System and method for judging whether the secondary voltage switch is closed or open based on wireless power transmission

Abstract

The present invention discloses a system and method for judging whether a knife switch is in place based on a secondary voltage of wireless power transmission, including an AC power supply, a rectifier inverter circuit, a transmitting coil, a pickup coil, an A / D sampling module, and a comparison module. During the opening and closing process of the knife switch, the change in mutual inductance between the pickup coil and the transmitting coil will cause the secondary voltage to change. Therefore, the opening and closing state of the knife switch can be judged by detecting the secondary voltage. Based on the principle of wireless power transmission, the pickup coil receives the electric energy sent by the transmitting coil and generates a secondary voltage. The secondary voltage is converted into a digital signal by the A / D sampling module and enters the comparison module to judge whether the secondary voltage value reaches the fully closed voltage U ref , and obtain the final closing judgment result, thereby realizing high-precision and low-cost monitoring of the knife switch opening and closing positions.

Description

Technical Field

[0001] The invention relates to the field of substation automation control, and in particular to a switch closing reliability judgment method based on secondary side voltage identification of a wireless power transmission system. Background Art

[0002] The knife switch equipment is a very important equipment in the substation. When the substation performs switching operations, due to the looseness of some mechanical components on the knife switch side of the primary equipment or the failure of the secondary circuit limit switch, it may cause misoperation accidents, affecting the safety and reliability of the system power supply, thereby affecting the normal production of society and causing losses to the national economy.

[0003] With the development of smart grids, it is necessary to grasp the operating status of the disconnector in real time, avoid major accidents caused by misoperation in time, and improve the reliability of grid operation. The substation operation specifications require that the knife switch be detected by a non-same principle or non-homologous method. Only when both non-homologous detection signals change can the knife switch be determined to be in place. At present, the first criterion for the knife switch closing position is mainly obtained through the mechanism auxiliary switch node, but the node may slip and deform after long-term operation, resulting in inaccurate detection of the knife switch position. At present, the second criterion for the knife switch closing position is mainly through three methods: manual on-site confirmation, image recognition, and installation of posture sensors.

[0004] Manual on-site confirmation means that substation personnel go to the site to directly observe the opening and closing status of the knife switch to confirm whether the knife switch is in place. This method is time-consuming and laborious, with low operating efficiency. At the same time, there are many human factors and it is not in line with the development of smart grids.

[0005] Image recognition is to use a camera to capture the opening and closing state of the knife switch, and then use the captured state photos to identify the state through image analysis software to complete the judgment of the opening and closing state of the knife switch. This method requires the installation of more cameras, which is costly. At the same time, the photos taken by the camera are greatly affected by environmental factors. In environments such as insufficient light or rain and fog, the photos taken are not clear, which can easily lead to inability to judge or wrong judgment, and it is difficult to automatically judge the reliability of the opening and closing of the knife switch.

[0006] The attitude sensor is installed on the knife switch and rotates with the knife switch to form the position or angle offset information of the process from opening to closing. The rotation angle and change of the sensor are calculated by the algorithm to judge whether the disconnector is in place. However, the attitude sensor cable rotates with the mechanism and is easily entangled on the mechanism connecting rod, resulting in data drift and poor application effect. Summary of the invention

[0007] Purpose of the invention: In order to overcome the deficiencies in the prior art, the present invention provides a system and method for determining whether a secondary voltage knife switch is in position based on wireless power transmission, which realizes automatic determination of the reliability of the knife switch in closing position with high precision and low cost.

[0008] Technical solution: To achieve the above purpose, the technical solution adopted by the present invention is:

[0009] A system for judging whether the secondary voltage switch is closed or open based on wireless power transmission includes an AC power supply, a rectifier inverter circuit, a transmitting coil, a pickup coil, an A / D sampling module, and a comparison module, wherein:

[0010] The AC power supply, the rectifier inverter circuit, and the transmitting coil are connected in sequence; the transmitting coil is installed on the low-voltage side of the switch base; the pickup coil, the A / D sampling module, and the comparison module are connected in sequence, and the pickup coil is installed on the high-voltage side of the switch contact;

[0011] The AC power supply provides power, the rectifier inverter circuit outputs high-frequency square waves, and the high-frequency square wave power supply transmits wireless energy through the transmitting coil;

[0012] The pickup coil receives the electric energy sent by the transmitting coil and generates a secondary voltage; the secondary voltage is converted into a digital signal by the A / D sampling module and enters the comparison module to determine whether the secondary voltage value reaches the fully closed voltage U ref , and obtain the final closing judgment result.

[0013] Preferably: the comparison module is provided with the following comparison and discrimination circuit:

[0014]

[0015] Among them, U ref Indicates the fully closed voltage, fully closed voltage U ref Refers to the voltage when the secondary voltage of the pickup coil is maximum when the knife switch is closed.

[0016] Preferably: comprising an LCCL topology, the LCCL topology being arranged between the rectifier inverter circuit and the transmitting coil, the LCCL topology being used to compensate for the reflected impedance of the primary side of the system when the knife switch is in different positions to ensure the safety of the system.

[0017] Preferably: a capacitance compensation circuit is included, the capacitance compensation circuit is arranged between the pickup coil and the A / D sampling module, and the capacitance compensation circuit compensates for the secondary side voltage.

[0018] Preferably, it comprises a wifi signal transmitting module, a wifi signal receiving module and a display module, wherein the display module is connected to the AC power supply and the wifi signal receiving module respectively, and the wifi signal receiving module is connected to the transmitting coil. The comparison module is connected to the wifi signal transmitting module. The wifi signal receiving module is used to receive the closing judgment result signal of the high-voltage side of the knife switch sent by the wifi signal transmitting module, and display it through the display module.

[0019] Preferably, the rectifier inverter circuit is a full-bridge inverter circuit composed of four switching tubes.

[0020] Preferably: the power supply of the A / D sampling module, the comparison module and the WiFi signal transmitting module is provided by a pickup coil.

[0021] A method for judging whether the knife switch is in place based on the secondary voltage of wireless power transmission. The change of mutual inductance between the pick-up coil and the transmitting coil during the knife switch opening and closing process will cause the secondary voltage to change. Therefore, the opening and closing state of the knife switch is judged by detecting the secondary voltage. Based on the principle of wireless power transmission, the electric energy is transmitted by the transmitting coil and received by the pick-up coil. The secondary voltage of the pick-up coil is compared after A / D sampling. The secondary voltage reaches the fully closed voltage U ref Indicates that the knife switch is fully closed. The secondary voltage has not reached the fully closed voltage U ref Indicates that the knife switch is open.

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] (1) This solution does not require personnel to go directly to the site to conduct status inspections, which greatly reduces the labor intensity of operators, shortens operation time, and improves operating efficiency and safety levels.

[0024] (2) This solution has high detection accuracy and low cost. It can achieve high-precision detection of the knife switch closing position at a relatively low cost and has high practicality.

[0025] (3) This solution adopts the principle of wireless power transmission. Energy transmission can power the secondary side, and no external power supply is required on the switch side, simplifying the system structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of the installation of the reliability judgment method of the secondary voltage switch closing position based on the wireless power transmission system;

[0027] Figure 2 It is a schematic diagram of the reliability judgment method of the secondary voltage switch closing position based on the wireless power transmission system;

[0028] Figure 3 It is a flow chart of the reliability judgment method of the secondary voltage switch closing position based on the wireless power transmission system;

[0029] Figure 4 It is the equivalent circuit diagram of the reliability judgment method of the secondary voltage knife closing position based on the wireless power transmission system. DETAILED DESCRIPTION

[0030] The present invention is further explained below in conjunction with the accompanying drawings and specific embodiments. It should be understood that these examples are only used to illustrate the present invention and are not used to limit the scope of the present invention. After reading the present invention, various equivalent forms of modifications to the present invention by those skilled in the art all fall within the scope defined by the claims attached to this application.

[0031] A system for judging whether the secondary voltage switch is closed or open based on wireless power transmission, such as Figure 1 As shown, it includes an AC power supply 1, a rectifier inverter circuit 2, an LCCL topology 3, a transmitting coil 4, a pickup coil 5, a compensation comparison circuit 6, an A / D sampling module 7, a comparison module 8, a wifi signal transmitting module 9, a wifi signal receiving module 10, and a display module 11, wherein:

[0032] The AC power supply 1, the rectifier inverter circuit 2, and the transmitting coil 4 are connected in sequence, and the display module 11 is connected to the AC power supply 1 and the wifi signal receiving module 10 respectively, and the wifi signal receiving module 10 is connected to the transmitting coil 4. The AC power supply 1, the rectifier inverter circuit 2, the transmitting coil 4, the wifi signal receiving module 10, and the display module 11 are installed on the low-voltage side of the switch base. The pickup coil 5, the capacitance compensation circuit 6, the A / D sampling module 7, the comparison module 8, and the wifi signal transmitting module 9 are connected in sequence, and the pickup coil 5, the capacitance compensation circuit 6, and the wifi signal transmitting module 9 are installed on the switch on the high-voltage side of the switch contact. The LCCL topology 3 is arranged between the rectifier inverter circuit 2 and the transmitting coil 4, and the LCCL topology 3 is used to compensate for the reflected impedance of the primary side of the system when the switch is in different positions to ensure system safety.

[0033] The AC power supply 1 provides power, and the rectifier inverter circuit 2 outputs a high-frequency square wave power supply, which transmits wireless energy through the transmitting coil 4. The magnetic energy transmitting coil and control device are installed directly below the knife switch on the low-voltage side of the base, including an AC power supply, an AC / DC conversion link, a high-frequency inverter circuit, a primary compensation capacitor, an inductor, and a primary coil; wherein, the AC / DC conversion converts the AC power supply into DC power; the high-frequency inverter circuit converts the DC power into high-frequency AC power; the primary compensation capacitor, the inductor, and the primary coil constitute an energy transmission channel.

[0034] The pickup coil 5 receives the electric energy sent by the transmitting coil 4 and generates a secondary voltage. The compensation capacitor in the capacitor compensation circuit 6 compensates the secondary voltage, and the output voltage is converted into a digital signal by the A / D sampling module 7, and enters the comparison module to determine whether the secondary voltage value reaches the fully closed voltage U ref The final closing judgment result is sent out through the WiFi signal transmitting module 9.

[0035] The passive pickup coil and detection accessories are installed on the primary equipment knife switch, including the secondary coil, secondary compensation capacitor, rectifier circuit, DC / DC conversion link, load and detection accessories; among them, the secondary coil generates an induced voltage by coupling with the primary coil; the secondary compensation capacitor and the secondary coil form an electric energy transmission channel; the rectifier circuit converts AC power into DC power; the DC / DC conversion converts the rectified DC power into the DC voltage required for the accessory to work; the load and the detection accessories constitute the knife switch status collection and transmission device.

[0036] like Figure 2 As shown in the figure, the wireless power transmission principle is used to identify the secondary voltage to realize the reliability judgment of the knife switch closing position. The wireless power transmission system includes a primary circuit and a secondary circuit. The primary circuit includes an AC power supply, an AC / DC rectifier link, a high-frequency inverter circuit, and a primary compensation capacitor C. p , C f , compensation inductance L f , primary coil L p Among them, AC / DC conversion converts AC power into DC power; high-frequency inverter circuit converts DC power into high-frequency AC power; primary compensation capacitor C p , C f , compensation inductance L f and the primary coil L p Form an electric energy transmission channel.

[0037] The secondary circuit includes the secondary coil L s , secondary compensation capacitor C s , rectifier circuit, DC / DC conversion link, load R L And detection accessories, the detection part includes A / D sampling module, single chip voltage identification module, wifi signal sending module. Among them, the secondary coil generates an induced voltage by coupling with the primary coil; the secondary compensation capacitor C s With the secondary coil L s The power transmission channel is formed; the rectifier circuit converts AC power into DC power; the DC / DC converter converts the rectified DC power into the DC voltage required for the accessory to work; the load R L And the detection accessories constitute the knife switch status collection and sending device.

[0038] Primary compensation capacitor C p , Cf , compensation inductance L f , primary coil L p , secondary coil L s , secondary compensation capacitor C s satisfy:

[0039]

[0040] Wherein, f is the operating frequency of the high-frequency inverter.

[0041] The wifi signal receiving module 8 is used to receive the closing judgment result signal of the high-voltage side of the knife switch sent by the wifi signal transmitting module 7, and display it through the display module 9. The voltage comparison judgment and signal transmission are controlled by the single chip microcomputer.

[0042] The rectifier inverter circuit 2 is a full-bridge inverter circuit composed of four switching tubes.

[0043] The power supply of the compensation comparison circuit 6, A / D sampling module, comparison module and WiFi signal transmission module 7 is provided by the pickup coil 5, and the electric energy is supplied to the secondary side through wireless transmission, and no external power supply is required on the knife switch side.

[0044] A method for judging whether the secondary voltage switch of wireless power transmission is closed or opened, such as Figure 3 As shown, the following steps are included:

[0045] Step 1: According to the specific position of the pickup coil and the transmitting coil when the knife switch is in place, establish the fully closed voltage U when the knife switch is closed ref .

[0046] for Figure 4 As shown, under the condition of satisfying equation (1), the secondary side reflection impedance Z M for:

[0047]

[0048] Where R eq is the secondary side equivalent load, R s is the internal resistance of the pickup coil, and M is the mutual inductance between the transmitting coil and the pickup coil.

[0049] System input total impedance Z in for:

[0050]

[0051] Where R f For the compensation coil L f Internal resistance, R s The secondary coil L s Internal resistance.

[0052] Assume that the rectified voltage u0 is:

[0053] u0=E (4)

[0054] Inverter output voltage u AB for:

[0055]

[0056] Inverter output current i f for:

[0057]

[0058] Primary current i p for:

[0059]

[0060] Secondary current i s for:

[0061]

[0062] Equivalent load voltage for:

[0063]

[0064] The actual load terminal voltage effective value U is:

[0065]

[0066] Combining formula (8-10), it can be seen that when the mutual inductance M changes, the actual load terminal voltage u also changes. The value of the mutual inductance M is related to the distance between the primary and secondary coils, thus establishing the fully closed voltage U ref :

[0067] When the knife switch is in the closed position, the primary coil and the secondary coil are vertically opposite and are H meters apart, and the standard mutual inductance threshold M is obtained. H , Substitute into formula (10), and get the detection voltage standard threshold U ref =U RH , place the detection voltage standard threshold in the microcontroller register.

[0068] Step 2: The secondary voltage is sampled in real time, and the microcontroller compares and determines whether the knife switch is closed reliably, and sends the result to the display module.

[0069] The secondary load voltage is sampled in real time through the A / D module, and the sampling result u is sent to the single-sided machine and compared with the stored fully closed voltage U ref For comparison, the comparison rules are as follows:

[0070]

[0071] Among them, U ref Indicates the fully closed voltage, fully closed voltage U ref Refers to the voltage when the secondary voltage of the pickup coil is maximum when the knife switch is closed. If the secondary voltage on the pickup coil (5) is less than the fully closed voltage U ref , it means that the knife switch is not fully closed; if the secondary voltage on the pickup coil (5) is equal to the fully closed voltage U ref , it means the knife switch is fully closed.

[0072] The present invention is based on the mutual inductance coupling principle in wireless power transmission. When the knife switch is open or closed, the pickup coil changes with the position of the knife switch. Since the position of the transmitting coil is fixed, the mutual inductance between the pickup coil and the transmitting coil will change with the position of the knife switch, which will cause the secondary voltage on the pickup coil to change. When the knife switch is closed, the secondary voltage of the pickup coil is the largest, which is defined as the fully closed voltage U ref , the secondary voltages at other locations are all lower than the fully closed voltage.

[0073] Finally, the unilateral machine sends the comparison result to the display module via WiFi as an auxiliary criterion for judging the status of the knife switch, thereby realizing high-precision and low-cost monitoring of the knife switch opening and closing positions.

[0074] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principle of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A system for judging whether the secondary voltage switch is closed or open based on wireless power transmission, characterized in that: It comprises an AC power supply (1), a rectifying and inverting circuit (2), a transmitting coil (4), a picking-up coil (5), an A / D sampling module (7), and a comparing module (8), wherein: The AC power supply (1), the rectifier inverter circuit (2), and the transmitting coil (4) are connected in sequence; the transmitting coil (4) is installed on the low-voltage side of the switch base; the pickup coil (5), the A / D sampling module (7), and the comparison module (8) are connected in sequence, and the pickup coil (5) is installed on the high-voltage side of the switch contact; An AC power source (1) provides power, a rectifier inverter circuit (2) outputs a high-frequency square wave, and the high-frequency square wave power source transmits wireless energy through a transmitting coil (4); The pickup coil (5) receives the electric energy sent by the transmitting coil (4) and generates a secondary voltage; the secondary voltage is converted into a digital signal by an A / D sampling module (7), and enters a comparison module (8) to determine whether the secondary voltage value reaches the fully closed voltage U ref , and obtain the final closing judgment result.

2. According to the system for judging whether the secondary voltage switch of wireless power transmission is in place, the system is characterized in that: The comparison module is provided with the following comparison and discrimination circuit: Among them, U ref Indicates the fully closed voltage, the fully closed voltage U ref Refers to the voltage when the secondary voltage of the pickup coil is maximum when the knife switch is closed.

3. According to claim 2, the system for determining whether the secondary voltage switch of wireless power transmission is in place is characterized in that: The invention comprises an LCCL topology (3), wherein the LCCL topology (3) is arranged between a rectifier inverter circuit (2) and a transmitting coil (4), and the LCCL topology (3) is used to ensure a constant current output of the primary side of the system when the knife switch is in different positions, so as to protect the safety of the system.

4. According to claim 3, the system for judging whether the secondary voltage switch of wireless power transmission is closed or opened is characterized in that: It comprises a capacitance compensation circuit (6), wherein the capacitance compensation circuit (6) is arranged between a pickup coil (5) and an A / D sampling module (7), and the capacitance compensation circuit (6) compensates for the secondary side voltage.

5. The system for determining whether the secondary voltage switch is closed or open based on wireless power transmission according to claim 4 is characterized in that: The invention comprises a wifi signal transmitting module (9), a wifi signal receiving module (10) and a display module (11); the display module (11) is connected to an AC power source (1) and a wifi signal receiving module (10) respectively; the wifi signal receiving module (10) is connected to a transmitting coil (4); the comparison module is connected to the wifi signal transmitting module (9); the wifi signal receiving module (10) is used to receive a closing judgment result signal of a high-voltage side of a knife switch sent by the wifi signal transmitting module (9), and display the result through the display module (11).

6. The system for determining whether the secondary voltage switch is closed or open based on wireless power transmission according to claim 5 is characterized in that: The rectifier inverter circuit (2) is a full-bridge inverter circuit composed of four switch tubes.

7. The system for determining whether the secondary voltage switch is closed or open based on wireless power transmission according to claim 6 is characterized in that: The power supply of the capacitance compensation circuit (6), the A / D sampling module (7), the comparison module (8), and the WiFi signal transmission module (9) is provided by the pickup coil (5).

8. A method for distinguishing whether the secondary voltage switch of wireless power transmission is closed or opened using the system for distinguishing whether the secondary voltage switch of wireless power transmission is closed or opened based on claim 1, characterized in that: The change of mutual inductance between the pickup coil and the transmitting coil during the opening and closing process of the knife switch will cause the change of the secondary voltage. Therefore, the opening and closing state of the knife switch is judged by detecting the secondary voltage. Based on the principle of wireless power transmission, the electric energy is transmitted by the transmitting coil and received by the pickup coil. The secondary voltage of the pickup coil is compared after A / D sampling; when the secondary voltage reaches the fully closed voltage U ref Indicates that the knife switch is fully closed; the secondary voltage has not reached the fully closed voltage U ref Indicates that the knife switch is open.

9. The identification method according to claim 8, characterized in that: The discriminant formula is as follows: Among them, U ref Indicates fully closed voltage.

10. The system for determining whether the secondary voltage switch is closed or open based on wireless power transmission according to claim 9, characterized in that: Fully closed voltage U ref Refers to the voltage when the secondary voltage of the pickup coil is maximum when the knife switch is closed.

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