40, a magnetic field is generated, and the magnetic field acts on the iron core to press the moving contact toward the static contact, so that the circuit is closed and the electromagnetic switch is closed; when the circuit current exceeds the set value, the contact iron sheet is displaced, so that the moving contact is opened, the circuit is disconnected, and the electromagnetic switch is opened.

[0043] Wherein, the iron core is made of semi-hard magnetic material, such as cobalt-nickel-iron alloy.

[0044] Specifically, when the electromagnetic switch of this embodiment is closed, the super capacitor 30 discharges the excitation coil 50 of the electromagnetic switch, and its magnetic core generates magnetic flux, overcoming the elastic force of the spring to close the switch. At this time, the iron core made of semi-hard magnetic material becomes a permanent magnet after one excitation. When the electromagnetic switch is opened, the super capacitor 30 discharges the excitation coil 50 of the electromagnetic switch, and its magnetic core is demagnetized, and the opening is achieved by relying on the elastic force of the spring.

[0045] Specifically, the factors affecting the switch action speed in this embodiment include the excitation voltage, the residual magnetism of the semi-hard magnetic material and the mechanical elastic force of the spring. Among them, the discreteness of the spring elastic force is extremely small and can be ignored. The accuracy of the excitation voltage is guaranteed by the DC / DC boost circuit. The oscillation demagnetization circuit ensures that the residual magnetism of the semi-hard magnetic material returns to zero after each opening, thereby minimizing the discreteness of the switch closing action speed each time.

[0046] In this embodiment, the electromagnetic control circuit 40 also includes a DC-DC boost circuit 10, the input end of the DC-DC boost circuit 10 is connected to the battery output end in the switch cabinet, and is used to input 48V DC power and convert the 48V DC power into 690V DC power and output it to the supercapacitor 30.

[0047] In this embodiment, the DC-DC boost circuit 10 charges the super capacitor 30 in a floating charge manner.

[0048] Specifically, the DC-DC boost circuit 10 of this embodiment serves as a charging device for the supercapacitor 30 on the line, and is used to ensure the accuracy of the voltage output to the excitation coil 50. The supercapacitor 30 can be charged and discharged as the voltage of the power line fluctuates. When the capacity of the capacitor group is small and the voltage of the power line is high, the supercapacitor 30 is charged; when the capacity of the capacitor group is large or the power supply is unexpectedly interrupted, the supercapacitor 30 is discharged to share part or all of the output. It can be seen that the voltage of the supercapacitor 30 in the floating charge state is generally constant, and the small amount of current provided by the DC-DC boost circuit 10 from the power line compensates for the loss of the local action of the supercapacitor 30, so that it can always be kept in a fully charged state without being overcharged.

[0049] In this embodiment, the DC-DC boost circuit 10 adopts an isolated boost circuit, and its output voltage accuracy is 0.1%.

[0050] It can be seen that the error between the actual value and the theoretical value of the output voltage of the DC-DC boost circuit 10 does not exceed 0.1% of the actual measured value, that is, when outputting 690V DC, the maximum difference between the actual voltage value and the theoretical value is 0.69V.

[0051] Specifically, the DC-DC boost circuit 10 of this embodiment adopts a bridge conversion circuit, including a PWM pulse generating circuit, a full-bridge driving circuit, a transformer and a synchronous rectification circuit. The PWM pulse generating circuit is used to generate 8 groups of PWM pulses to the gate of each MOS tube respectively, and the full-bridge driving circuit includes 4 MOS tubes constituting a full bridge, which are respectively composed of two half bridges, and the two switch nodes of the half bridge are respectively connected to the two ends of the primary side of the transformer. The synchronous rectification circuit uses 4 synchronous rectification MOS tubes constituting a full bridge. The two ends of the secondary side of the transformer are respectively connected to the synchronous rectification MOS tube. The purpose of controlling and adjusting the output voltage is achieved by adjusting the duty cycle of the primary full-bridge MOS tube.

[0052] See also Figure 6 , Q1 and Q4 are turned on at the same time as a group of diagonal MOS tubes, and Q2 and Q3 are turned on at the same time as another group of diagonal MOS tubes. VPRI is the primary voltage of the transformer, IPRI is the current of the primary side of the transformer, Q5 and Q8, Q6 and Q7 are used for secondary synchronous rectification.

[0053] Specifically, this embodiment refers to Figure 3 For existing electromagnetic switches, since the material of the finished product is fixed, the influence of the material on the switching speed can be ignored. The factors that actually affect the switching speed are the excitation voltage and the residual magnetism of the core. According to the PWM pulse width modulation control theory, the conduction duty cycle of the IGBT in the DC / DC boost circuit is positively correlated with its output voltage, so that a constant excitation voltage can be obtained. Figure 4 , when the residual magnetism in the iron core is zero, the magnetic field strength H2 obtained by the constant excitation voltage corresponds to the switching speed S1. When the residual magnetism is H1, the magnetic field strength of the switch after applying the constant excitation voltage is H3, and the corresponding switching speed is S2. In actual applications, since the residual magnetism is greatly affected by time and environment, H1 is a variable and its value is unknown, and the switching speed S2 of the electromagnetic switch cannot be determined, the existing electromagnetic switch opening and closing actions are relatively discrete.

[0054] See also Figure 5 In this embodiment, the RC oscillation circuit 20 includes a relay, a resistor and a capacitor, one end of the resistor is connected to the first output end of the DC-DC boost circuit 10 through the normally open contact of the relay, and the other end of the resistor is connected to the second output end of the DC-DC boost circuit 10 through the capacitor.

[0055] After the electromagnetic switch is opened, the relay is used to connect to the RC oscillation circuit 20 by controlling its normally open contact to close, the capacitor is used to exchange energy with the residual magnetism in the electromagnet to generate the oscillating current, and the resistor is used to convert the oscillating current flowing through into heat energy for consumption, thereby eliminating the residual magnetism in the electromagnet and reducing the discreteness of the closing of the electromagnetic switch.

[0056] In this embodiment, both the first control switch and the second control switch use IGBT transistors, whose gates are respectively connected to the first control signal and the second control signal. The first control switch controls the transistor to turn on according to the first control signal to close the electromagnetic switch; the second control switch controls the transistor to turn on according to the second control signal to open the electromagnetic switch.

[0057] In this embodiment, the inherent closing time of the first electromagnetic switch, the second electromagnetic switch, and the third electromagnetic switch are A and B, respectively. S , B S , C S , the first closing signal and the second closing signal of the first electromagnetic switch and the second electromagnetic switch are respectively advanced by A S , B S The third closing signal of the third electromagnetic switch is issued in advance by C S The time is issued, so that when the circuit breaker is closed, the phase voltage between phase C and phase B satisfies: V cb =V c -V b =0.5*V ab .

[0058] A method for melting ice in a distribution network line based on a low-discreteness electromagnetic switch

[0059] See also Figure 7 The present invention relates to a method for melting ice in a distribution network line based on a low-discrete electromagnetic switch, which is applied to a device for melting ice in a distribution network line based on a low-discrete electromagnetic switch, and comprises:

[0060] S1: Detect the inherent closing time A of the first electromagnetic switch, the second electromagnetic switch, and the third electromagnetic switch respectively S , B S , C S .

[0061] S2: Start the ice-melting operation and detect the three-phase sinusoidal alternating current in the distribution line.

[0062] S3: At the next intersection of the A-phase and B-phase sinusoidal alternating currents, advance A S , B SThe first closing signal and the second closing signal are sent to the first electromagnetic switch and the second electromagnetic switch at the same time.

[0063] S4: Advance C at the next zero crossing point of the C phase sinusoidal alternating current S The third closing signal is sent out at this time.

[0064] S5: The first electromagnetic switch and the second electromagnetic switch are closed at the intersection, and the A phase and the B phase are respectively connected to the capacitor bank. The third electromagnetic switch is closed at the zero crossing point, and the C phase is connected to the capacitor bank.

[0065] S6: The above three capacitor groups send capacitive reactive current to the line, causing the line to heat up and melt ice.

[0066] The above-mentioned embodiments are only preferred embodiments of the present invention and cannot be used to limit the scope of protection of the present invention. Any non-substantial changes and substitutions made by technicians in this field on the basis of the present invention shall fall within the scope of protection required by the present invention.

Claims

1. A distribution network line de-icing device based on a low discreteness electromagnetic switch, characterized in that: include: A first electromagnetic switch, a second electromagnetic switch, a third electromagnetic switch and three groups of capacitors, the three groups of capacitors are connected to the A phase, B phase and C phase of the distribution line through the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch respectively; the above electromagnetic switches all include an electromagnetic switch body and an electromagnetic control circuit, which are respectively used to control the switching in and out of each of the capacitor groups in the distribution line; the electromagnetic control circuit includes a resistor-capacitor oscillation circuit, a super capacitor and a control circuit, the resistor-capacitor oscillation circuit is used to interact with the residual magnetism in the electromagnet in the electromagnetic switch body to generate an oscillating current, and consume the oscillating current to reduce the discreteness of the closing of the electromagnetic switch; the super capacitor is connected in parallel with the excitation coil of the electromagnet through the control circuit, and is used to discharge the excitation coil to realize the closing or opening action of the electromagnetic switch; the control circuit includes a first control switch and a second control switch, the two ends of the super capacitor are connected to the excitation coil through the first control switch and the second control switch respectively, and the first control switch and the first control switch are used for the closing control and the opening control of the electromagnetic switch respectively; Among them, the control strategy of the first control switch in the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch is: at the intersection of the A-phase and B-phase sinusoidal alternating currents, the first electromagnetic switch and the second electromagnetic switch are controlled to be closed at the same time, and at the first zero crossing point of the C-phase thereafter, the third electromagnetic switch is controlled to be closed to achieve inrush-free closing control.

2. The distribution network line de-icing device based on low discreteness electromagnetic switch according to claim 1 is characterized in that: The electromagnetic control circuit also includes a DC-DC boost circuit, the input end of which is connected to the battery output end in the switch cabinet, for inputting 48V DC power and converting the 48V DC power into 690V DC power and outputting it to the supercapacitor.

3. The distribution network line ice melting device based on low discreteness electromagnetic switch according to claim 2 is characterized in that: The DC-DC boost circuit charges the supercapacitor in a floating charge manner.

4. The distribution network line ice melting device based on low discreteness electromagnetic switch according to claim 3 is characterized in that: The DC-DC boost circuit adopts an isolated boost circuit, and its output voltage accuracy is 0.1%.

5. The distribution network line ice melting device based on low discreteness electromagnetic switch according to claim 3 is characterized in that: The RC oscillation circuit comprises a relay, a resistor and a capacitor, one end of the resistor is connected to the first output end of the DC-DC boost circuit through the normally open contact of the relay, and the other end of the resistor is connected to the second output end of the DC-DC boost circuit through the capacitor; After the electromagnetic switch is opened, the relay is used to connect to the RC oscillation circuit by controlling its normally open contact to close, the capacitor is used to exchange energy with the residual magnetism in the electromagnet to generate the oscillating current, and the resistor is used to convert the oscillating current flowing through it into heat energy for consumption, thereby eliminating the residual magnetism in the electromagnet and reducing the discreteness of the closing of the electromagnetic switch.

6. The distribution network line de-icing device based on low discreteness electromagnetic switch according to claim 1 is characterized in that: The first control switch and the second control switch both use IGBT transistors, whose gates are respectively connected to the first control signal and the second control signal. The first control switch controls the transistor to turn on according to the first control signal to close the electromagnetic switch; the second control switch controls the transistor to turn on according to the second control signal to open the electromagnetic switch.

7. The distribution network line de-icing device based on low discreteness electromagnetic switch according to any one of claims 1 to 6, characterized in that: The inherent closing time of the first electromagnetic switch, the second electromagnetic switch and the third electromagnetic switch are A S , B S , C S , the first closing signal and the second closing signal of the first electromagnetic switch and the second electromagnetic switch are respectively advanced by A S , B S The third closing signal of the third electromagnetic switch is issued in advance by C S The time is issued, so that when the circuit breaker is closed, the phase voltage between phase C and phase B satisfies: V cb =V c -V b =0.5*V ab .

8. A method for melting ice in a distribution network line based on a low discreteness electromagnetic switch, characterized in that: A distribution network line de-icing device based on a low-discreteness electromagnetic switch as claimed in any one of claims 1 to 7, comprising: S1: Detect the inherent closing time A of the first electromagnetic switch, the second electromagnetic switch, and the third electromagnetic switch respectively S , B S , C S ; S2: Start the ice melting operation and detect the three-phase sinusoidal AC power in the distribution line; S3: At the next intersection of the A-phase and B-phase sinusoidal alternating currents, advance A S , B S Sending a first closing signal and a second closing signal to the first electromagnetic switch and the second electromagnetic switch at the same time; S4: Advance C at the next zero crossing point of the C phase sinusoidal alternating current S Time to send out the third closing signal; S5: the first electromagnetic switch and the second electromagnetic switch are closed at the intersection, and the A phase and the B phase are respectively connected to the capacitor bank, and the third electromagnetic switch is closed at the zero crossing point, and the C phase is connected to the capacitor bank; S6: The above three capacitor groups send capacitive reactive current to the line, causing the line to heat up and melt ice.

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